JP3137969B2 - Optical pickup device - Google Patents

Description

The present invention relates to an optical head device that optically reproduces information recorded on a recording medium or optically records information on a recording medium. Especially CD (Compact Disc) players, LVD
(Laser Vision Disc) The present invention relates to an optical pickup device for reproducing information recorded on an optical disc in a player or the like.

[Conventional technology]

Conventionally, as an optical pickup device of this type, there is an optical pickup device configured by combining many individual component elements such as a semiconductor laser, a polarizing prism, a condenser lens, and a photodetector. Was difficult.

In recent years, in addition to the above-described conventional apparatus, various types in which components other than the objective lens are formed on a single semiconductor substrate have been developed.

Fig. 15 shows a conventional optical pickup device of this type,
There was one shown in FIG. 16 (described in JP-A-64-33734). FIG. 15 is a schematic perspective view of a conventional apparatus, and FIG. 16 is a side view of a main part.

In each of the above figures, the conventional optical pickup device is mounted on a semiconductor substrate 10 and emits a laser beam for irradiating an optical disk 20 with a laser beam from the semiconductor laser 1 on one side 21. Reflected on the optical disk 20 side, the reflected laser light reflected on the optical disk 20 is transmitted through the one side surface 21 and is incident on the other side surface 22, and a part of the incident reflected laser light is reflected on the other side surface 22 and A light splitter 2 in which the reflected partially reflected laser light is reflected on the other side face 23 and then incident on the other side face 22 again;
A first light receiving element 5 buried on the surface of the semiconductor substrate 10 abutting on the other side surface 22 for receiving reflected light from the optical disk incident on the other side surface 22; And a second light receiving element 6 that is embedded on the upper surface and receives the partially reflected light of the optical disk incident on the other side surface 22.

Next, the operation of the conventional device based on the above configuration will be described. First, laser light emitted and emitted by the semiconductor laser 1 is reflected by one side surface 21 of the light splitter 2 and projected onto the surface of the optical disk 20 via an objective lens (not shown). The projected laser light is reflected by the optical disc 20, and the reflected laser light as the optical information is incident on the one side face 21 along the same path as the laser light projected onto the optical disc 20.

The incident reflected laser light is refracted and transmitted through one side 21, guided in the light splitter 2, and incident on the other side 22.
While the first light receiving element 5 below the first light receiving element 5 detects light, a part of the reflected laser light is reflected by the other side surface 22, and the partially reflected laser light is totally reflected by the other side surface 23 and is Is detected by the second light receiving element 6.

[Problems to be solved by the invention]

Since the conventional optical pickup device is configured as described above, it is necessary to reflect on the three side surfaces 21, 22, and 23 of the optical splitter 2, and one of the three side surfaces 21, 22, and 23 21 and the other side surface 23 must be polished in order to make it smooth, and furthermore, one side 21 of this polished smooth surface requires deposition of a dielectric multilayer film or the like having a semi-transparent mirror, and the polished smooth surface A reflection film must be formed on the other side surface 23 of the light-emitting device, and the processing of the light splitter 2 is complicated, and there is a problem that the entire device becomes large.

The present invention has been made to solve the above problems,
An object of the present invention is to provide an optical pickup device capable of easily processing at the time of manufacturing an optical splitter and reducing the size of the entire device.

[Means for solving the problem]

 FIG. 1 is a diagram illustrating the principle of the present invention.

In the figure, the optical pickup device according to the present invention comprises:
The light emitted from the light emitting means 1 is applied to the optical information recording carrier on which the record information is recorded, and the light reflected by the optical information recording carrier is received by the light receiving means 5, 6 provided inside the semiconductor substrate 10. In the optical pickup device for receiving light by the optical information recording medium, the light from the light emitting means 1 is irradiated onto the optical information recording medium using one side surface, and is reflected by the optical information recording medium. The light splitting means 2 for guiding the emitted light to the inside of the semiconductor substrate 10 using the one side surface is mounted, and the incident light from the light splitting means 2 is transmitted light inside the semiconductor substrate 10. Light diffracting means 3 for separating the diffracted light into light and diffracted light; and light guiding means 4 for guiding the diffracted light to a predetermined distance.
6 comprises a first light receiving element 5 for receiving the transmitted light, and a second light receiving element 6 for receiving the diffracted light via the optical waveguide means 4, wherein the first light receiving element is Receiving the transmitted light to generate at least a track signal;
Is characterized by receiving the diffracted light and generating at least a focus signal.

