JPH05174415A - Optical pickup device - Google Patents

Abstract

PURPOSE:To provide a holding tool for two transparent p1lates which are used to an optical pickup device. CONSTITUTION:A holding block 40 has a 1st through hole 41 through which the incident light passes and 2nd through holes 42 and 43 which are approximately orthogonal to the hole 41. These holes 41-43 have openings 44a and 45a on the slant holding surfaces 44 and 45 formed on the end faces of the block 40 respectively. Then the transparent plates 14 and 15 are fixed to the surfaces 44 and 45 respectively. A part of the incident light is reflected on the plate 15 and made incident on a photodetector. Meanwhile the stray light reflected on the plate 15 in the direction opposite to the photodetector is led to the outside through the hole 43. Thus it is possible to prevent the stray light from being reflected on the inner wall surface of the through hole 41 and then made incident on the photodetector as a noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for recording / reproducing information on / from an optical recording medium.

In the present invention, the optical recording medium includes not only an optical recording medium such as an optical disc and an optical card, but also a magneto-optical recording medium such as a magneto-optical disc and a magneto-optical card.

In the present invention, recording / reproducing information includes recording information on an optical recording medium, reproducing information recorded on the optical recording medium, and recording and reproducing.

[0004]

2. Description of the Related Art A conventional optical pickup device is a first optical system for collimating the divergent light from a semiconductor laser, collecting the collimated light on an optical recording medium, and reflecting the light from the optical recording medium. A second optical system for collimating the light, a first polarization beam splitter for polarization separating the reflected light collimated by the second optical system,
A second polarization beam splitter for further separating the polarization-separated light into tracking control light and focusing control light, and further separating the separated light on the light receiving surface of the tracking control photodetector. A third optical system for collecting the separated light, a fourth optical system for collecting the separated light on the light receiving surface of the focusing control photodetector, a third optical system or a fourth optical system for reading a read signal. It is composed of a fifth optical system and the like for guiding light to a photodetector for obtaining.

Since such a conventional optical pickup device uses many optical components, its weight is large,
Therefore, there is a problem that the access time is slow.
In addition, since many optical components are used, the cost of the components is high, and the assembly and adjustment of the components are troublesome and time-consuming, and the final cost is also high from this point.

[0006] Therefore, the applicant has made a great reduction in size and weight,
We have proposed an optical pickup device that can reduce costs.

[0007]

[Explanation of prior invention] First prior invention (Japanese Patent Application No. 3-21047)
8) is an optical pickup device comprising a light emitting element and a converging optical system for converging divergent light emitted from the light emitting element on an optical recording medium and condensing reflected light from the optical recording medium. Arranged on the optical path of the divergent light between the light emitting element and the condensing optical system, inclined with respect to the optical axis of the condensing optical system, and transmitting a part of incident light and partly At least two transparent plates (for example, dielectric plates) that reflect light, and among the light reflected by the optical recording medium and condensed by the condensing optical system, transmitted through the transparent plates or reflected by the transparent plates. It is characterized by comprising at least two photodetectors for receiving the emitted light.

The divergent light emitted from the light emitting element is condensed on the optical recording medium by the condensing optical system. The reflected light from the optical recording medium is condensed by the condensing optical system, a part of which is transmitted through the transparent plate or reflected by the transparent plate and is received by at least two photodetectors. A tracking error signal and a focusing error signal are obtained from the at least two photodetectors. In the case of reproduction, an information read signal is obtained based on the output signal of one or both of the at least two detectors. When the optical recording medium is a magneto-optical recording medium, an analyzer having polarization directions different from each other by 90 degrees is placed in front of the at least two photodetectors, and the polarization plane rotation angle of the reflected light is detected by the recorded information. To be done.

According to the first prior invention, an optical pickup device having a minimum required optical structure is realized by disposing at least two transparent plates between the light emitting element and the condensing optical system. Therefore, it is possible to reduce its size and weight.

