JPH09283853A - Semiconductor laser module and optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produe a semiconductor laser module incorporated in a unit with a semiconductor laser diode ship and photo detecting element for return lights in a simple structure at low cost. SOLUTION: A semiconductor laser module 1 comprises a semiconductor substrate 3, a spacer 4 and a transparent plate 5 laminated up in this order on a tilted substrate holding face 21 of a metal support 2. These members 3, 4, 5 can be positioned by butting them against a vertical position surface 22. The semiconductor substrate 3 is incorporated with a photo-diode 7 for the output control of a laser beam and a photo diode 8 for detecting a return light to obtain a tracking error signal, etc. A laser diode chip 6 is mounted on a laser chip hold surface 23 on the upper face of the support 2. Since the components 3, 4, 5 are incorporated by only laminating them up, the manufacturing is simple and low in cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for reproducing / recording an optical recording medium and / or performing one of the operations. More specifically, the present invention relates to a semiconductor laser module in which a laser light source and a photodetector of the optical pickup are integrated.

[0002]

2. Description of the Related Art An optical pickup for reproducing an optical recording medium such as a compact disk (CD) collects light emitted from a laser diode as a laser light source on a recording surface of the optical recording medium via an objective lens. And the return light from the recording surface is read by a photodetector. In addition, a mechanism is built in which the position of the objective lens can be finely corrected in the tracking direction and the focusing direction so that the emitted light is accurately focused on the target track on the recording surface via the objective lens. In order to perform such correction of the tracking direction and the correction of the focusing direction, for example, a diffraction grating such as a hologram optical element is used to diffract outgoing light into three beams, and perform tracking from return light from the optical recording medium. A servo control signal for correction and a servo control signal for focusing correction are obtained.

In order to realize the reduction in size and weight of the optical pickup, improvements have been made in reducing the size and weight of its constituent elements. Among them, a configuration has been proposed in which a laser light source and a photodetector are integrally assembled to reduce the size and weight.

For example, in Japanese Patent Laid-Open No. 4-159627, a semiconductor laser chip which is a laser light source, a photodiode which is a photodetecting element for tracking, a photodiode which is a photodetecting element for focusing, and an objective lens are integrated. Optical heads are disclosed. This optical head has a flat plate material having a reflective film formed on the front surface, and a substrate arranged in parallel on the back surface side with an air layer having a constant thickness interposed therebetween. A photodiode is mounted on this substrate. It is composed. The return light from the optical recording medium passes through the flat plate material and the air layer and is detected by the tracking photodiode. Part of the returned light is reflected by the reflective film formed on the front surface of the photodiode, then reflected on the back surface of the flat plate material, and again travels toward the substrate side, and is detected by the focusing photodiode formed on the substrate. It has become so. In this way, the return light is repeatedly reflected by sandwiching the air layer between the flat plate material and the substrate and detected by the focusing photodiode.

Further, Japanese Utility Model Laid-Open No. 12221/1989 discloses an optical pickup in which a laser light source and a photo-detecting element group are integrated. This optical pickup has a three-layer structure including a substrate on the surface of which a group of photodetectors is formed, a transparent plate stacked on the substrate, and a submount plate stacked on the substrate. Half mirror and full mirror are formed on the surface of the central transparent plate on the submount plate side,
The emitted light passes through the half mirror and is received by the photodetector element for controlling the laser output. The return light from the optical recording medium is partially detected by the photodetector for focusing correction after passing through the half mirror, and the rest is reflected by the surface of the photodetector and is reflected by the full mirror on the surface side of the transparent body. The light is reflected again on the substrate side and detected by the photodetection element for tracking correction. In this way, the return light is repeatedly reflected between the surface of the substrate and the surface of the transparent plate and reaches the photodetection element for tracking correction.

[0006]

In the optical head or optical pickup having the above-mentioned structure, the returning light is repeatedly reflected and detected by the light receiving element for focusing correction or the light receiving element for tracking correction. Therefore, it is necessary to make the parallelism between the reflecting surfaces highly accurate. Further, it is necessary to increase the surface accuracy of each reflecting surface. Therefore, since it is necessary to manufacture and assemble each member with high accuracy, there is a problem that the manufacturing cost becomes high and the assembly cannot be performed easily.

