JPH07161065A - Optical pickup device - Google Patents

Abstract

PURPOSE:To obtain an optical pickup device capable of performing a tracking servo by a three beam method and in which wire-bondings to a semiconductor laser element and a photodetecting element are made easy. CONSTITUTION:This device is provided with a base body 1 having an upper flat plane part 1a, a semiconductor laser element 4 provided on the upper flat plane part 1a of the base body 1 and outputting a laser beam to a side direction and a signal detecting light detecting part 5 provided on the upper flat plane part 1a. Further, the device is provided with a reflection type diffraction grating 6 disposed to face oppositely to the semiconductor laser element 4 and dividing the laser beam into three lines of beams and reflecting them upward, a transmission type hologram element 7 irradiated with three lines of beams reflected at the reflection type diffraction grating 6 and an objective lens 8 converging three lines of beams transmitting through the hologram element 7 on an optical recording medium 9. Then, three lines of beams reflected at the optical recording medium 9 are diffracted to the one side direction of the diffraction grating 6 with the hologram element 7 to be made incident on the signal detecting light detecting part 5 from an upper side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device using a hologram element.

[0002]

2. Description of the Related Art In recent years, research and development of an optical pickup device using a hologram element has been carried out in response to a demand for reduction in size, weight and cost of the optical pickup device.

FIG. 17 shows Japanese Patent Laid-Open No. 3-76035 (G11).
B 7/135) is a configuration diagram of an optical pickup device having a hologram element that performs tracking servo by using the three-beam method.

In the figure, 101 is a disk, 102 is a semiconductor laser element for outputting a laser beam (laser light) upward, 103 is a first hologram element for dividing the laser beam into three beams (diffraction for three divisions). Lattice), 104
Is a second hologram element that transmits the three beams and diffracts the return beam (reflected light) from the disc 101, and 105 represents the three beams that have passed through the second hologram element 104 on the disc 101. An objective lens for condensing and forming three spots, and 106 is a servo photodetection element for detecting the return beam from the disk 101 diffracted by the second hologram element 104.

In this optical pickup device, since the return beam from the disk 101 received by the photodetector 106 is not diffracted by the first hologram element 103, there is no loss of light and the return to the photodetector 106. Since the second hologram element 104 diffracts No. 2, it can be made thinner than the case where a prism or the like is used.

However, in this device, since the semiconductor laser element 102, the first hologram element 103, the second hologram element 104 and the lens 105 are present on a straight line, there is a problem that the thickness of the apparatus is still large.

Further, Japanese Patent Laid-Open No. 4-238121 (G11
B 7/09) and JP-A-4-60931 (G11).
B 7/135) discloses an optical pickup device in which the direction of a laser beam output from a semiconductor laser device is converted into a right angle to achieve a thin structure.

[0008]

However, as compared with other methods such as the push-pull method, tracking / tracking can be performed with higher accuracy.
No thin optical pickup device using the three-beam method capable of servo is known, and in the above-mentioned device,
In addition to difficulty in wire bonding to the semiconductor laser element and the photodetection section, it is not easy to attach the semiconductor laser element, the photodetection section, and the three-division diffraction grating, which causes a problem of high cost.

The present invention has been made in view of the above problems, and enables tracking / servoing by the three-beam method, and wire bonding to a semiconductor laser device and a photodetector, a semiconductor laser device, and photodetection. An object of the present invention is to provide a thin optical pickup device in which a diffraction grating for three-part division can be easily attached.

[0010]

An optical pickup device of the present invention comprises a substrate, a semiconductor laser element which is provided on the substrate and outputs a laser beam to the side, and a semiconductor laser element arranged on the substrate so as to face the semiconductor laser element. A reflective diffraction grating that splits the laser beam into at least three beams and reflects the laser beam above the substrate; and a transmissive hologram element that receives the three beams reflected by the reflective diffraction grating. A converging optical system that converges the three beams that have passed through the hologram element onto an optical recording medium, and the converging optical system that is reflected by the optical recording medium and diffracted to the side of the diffraction grating by the hologram element.
And a signal-detecting photodetector provided on the base for receiving a main beam.

Further, the optical pickup device of the present invention includes a substrate having at least one upper plane portion, a semiconductor laser element provided on the one upper plane portion for outputting a laser beam to the side, and on the substrate. A reflection type diffraction grating which is arranged to face the semiconductor laser element and divides the laser beam into at least three beams and reflects above the substrate, and three beams reflected by the reflection type diffraction grating are incident. Transmission hologram element, a converging optical system that converges the three beams that have passed through the hologram element to an optical recording medium, and the hologram element is reflected by the optical recording medium and diffracted to the side of the diffraction grating by the hologram element. And a signal detecting photodetector provided on the upper flat surface portion for receiving the three beams or on another upper flat surface portion of the substrate parallel to the upper flat surface portion. To.