The essential optical components in the optical pickup device of the first prior invention are a light emitting element, a condensing optical system, a transparent plate and a photodetector, and in the case of a magneto-optical recording medium, an analyzer is attached thereto. Since it is sufficient to provide it, it is possible to significantly reduce the cost.

The second prior invention (Japanese Patent Application No. 3-210479) is
An optical pickup device comprising a light emitting element and a converging optical system for converging divergent light emitted from the light emitting element on a magneto-optical recording medium and condensing reflected light from the magneto-optical recording medium Is arranged on the optical path of the divergent light between the light collecting optical system and the light collecting optical system at an angle with respect to the optical axis of the light collecting optical system, and transmits at least part of the incident light and reflects at least part of the incident light. A set of two transparent plates (for example, a dielectric plate) and at least two of the light reflected by the magneto-optical recording medium and condensed by the condensing optical system, which are reflected by the transparent plate. A pair of transparent plates, each of which is provided with one photodetector, is arranged such that line segments generated by a plane perpendicular to the optical axis intersecting these transparent plates are inclined in directions substantially orthogonal to each other. Characterize.

[0012] Preferably, the inclination angle of the transparent plate is set to a Brewster angle at which a polarization component having a specific polarization plane is completely transmitted.

If necessary, an analyzer having polarization directions different from each other by 90 ° is arranged in front of the photodetector.

The divergent light emitted from the light emitting element is focused on the magneto-optical recording medium by the focusing optical system. The reflected light from the magneto-optical recording medium is condensed by the condensing optical system, a part of which is reflected by the transparent plate and received by at least two photodetectors.

The information recorded on the magneto-optical recording medium is read by detecting the change (Kerr effect) in the rotation angle of the polarization plane of the reflected light from the magneto-optical recording medium.

When light is obliquely incident on one surface of the transparent plate, its reflectance and transmittance have polarization plane selectivity, and the reflectance of light of a specific polarization component is 0% and the transmittance is 100%. There is an incident angle (Brewster angle).

By setting the inclination directions of the two transparent plates as described above, the reflected light of the two transparent plates can contain only or a large amount of polarization components orthogonal to each other.

Therefore, without using the above-mentioned analyzer, or by using it in an auxiliary manner, the above-mentioned photodetector detects the optical components contained in the reflected light from the magneto-optical recording medium and having mutually orthogonal polarization planes. Therefore, the read signal of information can be created based on the output signals of the two photodetectors.

A tracking error signal and a focusing error signal can be obtained from at least two photodetectors.

According to the second prior invention, an optical pickup device having a minimum required optical structure is realized by disposing at least two transparent plates between the light emitting element and the condensing optical system. Therefore, it is possible to reduce its size and weight.

The essential optical parts in the optical pickup device of the second prior invention are a light emitting element, a condensing optical system, a transparent plate and a photodetector. The cost can be reduced.

[0022]

In the first and second prior inventions, at least two transparent plates are used, and these transparent plates must be properly positioned and fixed. The same applies to the assembly and positioning of lenses and the like that form the condensing optical system. There is also a problem that when the transparent plate, the lens and the like are fixed to an appropriate holding member, the thin transparent plate may bend due to the difference in thermal expansion coefficient between them.

An object of the present invention is to provide an appropriate holder or holding block for a transparent plate and a lens in the optical pickup device according to the first and second prior inventions described above.

[0024]

The holder according to the first invention has a holding block, a first through hole through which incident light passes is formed in this holding block, and the first and second end faces of the holding block have first and second through holes. A holding surface is formed obliquely with respect to the through hole, a first through hole is opened in the holding surface, and a second opening is opened in the holding surface, and the reflected light from the transparent plate fixed to the holding surface is passed therethrough.
Through holes are formed.

A transparent plate is fixed to the holding surface.

The light emitted from the light emitting element or the light condensed by the condensing optical system enters the first through hole of the holder as incident light. The reflected light from the transparent plate fixed to the holding surface enters the photodetector directly or through the second through hole.