An object of the present invention is to realize a semiconductor laser module having a structure in which a semiconductor laser chip and a photodetection element group are integrally incorporated, which can solve such a problem. Another object of the present invention is to propose an optical pickup using this semiconductor laser module.

[0008]

In order to solve the above problems, a semiconductor laser module of the present invention is mounted on a support body having a laser chip holding surface and a substrate holding surface and the laser chip holding surface. A semiconductor laser chip, a semiconductor substrate mounted on the substrate holding surface, a first light receiving element and a second light receiving element formed on the semiconductor substrate, a spacer stacked on the semiconductor substrate, and a spacer The transparent plate formed by the first light receiving element and the transparent plate and the spacer is adopted, which has a transparent plate stacked on the transparent plate and a reflecting surface formed on the surface of the transparent plate. And receiving the emitted light from the semiconductor laser chip that has passed through the air layer between the semiconductor substrate,
The second light receiving element receives the return light from the optical recording medium that has passed through the transparent plate and the air layer.

In the semiconductor laser module having this structure,
The emitted light from the semiconductor laser chip and the returned light from the optical recording medium pass through the transparent plate and the air layer to reach each light receiving element. Since an optical path that is repeatedly reflected and reaches each light receiving element is not formed, parallelism, surface accuracy, assembly accuracy, etc. of each component are not required as much as in the past.

Further, according to the present invention, the semiconductor substrate, the spacer and the transparent plate can be assembled by simply stacking them in this order on the substrate holding surface of the support.

Particularly, when the support body has the alignment surface for defining the superposition position of the semiconductor substrate, the spacer and the transparent plate, the assembling of these members can be easily performed.

In a preferred embodiment of the present invention, the substrate holding surface is an inclined surface, and the semiconductor substrate, the spacer, and the transparent plate placed on the inclined surface have the lower end in the inclined direction of the inclined surface. It is configured to align these members by abutting the alignment surface of.

Here, the substrate holding surface and the alignment surface may be formed so as to be orthogonal to each other, and the laser chip holding surface side may be inclined with respect to the substrate holding surface.

Next, in order to make the assembling work easier and to reduce the number of parts, the transparent plate and the spacers may be constructed as one body. For example, these may be integrally formed by a glass mold, a resin mold, or the like.

On the other hand, the above-mentioned support can be used as a heat radiating material for radiating heat generated by the semiconductor laser chip. With this configuration, the heat generated by the semiconductor laser chip can be efficiently released.

Further, it is desirable that the spacer is provided with a communicating portion for communicating the air layer formed by the spacer to the outside. With this configuration, even if the air layer expands or contracts due to temperature change, the internal pressure does not fluctuate because of the communicating portion.
Therefore, even if the ambient temperature changes, the influence does not affect the upper and lower transparent plates and the semiconductor substrate.

Further, an electronic circuit for signal processing can be built in the above semiconductor substrate. By doing this, compared to the case where an electronic circuit for signal processing is externally attached,
The semiconductor laser module can be made compact and compact.

Next, in the semiconductor laser module having the above structure, a hologram element for diffracting the emitted laser light into a plurality of light beams and a plurality of light beams obtained through the hologram element are spotted on a recording medium. And an objective lens for converging light as a 1 / for allowing the return light from the optical recording medium to pass through without being diffracted by the holograc element.
It is suitable for use in an optical pickup device that has a four-wavelength plate and detects a plurality of return lights with a photodetector, thereby detecting a focusing error signal, a tracking error signal, and the like.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a semiconductor laser module to which the present invention is applied will be described with reference to FIGS.

