JPH0950645A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve positional precision of component while avoiding the increasing complexity of process by making the high precision of light emission surfaces and realistically moldable precision of resin surface coexist each other while simplifying an optical system with a resin unified molding. SOLUTION: The laser beam of an outgoing path outputted from a laser diode 104 transmits through a hologram element 120 to be outputted without being reflected and is made incident on a disk. Besides, the laser beam of a returning path reflected on the disk is deffracted at the hologram element 120 and two beams are made incident on reflection mirrors 116, 118 of a resin body 112 and are reflected to be made incident on photodetectors. On the other hand, a monitor light outputted from the rear part of the laser diode 104 is reflected on a reflection mirror 114 of the resin body 112 to be made incident on a monitor diode.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a CD, MD, LD
The present invention relates to an optical pickup for recording or reproducing information on or from an optical information recording medium, and particularly to an improvement suitable for reduction in size and weight.

[0002]

BACKGROUND ART Various types of optical pickups have been already known as optical pickups for recording and reproducing information on optical discs such as CDs, MDs and LDs. Some examples are as follows.

Japanese Unexamined Patent Publication No. 5-314537: A prism type optical head in which optical functions such as a laser diode, a light collecting means, and a photodetecting element are integrally integrated in one prism block is disclosed. Japanese Laid-Open Patent Publication No. 6-4894: An optical pickup device is disclosed in which a lens, a prism, and the like inside the pickup are integrated by molding with a transparent material.

Japanese Unexamined Patent Publication No. 5-307760: A semiconductor laser is fixed on a semiconductor substrate on which a photodetector is formed,
An optical pickup in which an optical path changing mirror is formed on a semiconductor substrate by 45 ° etching is disclosed. As described above, in order to reduce the size and weight of the optical pickup and reduce the cost, various attempts have been made to integrate various functions performed by individual components on the same substrate or integrally mold them with resin. There is.

[0005]

However, in the above background art, it is necessary to pay attention to the following points. (1) Generally, in resin molding, surface accuracy is more difficult to obtain than in glass and the like. In particular, the wavefront aberration accumulates as the number of surfaces of the resin / air interface increases. Further, with the same surface precision, the occurrence of wavefront aberration is larger when the light beam is reflected than when it is transmitted (up to several times).

(2) In the optical disk pickup, the required wavefront accuracy differs depending on the forward / backward light flux. On the return path, the reproduction signal is obtained as an integrated value of the intensities of all luminous fluxes,
A diffraction-limited optical system is unnecessary, and it is sufficient if the accuracy as an error detection system is satisfied. On the other hand, in the forward path, it is necessary to connect a diffraction-limited spot on the disk, and the output light wavefront aberration of the entire pickup is RMSD <0.05λ at the maximum, which is extremely strict accuracy. That is, the optical components that make up the outward optical system are
All must be managed with strict wavefront accuracy.

(3) The photodetector is usually formed on a silicon wafer, but since a highly accurate mask or the like is used in the wafer process, its alignment mark or the like can be used and the positional accuracy can be easily obtained. Utilizing this, if the laser chip is fixed on the wafer, the mutual positional relationship between the light emitting point and the light receiving point can be accurately determined. However, in the current laser chip structure, if it is fixed on the wafer, the emission optical axis, and thus the optical axis of the return light flux, becomes substantially parallel to the light receiving surface of the photodetector. For this reason, it is necessary to provide a mirror for optical path conversion (for example, 90 °) somewhere in order to guide the returning light flux to the light receiving surface of the photodetector.

Considering the background art in view of these points, first, in the above-mentioned conventional example, all the optical functions in the outward path including the objective lens function are to be achieved at the interface of the optical block. If it is applied, deterioration of the accuracy of the output wavefront cannot be avoided. Therefore, it cannot be said to be preferable in terms of feasibility.

Next, in the conventional example, the conventional optical component and the optical base are simply integrally molded with resin, and similarly, the problem of the output wavefront accuracy arises. Further, in consideration of the degree of removal from the resin molding die, the curved surface structure of the lens or the like is greatly restricted, which may hinder the achievement of the function as a pickup.

Further, in the prior art example, the optical path of the light flux immediately after the laser emission is changed by the etched mirror formed by the wafer process, but in order to maintain the emission wavefront accuracy, the etching condition and the crystal axis of the wafer are kept. There are many problems such as management, yield reduction, and complicated process steps and equipment.

The present invention focuses on the above points,
The purpose is to improve the position accuracy of parts while avoiding complication of the process, while achieving high output wavefront accuracy and resin surface accuracy that can be actually formed while simplifying the optical system by resin molding. Is. Another object is to reduce the size and weight of the optical pickup, and hence the optical disc device, and to reduce the cost and simplify the production equipment.

