JPH0489636A - Optical pickup device - Google Patents

Abstract

PURPOSE:To make machining work easy and to miniaturize the whole device by reflecting light from a light emitting means to the side of an optical information recording carrier on one side of a beam splitting means, making the reflected light incident to the other side by refracting and transmitting it on one side, and splitting this incident light into transmitted light and diffracted light. CONSTITUTION:The light from a light emitting means 1 is reflected to the side of the optical information recording carrier on one side 21 of a beam splitting means 2, and the light reflected from the side of the optical information recording carrier is made incident to another side 22 by refracting and transmitting it on the one side 21. This incident light is transmitted through the other side 22 and guided into an optical waveguide 4 by the diffracting operation of a light diffracting means 3. Thus, since the light can be made incident to the light diffracting means 3 and splitted into the transmitted light and the diffracted light by the reflection only on one side 21 of the light splitting means 2, the machining work can be easily executed when manufacturing the splitter 2, and the device can be miniaturized as a whole.

Description

[Detailed Description of the Invention] [Industrial Application Field] 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, L V D (La+e+ViSion D
iSc) relates to an optical pickup device for reproducing information recorded on an optical disc in a player or the like.

[Conventional technology]

Conventionally, this type of optical pickup device has been constructed by combining many individual components such as a semiconductor laser, a polarizing prism, a condensing lens, and a photodetector. It was difficult to adjust.

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

This type of conventional optical pickup device is shown in Fig. 15.
There was one shown in Figure 16 (Japanese Unexamined Patent Publication No. 64-33734
(described in the issue). FIG. 15 is a schematic perspective view of the conventional device, and FIG. 16 is a side view of the main parts.

In each of the above figures, a conventional optical pickup device is mounted on a semiconductor substrate 10, and includes a semiconductor laser 1 that emits laser light to irradiate an optical disk 20, and a side surface 21 that emits the laser light from the semiconductor laser 1. The reflected laser light that is reflected toward the optical disk 20 side and reflected by the optical disk 20 is transmitted through the one side surface 21 and enters the other side surface 22, and a part of the incident reflected laser light is reflected on the other side surface 22. At the same time, the partially reflected laser beam is reflected on the other side 2.
The light splitter 2 enters the other side 22 again after being reflected at 3.
a first light-receiving element 5 that is embedded on the surface of the semiconductor substrate 10 that is in contact with the other side surface 22 of the light splitter 2 and receives the reflected light from the optical disk that is incident on the other side surface 22;
The structure includes a second light receiving element 6 which is buried on the surface of the semiconductor substrate 10 in the same way as the light receiving element 5 and receives the partially reflected light from the optical disk that is incident on the other side surface 22.

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

The incident reflected laser beam is refracted and transmitted through one side 21, guided through the light splitter 2, and irradiated onto the other side 22, and is received and detected by the first light receiving element 5 below the other side 22. A portion of the reflected laser beam is reflected by the other side surface 22, and this partially reflected laser beam is totally reflected by the other side surface 23 and is received and detected by the second light receiving element 6 below the other side surface 22.

[Problem to be solved by the invention]

Since the conventional optical pickup device is configured as described above, the three sides 21, 22, and 23 of the optical splitter 2 are
These three sides 21.22.2
One side 21 and the other side 23 in 3 must be polished to make them smooth, and furthermore, it is necessary to evaporate a dielectric multilayer film or the like using this polished smooth surface 21 as a semi-transparent mirror. At the same time, a reflective film must be formed on the other side surface 23 of the polished smooth surface, which complicates the processing of the light splitter 2 and increases the size of the entire device.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an optical pickup device in which processing during manufacturing of a light splitter can be facilitated and the entire device can be miniaturized.

[Means to solve the problem]

FIG. 1 shows a diagram explaining the principle of the present invention.

In the figure, the optical pickup device according to the present invention is formed of a semiconductor substrate 10, and directs light emitted from a light emitting means 1 placed on the semiconductor substrate 10 to an optical information recording carrier on which recorded information is recorded. In an optical pickup device that emits light and receives light reflected by the optical information recording carrier, the light from the light emitting means 1 is reflected toward the optical information recording carrier by one side 21, and the light is reflected by the optical information recording carrier. The reflected light is transmitted through the one side surface 21 and enters the other side surface 22.
a light splitting means 2 for guiding the light to the light splitting means 2; and the other side surface 2 of the light splitting means
The light diffraction means 3 separates the light emitted from the light beam 2 into transmitted light and diffracted light.

