JP2012150853A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device capable of performing reading operation of signals recorded on optical disks with different standards by three laser beams with different wavelengths.SOLUTION: A photodetector is provided in which laser beams emitted from a three-wavelength laser diode are collected on signal recording layers provided to a first optical disk, a second optical disk, and a third optical disk, and a first light receiving unit 12a for receiving return light of a first laser beam, a second light receiving unit 12b for receiving return light of a second laser beam, and a third light receiving unit 12c for receiving return light of a third laser beam, the laser beams being from the respective signal recording layers, are provided in one body. The second light receiving unit 12b and the third light receiving unit 12c are composed of four division sensors with four parts, and the first light receiving unit 12a is composed of six or more sensors with three or more parts.

Description

  The present invention relates to an optical pickup device that performs reading operation of a signal recorded on an optical disc and recording operation of a signal on an optical disc by laser light.

  2. Description of the Related Art Optical disk apparatuses that can perform signal reading operation and signal recording operation by irradiating a signal recording layer of an optical disk with laser light emitted from an optical pickup device have become widespread.

  As an optical disk apparatus, an apparatus using an optical disk called a CD or a DVD is generally widespread. Recently, an optical disk with improved recording density, that is, an apparatus using a Blu-ray standard optical disk has been developed.

  As a laser beam for performing a read operation of a signal recorded on a CD standard optical disc, an infrared light having a wavelength of 785 nm is used. As a laser beam for performing a read operation of a signal recorded on a DVD standard optical disc, , Red light having a wavelength of 655 nm is used.

  Further, the thickness of the transparent protective layer provided between the signal recording layer and the surface of the optical disc in the CD standard optical disc is 1.2 mm, and is used to read out signals from the signal recording layer. The numerical aperture of the objective lens to be set is set to 0.47. The thickness of the transparent protective layer provided between the signal recording layer in the DVD standard optical disc and the surface of the optical disc is 0.6 mm, and is used to read out signals from the signal recording layer. The numerical aperture of the objective lens to be set is set to 0.6.

  For such CD standard and DVD standard optical disks, the laser light for performing the read operation of the signals recorded on the Blu-ray standard optical disk is a laser light having a short wavelength, for example, a blue-violet light having a wavelength of 405 nm. It is used.

  The thickness of the protective layer provided on the upper surface of the signal recording layer in the Blu-ray standard optical disc is 0.1 mm, and the aperture of the objective lens used to read out signals from the signal recording layer The number is set to 0.85.

  The diameter of a laser spot generated by reading a signal recorded on a signal recording layer provided on a Blu-ray standard optical disc or by condensing a laser beam to record a signal on the signal recording layer Need to be small. The objective lens used to obtain a desired laser spot shape has a feature that not only the numerical aperture is increased but also the focal length is shortened, so that the radius of curvature of the objective lens is reduced.

  An optical disc apparatus capable of reading and recording signals recorded on all the optical discs of the CD standard, the DVD standard, and the Blu-ray standard described above has been commercialized, and is incorporated into such an optical disc apparatus. As an optical pickup device, a laser diode that emits a first laser beam that performs an operation of reading a signal recorded on a Blu-ray standard optical disc, and the first laser beam emitted from the laser diode is condensed on a signal recording layer. Two wavelengths for emitting a first objective lens, a second laser beam for performing a read operation of a signal recorded on a DVD standard optical disc, and a third laser beam for performing a read operation of a signal recorded on a CD standard optical disc Laser diode, and second and third laser beams Optical pickup device in which the second objective lens is incorporated for converging the signal recording layer of the click is generally employed (see Patent Document 1.).

  An optical pickup device configured to be able to read out signals recorded on three optical discs having different standards includes a laser diode that emits a first laser beam as described in Patent Document 1. In general, two laser diodes of two-wavelength laser diodes that emit two laser beams, ie, a second laser beam and a third laser beam, are used. Recently, a first laser beam, a second laser beam, and a third laser beam are used. There has been proposed an optical pickup device using a three-wavelength laser diode configured to emit three laser beams having different wavelengths of laser beams (see Patent Document 2).