The second through hole formed in the holder has either a first function of guiding the reflected light from the transparent plate to the photodetector or a second function of letting the reflected light from the transparent plate escape to the outside. Make up In particular, the second action is that, of the light reflected from the transparent plate, the light traveling in the direction opposite to the photodetector is reflected on the inner surface of the holding block, returns to the transparent plate again, passes through the transparent plate as it is, and passes through the photodetector. It is important to prevent noise from being incident on.

Preferably, the holding block and the transparent plate are made of the same material or materials having substantially the same coefficient of thermal expansion.

In a preferred embodiment of the first invention, the transparent plate is provided at one location (one side or part of one side of the transparent plate).
Only in the case of (1) and (2) are fixed to the holder by being bonded to the holding surface of the holder using an adhesive.

When the holding block and the transparent plate have different coefficients of thermal expansion, if the transparent plate is adhered to the holding block over the entire circumference, the transparent plate may be bent due to a change in ambient temperature.

If the transparent plate is fixed to the holding block only at one position, the transparent plate will be heated independently of the holding block even if the transparent plate and the holding block have different thermal expansion coefficients and the ambient temperature changes. It is possible to prevent the occurrence of flexure by expanding and contracting.

The adhesive may also expand and contract due to changes in ambient temperature. When the adhesive expands and contracts by heat, the transparent plate is displaced in the direction away from the holding surface of the holder (the part fixed by the adhesive does not move, but the transparent plate moves most at this fixed point and the part on the reflection side) )there is a possibility. Even if the transparent plate is slightly displaced, the spot light on the light receiving surface of the photodetector formed by the reflected light of the transparent plate also changes to the light receiving surface.

In a further preferred embodiment of the first aspect of the invention, the transparent plate is formed on the light receiving surface of the photodetector of the reflected light from the transparent plate caused by the displacement of the transparent plate due to the thermal expansion and contraction of the adhesive. The fixed point of the transparent plate is determined so that the moving direction of the spot light and the displacement direction of the spot light caused by the tracking error are orthogonal to each other on the light receiving surface.

As a result, even if the reflected light spot is slightly displaced on the light receiving surface due to displacement of the transparent plate due to thermal expansion and contraction of the adhesive, the direction of this displacement is caused by tracking error. Since it is orthogonal to the displacement direction of the reflected light spot, it has no effect on the tracking error signal. Therefore, an accurate tracking error signal can always be obtained.

In the holder according to the second invention, at least two of at least two transparent plates and lenses used in the above optical pickup device are integrally formed with the holder.

In a preferred embodiment of the second invention,
The holder is composed of a frame having the transparent plate or the lens as an end surface or a cut surface.

According to the second invention, since the transparent plate and the lens used in the optical pickup device are integrally formed with the holder, the assembly and the adjustment are very easy.
It also has excellent environmental resistance.

The holding block according to the third invention holds at least two transparent plates and two photodetectors in the above-mentioned prior invention, and is movably arranged in the optical axis direction of the condensing optical system. Is what

Preferably, the holding block is also provided with a photodetector for receiving the light emitted from the light emitting element and reflected by the transparent plate and outputting a signal for controlling the light emission intensity of the light emitting element.

According to the third aspect of the invention, at least two transparent plates and two photodetectors are fixed to the holding block in advance, so that the entire holding block is used as a condensing optical system in the assembly and adjustment of the optical pickup device. It is sufficient to move and position in the optical axis direction. It is not necessary to separately move the two photodetectors in the direction orthogonal to the optical axis to perform focusing adjustment, and the focusing adjustment of the spot formed on the photodetector can also be achieved by fine adjustment of the entire holding block.

[0041]

EXAMPLES First, the invention of the prior application will be described. An example of the second prior invention will be described as a representative example of the prior invention.

1 and 2 show an embodiment of the second prior invention.

The optical pickup device includes a semiconductor laser 11
And a condensing optical system for converging the divergent light emitted from the semiconductor laser 11 on the magneto-optical disk 20. The condensing optical system is a collimating lens that collimates divergent light.
It includes an objective lens 13 for condensing the collimated light.