[0012]

In order to achieve the above object, the present invention provides an optical path changing mirror for changing the optical path of laser light to a desired direction only on the return path of laser light from an information recording medium. On the substrate on which the photodetector is formed, the laser light source is fixed so that the substrate surface and the optical axis of the laser light are substantially parallel, and the substrate and the laser light source are It is characterized in that it is sealed with a transparent resin, and the optical path conversion mirror is formed on a part of the surface of the sealing resin so as to act only on the laser light in the returning path. The above and other objects, features and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to Examples.

[0014]

[Embodiment 1] First, Embodiment 1 will be described with reference to FIGS. FIG. 1 is a perspective view showing the outer appearance of the first embodiment, FIG. 2 is a side view, and FIG.
It is a top view of the wafer which comprises. In these figures, a submount 102 having an appropriate height is provided near the center of a wafer 100 made of a semiconductor such as Si, and a laser diode 104 is arranged on the top thereof. At this time, the optical axis of the laser light emitted from the laser diode 104 is substantially parallel to the wafer 100.
Then, photodetectors 106 and 108 divided into three are provided on both sides of the submount 102 of the wafer 100, respectively. A monitor diode 110 is formed on the wafer 100 on the rear monitor light output side of the laser diode 104.

The wafer 100 having such a structure is a resin body 1 integrally formed by using a transparent resin as shown in FIG.
12 is sealed. Laser diode 1 of resin body 112
A reflecting mirror 114 for the monitor light is formed on the rear part of 04 by an inclined surface of resin. Reflecting mirrors 1 for the signal laser light are provided on both sides thereof with different resin slopes.
16, 118 are formed. A hologram element 120 is formed on the laser beam emitting surface of the resin body 112 as a branch element for branching the laser beam. Therefore, the space between the emitting end surface of the laser light source, the detection surface of the photodetector, and the surface forming the outer shape of the resin body is filled with the sealing resin.

Next, the reflecting mirrors 114, 116 and 118 formed by the resin slant surface are formed so as to form an angle of 45 ° with respect to the optical axis of the returning light from the disk (not shown) in this embodiment. ing. As a result, the return laser beam or monitor light is reflected by 90 °, and the reflection mirror 11
4 to enter the monitor diode 110, or the photodetector 10 via the reflection mirrors 116 and 118.
It is incident on 6,108.

Next, the operation of the first embodiment configured as described above will be described. The forward laser beam output from the laser diode 104 passes through the hologram element 120 without being reflected and is output. , Is incident on the disk through another element such as a grating. Then, the returning laser beam reflected by the disk is diffracted by the hologram element 120 and separated into two outgoing optical paths, and the two beams are reflected by the reflecting mirror 11 of the resin body 112.
6, 118 respectively. The laser beams reflected by the reflection mirrors 116 and 118 enter the photodetectors 106 and 108, respectively. Therefore, the reflection mirrors 116 and 118 act only on the outward laser light. On the other hand, the monitor light output from the rear part of the laser diode 104 is reflected by the reflection mirror 114 of the resin body 112 and enters the monitor diode 110.

As described above, according to the first embodiment, of the laser beams for recording or reproducing on the disc, the beam on the outward path goes straight to the disc without being subjected to optical path conversion. Then, the return beam is subjected to optical path conversion and is incident on the photodetectors 106 and 108.

That is, the mirror acts only on the return laser beam, and only the return laser beam after being branched by the hologram element 120 is subjected to optical path conversion. Therefore, only the surface of the hologram element 120 needs to be molded with high accuracy, the accuracy of the mirror is relaxed, and it is possible to sufficiently use the resin molding surface. In other words, while achieving simplification of the optical system by resin integral molding, it is possible to achieve both high outgoing wavefront accuracy and resin surface accuracy that can be actually manufactured. Further, as the structure of the resin surface mirror, since a recess having an inclined surface of about 45 ° with respect to the wafer may be formed, the structure is simple and the manufacturing process can be prevented from becoming complicated.

As in the first embodiment, the resin body 11
By making the second laser beam emission surface substantially perpendicular to the emission optical axis of the laser beam, it is possible to prevent the optical axis from changing when the laser beam is emitted from the inside of the resin 112 to the external space. it can.

[0021]

Second Embodiment Next, a second embodiment will be described with reference to FIGS. FIG. 4 is a side view of the second embodiment, and FIG. 5 is a partially cutaway perspective view showing an exploded main part. This example is an example in which the unevenness of the resin body has the opposite relationship to that of the first embodiment. On the wafer 130, as in the first embodiment, the submount 132, the laser diode 134, the monitor diode 136, and the photodetectors 138 and 140 divided into three parts.
Are provided respectively. The wafer 130 is placed on an appropriate base 141 and entirely covered with a resin body 142. The space sealed by the base 141 and the resin body 142 is filled with, for example, an inert gas.

