JPH02292732A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the number of parts in an entire optical system and to make an entire device small in size and light in weight by positioning and disposing a 0th- order light detector and a 1st-order light detector on the same plane on an optical path obtained separating reflected light beam from an optical information recording medium by an optical path separation means and conducting it to a signal detection optical system. CONSTITUTION:After the light beam projected from a laser light source 30 passes through the optical path separation means 32 of a plane parallel plate 33 and is shaped, it irradiates the optical information recording medium 37 through an objective lens 36 and the reflected light beam is conducted to the optical path separation means 32 again. Then, it passes through a diffraction grating 35 consisting of equal pitches and is separated to 0th-order light and 1st-order light, which are reflected by the reflecting surface 34 of the means 32, pass through the diffraction grating 35 again and are projected to the outside to be conducted to the 0th-order light detector 39 and the 1st-order light detector 40 respectively, thereby detecting a magneto-optical signal, a focus error signal and a reproducing signal. Thus, the number of the parts is drastically reduced as compared with that of a conventional one and the constitution of the entire device is made small in size and light in weight.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical information recording and reproducing apparatus that detects a focus error signal and a track error signal using reflected light from an optical information recording medium.

2. Description of the Related Art A first conventional example of an optical information recording/reproducing apparatus is disclosed in Japanese Patent Application Laid-Open No. 61-230634. This will now be explained based on FIG. The light emitted from the semiconductor laser 1 is collimated by the collimating lens 2, and the collimated end is incident on the polarizing beam splitter grating 3, so that the polarization direction of the incident beam 4 is changed so that its electric vector is parallel to the polarizing beam splitter grating. Because it is parallel to the groove 3, the diffracted light becomes 5 and becomes 17.
The light enters a four-wavelength plate grating 6, becomes a circularly polarized light beam, is focused by a lens 7, and is irradiated onto the surface of an optical disk 8 serving as an optical information recording medium. Further, the reflected light from the optical disk 8 is converted into a linearly polarized light wave by the 1/4 wavelength plate grating 6, transmitted through the polarization beam splitter grating 3, and the O-order diffracted light 9
and enters the critical angle diffraction grating 10. The incident light undergoes critical angle diffraction twice and total reflection, becomes diffracted light 11, and is detected by a four-split photodetector 12. This results in
The focus error signal is detected by the difference signal between the left and right light receiving surfaces, and the track error signal is detected by the difference signal from the light receiving surface in the direction perpendicular to the page.

Further, as a second prior art example, there is a patent application filed by the present applicant in Japanese Patent Application No. 1518/1983. As shown in FIG. 9, light emitted from a semiconductor laser 13 is collimated by a collimating lens 14, passed through a beam shaping prism 15, reflected by a beam splitter 16, and condensed by an objective lens 17. The light is irradiated onto the surface of the magneto-optical disk 18, thereby recording information. Further, the reflected light from the magneto-optical disk 18 passes through the beam splitter 16, is focused by the detection lens 19, and is guided to the dual grating 20. In this dual grating 20, gratings 20a and 20b having different diffraction efficiencies depending on the polarization direction are formed on both the front and back surfaces, and light is transmitted through these two gratings 20.
a, 20b, the light is separated into O-order light T and 1st-order 9K, and the 0-order light T is guided to a 4-split light receiving element 21, and the 1st-order 9K is guided to a 2-split light receiving element 22, respectively.

Then, when detecting the magneto-optical signal, it is detected by the difference in light intensity between the O-order light T and the 1-dimensional light K, the focus error signal is detected by the O-order light T using the astigmatism method, and the track error signal is detected by the 1-dimensional light T. Detection can be performed using K.

Problems to be Solved by the Invention First of all, in the case of the first conventional example, it can be applied when a CD or a write-once optical disk 8 is used as the optical information recording medium. There is no function to detect signals. In addition, this device solves the fundamental drawback of gratings such as the polarizing beam splitter grating 3 and the quarter-wave plate grating 6, that is, the diffraction angle fluctuates in response to wavelength fluctuations. Not yet.

Therefore, as in the second conventional example, a dual grating 20 is used, which is compatible with not only the optical disk 8 but also the magneto-optical disk 18, and which has gratings 20a and 20b formed on the front and back surfaces of the substrate. In the case of an apparatus configured as follows, it is possible to significantly suppress positional deviation of the spot due to wavelength fluctuations. However, when two gratings 20a and 20b are used as in this device, the two gratings 20a and 20b are
It is very difficult to align the grating directions of There is a drawback that the variation in signal detection sensitivity for each dual grating 20 becomes large.