On the optical path of the divergent light between the semiconductor laser 11 and the collimating lens 12, two glass plates 14 and
15 is arranged in a state of being inclined with respect to the optical axes of the semiconductor laser 11 and the focusing optical system.

The divergent light emitted from the semiconductor laser 11 passes through the two glass plates 14 and 15 and is focused on the magneto-optical disk 20 by the focusing optical system. A part of the divergent light emitted from the semiconductor laser 11 is reflected by the glass plate 14 and is detected by the photodetector.
Received by 23. The emitted light intensity of the semiconductor laser 11 is controlled based on the light reception signal of the photodetector 23.

The reflected light from the magneto-optical disk 20 is condensed by the condensing optical system. A part of the condensed reflected light is reflected by the glass plate 15 and is incident on the photodetector 22, and a part of the light transmitted through the glass plate 15 is further reflected by the glass plate 14 and is detected by the photodetector 21. Incident on.

Since the reflected light from the magneto-optical disk 20 is condensed by the condensing optical system, the glass plate 15 and the photodetector 22
It is not always necessary to provide a condenser lens or the like between the glass plate 14 and the photodetector 21.

FIG. 3 shows the incident angle dependence of the reflection coefficient and the transmission coefficient of light when the light obliquely enters the surface of the glass plate (refractive index = 1.5).

T _p is the transmission coefficient of the P polarization component, T _s is the transmission coefficient of the S polarization component, R _p is the reflection coefficient of the P polarization component, R _s
Is the reflection coefficient of the S-polarized component. The component parallel to the glass surface is the S-polarized component, and the vertical component is the P-polarized component.

As can be seen from FIG. 3, at a certain angle α _B (this is called Brewster's angle), R _p becomes 0% and T _p becomes 100%. At this time, R _s and T _s take values other than 0 or 100%.

Therefore, if the glass plate is tilted with respect to the incident light at the Brewster angle α _B , the reflected light from the glass plate will be only the S-polarized component. Even if the inclination angle of the glass plate is other than Brewster's angle, the reflected light from the glass plate contains more S-polarized component than P-polarized component.

The glass plates 14 and 15 are arranged such that the line segments formed by intersecting the planes perpendicular to the optical axis of the condensing optical system with these glass plates 14 and 15 are orthogonal to each other,
Moreover, if the incident angle of the reflected light condensed by the condensing optical system is tilted so as to be the Brewster angle, the glass plate 14
The reflected light from 15 and 15 contains only polarization components orthogonal to each other, and only these lights are detected by photodetectors 21 and 22.
Respectively detected by.

Even if the inclination angles of the glass plates 14 and 15 with respect to the incident light are other than the Brewster angle, the glass plates 14 and 15 are
The reflected light from 1 contains more polarization components orthogonal to each other. By disposing analyzers 31 and 32 arranged such that their polarization directions are orthogonal to each other so that only these orthogonal polarization components pass respectively, the polarization components orthogonal to each other are provided. Only are detected by photodetectors 21 and 22, respectively.

The polarization directions of the linearly polarized light emitted from the semiconductor laser 11 are orthogonal to each other (the analyzer 31,
The polarization direction of the light passing through 32) and the angle of 45 degrees.

With the above configuration, the change in the polarization plane rotation angle caused by the information recorded on the magneto-optical disk 20 is detected by the difference between the output signals of the photodetectors 21 and 22.

It goes without saying that a polarizer may be provided on the front surface of the semiconductor laser 11.

The output signals of the photodetectors 21 and 22 are also used for producing the focusing error signal and the tracking error signal.

The focusing error signal is created by, for example, the beam size method or the astigmatism method. In the double beam size method, the photodetectors 21 and 22 are arranged at positions before and after the focal position of the reflected light when the focusing is performed correctly (see FIG. 2).
As shown). The photodetectors 21 and 22 are provided so that a signal representative of the size of the light beam received is obtained.
21 and 22 are formed, and the focusing error signal is created by taking the difference between the output signals of the photodetectors 21 and 22. Each of the photodetectors 21 and 22 includes, for example, a three-divided photodiode, and the difference between the output signal of the central photodiode and the sum signal of the output signals of the photodiodes on both sides becomes the output signal of the photodetector.