The semiconductor laser module 1 of this example comprises a support 2 made of aluminum, iron or copper having good thermal conductivity. A groove having a substantially triangular cross section defined by a rectangular inclined surface 21 and a rectangular vertical surface 22 is formed on the support 2. The inclined surface 21 is, for example, an inclined surface of 45 degrees and functions as a substrate holding surface, and the vertical surface 22 functions as an alignment surface. The semiconductor substrate 3 having a constant thickness is placed on the substrate holding surface 21, which is an inclined surface. Spacers 4 having a constant thickness are stacked on the semiconductor substrate 3. The spacer 4 has a transparent plate 5 of a certain thickness.
Are stacked. On the other hand, on the support 2, a horizontal plane continuous to the upper edge of the alignment surface 22, which is a vertical surface thereof, is formed as a laser chip holding surface 23. A laser diode chip 6 as a laser light source is mounted on the laser chip holding surface 23.

Semiconductor substrate 3 on substrate holding surface 21
Is the laser diode chip 6 at the center of its surface.
The photodiode 7 for detecting the light for adjusting the output of the laser light emitted from is manufactured by the semiconductor manufacturing process. In addition, on the surface of the semiconductor substrate 3,
The photodiodes 8 (81 to 85) are arranged on the side closer to the alignment surface 22 than the photodiode 7 in a direction parallel to the alignment surface 22. For example, as shown in the drawing, five photodiodes 81 to 85 are arranged. Of these, the photodiodes 82 to 85 other than the photodiode 81 located at the center have two light-receiving surfaces.
It is a two-division photodiode having a divided configuration. The photodiode 8 detects a tracking error signal, a focusing error signal and a high frequency signal. This photodiode 8 is also built in the semiconductor substrate 3 by the semiconductor manufacturing process.

The spacer 4 located on the semiconductor substrate 3 is a rectangular frame having a rectangular window 41 for light passage in the center, as shown by the hatched area in FIG. is there. Therefore, an air layer 9 (see FIG. 2A) having a constant thickness surrounded by the spacer 4 is defined between the semiconductor substrate 3 and the transparent plate 5 which are superposed with the spacer 4 interposed therebetween. ing. The photodiodes 7 and 8 formed in the semiconductor substrate 3 face the back surface of the transparent plate 5 via the air layer 9. In this example, a part of the rectangular frame-shaped spacer 4 is cut off. When the cut is formed with the separated portion 42, the air layer 9 defined by the spacer 4 is in a state of communicating with the outside through the separated portion 42. That is, the separated portion 42 functions as a communication portion. Next, the surface of the transparent plate 5 located at the top is a partial reflection surface 51 coated with a partial reflection film.

The semiconductor substrate 3, the spacer 4 and the transparent plate 5 stacked on the substrate holding surface 21 are aligned with the upper sides 35, 45 and 55 of the end faces located below the inclined direction. It has come into contact with the surface 22. In this way, by abutting each member against the alignment surface 22, these members are aligned in the plane direction.

Next, the laser beam L emitted from the laser diode chip 6 mounted on the edge of the laser chip holding surface 23 is set so that its optical axis Lo is oriented in the horizontal direction. The laser light L emitted in the horizontal direction irradiates the partial reflection surface 51 on the surface of the transparent plate 5 that is inclined at 45 degrees, and about half the laser light is reflected vertically,
It goes to the side of the optical recording medium (not shown). About the other half of the laser light passes through the transparent plate 5 on which the partially reflecting surface 51 is formed, passes through the air layer 9 on the back surface side of the transparent plate 5, and is formed on the surface of the semiconductor substrate 3. The light receiving surface of the existing photodiode 7 is illuminated. On the other hand, the return light Lr emitted to the optical recording medium side and reflected by the optical recording medium returns along the same optical path as the emitted light L and enters the transparent plate 5. The return light that has passed through the partial reflection surface 51 on the front surface of the transparent plate 5 passes through the transparent plate 5 and the air layer 9 on the rear surface side thereof, and the semiconductor substrate 3
The photodiode 8 built in the surface of the is irradiated.

