JPH03250437A - Optical information recording/reproducing device and double diffraction grating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical information recording and reproducing device that records information using an optical information recording medium and also performs tracking servo and focus servo, and a double diffraction grating. .

BACKGROUND OF THE INVENTION Conventionally, the first conventional example of an optical information recording/reproducing apparatus using a diffraction grating as a beam separating means is the one disclosed in Japanese Patent Application Laid-Open No. 61-230634. be. That is, as shown in FIG. 36, the laser beam emitted from the semiconductor laser 1 is collimated by the collimating lens 2 and enters the polarizing beam splitter 3.

In this case, since the polarization direction of the incident light is parallel to the groove of the polarizing beam splitter 3,
The light is diffracted and enters the quarter-wave plate 4 to become a circularly polarized light wave, which is focused by the objective lens 5 and irradiated onto an optical disc 6 as an optical information recording medium, thereby recording information. Further, the reflected light from the optical disk 6 is converted into a linearly polarized light wave by the quarter-wave plate 4, which passes through the polarization beam splitter 3, is guided to the signal detection optical system 7, and is incident on the critical angle diffraction grating 8. do. In this case, the incident light undergoes critical angle diffraction and total reflection twice, becomes diffracted light, and enters the four-divided light-receiving element 9, and is detected by the four-divided light-receiving element 9, thereby providing information. , and detection of focus error signals and track error signals.

Next, as a second conventional example, there is one using a dual type diffraction grating 10, as shown in FIG. That is,
The light emitted from the semiconductor laser 11 is passed through the collimating lens 1.
2, the light is reflected by a beam splitter 14 through two shaping prisms 13, focused by an objective lens 15, and irradiated onto a magneto-optical disk 16, thereby recording information. Further, the reflected light from the magneto-optical disk 16 is transmitted to the beam splitter 1.
4, is guided to the signal detection optical system 17, is focused by a condenser lens 18, and is transmitted or diffracted through the diffraction gratings 10a formed on both sides of the dual type diffraction grating 10. Of these, the O-order light T that has passed through and gone straight is guided to the four-split light receiving element 19a, while the first-order light that has been diffracted is guided to the two-split light receiving element 19b. As a result, the magneto-optical signal, which becomes the reproduction signal, is detected by the difference in light intensity between the O-order light T and the first-order light, and the focus error signal is detected using the O-order light T by the astigmatism method, and the focus error signal is detected using the O-order light T by the astigmatism method. The error signal is detected using the primary light K by the bush-pull method or the like.

Next, a third conventional example will be explained. Light emitted from a semiconductor laser as a laser light source is collimated by a collimating lens, then reflected by an optical path separation means, and condensed by an objective lens to form a magneto-optical disk as an optical information recording medium. The surface is irradiated, thereby recording information. In addition, the reflected light from the magneto-optical disk passes through the optical path separation means, is guided into the signal detection optical system, and is detected by the light receiving element, thereby reproducing information and detecting focus error signals and track error signals. It is carried out.

A fourth conventional example will be explained based on FIG. 38.

The light emitted from the semiconductor laser 20 passes through the beam splitting element 21
After being reflected by the diffraction grating 22 formed on one surface and collimated by the collimating lens 23, the objective lens 2
4 and irradiates the surface of the magneto-optical disk 25, thereby recording information. In addition, the reflected light from the magneto-optical disk 25 passes through the objective lens 24 and the collimating lens 23 sequentially, and then passes through the diffraction grating 22 of the beam splitting element 21 to be separated into O-order light T and first-order light. After being reflected by a total reflection surface 26 formed on the back surface, the light passes through the diffraction grating 22 again and is emitted to the outside. As a result, the O-order light T and the first-order light have different optical path lengths, and are guided to two light-receiving elements 27 arranged in the same plane as the semiconductor laser 20, thereby detecting various signals. It can be performed.

Problems to be Solved by the Invention First, the first problem will be described. In the case of the first conventional example shown in FIG. 36, it is possible to apply a write-once optical disk or CD to the optical information recording medium, but since it does not have a detection function for magneto-optical signals, it is not possible to use a rewritable optical It cannot be used as a disk head.

Next, we will discuss the second problem. In the case of the second conventional example shown in Fig. 37, a dual-type diffraction grating is used, and the output directions of the ○th-order light T and the first-order light formed by passing through the grating are directed in almost the same direction. Is it possible to save some space in the signal detection optical system 17?However, when looking at the device as a whole,
There is a problem in that optical components such as the beam splitter 14 and the condensing lens 18 remain, making it impossible to achieve sufficient size and weight reduction.

Next, I will discuss the third problem. In the case of the third conventional example, an optical path separation means is used to separate the light fluxes of the light emitted from the laser light source and the light reflected from the magneto-optical disk. As this beam separating means, a prism such as a beam splitter is generally used. However, in recent years, in order to shorten access time, it has become important to reduce the size and weight of optical pickup optical systems. One means to solve this problem is to use a dual diffraction grating, in which diffraction gratings are formed on both the front and back surfaces, as the aforementioned light beam separation means. By using this dual diffraction grating, it is possible to reduce the number of parts and the space required for the entire optical pickup optical system, thereby increasing the speed of seek movement.

However, due to its nature, the diffraction grating formed in such a dual-type diffraction grating is susceptible to wavelength fluctuations.
Moreover, the surface on which the diffraction grating is formed is fragile and the grating shape is easily distorted. Therefore, when such a diffraction grating is used, the accuracy of reflected, transmitted, and diffracted wavefronts deteriorates and the focused spot becomes larger, resulting in the problem that accurate information recording and reproduction cannot be performed. occurs.

Next, I will discuss the fourth problem. In the case of the second conventional example shown in FIG. 37, the layout of the entire optical system is as follows.
Since the optical system is divided into the output optical system A and the signal detection optical system B, the number of parts increases as a whole, resulting in an increase in cost.

Next, I will discuss the fifth problem. In the case of a fourth conventional example as shown in FIG.
As in the case of two diffraction gratings, the variation in the diffraction angle becomes smaller with respect to the variation in wavelength. but,
Light irradiated onto the magneto-optical disk 25 and the magneto-optical disk 2
The substrate 28 of the optical path separation element 21 separates the reflected light from the
Since this is determined by the plate thickness, there is a problem in that the degree of freedom in designing the distance between the light-emitting point and the light-receiving point and the focus sensitivity is narrowed, and furthermore, adjustment, assembly, and manufacturing become difficult. Further, in this case, there is a problem that the light utilization efficiency decreases due to reflection on the surface of the diffraction grating 22.

Next, I will discuss the sixth problem. In the case of a fourth conventional example as shown in FIG. 38, the diffraction grating 22 and the total reflection surface 26
By disposing the beam splitting element 21 having the above, the number of parts of the optical system can be reduced, and space can be saved. However, in this case, the transmitted light T and the diffracted light K
Two light-receiving elements 27 for detecting are mounted on one substrate so as to be disposed on both sides of the semiconductor laser 20. Therefore, during mounting, it is extremely difficult to position the two light receiving elements 27 and the semiconductor laser 20, that is, to perform fine adjustment. Also, in this case,
Since the semiconductor laser 20 and the light receiving element 27 are located at different distances from the mounting board 29, a separate height adjustment device is required. Since the light receiving elements 27 are arranged on both sides of the semiconductor laser 20 in this manner, there is a problem in that the adjustment is troublesome and time consuming for assembling the light receiving elements 27.

Means for Solving the Problems In the invention according to claim 1, light emitted from a laser light source is collimated by a collimating lens, and the collimated light is focused by an objective lens and irradiated onto an optical information recording medium. In an optical information recording and reproducing apparatus that records information and detects a reproduction signal for information, a track error signal, and a focus error signal by detecting reflected light from the optical information recording medium, emitted from the laser light source. A first diffraction member having a semi-reflective film is provided on the optical path on which the emitted light goes to the objective lens, and a second diffraction member is provided on the optical path on which the reflected light from the optical information recording medium passes through the first diffraction member. A diffraction member was provided, and a light receiving element was provided to detect transmitted light and diffracted light that were separated by passing through the second diffraction member.

In the invention according to claim 2, the light emitted from the laser light source is collimated by a collimating lens, the collimated light is focused by an objective lens, and is irradiated onto an optical information recording medium to record information, In an optical information recording and reproducing device that reproduces information and detects track error signals and focus error signals by guiding reflected light from the optical information recording medium to a light receiving element, a light path side of the light emitted from the laser light source is used. A surface diffraction grating having a semi-reflective film that reflects a part of the light incident on the surface is formed, and a light beam separation means having a back diffraction grating is provided on the surface opposite to this surface, and the back diffraction grating The light receiving element was disposed on the optical path on the side where the light receiving element was formed.

In the invention according to claim 3, the light emitted from the laser light source is collimated by a collimating lens, and the collimated light is focused by an objective lens and irradiated onto an optical information recording medium to record information. In an optical information recording and reproducing apparatus that reproduces information and detects track error signals and focus error signals by guiding reflected light from the optical information recording medium to a light receiving element, the optical path of the light emitted from the laser light source is A diffraction grating having a semi-reflective film that reflects a part of the light incident on the surface located on the side is formed, and a light beam separation means is provided on the surface opposite to the second surface with a total reflection surface formed, and the laser The light receiving element was arranged on the optical path on the side where the light source was provided.