[Action]

In the present invention, while irradiating the light emitted from the light emitting means 1 to the optical information record carrier on which the record information is recorded,
In an optical pickup device that receives the light reflected by the optical information recording carrier by light receiving means 5 and 6 provided inside the semiconductor substrate 10, the light from the light emitting means 1 is provided on the substrate of the semiconductor substrate 10. Light splitting means 2 for irradiating the optical information recording carrier with the light by using one side surface and guiding the light reflected by the optical information recording carrier to the inside of the semiconductor substrate 10 by using the one side surface And a light diffracting means 3 for separating incident light from the light dividing means 2 into transmitted light and diffracted light, and an optical waveguide for guiding the diffracted light for a predetermined distance. Wave means 4, wherein the light receiving means 5, 6 is a first light receiving means for receiving the transmitted light.
And the second light receiving element 6 for receiving the diffracted light through the optical waveguide means 4, and as a result, the light splitting means 2 is formed only by precisely processing only one side surface 21. Therefore, the processing operation at the time of manufacturing the light dividing means 2 can be facilitated.

Further, since it is not necessary to separately provide an optical path for reflection using a surface other than the one side surface 21 in the light splitting means 2, the light splitting means 2 can be reduced in size, and therefore the entire optical pickup device can be provided. Can be reduced in size.

Furthermore, since the light receiving element and the optical waveguide means 4 are formed inside the semiconductor substrate 10, when the optical pickup device is formed using the semiconductor substrate 10, the entire optical pickup device can be downsized.

〔Example〕

(A) One Embodiment of the Present Invention Hereinafter, one embodiment of the present invention will be described with reference to FIGS. FIG. 2 is an overall side view of the apparatus of this embodiment, FIG. 3 is a configuration diagram of a main part of the apparatus of this embodiment, and FIG.
FIG. 2 is a plan view of a semiconductor substrate having a main configuration shown in FIG.

In each of the above drawings, an optical pickup device according to the present embodiment includes a semiconductor laser 1 mounted on a semiconductor substrate 10 with a laser light emitting end face inclined and emitting laser light to irradiate an optical disc 20; The laser light from the front end surface of the optical disk 20 is reflected by the one side surface 21 with respect to the optical disk 20, and the reflected laser light reflected by the optical disk 20 is transmitted through the one side surface 21 and is incident on the other side surface 22. A light splitter 2 for emitting light toward the semiconductor substrate 10 via the adhesive layer 24, and a reflected laser formed below the clad layer 25 of the semiconductor substrate 10 and emitted from the light splitter 2 to the semiconductor substrate 10 A diffraction grating 3 for diffracting and separating light into transmitted light (emitted light) and diffracted guided light; and a laminated structure formed on the lower surface of the diffraction grating 3 to transmit the transmitted light downward and to transmit the diffracted guided light to the side. An optical waveguide 4 for guiding, Serial track signal by receiving the reflected laser beam transmitted through the first reading the information such as the FR signal
A light receiving element 5, a second light receiving element 6 for receiving the diffracted guided light and reading information such as a focus signal, and a monitor light receiving element 7 for receiving the laser light emitted from the rear end face of the semiconductor laser 1. It is a configuration provided.

The chip of the semiconductor laser 1 can be formed by cutting obliquely with respect to a cleavage plane when cutting from a wafer.

The diffraction grating 3 has two regions that divide the incident light into two in a direction perpendicular to the track of the optical disc 20.
The aberration generated when the light passes through the light splitter 2 is removed, and a grating pattern is formed to be focused on each of the second light receiving elements 6 that generate a focus signal.

The semiconductor laser 1 and the optical splitter 2 include a semiconductor substrate 10
A reference mounting mark is prepared in advance on the upper side, and mounted based on the mounting mark.