Therefore, instead of using two gratings 20a and 2ob on both the front and back surfaces, as shown in FIG. Light reflected by an optical information recording medium (for example, a magneto-optical disk) is guided to a light receiving element 28 through an optical path separating member 26 having a surface 25 through a condensing lens 27 in a signal detection optical system 29. There is an application filed by the present applicant as related to an earlier application, which was constructed by being arranged on the road.

However, even with this configuration, the number of parts in the entire optical system cannot be said to be significantly reduced compared to conventional systems, and this poses the problem that it is not possible to make the entire device smaller and lighter. .

Means for Solving the Problem Therefore, in order to solve such problems, claim 1
The described invention collects light emitted from a laser light source using an objective lens to form a light spot and irradiates it onto an optical information recording medium to record information, and also collects reflected light from the optical information recording medium. In an optical information recording/reproducing device that guides the light to a signal detection optical system and detects a track error signal, a focus error signal, and furthermore a reproduction signal, the light emitted from the laser light source is guided to the optical information recording medium. An optical path separating means is provided on the optical path, and includes a semi-transparent reflective surface formed on one surface of a parallel plate located on the laser light source side and a diffraction grating formed at equal pitches on the other surface, and the optical path separating means is provided on the optical path. A zero-order photodetector and a first-order photodetector were disposed in the same plane on the optical path where the reflected light was separated by the optical path separating means and guided to the signal detection optical system.

In the invention as claimed in claim 2, the light emitted from the laser light source is focused by an objective lens to form a light spot, and the light spot is irradiated onto an optical information recording medium to record information. In an optical information recording and reproducing device that guides reflected light to a signal detection optical system to detect a track error signal, a focus error signal, and furthermore a reproduction signal, light emitted from the laser light source is guided to the optical information recording medium. On the optical path between the parallel plates, a semi-transparent reflective surface is formed on one side of the parallel plate located on the laser light source side, and an optical path separation means is provided on the other side of the parallel plate on which a diffraction grating having a modulation pitch or curvature is formed. A zero-order photodetector and a first-order photodetector are arranged in the same plane on an optical path in which reflected light from the optical information recording medium is separated by the optical path separating means and guided to the signal detection optical system. Established.

According to the invention described in claim 1, the light emitted from the laser light source passes through the parallel plate optical path separation means and is beam-shaped, and then is irradiated onto the information recording medium through the objective lens, and its reflection is reflected. The light is guided to the optical path separation means again, passes through the diffraction grating with equal pitches, is separated into O-order light and first-order light, is reflected by the reflection surface, passes through the diffraction grating again, and is sent to the outside. A magneto-optical signal, a focus error signal, and a reproduction signal can be detected by being emitted to a zero-order photodetector and guided to a first-order photodetector, respectively.

According to the invention set forth in claim 2, the light emitted from the laser light source passes through the parallel plate optical path separation means and is beam-shaped, and then is irradiated onto the optical information recording medium through the objective lens, and the reflected light is The light is again led to the optical path separation means, passes through the diffraction grating with its modulation pitch or curvature, is separated into θ-order light and first-order light, is reflected by the reflecting surface, and passes through the diffraction grating again. is emitted to the outside, and 0
A magneto-optical signal, a focus error signal, and a reproduction signal can be detected by being guided to a secondary photodetector and a primary photodetector, respectively.

Embodiment An embodiment of the invention set forth in claim 1 will be described with reference to FIGS. 1 to 3. A parallel plate single-sided grating 32 serving as an optical path separation means is disposed on the optical path where the light emitted from the laser light source 30 is guided to the illumination optical system 31. This parallel plate type single-sided grating 32 has a semi-transparent reflective surface 34 formed on one side of the parallel plate 33 located on the laser light source 30 side, and the opposite side has straight lines with equal pitches. A shaped diffraction grating 35 is formed. In this case, parallel plate type single-sided grating 3
2 is arranged so as to be able to beam-shape the emitted light in an elliptical shape. Further, the reflecting surface 34 on which the emitted light is incident has a so-called half mirror-like structure that transmits a part of the incident light and reflects the part,
On the other hand, the diffraction grating 35 on the opposite side has the ability to vary its diffraction efficiency depending on the polarization direction, as shown in FIG. In addition, the parallel plate type single-sided grating 3
A magneto-optical disk 37 as an optical information recording medium is disposed on the optical path of the light that has passed through the optical system 2 via an objective lens 36.

