JP2012059338A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device that reads out signals recorded on optical disks according to different standards by using three laser beams having different wave lengths.SOLUTION: The optical pickup device includes: an AS plate 21 for applying astigmatism to a first laser beam and irradiating a first photo-detector 22 with the first laser beam; and a half mirror 17 for reflecting second and third laser beams radiated from a two-wavelength laser diode 3 toward an objective lens and transmitting the second and third laser beams reflected from an optical disk toward a second photo-detector 26. The second and third laser beams reflected by the half mirror 17 is reflected by the AS plate 21 to be incident on a polarization member, and the polarization member combines the optical paths of the first, second, and third laser beams.

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. in use.

  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.).

  Further, the first laser beam, the second laser beam, and the third laser beam having different wavelengths are combined into one objective lens, that is, a three-wavelength compatible objective lens, so that the signal recording layer of the first optical disc, the signal recording layer of the second optical disc, 3 A technique has been developed in which light is focused on a signal recording layer of an optical disc (see Patent Document 2).

JP 2010-61781 A JP 2006-236414 A

  A laser diode that emits a laser beam of one wavelength, a two-wavelength laser diode that emits a laser beam of two wavelengths, and a reading operation of signals recorded on three optical discs of different standards by two objective lenses In the optical pickup apparatus configured as described above, when an optical path is provided for each laser beam, many optical parts are required, which is not only expensive, but also cannot be reduced in size.

  As a method for solving such a problem, as described in Patent Document 1, there is provided a technique that doubles as an optical path and also serves as a photodetector. However, such a technique has a problem that the manufacturing cost is high because two polarization beam splitters are used as optical elements for optical path synthesis.

  As a method for solving such a problem, the optical paths of the first laser beam, the second laser beam, and the third laser beam are made common by using one polarization beam splitter and one half mirror. A conventional optical pickup device having such a configuration will be described with reference to FIGS.

  In FIG. 3, reference numeral 1 denotes a laser diode that generates and emits first laser light having a wavelength of 405 nm, for example, blue-violet light, and 2 denotes a first diffraction grating on which the first laser light emitted from the laser diode 1 is incident. There is a diffraction grating section 2a that separates laser light into zero-order main beam, + 1st-order light, and two sub-beams that are −1st-order light, and 1 that converts incident laser light into linearly polarized light in the S direction. / 2 wavelength plate 2b.

  3, for example, a first laser element that generates and emits second laser light that is red light having a wavelength of 655 nm and a second laser element that generates and emits third laser light that is infrared light of 785 nm are housed in the same case. This is a two-wavelength laser diode.

  Reference numeral 4 denotes a second diffraction grating on which the second laser light emitted from the first laser element incorporated in the two-wavelength laser diode 3 and the third laser light emitted from the second laser element are incident. A diffraction grating portion 4a that separates light into a main beam that is zero-order light, two sub-beams that are + 1st-order light, and two sub-beams that are −1st-order light, and a ½ wavelength that converts incident laser light into linearly polarized light in the S direction It consists of a plate 4b.

Reference numeral 5 denotes a divergence lens provided at a position where the second laser light and the third laser light emitted from the two-wavelength laser diode 3 are incident through the second diffraction grating 4, and is incident divergent light. It functions to adjust the divergence angle of the laser beam.

  Reference numeral 6 denotes a first laser beam, a second laser beam, and a third laser beam that reflect the S-polarized light of the first laser beam incident through the first diffraction grating 2 and reflected from the optical disk through an optical path to be described later. This is a half mirror that transmits the P-polarized light that is the return light. 7 reflects the S-polarized light of the second laser beam and the third laser beam incident through the second diffraction grating 4 and the divergence lens 5 and the first laser beam incident after being reflected by the half mirror 6. It is a polarization beam splitter that transmits P-polarized light that is transmitted through and reflected from the optical disk and that is return light of the first laser light, the second laser light, and the third laser light.

  In the polarizing beam splitter 7 having such a configuration, a part of the S-polarized light of the second laser light and the third laser light incident through the second diffraction grating 4 and the divergence lens 5 is transmitted and reflected from the half mirror 6. Is configured to reflect a portion of the S-polarized light of the first laser light incident thereon. 8 is a front monitor diode provided at a position where the first laser light reflected by the polarizing beam splitter 7, the second laser light transmitted through the polarizing beam splitter 7, and the third laser light are irradiated; A detection signal corresponding to the output of each laser beam is output. That is, the laser output can be controlled to a desired laser output by using the detection signal obtained from the front monitor diode 8.

