JPH07296438A - Magneto-optical pickup - Google Patents

Abstract

PURPOSE:To obtain an extremely small-sized magneto-optical pickup with which good-quality signals are obtainable. CONSTITUTION:A quartz crystal prism 3 is formed with a polarizing film 2 on its upper surface and a polarizing film 4 on its back surface. This quartz crystal prism 3 rotates the plane of polarization of propagating light by 45 deg.. This polarizing film 2 allows 30% transmission of S polarized light and allows 100% transmission of P polarized light. The polarizing film 4 allows 100% reflection of S polarized light and allows 100% transmission of P polarized light. A glass prism 5 has the upper surface in contact with the polarizing film 4 and is provided with a metallic reflection film 6 on the back surface. The quartz crystal prism 3 and the glass prism 5 have a common plane 13. An objective lens 7 is disposed on the optical path of the light which is emitted from a laser diode 1 and is reflected by the polarizing film 2. A photodiode 11 which receives the light from the quartz crystal prism 3 and a photodiode 12 which receives the light from the glass prism 5 are both disposed on a substrate 10. This substrate 10 is arranged parallel with a plane 13 which is common with the quartz crystal prism 3 and the glass prism 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical pickup for recording / reproducing information.

[0002]

2. Description of the Related Art Information is recorded by irradiating an optical information recording medium with light emitted from a laser light source, and light reflected from the recording medium is detected by a photodetector to reproduce or focus the information. Various types of magneto-optical pickups are known for detecting an error signal and a tracking error signal.

Japanese Unexamined Patent Publication No. 4-132034 discloses some examples of such a magneto-optical pickup. In the magneto-optical pickup shown in FIG. 1, a half mirror that reflects the light emitted from the semiconductor laser toward the objective lens is provided on one surface of the half-wave plate, and on the opposite surface thereof. A polarizing film for separating the reflected light from the magneto-optical disk is provided.

The light emitted from the semiconductor laser passes through the collimator lens to be a parallel light beam and enters the half mirror. The half mirror reflects a part (about half) of the incident light. The light reflected by the half mirror enters the objective lens and is condensed on the magneto-optical disk. The reflected light from the magneto-optical disk passes through the objective lens and becomes a parallel light beam,
The light enters the half mirror, and a part (about half) thereof passes through the half mirror and enters the half-wave plate. The light transmitted through the half mirror has its polarization plane rotated by 45 degrees while passing through the half-wave plate, and enters the polarizing film. The polarizing film reflects S-polarized light and transmits P-polarized light of the incident light.
The S-polarized light is applied to the light amount detecting element having two light receiving portions by the focusing lens. After the P-polarized light is reflected by the reflection mirror, it becomes focused light having astigmatism by the focusing lens and the cylindrical lens, and is irradiated on the light amount detecting element having four light receiving portions.

In this structure, the magneto-optical signal is obtained by the difference between the outputs of the above two light amount detecting elements. The track error signal is obtained by the push-pull method as the difference between the outputs of the two light receiving portions of the light amount detecting element that receives S-polarized light. The focus error signal is the sum of the outputs of the two light-receiving portions at the diagonal positions of the light amount detecting element receiving the P-polarized light and the sum of the outputs of the two light-receiving portions at the different diagonal positions by the astigmatic method. You get the difference.

[0006]

However, in the above-mentioned configuration, about half of the reflected light from the magneto-optical disk is reflected by the half mirror and is not used for information reproduction.
Such a situation is very unfavorable for obtaining a high quality signal.

Further, although a relatively small-sized magneto-optical pickup is realized by the above-mentioned structure, it is desired to further reduce the number of parts to achieve a smaller, lighter and cheaper magneto-optical pickup. . An object of the present invention is to provide a very small and lightweight magneto-optical pickup that can obtain a high quality signal.