Further, on the optical path where the reflected light from the magneto-optical disk 37 is reflected by the parallel plate single-sided grating 32 and guided to the signal detection optical system 38, there is a 0th-order photodetector 39 divided into 4 parts and a 1st-order photodetector 39 Detectors 40 are arranged in the same plane.

In such a configuration, the emitted light from the laser light source 30 passes through the reflective surface 34 of the parallel plate type single-sided grating 32 and the diffraction grating 35 located on the opposite side thereof, thereby eliminating astigmatism caused by the parallel plate 33. This action results in beam-shaped light. The beam-shaped output light enters the objective lens 36 to form a light spot, and in this state is irradiated onto the surface of the magneto-optical disk 37, thereby recording information.

Further, the reflected light from the magneto-optical disk 37 enters the parallel plate type single-sided grating 32 again from the diffraction grating 35 side via the objective lens 36. After the diffraction grating 35 polarizes and separates the O-order light T (transmitted light) and the 1-dimensional K (diffraction light), a portion of these two lights is reflected by the reflective surface 34 and returns to the diffraction grating 35. The light returns, passes through this, and is emitted to the outside.

Thereafter, the 0th order light T and the 1st order light K are transmitted to the Oth order photodetector 39 and the 1st order photodetector 4 arranged in the signal detection optical system 38.
The light is received by each light receiving surface of 0 and 0. Thereby, the magneto-optical signal can be detected based on the difference in light intensity between the zero-order light T and the one-dimensional light K.

Further, the focus error signal can be detected by an astigmatism method using astigmatism generated on the zero-order light T side. Furthermore, the track error signal can be detected by the well-known push-pull method or the like.

As described above, by disposing the parallel plate single-sided grating 32 on the optical path of the illumination optical system 31 where the light emitted from the laser light source 30 is guided to the magneto-optical disk 37, the conventional illumination optical The beam shaping prism and beam splitter used in the system become unnecessary, and by using the parallel plate type single-sided grating 32, the illumination optical system 31 and the signal detection optical system 38 can be connected with one optical component. As a result, the number of parts can be significantly reduced compared to the conventional method, making it possible to realize a smaller, lighter, and more cost-effective overall device configuration.

Next, an embodiment of the invention according to claim 2 is shown in FIGS. 4 and 5.
This will be explained based on the diagram. This embodiment is based on the above-mentioned claim 1.
Regarding the case where the shape of the diffraction grating 35 of the parallel plate type single-sided grating 32 in the embodiment of the described invention is changed,
This is the same as described above, and there is no difference in other configurations.

That is, a linear diffraction grating 35 with a modulated pitch is formed on the surface of the parallel plate type single-sided grating 32 on the magneto-optical disk side, so that the diffracted light is converged or diverged. . In this way, the diffraction grating 35
By changing the modulation pitch, the diffraction grating 35 has an effect equivalent to that of a cylindrical drill lens, which causes astigmatism on the primary light K side.

By arranging the primary photodetector 40 divided into four parts on the optical path on the primary light K side, a focus error signal can be detected.

Therefore, in this embodiment, the modulated pitched diffraction grating 3
5 to generate astigmatism, the degree of freedom in the amount of astigmatism generated can be increased compared to the embodiment of the invention set forth in claim 1. This increases the focus error signal detection sensitivity ( (S-curve) can be further enhanced.

Next, the O-order photodetector 39 and the 1 Next, a modification of the configuration of the photodetector 40 will be described.

In the two embodiments described above, astigmatism was generated in the O-order light T or the 1st-order 9K, and the focus error signal was detected by the astigmatism method, but in this embodiment, the focus error signal was detected by the astigmatism method. Since the beam size method (area density method) is used to detect signals, the configurations of the O-order photodetector 39 and the primary photodetector 40 have been changed accordingly.

That is, on the optical paths of the 0th-order light T and the 1st-order light K, the O-order photodetector 39 and the 1st-order photodetector 40, which are each divided into three parts, are arranged. In this case, the method for detecting various signals is shown in Figure 7 (a
), (b), and (c). First, Figure 7 (b
) shows when the magneto-optical disk is at the focused point, and FIGS. 7(a) and 7(c) show the case where the focus is shifted back and forth from this point.

At this time, the focus error signal FO is Fo = (a + c
-b)-(dtenf-e)- It can be detected by (1).