Further, the optical pickup device of the present invention comprises a base, a semiconductor laser element which is provided on the base and outputs a laser beam to the side, and the laser beam which is arranged on the substrate so as to face the semiconductor laser element. Is divided into at least three beams and is reflected above the substrate, a transmissive hologram element for injecting the three beams reflected by the reflective diffraction grating, and a transmissive hologram element A converging optical system for converging the three beams on an optical recording medium having a recording surface arranged so as to be substantially parallel to the optical axis direction and the reflection direction of the laser beam output to the side, and the optical recording. A signal detection photodetection unit provided on the base for receiving the three beams reflected by the medium and diffracted by the hologram element to the side of the diffraction grating;
And a reflecting means is provided between the reflective diffraction grating and the transmissive hologram element or between the transmissive hologram element and the converging optical system.

In the optical pickup device of the present invention, a substrate having at least one upper flat surface portion, a semiconductor laser element provided on the upper flat surface portion of the base member for outputting a laser beam to the side, and the substrate A reflection type diffraction grating which is arranged to face the semiconductor laser element and divides the laser beam into at least three beams and reflects above the substrate, and three beams reflected by the reflection type diffraction grating are incident. Transmission type hologram element and optical recording having a recording surface arranged so that the three beams transmitted through the hologram element are substantially parallel to the optical axis direction and the reflection direction of the laser beam output to the side. A converging optical system that converges on a medium, and the upper flat surface portion that receives the three beams reflected by the optical recording medium and diffracted to the side of the diffraction grating by the hologram element, or A signal detecting photodetector provided on the other upper flat surface of the base body parallel to the upper flat surface of the base, between the reflection type diffraction grating and the transmission hologram element or the transmission type. A reflecting means is provided between the hologram element and the converging optical system.

In particular, the photodetector is provided behind the reflective diffraction grating.

In particular, the semiconductor laser device, the reflection type diffraction grating, and the photodetection section are arranged in this order on a substantially straight line.

In particular, another signal detecting photodetection section for receiving the three beams reflected by the optical recording medium and diffracted by the hologram element to the other side of the diffraction grating is provided on the substrate. It is characterized by that.

In particular, on or above the one flat surface portion for receiving the three beams reflected by the optical recording medium and diffracted by the hologram element to the other side of the diffraction grating. Another signal detecting photodetector is provided on another upper flat surface of the base.

In particular, the reflection type diffraction grating is supported by an inclined portion provided on a part of the base.

Further, the inclined portion is formed by being recessed in the base body.

[0020]

According to the structure of the present invention, the laser beam is divided into at least three beams by the reflection type diffraction grating and is reflected above the substrate, and the three beams reflected by the optical recording medium are transmitted. Since it is diffracted to the side of the reflection type diffraction grating by the type hologram element and is incident on the photodetection section for signal detection, tracking / servo by the three-beam method is possible and the apparatus can be made thin.

Further, since the semiconductor laser element, the signal detection photodetection section, and the reflection type diffraction grating are provided on the base body, they can be attached with high precision and wire bonding to them, and the device can be easily mounted. The price can be reduced. In particular, when the semiconductor laser device and the signal detection photodetector are provided on the same upper flat surface portion or on parallel upper flat surface portions, highly accurate mounting and wire bonding become easier.

Further, the light is incident on the light detecting portion for signal detection 3
Since the beam of the book is detected without entering the reflection type diffraction grating again, there is no light loss.

Further, the optical recording medium is arranged so that the optical axis direction and the reflection direction of the laser beam output to the side are substantially parallel to the recording surface, and the reflection type diffraction grating and the transmission type hologram element are provided. The distance between the semiconductor laser element and the optical recording medium can be shortened by providing the reflection means between the two or between the transmission hologram element and the converging optical system, and the device can be made thinner.

In particular, when the photodetector is provided behind the reflection type diffraction grating, the diffraction grating functions as a light shielding member, so that the sensitivity of the photodetector is increased.

In particular, when the semiconductor laser device, the reflection type diffraction grating, and the photodetector are provided in this order on a substantially straight line, the width of the substrate can be reduced, so that the laser beam output to the side can be made smaller. By arranging the optical recording medium so that the optical axis direction and the reflection direction and the recording surface are substantially parallel to each other, it is possible to make the device thinner.

In particular, another signal detecting photodetection section for injecting the three beams reflected by the optical recording medium and diffracted by the hologram element to the other side of the diffraction grating is provided on the substrate. In this case, since the signals are detected by the two signal detection photodetectors, the reliability is high.

Particularly, when the reflection type diffraction grating is supported by an inclined portion provided on a part of the base, it can be accurately provided on the inclined portion.

Further, in the case where the inclined portion is formed as a recess in the base body, it is easier to install the diffraction grating with high accuracy.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical pickup device according to a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic perspective view of an optical pickup device for performing tracking servo using the three-beam method of this embodiment, and FIG. 2 is a schematic configuration diagram of this optical pickup device. The electrodes and bonding wires are not shown.

In the figure, reference numeral 1 designates a good thermal conductive substrate made of a conductive semiconductor material made of n ⁺ type Si (silicon) or the like or a conductive metal such as copper, which is a flat upper surface portion 1a and Inclined portion 1 forming an angle of 45 degrees with the upper flat portion 1a
b.

Reference numeral 2 is an n ⁺ as a conductive heat sink for mounting a semiconductor laser element (laser diode) which is die-bonded on the upper plane portion 1a and electrically connected to the substrate 1.
Type Si semiconductor substrate. 2a is this semiconductor substrate 2,
A laser beam monitor for an n ^- type diffusion layer selectively formed on the surface of one end side thereof and ap ⁺ type diffusion layer selectively formed on the surface of the n ^- type diffusion layer. PIN
Type photodiode (light detection unit).