[0008]

A magneto-optical pickup of the present invention has a first plane and a second plane which are parallel to each other,
A first prism that rotates the plane of polarization of light that traverses the interior along the optical path by 45 degrees, reflects S polarization at a predetermined ratio, and
The first polarizing film formed on the first plane of the first prism for transmitting polarized light at a rate of 100%, and the S polarized light of 10%
The second polarizing film formed on the second flat surface of the first prism that reflects 0% and transmits P polarized light at 100% is provided in contact with the second polarizing film. A second prism, a laser light source that emits divergent light toward the first polarizing film, an objective lens that collects the light reflected by the first polarizing film on a magneto-optical disk, A first photodetector that receives the first emitted light emitted from the prism and a second photodetector that receives the second emitted light emitted from the second prism are provided.

[0009]

The magneto-optical pickup of the present invention can be applied to both recording and reproducing. However, since the function when used for recording is included in the function when used for reproducing, the following mainly describes the case of reproducing. To do.

The light emitted from the laser light source is reflected by the first polarizing film except for a part thereof, enters the objective lens, and is condensed on the magneto-optical disk. In the case of recording, light is applied to the magneto-optical disk at a timing according to the information to be recorded. The direction of the magnetic pole of the magneto-optical disk changes only in the area irradiated with light. As a result, the information is recorded as binary information corresponding to the direction of the magnetic pole.

For reproduction, the magneto-optical disk is irradiated with linearly polarized light, that is, S-polarized light with respect to the first polarizing film. When the linearly polarized light is applied to the magneto-optical disk, the direction of the magnetic pole at that portion, that is, the binary information recorded,
The plane of polarization is rotated by the Kerr rotation angle in a predetermined direction.

The reflected light from the magneto-optical disk is linearly polarized light whose polarization plane is rotated in the direction corresponding to the recorded information, that is, linearly polarized light containing a P-polarized light component, which passes through the objective lens. It is incident on the first polarizing film. With respect to the light incident on the first polarizing film, the P-polarized light is transmitted therethrough, and the S-polarized light is reflected at a predetermined ratio. Thereby, the Kerr rotation angle of the light passing through the first polarizing film is apparently large.

The light passing through the first polarizing film has its plane of polarization rotated by 45 degrees before reaching the second polarizing film due to the optical characteristics of the first prism. The prism having such characteristics can be obtained by using a birefringent crystal or an optical rotatory crystal as a material and appropriately selecting the thickness thereof. Quartz is an example of such a material.

Of the light that has entered the second polarizing film, S-polarized light is reflected by the second polarizing film, propagates inside the first prism, and then exits from the first prism as the first exit light. And is incident on the first photodetector. On the other hand, the P-polarized light passes through the second polarizing film, enters the second prism, propagates inside the second prism, and then is emitted as second emitted light from the second prism. It is incident on the photodetector.

The reproduced signal is obtained, for example, as the difference between the output of the first photodetector and the output of the second photodetector. The track error signal is obtained by the push-pull method, for example.
In this case, the first photodetector or the second photodetector is composed of a light receiving element having two adjacent light receiving sections having a boundary parallel to the track direction. The track error signal is obtained as the difference between the outputs of the two light receiving parts.

The focus error signal is obtained, for example, by the beam size method. In this case, the first exit light and the first exit light are focused so that the first exit light has a focus behind the first photodetector and the second exit light has a focus before the second photodetector. The optical path length of the second emitted light is selected, and the outputs of the first detector and the second detector are set to be equal when the objective lens and the magneto-optical disk are in the in-focus positional relationship. The focus error signal is obtained as the difference between the output of the first photodetector and the second photodetector.

[0017]

Embodiments of the present invention will now be described with reference to the drawings. The structure of the magneto-optical pickup of the first embodiment is shown in FIGS. First, the configuration of this embodiment will be described with reference to FIGS. 1 and 3.

The crystal prism 3 has two planes parallel to each other, and the polarizing film 2 is formed on one of the planes and the polarizing film 4 is formed on the other plane. The crystal prism 3 rotates the polarization plane of the propagating light by 45 degrees before the light that has passed through the polarizing film 2 and propagates through the optical path shown in the figure to reach the polarizing film 4. It has a thickness. Polarizing film 2
Transmits S-polarized light at a ratio of 30% and P-polarized light at 100%.
It has the property of transmitting at a ratio of. The polarizing film 4 is S
It has the property of reflecting polarized light at a rate of 100% and transmitting P polarized light at a rate of 100%. Such a polarizing film 2
And the polarizing film 4 are made of, for example, TiO2 by a vacuum deposition method or the like.
It is realized by alternately laminating a plurality of thin films of SiO2 and SiO2. The desired polarization characteristics can be obtained by selecting the film thickness and the number of layers of the laminated thin films.