Aberrations including astigmatism occur in the reflected light of the glass plate arranged obliquely with respect to the optical axis. By utilizing this astigmatism, a focusing error signal based on the astigmatism method can be obtained. For example, one of the photodetectors 21 and 22 is composed of a four-division photodiode, and a focusing error signal is generated by adding and subtracting the output signals of these four photodiodes.

For example, the push-pull method is used to create the tracking error signal. That is, the photodetector
21 or 22 is configured to include a photodiode divided into two or three in the direction perpendicular to the track direction of the magneto-optical disk 20, and the difference signal between the output signals of the photodiodes at both ends serves as a tracking error signal.

If necessary, arrange three or more glass plates,
Focusing error detection for each glass plate,
A photodetector for tracking / error detection or the like may be provided.

The reflectance and the transmittance of the glass plate are appropriately adjusted in advance as needed. In this adjustment, at least one surface of the glass plate may be coated with a non-reflective coating, a semi-mirror surface coating, or the like. The antireflection coating is particularly useful when it is necessary to obtain the reflected light from only one of the two surfaces of the glass plate.

If necessary, the thickness of the glass plate
On the magneto-optical disk 20, the thickness is made thin (for example, about 100 μm or less) so that the influence of wavefront aberration can be ignored.
Alternatively, the shape of the collimator lens 12 or the like may be a shape (for example, an aspherical surface or an asymmetrical lens) in which the light spot formed on the magneto-optical disk 20 is hardly affected by the wavefront aberration.

Further, between the semiconductor laser 11 and the collimating lens 12 of the condensing optical system, a light beam shaping optical system for correcting the light of the elliptical cross section emitted from the semiconductor laser 11 into the light of the circular cross section is provided. You can also In addition, semiconductor laser 11
The emitted light of the semiconductor laser 11 passes between the glass plate 14 and the glass plate 14, and the semiconductor laser 11 emits the reflected light from the magneto-optical disk 20.
An isolator optical system may be provided to prevent the light from entering the device. If necessary, a condensing optical system can be provided between the glass plate and the photodetector.

4 and 5 show an example of a holder for holding the glass plates 14 and 15 used in the above-mentioned optical pickup device. FIG. 4 is a perspective view, and the viewing direction is slightly different from that in FIG. 5 is a plan view seen from the direction of arrow A in FIG.

The holder has a holding block 40. The holding block 40 has a shape in which the end surface of the rectangular parallelepiped is cut obliquely according to the arrangement angle of the glass plates 14 and 15. The longitudinal direction of the holding block 40 coincides with the optical axis direction of the optical system shown in FIGS. The holding block 40 is preferably a glass plate 1.
It is made of a material that has a coefficient of thermal expansion approximately equal to that of 4, 15 or the same material.

The glass plates 14 and 15 are fixed to the end surfaces (holding surfaces) 44 and 45 of the holding block 40, which are cut into inclined surfaces, by an adhesive, for example. The holding surfaces 44 and 45 are formed such that the line segments formed by intersecting the surfaces perpendicular to the optical axis with the holding surfaces 44 and 45 are orthogonal to each other.

Preferably, the glass plates 14, 15 are holding surfaces 44,
It is bonded to 45 only at one part (one place or one point). Hatching F4 and F5 respectively show an example of an adhesion part. In this way, the glass plates 14 and 15 are adhered to each other only at one location, so that the holding block 40 and the glass plates 14 and 15 have different thermal expansion coefficients and even if the ambient temperature changes. The deformation (deflection, etc.) of 15 is prevented in advance.

A first through hole 41 is formed through the center of the holding block 40 in the longitudinal direction thereof. The through-hole 41 has openings 44a and 45 on the holding surfaces 44 and 45 at both ends thereof.
a. The divergent light from the semiconductor laser 11 and the reflected light from the magneto-optical disk 20 condensed by the condensing optical system pass through the first through hole 41.