Reference numeral 4 denotes a laser beam (laser light) provided with another electrode 4a on the upper surface which is die-bonded to an electrode side (not shown) on the other end side surface portion of the semiconductor substrate 2 and electrically connected to the substrate 2. A semiconductor laser device for outputting,
The front end surface is arranged so as to face the inclined portion 1b. In this element 4, a laser beam is generated in an active region (not shown) extending in parallel with the surface portion, and a main laser beam for detecting an optical recording medium signal is emitted from the front end face side of the element 4 and a main laser beam is emitted from the rear end face side thereof for monitoring. A laser beam (not shown) is output.

Reference numeral 5 denotes a signal detection photodetection element (signal detection detection section) for detecting the return beam (reflected light) returned from the optical recording medium to perform tracking servo, focusing servo and reproduction. And the beams other than the return beam do not substantially enter the detection element 5.
The upper flat surface portion 1a is die-bonded to the electrode side (not shown) and electrically connected to the substrate 1.

Reference numeral 6 denotes a three-divided reflection type diffraction grating having gratings at equal intervals fixed to the inclined portion 1b. The diffraction grating is arranged so as to face the semiconductor laser element 4 and is output from the front end face side of the element 4. The main laser beam is
A ± 1st-order diffracted beam (hereinafter, the 0th-order beam is referred to as a main beam, the + 1st-order beam is referred to as a sub-beam X, and the -1st-order beam is referred to as a sub-beam Y) and is reflected upward.

Reference numeral 7 denotes a transmissive hologram element provided above the three-division reflective diffraction grating 6, and in this embodiment, a group of curves in which the pitch of the grating is gradually changed. Is composed of a transparent substrate formed on the upper surface. The element 7 transmits (0th-order diffraction) the 0th-order and ± 1st-order beams (main beam and sub-beams X and Y), and reflects these 0th-order and ± 1st-order beams returned from the optical recording medium. Of the return beam (main beam and sub-beams X and Y) is diffracted in the first order and converged (focused) on the photo-detecting portion of the photo-detecting element 5 located on the side of the diffraction grating 6. The hologram element 7 generates an ± 1st-order diffracted beam having an optical axis that is oblique to the optical axis, and the ± 1st-order diffracted beam in one direction orthogonal to the beam traveling direction. It exerts a condensing (astigmatism) effect such that the focal lengths are different in the direction orthogonal to the one direction. That is, this hologram element 7 also has the functions of a beam splitter, a condenser lens, and a cylindrical lens.

Reference numeral 8 is provided above the transmissive hologram element 7, and the 0th and ± 1st order beams (main beam and sub-beam X, which are transmitted (0th order diffraction) through the hologram element 7).
Y) is converged on the surface of an optical recording medium 9 composed of an optical disc such as a compact disc, and the main beam spot and the sub-beam spots X and X are provided on both sides of the main beam spot.
The objective lens is a converging optical system for forming the sub beam spot Y.

Here, as shown in FIG. 3, the main spot scans the track to be reproduced, and the sub-spots X and Y are scanned.
The optical system of the optical pickup device is adjusted and arranged so that both sides of the main spot slightly scan the track and scan. The objective lens 8 is the photodetector 5
Driven by a drive mechanism (not shown) on the basis of the detection signal of, the focusing and tracking adjustments are performed.

FIG. 4 shows the base 1 of this optical pickup device.
3 is a top view of the electrode, which is not shown in FIGS. 1 and 2,
The details of the wire bonding wire and the photodetector 5 will be shown.

As shown in the figure, the photo-detecting element 5 of this embodiment
Is a photodetection section A, B, C, D divided into four in the center for performing focusing servo using the astigmatism method,
It is composed of photodetectors E and F provided on both sides for performing tracking servo using the three-beam method,
The main beam, which is first-order diffracted by the hologram element 7, is incident on the center of each of the four photodetector sections A, B, C, and D, and the light-detecting sections E and F are similarly similarly first-order diffracted. The sub beams X and Y are incident.

The first-order diffracted main beam has the above-mentioned astigmatism due to the hologram element 7, and the lens 8 and the optical recording medium 9 are schematically shown in FIG.
When and are too close to each other, an elliptical spot in which the direction connecting the centers of the photodetector B and the photodetector C is the major axis direction (dotted line a in the figure)
In the case of the positional relationship between the lens 8 and the optical recording medium 9 that achieves good focusing, a circular spot (solid line b in the figure) is formed at the center of the photodetection portions A, B, C, and D, and the lens 8 and the optical recording medium are formed. When 9 is too far, the direction connecting the centers of the photodetector A and the photodetector D becomes an elliptical spot (dotted line c in the figure) whose major axis is the direction. Therefore, the focus error (F
The E) signal is a FE signal = (A1 + D1)-(B1 + C1) obtained by an arithmetic circuit (not shown). In addition to the focus shift amount, a positive signal when the distance is too close, a 0 when the focusing is good, If it is too far, it will be obtained as a negative signal.