The glass prism 5 has two planes parallel to each other, one plane being in contact with the polarizing film 4, and the other plane being provided with a metal reflecting film 6. The crystal prism 3 and the glass prism 5 have a common plane 13 for emitting the light reflected by the polarizing film 4 and the light reflected by the metal reflecting film, respectively.

The laser diode 1 is arranged so that its emitted light enters the polarizing film 2 at a predetermined angle. The laser diode 1 is attached to the end surface of the substrate 10. The laser diode 1 emits divergent light that becomes S-polarized light to the polarizing film 2.

An objective lens 8 is provided on the optical path of the light emitted from the laser diode 1 and reflected by the polarizing film 2. The objective lens 8 condenses the light from the polarizing film 2 on the magneto-optical disk 8 and converts the divergent reflected light from the magneto-optical disk 8 into a converging light flux toward the polarizing film 2.

The photodiode 11 that receives the light emitted from the crystal prism 3 and the photodiode 12 that receives the light emitted from the glass prism 5 are
It is provided on the same side of. The substrate 10 is arranged such that the surface provided with the photodiodes 11 and 12 is parallel to a plane 13 common to the crystal prism 3 and the glass prism 5.

As shown in FIG. 3, the photodiode 11
Has three light receiving regions 11a to 11c arranged adjacent to each other,
The photodiode 12 has three light receiving regions 1 arranged side by side.
2a to 12c. When the objective lens 7 is at the in-focus position with respect to the magneto-optical disk 8, the spot 20 irradiated on the photodiode 11 and the photodiode 1
The spots 21 irradiated on the 2 are adjusted to have the same size.

Next, the operation of this embodiment will be described.
The magneto-optical pickup of this embodiment is used for both recording and reproduction, but the operation at the time of recording is the same as that at the time of reproduction except that the output of the laser diode is different. Therefore, the case of reproduction will be described below.

70% of the light (S polarized light) emitted from the laser diode 1 is reflected by the polarizing film 2, enters the objective lens 7, and is condensed on the magneto-optical disk 8. The linearly polarized light applied to the magneto-optical disk 8 has its plane of polarization rotated by the Kerr rotation angle in the direction of the magnetic pole of that portion, that is, in the direction according to the recorded binary information. Therefore, as shown by SH and SL in FIG. 2, the reflected light from the magneto-optical disk 8 is a straight line whose polarization plane is rotated by the Kerr rotation angle θk in the opposite direction according to the recorded information “H” and “L”. It becomes polarized light.

The reflected light from the magneto-optical disk 8 passes through the objective lens 7, becomes a converging light beam, and enters the polarizing film 2. The light incident on the polarizing film 2 is 10
Although 0% is transmitted, 70% of S-polarized light is reflected by the polarizing film 2 and 30% is transmitted through the polarizing film 2. Therefore, the light indicated by SH 'and SL' in FIG. 2 is incident on the quartz prism 3 in correspondence with each of SH and SL. Since the recorded information is reflected in the P-polarized light, there is no signal loss due to the polarizing film 2. As can be seen from FIG. 2, this is because the X component corresponding to the reproduction signal amplitude does not change and SH sin θk = SH's
This is because inθk '.

The light incident on the crystal prism 3 propagates through the crystal prism 3 and reaches the polarizing film 4, while its plane of polarization is 45 degrees.
Is rotated once. As a result, when it reaches the polarization plane 4,
The light corresponding to SH 'and the light corresponding to SL' have opposite ratios of P-polarized light and S-polarized light. Of course, the proportions of P-polarized light and S-polarized light are not equal.