[Effect]

In the present invention, the light from the light emitting means 1 is split into the light dividing means 2.
The light is reflected from one side surface 21 to the optical information recording carrier side, and the light reflected from the optical information recording carrier side is refracted and transmitted through one side surface 21 and enters the other side surface 22 . Since this incident light passes through the other side surface 22 and is guided into the optical waveguide 4 by the diffraction action of the light diffraction means 3, one side surface 22 of the light splitting means 2
The light is incident on the light diffraction means (3) by reflection by the splitter 2, and can be separated into transmitted light and diffracted light, which facilitates processing work during the manufacture of the splitter 2 and allows the entire device to be miniaturized. becomes.

〔Example〕

(a) One Embodiment of the Present Invention An embodiment of the present invention will be described below with reference to FIGS. 2 to 4. This FIG. 2 is an overall side view of the device of this embodiment.
FIG. 3 is a diagram showing the configuration of the main parts of the device of this embodiment, and FIG. 4 is a plan view of a semiconductor substrate having the configuration of the main parts shown in FIG.

In each of the above figures, the optical pickup device according to the present embodiment includes a semiconductor laser 1 that is mounted on a semiconductor substrate 10 with its laser beam emitting end face inclined, and emits a laser beam that is irradiated onto an optical disk 20; The laser beam from the front end surface of the optical disk 20 is reflected by one side surface 21, and the reflected laser beam reflected by the optical disk 20 is transmitted through one side surface 21 and enters the other side surface 22, and the reflected laser beam that has entered is A light splitter 2 that emits light to the semiconductor substrate 10 side via the adhesive layer 24, and a reflective laser that is formed under the cladding layer 25 of the semiconductor substrate 10 and that is emitted from the light splitter 2 to the semiconductor substrate 10. A diffraction grating 3 that diffracts and separates light into transmitted light (radiated light) and diffracted waveguided light is laminated on the lower surface of the diffraction grating 3, and transmits the transmitted light downward and directs the diffracted waveguided light to the sides. An optical waveguide 4 that guides the wave, a first light receiving element 5 that receives the transmitted reflected laser light and reads information such as a track signal and an RF multiplied signal, and a first light receiving element 5 that receives the diffracted guided wave light and reads information such as a focus signal. This configuration includes a second light receiving element 6 and a monitor light receiving element 7 that receives laser light emitted from the rear end face of the semiconductor laser 1.

The chip of the semiconductor laser 1 can be manufactured by cutting the semiconductor laser 1 obliquely from the wafer when cutting it out from the wafer.

The diffraction grating 3 has two regions that divide the incident light into two in the direction perpendicular to the track of the optical disk 20,
The configuration is such that aberrations generated when the light passes through the light splitter 2 are removed and the light is condensed into a lattice pattern on each of the second light receiving elements 6 that generate a focus signal.

The semiconductor laser 1 and the light splitter 2 are provided on a semiconductor substrate 10.
A reference mounting mark is prepared in advance on the top, and the product is mounted based on this mounting mark.

In addition, in the device of this embodiment, the semiconductor laser 1, the light splitter 2, and the semiconductor substrate 10 are housed and fixed in a pickup body 30, and an objective lens 31 provided at one end of the pickup body 30 is arranged to face the optical disk 20. It is configured to do this.

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

First, the semiconductor laser 1 emits laser light from each of its front and rear end faces. Approximately half of the laser light emitted from the front end face is reflected by one side 21 of the light splitter 2, and is condensed and irradiated onto the information surface of the optical disc 20 via the objective lens 31. This irradiated laser light is diffracted and reflected by the recorded information on the optical disk 20, and this diffracted and reflected reflected laser light is incident on one side 21 of the light splitter 2 along the same path as the laser light, and is incident on the one side 21 of the light splitter 2. The other side 2 of the light splitter 2
Guide the wave to the 2nd side.

Further, among the laser beams of the semiconductor laser 1, the light directly transmitted through one side 21 of the light splitter 2 is transmitted to the cladding layer 24 below 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 greater than the critical angle on the surface of , the light is totally reflected without being transmitted through the other side surface 22 .

On the other hand, the reflected laser beam of the optical disc 20 is reflected from one side 2.
Since the angle is set at such an angle that the laser beam passes through the first light receiving element 5 and is not totally reflected by the cladding layer 24, unnecessary light is prevented from entering the first light receiving element 5, and the laser beam is effectively utilized. .

