JP2011028817A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device in which a position of a lens used for correction of spherical aberration can be detected in real time without complexing and enlarging device configuration, and without increasing the number of assembling processes of a device. <P>SOLUTION: A light quantity monitor 19 that receives both light beams of a light source 2 for BD and a light source 9 for DVD, CD is arranged at a holder 17 mounting a collimator lens 4 and moved. When the light source 9 constantly emits light with the prescribed light quantity, a position detection unit 23 detects a position in the optical axis direction of the collimator lens 4 based on the light quantity of light from the light source 9 detected by the light quantity monitor 19. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical pickup device used for recording and reproducing information signals on an optical disc.

  2. Description of the Related Art Conventionally, an optical pickup device used for recording and reproducing information signals with respect to a BD (Blu-ray Disc) is provided with a mechanism for correcting spherical aberration caused by a difference in cover layer thickness in the BD. ing.

  This is because the NA (numerical aperture) of the objective lens used in the optical pickup device for BD is 0.85, and the NA of the objective lens for CD (Compact Disc) and DVD (Digital Versatile Disk) (0. 45 to 0.51 and DVD for 0.6 to 0.65), which is larger than the spherical aberration caused by an error in the thickness of the cover layer, and this needs to be corrected. is there. In addition, in the BD, a two-layer disc is in the standard, and it is essential to correct spherical aberration corresponding to the thickness of the cover layer of each recording layer.

  As a method of correcting spherical aberration, a lens (for example, a collimator lens) between the light source and the objective lens is moved in the optical axis direction, thereby changing the divergence angle of the light beam incident on the objective lens and changing the magnification. For this reason, a correction method using spherical aberration generated in the objective lens is used. In order to move the lens, generally, the lens is attached to a holder that can move in the optical axis direction, and the holder is moved by a drive mechanism such as a stepping motor.

  As described above, when the position of the lens is moved in accordance with the thickness of the cover layer of the optical disk, the position of the lens must be controlled corresponding to the optical disk to be recorded and reproduced. For this purpose, it is necessary to detect the position of the lens. In the case of using a stepping motor as a drive source for moving the holder on which the lens is mounted, the position of the lens in the optical axis direction is controlled by moving the lens to the initial position and then counting the number of pulses sent to the stepping motor. Yes. In this method, since the current lens position is acquired as a relative amount converted from the number of pulses of driving the stepping motor from the origin position, it is necessary to first send the lens to the origin position.

  In order to eliminate such an operation, a technique for detecting the position of the lens in real time has been proposed.

  For example, in Patent Document 1, a part of a light beam that has passed through a beam expander is separated and incident on a detector for controlling the beam expander, and the position of the lens is changed by utilizing the change in the amount of incident light. Control techniques have been proposed.

  Patent Document 2 proposes a technique in which a detector that detects the parallelism of light that has passed through a collimator lens is disposed, and the position of the collimator lens is detected from a deviation in parallelism.

  Further, as a method that does not require a dedicated optical path for detecting the position of the lens, in Patent Document 3, a part of light directed from the light source toward the optical disk is reflected, and in the vicinity of the detector that receives the reflected light from the optical disk. A technique has been proposed in which the light is condensed and the change in the light condensing state due to the movement of the lens is detected.

JP 2005-327396 A JP 2007-149228 A JP 2008-305493 A

  In the techniques of the above Patent Documents 1 and 2, it is necessary to provide a dedicated detector for detecting the position of the lens, and the arrangement of the optical system is limited in order to arrange the optical path for the dedicated detector. As a result, the device configuration has become complicated and large.

  In the technique of Patent Document 3, a detector for detecting the position of the lens is provided in the same package as the detector for detecting information on the optical disk, so that an optical path for detection is not required separately, so that the optical system can be made compact. However, in order to make light incident on the detector for detecting the position of the lens, it is necessary to adjust the inclination of the optical element with high accuracy, and the number of assembling steps has increased.

  The present invention has been made in view of the above, and can detect in real time the position of a lens used for correcting spherical aberration without increasing the complexity and size of the apparatus and increasing the number of steps for assembling the apparatus. An object is to provide an optical pickup device.

  In order to achieve the above object, an optical pickup device of the present invention includes a first light source that emits light having a predetermined wavelength, a second light source that emits light having a wavelength different from that of the first light source, and the first light source. An objective lens that causes light emitted from one light source to enter the optical disk, and a divergence that is provided between the first light source and the objective lens and changes a divergence angle of the light emitted from the first light source. An angle conversion element; a moving means for moving a holder holding the divergence angle conversion element in an optical axis direction; and the holder provided at a position where light emitted from the first and second light sources can enter. A first light amount monitor for detecting light emitted from the first and second light sources, a second light amount monitor for detecting light emitted from the second light source, and the first and second light sources, respectively. Detected by 2 light intensity monitor Light source control means for controlling the emitted light quantity of the first and second light sources based on the light quantity of the light source, and the second light source emits light, and is detected by the second light quantity monitor by the light source control means. When the amount of light emitted from the second light source is controlled to a predetermined amount based on the amount of light, based on the amount of light from the second light source detected by the first light amount monitor, And a position detecting means for detecting the position of the divergence angle conversion element in the optical axis direction.

