JP2008084449A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device wherein respective laser beams can be smoothly received by a common photodetector while the laser beams having wavelengths different from each other are made incident in a common objective lens in different conjugated states. <P>SOLUTION: A laser beam for HD and a laser beam for DVD emitted from semiconductor lasers 101 and 102 converted into parallel beams (an infinite conjugated system) by a collimator lens 106 and made incident in the objective lens 111 and a laser beam for CD emitted from a semiconductor laser 103 is made incident in the objective lens 111 in a diffusion state (a finite conjugated system). When the CD is reproduced, a liquid crystal lens 109 is driven and the laser beam for the CD reflected from the CD is converted into a parallel beam by the liquid crystal lens 109. Thereby, the reflected beam is made incident in the collimator lens 106 in a parallel beam state as well as the reflected beams of the laser beam for HD and the laser beam for DVD and these beams can be received by the common photodetector 115. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical pickup device, and is particularly suitable for use in a compatible optical pickup device that converges laser beams having different wavelengths on a disk using a common objective lens.

  Currently, CDs (Compact Discs) and DVDs (Digital Versatile Discs) are commercialized and widely used as optical disks. More recently, commercialization of HD DVD (High-Definition Digital Versatile Disc) has been promoted as a larger capacity optical disc. Among these optical discs, DVD and HDDVD have the same light transmission protective layer (cover layer) thickness, but CD has a light transmission protective layer thicker than other discs. For this reason, when the laser light is converged on the CD and another disk by the common objective lens, it is necessary to change the conjugate state of the laser light with respect to the objective lens according to the difference in the thickness of the light transmission protective layer.

As a method for realizing this, for example, a method described in Patent Document 1 below is known. In this document, the laser beam for DVD and the laser beam for HDDVD are incident on the objective lens after being converted into parallel light by the collimator lens, and the laser beam for CD is incident on the objective lens as diffused light without passing through the collimator lens. The configuration is shown. In this case, the DVD laser light and the HDDVD laser light are incident on the objective lens in an infinite conjugate system, and the CD laser light is incident on the objective lens in a finite conjugate system. Thereby, the focal position of the laser beam by the objective lens changes back and forth, and the laser beam of each wavelength can be smoothly converged on the corresponding disk.
JP 2006-12218 A

  However, in this case, of the laser light reflected by the disc, the DVD laser light and the HDDVD laser light become parallel light after passing through the objective lens, and the CD laser light converges after passing through the objective lens. Since it becomes light, the focal lengths of the two are different, and therefore there arises a problem that the respective laser beams cannot be received by a common photodetector. In this case, for example, only a CD laser beam having a different focal length can be separated from other laser beams and received by an independent photodetector, but the optical system is complicated and large in size. This also results in an increase in the number of parts and cost.

  Therefore, the present invention provides an optical pickup device that allows laser beams of different wavelengths to be incident on a common objective lens in different conjugate states while each laser beam can be smoothly received by a common photodetector. This is the issue.

  In view of the above problems, the present invention has the following features.

  According to a first aspect of the present invention, in the optical pickup device, a first semiconductor laser that emits a laser beam having a first wavelength and a second semiconductor that emits a laser beam having a second wavelength different from the first wavelength A laser, an objective lens for converging the laser beams of the first and second wavelengths on the disk, and a first optical for guiding the laser beams of the first and second wavelengths to the objective lens with different conjugates. A system, a photodetector for receiving reflected light from the disk, a second optical system for guiding the laser beams of the first and second wavelengths reflected by the disk to the photodetector, and the first And an optical element that is arranged in the optical path of the second optical system and that matches the focal lengths of the laser beams of the first and second wavelengths reflected by the disk.