In the apparatus of this embodiment, the semiconductor laser 1, the beam splitter 2, and the semiconductor substrate 10 are housed and fixed in the pickup body 30, and the objective lens 31 provided at one end of the pickup body 30 is arranged to face the optical disc 20. It is a configuration to do.

Next, the operation of the apparatus of this embodiment based on the above configuration will be described.

First, the semiconductor laser 1 emits laser light from the front and rear end faces. About half of the laser light emitted from the front end face is reflected by one side face 21 of the light splitter 2, and is condensed and irradiated on the information surface of the optical disc 20 via the objective lens 31.
The irradiated laser light is diffracted / reflected by the recorded information on the optical disc 20, and the diffracted / reflected reflected laser light is incident on one side face 21 of the light splitter 2 along the same path as the laser light, and The light passes through the inside and is guided to the other side surface 22 side of the light splitter 2.

Also, of the laser light of the semiconductor laser 1, light that has passed directly through one side surface 21 of the light splitter 2 is applied to the surface of the cladding layer 25 under the adhesive layer 24 that joins the light splitter 2 to the semiconductor substrate 10. Since the incident angle is set to be equal to or larger than the critical angle, the light is totally reflected without passing through the other side surface 22. On the other hand, the reflected laser light from the optical disc 20 is set at an angle that passes through one side surface 21 and is not totally reflected by the cladding layer 25, thereby preventing unnecessary light from being incident on the first light receiving element 5. At the same time, effective use of laser light is achieved.

The reflected laser light is incident on the diffraction grating 3 from the other side surface 22 via the adhesive layer 24 and the cladding layer 25, and the diffraction grating 3
Is diffracted and separated into transmitted light and diffracted waveguide light. Most of the reflected laser light is transmitted light, and this transmitted light is incident on the lower first light receiving element 5 and is generated as a track signal, an RF signal, and the like. Since most of the reflected laser light is transmitted light by the diffraction grating 3, the condition of the diffraction grating for reducing the amount of diffracted waveguide light from the transmitted light amount, particularly the grating depth can be made shallow, so that the design structure condition is reduced. It will be less severe.

Further, the diffracted and guided diffracted light is guided through the optical waveguide 4 and is incident on the second light receiving element 6 provided on the end face. The second light receiving element 6 includes a pair of photodetectors 61, 62, 63,
A focus signal and the like are generated from the incident diffracted waveguide light.

Further, the laser light emitted from the rear end face of the semiconductor laser 2 is received by a monitor light receiving element 7 provided on the surface of the semiconductor substrate 10 and output as an APC (Automatic Power Control) signal. When the optical output of the semiconductor laser 1 changes with the temperature, the drive current of the semiconductor laser 1 is controlled based on the APC signal to make the optical output a constant value.

As shown in FIG. 4, on the semiconductor substrate 10, a mounting land 11 for mounting and connecting the semiconductor laser 1, a laser trimming unit 14 for adjusting the operation state of an optimum point when the semiconductor laser 1 is manufactured, Output control of the semiconductor laser 1,
An electric circuit section 13 for performing light receiving signal processing of each of the light receiving elements 5, 6, 7; a bonding pad 12 used for wire bonding connection with the outside; and a four-divided light detecting section 51 forming the first light receiving element 5 To 54 are formed.

The electric circuit unit based on the track signals 51a to 54a detected by the quadrant light detection units 51 to 54 of the first light receiving element 5.
13 performs the signal operation by the push-pull method. This push-pull method is performed by performing an operation of (51a + 53a)-(52a + 54a).

In addition, the light detection units 61 and 62, 63 and 64 of the second light receiving element 6
Based on the focus signals 61a and 62a and 63a and 64a detected in the above, the electric circuit unit 13 calculates a signal by the Foucault method. This Foucault method is performed by performing an operation of (61a-62a) + (64a-63a).

Further, the APC circuit in the electric circuit section 13 adjusts the laser output based on the APC signal received by the monitor light receiving element 7.