  An optical pickup device irradiates a photodetector with return light reflected from a signal recording layer, and performs a focus control operation, a tracking control operation, and a signal demodulation operation using a signal obtained from the photodetector. It is configured to obtain a signal.

  Such an optical pickup device is configured to irradiate return light to a sensor constituting the photodetector, but it is necessary to accurately perform the irradiation position of the return light on the sensor. However, the irradiation position of the return light with respect to the sensor may be shifted due to a displacement of the mounting position of each optical component constituting the optical system, and an operation called a so-called XY position adjustment is performed. .

  Even if such XY position adjustment is performed, the irradiation position of the return light cannot be adjusted to the optimum position, or the position of the photodetector cannot be adjusted in some cases, and the problem is solved. As a method, a technique for adjusting the level of a signal obtained from a sensor constituting a photodetector has been proposed (see Patent Document 3).

JP 2010-61781 A JP 2010-27148 A JP 2007-12200 A

  An optical pickup device using a three-wavelength laser diode as described in Patent Document 2 will be described with reference to FIGS.

  In FIG. 5, reference numeral 1 denotes a first laser chip that generates and emits first laser light that is blue-violet light having a wavelength of 405 nm, for example, a second laser chip that generates and emits second laser light that is red light having a wavelength of 655 nm. And, for example, a three-wavelength laser diode in which a third laser chip that generates and emits third laser light that is infrared color light having a wavelength of 785 nm is housed in the same case.

  Reference numeral 2 denotes a diffraction grating on which the first laser beam, the second laser beam, and the third laser beam emitted from the three-wavelength laser diode 1 are incident, and each laser beam having a different wavelength is converted into a main beam that is zero-order light, It comprises a diffraction grating portion 2a that separates two sub-beams that are + 1st order light and −1st order light, and a ½ wavelength plate 2b that converts incident laser light into linearly polarized light in the S direction.

  Reference numeral 3 denotes a first laser beam that reflects S-polarized light of the first laser beam, the second laser beam, and the third laser beam that is incident through the diffraction grating 2 and that is reflected from the optical disk through an optical path that will be described later. This is a polarization beam splitter in which a control film 3a that transmits P-polarized light that is return light of the second laser light and the third laser light is formed.

  4 is provided at a position where the first laser beam, the second laser beam, and the third laser beam reflected by the polarizing beam splitter 3 are incident, and is incident in correspondence with laser beams having three different wavelengths. This is a three-wavelength-compatible quarter-wave plate that functions to convert laser light from linearly polarized light to circularly polarized light, and conversely from circularly polarized light to linearly polarized light.

  Reference numeral 5 denotes a collimator lens that receives the first laser light, the second laser light, and the third laser light transmitted through the quarter-wave plate 4 and converts the incident laser light into parallel light. The spherical aberration caused by the thickness of the protective layer of the optical disk is corrected by the displacement operation in the direction of the optical axis 5. Reference numeral 6 denotes an aberration correction motor that displaces the collimating lens 5 in the optical axis direction.

  Reference numeral 7 denotes a first objective lens that focuses the first laser beam on the signal recording layer L1 provided on the first optical disc D1 (see FIG. 6). Reference numeral 8 denotes a second laser beam provided on the second optical disc D2. This is a second objective lens for two wavelengths that focuses the signal recording layer L2 and focuses the third laser beam on the signal recording layer L3 provided on the third optical disc D3. In such a configuration, the first objective lens 7 and the second objective lens 8 are, for example, displaced by the four support wires in the focusing direction perpendicular to the surface of the optical disc and the tracking in the radial direction of the optical disc. It is mounted on a member called a lens holder that is supported so that it can be displaced in the direction.

  The first laser light, the second laser light, and the third laser light transmitted through the collimator lens 5 are configured to be guided to the first objective lens 7 and the second objective lens 8 by the optical system shown in FIG. . In FIG. 6, reference numeral 9 denotes a wavelength selective element that is configured to transmit the first laser light and reflect the second laser light and the third laser light toward the second objective lens 8. Reference numeral 10 denotes a rising mirror that reflects the first laser beam transmitted through the wavelength selective element 9 toward the first objective lens 7. Since such a configuration is the same as the technique described in Patent Document 1, the description thereof is omitted.