When the main spot is tracking well, the intensities of the sub-beams X and Y incident on the photodetectors E and F are equal, and either side of the track to be reproduced by the main spot. In the case of the deviation, the intensity of one of the corresponding sub-beams X and Y increases. Therefore, with respect to the tracking error (TE) signal, it is possible to obtain information on the deviation amount and on which side of the track the deviation is due to the TE signal = E1-F1 obtained by an arithmetic circuit (not shown).

The reproduced signal is obtained by the reproduced signal = A1 + B1 + C1 + D1 obtained by an arithmetic circuit (not shown). In addition, A1 to F1 in the above equations indicate detection signal intensities in the photodetectors A to F.

In FIG. 4, 10 to 17 are relay electrodes made of gold or the like formed on the upper flat surface portion 1a of the substrate 1 via an insulating layer made of SiO ₂ or the like (not shown), and 18 is a photodiode 2a. Electrodes made of gold, 19-24
Is the other electrode made of gold or the like for each of the photodetection sections A to F of the photodetection element 5. The electrode 4a of the semiconductor laser element 4, the electrode 18 of the photodiode 2a, and the electrode 1 of each of the photodetectors AF.
9 to 24 are electrically connected to the corresponding relay electrodes 10 to 17 by wire bonding wires (thick line in the figure) such as gold, and the relay electrodes 10 to 17 are connected to an arithmetic circuit (not shown) by wires such as gold. It is electrically connected by a bonding wire (thick line in the figure). Then, the semiconductor laser device 4,
The photodetectors A to F of the photodetector 5 and the photodiode 2a are electrically connected to a common backside electrode (not shown) formed on the backside of the base 1.

The reproduction, tracking servo, focusing servo and the like in such an optical pickup device are performed as follows.

The laser beam output from the rear end face side of the semiconductor laser device 4 is received by the photodiode 2a, and an AP (not shown) is used based on a signal corresponding to the amount of received light.
The C (automatic output control) circuit controls so that the laser beam is constant.

On the other hand, the laser beam output from the front end face side of the semiconductor laser device 4 is 0 by the reflection type diffraction grating 6.
Next, ± 1st order diffracted beams (main beam and sub-beam X,
It is divided into a plurality of beams including Y) and is reflected upward at a right angle. The 0th order and ± 1st order diffracted beams (main beam and sub beams X and Y) reflected upward enter from one of the transmission hologram elements 7. After that, the 0th order and ± 1st order diffracted beams (main beam and sub beams X and Y) diffracted (transmitted) by the element 7 are transmitted through the objective lens 8 onto the optical recording medium 9 as described above. The sub-beam spots X and Y are converged (focused). The return beams (main beam and sub beams X and Y) containing the information signals from these main spots and sub spots X and Y, after passing through the objective lens 8, are first-order diffracted by the transmissive hologram element 7 to obtain the main beam. Is incident on the photodetectors A to D of the photodetector 5, and the sub-beams X and Y are incident on the photodetectors E and F. Then, the signal obtained by the photodetection element 5 is calculated by an arithmetic circuit (not shown) to obtain the above-mentioned reproduction signal, FE signal and TE signal. Based on the FE signal and the TE signal, the objective lens 8 is driven by a driving mechanism (not shown) to perform tracking servo and focusing servo.

In this optical pickup device, the reflection type diffraction grating 6 causes the laser beam to be 0th order, ± 1st order (main beam,
The three beams, which are split into sub-beams X and Y), reflected upward, and reflected by the optical recording medium 9, are first-order diffracted to the side of the reflection type diffraction grating 6 by the hologram element 7. Since the main beam is incident on the photodetectors A to D and the sub-beams X and Y are incident on the photodetectors E and F, respectively, from above,
Tracking / servo by the three-beam method can be performed, and the thickness can be reduced.

Further, since the semiconductor laser element 4, the signal detection photodetection element 5, and the reflection type diffraction grating 6 are formed on the same substrate 1, these elements can be easily mounted with high precision. Moreover, since the semiconductor laser element 4 and the signal detection light detection element 5 are provided on the upper plane portion 1a,
Wire bonding to these elements is easy.

In the above description, the main beam and sub-beams X and Y which are first-order diffracted by the hologram element 7 are made incident on the photodetector 5, but the main beam and sub-beams X and Y which are -1st-order diffracted. Needless to say, the light may be incident on the light detection element 5.

Next, an optical pickup device according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a schematic configuration diagram of an optical pickup device of the present embodiment, which can perform tracking servo by the three-beam method and focusing servo by the astigmatism method. The difference from the first embodiment is that another upper flat surface portion is provided on the opposite side of the inclined portion of the base body,
The photodetecting element is also provided on the upper plane portion, and the same portions as or corresponding portions to those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted and electrodes and the like will not be shown.

In FIG. 6, reference numeral 1 denotes a good heat conductive base made of a conductive semiconductor material such as n ⁺ type Si or a conductive metal such as copper. Between the upper flat portions 1c, there is an inclined portion 1b forming an angle of 45 degrees with the upper flat portion 1a.