  9 is provided at a position where the first laser light transmitted through the polarizing beam splitter 7, the second laser light reflected by the polarizing beam splitter 7 and the third laser light are incident, and having three different wavelengths. This is a three-wavelength type quarter-wave plate that functions to convert incident laser light corresponding to laser light from linearly polarized light to circularly polarized light, and conversely from circularly polarized light to linearly polarized light.

  Reference numeral 10 denotes a collimator lens for converting the incident laser light into parallel light as the laser light transmitted through the quarter-wave plate 9 is incident thereon. The collimating lens 10 is displaced in the optical axis direction by the displacement operation of the optical disk. The spherical aberration generated based on the thickness of the protective layer is corrected.

  Reference numeral 11 denotes a first objective lens that condenses the first laser beam on the signal recording layer L1 provided on the first optical disc D1 (see FIG. 2), and reference numeral 12 denotes a second laser beam provided on the second optical disc D2. The second objective lens focuses light on the signal recording layer L2 and focuses the third laser light on the signal recording layer L3 provided on the third optical disc D3. In such a configuration, the first objective lens 11 and the second objective lens 12 are, for example, displaced by a four support wires in a focusing direction perpendicular to the surface of the optical disc and in a 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 collimating lens 10 are configured to be guided to the first objective lens 11 and the second objective lens 12 by the optical system shown in FIG. . In FIG. 2, reference numeral 13 denotes a wavelength selective element, which is configured to transmit the first laser light and reflect the second laser light and the third laser light toward the second objective lens 12. Reference numeral 14 denotes a rising mirror that reflects the first laser light transmitted through the wavelength selective element 13 toward the first objective lens 11. Such a configuration is the same as the technique described in Patent Document 1.

In such a configuration, the first laser light transmitted through the collimator lens 10 is transmitted through the wavelength selective element 13, reflected by the rising mirror 14, and incident on the first objective lens 11. Thus, the first laser light incident on the first objective lens 11 is condensed on the signal recording layer L1 provided on the first optical disc D1 by the condensing operation of the first objective lens 11. Become.

  The second laser light transmitted through the collimator lens 10 is reflected by the wavelength selective element 13 and is incident on the second objective lens 12. Thus, the second laser light incident on the second objective lens 12 is condensed on the signal recording layer L2 provided on the second optical disc D2 by the condensing operation of the second objective lens 12. Become. Then, the third laser light transmitted through the collimating lens 10 is reflected by the wavelength selective element 13 and is incident on the second objective lens 12. Thus, the third laser light incident on the second objective lens 12 is condensed on the signal recording layer L3 provided on the third optical disc D3 by the condensing operation of the second objective lens 12. Become.

  In such a configuration, the first laser light emitted from the laser diode 1 is transmitted through the first diffraction grating 2, the half mirror 6, the polarization beam splitter 7, the quarter wavelength plate 9, the collimating lens 10, the wavelength selective element 13, and the like. After being incident on the first objective lens 11 via the rising mirror 14, the signal recording layer L1 provided on the first optical disc D1 is irradiated as a focused spot by the focusing operation of the first objective lens 11. However, the first laser light applied to the signal recording layer L1 is reflected as return light by the signal recording layer L1.

  The second laser light emitted from the first laser element of the two-wavelength laser diode 3 is a second diffraction grating 4, a divergence lens 5, a polarization beam splitter 7, a quarter-wave plate 9, a collimating lens 10, and a wavelength selection. After being incident on the second objective lens 12 via the directional element 13, 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 12. 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 second laser element of the two-wavelength laser diode 3 is a second diffraction grating 4, a divergence lens 5, a polarization beam splitter 7, a quarter-wave plate 9, a collimating lens 10, and a wavelength selection. After being incident on the second objective lens 12 via the directional element 13, 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 12. 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 is a first objective lens 11, a rising mirror 14, a wavelength selective element 13, a collimating lens 10, a quarter wavelength plate 9, and The light enters the half mirror 6 through the polarization beam splitter 7. The return light incident on the half mirror 6 in this way is changed to linearly polarized light in the P direction by the phase changing operation by the quarter wavelength plate 9. Therefore, the return light of the first laser light is not reflected by the half mirror 6, but passes through the half mirror 6 as control laser light.