  According to a second aspect of the present invention, in the optical pickup device, a first semiconductor laser that emits a laser beam having a first wavelength and a second semiconductor that emits a laser beam having a second wavelength different from the first wavelength A laser, an objective lens for converging the laser beams of the first and second wavelengths on the disk, and a first optical for guiding the laser beams of the first and second wavelengths to the objective lens with different conjugates. A system, a photodetector for receiving reflected light from the disk, a second optical system for guiding the laser beams of the first and second wavelengths reflected by the disk to the photodetector, and the first A polarization beam splitter that separates the optical path of the second optical system in a direction from the optical path of the first optical system toward the photodetector, and in the common optical path of the first and second optical systems, and the first and second optical systems. Second wavelength laser Is disposed between the polarizing plate and the ¼ wavelength plate, and is dynamically driven by a driving signal so that reflected light from the disk is incident. And a liquid crystal lens that applies a lens action to the light in the polarization direction and matches the focal lengths of the laser beams having the first and second wavelengths toward the photodetector.

  According to a third aspect of the present invention, there is provided the optical pickup device according to the second aspect, wherein the collimating lens is disposed at a position where only one of the laser beams having the first and second wavelengths is incident in the first common optical path. And only one of the laser beams of the first and second wavelengths is converted into parallel light by the collimating lens, so that the laser beams of the first and second wavelengths are conjugated differently. And guided to the objective lens.

  According to a fourth aspect of the present invention, in the optical pickup device according to the second or third aspect, the quarter-wave plate and the liquid crystal lens are integrally formed as a single structure.

  According to a fifth aspect of the present invention, in the optical pickup device according to the fourth aspect, in addition to the quarter-wave plate and the liquid crystal lens, an aberration correction element that suppresses the aberration of laser light on the disk is integrated. It is formed into a single structure.

  According to a sixth aspect of the present invention, in the optical pickup device according to the fourth or fifth aspect, any of the laser beams having the first and second wavelengths is formed on the laser beam passage surface of the integrally formed structure. A wavelength selective film that imparts an aperture limiting action to only one of them is formed.

  According to the first and second aspects of the present invention, the first and second wavelength laser beams are incident on the objective lens in different conjugate states by the first optical system. The focal position can be moved back and forth in the optical axis direction. In addition, since the focal lengths of the laser beams having the first and second wavelengths traveling toward the photodetector coincide with each other due to the action of the optical element or the liquid crystal lens, the two laser beams are separated by a common photodetector. It can receive light.

  According to the invention of claim 3, either one of the first and second wavelength laser beams is incident on the objective lens through the infinite conjugate system, and the other is incident on the objective lens through the finite conjugate system. Can do.

  According to the invention of claim 4, since the quarter wavelength plate and the liquid crystal lens are integrally formed as one structure, the number of parts can be suppressed, and the quarter wavelength plate and the liquid crystal are reduced. Workability at the time of arranging the lens can be improved.

  Further, according to the invention of claim 5, since the aberration correction element is further integrated with this structure, the number of parts can be further reduced and the arrangement work can be simplified.

  According to the invention of claim 6, since the opening limiting film is further formed in the structure, it is not necessary to separately arrange an opening limiting element, and the position adjustment of the opening limiting element needs to be individually performed. Therefore, it is possible to reduce the number of parts and simplify the position adjusting operation of the aperture limiting element.

The characteristics and significance of the present invention will be further clarified by the following description of embodiments. However, the following embodiments are merely exemplary forms for carrying out the present invention, and the meanings of the terms of the present invention or each constituent element are limited to those described in the following embodiments. Is not to be done.

  Embodiments of the present invention will be described below with reference to the drawings. This embodiment is compatible with HDDVD (hereinafter referred to as “HD”) and DVD with a light transmission protective layer (cover layer) thickness of 0.6 mm, and a CD with a light transmission protective layer thickness of 1.2 mm. The present invention is applied to a compatible optical pickup device that can be used.

  FIG. 1 is a diagram illustrating an optical system of an optical pickup device according to an embodiment and a circuit configuration on the optical disk device side related thereto.

  As shown in the figure, the optical system of the optical pickup device includes semiconductor lasers 101, 102, 103, a dichroic prism 104, a polarizing beam splitter 105, a collimating lens 106, a lens actuator 107, a dichroic mirror 108, and a liquid crystal lens 109. A quarter-wave plate 110, an objective lens 111, a holder 112, an objective lens actuator 113, a detection lens 114, and a photodetector 115. The optical disc apparatus also includes a signal calculation circuit 201, a reproduction circuit 202, a servo circuit 203, and a controller 204.