Reference numeral 35 denotes a photodetector for signal detection having the same structure as the photodetector 5 of the first embodiment, which is die-bonded to the electrode side (not shown) on the upper flat surface 1c and electrically connected to the substrate 1. , The 0th and ± 1st order return beams (main beam and sub beam X, which are reflected and returned from the optical recording medium 9).
Y) is -1st-order diffracted by the hologram element 7 and is converged (focused) on the photodetection portion of the photodetection element 35 located on the other side of the diffraction grating 6.

In such an optical pickup device, tracking servo can be performed by the three-beam method and the device can be made thin as in the first embodiment, and the semiconductor laser device 4 and the signal detection photodetector devices 5 and 35 have Since it is provided on the flat surface portion 1a and the upper flat surface portion 1c parallel thereto, wire bonding to these elements is easy, and the semiconductor laser element 4, the signal detection photodetection elements 5 and 35, and the reflection diffraction grating. Since 6 is provided on the same substrate 1, these elements can be easily mounted.

In addition, a signal detected by the photodetector 5 for the feedback beam diffracted by the + 1st order in the hologram element 7 and a photodetector element 35 for the feedback beam diffracted in the -1st order by the hologram element 7.
Add the signals detected by the addition calculation circuit (not shown),
On the basis of this added signal, the reproduction servo, the tracking servo by the three-beam method, and the focusing servo by the astigmatism method are performed, so that the detection signal strength based on the feedback beam becomes larger and the reliability becomes higher than in the first embodiment. .

When two photodetecting elements are used as in the second embodiment, the feedback beam diffracted by the + 1st order by the hologram element and the feedback beam diffracted by the -1st order are collected on one side and collected on the other side. They are appropriately arranged on the substrate 1 which does not substantially enter other than these return beams.

Further, in each of the above embodiments, the hologram element 7 has a hologram surface on the upper surface, but the hologram surface may of course be the lower surface.

Next, an optical pickup device according to the third embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a schematic perspective view of an optical pickup device capable of performing tracking servo and astigmatism method focusing servo by the three-beam method of the present embodiment, and FIG. 8 is a schematic configuration diagram of this optical pickup device.

The difference of this embodiment from the first embodiment is that a concave portion having an inclined portion is formed on the upper surface of the base body 1 whose entire upper surface is flat, and the diffraction grating 6 is provided on this inclined surface.
The same parts or corresponding parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Moreover, electrodes and the like are not shown in these figures.

In FIGS. 7 and 8, 1 is S as in the first embodiment.
A base made of a semiconductor material such as i, a conductive metal material such as copper, and the like.
A concave portion 1e having an inclined surface (inclined portion) 1d forming 5 degrees is formed. The three-division reflective diffraction grating 6 is fixed on the inclined surface 1d of the recess 1e.

Reference numeral 7 denotes a transmissive (transmissive) hologram element provided above the three-division reflective diffraction grating 6, and in the present embodiment, a group of curves formed by gradually changing the pitch of the grating. The transparent substrate is formed on the lower surface. This element 7 also has the same function as in the first embodiment.

This embodiment has substantially the same configuration as that of the first embodiment except that the method of installing the reflection type diffraction grating 6 for division into three parts is different, and therefore has the same effect as the first embodiment.

That is, this optical pickup device splits the laser beam into 0th order and ± 1st order (main beam, sub-beams X, Y) beams by the reflection type diffraction grating 6 and reflects the beams upward, and also performs optical recording. The three beams reflected by the medium 9 are diffracted by the hologram element 7 to the side of the reflection type diffraction grating 6 in the first order (or −1st order) and the main beams are detected by the photodetectors A to D.
In addition, since the sub-beams X and Y are incident on the photodetectors E and F, respectively, from above, tracking by the three-beam method
Servo can be performed and the device can be made thinner.

Further, since the semiconductor laser device 4, the signal detection photodetector 5, and the reflection type diffraction grating 6 are provided on the same substrate 1, it is easy to attach these devices with high precision. Moreover, since the semiconductor laser device 4 and the signal detection light detection device 5 are provided on the same upper flat surface portion 1a, wire bonding to these devices is also easy.

Furthermore, in this embodiment, since the concave portion 1e is used in the base 1 to fix the three-division reflection type diffraction grating 6, the diffraction grating 6 can be easily installed with high precision.

In each of the above embodiments, a conductive and highly heat-conductive substrate is used as the substrate 1, but a non-conductive substrate having poor thermal conductivity such as resin may be used. In this case, the electrodes formed on the base body 1 do not need to interpose an insulating layer, the base body 1 and the semiconductor substrate 2 are not electrically connected, and a common electrode cannot be provided on the back surface of the base body 1. Therefore, it is necessary to change the design such as providing an electrode for the semiconductor substrate 2 on the base body 1 instead of this. In the following examples, the base 1 is made of a non-conductive material.

Next, an optical pickup device according to the fourth embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a schematic perspective view of an optical pickup device capable of performing tracking servo and astigmatism focusing servo by the three-beam method of the present embodiment, and FIG. 10 is a schematic configuration diagram of this optical pickup device.

The present embodiment is different from the third embodiment in that the semiconductor laser device, the three-division diffraction grating, and the photodetector are arranged in a straight line, and the same portion as or a portion corresponding to the third embodiment. Are denoted by the same reference numerals and description thereof will be omitted.
Moreover, electrodes and the like are not shown in these figures.