The second through holes 42 and 43 are formed in the directions substantially orthogonal to the through holes 41, respectively.
These through holes 42, 43 also open into the holding surfaces 44, 45, respectively.

The light L1 reflected from the magneto-optical disk 20 and being condensed by the condensing optical system enters the glass plate 15 as described above. A part L2 of this incident light is reflected by the glass plate 15 and goes to the photodetector 22. The other part of the light L4 passes through the glass plate 15, passes through the inside of the first through hole 41, and enters the glass plate 14. Of the reflected light from the glass plate 15, the light traveling in the direction opposite to the photodetector 22 (this is called stray light) L3
Is guided to the outside through the second through hole 43. If the second through hole 43 does not exist, the stray light L3 is generated by the first through hole 41.
The light is reflected by the inner wall surface of, and a part of it is incident on the photodetector 22 through the glass plate 15 and becomes a noise source. Since the second through hole 43 is provided, such noise is prevented from occurring.

A part of the light L4 traveling toward the glass plate 14 through the inside of the first through hole 41 is reflected by the glass plate 14, and the second through hole 42 is formed.
And goes to the photodetector 21.

The points F4 and F5 for fixing the glass plates 14 and 15 with an adhesive are preferably determined in consideration of the following points.
The fixing point F5 of the glass plate 15 will be described with reference to FIG.

As described above, a part of the reflected light from the magneto-optical disk 20 is reflected by the glass plate 15 and enters the photodetector 22. The photodetector 22 is composed of, for example, three-divided photodiodes 22a, 22b, and 22c. The difference between the output signals of the photodiodes 22a and 22c is calculated by the subtractor 24 to create a tracking error signal.
The focusing error signal can also be created by using the output signal of the three-division photodiode as described above.

The direction of the dividing line of the three-divided photodiodes 22a to 22c coincides with the track direction of the magneto-optical disk 20. Therefore, when a tracking error occurs, the reflected light spot on the light receiving surface of these photodiodes moves in the direction orthogonal to the dividing line (the direction indicated by arrow E).

On the other hand, the glass plate 15 is fixed to the holding surface 45 of the holding block 40 with an adhesive at a point F5.
The adhesive also expands and contracts due to changes in ambient temperature. Due to the thermal expansion and contraction of the adhesive, the glass plate 15 is displaced about the adhesion point F5 in the direction away from the holding surface 45 or approaching the holding surface 45 as indicated by arrow C. Due to such displacement of the glass plate 15, the photodiode of the photodetector 22
The reflected light spots formed on the light receiving surfaces of 22a to 22c also move.

The displacement direction of the reflected light spot caused by the displacement of the glass plate 15 caused by the thermal expansion and contraction of the adhesive is indicated by the arrow D.
As shown by, the adhesion point F5 is determined so as to coincide with the direction of the dividing line of the photodiodes 22a to 22c. By doing so, even if the reflected light spot is displaced in the direction of the arrow D, if the displacement is within the range of the light receiving surfaces of the photodiodes 22a to 22c, the tracking error signal is not affected at all. Become. The adhesion point F4 of the glass plate 14 may be similarly set.

FIG. 7 shows another embodiment of the holder.

In this embodiment, a transparent plate (corresponding to a glass plate)
15 and collimating lens 12 are integrally formed with the retainer. More specifically, the transparent plate 15 and the lens 12 are integrally formed as a part of the frame 50 of the holder. Such a holder can be made of, for example, plastic.

FIG. 8 shows still another example of the holder, in which the two transparent plates 14 and 15 and the lens 12 are integrally formed as an end surface of the frame 50 of the holder or as a plate.

When such a holder is used, the mutual positional relationship of the transparent plate, the lens, etc. is fixed and fixed.
The holder may be positioned with respect to the semiconductor laser 11 and the like, and the assembling and adjustment are easy, and the mutual deviation due to the temperature change is small and the environment resistance is excellent.