  The return light of the second laser light reflected from the signal recording layer L2 of the second optical disk D2 is the second objective lens 12, the wavelength selective element 13, the collimating lens 10, the quarter wavelength plate 9, and the polarization beam splitter. 7 enters the half mirror 6. The return light incident on the half mirror 6 in this way is changed to linearly polarized light in the P direction by the phase changing operation by the quarter wavelength plate 9. Therefore, the return light of the second laser light is not reflected by the half mirror 6, but passes through the half mirror 6 as control laser light.

  The return light of the third laser light reflected from the signal recording layer L3 of the third optical disc D3 is the second objective lens 12, the wavelength selective element 13, the collimating lens 10, the quarter wavelength plate 9, and the polarization beam splitter. 7 enters the half mirror 6. The return light incident on the half mirror 6 in this way is changed to linearly polarized light in the P direction by the phase changing operation by the quarter wavelength plate 9. Therefore, the return light of the third laser light is not reflected by the half mirror 6, but passes through the half mirror 6 as control laser light.

  Reference numeral 15 denotes an AS plate on which the control laser beam transmitted through the half mirror 6 is incident. The size of the astigmatism generated by the half mirror 6 is a size suitable for generating a focus error signal. In addition to the function of enlarging, the coma aberration generated in the half mirror 6 is corrected. Reference numeral 16 denotes a photodetector that is irradiated with control laser light through the AS plate 15 and is provided with a well-known four-divided sensor or the like. The signal recorded on the signal recording layer of the optical disk by the main beam irradiation operation. A focus error signal generation operation for performing a signal generation operation associated with the readout operation of the lens, a focusing control operation by the astigmatism method, and a tracking error signal generation operation for performing the tracking control operation by the irradiation operation of the two sub beams It is configured. Since such control operations for generating various signals are well known, the description thereof is omitted.

  As described above, the first laser light emitted from the laser diode 1 goes to the signal recording layer L1 of the first optical disc D1, and the second laser light emitted from the second wavelength laser diode 3 records the signal on the second optical disc D2. Comparing the forward path to the layer L2 and the forward path of the third laser light emitted from the two-wavelength laser diode 3 to the signal recording layer L3 of the third optical disc D3, the optical path from the polarization beam splitter 7 to the wavelength selective element 13 is You can see that they are also used.

  Then, the return path of the return light of the first laser light reflected from the signal recording layer L1 of the first optical disk D1 to the photodetector 16, the return of the second laser light reflected from the signal recording layer L2 of the second optical disk D2 Comparing the return path of the light to the photodetector 16 and the return path of the return light of the third laser light reflected from the signal recording layer L3 of the third optical disc D3, the light from the wavelength selective element 13 is compared. It can be seen that the optical path to the detector 16 is also used.

  The conventional optical pickup device shown in FIG. 3 combines the forward path for guiding the laser light to the signal recording layer of the optical disk and the return path for guiding the return light reflected from the signal recording layer of the optical disk to the photodetector 16. The number of optical components can be reduced. As a result, there is an advantage that not only the manufacturing price can be reduced, but also the optical pickup device can be miniaturized.

  In the optical pickup device having such a configuration, the AS plate and the photodetector 16 are shared by all the laser beams of the first laser beam, the second laser beam, and the third laser beam. It is difficult to configure so as to perform a simple detection operation.

  The present invention is intended to provide an optical pickup device that improves such a point.