In FIGS. 9 and 10, reference numeral 1 denotes a base made of a non-conductive material such as resin, and the upper flat surface portion 1a thereof has a concave portion 1e having an inclined surface 1d forming 45 degrees with the flat surface portion. Are formed. On the inclined surface 1d of the recess 1e, the three-division reflective diffraction grating 6 having gratings at equal intervals is fixed. As described above, the reflection type diffraction grating 6 is arranged so as to face the semiconductor laser element 4, divides the laser beam output from the front end face of the element 4 into 0th and ± 1st order diffracted beams and reflects them upward.

Reference numeral 5 denotes a photodetecting element provided on the upper flat surface portion 1a of the base body 1. The photodetecting element 5 is a diffraction grating 6
The upper flat surface portion 1a opposite to the semiconductor laser element 4 with the sandwiched therebetween.
Located on top. That is, the semiconductor laser device 4 and the diffraction grating 6
The light detection elements 5 are arranged in this order on a straight line on the upper flat surface portion 1a.

Therefore, the photodetection element 5 is located on the back surface side of the diffraction grating 6, that is, behind the diffraction grating 6, and the diffraction grating 6 functions as a light shielding member of the photodetection element 5. As a result, it is possible to prevent the stray light, which is the laser beam output from the front end face of the semiconductor laser element 4 from being reflected by the diffraction grating 6 and the like, and the laser beam output from the front end face and expanded, from entering the photodetector element 5. .

FIG. 11 is a top view of the substrate 1 of this optical pickup device, showing the details of the electrodes, wire bonding lines, and photodetector 5 which are not shown in FIGS. 9 and 10. However, also in this figure, the same parts or corresponding parts as those of the first or third embodiment are designated by the same reference numerals and the description thereof will be omitted, but in this embodiment, a non-conductive base is used as the base 1. Since it is used, the extraction electrode 25 for the conductive semiconductor substrate 2 and the extraction electrode 26 for the photodetection element 5 are provided.

Since this embodiment has substantially the same configuration as that of the third embodiment except that the installation position of the photodetector 5 is different, it has the same effect as that of the third embodiment, and as described above. To
Since the diffraction grating 6 functions as a light shielding member of the photodetection element 5, the sensitivity of the photodetection element 5 is increased.

By the way, normally, a constant distance is required between the light source (semiconductor laser element 4) and the objective lens 8. For example, in the case of a compact disc device, the distance needs to be about 20 mm. In order to make the optical pickup device thinner, for example, instead of arranging the hologram element 7 and the objective lens 8 in a straight line, the hologram element 7 and the objective lens 8 are arranged so that the hologram surface of the hologram element 7 and the objective lens 8 are orthogonal to each other. It is preferable to adopt a structure in which light reflecting means such as a reflecting mirror is provided between the lenses 8.

Next, an optical pickup device according to the fifth embodiment of the present invention will be described with reference to the drawings. FIG. 12 is a schematic perspective view of an optical pickup device of the present embodiment, which can perform tracking servo by the three-beam method and focusing servo by the astigmatism method.

The difference between this embodiment and the fourth embodiment is that a light reflecting means such as a reflecting mirror is provided between the hologram element 7 and the objective lens 8, and the same portion as or a portion corresponding to the fourth embodiment. Will be denoted by the same reference numerals and will be briefly described.

In this embodiment, the semiconductor laser element 4, the three-division diffraction grating 6, and the photodetector element 5 are arranged in a straight line, and the light reflecting means 27 including a reflection mirror or the like is provided between the hologram element 7 and the objective lens 8. And the hologram element 7
Since the hologram surface and the objective lens 8 are orthogonal to each other, the device can be made thinner.

In the first to fifth embodiments, the semiconductor laser element and the photo-detecting element are provided on the same upper flat surface, but the photo-detecting element is provided on the upper flat surface portion formed in parallel with the upper flat surface portion. It may be provided. In the first to fifth embodiments, since the element is provided on the upper flat surface portion, the element can be easily installed. However, when the upper flat surface portions parallel to each other form a step, this is used as a reference portion for installing the element. The device can be installed more easily.

Although the focusing servo is performed by the astigmatism method in the above description, another method may be used. For example, instead of the hologram element 7, the transmission hologram element and the photodetector elements 5 and 35 having the grating shape shown in FIG. Instead of this, focusing servo may be performed by the spot size method using the photodetector shown in FIG. In this case, the main beam and the sub-beams X and Y are each divided into two by the hologram element, and the two main beams are diffracted by the ± 1st orders and are respectively sent to the photodetection units A and C and the photodetection units B and D. The two sub beams X and Y are incident on the photodetectors E and F to form spots. Therefore, the FE signal, the TE signal, and the reproduction signal are: FE signal = (A1-C1)-(B1-D1) TE signal = E1-F1 reproduction signal = A1 + B1 + C1 + D1. It should be noted that A1 to F1 in this equation are detection intensities at the photodetectors A to F shown in FIG.