  In such a configuration, the first laser light transmitted through the collimating lens 5 is transmitted through the wavelength selective element 9 and reflected by the rising mirror 10 to be incident on the first objective lens 7. Thus, the first laser light incident on the first objective lens 7 is condensed on the signal recording layer L1 provided on the first optical disc D1 by the condensing operation of the first objective lens 7. Become.

  The second laser light transmitted through the collimating lens 5 is reflected by the wavelength selective element 9 and is incident on the second objective lens 8. Thus, the second laser light incident on the second objective lens 8 is condensed on the signal recording layer L2 provided on the second optical disc D2 by the condensing operation of the second objective lens 8. Become. Then, the third laser light transmitted through the collimating lens 5 is reflected by the wavelength selective element 9 and is incident on the second objective lens 8. Thus, the third laser light incident on the second objective lens 8 is condensed on the signal recording layer L3 provided on the third optical disc D3 by the condensing operation of the second objective lens 8. Become.

  In such a configuration, the first laser light emitted from the first laser chip incorporated in the three-wavelength laser diode 1 is the diffraction grating 2, the polarization beam splitter 3, the quarter wavelength plate 4, the collimating lens 5, the wavelength. After being incident on the first objective lens 7 through the selective element 9 and the rising mirror 10, the light is condensed on the signal recording layer L1 provided on the first optical disc D1 by the light collecting operation of the first objective lens 7. Although it is irradiated as a spot, the first laser light irradiated to the signal recording layer L1 is reflected as return light by the signal recording layer L1.

  The second laser light emitted from the second laser chip incorporated in the three-wavelength laser diode 1 is a diffraction grating 2, a polarizing beam splitter 3, a quarter wavelength plate 4, a collimating lens 5, and a wavelength selective element. After being incident on the second objective lens 8 via 9, the signal recording layer L2 provided on the second optical disc D2 is irradiated as a focused spot by the focusing operation of the second objective lens 8. The second laser light applied to the signal recording layer L2 is reflected as return light by the signal recording layer L2.

  The third laser light emitted from the third laser chip incorporated in the three-wavelength laser diode 3 is a diffraction grating 2, a polarizing beam splitter 3, a quarter-wave plate 4, a collimating lens 5, and a wavelength selective element. 9, after being incident on the second objective lens 8 via 9, the signal recording layer L3 provided on the third optical disc D3 is irradiated as a focused spot by the focusing operation of the second objective lens 8. The third laser light applied to the signal recording layer L3 is reflected as return light by the signal recording layer L3.

  The return light of the first laser beam reflected from the signal recording layer L1 of the first optical disc D1 passes through the first objective lens 7, the rising mirror 10, the wavelength selective element 9, the collimator lens 5, and the quarter wavelength plate 4. The light enters the polarizing beam splitter 3. The return light incident on the polarizing beam splitter 3 in this way is changed to linearly polarized light in the P direction by the phase changing operation by the quarter wavelength plate 4. Therefore, the return light of the first laser light is not reflected by the control film 3a of the polarizing beam splitter 3, but passes through the polarizing beam splitter 3 as control laser light.

  The return light of the second laser light reflected from the signal recording layer L2 of the second optical disc D2 passes through the second objective lens 8, the wavelength selective element 9, the collimating lens 5 and the quarter wavelength plate 4 and is a polarization beam splitter. 3 is incident. The return light incident on the polarizing beam splitter 3 in this way is changed to linearly polarized light in the P direction by the phase changing operation by the quarter wavelength plate 4. Therefore, the return light of the second laser light is not reflected by the control film 3a of the polarizing beam splitter 3, but passes through the polarizing beam splitter 3 as control laser light.

  Then, the return light of the third laser light reflected from the signal recording layer L3 of the third optical disc D3 passes through the second objective lens 8, the wavelength selective element 9, the collimating lens 5, and the quarter wavelength plate 4 to the polarization beam splitter. 3 is incident. The return light incident on the polarizing beam splitter 3 in this way is changed to linearly polarized light in the P direction by the phase changing operation by the quarter wavelength plate 4. Therefore, the return light of the third laser light is not reflected by the control film 3a of the polarization beam splitter 3, but passes through the polarization beam splitter 3 as control laser light.