  The semiconductor laser 101 emits laser light having a wavelength of about 405 nm (hereinafter referred to as “HD laser light”). The semiconductor laser 102 emits laser light having a wavelength of about 650 nm (hereinafter referred to as “DVD laser light”). The semiconductor laser 103 emits laser light having a wavelength of about 780 nm (hereinafter referred to as “CD laser light”). The dichroic prism 104 transmits the HD laser beam and reflects the DVD laser beam. The semiconductor lasers 101 and 102 are arranged so that the optical axes of the HD laser light and the DVD laser light after passing through the dichroic prism 104 coincide. Further, these laser beams are arranged so that the polarization direction thereof is P-polarized with respect to the polarization beam splitter 105.

  The polarization beam splitter 105 substantially totally transmits the laser light (P-polarized light) incident from the dichroic prism 104 side and substantially totally reflects the laser light (S-polarized light) incident from the collimator lens 106 side. The collimating lens 106 converts the laser light incident from the polarization beam splitter 102 side into parallel light. The collimating lens 106 is designed to have an aberration correction function. The lens actuator 107 displaces the collimating lens 106 in the optical axis direction according to the servo signal input from the servo circuit 203. Thereby, the aberration which arises in a laser beam is correct | amended.

  The dichroic mirror 108 reflects the laser light incident from the collimating lens 106 side in the direction toward the objective lens 111 and transmits the CD laser light emitted from the semiconductor laser 103. The semiconductor laser 103 is disposed so that the optical axes of the CD laser light after passing through the dichroic mirror 108 coincide with the optical axes of the HD laser light and the DVD laser light. Also, the polarization direction of the CD laser light is arranged to be P-polarized in the same way as the HD laser light and the DVD laser light. The laser beam for CD emitted from the semiconductor laser 103 enters the objective lens 111 in a diffusion state (finite conjugate system) corresponding to the thickness of the light transmission protective layer of the CD.

  The liquid crystal lens 109 imparts a diffusing action to S-polarized laser light. The configuration of the liquid crystal lens 109 will be described later with reference to FIGS.

  The quarter-wave plate 110 converts laser light traveling toward the disk into circularly polarized light, and converts reflected light from the disk into linearly polarized light (S-polarized light) perpendicular to the polarization direction (P-polarized light) when the disk is incident. . In the present embodiment, the liquid crystal lens 109 and the quarter wavelength plate 110 are integrally formed. Further, on the surface of the quarter-wave plate 110, a wavelength-selective aperture limiting film 110a (see FIG. 3B) that provides an aperture limiting function only to the CD laser beam is formed.

  The objective lens 111 is designed to properly converge the HD laser beam and the DVD laser beam onto the HD recording surface and the DVD recording surface. When HD and DVD are supported, the HD laser beam and the DVD laser beam are incident on the objective lens 111 in an infinite conjugate system (parallel light). On the other hand, at the time of CD correspondence, the laser beam for CD is limited by the aperture limiting film 110a formed on the surface of the quarter wavelength plate 110, and is incident on the objective lens 111 in a finite conjugate system (diffused light). The As a result, the convergence position of the CD laser light when CD is supported is farther from the objective lens 111 than when HD and DVD are supported. Here, the conjugate action of the aperture limiting action imparted to the laser beam at the time of CD support and the CD laser beam is adjusted so that the CD laser beam is properly converged on the CD recording surface.

  The holder 112 integrally holds the liquid crystal lens 109, the quarter wavelength plate 110, and the objective lens 111. The objective lens actuator 113 is configured by a conventionally known electromagnetic drive circuit, and a coil portion such as a focus coil is mounted on the holder 112 in the circuit.