In addition to the above, instead of the hologram element 7, a hologram element having a grating shape shown in FIG. 15 and the photodetection elements 5 and 35 shown in FIG. You may perform by the Foucault method. In this case, the main beam and the sub beams X and Y are each divided into two and are incident on the photodetectors A to H to form spots. Therefore, the FE signal, the TE signal, and the reproduction signal are: FE signal = (A1 + D1)-(B1 + C1) TE signal = (E1 + G1)-(F1 + H1) reproduction signal = A1 + B1 + C1 + D1. It should be noted that A1 to H1 in this equation are detection intensities at the photodetectors A to H shown in FIG.

Further, in the first to fifth embodiments, the substrate 2 having the base 1 on which the photodetector elements 5 and 35 and the photodiode 2a are provided.
Etc. are provided separately, but the photodetection elements and the photodiodes, or the photodetection portions of the photodetection elements 5 and 35 by using a semiconductor process such as a diffusion method on the substrate 1 with at least one of them, Photodiode 2a
May be directly installed, and in such a case, it is understood to be installed on the substrate of the present invention. When this configuration is applied to the first and second embodiments, the inclined portion 1b which is a separate body is attached to the plate-shaped substrate 1 by a semiconductor process as a photo-detecting portion, and then attached. In such a case, needless to say, the one in which the diffraction grating for three divisions is directly formed on the inclined portion may be used.

Furthermore, in the above-mentioned reflection type diffraction grating and transmission type hologram element, since the diffraction of the second or higher order is also performed, it is desirable to set the optical system so that the diffracted beams of the second or higher order do not enter. However, since the diffracted beams of the second and higher orders have extremely small intensities, even if they enter the photodetector, it does not pose a serious problem. Further, although the photodetector can appropriately select the arrangement position as described above, it is needless to say that the grating shape of the transmission hologram element or the like needs to be changed when the arrangement is changed.

In addition, by forming a transparent (translucent) resin mold on such an optical pickup device, it is possible to prevent dew condensation and reduce the cost.

[0083]

According to the structure of the present invention, the laser beam is divided into at least three beams by the reflection type diffraction grating, and the three beams are reflected above the substrate and reflected by the optical recording medium. Is diffracted to the side of the reflection type diffraction grating by the transmission type hologram element and is incident on the signal detection photodetection section, so that tracking servo by the three-beam method is possible and the apparatus can be made thin.

Further, since the semiconductor laser element, the signal detecting light detecting portion, and the reflection type diffraction grating are provided on the base body, it is easy to attach them with high precision and wire bonding to them, and the device The price can be reduced. In particular, when the semiconductor laser device and the signal detection photodetector are provided on the same upper flat surface portion or on parallel upper flat surface portions, highly accurate mounting and wire bonding become easier. Furthermore, since the three beams incident on the signal detection photodetection section are detected without entering the reflection type diffraction grating again, there is no light loss.

Further, the optical recording medium is arranged so that the optical axis direction of the laser beam outputted to the side and the reflection direction are substantially parallel to the recording surface, and the reflection type diffraction grating and the transmission type hologram element are provided. The distance between the semiconductor laser element and the optical recording medium can be shortened by providing the reflection means between the two or between the transmission hologram element and the converging optical system, and the device can be made thinner.

When the photodetection section is provided behind the reflection type diffraction grating, the diffraction grating functions as a light shielding member, so that the sensitivity of the photodetection section is increased.

In particular, when the semiconductor laser device, the reflection type diffraction grating, and the photodetection section are provided in this order on a substantially straight line, the width of the substrate can be reduced, so that the laser beam output to the side can be made smaller. By arranging the optical recording medium so that the optical axis and the reflection direction and the recording surface are substantially orthogonal to each other, it is possible to make the device thinner. Further, in such a case, the three beams diffracted by the hologram element and incident on the photodetector can be made substantially symmetrical with respect to the center beam thereof, and therefore, even when the recording surface of the optical recording medium is inclined, the signal is not changed. Less likely to cause offset.

In particular, another signal detection photodetection section for injecting the three beams reflected by the optical recording medium and diffracted by the hologram element to the other side of the diffraction grating is provided on the substrate. In this case, since the signals are detected by the two signal detection photodetectors, the reliability is high.

Particularly, when the reflection type diffraction grating is supported by an inclined portion provided on a part of the base, it can be accurately provided on the inclined portion.

Furthermore, in the case where the inclined portion is formed as a recess in the base body, it is easier to install the diffraction grating with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an optical pickup device according to a first embodiment of the invention.

FIG. 2 is a schematic configuration diagram of the optical pickup device of the embodiment.

FIG. 3 shows a track of the optical recording medium in the above embodiment,
It is a figure which shows the relationship of the main spot and the sub-spots X and Y.

FIG. 4 is a top view of the base body of the embodiment.

FIG. 5 is a top view of the photo-detecting element of the above embodiment.

FIG. 6 is a schematic configuration diagram of an optical pickup device according to a second embodiment of the invention.

FIG. 7 is a schematic perspective view of an optical pickup device according to a third embodiment of the invention.

FIG. 8 is a schematic configuration diagram of the optical pickup device of the embodiment.

FIG. 9 is a schematic perspective view of an optical pickup device according to a fourth embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of the optical pickup device of the embodiment.

FIG. 11 is a top view of the base body of the embodiment.