The present invention relates to a laser diode that emits a first laser beam having a first wavelength for performing a read operation of a signal recorded on a first optical disc having a short distance from the surface of the optical disc to a signal recording layer, and signal recording from the surface of the optical disc. A first laser element that emits a second laser beam having a second wavelength for performing a read operation of a signal recorded on a second optical disc whose distance to the layer is longer than that of the first optical disc; A two-wavelength laser diode provided with a second laser element that emits a third laser beam having a third wavelength for performing a read operation of a signal recorded on a third optical disk whose distance is longer than that of the second optical disk is incorporated. In the optical pickup device, when the first laser light emitted from the laser diode is guided toward the objective lens, A polarizing member for guiding the first laser light reflected from the signal recording layer of the first optical disc in the direction of the first photodetector, and a first laser provided between the polarizing member and the first photodetector. An AS plate for adding astigmatism to the light, and the second laser beam and the third laser beam emitted from the two-wavelength laser diode are reflected in the direction of the objective lens, and the signal recording layer of the second optical disc and the third optical disc A half mirror that transmits the second laser beam and the third laser beam reflected from the signal recording layer in the direction of the second photodetector; a first laser beam that is provided between the polarizing member and the objective lens; A three-wavelength-compatible quarter-wave plate for converting the polarization directions of the second laser beam and the third laser beam from linearly polarized light to circularly polarized light and from circularly polarized light to linearly polarized light; The second laser beam and the third laser beam reflected by the mirror are incident on the polarizing member by being reflected by the AS plate, and the first laser beam, the second laser beam, and the third laser are incident on the polarizing member. It is characterized in that the optical paths of light are synthesized.

  In the present invention, recording is performed on each signal recording layer by focusing the first, second, and third laser beams having different wavelengths on the signal recording layers provided on the first, second, and third optical discs having different standards. In the optical pickup device configured to read out the read signal, the first light detector irradiated with the first laser light and the second light detection irradiated with the second laser light and the third laser light Two optical detectors are provided, and the second laser beam and the third laser beam are provided in the optical path of the first laser beam by using the AS plate used for the detection operation of the first laser beam photodetector. Since the optical paths of the first laser beam, the second laser beam, and the third laser beam are synthesized by being incident on the polarizing member, the optical configuration of the optical pickup device can be simplified. It has the advantage that it can be detected operation by the light detector that is suitable for each of the laser beam not only accurately configured to allow.

It is the schematic which shows one Example of the optical pick-up apparatus which concerns on this invention. It is a figure which shows a part of Example of the optical pick-up apparatus based on this invention. It is the schematic which shows one Example of the conventional optical pick-up apparatus.

  Using a laser diode that generates a single laser beam and a two-wavelength laser diode that generates two laser beams of different wavelengths, it is recorded on a signal recording layer provided on an optical disc of a different standard. It is related with the optical pick-up apparatus comprised so that the read-out operation | movement of the signal may be performed.

  FIG. 1 shows an embodiment of an optical pickup device according to the present invention. The present invention will be described with reference to FIGS. Note that components having the same functions as those of the optical pickup device shown in FIG.

  17 reflects most of the S-polarized light of the second laser beam and the third laser beam incident through the second diffraction grating 4 in the direction of the objective lens and transmits a part thereof as monitor light, and the signal of the second optical disc D2 This is a half mirror that transmits the return light reflected from the recording layer L2 and the signal recording layer L3 of the third optical disc D3.

  Reference numeral 18 denotes a first front monitor diode, which is provided at a position where the second laser light and the third laser light transmitted through the half mirror 17 are irradiated. Therefore, by using the detection signal obtained from the first front monitor diode 18, the output of the second laser light and the third laser light emitted from the two-wavelength laser diode 3 is controlled to be a desired laser output. I can do it.

  Reference numeral 19 denotes a first collimating lens that converts the second laser light and the third laser light reflected by the half mirror into parallel light, and reference numeral 20 denotes a first laser that is S-polarized light incident through the first diffraction grating 2. The first laser beam is reflected from the signal recording layer L1 of the first optical disc D1, the signal recording layer L2 of the second optical disc D2, and the signal recording layer L3 of the third optical disc D3 as described later. The polarization beam splitter transmits the second laser light and the third laser light.

  Reference numeral 21 denotes an AS plate that transmits the first laser beam incident through the polarizing beam splitter 20 and generates astigmatism in the first laser beam. The first laser beam is supplied to the first photodetector 22. Is irradiated as a control laser beam.

  In such a configuration, the second laser light and the third laser light reflected by the half mirror 17 are incident on the AS plate 21 through the first collimating lens 19, and are directed to the polarization beam splitter 20 by the AS plate 21. It is comprised so that it may reflect. According to such a configuration, the polarization beam splitter 20 performs optical path synthesis in which the optical paths of the first laser light, the second laser light, and the third laser light are unified into the same optical path.

  Reference numeral 23 denotes a reflection mirror that reflects the first laser light, the second laser light, and the third laser light incident through the three-wavelength compatible quarter-wave plate 9 in the direction of the objective lens, and a part of the first laser light. Is configured to have wavelength selection characteristics so as to be transmitted as monitor light.