The semiconductor laser module 1 having this structure is
It is used as a semiconductor laser unit 11 by being enclosed in a package 10 having the shape shown in FIG. Package 10
Is provided with a support substrate (stem) 13 and a cup-shaped sealing cap 14 mounted thereon. Support substrate 13
The semiconductor laser module 1 having the above-described configuration is mounted on the surface of, and the module 1 is sealed by covering the sealing cap 14. Here, the above-mentioned semiconductor laser module 1
The semiconductor substrate 3 is provided with a large number of bonding pads (not shown) for taking out signals from the photodiodes 7 and 81 to 85, for example, on the outer peripheral end face thereof. These bonding pads are package 10
Attached to the back surface of the support substrate 13 on the side of the
, So that the connection relationship is set in advance,
It is electrically connected by a connection method such as wire bonding.

In the semiconductor laser module 1 of this example having the above-described structure, the return light Lr is transmitted through the transparent plate 5 and the semiconductor substrate 3.
The light is directly reflected by the photodiodes 7, 81 to 85 formed on the surface of the semiconductor substrate 3 without being reflected by the light. Therefore, as compared with the conventional case where the return light is reflected between the members and received by the light receiving element and detected, the optical path of the return light is simpler, so that the work of aligning each component can be performed easily. Can be done.

Further, in the assembling work of the respective constituent members of the semiconductor laser module 1 of this example, the semiconductor substrate 3, the spacer 4 and the transparent plate 5 are sequentially arranged on the inclined substrate holding surface 21 of the support 2. And the lower sides 35, 45, 55 of them in the inclination direction are vertically aligned with each other.
When the two are abutted against each other, these respective constituent members are aligned with each other. Therefore, the position of each component can be easily aligned. It should be noted that the respective constituent members after being aligned are fixed to each other with an adhesive or the like, and are fixed on the substrate holding surface 22.

Further, in this example, the separating portion 42 is formed in the spacer 4 to communicate the air layer 9 to the outside.
As a result, even if the ambient temperature changes and the air layer expands or contracts, the pressure of the air layer does not change. For this reason, the ambient temperature does not fluctuate, and the position of each component changes due to the expansion of the air layer or the like.

Furthermore, in this example, since the support 2 is made of a metal material having good thermal conductivity, it also functions as a heat sink for the laser diode chip. Therefore, the heat generated by the laser diode chip can be efficiently emitted. The support body 2 can be produced by cutting a metal rod material after grooving. Alternatively, it may be produced by casting.

On the other hand, in the semiconductor laser module 1 of this example, if the transparent plate 5 is thin, the astigmatism generated in the return light Lr can be reduced. As a result, it is possible to accurately detect light by the photodiode groups 81 to 85. Further, if the transparent plate 5 is thinned, the laser diode chip 6, the transparent plate 5, and the photodiodes 7 and 8 can be arranged close to each other. In this way, the photodiode 7 of this example has a structure for directly irradiating the laser light L which is divergent light. However, without using an optical element for converging the light flux such as a condenser lens, Most of the laser light flux can be received by the light receiving surface of the photodiode 7 without making the surface large.

Further, in this example, the transparent plate 5 and the spacer 4 are constructed as separate members. If these members are integrated by glass molding, resin molding, etc., the number of parts is reduced and the assembling work is simplified.

Further, an I / V conversion circuit or the like for converting the detection output current from each photodiode 7, 8 into a voltage can be built in the semiconductor substrate 3 by a semiconductor manufacturing process. For example, a signal processing circuit shown in FIG. 9 described later can be built in. With this configuration, the semiconductor laser unit can be made smaller and more compact than when these signal processing circuits are externally provided. Also,
The wiring between the light receiving part and the conversion circuit can be shortened, and S /
The N can be improved.

(Modification of Semiconductor Laser Module) FIG.
Shows a modification of the above semiconductor laser module. The semiconductor laser module 20 shown in this drawing has the same basic configuration as the module 1 described above, and therefore, corresponding parts are designated by the same reference numerals and description thereof is omitted. In this example, in the semiconductor laser module 20, the substrate holding surface 21 is a horizontal surface and the laser holding surface 23 is an inclined surface. Further, since the substrate holding surface 21 is a horizontal surface, the alignment surface 22 continuous to the end is a vertical surface. Thus, even if the substrate holding surface 21 is a horizontal surface and the laser chip holding surface 23 is an inclined surface, the same effect as that of the module 1 can be obtained.