  In the optical pickup device of the present invention, the first light amount monitor has a direction in which a spread angle of light from the first light source is maximum with respect to the first light source and the second light source. The divergence angle of the light from the second light source is arranged between the maximum direction and the minimum direction.

  According to the optical pickup device of the present invention, it is possible to detect the position of the lens used for correcting the spherical aberration in real time without increasing the complexity and size of the device and increasing the number of steps for assembling the device.

1 is a schematic configuration diagram of an optical pickup device according to an embodiment of the present invention. It is a figure for demonstrating arrangement | positioning of the light quantity monitor installed in the holder of the optical pick-up apparatus shown in FIG. It is a figure which shows intensity distribution of the light inject | emitted from a light source. It is a figure which shows the change of the light reception amount of the light quantity monitor when a collimator lens moves. It is a figure which shows the change rate of the light reception amount of a light quantity monitor when a collimator lens moves. It is a figure which shows the change of the emitted light amount of an objective lens when a collimator lens moves. It is a schematic block diagram of the optical pick-up apparatus which concerns on the modification of embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals, and the description thereof is omitted or simplified.

  FIG. 1 is a schematic configuration diagram of an optical pickup device according to an embodiment of the present invention. The optical pickup device 1 according to the present embodiment corresponds to three standards of BD, DVD, and CD.

  As shown in FIG. 1, the optical pickup device 1 includes a light source 2 composed of a semiconductor laser that emits laser light having a wavelength of 400 to 410 nm corresponding to BD, and condenses light from the light source 2 on a recording layer of an optical disc 30. An objective lens 3, a collimator lens 4 that is provided between the light source 2 and the objective lens 3 and changes a divergence angle of light from the light source 2, and the objective lens 3 and the collimator lens 4. A quarter-wave plate 5 provided between the light source 2 and the collimator lens 4 for converting the polarization of light from the light source 2 from linearly polarized light to circularly polarized light; A polarization beam splitter 6 that branches the optical path (return path) of the reflected light from the light source 2 from the optical path (outward path) of the light emitted from the light source 2, and an optical detector that detects the reflected light branched by the polarization beam splitter 6. It comprises a vessel 7, is provided between the polarizing beam splitter 6 and the light detector 7, a detection lens 8 to be incident reflected light split by the polarizing beam splitter 6 to the photodetector 7.

  The optical pickup device 1 also collects the light from the light source 9 that emits laser light having a wavelength of 650 to 665 nm corresponding to DVD and the laser light having a wavelength of 780 nm corresponding to CD, and the light from the light source 9 on the recording layer of the optical disc 30. A collimator lens 11 provided between the objective lens 10 that illuminates, the light source 9 and the objective lens 10 to change the divergence angle of the light from the light source 9, and provided between the objective lens 10 and the collimator lens 11; A quarter-wave plate 12 for converting the polarization of light from the light source 9 from linearly polarized light to circularly polarized light, and the light source 9 and the collimator lens 11 are provided, and a part of the light emitted from the light source 9 is separated. At the same time, the polarization beam splitter 13 branches the optical path (return path) of the reflected light from the light source 9 reflected by the optical disc 30 from the optical path (outward path) of the light emitted from the light source 9. , A photodetector 14 for detecting the reflected light branched by the polarizing beam splitter 13, and a photodetector provided between the polarizing beam splitter 13 and the photodetector 14 for detecting the reflected light branched by the polarizing beam splitter 13. 14 includes a detection lens 15 that is incident on the light source 14 and a light amount monitor 16 that detects light in the forward path from the light source 9 partially separated by the polarization beam splitter 13.

  The light source 9 is a so-called two-wavelength laser in which a semiconductor laser that emits laser light having a wavelength of 650 to 665 nm corresponding to DVD and a semiconductor laser that emits laser light having a wavelength of 780 nm corresponding to CD are mounted in the same package. . The objective lens 10 is a lens compatible with both DVD and CD. Further, the photodetector 14 has a region for receiving reflected light of both DVD and CD, and other optical components are designed to be shared by two wavelengths corresponding to DVD and CD. A common optical path is used for CD recording and reproduction.

  The collimator lens 4 for BD is fixed to a holder 17 that can move in the optical axis direction of the light emitted from the light source 2, and the thickness of the cover layer of the optical disc 30 is changed by changing the position in the optical axis direction. Corrects spherical aberration that sometimes occurs. The holder 17 is connected to a rotating shaft 18a of a stepping motor 18 that is a moving means, and can move in the optical axis direction.

  A light amount monitor 19 is provided on the side of the holder 17 facing the light sources 2 and 9. The light amount monitor 19 is disposed in the holder 17 at a position where both the light emitted from the light source 2 and the light source 9 can enter, and detects the light from the light sources 2 and 9, respectively.