  Reference numeral 24 denotes a second front monitor diode, which is provided at a position where the monitor light of the first laser light transmitted through the reflection mirror 23 is irradiated. Therefore, by using the detection signal obtained from the second front monitor diode 24, the output of the first laser light emitted from the laser diode 1 can be controlled to be a desired laser output.

  Reference numeral 25 denotes a second collimating lens provided between the reflection mirror 23 and the objective lens, and the first laser beam, the second laser beam, and the third laser beam are converted into laser beams by being displaced in the optical axis direction. It is configured to convert into parallel light that suits. Such a displacement operation of the second collimating lens 25 in the optical axis direction is configured to be performed using a stepping motor or the like, but since such a technique is well known, the description thereof is omitted.

  Reference numeral 26 denotes a second photodetector provided at a position where the return light of the second laser light and the third laser light transmitted through the half mirror 17 is irradiated. Astigmatism is added by the half mirror 17. It is comprised so that.

  In such a configuration, the first laser light generated and emitted from the laser diode 1 is the first diffraction grating 2, the polarization beam splitter 20, the quarter wavelength plate 9, the reflection mirror 23, the second collimator lens 25, and the wavelength selectivity. The light is guided to the first objective lens 11 through the element 13 and the rising mirror 14 and is focused on the signal recording layer L1 of the first optical disc D1 by the focusing operation of the first objective lens 11.

  The return light of the first laser beam reflected from the signal recording layer L1 of the first optical disc D1 is a first objective lens 11, a rising mirror 14, a wavelength selective element 13, a second collimating lens 25, a reflecting mirror. 23, the first wavelength detector 22 is irradiated through the quarter-wave plate 9, the polarization beam splitter 20, and the AS plate 21.

  Then, an operation in which a part of the first laser light emitted from the laser diode 1 passes through the reflection mirror 23 and is irradiated to the second front monitor diode 24 is performed.

  As described above, the first laser light emitted from the laser diode 1 is focused on the signal recording layer L1 of the first optical disc D1, and the return light reflected from the signal recording layer L1 is directed to the first photodetector 22. Irradiating operation and irradiating the second front monitor diode 24 with the monitor light are performed, so that the focus control operation, tracking control operation and laser light output control operation are performed on the signal recording layer L1 of the first optical disc D1. The recorded signal can be read out.

  Next, the second laser light generated and emitted from the two-wavelength laser diode 3 is the second diffraction grating 4, the half mirror 17, the first collimating lens 19, the AS plate 21, the polarization beam splitter 20, and the ¼ wavelength plate 9. Then, the light is guided to the second objective lens 12 through the reflecting mirror 23, the second collimating lens 25, and the wavelength selective element 13, and is collected on the signal recording layer L2 of the second optical disc D2 by the condensing operation of the second objective lens 12. Lighted.

  The return light of the second laser beam reflected from the signal recording layer L2 of the second optical disc D2 is the second objective lens 12, the wavelength selective element 13, the second collimator lens 25, the reflection mirror 23, and 1/4. The second light detector 26 is irradiated through the wave plate 9, the polarizing beam splitter 20, the AS plate 21, the first collimating lens 19 and the half mirror 17.

  Then, an operation in which a part of the second laser light emitted from the two-wavelength laser diode 3 passes through the half mirror 17 and is irradiated on the first front monitor diode 18 is performed.

  As described above, the second laser light emitted from the two-wavelength laser diode 3 is focused on the signal recording layer L2 of the second optical disc D2, and the second photodetector of the return light reflected from the signal recording layer L2. 26 and the first front monitor diode 18 are irradiated with the monitor light, so that the signal recording layer of the second optical disc D2 is obtained by performing the focus control operation, tracking control operation and laser light output control operation. The read operation of the signal recorded in L2 can be performed.

  The third laser light generated and emitted from the two-wavelength laser diode 3 is the second diffraction grating 4, the half mirror 17, the first collimating lens 19, the AS plate 21, the polarization beam splitter 20, and the ¼ wavelength plate 9. Then, the light is guided to the second objective lens 12 through the reflection mirror 23, the second collimating lens 25, and the wavelength selective element 13, and is collected on the signal recording layer L3 of the third optical disc D3 by the condensing operation of the second objective lens 12. Lighted.