  The detection lens 114 converges the HD laser light, the DVD laser light, and the CD laser light reflected by each disk on the photodetector 115. Here, the detection lens 114 is constituted by a cylindrical lens, and introduces astigmatism into the reflected light from the disk. The photodetector 115 has a sensor pattern for deriving a reproduction RF signal, a focus error signal, and a tracking error signal from the intensity distribution of the received laser beam. A signal from each sensor is output to the signal calculation circuit 201. Note that the position of the light receiving surface of the photodetector 115 is adjusted so as to receive the reflected light from the disk incident on the collimating lens 103 as parallel light.

  The signal arithmetic circuit 201 performs arithmetic processing on the sensor signal incident from the photodetector 115 to generate a reproduction RF signal, a focus error signal, and a tracking error signal, and outputs them to a corresponding circuit.

  The reproduction circuit 202 demodulates the reproduction RF signal input from the signal arithmetic circuit 201 to generate reproduction data. The servo circuit 203 generates a tracking servo signal and a focus servo signal from the tracking error signal and the focus error signal input from the signal arithmetic circuit 201, and outputs them to the objective lens actuator 113. In addition, a drive signal is output to the liquid crystal lens 109 in response to a command from the controller 204. The controller 204 outputs a command signal for driving the liquid crystal lens 109 to the servo circuit 203 when the reproduction target disc is a CD.

  FIG. 2 shows a cross-sectional structure of the liquid crystal lens 109. Since the liquid crystal lens 109 is formed integrally with the quarter-wave plate 110 as described above, the portion of the quarter-wave plate 110 is also shown in FIG. Further, this figure shows a cross-sectional structure when the structure including the liquid crystal lens 109 and the quarter-wave plate 110 in FIG. 1 is cut along a plane parallel to the YZ plane.

  The liquid crystal lens 109 is configured by enclosing a liquid crystal with a seal member 109e between a transparent electrode 109b having a blazed diffraction structure 109c on the upper surface and a transparent electrode 109f facing the transparent electrode 109b. Here, the alignment direction of the liquid crystal molecules in the liquid crystal layer 109d is aligned with the inner surface of the transparent electrode 109f, the upper surface of the diffraction structure 109c, and the inner surface of the transparent electrode 109b where the diffraction structure 109c is not formed. An alignment film (not shown) is formed. The two transparent electrodes 109b and 109f are formed on the inner side surfaces of the glass substrates 109a and 109g, respectively. Further, an opening limiting film 110 a is formed on the upper surface of the quarter wavelength plate 110.

  The diffraction structure 109c is formed in a concentric ring shape as shown in FIG. Further, as shown in FIG. 3B, the aperture limiting film 110a has a circular light transmission region (a region where no aperture limiting film is formed) formed at the center. This figure schematically shows the state when the diffraction structure 109c and the aperture limiting film 110a are viewed from the Y-axis direction of FIG.

  The diffractive structure 109c exhibits a function as a diffraction grating when laser light is incident as S-polarized light. The diffractive structure 109c imparts a lens action for converting the CD laser light (converged light) reflected by the CD into parallel light to the CD laser light. Further, the center of the region where the diffraction structure 109c is formed coincides with the center of the light transmission region of the aperture limiting film 110a shown in FIG. 5B, and the diameter D1 is equal to that of the light transmission region of the aperture limiting film 110a. It is substantially the same as the diameter D2.

  Since the liquid crystal lens 109 is adjusted so as to give a lens effect to the laser light when the laser light is incident in the S-polarized state, the HD laser light, the DVD laser light, and the CD laser light are objective. Even if it passes through the liquid crystal lens 109 in the forward path toward the lens 111, no lens action is imparted to these laser beams (P-polarized light). Therefore, the HD laser light and the DVD laser light pass through the liquid crystal lens 109 as parallel light, and the CD laser light passes through the liquid crystal lens 109 as diffuse light.

  On the other hand, since the polarization direction of the HD laser beam, DVD laser beam, and CD laser beam after being reflected by the disk and passing through the quarter-wave plate 110 is S-polarized, the liquid crystal lens 109 After passing, the lens action is received as follows according to the driving state of the liquid crystal lens 109.