Since the mounting lands 11 are provided on the semiconductor substrate 10, the semiconductor laser 11 can be directly die-bonded to the semiconductor substrate 10 of the optical integrated circuit. Can be reduced, and the mounting accuracy can be improved.

The design example of each layer of the semiconductor substrate 10 is shown below.

(B) Manufacturing method of one embodiment of the present invention FIG. 5 is an explanatory diagram of a manufacturing method of the optical splitter 2 in the optical pickup device according to the present embodiment.

In the figure, one of the A surface and the B surface of the transparent plate is polished to a smooth surface, and a dielectric multilayer film or the like is deposited on the polished smooth surface to form a semi-transparent mirror. The plate on which the semi-transparent mirror is formed is cut at an angle θ with respect to each of the A and B planes as shown by the chain line in the figure.

Thus, the light splitter 2 is formed only by polishing a single surface of the transparent plate to form a semi-transparent mirror.

The light splitter 2 has a cut surface (third surface) cut at an angle θ with respect to a surface which is a semi-transparent mirror (one side surface 21 in FIG. 3).
In the figure, the other side surface 22) is placed on the semiconductor substrate 10,
The cut surface is bonded and fixed to the semiconductor substrate 10 with an adhesive. This adhesive is a transparent medium, and one having a refractive index equivalent to that of the light splitter 2, for example, a UV-curable adhesive is selected. Therefore, even if the cut surface is not particularly polished, the uneven portion is filled with the adhesive, and scattering and reflection of light on the cut surface (the other side surface 22) are eliminated.

(C) Attachment Mode of Light-Emitting Element According to Embodiment of the Present Invention FIG. 6 is a schematic perspective view of a semiconductor laser. FIGS. 7A and 7B show a state in which the semiconductor laser 1 is mounted on a semiconductor substrate 10. FIG.

In each of the above figures, the semiconductor laser 1 is mounted on a mounting land 11 of an aluminum electrode formed by vapor deposition on a semiconductor substrate 10, and the side electrodes 1a and 1b and the mounting land 11 are fixed by soldering. . The gap 11b between the soldered semiconductor laser 1 and the semiconductor substrate 10 is formed by the projection of the mounting land 11, so that the semiconductor laser 1 directly contacts the semiconductor substrate 10 itself and a short circuit occurs. It is preventing that. In addition, besides the protrusion of the mounting land 11,
An insulating material can be deposited on 11b to prevent a short circuit state of the semiconductor laser.

FIG. 8 shows a semiconductor laser 1 mounted on a mounting land 11.
The mounting lands 11 forming the aluminum electrodes are formed larger than the area required for bonding and fixing the semiconductor laser 1. By forming the mounting land 11 with such a large area, the heat radiation characteristics of the semiconductor laser 1 are improved.

FIG. 9 is a plan view of the semiconductor substrate 10 on the lower surface where the semiconductor laser 1 is mounted. In FIG. 9, the monitor light receiving element 7 is formed on the lower surface where the semiconductor laser 1 is mounted.

FIGS. 10A and 10B show a semiconductor substrate 10 similar to FIG.
FIG. 1A, the diffraction grating 3 is formed on the lower surface of the semiconductor laser 1, and in FIG. 2B, the diffraction grating 3 and the monitor light receiving element 7 are formed on the lower surface of the semiconductor laser 1.

FIG. 11 is an explanatory view of the attachment of the main part of the semiconductor laser 1 to the semiconductor substrate 10, in which a step 11 is provided on the semiconductor substrate 10.
It is formed as a mounting land 11 having a. As described above, the stepped portion 11a of the mounting land 11 allows the semiconductor laser 1 to be mounted.
Abuts the step portion 11a to facilitate mounting position determination.
Mounting work can be performed with high accuracy and speed.

12 (A), (B), and (C) are views for explaining main parts of the semiconductor substrate 10 attached to the side surfaces of the semiconductor substrate 10. FIG. As shown in FIG. 1A, the semiconductor laser 1 is bonded to the side surface of the semiconductor substrate 10 with an adhesive.
15 (B), (C)
As shown in FIG. 5, a mounting land 11 as an electrode is formed so as to extend to the side surface of the semiconductor substrate 10, and the mounting land thus formed is formed.
It is also possible to adopt a configuration in which the electrodes 1a and 1b of the semiconductor laser 1 are abutted and fixed to 11.