Of the light incident on the polarizing film 4, S-polarized light is
It is reflected by the polarizing film 4, propagates inside the quartz prism 3,
The light is emitted from the flat surface 13 and is incident on the photodiode 11. The P-polarized light passes through the polarizing film 4, propagates inside the glass prism 5, is reflected by the metal reflecting film 6, and then is reflected on the flat surface 13.
And is incident on the photodiode 12. Since the polarization film 4 and the metal reflection film 6 are in a parallel relation,
The polarized light is emitted perpendicular to the plane 13 and parallel to it. Further, due to the difference in optical path length between P-polarized light and S-polarized light, S-polarized light has a focal point behind the photodiode 11, and P-polarized light has a focal point in front of the photodiode 12.

In this structure, the reproduction signal is obtained by the difference between the output of the photodiode 11 and the output of the photodiode 12. The track error signal is obtained by the push-pull method, for example, by the difference between the outputs of the two light receiving regions 11a and 11c of the photodiode 11. Alternatively, it can be obtained by the difference between the outputs of the two light receiving regions 12a and 12c of the photodiode 12. In order to obtain a highly reliable signal, it is desirable to consider both of them.

The focus error signal is obtained by the beam size method. When the objective lens 7 is in the in-focus position with respect to the magneto-optical disk 8, as shown in FIG. 3, the S-polarized spot 20 irradiated on the photodiode 11 and the P-polarized spot irradiated on the photodiode 12 are shown. 21 is adjusted to have the same size. Therefore,
When the magneto-optical disk 8 moves away from the objective lens 7, the spot 20 becomes smaller and the spot 21 becomes larger. On the contrary, the magneto-optical disk 8 is used for the objective lens 7
The spot 20 becomes larger and the spot 21
Becomes smaller. Therefore, the photodiodes 11 and 1
If the output of each light receiving area of No. 2 is described using the code indicating the light receiving area, the focus error signal is (11a + 11).
c + 12b)-(12a + 12c + 11b).

As described above, according to this embodiment, there is no loss of light reflecting information, and since only one objective lens is used, a compact and inexpensive magneto-optical pickup with high signal quality is provided. can get.

In the crystal prism 3, the crystal constituting the crystal is a crystal having birefringence and optical rotatory power. In the above-described embodiment, the function of the half-wave plate utilizing birefringence is used. Although the plane of polarization is rotated by 45 degrees, the plane of polarization may be rotated by utilizing the optical rotatory power. Further, the material of the prism 3 is not limited to quartz, and other materials may be used as long as they are birefringent crystals or optical rotatory crystals. As an example, TeO2, which is an optically active crystal, is given.

Next, the structure of the magneto-optical pickup of the second embodiment is shown in FIG. In the figure, the same members as in the first embodiment are designated by the same reference numerals. Regarding the light, only the optical path of the principal ray is shown, and the spread of the light flux is omitted.

In this embodiment, as shown in FIG. 4, the crystal prism 3 and the glass prism 5 are both parallel flat plates. The laser diode 1 is fixed to the supporting member 9, and the substrate 10 is attached to the supporting member 9.
The other structure is the same as that of the first embodiment.

The operation of this embodiment is the same as that of the first embodiment until the light from the magneto-optical disk 8 is separated by the polarizing film 4. The S-polarized light reflected by the polarizing film 4 is emitted from the upper surface of the crystal prism 3, passes through the polarizing film 2, and enters the photodiode 11. The P-polarized light transmitted through the polarizing film 4 enters the glass prism 5, is reflected by the metal reflection film 6 provided on the lower surface, is emitted from the upper surface of the glass prism 5, and is incident on the photodiode 12.
Various signals are obtained in the same manner as in the first embodiment. However, the light incident on the photodiode 11 is weakened when passing through the polarizing film 2, and therefore it is necessary to perform a calculation that corrects that amount.

The structure consisting of the crystal prism 3 and the glass prism 5 used in this embodiment is one before the flat surface 13 in the first embodiment (FIG. 1) is formed by polishing or the like. Therefore, the magneto-optical pickup equivalent to that of the first embodiment can be obtained at a lower cost.