This 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 is diffracted and separated by the diffraction grating 3 into transmitted light and diffracted guided light. Most of the reflected laser light becomes transmitted light, which enters the lower first light receiving element 5 and is generated into a track signal and an RF multiplied signal. Since most of the reflected laser light becomes transmitted light by the diffraction grating 3, the conditions for the diffraction grating, especially the depth of the grating, can be made shallower to reduce the amount of diffracted waveguide light than the amount of transmitted light, so the design and manufacturing conditions can be improved. It becomes less strict.

Further, the diffraction-separated guided waveguide light is guided through the optical waveguide 4 and is incident on the second light receiving element 6 provided at the end face.

This second light receiving element 6 has a pair of light detecting parts 61, 62, 63.
・It is formed with two sets of 64, and generates a focus signal etc. from the incident diffraction guided wave light.

Further, the laser light emitted from the rear end facet of the semiconductor laser 2 is received by a monitor light receiving element 7 provided on the surface of the semiconductor substrate 10, and is converted into an APC (Automatic Point Pole).
When the optical output of the semiconductor laser 1 changes with temperature, the driving current of the semiconductor laser 1 is controlled based on the APC signal to maintain the optical output at a constant value.

As shown in FIG. 4, on the semiconductor substrate 10 there are a mounting land 11 for mounting and connecting the semiconductor laser 1, and a laser trimming section 14 for adjusting the operating state to the optimum point when manufacturing the semiconductor laser 1. , an electric circuit section 13 that performs output control of the semiconductor laser 1, processing of received light signals of each light receiving element 5, 6, 7, etc., a bonding pad 12 used for wire bonding connection with the outside, and a first light receiving element 5. Four divided photodetecting sections 51 to 54 are formed.

Based on the respective track signals 51a to 54a detected by the four-division light detection units 51 to 54 of the first light receiving element 5, the electric circuit unit 13 performs signal calculation using a push-pull method.

This push-pull method is (51a+53a)-(52a+
This is done by performing the calculation 54a).

In addition, the light detection portions 61, 62, 63 of the second light receiving element 6
-Focus signals 61a and 62a detected at 64
Based on s 63 a and 64 a, the electric circuit section 13
calculates signals using the Foucault method. This Foucault method is performed by performing the calculation (61a-62a)+(64a-63a).

Furthermore, 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 land 11 is 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.
The number of conventional parts such as wire bonding and silicone bats can be reduced, making it possible to improve mounting accuracy.

Note that design examples for each layer of the semiconductor substrate 10 are shown below.

Layer thickness Refractive index Material Adhesive layer
t= 10μm n=1.51 cladding layer t=
0.5μm n=1.38 MgF2 optical waveguide layer t=1.0μm n=1.51 5i02
Core layer t=2.0μm n=1.38
MgF2(b) Manufacturing method according to an embodiment of the present invention FIG. 5 is an explanatory diagram of a method for manufacturing the light splitter 2 in the optical pickup device according to the present embodiment.

In the figure, either the A side or the B side of the transparent plate is polished to make it 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 planes A and B, as shown by chain lines in the figure.

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

This light splitter 2 has a cut surface (a third side) cut at an angle θ with respect to a semi-transparent mirror surface (one side 21 in FIG. 3).
In the figure, the other side 22) is placed on the semiconductor substrate 10, and the cut surface is adhesively fixed to the semiconductor substrate 10 with an adhesive. This adhesive is a transparent medium, and is selected to have the same refractive index as the light splitter 2, for example, a UV curing type. Therefore, even if the cut surface is not particularly polished, the uneven portions are filled with adhesive, and light scattering and reflection on the cut surface (other side surface 22) is eliminated.

(C) Mounting aspect of a light emitting element according to an embodiment of the present invention FIG. 6 shows a schematic perspective view of a semiconductor laser. FIG. 7 (
Shown in A) and (B).

In each of the above figures, the semiconductor laser 1 is placed on the mounting land 11 of an aluminum electrode formed by vapor deposition on the semiconductor substrate 10, and the side electrodes 1a, lb and the mounting land 11 are bonded and fixed by soldering. . The gap 11b between the soldered semiconductor laser 1 and the semiconductor substrate 10 is formed by the protrusion of the mounting land 11, and the semiconductor laser 1 is in direct contact with the semiconductor substrate 10 itself to prevent a short circuit. It prevents it from happening. Further, in addition to the protrusion of the mounting land 11, an insulating material may be deposited in the gap 11b to prevent a short circuit of the semiconductor laser.