Further, the magneto-optical signal MO can be detected using the difference in light intensity between the two photodetectors as follows: Mo=(a+b+c)-(d+e+f)- (2) Furthermore, the track error signal Tr is Using the light-receiving surface of
It can be detected by

As mentioned above, by using the beam size method,
Compared to the astigmatism method used in the two embodiments described above, it is possible to have a larger tolerance for deviation of the light spot.
Accordingly, assembly adjustment becomes easier, thereby further improving productivity.

Effects of the Invention In the invention described in claim 1, an optical path separating means is provided on the optical path of the light emitted from the laser light source, in which a semi-transparent reflective surface is formed on one surface and a diffraction grating with an equal pitch is formed on the other surface. This eliminates the need for beam shaping prisms and beam splitters used in conventional illumination optical systems, and by using such optical path separation members, the illumination optical system and signal detection optical system can be connected to one It can be done with optical parts,
As a result, the number of parts can be significantly reduced compared to the conventional system, and the overall structure of the device can be made smaller, lighter, and cost-effective.

In the invention as claimed in claim 2, there is provided an optical path separating means in which a semi-transparent reflective surface is formed on one surface of the optical path of the light emitted from the laser light source, and a diffraction grating having a modulation pitch or curvature is formed on the other surface. Since it is possible to generate astigmatism by using a diffraction grating with a modulation pitch, it is possible to have a greater degree of freedom in the amount of astigmatism generated. The detection sensitivity (S-curve) of focus error signals can be further improved compared to the described invention.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the invention as claimed in claim 1,
FIG. 2 is a side view showing the front separation member, FIG. 3 is a waveform diagram showing the polarization dependence of the diffraction efficiency of the diffraction grating, and FIG. 4 is an optical path diagram showing an embodiment of the invention as claimed in claim 2. , FIG. 5 is a plan view showing the surface shape of the diffraction grating of the forward separation member, FIG. 6 is an optical path diagram showing a modified example of the O-order photodetector and the first-order photodetector, and FIG. 7(a) (b) and (c) are front views showing the principle of signal detection using the various detectors, Fig. 8 is a block diagram showing the first conventional example, and Fig. 9 (a) is the second conventional example. FIG. 9(b) is a circuit diagram showing the principle of detecting various signals, and FIG. 10 is a configuration diagram showing an example related to a previous application by the present applicant. 30... Laser light source, 32... Optical path separation means, 33
...Parallel plate, 34...Reflecting surface, 35...Diffraction grating, 36...Objective lens, 37...Optical information recording medium, 38...Signal detection optical system, 39...O Secondary photodetector, 4o/1st photodetector output 1 applicant Rico J Co., Ltd. Is there 5 diagrams and diagrams of bacteria? Diagrams (a) (b) (C) Collaboration with Jin Pico, Kufu Bib

Claims (1)

[Claims] 1. The light emitted from the laser light source is focused by an objective lens to form a light spot and irradiated onto an optical information recording medium to record information, and to record information from the optical information recording medium. In an optical information recording and reproducing device that guides reflected light to a signal detection optical system to detect a track error signal, a focus error signal, and furthermore a reproduction signal, light emitted from the laser light source is guided to the optical information recording medium. On the optical path between the
Optical path separating means is provided in which a semi-transparent reflective surface is formed on one surface of a parallel plate located on the laser light source side and a diffraction grating of equal pitch is formed on the other surface, so that the reflected light from the optical information recording medium is Optical information recording and reproducing characterized in that a zero-order photodetector and a first-order photodetector are arranged in the same plane on an optical path separated by an optical path separating means and guided to the signal detection optical system. Device. 2. The light emitted from the laser light source is focused by an objective lens to form a light spot and irradiated onto an optical information recording medium to record information, and the reflected light from the optical information recording medium is detected by signal detection optics. In an optical information recording and reproducing apparatus that detects a track error signal, a focus error signal, and furthermore, a reproduction signal, the light emitted from the laser light source is on the optical path while being guided to the optical information recording medium. ,
Optical path separating means is provided on one surface of a parallel plate located on the laser light source side, on which a semi-transparent reflective surface is formed, and on the other surface, a diffraction grating having a modulation pitch or curvature is formed, and the optical path separating means is provided, and the optical path separation means is provided with a semi-transparent reflective surface formed on one surface located on the side of the laser light source, and an optical path separation means formed on the other surface, on which a diffraction grating having a modulation pitch or curvature is formed. A zero-order photodetector and a first-order photodetector are disposed in the same plane on the optical path where the reflected light is separated by the optical path separating means and guided to the signal detection optical system. Optical information recording and reproducing device.