Inside the resin body 142, reflecting mirrors 144, 146, 148 corresponding to the reflecting mirrors 114, 116, 118 of the first embodiment are formed of resin surfaces, respectively. A hologram element 150 is formed on the laser beam output surface of the resin body 142.

The operation of the second embodiment is basically the same as that of the first embodiment, and the return laser beam branched by the hologram element 150 is reflected by the reflecting mirror 14.
It is reflected by 6, 148 and enters the photodetectors 138, 140, respectively. The monitor light output from the rear part of the laser diode 134 is reflected by the reflection mirror 144 and enters the monitor diode 136. As described above, in the second embodiment, since the wafer and the resin body are separate bodies, the positional relationship between the two can be adjusted.

[0024]

Other Embodiments The present invention can be variously modified based on the above disclosure, and includes, for example, the following. (1) On the wafer, in addition to the photodetector for photodetection power,
Necessary circuits such as a voltage converter, an amplifier and an arithmetic circuit may be integrally formed (so-called monolithic).

(2) In the above embodiment, the monitor light emitted from the rear part of the laser diodes 104 and 134 is reflected by the reflection mirrors 114 and 144 of the resin bodies 112 and 142 and enters the monitor diodes 110 and 136. However, in addition to this, the top surface 1 of the submounts 102 and 132
Various resin surfaces can be used, for example, after being reflected by 03, 133 and then reflected by the resin surface and incident on the monitor diodes 110, 136. Also,
It is also possible to form tapered recesses along the light flux of the monitor light on the laser diode mounting surfaces 103, 133 of the submounts 102, 132.

(3) In the above embodiment, the substrate on which the photodetector is formed and the laser light source are sealed with a transparent resin, but they are simply fixed with a transparent resin. A case formed by a glass press instead of the transparent resin. May be used.
Further, a transparent resin may be filled between at least one of the emission end surface of the laser light source or the detection surface of the photodetector and the sealing resin surface to be integrally molded, or substantially equal to the sealing resin. A transparent material having a refractive index may be filled.

[0027]

As described above, according to the present invention, the mirror formed by the sealing resin surface is provided only on the return path of the light, so that the optical system is simplified by the resin integral molding, and the high output is achieved. It is possible to improve both the wavefront accuracy and the resin surface accuracy that can be actually formed, to improve the component position accuracy while avoiding the complexity of the process, and to reduce the size and weight of optical pickups and optical disk devices. it can.

[Brief description of drawings]

FIG. 1 is a perspective view showing an appearance of a first embodiment.

FIG. 2 is a side view showing the main configuration of the first embodiment.

FIG. 3 is a plan view showing a main part of the first embodiment.

FIG. 4 is a side view showing the main configuration of the second embodiment.

FIG. 5 is a partially cutaway exploded perspective view showing the main configuration of the second embodiment.

[Explanation of symbols]

100, 130 ... Wafer 102, 132 ... Submount 104, 134 ... Laser diode 106, 108, 138, 140 ... Photodetector 110, 136 ... Monitor diode 112, 142 ... Resin body 114, 116, 118, 144, 146 148 ... Mirror 120, 150 ... Hologram element 141 ... Base 103, 133 ... Installation surface

Claims (6)

[Claims] 1. A laser light source for generating a laser beam for irradiating an information recording medium; a branching element for branching a returning laser beam from the information recording medium; an optical path for converting an optical path of the returning laser beam. A conversion mirror; a photodetector for detecting the returning laser beam obtained by the branching element; and on the substrate on which the photodetector is formed, the substrate surface and the optical axis of the laser beam are substantially While fixing the laser light source so as to be parallel to each other, the substrate and the laser light source are sealed with a transparent resin, and a part of the surface of the sealing resin acts only on the laser light in the return path. An optical pickup, wherein the optical path changing mirror is formed. 2. A photodetector for optical output monitoring of the laser light source is integrally formed on the substrate, and a part of the sealing resin surface is used as a mirror for optical path conversion of monitor light. The optical pickup according to claim 1. 3. The optical pickup according to claim 1, wherein the laser light emitting surface of the sealing resin is substantially perpendicular to the laser light emitting optical axis. 4. A transparent resin is filled between the emitting end surface of the laser light source, at least one of the detection surfaces of the photodetectors, and the sealing resin surface to be integrally molded. The optical pickup described in 1, 2, or 3. 5. A transparent material having a refractive index substantially equal to that of the sealing resin is filled between the emitting end surface of the laser light source, at least one of the detection surfaces of the photodetectors, and the sealing resin. The optical pickup according to claim 1, 2 or 3, characterized in that: 6. The branch element is integrally formed on a laser beam emitting surface of the sealing resin.
Optical pickup as described.