FIGS. 13A and 13B are schematic perspective views of a mounting base for a semiconductor laser. In the figures (A) and (B), the mounting base 10
0 is formed by sandwiching the non-conductive substance 101 between the conductive substances 101a and 101b. The semiconductor laser 1 is mounted on the mounting base 100,
Alternatively, it is bonded and fixed by being sandwiched and soldered. As described above, the semiconductor laser 1 can be easily attached to another member, for example, the semiconductor substrate 10 via the attachment base 100.

FIG. 14 shows a modified mounting mode of the mounting base 100 described in FIG. 13, and shows the mounting base 100 depending on the light output direction of the semiconductor laser 1.
The through-hole 101c is formed in the non-conductive substance 101 or a transparent substance is formed, and laser light can be emitted in the direction of the arrow. Further, the upper surface or the lower surface of the mounting base 100 is formed to be inclined, so that the laser light output can be emitted vertically and obliquely.

(D) Another embodiment of the present invention Although the light splitter 2 has a configuration in which only one side surface 21 is polished to be a semi-transparent mirror, an antireflection film is provided on the other side surfaces 23 and 26 (see FIG. 3). It can also be formed. This anti-reflection film emits stray light such as scattered light to the outside of the light splitter 2 to prevent unnecessary laser light (laser light other than light reflected from the optical disc 20) from entering the first light receiving element 5. In addition, the effective use of laser light is further improved.

The relationship among the light splitter 2, the adhesive layer 24, the cladding layer 25, and the diffraction grating 3 may be as follows.

_{n 2> n 20> n 24} > n 3 where, n ₂ is the refractive index of the optical splitter 2, n ₂₀ is the refractive index of the adhesive layer, n ₂₄ is the refractive index of the cladding layer 24, n ₃ is a diffraction grating Is the refractive index of

As described above, by sequentially setting the refractive index to be smaller toward the incident direction of the reflected laser light, reflection at each boundary surface can be effectively prevented, and the transmission efficiency of the effective light beam can be further improved.

In each of the above embodiments, the light diffracting means is constituted by a region formed from two regions, but may be constituted by two or more regions.

In the above embodiments, the light diffraction means is constituted by a diffraction grating. However, it may be constituted by a step grating or other diffraction means or various optical elements for branching and emitting incident light to the optical waveguide and the first light receiving element on the lower surface.

〔The invention's effect〕

As described above, in the present invention, the light emitting means 1
Irradiates the light emitted from the optical information recording medium on which the recording information is recorded, and receives the light reflected by the optical information recording carrier by light receiving means 5, 6 provided inside the semiconductor substrate 10. In the optical pickup device, on the substrate of the semiconductor substrate 10, the light from the light emitting means 1 is irradiated on the optical information recording carrier using one side surface,
The light splitting means 2 for guiding the light reflected by the optical information recording carrier into the semiconductor substrate 10 using the one side surface is mounted, and the light splitting means is provided inside the semiconductor substrate 10. A light diffracting means 3 for separating incident light from the light source 2 into transmitted light and diffracted light; and an optical waveguide means 4 for guiding the diffracted light by a predetermined distance. Since it is composed of the first light receiving element 5 for receiving light and the second light receiving element 6 for receiving the diffracted light via the optical waveguide means 4, as a result, only one side is precisely processed. Since the light dividing means can be formed, the processing operation at the time of manufacturing the light dividing means can be facilitated.

Therefore, the manufacturing process of the entire optical pickup device can be simplified.

Further, since it is not necessary to separately provide an optical path for reflection using another surface other than the one side surface in the light splitting unit, the light splitting unit can be reduced in size, and therefore the entire optical pickup device can be reduced in size. Can be

Further, since the light receiving element and the optical waveguide means are formed inside the semiconductor substrate, the size of the entire optical pickup device can be reduced when the optical pickup device is formed using the semiconductor substrate.