In the invention according to claim 4, the light emitted from the laser light source is collimated by a collimating lens, the collimated light is focused by an objective lens, and is irradiated onto an optical information recording medium, thereby recording information. In an optical information recording and reproducing apparatus that reproduces information and detects focus error signals and track error signals by guiding reflected light from an optical information recording medium to a light receiving element in a signal detection optical system, the light emitted from the laser light source is used. A semi-reflective first substrate having a first diffraction member formed on one side thereof and a surface of the first substrate on which the first diffraction member is formed are arranged opposite to each other on the optical path of the light with a spacer interposed therebetween. A double diffraction grating element serving as a transparent second substrate on which a second diffraction member was formed was disposed on the other side.

In the invention as set forth in claim 5, the light emitted from the laser light source is collimated by a collimating lens, and then focused by an objective lens and irradiated onto an optical information recording medium to record information, and the optical information is In an optical information recording and reproducing device that detects reflected light from a recording medium to reproduce information and detect a track error signal and a focus error signal, a wedge shape is provided on the optical path between the collimating lens and the objective lens. A light beam separating means is disposed in which a diffraction grating having a semi-reflective film is formed on one surface of the non-parallel substrate and a total reflection surface is formed on the other surface, and the light reflected by the light beam separating means is transmitted through the collimating lens. Two light receiving elements for detecting reflected light from the optical information recording medium were installed on the optical path on the laser light source side.

In the invention as set forth in claim 6, information is recorded by collimating the light emitted from the laser light source by a collimating lens, and then condensing the light by an objective lens and irradiating it onto an optical information recording medium. In an optical information recording and reproducing device that detects reflected light from a medium to reproduce information and detect track error signals and focus error signals, a non-parallel substrate is provided on the optical path between the collimating lens and the objective lens. A light beam separating means is provided in which a diffraction grating having a semi-reflective film is formed on one surface and a total reflection surface in the shape of a wedge prism is formed on the other surface, and the light reflected by the light beam separating means is transmitted through the collimating lens. Two sets of two light receiving elements for detecting reflected light from the optical information recording medium were disposed on the optical path on the laser light source side.

In the invention according to claim 7, information is recorded by condensing light emitted from a laser light source with an objective lens and irradiating it onto an optical information recording medium, and the reflected light from the optical information recording medium is detected. In an optical information recording and reproducing device that reproduces information and detects track error signals and focus error signals, a diffraction grating is provided on one surface of the substrate on the optical path of the light emitted from the laser light source toward the objective lens. A light beam separating means is provided, in which a semi-reflecting film is formed on one part of the surface and a total reflecting surface is formed on the other surface, and a first light beam is disposed on the optical path of the primary light that is diffracted by the light beam separating means and proceeds. A second light receiving element was arranged on the optical path of the zero-order light that was refracted by the light beam separating means and proceeded.

In the invention set forth in claim 8, in the structure of the invention set forth in claim 7 described above, a collimating lens is disposed on the optical path of the light emitted from the laser light source as it heads toward the beam separation means.

In the invention described in claim 9, information is recorded by condensing the light emitted from the laser light source by an objective lens through a collimating lens and irradiating the light onto an optical information recording medium, and the information is recorded on the optical information recording medium. In an optical information recording and reproducing device that detects reflected light from a camera to reproduce information, detect a drag nir signal, and a focus error signal, the emitted light passes through the collimating lens and heads toward the objective lens. A wedge-shaped light beam separating means is disposed on the optical path, and includes a diffraction grating formed on one surface of the substrate, a semi-reflective film on the surface thereof, and a total reflective surface on the other surface, and the emitted light is directed to the semi-reflective film. The light beam separating means is wedge-shaped so that the main beam of the book and the two sub-beams obtained by passing through the semi-reflective film are guided to the optical information recording medium. The wedge angle was set.

In the invention according to claim 10, in the configuration of the invention according to claim 9 described above, of the main beam and the sub beam reflected by the optical information recording medium, two beams that receive the main beam are provided.
Two three-split light receiving elements are provided to receive the sub beam.
Two undivided light receiving elements were provided.

In the invention described in claim 11, the light emitted from the laser light source is collimated by a collimating lens, and then focused by an objective lens and irradiated onto the surface of an optical information recording medium to record information, and the optical information is In an optical information recording and reproducing device that detects a focus error signal and a track error signal by detecting reflected light from a recording medium using a light receiving element,
On the optical path of the light emitted from the laser light source toward the collimating lens, there is provided a beam separating means having a transmission type diffraction grating and a high reflection surface disposed at a certain angle to the transmission type diffraction grating. Established.

In the invention as set forth in claim 12, a semi-reflective first substrate having a first diffraction member formed on one side thereof and a surface of the first substrate on which the first diffraction member is formed are arranged to face each other via a spacer. A double diffraction grating consisting of a transparent second substrate on which a first diffraction member was formed was provided on the opposite side.

According to the invention described in claim 1, the light emitted from the laser light source is reflected by the semi-reflective film formed on the first diffraction member, and then reflected by the optical information recording medium and guided to the first diffraction member again. The transmitted light and the diffracted light are separated by passing through the second diffraction member, and these two separated lights are detected by the light receiving element to reproduce information, track error signals, and focus error signals. can be detected.

According to the second aspect of the invention, the light emitted from the laser light source is reflected by the semi-reflective film formed on the surface diffraction grating of the beam separation means, and then reflected by the optical information recording medium and guided to the surface diffraction grating again. Furthermore, by passing through the back surface diffraction grating, the 0th-order light and the 1st-order light are separated into a 0th-order light and a 1st-order light that are emitted in almost the same direction, and these two separated lights are detected by a light receiving element. By doing so, information can be reproduced and track error signals and focus error signals can be detected.

According to the third aspect of the invention, the light emitted from the laser light source is reflected by the semi-reflective film formed on the surface diffraction grating of the beam separating means, and then reflected by the optical information recording medium and guided to the surface diffraction grating again. The light is then reflected by the total reflection surface, passes through the surface diffraction grating again, and is detected by a light receiving element placed in the same plane as the laser light source, thereby reproducing information, tracking error signals, and focus error signals. can be detected.

According to the invention described in claim 4, the light emitted from the laser light source is reflected by the semi-reflective first substrate of the double diffraction grating element, collimated by the collimating lens, and reflected by the optical information recording medium. , is again guided to the double diffraction grating element, and is separated into two lights, the transmitted light and the diffracted light, by the first diffraction member of the first substrate, and after both pass through the spacer, the transmitted light is guided to the second substrate. The diffracted light that passes through the second diffraction grating as it is is further diffracted by the second diffraction grating, passes through the double diffraction grating in a separated state, and is guided into the signal detection optical system to reproduce information. , focus error signal, and track error signal can be detected.

According to the invention as set forth in claim 5, the diffraction grating and the total reflection surface are formed on both sides of a non-parallel substrate.
Since the secondary light and the primary light are spot-separated, it is easy to design the layout of the entire optical system.Moreover, the light beam separation means is disposed between the collimator lens and the objective lens, so it is not collimated. The resulting light enters the diffraction grating, which enables high-performance polarization separation and increases light utilization efficiency.

According to the invention as set forth in claim 6, the total reflection surface is shaped like a wedge prism, and two sets of two light receiving elements are arranged, thereby making it possible to detect a focus error signal using the double knife method. As a result, the accuracy of assembly can be made much looser than in the past, and stable signal detection can be performed at all times.

According to the invention set forth in claim 7, the light emitted from the laser light source is reflected by the semi-reflective film of the beam separation means and guided to the optical information recording medium, thereby recording information, and at the same time recording information from the optical information recording medium. The reflected light passes through the semi-reflective film of the beam separation means and is separated into 0th-order light and 1st-order light, and these 0th-order light and 1st-order light pass through the diffraction grating in the area other than the semi-reflective film. It is possible to reproduce information and detect signals by emitting the light to the outside and guiding it to the first and second light receiving elements, respectively. This allows the 0th-order light and the 1st-order light to be separated by the diffraction grating of the beam separation means. When the light is reflected by the total reflection surface and emitted to the outside, it passes through a transmission area other than the semi-reflection film in the diffraction grating, so it is possible to further improve the light utilization efficiency compared to the conventional method.

According to the invention as set forth in claim 8, the light emitted from the laser light source is guided to the beam separation means after passing through the collimator lens, so that only the parallel light of the emitted light enters the diffraction grating, resulting in high performance. Can perform polarization separation,
This makes it possible to further increase the light utilization efficiency.

According to the invention as set forth in claim 9, among the light whose emitted light is incident on the semi-reflective film formed on the surface of the diffraction grating of the beam separation means, the reflected light by the semi-reflective film is used as a main beam, and the transmitted light is used as a sub beam. This makes it possible to perform three-beam tracking, and this makes it possible to make this device compatible with various devices that use magneto-optical disks, CDs, etc. as optical information recording media, expanding the range of its applications compared to conventional methods. It can be expanded further.

According to the tenth aspect of the invention, the main beam and the sub beam reflected by the optical information recording medium are all received by each light receiving element without wastage, so that the light utilization efficiency can be further improved compared to the conventional method.

According to the invention as set forth in claim 11, by providing the light beam separating means having a transmission type diffraction grating and a high reflection surface disposed at a certain angle to the transmission type diffraction grating, the transmitted light separated by the light beam separating means and Since the optical path of the reflected light can be changed, it is no longer necessary to provide a light receiving element on both sides of the laser light source as in the past, and as a result, the substrate for the laser light source and the substrate for the light receiving element can be created separately. Since it can be mounted as a single unit, assembly and adjustment can be simplified compared to conventional methods, and work efficiency can be increased.