  Reference numeral 11 denotes a sensor lens to which a control laser beam, which is a return light transmitted through the control film 3a of the polarization beam splitter 3, is incident. The control laser 11 generates a signal for performing a focus control operation and a tracking control operation. It acts on light.

  Reference numeral 12 denotes a photodetector that is irradiated with control laser light through the sensor lens 11, and a known quadrant sensor or the like is provided corresponding to the first laser light, the second laser light, and the third laser light. A focus error signal generation operation for performing a signal generation operation associated with a read operation of a signal recorded on the signal recording layer of the optical disc by the main beam irradiation operation and a focusing control operation by the astigmatism method, and two sub-beams A tracking error signal generating operation for performing a tracking control operation by an irradiation operation is performed. Since such control operations for generating various signals are well known, the description thereof is omitted.

  A three-wavelength laser diode 1, a first laser beam, a second laser beam, and three laser chips that emit a first laser beam, a second laser beam, and a third laser beam having different wavelengths are provided in the same housing. The optical pickup device using the photodetector 12 in which the sensor corresponding to the return light of the third laser light is provided in the same casing is configured as described above. Next, the three-wavelength laser diode 1 is used. The photodetector 12 will be described with reference to FIGS.

  FIG. 3 shows the arrangement of the laser chips incorporated in the three-wavelength laser diode 1, wherein 1a is a first laser chip that emits a first laser beam having a short wavelength, and 1b has a wavelength that is shorter than that of the first laser beam. A second laser chip 1c that emits a long second laser beam is a third laser chip that emits a third laser beam having a wavelength longer than that of the second laser beam.

  In such a configuration, the second laser chip 1b and the third laser chip 1c are manufactured on a single substrate by a monolithic technique that is a semiconductor technique, and the first laser chip 1a includes the second laser chip 1b and the second laser chip 1b. The third laser chip 1c is formed on a different substrate from the substrate on which the third laser chip 1c is formed, and both are provided in one housing by a hybrid technique.

  Since the second laser chip 1b and the third laser chip 1c incorporated in the three-wavelength laser diode 1 are manufactured by the monolithic technique as described above, the positional relationship between the two laser chips 1b and the third laser chip 1c is arranged at an accurate position with little error. However, since the first laser chip 1a is incorporated into the housing of the three-wavelength laser diode 1 by the hybrid technique, an error occurs in the arrangement thereof.

  FIG. 4 shows the arrangement of a four-divided sensor incorporated in the photodetector 12, wherein 12a is a first light receiving portion provided at a position where the return light of the first laser light is irradiated, and 12b is a first light receiving portion. A second light receiving portion provided at a position where the return light of the two laser beams is irradiated, and 12c is a third light receiving portion provided at a position where the return light of the third laser light is irradiated, and an arrow X It is arranged linearly in the direction.

  FIG. 4 shows a light receiving portion for a main beam irradiated with a main beam constituting the first laser light, the second laser light, and the third laser light. The light receiving portion for the sub beam is a light receiving portion for the main beam. It is arrange | positioned in the optimal position of the arrow Y direction with respect to the part. That is, when the main beam of the laser beam is irradiated at the optimum position with respect to the light receiving portion for the main beam irradiated with the main beam, the sub beam is placed at the optimum position with respect to the light receiving portion for the sub beam. It is supposed to be irradiated.

  The first light receiving unit 12a irradiated with the return light of the first laser beam, the second light receiving unit 12b irradiated with the return beam of the second laser beam, and the third light receiving unit irradiated with the return light of the third laser beam. The part 12c is configured by a sensor divided into four as shown in the figure. A focus error signal or the like is generated in a well-known manner using a signal obtained from such a sensor divided into four.