Figure 8 shows the semiconductor laser 1 mounted on the mounting land 11.
The mounting land 11 forming the aluminum electrode is formed to have a larger area 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 dissipation characteristics of the semiconductor laser 1 are improved.

FIG. 9 shows a plan view of the semiconductor substrate 10 on the lower surface on which the semiconductor laser 1 is mounted, and in this figure, a monitor light receiving element 7 is formed on the lower surface on which the semiconductor laser 1 is mounted.

FIGS. 10(A) and 10(B) show the semiconductor substrate 1 in the same way as FIG. 9.
0 is shown. In the same figure (A), the semiconductor laser 1
In this configuration, a diffraction grating 3 is formed on the lower mounting surface of the semiconductor laser 1, and a diffraction grating 3 and a monitor light receiving element 7 are formed on the lower mounting surface of the semiconductor laser 1 in FIG.

FIG. 11 shows an explanatory view for attaching the main parts of the semiconductor laser 1 to the semiconductor substrate 10, and in the same figure, it is formed as a mounting land 11 having a stepped portion 11a on the semiconductor substrate 10. As shown in FIG.

In this way, the stepped portion 11a of the mounting land 11 makes it easy to locate the mounting position by bringing the semiconductor laser 1 into contact with the stepped portion 11a, allowing the mounting work to be performed quickly and with high precision.

FIGS. 12A, 12B, and 12C are explanatory diagrams for attaching the main parts of the semiconductor substrate 10 to the side surface of the semiconductor substrate 10. FIG. The same figure (A
), the semiconductor laser 1 was connected and fixed to the side surface of the semiconductor substrate 10 with an adhesive 15, whereas in the same figure (B)
As shown in (C), a mounting land 11 as an electrode is formed to extend to the side surface of the semiconductor substrate 10, and the electrodes 1a and lb of the semiconductor laser 1 are abutted and fixed to the extended mounting land 11. It is also possible to do this.

FIGS. 13(A) and 13(B) show schematic perspective views of a mounting base for a semiconductor laser. In the same figure (A) and (B), the mounting base 1
00 is a non-conductive substance 101 and a conductive substance 101a, 10
1. Form by sandwiching it with b. The semiconductor laser 1 is placed on this mounting base 100, or is sandwiched and soldered to be adhesively fixed.

In this manner, the semiconductor laser 1 can be easily mounted to another member, for example, the semiconductor substrate 10, via the mounting base 100.

FIG. 14 shows a modified mounting mode of the mounting base 100 shown in FIG. This means that laser light can be emitted in the direction of the arrow. Further, by forming the upper surface or the lower surface of the mounting base 100 with an inclination, the laser light output can be emitted diagonally upward and downward.

(d) Other embodiments of the present invention The light splitter 2 has a structure in which only one side surface 21 is polished to form a semi-transparent mirror, but the other side surfaces 23 and 26 (see FIG. 3) are coated with an antireflection film. It can also be formed. This anti-reflection film emits stray light such as scattered light to the outside of the light splitter 2 and prevents unnecessary laser light (laser light other than the reflected light from the optical disc 20) from entering the first light receiving element 5. , to further improve the effective use of laser light.

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 a where n2 is the refractive index of the light splitter 2, n2o is the refractive index of the adhesive layer, n24 is the refractive index of the cladding layer 24, and n3 is the refractive index of the diffraction grating. be.

In this way, by sequentially setting the refractive index smaller in the direction of incidence 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 diffraction means is constructed from two regions, but it can also be constructed from two or more regions.

In each of the embodiments described above, the optical diffraction means is constituted by a diffraction grating, but it can also be constituted by a stepped grating or other diffraction means, or by various optical elements that branch and emit incident light to an optical waveguide and a first light receiving element on the lower surface.