According to the twelfth aspect of the invention, the first diffraction member and the second diffraction grating are configured to face each other, so that the diffraction grating surface is sealed inward, thereby stabilizing the grating shape and making two diffraction Because the grids are close together,
It is possible to make the primary light less susceptible to shift fluctuations due to wavelength fluctuations.

Embodiment An embodiment of the invention described in claim 1.2 is shown in FIGS. 1 to 5.
This will be explained based on the diagram. Note that this embodiment deals with the first problem and the second problem.

A dual-type diffraction grating 31 as a beam separating means is disposed on the optical path of the light emitted from the semiconductor laser 30 as a laser light source. This dual type diffraction grating 31
A surface diffraction grating 33 as a first diffraction member having a semi-reflective film 32 on its surface portion that reflects a part of the light incident on the surface located on the semiconductor laser 30 side is formed. A back diffraction grating 34 as a second diffraction member is formed on the surface facing the grating 33. The diffraction efficiency of the diffraction gratings 33 and 34 formed on both the front and back surfaces changes depending on the polarization direction. Further, on the optical path on the side where the surface diffraction grating 33 is formed,
A collimating lens 35, an objective lens 36, and a magneto-optical disk 37 as an optical information recording medium are arranged in this order.

Further, on the optical path on the side where the back surface diffraction grating 34 is formed, a light receiving element 38 for detecting a focus error signal, a tracking error signal, etc. is arranged. In such a configuration, the light emitted from the semiconductor laser 30 is
It is reflected by the semi-reflective film 32 on the surface diffraction grating 33.

This semi-reflective film 32 is designed to irradiate the magneto-optical disk 37 with desired optical power. The reflected light becomes parallel light by the collimating lens 35. Since this parallel light is simply reflected light and not diffracted light by the surface diffraction grating 33, no aberration occurs, and therefore the shape of the surface diffraction grating 33 does not need to be particularly curved or have a modulation pitch. The parallel light is focused by an objective lens 36 and irradiated onto the surface of the magneto-optical disk 37 in the form of a spot. Then, due to the Kerr effect, the irradiated light is reflected with the polarization direction tilted according to the information signal on the magneto-optical disk 37, returns to the collimating lens 35 again, and is converged by the collimating lens 35. The light becomes incident on the surface diffraction grating 33. In this case, dual type diffraction grating 3
1 is arranged so that the diffraction gratings 33 and 34 formed on both the front and back surfaces thereof form a black angle with respect to the reflected light from the magneto-optical disk 37.

That is, as shown in FIG. 5, the diffraction gratings 33 and 34 formed on both the front and back surfaces are oriented at 45 degrees with respect to the polarization direction of the light from the semiconductor L-hoop 30. The light incident on the front surface diffraction grating 33 is separated into transmitted light T and diffracted light K, and then enters the back surface diffraction grating 34. This back diffraction grating 34 is a transmission type diffraction grating, and its grating direction is the same as that of the front diffraction grating 33. That is, the transmitted light (0th order light) of the front surface diffraction grating 33 also passes through the back surface diffraction grating 34 and becomes 0th order light, and the diffracted light (1st order light) of the front surface diffraction grating 33 is also diffracted by the back surface diffraction grating 34 and becomes 1 It becomes the next light. In this way, O order light T and 1
The light separated into two lights, the second order light, is received by the light receiving element 38, and an optical information signal, a focus error signal, Track error signals can be detected.

In this case, the focus error signal can be detected using the astigmatism method using a parallel plate using O-order light T, as shown in FIG. As shown in FIG. 4(b), the astigmatism method uses one-dimensional K by modulating the front diffraction grating 33 and the back diffraction grating 34,
Thirdly, as shown in FIG. 4(c), there is a beam size method that utilizes the optical path difference existing between the O-order light T and the first-order light. In addition, as a method of detecting the track error signal, when the bush-pull method is used, the detection is performed using the light receiving element 38 which is divided into two parts, and when the sample servo method is used, the reflected light intensity is detected by being received by the light receiving element 38. be able to.

As mentioned above, the dual-type diffraction grating 31 is designed to divide the light into two parts.
By making the light pass twice, it is possible to reduce the positional deviation of the spot due to wavelength fluctuations, and by forming a semi-reflective film 32 on one surface of one surface diffraction grating 33, it is possible to By simply providing the dual-type diffraction grating 31, it is possible to separate the light flux between the output optical system and the signal detection optical system, and this allows the number of optical components to be significantly reduced, making the overall device configuration more compact. , it is possible to reduce the weight and cost.

Next, an embodiment of the invention according to claims 1 and 3 will be described based on FIG. Note that this embodiment deals with the first problem and the second problem. Further, the same reference numerals are used for the same parts as in the invention described in claim 2.

In the single-sided diffraction grating 39 as a beam separating means, a diffraction grating 40 as a first diffraction member whose diffraction efficiency changes depending on the polarization direction is formed on the surface located on the semiconductor laser 30 side. A total reflection surface 41 as a second diffraction member is formed on the opposing surface. A semi-reflective film 42 is formed on the diffraction grating 40 and has a constant reflectance so that the magneto-optical disk 37 is irradiated with a desired optical power. Further, the light receiving element 38 is configured to be integrated with the semiconductor laser 30 on the side where the diffraction grating 40 is formed. Note that the single-sided diffraction grating 39 is attached to the magneto-optical disk 37.
It is arranged so that it forms a black angle with respect to the reflected light from.

In such a configuration, the light emitted from the semiconductor laser 30 is reflected by the semi-reflective film 42 on the diffraction grating 40, becomes parallel light by the collimator lens 35, and is focused by the objective lens 36 onto the surface of the magneto-optical disk 37. The information signal is read. Then, the reflected light from the magneto-optical disk 37 returns to the diffraction grating 40 again, and the incident light is separated into O-order light T and first-order light, and is reflected by a total reflection surface 41 formed on the back surface. After being reflected,
The light passes through the diffraction grating 40 again and is detected by the light receiving element 38 integrated with the semiconductor laser 30, thereby reproducing the information signal and detecting the focus error signal and the track error signal. Note that the method for detecting these signals has been described in the above-described second aspect of the invention, so a description thereof will be omitted here.

Therefore, by forming the diffraction grating 40 on only one side as in this embodiment, it becomes easier to manufacture and handle the diffraction grating 40, and the total reflection surface 41 formed on the back side allows light to be emitted. Since it is returned to the optical system, the semiconductor laser 30 and the light-receiving element 38 can be integrated, thereby reducing the number of parts and making it possible to obtain a device that is even more compact.

Next, a first embodiment of the invention recited in claims 1, 4, and 12 will be described based on FIGS. 7 and 8.

Note that this embodiment deals with the third problem.

A dual-type diffraction grating 44 as a double diffraction grating element is formed on the optical path of the light emitted from the semiconductor laser 43 as a laser light source. As shown in FIG. 8, this dual type diffraction grating 44 includes a semi-reflective first substrate 45 on which a first diffraction grating 45a as a first diffraction member is formed on one side, and First diffraction grating 45a
A second diffraction grating 47a serving as a second diffraction member is disposed on the surface on which the is formed and the surface on the side opposite to each other with the spacer 46 interposed therebetween.
A transparent second substrate 47 is formed thereon.

Further, the first substrate 45 of the dual type diffraction grating 44
A collimating lens 48 and an objective lens 49 are sequentially disposed on the side, and a magneto-optical disk 50 as an optical information recording medium is disposed opposite the objective lens 49. Furthermore, the dual type diffraction grating 44
In the signal detecting optical system 5 located on the second substrate 47 side, a four-divided light receiving element 52a and a two-divided light receiving element 52b as light receiving elements are disposed.

In the dual-type diffraction grating 44, a surface 4.5b of the first substrate 45 located on the incident light side where the first diffraction grating 45a is not formed is a highly accurate semi-reflective polished surface. The second diffraction grating 4 of the second substrate 47 is finished so that the reflected wavefront is not disturbed.
The surface 47b on the outgoing light side where 7a is not formed is configured to prevent diffused reflection with a non-reflection coating or the like.

In such a configuration, the diverging light A emitted from the semiconductor laser 43 is reflected by the surface of the semi-reflective first substrate 45 of the dual type diffraction grating 44 and collimated by the collimating lens 48, and then further The parallel light is focused by the objective lens 49 and irradiated onto the surface of the magneto-optical disk 50, thereby recording information. Also,
The reflected light from the magneto-optical disk 50 is reflected by the objective lens 4
9. The light is guided to the dual-type diffraction grating 44 again through the collimating lens 48. This dual type diffraction grating 4
As shown in FIG.
The light is separated into T and diffracted light (first-order light) K (point P). Then, the O-order light T passes through the spacer 46 and passes through the second substrate 4.
On the other hand, the primary light passes through the spacer 46 and is further diffracted by the second diffraction grating 47a formed on the second substrate 47 (point Q). <(R point)

After that, of the O-order light T and the first-order light guided into the signal detection optical system 51 in this way, the O-order light T is astigmatic because the substrate of the dual type diffraction grating 44 is relatively thick. This creates a state where aberrations are generated, and as a result, a refocus error signal can be detected by the astigmatism method using the four-split light receiving element 52a.