Some modifications of the second embodiment will be described below. A magneto-optical pickup of the first modified example is shown in FIG. In this modification, the polarizing film 2 is formed not in the entire upper surface of the crystal prism 3 but in a partial region. The remaining area of the crystal prism 3 is P polarized light and S polarized light.
An antireflection film 13 that transmits 100% of both polarized light is formed. The position of the boundary between the polarizing film 2 and the antireflection film 13 is
The light emitted from the laser diode 1 is selected to enter the polarizing film 2, and the light reflected by the polarizing film 4 is emitted through the antireflection film 13. According to this modification, the light reflected by the polarizing film 4 passes through the antireflection film 13 and enters the photodiode 11. As a result, the photodiode 11 is irradiated with strong light without loss. Therefore,
The output of the photodiode 11 is good and does not need to be corrected, and various signals finally obtained are of high quality.

The magneto-optical pickup of the second modification is shown in FIG.
Shown in. In this modification, the crystal prism 3 and the glass prism 5 are formed with a flat surface 30 that obliquely crosses both. A photodiode 31 that receives the light emitted from the laser diode 1 and transmitted through the polarizing film 2 is arranged below the plane 30. In the magneto-optical pickup, the laser diode 1 is used when recording / reproducing information.
The output of is finely adjusted. Therefore, it is necessary to monitor the output of the laser diode 1. In this modified example, of the light emitted from the laser diode 1, which is transmitted through the polarizing film 2 and is not used for recording and reproduction,
Is emitted from the light source, enters the photodiode 31, and is monitored. As a result, the above-described object is achieved, and at the same time, it is prevented that the light used for recording / reproduction becomes stray light propagating in the prism and the signal quality is deteriorated.

The magneto-optical pickup of the third modification is shown in FIG.
Shown in. This modification is an example in which measures against stray light are taken by appropriately selecting the position of the end face of the substrate 10 and the position of the end of the prism. The laser diode 1 is close to a point light source, and its emitted light has a considerably large divergence angle. The divergence angle is about 30 degrees, although it varies depending on the characteristics of the objective lens, the arrangement of the optical elements, and the like in consideration of light actually used for recording and reproducing information. For example, if the diameter of the objective lens becomes large, all the light reflected by the polarizing film will be incident, so the problem of stray light does not occur, but it is desirable that the objective lens is small in terms of the structure of the magneto-optical pickup. Therefore, out of the light emitted from the laser diode, the outer beam, that is, 3
The beam deviating from 0 degrees is not incident on the objective lens. Furthermore, because of the characteristics of the polarizing film, 30% of the light emitted from the laser diode is transmitted to the crystal prism, so that the outside beam that does not enter the objective lens is also transmitted to the crystal prism. Since this transmitted light naturally does not include information from the magneto-optical disk,
When it enters the photodiodes 11 and 12, it is detected as noise.

In the figure, the ray 41 shows the principal ray of the light flux actually used, and the rays 42 and 43 show the outermost rays of the light actually used. That is, since the light rays outside the light rays 42 and 43 become stray light, it is desirable not to enter the prism. Ray 44
Lights 45 and 45 are lights further outside the light rays 42 and 43 and become stray light. Therefore, the position of the end face of the substrate 10 is adjusted so that the light beam 44 is reflected by the end face of the substrate 10 so as not to enter the crystal prism 3, and the position of the end face is adjusted so that the light beam 45 does not enter the crystal prism 3 and the glass prism 5. Has been adjusted. As a result, it is possible to prevent deterioration of the signal caused by unnecessary light entering the prism and becoming stray light.

The structure of the magneto-optical pickup of the third embodiment is shown in FIG. In the figure, the same members as those in the above-described embodiment are designated by the same reference numerals. Regarding the light, only the optical path of the principal ray is shown, and the spread of the light flux is omitted.

The basic structure of this embodiment is almost the same as that of the second embodiment, and different points will be described below. In this embodiment, a glass triangular prism 1 is provided on the polarizing film 2.
4 are provided. The light reflected by the polarizing film 4 is emitted from the end face of the crystal prism 3, and the light reflected by the metal reflection film 6 is emitted from the end face of the glass prism 5.