  The refractive index of the liquid crystal layer 109d when the laser light incident on the liquid crystal lens 109 is S-polarized light is the same as the refractive index of the diffractive structure 109c when no voltage is applied between the transparent electrodes 109b and 109f. In this case, since a boundary due to the refractive index does not occur between the liquid crystal layer 109d and the diffractive structure 109c, the diffractive structure 109c does not function as a diffraction grating, and a lens effect on the laser light does not occur.

  On the other hand, when a voltage is applied to the transparent electrodes 109b and 109f, the alignment state of the liquid crystal molecules in the liquid crystal layer 109d changes, and as a result, the refractive index of the liquid crystal layer 109d with respect to S-polarized light changes. Thereby, a boundary due to the refractive index is generated between the liquid crystal layer 109d and the diffractive structure 109c, and the diffractive structure 109c functions as a diffraction grating. As a result, the laser light is subjected to the lens effect by the diffractive structure 109c.

  Here, the diffraction structure 107b is configured such that the diffraction efficiency of the + 1st order light is approximately 100%. FIG. 4 shows a simulation of the phase difference and diffraction efficiency generated at the blaze height for a CD laser beam having a wavelength of 780 nm. In this case, the diffraction efficiency of the + 1st order light with respect to the laser beam for CD can be set to 100% by adjusting the height of the blaze so that the resulting phase difference is 780 nm. In this case, the laser beam for CD reflected by the CD and incident on the liquid crystal lens 109 is subjected to the diffusing action by the diffractive structure 109c without being attenuated in terms of diffraction efficiency by setting the liquid crystal lens 109 to the driving state. It will be.

  In the present embodiment, when the playback target disks are HD and DVD, the liquid crystal lens 109 is set to a non-driven state. Therefore, the HD laser light and DVD laser light reflected by the HD and DVD pass through the liquid crystal lens 109 as parallel light without being subjected to the lens action by the liquid crystal lens 109.

  On the other hand, when the reproduction target disc is a CD, the liquid crystal lens 109 is set in a driving state. Therefore, the CD laser light reflected by the CD is subjected to the lens action by the liquid crystal lens 109, passes through the liquid crystal lens 109, and is converted into parallel light.

  In this way, by switching and controlling the driving state of the liquid crystal lens 109, the reflected light of the CD laser light is parallel to the photodetector 115 in the same state as the reflected light of the HD laser light and the DVD laser light. To be able to go to. Therefore, by adjusting the light receiving surface of the photodetector 115 as described above to a position where the reflected light from the disk incident on the collimating lens 103 can be received as parallel light, the HD laser light and the DVD laser light can be received. CD laser light can be received by a common photodetector. In addition, it is not necessary to adjust the detection lens 114 separately to take into account the conjugation of the laser beam for CD.

  Although the embodiments of the present invention have been described above, various modifications can be made to the embodiments of the present invention in addition to the above.

  For example, in the above embodiment, the aberration of the laser beam on the disk is corrected using a collimating lens with an aberration correction function. However, as shown in FIG. 5 and FIG. Correction can also be performed. In the example shown in FIGS. 5 and 6, the phase correction element 121 is formed integrally with the liquid crystal lens 109 and the quarter wavelength plate 110.

  FIG. 6 is a diagram illustrating the configuration of the phase correction element 121. This figure shows a cross-sectional structure when the structure including the liquid crystal lens 109, the quarter-wave plate 110, and the phase correction element 121 in FIG. 5 is cut along a plane parallel to the YZ plane. As illustrated, the phase correction element 121 includes a transparent electrode 121a, a liquid crystal layer 121b, a seal member 121c, a transparent electrode 121d, and a glass substrate 121e.

  The transparent electrodes 121a and 121d are formed on the glass substrates 109a and 121e, respectively. Among these, as shown in FIG. 7, the transparent electrode 121a is formed by forming a plurality of ring-shaped electrodes having different diameters on a concentric circle. The transparent electrode 121d is a circular electrode having the same diameter as that of the largest diameter ring-shaped electrode among the ring-shaped electrodes on the transparent electrode 121a. The central axis of the ring-shaped electrode on the transparent electrode 121a side and the central axis of the circular electrode on the transparent electrode 121d side coincide with each other.