In addition, the ]-order light T also has astigmatism, but in this case, the astigmatism is canceled by the action of the diffraction grating, and a tracking error is generated using the bush-pull method using the two-split light-receiving element 52b. signal can be detected. Furthermore, a first diffraction grating 45a with a fine pitch
The magneto-optical signal can be detected by comparing the intensities of the two light fluxes respectively detected by the four-split light receiving element 52a and the two-split light receiving element 52b due to the polarization separation characteristic of the second diffraction grating 47a.

As described above, the dual type diffraction grating 44 has a semi-reflective surface 45b and two diffraction gratings 45a and 47a inside.
Since astigmatism is generated in only one of the O-order light T and the first-order light using
Since the two diffraction gratings are arranged close to each other, they are less susceptible to shifts in the primary light due to wavelength fluctuations, and as a result, stable and highly reliable signal detection can be performed at all times. Furthermore, by making one surface of the dual-type diffraction grating 44 a semi-reflective surface 45b, it is possible to have a highly accurate beam splitter function.
As a result, the number of parts in the optical system can be reduced to make the optical system smaller and lighter, and high-speed seek movement is possible, thereby further shortening the access time.

Next, a second embodiment of the invention recited in claims 1 and 4.12 will be described based on FIG. 9. Note that this embodiment also addresses the third problem.

Here, a semiconductor laser 43 and a dual-type diffraction grating 4 are used.
A collimating lens 48 is disposed on the optical path between the
Further, a condenser lens 53 is disposed on the second substrate 47 side of the dual type diffraction grating 44. As a result, the light emitted from the semiconductor laser 43 is collimated by the collimating lens 48 and then sent to the dual-type diffraction grating 4.
4), and the magneto-optical disk 50
The reflected light from the dual-type diffraction grating 4 is also in the state of parallel light flux.
It will be incident on 4. Therefore, among the lights that have passed through the dual-type diffraction grating 44, the O-order light T does not generate astigmatism, so a tracking error signal can be detected using the two-split light-receiving element 52b. Since the diffraction grating can provide astigmatism, the focus error signal can be detected using the four-segment light receiving element 52a. Note that the magneto-optical signal can be detected in the same manner as described above.

Next, a third embodiment of the invention recited in claims 1, 4, and 12 will be described based on FIG. Note that this embodiment also addresses the third problem.

Here, a cylindrical lens 54 is disposed between the dual type diffraction grating 44 and the condensing lens 53 in the second embodiment (see FIG. 9). This results in
As shown in FIG. 11(a) when viewed from a direction parallel to the plane of the paper, the dual-type diffraction grating 44 condenses the primary light K in the direction of the plane of the paper, and the condensing point B and the focal point of the concave cylindrical lens 54 When they match, the cylindrical lens 54
The primary light that passes through has no astigmatism. In addition, the first
FIG. 1(b) shows the signal detection optical system 51 when viewed from a direction perpendicular to the plane of the paper. Therefore, a tracking error signal can be detected by having the two-split light receiving element 52b detect the first-order light K that does not have astigmatism, and the zero-order light K has astigmatism removed by the cylindrical lens 54. Therefore, the focus error signal can be detected using the four-division light receiving element 52a.

Next, a first embodiment of the invention according to claims 1, 5, and 6 will be described based on FIGS. 12 to 14. Note that this embodiment deals with the fourth problem and the fifth problem.

First, the overall configuration of this device will be described based on FIG. 12.

A prism 58 as a beam separating means, which is made of a wedge-shaped non-parallel substrate 57, is disposed on the optical path of the light emitted from the semiconductor laser 55 as a laser light source and transmitted through the collimating lens 56. The non-parallel substrate 5
A diffraction grating 59 as a first diffraction member with a modulated pitch as shown in FIG. 13 is formed on one surface of the grating 7.
A total reflection surface 60 as a second diffraction member is formed on the other surface. A coating layer 59a serving as a semi-reflective film is formed on the surface of the diffraction grating 59. Note that if the angles formed by the diffraction grating 59 and the total reflection surface 60 with respect to the plane are respectively 0 and β, β-α can be expressed as a wedge angle.

Further, an objective lens 61 is disposed on the side of the prism 58 on which the diffraction grating 59 is formed. A magneto-optical disk 62 as an optical information recording medium is provided at a position close to the objective lens 6e. On the other hand, on the optical path on the optical system 63 side where the semiconductor laser 55 is provided, two light receiving elements 64 and 65 for detecting the reflected light from the magneto-optical disk 62 are arranged in the same plane.

In such a configuration, the light emitted from the semiconductor laser 55 becomes parallel light by the collimating lens 56,
The light is guided to a diffraction grating 59 whose diffraction efficiency changes depending on the polarization direction of the prism 58.

A coating layer 59a is formed on the diffraction grating 59 so as to have polarization dependence as shown in FIG. 14 and a desired reflectance in order to irradiate the magneto-optical disk 62 with appropriate optical power. However, this coating layer 59
A part of the parallel light from the collimator lens 56 is reflected by a, and the parallel light travels toward the objective lens 61. On the other hand, the parallel light that is transmitted without being reflected is separated into zero-order light T and first-order light by the diffraction grating 59, and travels toward the total reflection surface 60. Since this total reflection surface 60 is not parallel to the diffraction grating 59 but has a wedge shape, the light reflected here is not parallel to the light reflected by the coating layer 59a, but travels in a different direction and is separated. Since the light is illuminated, there will be no negative effects. Thereafter, the reflected light from the coating layer 59a that has traveled to the objective lens 61 is irradiated onto the surface of the magneto-optical disk 62, thereby making it possible to record information.

Further, the reflected light from the magneto-optical disk 62 reads the recorded information signal, has its polarization direction rotated due to the Kerr effect, and is guided to the diffraction grating 59 again. The reflected light is separated into O-order light T and first-order light by this diffraction grating 59, reflected by a total reflection surface 60 on the back surface, passes through the diffraction grating 59 again, and is emitted to the outside.

At this time, the O-order light T and the first-order light are set at different angles from the diffraction grating 55 than the parallel light emitted from the semiconductor laser 55.
It is emitted from 9.

Then, the O-order light T and the first-order light pass through the collimating lens 56 and are detected by the light receiving elements 64 and 65.

In this case, since the primary light passes through the diffraction grating 59 twice, the deviation in the diffraction angle due to wavelength fluctuation can be almost canceled out. Furthermore, since the diffraction grating 59 has a modulation pitch, it can generate astigmatism in the primary light K.
Thereby, by guiding the primary light K to one of the light receiving elements 65, a focus error signal can be detected. On the other hand, since astigmatism does not occur in the O-order light T, by guiding this light to one of the light receiving elements 64, a stable tracking error signal can be detected using the bush-pull method. Furthermore, those two light receiving elements 64.
The magneto-optical signal is detected by determining the intensity difference between the signals detected by the magneto-optical signal 65, and information can be reproduced thereby.

As mentioned above, by shifting the polarization direction of the light emitted from the semiconductor laser 55 by 45 degrees from the grating direction of the diffraction grating 59, the λ/2 plate that was conventionally required can be omitted. This allows the number of parts to be reduced. Also, depending on the wedge angle of the prism 58, the O-order light T and the
The spot spacing between the next light and the next light can be set arbitrarily,
Moreover, since the focus sensitivity is determined by the degree of modulation pitch, this increases the degree of freedom in design, making it possible to optimally design each component, making it possible to realize a compact and highly sensitive magneto-optical head.

Next, a second embodiment of the invention described in claims 1 and 5.6 will be described based on FIGS. 15 to 17. Note that this embodiment deals with the fourth problem and the fifth problem. This is the same as the first embodiment described above, except that the arrangement positions of the light receiving elements 64 and 65 are changed, and there is no change in the other configurations.

FIG. 16 shows the light receiving elements 64 and 65 connected to the collimating lens 5.
It is seen from the 6th side, and each has a shape divided into 3 parts. In addition, in this case, the light receiving elements 64 and 65 are
They are arranged so as to be shifted back and forth in the optical axis direction. Therefore, the focus error signal here is detected not by the astigmatism method but by the beam size method.

By detecting signals using this method,
Since a large tolerance for assembly and position adjustment can be achieved, assembly can be easily adjusted and mass production of the -layer can be achieved. Further, in the case of this embodiment, since astigmatism is not required, the pitches of the gratings 59 can be formed at equal pitches, so that the production of the gratings 590 can be made easier.

Next, a third embodiment of the invention described in claims 1, 5, and 6 will be described based on FIGS. 18 and 19.

Note that this embodiment also addresses the fourth problem and the fifth problem.

This is a modification of the first embodiment (see FIG. 12) in which the shape of the beam separating means is changed. That is, the prism 58 as a beam separating means has its non-parallel substrate 57.
A grating 59 for polarization separation is formed on one surface, and a total reflection surface 6o is formed on the other surface, but in this embodiment, the shape of the total reflection surface 60 is not a plane, but an 18th
As shown in the figure, it is formed into a wedge prism shape.

Therefore, if the layout of the entire optical system is the same as that shown in FIG. 12, the light-receiving optical system viewed from the collimator lens 56 side will be divided into two light-receiving elements 66, 67, 67, 66, 67, 66, 67, 66, 67, 66, 67, 66, 66, 67, 66, 67, 66, 67, 66, 67, 66, 67, 66, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67 respectively are each that separate the light receiving optical system, as shown in FIG.
It is constructed using a total of four pieces of 68.69. That is, in this case, the focus error signal FO is detected by the double knife method using two spots formed by the 0th order light T or the 1st order light K, and the other two spots (or only one) are detected. The tracking error signal Tr is detected using the bush-pull method. Furthermore, the magneto-optical signal Mo can be detected by the difference in light intensity between the 0th-order light T and the 1st-order light. Therefore, by performing signal detection using such a method, the two-split light receiving elements 66, 67, 68, and 69 are all disposed in the same plane, so they can be formed integrally. Detecting a focus error signal using the Tsuji method has an advantage over the astigmatism method in that the influence of wavelength fluctuations can be reduced.