(Optical Pickup) FIG. 5 shows an example of an optical system of an optical pickup in which the semiconductor laser module 1 (see FIGS. 1 to 3) described above is incorporated.

In the optical system of the optical pickup of this example, a linear optical path is formed between the semiconductor laser module 1 (semiconductor laser unit 11) and the optical recording medium 31. The semiconductor laser module 1 is placed on this linear optical path.
From the side, the hologram element 32, the quarter-wave plate 33, and the objective lens 34 are arranged in this order. The hologram element 32 is formed on the surface of a glass substrate 35 arranged substantially perpendicular to the optical axis Lo.

Emitted light L from the semiconductor laser module 1
Passes through the glass substrate 35 and is divided into five light beams by the hologram element 32. These split lights are
It is guided to the objective lens 34 via the quarter-wave plate 33, and is focused as five light spots on the recording surface of the optical recording medium 31 via the objective lens 34. In this way, the recording medium 31
The return lights of the five light beams reflected by the recording surface of (1) are reflected by the recording surface and again pass through the quarter-wave plate 33 via the objective lens 34. The plane of polarization of the return light is rotated 90 degrees by the quarter-wave plate 33. Therefore, it passes through the hologram element 32 as it is and returns to the semiconductor laser module 1 through the glass substrate 35. The five light beams returned to the semiconductor laser module 1 are five photodiodes 8 (81 to 85) formed on the semiconductor substrate 3.
Then, the focusing error signal, the tracking error signal and the RF signal are detected.

On the other hand, as described with reference to FIGS. 1 and 2, part of the emitted light L is part of the semiconductor laser module 1.
At, the light is received by the photodiode 7 formed on the semiconductor substrate 3. The output control of the laser diode 6 is performed based on the detection signal of the photodiode 7. That is, the light amount of the emitted light L is adjusted.

As described above, in this example, the signal is detected by dividing the emitted light into five light beams by the hologram element 32.

The operation of the hologram element 32 and the principle of signal detection will be described with reference to FIGS. 6 to 9.

First, as shown in FIG. 6, the hologram element 32 is divided into two parts by a dividing line extending in a direction substantially orthogonal to the direction along the track of the recording medium 31 on the optical axis Lo. A pair of diffraction gratings (irregular gratings) 32A and 32B having different diffraction conditions are formed on the dividing line. These diffraction gratings 32A and 32B have different grating intervals and grating directions.

The position on the recording surface where the diffracted 0th-order and 1st-order diffracted light beams are converged by the action of the hologram element 32 will be described with reference to the principle diagram of FIG. Of the light beam emitted from the semiconductor laser module 1 and incident on the upper hologram element 32A, the 0th-order light that is not diffracted passes through the diffraction grating 32A, enters the objective lens 34, and converges to a point L '. The diffracted first-order light that has been diffracted is incident on the objective lens 34 as if there are light sources in the virtual images A + and A− having optical axis symmetry with the position L1 of the semiconductor laser module 1 as the center, and the points A ′ + and A '-Converge. That is, the light beam emitted from the diffraction grating 32A is, by the objective lens 34, a point L1 ′ conjugate with L1 for the 0th-order light.
For the primary light, the conjugate points A '+, A'of A +, A-
Each of the negative values converges to a corresponding position (conjugate point) on the recording surface.

The light beam emitted from the semiconductor laser module 1 and incident on the lower diffraction grating 32B in FIG. 6 can be considered in exactly the same manner. For the 0th order light, at the point L1 ′ conjugate with L1, for the 1st order light B
It converges on the conjugate points B '+ and B'- of + and B-, respectively.
Therefore, the light emitted from the semiconductor laser module 1 becomes a zero-order diffraction light beam and a first-order diffraction light beam by the action of the upper and lower diffraction gratings 32A and 32B of the hologram element 32. The light spots converge as five light spots L ′, A ′ +, A′−, B ′ +, and B′− on the recording surface.