FIG. 12 is a schematic perspective view of an optical pickup device according to a fifth embodiment of the invention.

FIG. 13 is a top view of a transmission hologram element used in the spot size method.

FIG. 14 is a top view of a photodetector used in the spot size method.

FIG. 15 is a top view of a transmission hologram element used in the Foucault method.

FIG. 16 is a top view of a photodetector used in the Foucault method.

FIG. 17 is a configuration diagram of a conventional optical pickup device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 1a Upper plane part 1b Inclined part 1c Upper plane part 1d Inclined part (inclined surface) 1e Recess 4 Semiconductor laser device 5 Photodetector for signal detection (photodetector for signal detection) 6 Reflective diffraction grating 7 Transmission hologram Element 8 Objective lens (converging optical system) 9 Optical recording medium 35 Photodetector for signal detection (photodetector for signal detection)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Yamaguchi 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (10)

[Claims] 1. A substrate, a semiconductor laser element that is provided on the substrate and outputs a laser beam to the side, and a semiconductor laser element that is disposed on the substrate so as to face the semiconductor laser element and divides the laser beam into at least three beams. In addition, a reflective diffraction grating that reflects above the substrate, a transmissive hologram element that enters the three beams reflected by the reflective diffraction grating, and three beams that have passed through the hologram element are optically recorded. Converging optical system for converging on a medium, and optical detection for signal detection provided on the substrate for receiving the three beams reflected by the optical recording medium and diffracted to the side of the diffraction grating by the hologram element. And an optical pickup device. 2. A substrate having at least one upper plane portion,
A semiconductor laser element that is provided on one upper plane portion of the base body and outputs a laser beam laterally; and a semiconductor laser element that is arranged on the substrate so as to face the semiconductor laser element and divides the laser beam into at least three beams. A reflection type diffraction grating that reflects above the substrate, and 3 that is reflected by the reflection type diffraction grating
Transmission type hologram element for injecting three beams, a converging optical system for converging three beams transmitted through the hologram element to an optical recording medium, and a diffraction grating side of the hologram element reflected by the optical recording medium. A signal detection photodetector provided on the one upper flat surface portion for receiving the three beams diffracted toward one side or on another upper flat surface portion of the substrate parallel to the one upper flat surface portion. An optical pickup device characterized by being provided. 3. A substrate, a semiconductor laser element which is provided on the substrate and outputs a laser beam to the side, and a semiconductor laser element which is arranged on the substrate so as to face the semiconductor laser element and divides the laser beam into at least three beams. In addition, a reflective diffraction grating that reflects above the substrate, a transmissive hologram element that receives the three beams reflected by the reflective diffraction grating, and three beams that have passed through the hologram element A converging optical system that converges on an optical recording medium in which a recording surface is disposed so as to be substantially parallel to the optical axis direction of the laser beam output toward one side and the reflection direction, and the hologram element is reflected by the optical recording medium. A signal detecting photodetector provided on the base for receiving the three beams diffracted to the side of the diffraction grating, the reflection type diffraction grating and the transmission type hologram element. The optical pickup apparatus characterized in that a reflecting means or between the transmission type holographic optical element and the converging optical system and. 4. A substrate having at least one upper flat surface portion,
A semiconductor laser element that is provided on one upper plane portion of the base body and outputs a laser beam laterally; and a semiconductor laser element that is arranged on the substrate so as to face the semiconductor laser element and divides the laser beam into at least three beams. A reflection type diffraction grating that reflects above the substrate, and 3 that is reflected by the reflection type diffraction grating
And a recording surface such that the three beams that have passed through the hologram element are approximately parallel to the optical axis direction and the reflection direction of the laser beam that is output to the side. A converging optical system that converges on the optical recording medium that is arranged, and on the upper flat surface portion that receives the three beams reflected by the optical recording medium and diffracted to the side of the diffraction grating by the hologram element, or A signal detection photodetector provided on the other upper flat surface of the substrate parallel to the upper flat surface, and between the reflection type diffraction grating and the transmission hologram element or the transmission type. An optical pickup device characterized in that a reflecting means is provided between the hologram element and the converging optical system. 5. The optical pickup device according to claim 1, wherein the photodetection section is provided behind the reflection type diffraction grating. 6. The light according to claim 1, 2, 3, or 4, wherein the semiconductor laser device, the reflection type diffraction grating, and the photodetector are provided in this order on a substantially straight line. Pickup device. 7. A signal detection photodetection unit for receiving the three beams reflected by the optical recording medium and diffracted by the hologram element to the other side of the diffraction grating is provided on the substrate. Claims 1, 2, 3, 4, 5 characterized in that
Alternatively, the optical pickup device according to item 6. 8. The upper flat surface portion for receiving the three beams reflected by the optical recording medium and diffracted to the other side of the diffraction grating by the hologram element, or parallel to the upper flat surface portion. The optical pickup device according to claim 2 or 4, wherein another photodetector for signal detection is provided on another upper flat surface portion of the base. 9. The reflection type diffraction grating is supported by an inclined portion provided in a part of a base body.
2. The optical pickup device described in 2, 3, 4, 5, 6, 7 or 8. 10. The optical pickup device according to claim 9, wherein the inclined portion is formed by being recessed in the base body.