〔Effect of the invention〕

As explained above, in the present invention, the light from the light emitting means is reflected to the optical information recording carrier side by one side of the light splitting means, and the light reflected from the optical information recording carrier side is refracted and transmitted by one side. This incident light passes through the other side and is separated into transmitted light and diffracted light by the diffraction action of the light diffraction means. This allows light to be guided within the optical waveguide, which facilitates processing operations during the manufacture of the optical splitter and has the effect of making the entire device smaller.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is an overall side view of an embodiment of the invention, Fig. 3 is a configuration diagram of essential parts of an embodiment of the invention, and Fig. 4 is the description shown in Fig. 3. 5 is an explanatory diagram of a method of manufacturing a light splitter in an embodiment of the present invention; FIG. 6 is a schematic perspective view of a semiconductor laser installed in an embodiment of the present invention; Figures 7 (A) and (B) are explanatory diagrams of the mounting state of the semiconductor laser, Figures 8 and 9 are plan views of the semiconductor substrate of the mounting land forming part, and Figures 10 (A) and (B) are the semiconductor substrate 11, 12(A), 11(A), 12(A), 12(A), 11(A), 12(A), 12(A), 12(A), 12(A), 12(A), 12(A), 12(A), 12(A) (B) a plan view of the semiconductor substrate of the diffraction grating and mounting land forming part; (B) and (C) are explanatory diagrams for attaching a semiconductor laser to a semiconductor substrate, and Fig. 13 (A) and (B
), FIG. 14 is an explanatory diagram of a mounting base for mounting a semiconductor laser, FIG. 15 is a schematic perspective view of a conventional optical pickup device, and FIG. 16 is a side view of essential parts of a conventional optical pickup device. 1... Semiconductor laser (light emitting means) 2... Light splitter (light splitting means) 3... Diffraction grating (light diffraction means) 4... Optical waveguide 5... First light receiving element 6...・Second light receiving element 7...Monitor light receiving element 10...Semiconductor substrate 20...Optical disc 30...Pickup body 31...Objective lens

Claims (1)

[Claims] 1. Formed of a semiconductor substrate (10), the semiconductor substrate (
10) Light that emits light emitted from the light emitting means (1) placed on the optical information recording carrier on which recorded information is recorded, and receives the light reflected by the optical information recording carrier. The pickup device is placed on the semiconductor substrate (10) and includes the light emitting means (
1) is reflected to the optical information recording carrier side by one side surface (21), and the light reflected by the optical information recording carrier is transmitted through the one side surface (21) and enters the other side surface (22). a light splitting means (2) for guiding waves; and a light splitting means (2) formed in the semiconductor substrate (10) for separating light emitted from the other side surface (22) of the light splitting means (2) into transmitted light and diffracted light. An optical pickup device comprising: an optical diffraction means (3). 2. The optical pickup device according to claim 1, further comprising a core layer in the semiconductor substrate (10) and the optical diffraction means (
An optical waveguide (4) is formed between the optical waveguide (3) and the optical waveguide (4).
A first light-receiving element is formed on a side surface of the core layer that is not adjacent to 4), a second light-receiving element is formed at the end of the optical waveguide (4), and the light transmitted through the light diffraction means (3) is received by the first light-receiving element. In addition to receiving the light with the element, the diffracted light of the optical diffraction means (3) is transmitted to the optical waveguide (4).
An optical pickup device that receives light through a second light receiving element. 3. In the optical pickup device according to claim 1, the light splitting means (2) is made of an adhesive material made of a transparent medium having approximately the same refractive index as the light splitting means (2) on the other side (22).
) is adhesively fixed onto a semiconductor substrate (10). 4. The optical pickup device according to claim 1, wherein the refractive index of the adhesive bonding the light splitting means (2) is approximately equal to the refractive index of the light splitting means (2), and the semiconductor substrate (10
) is made larger than the refractive index of the cladding layer formed thereon,
The light emitted from the light emitting means (1) is directly transmitted to the light dividing means (
2) The light transmitted through the surface of the one side surface (21) is totally reflected on the surface of the cladding layer, and is reflected by the optical information recording carrier to form the surface of the one side surface (21) of the light splitting means (2). An optical pickup device characterized in that the light transmitted through the cladding layer is transmitted through the cladding layer. 5. The optical pickup device according to claim 1, wherein the optical diffraction means (3) is constituted by a diffraction grating formed adjacent to the optical waveguide (4) layer of the semiconductor substrate (10). Optical pickup device. 6. The optical pickup device according to claim 1, wherein the light diffraction means (3) is formed of at least two regions, and the amount of transmitted light is greater than the amount of diffracted light. 7. The optical pickup device according to claim 1, further comprising a light emitting means (1) placed on the semiconductor substrate (10).
is formed by emitting light from a surface that is placed in contact with the semiconductor substrate (10) and providing electrodes on both sides adjacent to the surface from which the light is emitted, and is provided on the semiconductor substrate (10). An optical pickup device characterized in that the end portion of the electrode is directly contact-connected to the land portion.