FIG. 7 shows a state in which the formed light spot is viewed from the direction perpendicular to the recording surface of the optical recording medium 31. The light spot 100 at the center of the track 311 is the diffracted 0th order light, and the other 4 points are the ± 1st order diffracted lights. The light beam that has passed through the portion of the hologram element 32 where no diffraction grating is provided converges on the same light spot as the zero-order diffracted light. Here, diffraction 1 of diffraction grating 32A
The next light spots 101 and 103 are the central light spot 100
The position is point-symmetrical with respect to, and the diffraction of the diffraction grating 32B 1
The next light spots 102 and 104 are also at the center light spot 100.
Is symmetric with respect to the point. Each spot position determines each grating interval and grating direction of each of the diffraction gratings 32A and 32B, so that each first-order diffracted light can be converged at an appropriate position on the track. Further, the approximate shape of the light spot of the first-order diffracted light is obtained as a Fourier transform of each diffraction grating aperture shape.

Next, the photodiode 8 which is a photodetector
The light spot received at (81 to 85) will be described. The light spot on the recording surface of the optical recording medium 31 is reflected by the optical recording medium 31, passes through the objective lens 34 again, and is re-imaged on the focal plane on the side of the photodiode 8.
The positional relationship of the light spots on the focal plane on the side of the photodiode 8 is conjugate with the positional relationship of the light spots on the recording surface. Therefore, when the positional relationship between the objective lens 34 and the optical recording medium 31 moves in the optical axis direction or the direction perpendicular to the optical axis, the spot position and the spot shape are shifted between the recording surface and the focal plane on the photodiode group 8 side. Change as well.

With reference to FIG. 8, a change in the positional relationship between the objective lens 34 and the optical recording medium 31 in the optical axis direction, that is, a change in the light spot on the side of the photodiode 8 with respect to a focus shift will be described.

At the focal point, as shown in FIG. 8B, the light spots 201 and 203 of the diffractive first-order light of the diffraction grating 32A and the diffraction grating 32B centering on the light spot 200 of the zero-order light are used.
The light spots 202 and 204 of the first-order diffracted light are located above and below, and all form the smallest light spot. And
The light spot 200 is located at the center of the light receiving surface 81a of the photodiode 81 at the center, and the light spots 201 to 2 of the first-order diffracted light
Reference numeral 04 is located at the center of the dividing line of the two-divided light-receiving surface of the two-divided photodiodes 82 to 85 arranged in a line on both sides of the photodiode 81.

On the other hand, when the distance between the objective lens 34 and the optical recording medium 31 becomes short, the light spot 200 of the 0th-order light has no change in position and has a large diameter, as shown in FIG. 8A. The light spot 201 of the primary diffraction light of the diffraction grating 32A,
Reference numeral 203 shows a shape similar to the opening shape of the diffraction grating 32A, and its center moves upward in FIG.

The light spots 202 and 204 of the first-order diffracted light of the diffraction grating 32B become larger in shape similar to the aperture shape of the diffraction grating 32B, and the centers thereof move to the lower side in FIG. As a result, the light spots 201 to 20 of the diffracted primary light
Most of 4 is located on one side of each of the two-divided photodiodes 82 to 85. Since FIG. 8 shows an ideal state, the light spot is located only on one side, but in reality, a part is also located on the other side due to blurring or the like.

Contrary to the above, when the distance between the objective lens 34 and the optical recording medium becomes long, as shown in FIG. 8C, the light spot 200 of the 0th order light has no change in position and its diameter. Grows larger. The light spots 201 and 203 of the 1st-order diffracted light of the diffraction grating 32A grow in a shape similar to the upside-down opening shape of the diffraction grating 32A, and the centers thereof move to the lower side of FIG. Light spot 20 of the primary diffraction light of diffraction grating 32B
The centers of the reference numerals 2 and 204 move to the upper side in FIG. 8 while increasing in size to resemble the inverted shape of the diffraction grating 32B.