  In FIG. 4, M1 is a first laser spot generated on the first light receiving unit 12a when irradiated with the return light of the first laser beam, and M2 is irradiated with the return light of the second laser beam and irradiated on the second light receiving unit 12b. A second laser spot generated above, M3, is a third laser spot generated on the third light receiving unit 12c by irradiation with the return light of the third laser light.

  FIG. 4 shows a quadrant sensor in which the first laser spot M1, the second laser spot M2, and the third laser spot M3 are provided in the first light receiving unit 12a, the second light receiving unit 12b, and the third light receiving unit 12c, respectively. It shows a state in which the central portion of the four sensors, that is, the optimum position is irradiated.

  The XY position adjustment for adjusting the position of the photodetector 12 is performed by the assembling work of the optical pickup device. Such adjustment operation is performed with reference to the second light receiving unit 12b irradiated with the return light of the second laser light. Is called. That is, first, the position of the photodetector 12 is adjusted so that the second laser spot M2 generated by the return light of the second laser light is positioned at the center of the four-divided sensor constituting the second light receiving unit 12b. Work is done.

  After such adjustment operation is performed, the photodetector 12 is rotated about the second light receiving unit 12b, and the first laser spot M1 and the third laser beam returned by the return light of the first laser beam are returned. Position adjustment is performed so that the third laser spot M3 generated by the light is irradiated to an optimal position with respect to the first light receiving unit 12a and the third light receiving unit 12c. Such an adjustment operation can be performed by detecting signals obtained from the first light receiving unit 12a and the third light receiving unit 12c. That is, the level of the signal obtained from the sensor constituting each light receiving unit is balanced, but the optical pickup is not necessarily in an optimal position with respect to the first light receiving unit 12a and the third light receiving unit 12c. It is set in a range where the control operation can be performed without any trouble.

  Thus, the XY position adjustment of the photodetector 12 is performed. At this time, the second laser chip 1b that generates and emits the second laser light and the third laser chip 1c that generates and emits the third laser light are described above. In this way, the positional relationship between the two can be set accurately. Therefore, for example, if the XY position adjustment is performed so that the position of the second laser spot M2 generated by the return light of the second laser light becomes the center of the second light receiving part 12b, that is, the optimum position, the third laser light is obtained. The position of the third laser spot M3 generated by the return light can be arranged at the center of the third light receiving unit 12c, that is, at the optimum position.

  FIG. 2 shows a state in which the above-described adjustment operation is performed. The second laser spot M2 and the third laser spot M3 are irradiated and generated at the optimal positions of the second light receiving unit 12b and the third light receiving unit 12c. . In the state in which such XY position adjustment is performed, the first laser spot M1 generated by irradiation with the return light of the first laser beam may deviate from the optimal position of the first light receiving unit 12a as illustrated. . The reason why the first laser spot M1 deviates from the optimum position of the first light receiving unit 12a is that the position of the first laser chip 1a incorporated in the three-wavelength laser diode 1 is relative to the second laser chip 1b and the third laser chip 1c. There is a deviation from the optimum setting position.

  The magnitude of the positional deviation of the first laser chip 1a with respect to the second laser chip 1b is large with respect to the X direction shown in FIG. 3 and small in the Y direction.

  When the position of the first laser spot M1 is deviated from the optimum position, the positional relationship between the second light receiving unit 12b and the second laser spot M2 or the position between the third light receiving unit 12c and the third laser spot M3. Although the position adjustment in the X direction is performed while considering the relationship, there are cases where adjustment is impossible, and in such a case, there is a problem that the product is disposed as a defective product.

  The present invention is intended to provide an optical pickup device that can solve such a problem.

  The present invention includes a first laser chip that emits a first laser light having a short wavelength, a second laser chip that emits a second laser light having a longer wavelength than the first laser light, and a third laser having a longer wavelength than the second laser light. A first optical disc, a second optical disc, and a second optical disc having different distances from the surface of the optical disc to the signal recording layer for each laser beam emitted from a three-wavelength laser diode in which a third laser chip for emitting light is provided in the same housing; A first light-receiving unit that collects light on the signal recording layer provided on the third optical disc and receives the return light of the first laser light reflected from each signal recording layer, and a first light-receiving unit that receives the return light of the second laser light. The second light receiving unit and the third light receiving unit that receives the return light of the third laser light include a photodetector arranged in a straight line in the same housing, and the second light receiving unit and the third light receiving unit. It is characterized in that constituted by 6 or more sensors which are divided into three or more divisions of the first light receiving portion in the orientation as well as constituted by the four-divided sensor divided into four light portions.