By removing the portion of the lens 12 in FIG. 8, a holder in which the two transparent plates 14 and 15 are integrated is realized. 7 and 8, the portion where the lens 12 is provided may be a flat surface, and the separately formed lens 12 may be bonded to this flat surface.

FIG. 9 shows another embodiment of the holding block.

The holding block 60 is a cylinder or a square tube,
The glass plate 1 is attached to the interior of the glass plate 1 through mounting members 61 and 62, respectively.
4 and 15 are retained. Further, the photodetectors 21, 22, and 23 are fixed to the peripheral surface of the holding block 60. Analyzers 31 and 32 are attached to the front surfaces of the photodetectors 21 and 22, respectively. Such a holding block 60 is movably supported in the optical axis direction of the optical system as shown by an arrow B in FIG.

In the holding block 60, the glass plates 14,
The positions of 15 and the photodetectors 21 to 23 are adjusted in advance and then fixed. In the optical system shown in FIG. 1, such a holding block 60 may be adjusted in position while moving in the optical axis direction.

As described above, in the detection of the focusing error signal by the (double) beam size method, the photodetector is provided at the position before and after the focal position of the reflected light when the focusing is performed correctly. 21 and 22 are placed. To do so, the photodetector 21 and
It is necessary to adjust the position of each 22 separately in the direction perpendicular to the optical axis.

When the holding block 60 is used, the holding block
By moving the entire 60 only in the optical axis direction, the position of the photodetectors 21 and 22 in the direction orthogonal to the optical axis direction can be adjusted all at once.

[Brief description of drawings]

FIG. 1 shows an embodiment of an optical pickup device according to the invention of the earlier application, and is a plan view of an optical configuration of the optical pickup device.

2 is a perspective view showing a part of the optical system shown in FIG. 1, showing an embodiment of the optical pickup device according to the invention of the prior application.

FIG. 3 is a graph showing the incident angle dependence of the reflection coefficient and the transmission coefficient of a glass plate.

FIG. 4 is an assembled perspective view showing an embodiment of a holder according to the present invention.

5 is a plan view seen from arrow A in FIG. 4. FIG.

FIG. 6 is a perspective view for explaining a bonding portion of a glass plate.

FIG. 7 is a perspective view showing another embodiment of the holder.

FIG. 8 is a perspective view showing still another embodiment of the holder.

FIG. 9 is a sectional view showing still another embodiment of a holding block.

[Explanation of symbols]

 11 Semiconductor laser 12 Collimating lens 13 Objective lens 14, 15 Glass plate 20 Magneto-optical disk 21, 22 Photodetector 22a, 22b, 22c Photodiode 31, 32 Analyzer 40, 60 Holding block 41 First through hole 42, 43 Second through hole 44, 45 Holding surface 44a, 45a Opening 50 Holding frame

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Noriyoshi Horie, No. 10 Hanazono Dodo-cho, Ukyo-ku, Kyoto Omron Co., Ltd.

Claims (15)