[Brief description of the drawings]

FIG. 1 is a view for explaining the principle of the present invention, FIG. 2 is an overall side view of one embodiment of the present invention, FIG. 3 is a configuration diagram of a main part of one embodiment of the present invention, and FIG. FIG. 5 is an explanatory view of a method of manufacturing an optical splitter in one embodiment of the present invention, FIG. 6 is a schematic perspective view of a semiconductor laser installed in one embodiment of the present invention, FIG. 7 (A) and 7 (B) are views for explaining a mounting state of a semiconductor laser, FIGS. 8 and 9 are plan views of a semiconductor substrate showing a mounting land forming portion, and FIGS. 10 (A) and 10 (B) are semiconductor substrates. Illustration of formation of a plane,
(A) is an explanatory view of a diffraction grating forming portion, (B) is a plan view of a semiconductor substrate of a diffraction grating and a mounting land forming portion, and FIGS. 11 and 12 (A), (B), (C). ) Is an explanatory view of mounting a semiconductor laser on a semiconductor substrate, FIGS. 13 (A) and (B), FIG. 14 is an explanatory view of a mounting base for mounting a semiconductor laser, and FIG. 15 is a schematic perspective view of a conventional optical pickup device. FIG. 16 shows a side view of a main part of a conventional optical pickup device. DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser (light emitting means) 2 ... Light splitter (light splitting means) 3 ... Diffraction grating (light diffraction means) 4 ... Optical waveguide 5 ... 1st light receiving element 6 ... 2nd light receiving element 7 …… Monitor light receiving element 10 …… Semiconductor substrate 20 …… Optical disk 30 …… Pickup body 31 …… Objective lens

Claims (7)

(57) [Claims] An optical information recording carrier on which recording information is recorded is irradiated with light emitted from a light emitting device, and the light reflected by the optical information recording carrier is provided inside a semiconductor substrate. In the optical pickup device receiving the light, the light from the light emitting unit is irradiated on the optical information recording carrier by using one side surface, and is reflected by the optical information recording carrier on the substrate of the semiconductor substrate. A light dividing unit that guides the light into the semiconductor substrate using the one side surface is mounted, and inside the semiconductor substrate, incident light from the light dividing unit is separated into transmitted light and diffracted light. Light diffracting means, and light guiding means for guiding the diffracted light for a predetermined distance, wherein the light receiving means comprises: a first light receiving element for receiving the transmitted light; and the light guiding means for diffracting the diffracted light. Receive through The second
Wherein the first light receiving element receives the transmitted light and generates at least a track signal, and the second light receiving element receives the diffracted light and generates at least a focus signal. An optical pickup device, characterized in that: 2. The optical pickup device according to claim 1, wherein the second light receiving element includes a pair of light detectors, wherein the light diffraction unit includes a diffraction grating, and the diffraction grating includes the pair of light detectors. An optical pickup device, which is formed in a lattice pattern for condensing light on each of the light detecting units. 3. The optical pickup device according to claim 1, wherein the light diffracting means is constituted by two regions which divide light incident on the light diffracting means into two. An optical pickup device characterized in that: 4. The optical pickup device according to claim 1, wherein the first light receiving element is formed below the optical diffraction means, and the second light receiving element is An optical pickup device formed at an end of the optical waveguide means. 5. The optical pickup device according to claim 1, wherein a transparent medium having substantially the same refractive index as the light splitting means is provided between the light splitting means and the semiconductor substrate. An optical pickup device comprising an adhesive layer interposed therebetween. 6. The optical pickup device according to claim 1, wherein said light emitting means emits light also from an end face opposite to an end face which is emitted to irradiate said optical information recording carrier. A third light receiving element for receiving light emitted from the opposite end face, and wherein the light emitting unit controls output of the emitted light based on the third light receiving element. Optical pickup device. 7. The optical pickup device according to claim 5, wherein the refractive indices of the light splitting means, the adhesive layer, and the optical diffraction grating are set in a direction of incidence of reflected light from the optical information recording carrier. An optical pickup device wherein the refractive index is set so as to decrease sequentially.