In this embodiment, the point where light is incident on the polarizing film 2 via the triangular prism 14 and the light incident on the photodiode 11 and the photodiode 12 are emitted from the end faces of the quartz prism 3 and the glass prism 5, respectively. The operation is the same as that of the second embodiment except that

In the structure of this embodiment, since the triangular prism 14 is provided on the polarizing film 2, the difference in the refractive index of the medium (crystal and glass) on both sides of the polarizing film 2 is different from that of the above-mentioned embodiment. Therefore, the number of thin film layers required to form the polarizing film 2 having desired characteristics can be reduced. Therefore, the polarizing film 2
The number of manufacturing steps is reduced, and a magneto-optical pickup equivalent to the above-mentioned embodiment can be obtained at a lower cost.

The structure of the magneto-optical pickup of the fourth embodiment is shown in FIG. In the figure, the same members as those in the above-described embodiment are designated by the same reference numerals. Regarding the light, only the optical path of the principal ray is shown, and the spread of the light flux is omitted. The objective lens and the magneto-optical disk are omitted.

The structure of this embodiment is basically the same as that of the third embodiment, although the shapes of the quartz prism 3 and the glass prism 5 are different. Alternatively, it may be said that the triangular prism 14 is provided on the polarizing film 2 in the first embodiment (see FIG. 1).

As shown in FIG. 9, a glass triangular prism 14 is provided on the polarizing film 2. The triangular prism 1 on which the light emitted from the laser diode 1 is incident
4, the end face 16 of the crystal prism 3 through which the light reflected by the polarizing film 4 passes, and the end face 18 of the glass prism 5 through which the light reflected by the metal reflection film 6 passes form the same plane. There is. The laser diode 1 is attached to the support member 9 via the attachment member 15.

In this embodiment, as in the third embodiment, since the triangular prism 14 is provided on the polarizing film 2, the difference in the refractive index between the media (crystal and glass) on both sides of the polarizing film 2 is different. Since it is smaller than that of the above-mentioned embodiment, the polarizing film 2 having desired characteristics is obtained.
The number of thin film layers required to form the film is small.

Further, the end face 16 of the triangular prism 14, the end face 17 of the crystal prism 3 and the end face 18 of the glass prism 5 are flush with each other. This allows the direction of the optical axis of the light passing through the prism to be set accurately. The three end faces 16, 17 and 18 can be easily made in the same plane by laminating the triangular prism 14, the crystal prism 3 and the glass prism 5 and then polishing them. This can be understood from the advantage that the plane 13 must be formed at a predetermined angle with respect to the polarizing film 2 in the first embodiment.

In this embodiment, since the assembling and processing can be easily performed with high accuracy, the magneto-optical pickup equivalent to the above-mentioned embodiment can be obtained at a lower cost. A modification of the fourth embodiment is shown in FIG. In this modification, as shown in FIG. 10, a photodiode 31 that receives the light emitted from the laser diode 1 and transmitted through the polarizing film 2 is provided. As mentioned in the description of the second modification of the second embodiment, in the magneto-optical pickup, it is necessary to finely adjust the output of the laser diode 1 when recording / reproducing information. It is necessary to monitor the output of 1. According to the configuration of FIG. 10, the output of the laser diode 1 can be known based on the output of the photodiode 31, and the output can be adjusted.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist of the invention.

The summary of the present invention can be summarized as follows. (1) (corresponds to the configuration of FIG. 1 and FIGS. 4 to 10) Information is recorded by irradiating the optical information recording medium with light emitted from a laser light source through an objective lens and recording from the recording medium. A magneto-optical pickup that reproduces information and detects a focus error signal and a tracking error signal by detecting reflected light with a photodetector.It has a first plane and a second plane that are parallel to each other and is along the optical path. The polarization plane of the light that traverses the interior by 45
A first prism that rotates by a degree, a first polarizing film formed on a first plane of the first prism that reflects S polarized light at a predetermined ratio and transmits P polarized light at a ratio of 100%, S
Provided in contact with the second polarizing film formed on the second flat surface of the first prism, which reflects polarized light at 100% and transmits P polarized light at 100%. Second prism, a laser light source that emits divergent light toward the first polarizing film, an objective lens that collects the light reflected by the first polarizing film onto a magneto-optical disk, It is provided with a first photodetector for receiving the first emitted light emitted from the one prism and a second photodetector for receiving the second emitted light emitted from the second prism. Magneto-optical pickup.