  The return light of the third laser beam reflected from the signal recording layer L3 of the third optical disc D3 is the second objective lens 12, the wavelength selective element 13, the second collimator lens 25, the reflection mirror 23, and 1/4. The second photodetector 26 is irradiated through the wave plate 9, the polarization beam splitter 20, the AS plate 21, the first collimating lens 19 and the half mirror 17.

  In addition, an operation is performed in which a part of the third laser light emitted from the two-wavelength laser diode 3 passes through the half mirror 17 and is irradiated to the first front monitor diode 18.

  As described above, the third laser light emitted from the two-wavelength laser diode 3 is focused on the signal recording layer L3 of the third optical disk D3, and the second photodetector of the return light reflected from the signal recording layer L3. 26 and the first front monitor diode 18 are irradiated with the monitor light. Therefore, the signal recording layer of the third optical disc D3 is obtained by performing the focus control operation, the tracking control operation, and the laser light output control operation. The read operation of the signal recorded in L3 can be performed.

  In this embodiment, the first objective lens 11 that focuses the first laser beam on the signal recording layer L1 of the first optical disc D1 and the second laser beam are focused on the signal recording layer L2 of the second optical disc D2. The case where the third laser beam is applied to the optical pickup device including the two objective lenses of the second objective lens 12 for condensing the third laser beam on the signal recording layer L3 of the third optical disc D3 has been described. In other words, the present invention can be implemented in an optical pickup device having one objective lens.

  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.

DESCRIPTION OF SYMBOLS 1 Laser diode 3 2 wavelength laser diode 9 1/4 wavelength plate 11 1st objective lens 12 2nd objective lens 17 Half mirror 18 1st front monitor diode 19 1st collimating lens 20 Polarizing beam splitter 21 AS plate 22 1st light detection 24 Second front monitor diode 25 Second collimating lens 26 Second photodetector

Claims (4)

A laser diode that emits a first laser beam having a first wavelength for performing a read operation of a signal recorded on a first optical disc having a short distance from the surface of the optical disc to the signal recording layer, and a distance from the surface of the optical disc to the signal recording layer Is a first laser element that emits a second laser beam of a second wavelength that performs an operation of reading a signal recorded on a second optical disc that is longer than the first optical disc, and the distance from the surface of the optical disc to the signal recording layer is In an optical pickup device incorporating a two-wavelength laser diode provided with a second laser element that emits a third laser beam having a third wavelength for performing a read operation of a signal recorded on a third optical disc longer than two optical discs , Guiding the first laser light emitted from the laser diode toward the objective lens and the first light A polarizing member that guides the first laser light reflected from the signal recording layer of the disk in the direction of the first light detector, and is provided between the polarizing member and the first light detector and is non-visible to the first laser light. An AS plate for adding point aberration, and a second laser beam and a third laser beam emitted from the two-wavelength laser diode are reflected in the direction of the objective lens, and the signal recording layer of the second optical disc and the signal recording layer of the third optical disc The first laser beam and the second laser are provided between the polarizing member and the objective lens, a half mirror that transmits the second laser beam and the third laser beam reflected from the second detector in the direction of the second photodetector. A half-wavelength-compatible quarter-wave plate that converts the polarization direction of the light and the third laser light from linearly polarized light to circularly polarized light, and from circularly polarized light to linearly polarized light. The second laser beam and the third laser beam reflected by the laser beam are reflected by the AS plate to be incident on the polarizing member, and the first laser beam, the second laser beam, and the third laser beam are incident on the polarizing member. An optical pickup device characterized in that the optical paths are synthesized. 2. The optical pickup device according to claim 1, wherein a polarizing beam splitter is used as the polarizing member. A first objective lens for condensing the first laser beam on the signal recording layer of the first optical disc and a second laser beam on the signal recording layer of the second optical disc and the third laser beam on the signal recording layer of the third optical disc The optical pickup device according to claim 1, further comprising a second objective lens that collects light on the second objective lens. The first laser beam is focused on the signal recording layer of the first optical disc, the second laser beam is focused on the signal recording layer of the second optical disc, and the third laser beam is focused on the signal recording layer of the third optical disc. The optical pickup device according to claim 1, wherein the objective lens to be operated is constituted by a single objective lens compatible with three wavelengths.

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