Therefore, as shown in FIG. 9, among the outputs of the photodiodes 81 to 85, the outputs of the two-divided photodiodes 82 and 83 and the two-divided photodiodes 84 and 8 are shown.
By comparing the output of No. 5 upside down with comparators 401 and 402 and comparing the result with comparator 403, a focusing error signal (FE signal) can be obtained.

On the other hand, as in the case of the ordinary three-beam method, as shown in FIG. 9, the outputs of the two-divided photodiodes 82 and 83 are added by the adders 404 and 405, respectively. , The result is the comparator 4
By performing the comparison at 06, a tracking error signal (TE signal) can be obtained. The tracking error signal can be obtained only from the outputs of the two-divided photodiodes 82 and 84 or the outputs of the two-divided photodiodes 83 and 85.

Regarding the RF signal, only the beam diameter of the 0th order light increases or decreases depending on the degree of focusing, and the spot is always located on the light receiving surface of the photodiode 81. An RF signal is detected based on the output of the photo diode 81.

(Another Example of Optical Pickup) FIG.
Another example of an optical system of an optical pickup in which the semiconductor laser module 1 is incorporated is shown. In the optical system shown in this figure, a hologram element 32 having the same configuration as described above is arranged between a total reflection mirror 37 and a quarter-wave plate 33.
Therefore, the light emitted from the semiconductor laser module 1 has its optical path raised by the total reflection mirror 37 and is guided to the hologram element 32. The emitted light is diffracted by the hologram element 32 and divided into five light beams, and the divided light is guided to the objective lens 34 via the quarter-wave plate 33 and is divided into five light beams on the recording surface of the optical recording medium 31. It converges as a light spot. The return light reflected from the recording surface of the optical recording medium 31 reaches the quarter-wave plate 33 via the objective lens 34, passes therethrough, and the plane of polarization is rotated by 90 degrees. Therefore, the return light passes through the hologram element 32 that diffracts only specific polarized light, reaches the total reflection mirror 37, is reflected there, and returns to the semiconductor laser module 1. The light detection operation in this example is the same as in the above case.

[0054]

As described above, the semiconductor laser module of the present invention can be constructed by stacking the semiconductor substrate, the spacer and the transparent body on the substrate holding surface formed on the support plate. Further, the returned light is directly detected by the light receiving element (photodiode) formed on the semiconductor substrate without being reflected by each of these members. Therefore, according to the present invention, there is an advantage that it can be easily manufactured, and that the parallelism, surface accuracy, etc. of the respective constituent members are not required as in the conventional case.

Further, according to the present invention, the positioning of the constituent members stacked on the substrate holding surface can be easily performed by the positioning surface formed on the support. Therefore,
According to the present invention, each member can be easily assembled.

Further, in the present invention, the transparent plate and the spacer, which are the components, are integrated. If you do this,
Assembly work can be further simplified.

Next, in the present invention, since the support body is made of a heat radiation material for radiating the heat of the semiconductor laser chip, the heat of the semiconductor laser chip can be efficiently radiated.

Further, in the present invention, the spacer is provided with a communicating portion for communicating the air layer formed by the spacer to the outside. If you do this,
Even if the air layer expands or contracts due to temperature change, the internal pressure does not fluctuate because there is a communicating portion. Therefore, even if the ambient temperature changes, the influence does not affect the upper and lower transparent plates and the semiconductor substrate.

Furthermore, in the present invention, an electronic circuit for signal processing is built in the semiconductor substrate. With this configuration, the semiconductor laser module can be made compact and compact as compared with the case where an electronic circuit for signal processing is externally attached.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a semiconductor laser module to which the present invention is applied.

2A is a schematic sectional view of the module of FIG. 1,
FIG. 3B is an explanatory diagram showing the shapes of the semiconductor substrate and the spacer.

3 is a side view of a semiconductor laser unit in which the module of FIG. 1 is enclosed.

FIG. 4 is a diagram showing a modification of the module shown in FIG.

5 is a schematic configuration diagram showing an example of an optical system of an optical pickup in which the module of FIG. 1 is incorporated.

6A and 6B are explanatory views for explaining the operation of the hologram element of FIG.