When the light from the magneto-optical disk passes through the first polarizing film, the P-polarized light reflecting the recorded information is 10
Since it transmits 0%, there is no loss of signal light. Further, when passing through the first polarizing film, S-polarized light irrelevant to the recorded information is reduced, so that the apparent Kerr rotation angle is increased. As a result, a magneto-optical pickup capable of obtaining a high quality signal can be obtained.

(2) (corresponds to the configuration of FIG. 1 and FIGS. 4 to 10) In the above item (1), the second prism has a first plane and a second plane which are parallel to each other. The first flat surface of the prism of is in contact with the second polarizing film, and the magneto-optical pickup further includes a reflection mirror provided on the second flat surface of the second prism. And the second emitted light is emitted in parallel to the magneto-optical pickup.

(3) (corresponds to the configuration of FIG. 1 and FIGS. 4 to 10) In the above item (2), the first photodetector and the second photodetector are arranged on the same plane, As a result, the first emitted light has a focus behind the first photodetector and the second emitted light has a focus before the second photodetector.

With this configuration, the focus error signal can be obtained by the beam size method. (4) (corresponds to the configurations of FIGS. 1, 9, and 10) In the above (3), the first prism has a third plane that intersects the first plane and the second plane. The second prism has a third plane transverse to the first plane, and the third plane of the first prism and the third plane of the second prism are the first photodetector and the third plane. In the same plane, which is in a positional relationship parallel to the plane where the two photodetectors are located, the first emission light is emitted vertically from the third plane of the first prism, and the second emission A magneto-optical pickup in which light is emitted vertically from the third plane of the second prism.

(5) (corresponds to the configurations of FIGS. 9 and 10) The magneto-optical pickup according to the above (4), further including a triangular prism provided in contact with the first polarizing film.

With this structure, the difference in the refractive index between the media on both sides of the first polarizing film becomes small, so that the number of thin film layers constituting the first polarizing film can be small and the manufacturing cost can be kept low. it can.

(6) (corresponds to the configurations of FIGS. 9 and 10) In the above item (5), the light emitted from the laser light source is incident perpendicularly on the incident surface of the triangular prism, and the incident surface of the triangular prism is A magneto-optical pickup located on a plane formed by the third plane of the first prism and the third plane of the second prism.

Since the third plane of the first prism, the third plane of the second prism, and the entrance surface of the triangular prism are on the same plane, it is easy to design the optical system. Further, forming the end faces of a plurality of prisms on the same plane is easier than forming them at a predetermined angle, and the manufacturing cost is low.

(7) (corresponds to the configuration of FIG. 10) In the above item (6), a third photodetector for receiving the light emitted from the laser light source and transmitted through the first polarizing film is further provided. Magneto-optical pickup provided.

By monitoring the output of the third photodetector, the output of the laser light source can be known and the output can be finely adjusted. (8) (corresponds to the configuration of FIGS. 4 to 8) In the above item (3), the first plane of the second prism is
A magneto-optical pickup part of which is in contact with the second polarizing film.

(9) (corresponds to the configuration of FIGS. 4 to 7) In the above item (8), the first emitted light is emitted from the first plane of the first prism, and the second emitted light is A magneto-optical pickup which is emitted from the first plane of the second prism in a portion not in contact with the second polarizing film.

Since it is not necessary to newly process the exit surfaces from which the first exit light and the second exit light are emitted into the first prism and the second prism, respectively, the manufacturing cost can be kept low.

(10) (corresponds to the configuration of FIG. 5) In the above item (9), the first polarizing film is provided on a part of the first plane of the first prism, and Is
A magneto-optical pickup which is emitted from the first plane of the first prism in the portion where the first polarizing film is not provided.