Next, an embodiment of the invention described in claims 1 and 7.8 will be described in the 20th embodiment.
This will be explained based on FIGS. 22 to 22.

Note that this embodiment deals with the fourth problem and the fifth problem.

On the optical path of the light emitted from the semiconductor laser 70 as a laser light source, a transmission type diffraction grating 72 as a diffraction grating (first diffraction grating) is formed on one surface of a parallel substrate 71 as a substrate, and a transmission type diffraction grating 72 as a diffraction grating (first diffraction grating) is formed on the other surface. A light beam splitting element 74 as a light beam separating means is disposed on which a total reflection surface 73 as a double diffraction grating is formed.

A semi-transmissive diffraction grating 75 as a semi-reflective film is formed in a central part of the transmissive diffraction grating 72 . Also,
On the optical path of the light reflected by the semi-transmissive diffraction grating 75, a magneto-optical disk 77 as an optical information recording medium is disposed via an objective lens 76. Further, a first light receiving element 78 is disposed on the optical path of the primary light that is reflected by the magneto-optical disk 77 and is diffracted by the light beam splitting element 74 and proceeds. A second light receiving element 79 is disposed on the optical path of the O-order light T that is refracted by the light beam 74 and proceeds.

In such a configuration, the light emitted from the semiconductor laser 70 travels toward the beam splitting element 74 as diffused light. A portion of the light incident on the beam splitting element 74 is reflected by the semi-transmissive diffraction grating 75 having a high reflectance, and is focused by the objective lens 76 to form the magneto-optical disk 74.
The light is irradiated onto the surface of 7, thereby recording information and the like.

Further, by reading the recorded information signal, the reflected light from the magneto-optical disk 77 undergoes polarization rotation according to the signal due to the Kerr effect, and is again semi-transmitted by the beam splitting element 74. The light is guided to a type diffraction grating 75. Then, by passing through this semi-transmissive diffraction grating 75, the light is separated into O-order light T and first-order light, and each light is reflected separately by the total reflection surface 73 on the back surface thereof. Thereafter, the first-order light passes through the transmission-type diffraction grating 72 and is emitted to the outside and is guided to the first light-receiving element 78, while the O-order light T passes through the transmission-type diffraction grating 72 located at another location. The light is emitted to the outside and guided to the second light receiving element 79.

In this case, the first light receiving element 78 and the second light receiving element 79 are
As shown in FIGS. 22(a) and 22(b), each is divided into three parts, and the focus error signal can be detected using the beam size method, and the track error signal can be detected using the bush-pull method. Furthermore, the magneto-optical signal can be detected by determining the difference between the signal outputs detected by the first light receiving element 78 and the second light receiving element 79, respectively. However, when detecting a magneto-optical signal by such a method, the polarization direction of the light emitted from the semiconductor laser 70 and the lattice direction make an angle of 45 degrees, as shown in FIG. You need to adjust it accordingly.

Therefore, by forming the semi-transmissive diffraction grating 75 and the transmissive diffraction grating 72 in the beam splitting element 74 as described above, the reflected light from the magneto-optical disk 77 is transmitted to the semi-transmissive diffraction grating 75 of the beam splitting element 74. The transmission type diffraction grating 72 is used as the diffraction grating when the O-order light T and the first-order light K obtained by entering are reflected by the total reflection surface 73 and emitted to the outside.
As a result, it is possible to further increase the light utilization efficiency compared to the conventional method, and it is also possible to obtain an optical head that is small, lightweight, and low cost.

Furthermore, in the configuration described above, the semiconductor laser 70
By arranging a collimating lens (not shown) on the optical path where the light emitted from the semiconductor laser 70 heads toward the beam splitting element 74, the light emitted from the semiconductor laser 70 is guided to the beam splitting element 74 after passing through the collimating lens. As a result, only the parallel light among the eight incident lights is incident on the semi-transmissive diffraction grating 75, so that high-performance polarization separation can be performed and the light utilization efficiency can be further increased.

Next, a modification example in which signal detection is performed using the first light receiving element 78 and the second light receiving element 79 will be described.

First, as a first modification, a case will be described in which the astigmatism method is used to detect the focus error signal. Second
Figures 3(a) and 3(b) show the configuration. In this case, the second light receiving element 79 for detecting the O-order light T shown in FIG.
By appropriately changing the tilt and refractive index, astigmatism is generated in the O-order light T, and by arranging the second light-receiving element 79, which is divided into four, at the optimal position, focus error can be corrected using the astigmatism method. Signal detection can be performed. On the other hand, 1
By forming the first light receiving element 78 that detects the secondary light K into a two-split shape, it is possible to detect a tracking error signal using the bush-pull method.

Furthermore, as a second modification, a method of detecting a focus error signal using another astigmatism method will be described. Semi-transmission type diffraction grating 75 or transmission type diffraction grating 7
This is a method of generating astigmatism on the side of the primary light by modulating at least one of the two. In this case, since focus sensitivity is optimized by the degree of modulation of the grating pitch, a greater degree of freedom in design can be achieved than in the astigmatism method of the first modification described above.

Note that the focus error signal can be detected using either the beam size method or the astigmatism method.
Track error signals can be detected by a sample servo method in addition to the above-described continuous method. In addition, the transmission type diffraction grating 72 provided in one region through which only the 0th order light T passes only allows the Oth order light T to pass through, so if there is no manufacturing problem, there will be no performance problem even if it is not provided separately. It won't happen. Furthermore, although the substrate of the beam splitting element 74 here is a parallel flat plate, in order to optimize the distance between the first light receiving element 78 and the second light receiving element 79,
A similar effect can be obtained by using a shape like a wedge prism (not shown).

Next, one embodiment of the invention described in claims 1, 9, and 10 will be described as a second embodiment.
This will be explained based on FIGS. 5 to 29.

Note that this embodiment deals with the fourth problem and the fifth problem.

Output light a emitted from a semiconductor laser 80 as a laser light source passes through a collimating lens 81 and is directed to an objective lens 8.
2, a polarization separation diffraction grating 84 as a diffraction grating (first diffraction member) is formed on one surface of the substrate 83, and a total reflection surface 85 as a second diffraction member is formed on the other surface. A light beam separating element 86 is provided as a wedge-shaped light beam separating means. A semi-reflective film 87 is formed on the surface of the polarization separation grating 84 . Further, on the optical path of the light reflected by the semi-reflective film 87, an optical disc 88 as an optical information recording medium is disposed via a condensing lens 82.

In this case, one reflected light 89 obtained by being reflected by the semi-reflective film 87 and two transmitted lights 90.91a and 91b obtained by passing through the semi-reflective film 87 (see FIG. 26). The wedge angle θ of the wedge-shaped beam splitting element 86 was set so that the beam was guided to the optical disk 88. however,
The wedge angle O is.

If the angle between the surface on which the polarization separation diffraction grating 84 is formed and the horizontal plane is α, and the angle between the surface on which the total reflection surface 85 is formed and the horizontal plane is β, then θ=0−β. can.

Also, as shown in FIGS. 27 to 29, among the reflected light (main beam) 89 and transmitted light (sub beams) 91a and 91b reflected by the optical disc 88, the reflected light 8
Two 3-split light receiving elements 92.93 that receive the transmitted light 92.93 and two undivided light receiving elements 94.95 that receive the transmitted light 91a and 91b are arranged on the optical path of the collimating lens 81 on the semiconductor laser 80 side. did.

In such a configuration, the emitted light a emitted from the semiconductor laser 80 is turned into parallel light by the collimating lens 81, and is incident on the surface of the wedge-shaped beam separation means 86 on the side where the polarization separation diffraction grating 84 is formed. . At this time, assuming that the emitted light a is linearly polarized light that forms an angle of 45 degrees with the grating direction (perpendicular to the plane of the paper) of the polarization separation diffraction grating 84, the emitted light a first passes through the semi-reflective film 87 as shown in FIG. A portion of the reflected light 89 (hereinafter referred to as the main beam 89) is irradiated onto the surface of the optical disk 88, and transmitted light 90 (hereinafter referred to as the sub beam 90) that has passed through the semi-reflective film 87 is reflected. , separated into two by the polarization separation grating 84, and 0
The light is separated into an order light 91a (transmitted light) and a first order light 91b (diffraction light).

Then, the O-order light 91a is reflected by the total reflection surface 85 and passes through the polarization separation diffraction grating 84 again. At this time, since the total reflection surface 85 is shifted from the surface on the side where the polarization separation diffraction grating 84 is formed by the wedge angle O, the O-order light 91a is not parallel to the main beam 89 and is not parallel to the main beam 89. toward the objective lens 82 at an angle. On the other hand, the primary light 91b is diffracted by the polarization separation grating 84, reflected by the total reflection surface 85, and diffracted by the polarization separation grating 84 again. In this case as well, since the total reflection surface 85 has a wedge angle O, the incident angle when passing through the polarization separation grating 84 for the second time becomes large, and the diffraction angle also becomes large accordingly. 911] is also not parallel to the main beam 89, but is directed toward the objective lens 82 at a certain desired angle. Therefore, one main beam 29 (reflected light) and two sub beams 90 (0th order light 91a and first order light 9lb) obtained in this way are condensed by the objective lens 82. The optical disc 88 forms three spots.
This makes it possible to record information and enable a 3-beam tracking system.