  An alignment film (not shown) is formed on the surface of the transparent electrodes 121a and 121d on the liquid crystal layer 121b side. A liquid crystal layer 121b is formed by filling liquid crystal between the alignment film and the seal member 121c. The liquid crystal layer 121b changes the alignment direction of liquid crystal molecules when a potential is applied through the transparent electrodes 121a and 121d.

  When different potentials are applied to the ring-shaped electrodes on the transparent electrode 121a side while keeping the transparent electrode 121d at a constant potential V0 (for example, ground potential), the orientation direction of liquid crystal molecules between the ring-shaped electrode and the transparent electrode 121d is applied potential. It changes according to. As a result, the refractive index of the liquid crystal layer 121b changes at the position of the ring-shaped electrode, and a phase change occurs in the laser light passing through each position. As a result, the wavefront state of the laser light after passing through the liquid crystal layer 121b changes according to the phase change state. For example, as shown in FIG. 7, the wavefront state of the laser light after passing through the liquid crystal layer 121b is changed in the radial direction by changing the potential applied to each ring-shaped electrode in steps from V0 to V1. It can be changed in the same step shape. Therefore, by controlling the potential applied to the ring electrode, the wavefront state of the laser beam can be adjusted, and thereby the aberration of the laser beam on the disk can be suppressed.

  In the above embodiment, the diffractive structure formed on the liquid crystal lens 109 is a blaze type, but as shown in FIG. 8, the diffractive structure formed on the liquid crystal lens 109 may be a step type diffractive structure. In the figure, a diffractive structure 109c is constituted by a four-step diffractive structure.

  FIG. 9 shows a simulation of the relationship between the phase difference per step generated in the laser beam for CD and the diffraction efficiency when the diffraction structure 109c is a four-step diffraction structure. In this case, by setting the phase difference per step generated in the laser beam for CD (wavelength λ: 780 nm) to 0.25λ, the diffraction efficiency for the laser beam for CD can be set to about 0.8. Attenuation of laser light due to efficiency can be suppressed. However, since this diffraction efficiency is about 0.2 lower than that in the case of FIG. 4, in terms of diffraction efficiency, it is advantageous to make the diffraction structure 109c blazed as shown in FIG.

  In the above embodiment, the liquid crystal lens 109 is formed integrally with the quarter wavelength plate 110 and attached to the holder 112. However, the liquid crystal lens 109 is separated from the quarter wavelength plate 110. For example, it may be arranged at any position in the optical path between the quarter-wave plate 110 and the photodetector 115, such as the position of A or B in FIG. However, when the lens is disposed at the position A or B in FIG. 10, the objective lens 111 is displaced in the tracking direction, thereby causing a deviation between the central axis of the objective lens 111 and the central axis of the liquid crystal lens 109. Therefore, there arises a problem that the characteristics of the laser beam for CD (reflected light) are deteriorated as compared with the above embodiment. Further, as the position of the liquid crystal lens 109 is further away from the objective lens 111, the beam diameter of the laser beam for CD (reflected light) when entering the liquid crystal lens 109 becomes smaller. In addition, the optical axis adjustment of the diffractive structure with respect to the laser light is required to have high accuracy. For this reason, the liquid crystal lens 109 is preferably attached to the holder 112 that holds the objective lens 111 as described above.

  Furthermore, in the above embodiment, the collimating lens function has been described for the case where HD laser light is converted into parallel light. However, the present invention is not limited to this. May be. In this case, although the incident light to the objective lens 111 becomes finite conjugate, it becomes gentler than the diffusion degree of the CD laser light, so that the HD laser light and the CD laser light have different finite conjugate objectives. The light enters the lens 111. Further, regarding the function of the liquid crystal lens 109 in this case, the laser beam for HD which does not receive the lens action as a result of imparting a diffusing action to the laser beam for CD after being reflected by the disk and transmitted through the quarter-wave plate 110. It is sufficient to set the focus at the same position.