  Further, the present invention is characterized in that each sensor is provided with a gain adjustment circuit that adjusts the level of a signal obtained from each sensor constituting the first light receiving unit.

  The present invention is characterized in that the division width in the arrangement direction of the first light receiving portion is set based on the size of the arrangement deviation of the laser chip incorporated in the three-wavelength laser diode.

  In addition, the present invention is characterized in that the position adjustment of the photodetector is performed with reference to the second light receiving unit.

  The present invention includes a first laser chip that emits a first laser light having a short wavelength, a second laser chip that emits a second laser light having a longer wavelength than the first laser light, and a third laser having a longer wavelength than the second laser light. A first optical disc, a second optical disc, and a second optical disc having different distances from the surface of the optical disc to the signal recording layer for each laser beam emitted from a three-wavelength laser diode in which a third laser chip for emitting light is provided in the same housing; A first light-receiving unit that collects light on the signal recording layer provided on the third optical disc and receives the return light of the first laser light reflected from each signal recording layer, and a first light-receiving unit that receives the return light of the second laser light. The second light receiving unit and the third light receiving unit that receives the return light of the third laser light include a photodetector arranged in a straight line in the same housing, and the second light receiving unit and the third light receiving unit. Since the light part is composed of four divided sensors and the first light receiving part is composed of six or more sensors divided into three or more in the arrangement direction, it is incorporated into a three-wavelength laser diode. The signal generation operation can be performed accurately even if the position of the laser spot of the return light is deviated from the light receiving portion incorporated in the photodetector due to the positional deviation of the laser chip. Therefore, according to the present invention, signals recorded on optical discs of three different standards using a three-wavelength laser diode incorporating three laser chips and one photodetector incorporating three light receiving units. It is possible to provide an optical pickup device capable of performing the reading operation.

It is the schematic which shows one Example of the photodetector which concerns on the optical pick-up apparatus of this invention. It is the schematic which shows the photodetector which concerns on the conventional optical pick-up apparatus. It is the schematic which shows one Example of the 3 wavelength laser diode which concerns on the optical pick-up apparatus of this invention. It is the schematic which shows the photodetector which concerns on the conventional optical pick-up apparatus. It is the schematic which shows the optical system of an optical pick-up apparatus. It is the schematic which shows the optical system of an optical pick-up apparatus.

  The present invention relates to an optical pickup device in which a three-wavelength laser diode that emits laser beams of three different wavelengths and a photodetector including three light-receiving units that are irradiated with return light of each wavelength are incorporated.

  FIG. 1 is a schematic view showing an embodiment of a photodetector according to the optical pickup device of the present invention. In the present invention, the first light receiving unit 12a constituting the photodetector 12 is divided into four in the direction of the arrow X, which is the arrangement direction of the first light receiving unit 12a, the second light receiving unit 12b, and the third light receiving unit 12c, as illustrated. In addition, each sensor is provided with a gain adjustment circuit (not shown) that adjusts the level of a signal obtained from each of the eight divided sensors formed by dividing into two in the arrow Y direction. . Since such a gain adjustment circuit may use a technique as described in Patent Document 3, description thereof will be omitted.

  When the positions of the second laser spot M2 and the third laser spot M3 with respect to the second light receiving part 12b and the third light receiving part 12c are adjusted to the optimum positions by the XY position adjustment, the first light receiving part 12a with respect to the first light receiving part 12a is adjusted. When the position of the laser spot M1 is shifted as shown in FIG. 2, the present invention is in a state as shown in FIG.

  As is apparent from the drawings, the first laser spot M1 is in a state of being irradiated to the sensors A, B, C, and D among the eight divided sensors constituting the first light receiving unit 12a. In such a state, since the sensors A, B, C, and D are in a state of acting as a quadrant sensor, a control signal such as a focus error signal is obtained by using a signal obtained from the sensors A, B, C, and D. Can be obtained.