In addition, three beams (one main beam 89, two sub beams 91a) reflected by the optical disk 88.

91b) passes through the objective lens 82 and enters the semi-reflective film 87 of the beam splitting element 86 again. Of these, two sub beams 91. a, 91. b is reflected by the semi-reflective film 87, condensed by the collimating lens 81, and received by two undivided light receiving elements 94 and 95 as shown in FIG. Signal Tr can be detected.

On the other hand, as shown in FIG. 27, one main beam 89 reflected by the optical disk 88 is transmitted through the semi-reflective film 87 and partially reflected) and then diffracted into the transmitted light 89a by the polarization separation diffraction grating 84. It is separated into light 89b depending on its polarization direction. After the transmitted light 89a is totally reflected by the total reflection surface 85, it passes through the polarization separation diffraction grating 84 again and heads toward the three-divided light-receiving elements 92 and 93. In this case, the transmitted light 89a is reflected by the wedge-shaped surface and the optical axis a of the emitted light a is changed. The light is not parallel to the light, but enters the collimator lens 81 at a predetermined angle, and is condensed by the collimator lens 81 and detected by one of the three-split light receiving elements 92. In addition, the diffracted light 89
After being reflected by the total reflection surface 85, the light beam b heads toward the polarization separation grating 84 again, or at this time, due to the reflection by the wedge-shaped surface, the angle of incidence on the polarization separation grating 84 is different from the first time. As a result, the diffraction angle becomes smaller and the light is emitted. In this case as well, the diffracted light 89b is not parallel to the optical axis of the emitted light a, but enters the collimating lens 81 at a predetermined angle and is condensed into the other three.
It is detected by the divided light receiving element 93. Therefore, since the main beam 89 is thus separated into the transmitted light 89a and the diffracted light 89b, the magneto-optical signal Mo can be detected from the difference in light intensity, and thereby the information recorded on the optical disk 88 can be detected. Can be played.

FIG. 29 also shows the non-divided light receiving element 94 described above. ．． 95 and two three-part light receiving elements 92 and 93. In this case, the main beam 89 is detected by two 3-split light receiving elements 92 and 93 that are arranged to be shifted back and forth with respect to the direction of the optical axis a0 and have different focal lengths, so the focus error signal FO is determined by the beam size. can be detected using a method.

As described above, the main beam 89 is split into three light receiving elements 92 .
93 and the sub beam 90 is detected by the non-divided light receiving element 94.
95, it becomes possible to detect the magneto-optical signal Mo, the focus error signal FO, and the track error signal Tr. Furthermore, in this case, the method for detecting the track error signal Tr may be the three-beam method or the bush-pull method. , a sample servo method can be adopted, thereby making it possible to correspond to various types of optical discs 88.

Furthermore, by making the beam splitting element 86 wedge-shaped, it becomes possible to create three beams, which enables a three-beam tracking method. Accordingly, it is possible to obtain an optical pickup that is compatible with the optical pickup device and is also smaller and lighter in weight.

Next, an embodiment of the invention set forth in claim 1.11 will be described based on FIGS. 30 to 34. Note that this embodiment deals with the sixth problem. Further, description of the same parts as those in the prior art (see FIG. 38) will be omitted.

As shown in FIG. 31, the beam separating element 96 as a beam separating means includes a transmission type diffraction grating 97 as a first diffraction member.
A certain angle (wedge angle) Δθ is applied to the transmission type diffraction grating 97.
A high reflection surface 98 as a second diffraction member arranged to form a
It has This beam splitting element 96 allows light emitted from a semiconductor laser 99 as a laser light source to collimate lens 1. It is located on the optical path toward OO.

In such a configuration, reflected light from the magneto-optical disk 101 is transmitted through the objective lens 102 and the collimating lens 100.
After sequentially passing through the transmission type diffraction grating 9 of the beam separation means 96
7 and is separated into transmitted light T and diffracted light. The transmitted light T is reflected by the high reflection surface 98 and transmitted through the transmission type diffraction grating 97 again, thereby becoming the light that has been transmitted twice.

On the other hand, the diffracted light is reflected by the high reflection surface 98,
It is diffracted again by the transmission type diffraction grating 97, thereby 2
The light is diffracted both times.

In this case, the diffraction conditional expression for the diffracted light is as follows (
(See Figure 32).

sinθi+sinθ. =λ/c ・(])sin(
θ. -280) + sin θ, (2) where 01: angle of incidence, Oo: to 1st diffraction angle 0: wedge angle, 01
: Second fold angle λ/wavelength, A : Pitch of diffraction grating Here, when θ1 is calculated, θ, = si, n-' [λ/A - ((λ/A)
−sinθ1) cos2θ+ 1− (λA −5i
nOi 5in201...(3)

Here, the diffraction axis deviation angle φd and the transmission axis deviation angle ψt are respectively defined as follows.

ψd = incident angle - 2nd diffraction angle = θl - θ ... (4) ψt = 2△O
...(5) Then, using these equations (4) and (5), find the angular difference (separation angle) φS between the diffracted light that was diffracted both times and the transmitted light T that was transmitted both times. and ψS−ψd−ψt=ei
-01-2Δ61 ・16).

Therefore, from this, as shown in Figure 30,
Since the two light-receiving elements 103 and 104 can be arranged close to each other next to the semiconductor laser 99, it is possible to separately produce a substrate for the semiconductor laser and a substrate for the light-receiving element. Therefore, with this, the semiconductor laser 99
Since the light-receiving elements 103 and 104 can be mounted separately, the assembly can be easily adjusted.

In this case, the shapes of the light-receiving elements 103 and 104 can be such that one has a four-divided light-receiving surface 105 and the other has a two-divided light-receiving surface 106, as shown in FIG. In this case, a tracking error signal can be detected using the two-divided light receiving surface 106 using the bush-pull method, and a focus error signal can be detected from the four-divided light receiving surface 105 using the astigmatism method. Note that in the case of sample servo tracking, the two-split light receiving surface may be undivided. The light receiving surface shown in FIG. 34(a) is for detecting a focus error signal using the beam size method. Further, when calibrating the track error signal using the bush-pull method, as shown in FIG. 34(b), by adding dividing lines 107 to the left and right at the broken line, calibration can be performed based on the difference in light amount between the left and right sides. Note that in the case of sample servo tracking, the dividing line 107 is unnecessary.

Next, a modification of this embodiment is shown in FIG. 35. In the above-mentioned embodiment, as shown in FIG. 31, the transmission type diffraction grating 97 and the high reflection surface 98 constituting the beam separation means 96 were separated, but here, a wedge 10 having a constant angle ΔO is used.
A transmission type diffraction grating 97 is formed on one side of the mirror 8, and a highly reflective surface 98 is formed on the other side. Even if formed in this way, similar effects can be obtained.

Effects of the Invention The invention described in claim 1 collimates light emitted from a laser light source using a collimating lens, focuses the collimated light using an objective lens, and irradiates it onto an optical information recording medium to record information. In an optical information recording and reproducing apparatus that detects an information reproduction signal, a track error signal, and a focus error signal by detecting the reflected light from the optical information recording medium, the light emitted from the laser light source is A first diffraction member having a semi-reflective film is provided on the optical path toward the objective lens, a second diffraction member is provided on the optical path on which the reflected light from the optical information recording medium passes through the first diffraction member, and this Since a light receiving element is provided to detect the transmitted light and the diffracted light that are separated by passing through the second diffraction member, the output optical system and the signal detection optical system can be integrated to save space. As a result, the number of parts of the entire device can be reduced, and a compact, lightweight, and inexpensive device can be obtained.

The invention according to claim 2 is a method for collimating light emitted from a laser light source using a collimating lens, condensing the collimated light using an objective lens, and irradiating the optical information recording medium onto an optical information recording medium to record information. In an optical information recording and reproducing device that reproduces information and detects track error signals and focus error signals by guiding the reflected light from the optical information recording medium to a light receiving element, a half-circle is placed on the optical path of the light emitted from the laser light source. Since the light beam separation means in which the front surface diffraction grating and the back surface diffraction grating are formed is provided, the space can be saved and the eight-ray optical system and the signal detection optical system can be integrated. As a result, the number of parts of the entire device can be reduced and a compact, lightweight, and inexpensive device can be obtained.

The invention according to claim 3 is a method of collimating light emitted from a laser light source using a collimating lens, condensing the collimated light using an objective lens, and irradiating it onto an optical information recording medium to record information. In an optical information recording and reproducing device that reproduces information and detects track error signals and focus error signals by guiding the reflected light from the optical information recording medium to a light receiving element, there is a light on the optical path of the light emitted from the laser light source. Since a diffraction grating with a semi-reflective film and a beam separation means with a total reflection surface are provided, the diffraction grating only needs to be fabricated on one side, making the fabrication work and handling very easy. Since the light receiving element and the light receiving element can be integrated into one unit, the number of parts can be significantly reduced, which simplifies the assembly work and provides a device that is even smaller and lighter in weight.