Since the first emitted light does not pass through the first polarizing film, the loss of light incident on the first photodetector is reduced. (11) (corresponds to the configuration of FIG. 5) In the above item (10), an antireflection film provided in contact with the first plane of the first prism in the portion where the first polarizing film is not provided is further added. Magneto-optical pickup provided.

Since the reflection of the first emitted light on the first plane of the first prism is prevented by the antireflection film, the loss of light incident on the first photodetector is further reduced. (12) (corresponds to the configuration of FIG. 6) In the above item (9), further includes a third photodetector for receiving the light transmitted through the first polarizing film among the light emitted from the laser light source. Magneto-optical pickup.

By monitoring the output of the third photodetector, the output of the laser light source can be known and the output can be finely adjusted. (13) (corresponds to the configuration of FIG. 7) In the above item (9), means for limiting the spread of the light emitted from the laser light source is provided so that the light not incident on the objective lens is not incident on the first prism in advance. A magneto-optical pickup in which the position of the end of the first prism with respect to the laser light source is selected.

With this configuration, stray light in the prism is reduced, so that a higher quality signal can be obtained. (14) (corresponds to the configuration of FIG. 8) The magneto-optical pickup according to the above (9), further including a triangular prism provided in contact with the first polarizing film.

With this structure, the difference in refractive index between the media on both sides of the first polarizing film is reduced, so that the number of thin film layers constituting the first polarizing film can be small and the manufacturing cost can be kept low. it can.

(15) (corresponds to the configuration of FIG. 8) In the above item (14), the first prism has a third plane that intersects the first plane and the second plane, and Is emitted from the third plane of the first prism, the second prism has a third plane that intersects the first plane and the second plane, and the second emitted light is the second plane of the second prism. A magneto-optical pickup emitted from three planes. Since the first emitted light does not pass through the first polarizing film, the loss of light incident on the first photodetector is small.

[0072]

According to the present invention, a very small and lightweight magneto-optical pickup capable of obtaining a high quality signal is provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a magneto-optical pickup according to a first embodiment of the present invention.

FIG. 2 is a view for explaining the action of a polarizing film formed on the upper surface of the quartz prism shown in FIG.

FIG. 3 is a diagram showing a configuration of a photodiode shown in FIG.

FIG. 4 is a diagram showing a configuration of a magneto-optical pickup according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a first modification of the magneto-optical pickup according to the second embodiment of the present invention.

FIG. 6 is a diagram showing a second modification of the magneto-optical pickup according to the second embodiment of the present invention.

FIG. 7 is a diagram showing a third modification of the magneto-optical pickup according to the second embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a magneto-optical pickup according to a third embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a magneto-optical pickup according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a modification of the magneto-optical pickup according to the fourth embodiment of the present invention.

[Explanation of symbols]

1 ... Laser diode, 2 ... Polarizing film, 3 ... Quartz prism, 4 ... Polarizing film, 5 ... Glass prism, 7 ... Objective lens, 11 and 12 ... Photodiode.

Claims (1)

[Claims] 1. Information is recorded by irradiating an optical information recording medium with light emitted from a laser light source through an objective lens, and information reflected by the light is detected by a photodetector. A magneto-optical pickup that performs reproduction and detection of a focus error signal and a tracking error signal, has a first plane and a second plane that are parallel to each other, and rotates the polarization plane of light that traverses the interior along the optical path by 45 degrees. A first prism, a first polarizing film formed on the first plane of the first prism that reflects S-polarized light at a predetermined ratio, and transmits P-polarized light at a ratio of 100%; A second polarizing film formed on the second plane of the first prism that reflects 100% of the light and transmits P polarized light at the ratio of 100%, and is provided in contact with the second polarizing film. The second prism, the laser light source that emits divergent light toward the first polarizing film, the objective lens that focuses the light reflected by the first polarizing film on the magneto-optical disk, and the first prism Magneto-optical pickup including a first photodetector for receiving the first emitted light emitted from the second photodetector and a second photodetector for receiving the second emitted light emitted from the second prism .