  In this way, control signals can be obtained from the sensors A, B, C, and D, but the position of the first laser spot M1 is rarely located at the center of the sensors A, B, C, and D. is there. Therefore, the levels of signals obtained from the sensors A, B, C, and D are different.

  Therefore, in the photodetector of the present invention, each sensor has a gain adjustment circuit for adjusting the level of the output signal so that the levels of the signals obtained from the sensors A, B, C, and D are the same. Is provided. By providing a gain adjustment circuit that adjusts the level of a signal obtained from each sensor, the sensors A, B, C, and D can be operated as a four-divided sensor.

  In the present embodiment, the first light receiving portion 12a is divided into four in the direction of the arrow X. The number of divisions is the size of the shift of the first laser spot M1, that is, the first laser chip 1a incorporated in the three-wavelength laser diode 1. Are set based on the size of the displacement of the optical system, the size of the shift of the optical system, and the diameter of the first laser spot M1, and may be three or more.

  The width d of the sensor provided by the division of the first light receiving unit 12a is the same as the number of divisions, the magnitude of the displacement of the first laser chip 1a, the magnitude of the deviation of the optical system, and the diameter of the first laser spot M1. It will be set based on.

  In the photodetector having the above-described configuration, the sensor that receives light differs depending on the displacement position of the first laser spot M1 in the X direction and the Y direction. Therefore, an offset is generated in the detection output based on the difference between the light receiving sensors. become. In the present invention, the offset is corrected and adjusted by the gain adjustment circuit for adjusting the output of each sensor as described above. Therefore, according to the present invention, three standard laser diodes incorporating three laser chips that emit laser beams of different wavelengths and one photodetector incorporating three light receiving units are used. It is possible to provide an optical pickup device capable of performing a reading operation of a signal recorded on an optical disc.

  Although the description has been given of the case where the optical pickup apparatus that performs the reading operation of the signal recorded on the optical disc of the CD standard, the DVD standard, and the Blu-ray standard has been described, the reading operation of the signal recorded on the optical disc of another different standard has been described. It can also be implemented in an optical pickup device that can be used.

  In addition, two objective lenses are provided for condensing three laser beams on the signal recording layers provided on three types of optical discs with different standards. However, one objective lens is provided on three types of optical discs. The present invention can also be implemented in an optical pickup device configured to focus three laser beams on a signal recording layer.

DESCRIPTION OF SYMBOLS 1 3 wavelength laser diode 3 Polarizing beam splitter 4 1/4 wavelength plate 5 Collimating lens 7 1st objective lens 8 2nd objective lens 12 Photodetector

Claims (4)

A first laser chip that emits a first laser beam having a shorter wavelength, a second laser chip that emits a second laser beam that has a longer wavelength than the first laser beam, and a third laser beam that has a longer wavelength than the second laser beam. Each laser beam emitted from a three-wavelength laser diode in which the third laser chip is provided in the same housing is applied to the first optical disc, the second optical disc, and the third optical disc that have different distances from the surface of the optical disc to the signal recording layer. A first light receiving unit that collects light on the provided signal recording layer and receives the return light of the first laser light reflected from each signal recording layer; a second light receiving unit that receives the return light of the second laser light; In the optical pickup device including the photodetector in which the third light receiving portion that receives the return light of the third laser light is linearly arranged in the same housing, The two light receiving portions and the third light receiving portion are configured by four divided sensors divided into four, and the first light receiving portion is configured by six or more sensors divided in three or more divisions in the arrangement direction. Optical pickup device. 2. The optical pickup device according to claim 1, wherein each sensor is provided with a gain adjustment circuit for adjusting a level of a signal obtained from each sensor constituting the first light receiving unit. 2. The optical pickup device according to claim 1, wherein the division width in the arrangement direction of the first light receiving unit is set on the basis of the arrangement deviation of the laser chip incorporated in the three-wavelength laser diode. 2. The optical pickup device according to claim 1, wherein the position of the photodetector is adjusted based on the second light receiving unit.

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