The invention according to claim 4 records information by collimating light emitted from a laser light source using a collimating lens, condensing the collimated light using an objective lens, and irradiating the optical information recording medium. In an optical information recording and reproducing device that reproduces information and detects focus error signals and track error signals by guiding reflected light from an optical information recording medium to a light receiving element in a signal detection optical system, the light emitted from a laser light source On the optical path of light, a semi-reflective first substrate having a first diffraction grating formed on one side and a surface of the first substrate on which the first diffraction grating is formed are arranged opposite to each other via a spacer. Since a double diffraction grating element consisting of a transparent second substrate with a second diffraction grating formed on the side surface is disposed, this double diffraction grating element can be used to combine transmitted light and diffracted light. By generating astigmatism on either side and detecting the focus error signal, it is possible to always achieve a stable signal peak that is not affected by wavelength fluctuations. Since the surfaces are arranged close to each other and are less susceptible to shift fluctuations in the primary light due to wavelength fluctuations, it is possible to perform signal detection with higher reliability than in the past.

The invention according to claim 5 records information by collimating the light emitted from the laser light source using a collimating lens, and then condensing the light using an objective lens and irradiating it onto an optical information recording medium. In an optical information recording and reproducing device that detects reflected light from a medium to reproduce information and detect track error signals and focus error signals, a wedge-shaped optical path is formed on the optical path between the collimating lens and the objective lens. A light beam separating means is provided in which a diffraction grating having a semi-reflective film is formed on one surface of the non-parallel substrate and a total reflection surface is formed on the other surface, and the light reflected by the light beam separating means is transmitted through the collimating lens. Since two light receiving elements for detecting the reflected light from the optical information recording medium are arranged on the optical path on the laser light source side, such a diffraction grating and a total reflection surface are formed on both sides of the non-parallel substrate. Since the zero-order light and the first-order light are spot-separated using a light beam separation means, it is easy to design the layout of the entire optical system. Because of this arrangement, the collimated light is incident on the diffraction grating, which allows high-performance polarization separation to be performed, thereby further increasing light utilization efficiency.

The invention according to claim 6 records information by collimating the light emitted from the laser light source using a collimating lens, and then condensing the light using an objective lens and irradiating it onto an optical information recording medium. In an optical information recording and reproducing device that detects reflected light from a medium to reproduce information and detect track error signals and focus error signals, a non-parallel substrate is provided on the optical path between the collimating lens and the objective lens. A light beam separating means is provided in which a diffraction grating having a semi-reflective film is formed on one surface and a total reflection surface in the shape of a wedge prism is formed on the other surface, and the light reflected by the light beam separating means is transmitted through the collimating lens. Since two sets of two light receiving elements for detecting the reflected light from the optical information recording medium are arranged on the optical path on the semiconductor laser side,
By making the total reflection surface into a wedge prism shape and arranging two sets of two light receiving elements, it is possible to detect the focus error signal using the double knife method. The accuracy can be made much looser than before, and stable signal detection can always be performed.

The invention according to claim 7 records information by condensing light emitted from a laser light source with an objective lens and irradiating it onto an optical information recording medium, and detects reflected light from the optical information recording medium. In an optical information recording and reproducing device that reproduces information and detects track error signals and focus error signals, a diffraction grating is provided on one surface of the substrate on the optical path of the light emitted from the laser light source toward the objective lens. is formed, a semi-transparent layer is formed on a part of the surface, and a total reflection surface is formed on the other surface. A light beam separating means is provided, and a first light beam is disposed on the optical path of the primary light that is diffracted by the light beam separating means and propagates. A light receiving element is provided, and the light beam is refracted by the light beam separating means and proceeds.
Since the second light receiving element is arranged on the optical path of the order light, when the 0th order light and the 1st order light separated by the diffraction grating of the light beam separation means are reflected by the total reflection surface and emitted to the outside, the diffraction Since the light passes through a transparent region other than the semi-transparent layer in the grating, it is possible to further improve the light utilization efficiency compared to the conventional method.

The invention as set forth in claim 8 is based on the configuration of the invention as set forth in claim 7 as described above, further comprising a collimating lens disposed in the optical path ``2'' during which the light emitted from the laser light source heads toward the beam separating means. Since only the parallel light of the emitted light is incident on the diffraction grating, it is possible to perform high-performance polarization separation, thereby further increasing the light utilization efficiency.

The invention according to claim 9 records information by condensing light emitted from a laser light source by an objective lens through a collimating lens and irradiating it onto an optical information recording medium, and also records information on the optical information recording medium. In an optical information recording and reproducing device that detects reflected light from a camera to reproduce information, detect a track error signal, and a focus error signal, the emitted light passes through the collimating lens and heads toward the objective lens. A wedge-shaped light beam separating means is disposed on the road in which a diffraction grating is formed on one surface of a substrate, a semi-reflective film is formed on the surface of the diffraction grating, and a total reflective surface is formed on the other surface, and the emitted light is transmitted through the semi-reflective film. a wedge of the light beam separating means having a wedge shape so that one main beam obtained by reflection and two sub beams obtained by passing through the semi-reflective film are guided to the optical information recording medium; Since the angle is set, the outgoing light enters the semi-reflective film formed on the surface of the diffraction grating of the beam separation means, and the light reflected by the semi-reflective film is used as the main beam, and the transmitted light is used as the sub beam. Therefore, it becomes possible to perform three-beam tracking, and this makes it possible to make this device compatible with various devices that use magneto-optical disks, CDs, etc. as optical information recording media, and expands the range of applications even further than before. It is something that can be expanded.

The invention according to claim 10 is the configuration of the invention according to claim 9 as described above, further comprising two three-part light receiving units for receiving the main beam out of the main beam and the sub beam reflected by the optical information recording medium. Since two non-divided light receiving elements are provided to receive the sub beams, the main beam and sub beam reflected by the optical information recording medium are all received by each light receiving element without wasting the light, which is different from the conventional method. Compared to this, the light utilization efficiency can be further improved.

The invention as set forth in claim 11 is such that the emitted light is collimated by a collimating lens and then focused by an objective lens and irradiated onto the surface of an optical information recording medium to record information, and the light is In an optical information recording/reproducing device that detects focus error signals and track error signals by detecting reflected light from an information recording medium using a light receiving element, a transmission type diffraction grating and a transmission type diffraction grating arranged at a certain angle are used. By providing a beam separating means having a high reflective surface, it is possible to change the optical path of transmitted light and reflected light separated by this beam separating means. There is no need to provide light receiving elements on both sides, and as a result, the substrate for the laser light source and the substrate for the light receiving element can be created and mounted separately.
Compared to the past, assembly and adjustment are simplified and work efficiency can be increased.

A twelfth aspect of the invention provides a semi-reflective first substrate having a first diffraction grating formed on one side thereof, and a surface of the first substrate on which the first diffraction grating is formed, which is arranged to face each other via a spacer. Since a double diffraction grating element consisting of a transparent second substrate on which a second diffraction grating is formed is provided on the side surface thereof, the grating surfaces of the first diffraction grating and the second diffraction grating face each other and are sealed. Moreover, the lattice shape is stable and these two
Because the two diffraction gratings are close to each other, the primary light is less susceptible to shift fluctuations due to wavelength fluctuations, and by making the outer - surface on which the diffraction gratings are formed a semi-transparent surface, It has a high-precision beam splitter function and can be applied to optical information recording and reproducing devices.
It is possible to further reduce the number of parts and obtain a device that is smaller and lighter in weight.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the invention as claimed in claims 1 and 2, FIG. 2 is a configuration diagram showing a state of a dual-type diffraction grating,
Figure 3 is an explanatory diagram of the dual-type diffraction grating viewed from behind the laser light source, Figure 4 is an explanatory diagram showing the principle of calibrating the focus error signal using the light receiving element, and Figure 5 is the diffraction efficiency of the high-density diffraction grating. FIG. 6 is a configuration diagram showing an embodiment of the invention according to claim 1.3, and FIG. 7 is a first embodiment of the invention according to claims 1 and 4.12. FIG. 8 is a side view showing the optical path state of the light incident on the dual-type diffraction grating and separated, and FIG. FIG. 10 is a configuration diagram showing a third embodiment of the invention as claimed in claim 1.4.12. FIG. 11 is a configuration diagram showing the arrangement of the cylindrical lens in the signal detection optical system. The explanatory diagram, FIG. 12, is in accordance with claims 1, . A configuration diagram showing the first embodiment of the invention described in 5.6, FIG. 13 is a front view showing the state of the modulated diffraction grating, and FIG. 14 is a characteristic diagram showing the polarization dependence of the diffraction grating. Fig. 15 is a configuration diagram showing a second embodiment of the invention as claimed in claims 1, 5.6, Fig. 16 is a front view showing the arrangement state of the light receiving elements, and Fig. 17 is a configuration diagram showing the arrangement of the light receiving elements. FIG. 18 is a front view showing the state of the diffraction grating, FIG. 18 is a perspective view showing the state of the light beam separating means which is the third embodiment of the invention as claimed in claims 1 and 5.6, and FIG. 19 is the arrangement of the light receiving element. The front view of FIG. 20 showing the installed state is according to claim 1. ．． 7.8 is a configuration diagram showing an embodiment of the invention, FIG. 21 is an explanatory diagram showing the state of the diffraction grating, FIG. 22 is an explanatory diagram showing the state of the surface shape of the light receiving element, and FIGS. Fig. 24 is a front view showing a modified example of the light receiving element, Fig. 25 is a configuration diagram showing an embodiment of the invention as set forth in claims 1, 9, and 10, and Fig. 26 is a traveling path within the emitted light beam separation means. FIG. 27 is an optical path diagram showing the traveling path of the return light from the optical information recording medium within the beam separation means, and FIG. 28 is a diagram showing the wiring circuit connected to the undivided and 3-divided light receiving elements Circuit diagram shown, 2nd
FIG. 9 is an optical path diagram showing the relationship between the arrangement positions of undivided and three-divided light receiving elements on the optical path, FIG. 30 is a configuration diagram showing an embodiment of the invention as claimed in claims 1 and 11, and FIG. FIG. 32 is an explanatory diagram showing various diffraction angles, FIG. 33 is a front view of a light receiving element, FIG. 34 is a side view showing a modified example of the light receiving element, and FIG. 35 is a side view showing a light beam separating means. is a front view showing a modified example of the light beam separation means, FIG. 36 is a block diagram showing a first conventional example, and FIG. 37 is a block diagram showing a second conventional example,
FIG. 38 is a configuration diagram showing a fourth conventional example. 30...Laser plateau, 32...Semi-reflective film, 33...
・Surface diffraction grating, 34... Back diffraction grating, 35...
Collimating lens, 36...Objective lens, 37...
Optical information recording medium, 38... Light receiving element, 40... Diffraction grating, 41... Total reflection surface, 42... Semi-reflection film, 43.
...Laser light source, 45...First substrate, 45a...First diffraction grating, 47...Second substrate, 47a...Second diffraction grating, 48...Collimating lens, 49...Objective Lens, 50... Optical information recording medium, 51... Signal detection optical system, 52a, 52b... Light receiving element, 55... Laser light source, 56... Collimating lens, 57... Non-parallel substrate , 58... Light beam separation means, 59... Diffraction grating, 59a... Semi-reflection film, 60 Total reflection surface, 61... Objective lens, 62... Optical information recording medium, 64.65...
- Light receiving element, 70... Laser light source, 71... Substrate,
72... Diffraction grating, 73... Total reflection surface, 74...
Light beam separating means, 75... Semi-transparent layer, 76... Objective lens, 77... Optical information recording medium, 78... First light receiving element, 79 - Second light receiving element, 80... Laser light source, 81
...Collimating lens, 82...Objective lens, 83.
... Substrate, 84 ... Diffraction grating, 85 ... Total reflection surface,
86... Luminous flux separation means, 87... Semi-reflective film, 92° 93... 3-split light receiving element, 94.95... Undivided light receiving element, 96... Luminous flux separating means, 97... Transmission type diffraction grating, 98...high reflection surface, 99...laser light source, 1
00... Collimating lens, 101... Optical information recording medium, 1, 02... Objective lens, 103, 104...
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Claims (1)