  In addition, the present invention is compatible with HD, DVD, CD compatible pickup devices, HD, CD compatible pickup devices, or several types of discs having different thicknesses of light transmission protective layers (cover layers). The present invention can also be applied to a compatible optical pickup device.

  The embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

The figure which shows the structure of the optical pick-up apparatus and peripheral circuit which concern on embodiment FIG. 6 illustrates a structure of a liquid crystal lens according to an embodiment. The figure explaining the diffraction structure and aperture limiting film of the liquid crystal lens which concern on embodiment The figure explaining the diffraction efficiency of the liquid crystal lens which concerns on embodiment The figure which shows the example of a change of the optical pick-up apparatus and peripheral circuit which concerns on embodiment The figure explaining the liquid crystal lens and phase correction element which concern on embodiment The figure which shows the electrode pattern and applied electric potential of the phase correction element which concern on embodiment The figure explaining the example of a change of the liquid crystal lens which concerns on embodiment The figure explaining the diffraction efficiency of the liquid crystal lens which concerns on embodiment The figure which shows the example of a change of the arrangement position of the liquid crystal lens which concerns on embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 101,102,103 ... Semiconductor laser 104 ... Dichroic prism 105 ... Polarizing beam splitter 106 ... Collimating lens 108 ... Dichroic mirror 109 ... Liquid crystal lens 110 ... 1/4 wavelength plate 111 ... Objective lens 114 ... Detection lens 115 ... Photodetector

Claims (6)

A first semiconductor laser that emits laser light of a first wavelength;
A second semiconductor laser that emits laser light having a second wavelength different from the first wavelength;
An objective lens for focusing the laser beams of the first and second wavelengths on the disk;
A first optical system for guiding the laser beams of the first and second wavelengths to the objective lens with different conjugates;
A photodetector for receiving reflected light from the disk;
A second optical system for guiding the laser beams of the first and second wavelengths reflected by the disk to the photodetector;
An optical element that is arranged in the optical path of the second optical system and matches the focal lengths of the laser beams of the first and second wavelengths reflected by the disk;
An optical pickup device comprising: A first semiconductor laser that emits laser light of a first wavelength;
A second semiconductor laser that emits laser light having a second wavelength different from the first wavelength;
An objective lens for focusing the laser beams of the first and second wavelengths on the disk;
A first optical system for guiding the laser beams of the first and second wavelengths to the objective lens with different conjugates;
A photodetector for receiving reflected light from the disk;
A second optical system for guiding the laser beams of the first and second wavelengths reflected by the disk to the photodetector;
A polarization beam splitter that separates the optical path of the second optical system in a direction from the optical path of the first optical system toward the photodetector;
A quarter-wave plate disposed in a common optical path of the first and second optical systems and at a position where both the laser beams of the first and second wavelengths are incident;
The light beam is disposed between the polarizing beam splitter and the quarter-wave plate and is dynamically driven by a driving signal to add a lens action to the light in the polarization direction when the reflected light from the disk is incident. A liquid crystal lens for matching the focal lengths of the laser beams of the first and second wavelengths toward the detector;
An optical pickup device comprising: The optical pickup device according to claim 2,
A collimating lens is disposed in the first common optical path at a position where only one of the laser beams having the first and second wavelengths is incident, and the lasers having the first and second wavelengths are arranged by the collimating lens. By converting only one of the lights into parallel light, the laser beams of the first and second wavelengths are guided to the objective lens with different conjugates.
An optical pickup device characterized by that. The optical pickup device according to claim 2 or 3,
The quarter-wave plate and the liquid crystal lens are integrally formed into a single structure.
An optical pickup device characterized by that. The optical pickup device according to claim 4,
In addition to the quarter-wave plate and the liquid crystal lens, an aberration correction element that suppresses the aberration of laser light on the disk is integrally formed to form a single structure.
An optical pickup device characterized by that. The optical pickup device according to claim 4 or 5,
On the laser beam passage surface of the integrally formed structure, a wavelength selection film is provided that imparts an aperture limiting action to only one of the laser beams of the first and second wavelengths.
An optical pickup device characterized by that.

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