FIG. 7 is an explanatory diagram showing positions of light spots formed on an optical recording medium.

FIG. 8 is an explanatory diagram showing a state of a light spot of return light formed on the light receiving surface of the photodiode.

FIG. 9 is a schematic block diagram showing a circuit configuration for generating a focusing error signal, a tracking error signal, and an RF signal based on the output of the photodiode.

10 is a schematic configuration diagram showing another example of an optical system of an optical pickup in which the module of FIG. 1 is incorporated.

[Explanation of symbols]

1 Semiconductor Laser Module 2 Support 21 Substrate Holding Surface 22 Alignment Surface 23 Laser Holding Surface 3 Semiconductor Substrate 4 Spacer 5 Transparent Plate 51 Partially Reflective Surface 6 Laser Diode Chip 7 Photodiode 8 for Output Adjustment Photodiode 81 for Detection of Return Light 81 Center Photodiode 82, 83, 84, 85 2-divided photodiode 81a Light-receiving surface 82a to 85a, 82b to 85b 2-divided photodiode light-receiving surface L Emitted light Lr Return light Lo Optical axis

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisahiro Ishihara 5329 Shimo-Suwa Town, Suwa-gun, Nagano Sankyo Seiki Co., Ltd. (72) Inventor Kazuo Kobayashi 5329 Shimo-Suwa Town, Suwa-gun, Nagano Sankyo Seiki Co., Ltd. (72) Inventor Kenichi Hayashi 5329 Shimosuwa Town, Suwa District, Nagano Prefecture Sankyo Seiki Co., Ltd.

Claims (9)

[Claims] 1. A support having a laser chip holding surface and a substrate holding surface, a semiconductor laser chip mounted on the laser chip holding surface, a semiconductor substrate mounted on the substrate holding surface, and a semiconductor substrate on the semiconductor substrate. Formed first light receiving element and second light receiving element, a spacer stacked on the semiconductor substrate, a transparent plate stacked on the spacer, and a reflecting surface formed on the surface of the transparent plate. And the first light receiving element receives light emitted from the semiconductor laser chip that has passed through the transparent plate formed by the spacer and the air layer between the transparent substrate and the semiconductor substrate. The semiconductor laser module is characterized in that the second light receiving element is adapted to receive return light from the optical recording medium which has passed through the transparent plate and the air layer. 2. The semiconductor laser module according to claim 1, wherein the support has an alignment surface for defining an overlapping position of the semiconductor substrate, the spacer, and the transparent plate. 3. The substrate holding surface according to claim 2, wherein the substrate holding surface is an inclined surface, and the semiconductor substrate, the spacer, and the transparent body placed on the inclined surface have lower ends in the inclination direction of the inclined surface. A semiconductor laser module in which these members are aligned by hitting the alignment surface. 4. The end on the side of the alignment surface of the semiconductor substrate, the spacer and the transparent body which are orthogonal to the substrate holding surface and the alignment surface and are mounted on the substrate holding surface. The semiconductor laser module is characterized in that these members are aligned by hitting the alignment surface, and the laser chip holding surface is a surface inclined with respect to the substrate holding surface. 5. The semiconductor laser module according to any one of claims 1 to 4, wherein the support is a heat dissipation material that emits heat from the semiconductor laser chip. 6. The semiconductor laser module according to claim 1, wherein the transparent plate and the spacer are integrally formed. 7. The spacer according to any one of claims 1 to 6, wherein the spacer is provided with a communicating portion for communicating the air layer formed by the spacer to the outside. Semiconductor laser module. 8. The semiconductor laser module according to claim 1, wherein an electronic circuit for signal processing is built in the semiconductor substrate. 9. The semiconductor laser module according to claim 1, a hologram element that diffracts laser light emitted from the semiconductor laser module into a plurality of light beams, and a plurality of light beams obtained through the hologram elements. An objective lens for condensing as a light spot on the recording medium,
An optical pickup comprising: a quarter-wave plate for allowing returned light from an optical recording medium to pass through without being diffracted by the holograc element.