[Claims] 1. An optical pickup device comprising a light emitting element and a condensing optical system for converging divergent light emitted from the light emitting element onto an optical recording medium and condensing reflected light from the optical recording medium. In the optical path of the divergent light between the light emitting element and the condensing optical system, the optical system is tilted with respect to the optical axis of the condensing optical system and transmits a part of the incident light. At least two transparent plates that reflect light from the light receiving portion, and receive light that is transmitted by the transparent plate or is reflected by the transparent plate among the lights that are reflected by the optical recording medium and are condensed by the condensing optical system. At least two photodetectors and a holder for holding the at least two transparent plates are provided, the holding surface on which the transparent plate is fixed, and the incident light which is opened on the holding surface. The first through hole through which the above An optical pickup device, comprising: a second through hole that is opened in the holding surface and allows reflected light from the transparent plate fixed to the holding surface to pass therethrough. 2. The optical pickup device according to claim 1, wherein the transparent plate is fixed only at one position by being bonded to the holding surface of the holder by using an adhesive. 3. A moving direction of a spot light formed on the light receiving surface of the photodetector of reflected light from the transparent plate, which is caused by displacement of the transparent plate due to thermal expansion and contraction of the adhesive. 3. The optical pickup device according to claim 2, wherein the fixing point of the transparent plate is determined such that the displacement direction of the spot light caused by a tracking error is orthogonal to the light receiving surface. 4. A holding block is provided, and a first through hole through which incident light passes is formed in the holding block, and both ends of the holding block are provided with a holding surface oblique to the first through hole. The first through hole is formed in the holding surface, the second through hole is formed in the holding surface, and the second through hole is formed in the holding surface and allows reflected light from the transparent plate fixed to the holding surface to pass therethrough. ， Holder for optical pickup device. 5. The holder according to claim 4, wherein the first through hole and the second through hole are substantially orthogonal to each other. 6. The holder according to claim 4, wherein the transparent plate is fixed to one side of the transparent plate by being bonded to the holding surface with an adhesive. 7. A movement of spot light formed on a light receiving surface of a photodetector for receiving reflected light from the transparent plate, which is caused by displacement of the transparent plate due to thermal expansion and contraction of the adhesive. 7. The fixed point of the transparent plate is set so that the direction and the displacement direction of the spot light caused by a tracking error are orthogonal to each other on the light receiving surface.
The holder described in. 8. An optical pickup device comprising a light emitting element and a converging optical system for converging divergent light emitted from the light emitting element onto an optical recording medium and condensing reflected light from the optical recording medium. In the optical path of the divergent light between the light emitting element and the condensing optical system, the optical system is tilted with respect to the optical axis of the condensing optical system and transmits a part of the incident light. At least two transparent plates that reflect light from the light receiving portion, and receive light that is transmitted by the transparent plate or is reflected by the transparent plate among the lights that are reflected by the optical recording medium and are condensed by the condensing optical system. At least two photodetectors, and at least two of the lenses included in the at least two transparent plates and the condensing optical system.
An optical pickup device, comprising: a holder for holding one of the holders, wherein the holder and the transparent plate or lens held by the holder are made of the same material or a material having substantially the same coefficient of thermal expansion. 9. The optical pickup device according to claim 8, wherein the holder and at least two of the at least two transparent plates and the lens are integrally formed. 10. The optical pickup device according to claim 8, wherein the holder is formed by a frame having the transparent plate or the lens as an end surface or a cut surface. 11. A holding surface on which the transparent plate is fixed to the holder, and a first opening which opens in the holding surface and allows the incident light to pass therethrough.
9. The optical pip-up device according to claim 8, wherein the through hole and the second through hole which is opened in the holding surface and allows the reflected light from the transparent plate fixed to the holding surface to pass therethrough are formed. 12. A holder for an optical pickup device, wherein at least two of at least two transparent plates and lenses are integrally formed with a frame holding them. 13. The holder according to claim 12, wherein the transparent plate or the lens is an end surface or a cut surface of the frame. 14. An optical pickup device comprising a light emitting element and a condensing optical system for condensing divergent light emitted from the light emitting element onto an optical recording medium and condensing reflected light from the optical recording medium. In the optical path of the divergent light between the light emitting element and the condensing optical system, the optical system is tilted with respect to the optical axis of the condensing optical system and transmits a part of the incident light. At least two transparent plates that reflect the light-receiving portion, and receive the light that is transmitted by the transparent plate or is reflected by the transparent plate among the light that is reflected by the optical recording medium and is condensed by the condensing optical system. At least two photodetectors, and a holding block which holds the at least two transparent plates and two photodetectors, and is arranged so as to be movable in the optical axis direction of the condensing optical system. Light picking Up device. 15. A photodetector for receiving light emitted from the light emitting element and reflected by the transparent plate and outputting a signal for controlling the light emission intensity of the light emitting element is provided in the holding block. 15. The optical pickup device according to claim 14, which is present.