[Claims] 1. The light emitted from the laser light source is collimated by a collimating lens, the collimated light is focused by an objective lens, and is irradiated onto an optical information recording medium to record information, In an optical information recording and reproducing apparatus that detects an information reproduction signal, a track error signal, and a focus error signal by detecting reflected light from the optical information recording medium, the emitted light emitted from the laser light source is transmitted to the objective. A first diffraction member having a semi-reflective film is provided on the optical path toward the lens, and a second diffraction member is provided on the optical path on which the reflected light from the optical information recording medium passes through the first diffraction member, An optical information recording and reproducing apparatus characterized by being provided with a light receiving element that detects transmitted light and diffracted light that are separated and obtained by passing through the second diffraction member. 2. The light emitted from the laser light source is collimated by a collimating lens, and the collimated light is focused by an objective lens and irradiated onto an optical information recording medium to record information, and the information is recorded from the optical information recording medium. In an optical information recording and reproducing device that reproduces information and detects track error signals and focus error signals by guiding the reflected light of the laser beam to a light receiving element, the reflected light of the laser light source is incident on a surface located on the optical path side of the light emitted from the laser light source. A surface diffraction grating having a semi-reflective film that reflects a part of the light is formed, and a light beam separation means having a back diffraction grating is provided on the surface opposite to this surface, An optical information recording/reproducing device characterized in that the light receiving element is disposed on an optical path. 3. The light emitted from the laser light source is collimated by a collimating lens, and the collimated light is focused by an objective lens and irradiated onto an optical information recording medium to record information, and the optical information recording medium In an optical information recording and reproducing device that reproduces information and detects track error signals and focus error signals by guiding the reflected light from the laser light source to a light receiving element, the light incident on the surface located on the optical path side of the light emitted from the laser light source is used. A diffraction grating having a semi-reflective film that reflects a part of the light is provided, and a light beam separation means is provided on the surface opposite to this surface with a total reflection surface, so that the light beam on the side where the laser light source is provided is provided. An optical information recording/reproducing device characterized in that the light receiving element is arranged on a road. 4. The light emitted from the laser light source is collimated by a collimating lens, and the collimated light is focused by an objective lens and irradiated onto an optical information recording medium to record information and record information from the optical information recording medium. In an optical information recording and reproducing device that reproduces information and detects focus error signals and track error signals by guiding reflected light to a light receiving element in a signal detection optical system, a light beam on the optical path of light emitted from the laser light source is used. a semi-reflective first substrate having a first diffraction member formed on one side; 1. An optical information recording and reproducing device characterized in that a double diffraction grating element is disposed, the double diffraction grating element comprising a transparent second substrate on which a double diffraction member is formed. 5. The light emitted from the laser light source is collimated by a collimating lens, and then focused by an objective lens and irradiated onto an optical information recording medium to record information, and the reflected light from the optical information recording medium is In an optical information recording and reproducing device that detects and reproduces information, detects a track error signal, and a focus error signal, a wedge-shaped non-parallel substrate is provided on one surface of a wedge-shaped optical path between the collimating lens and the objective lens. A light beam separating means is provided in which a diffraction grating having a semi-reflective film is formed and a total reflection surface is formed on the other surface, and the light reflected by the light beam separating means is transmitted through the collimating lens to the laser light source side. An optical information recording/reproducing device characterized in that two light receiving elements for detecting reflected light from the optical information recording medium are arranged on a road. 6. Recording information by collimating the light emitted from the laser light source using a collimating lens, and then focusing the light using an objective lens and irradiating it onto an optical information recording medium, as well as recording the light reflected from the optical information recording medium. In an optical information recording and reproducing device that detects and reproduces information, detects a track error signal, and a focus error signal, a semi-reflective film is provided on one surface of a non-parallel substrate on an optical path between the collimating lens and the objective lens. A beam separating means is disposed on which a diffraction grating is formed and a total reflection surface in the shape of a wedge prism is formed on the other surface, and the light reflected by the beam separating means passes through the collimating lens on the laser light source side. An optical information recording/reproducing apparatus characterized in that two sets of two light receiving elements for detecting reflected light from the optical information recording medium are disposed on an optical path. 7. The light emitted from the laser light source is focused by an objective lens and irradiated onto the optical information recording medium to record information, and the reflected light from the optical information recording medium is detected to reproduce the information. , in an optical information recording/reproducing device that detects a track error signal and a focus error signal, a diffraction grating is formed on one surface of a substrate on an optical path of light emitted from the laser light source toward the objective lens, and a part of the diffraction grating is formed. A light beam separation means having a semi-reflective film on one surface and a total reflection surface on the other surface is disposed, and a first light receiving element is disposed on the optical path of the primary light diffracted by the light beam separation means and propagating. , a second light beam is arranged on the optical path of the zero-order light that is refracted by the light beam separating means and proceeds.
An optical information recording/reproducing device characterized in that a light receiving element is provided. 8. The optical information recording and reproducing apparatus according to claim 7, further comprising a collimating lens disposed on the optical path of the light emitted from the laser light source as it travels toward the beam separation means. 9. Recording information by condensing the light emitted from the laser light source with an objective lens via a collimating lens and irradiating it onto an optical information recording medium, and detecting the reflected light from the optical information recording medium. In an optical information recording and reproducing device that reproduces information and detects a track error signal and a focus error signal, a substrate is provided on one surface of the substrate on the optical path during which the emitted light passes through the collimating lens and heads toward the objective lens. A wedge-shaped light beam separating means is provided in which a diffraction grating is formed, a semi-reflective film is formed on one surface, and a total reflective surface is formed on the other surface, and the emitted light is reflected by the semi-reflective film. The wedge angle of the wedge-shaped beam separating means is set so that one main beam and two sub beams obtained by passing through the semi-reflective film are guided to the optical information recording medium. Features of optical information recording and reproducing device. 10. Of the main beam and sub beam reflected by the optical information recording medium, two 3-split light receiving elements are provided to receive the main beam, and two undivided light receiving elements are provided to receive the sub beam. The optical information recording/reproducing apparatus according to claim 9. 11. After the light emitted from the laser light source is collimated by a collimating lens, it is focused by an objective lens and irradiated onto the surface of an optical information recording medium to record information, and the reflected light from the optical information recording medium is In an optical information recording and reproducing device that detects a focus error signal and a track error signal by detecting the focus error signal and the track error signal using a light receiving element, a transmission type diffraction grating is provided on the optical path of the light emitted from the laser light source toward the collimating lens. An optical information recording/reproducing apparatus characterized in that a light beam separating means having a high reflection surface arranged at a constant angle is provided on the transmission type diffraction grating. 12. A semi-transparent first substrate with a first diffraction member formed on one side, and a surface of the first substrate facing the side on which the first diffraction member is formed, with a spacer interposed therebetween. 1. A double diffraction grating element comprising: a second transparent substrate on which a second diffraction member is formed;