  In addition, the optical pickup device 1 includes a light amount detection unit 20 that detects the light amount of light detected by the light amount monitor 19, a light amount detection unit 21 that detects the light amount of light detected by the light amount monitor 16, and a light amount detection unit 20. , 21 based on the light quantity detected by the light sources 2 and 9, the APC (Auto Power Control) drive unit 22 that controls the light quantity emitted from the light sources 2 and 9, and the light quantity of the light source 9 detected by the light quantity detection unit 20. A position detector 23 that detects the position of the collimator lens 4 in the optical axis direction, a motor drive unit 24 that drives the stepping motor 18, and a controller 25 that controls each unit provided in the apparatus.

  FIG. 2 is a view for explaining the arrangement of the light quantity monitor 19 and is a view of the holder 17 as viewed from the light sources 2 and 9 side. As shown in FIG. 2A, the holder 17 is equipped with a collimator lens 4 for BD, and has an effective diameter of the collimator lens 11 for DVD and CD so as not to block the optical path for DVD and CD. Correspondingly, a through hole 26 having a required size is provided. The light quantity monitor 19 detects light that strikes a portion outside the effective diameter of the collimator lenses 4 and 11.

  By the way, the light emitted from the semiconductor lasers used as the light sources 2 and 9 is diffused light whose intensity exhibits a Gaussian distribution as shown in FIG. 3, and is horizontal (H direction) with respect to the bonding surface of the semiconductor laser. And the vertical direction (V direction) have different spread angles. Many semiconductor lasers used as a light source in an optical pickup device have an aspect ratio of about 2.

  The direction of the light amount distribution of the light from the light sources 2 and 9 at the position of the collimator lenses 4 and 11 can be arbitrarily set according to the mounting direction of the semiconductor laser as the light sources 2 and 9. In general, there is a preferable direction from the relationship between the light utilization factor and the intensity distribution on the pupil of the objective lens, the light source for BD spreads in the 45 degree direction, and the light source for DVD and CD spreads in the pit direction of the optical disc 30. In many cases, the corners are arranged in a wide direction.

  In the present embodiment, the light amount monitor 19 is positioned in the V direction, which is the direction in which the light spread angle is maximum, as shown in FIG. 2B with respect to the light source 2 for BD, and As shown in FIG. 2 (c), the light source 9 for DVD and CD is positioned in a 45 degree direction which is intermediate between the H direction and the V direction, which is the direction in which the light spread angle is minimized. Yes. For example, a photodiode having a light receiving portion with a diameter of 0.8 mm is disposed as the light amount monitor 19 at a position 2.5 mm from the center of the optical axis of each of the light sources 2 and 9.

  Here, a change in the amount of light received by the light quantity monitor 19 when the holder 17 on which the collimator lens 4 and the light quantity monitor 19 are mounted will be described. FIG. 4 shows the change in the amount of light received by the light amount monitor 19 (the detected light amount of the light amount detection unit 20) when the collimator lens 4 and the light amount monitor 19 are moved when the emitted light amount of the light source is constant with respect to the light amount distribution of the light source. It is a graph shown about the case where the attachment direction of the light quantity monitor 19 is a H direction, a V direction, and a 45 degree direction. FIG. 4 shows an example in which the spread angle of light emitted from the light source is 9 degrees in the H direction and 20 degrees in the V direction. In FIG. 4, the plus direction of the lens position is the direction away from the light source.

  As shown in FIG. 4, when the light quantity monitor 19 is arranged in the V direction with respect to the light quantity distribution, when the collimator lens 4 and the light quantity monitor 19 are separated from the light source, the amount of light received by the light quantity monitor 19 decreases. On the other hand, when the light quantity monitor 19 is disposed in the 45 degree direction or the H direction with respect to the light quantity distribution, the amount of received light increases when the collimator lens 4 and the light quantity monitor 19 are separated from the light source. This is because when the distance from the light source of the light quantity monitor 19 changes, the density of the received light quantity changes, and at the same time, the position of the light quantity monitor 19 on the Gaussian distribution also changes. This is because the influence of the position change on the Gaussian distribution becomes large on the side where the spread angle is small (45 degrees direction, H direction) where the change of the intensity distribution is larger than the direction (direction).

  FIG. 5 is a graph showing the change rate of the received light amount of the light amount monitor 19 with respect to the position of the collimator lens 4 when the light amount emitted from the light source is constant. As shown in FIG. 5, the direction in which the amount of received light increases differs between the V direction and the other directions, and the rate of change in the H direction is the largest.

  In the optical pickup device 1, during the BD recording / reproducing operation, in order to make the emitted light amount of the objective lens 3 substantially constant even when the collimator lens 4 moves, the light pickup device 1 is based on the light amount of the light source 2 detected by the light amount monitor 19. The amount of light emitted from the light source 2 is controlled. For this purpose, as will be described later, it is preferable that the amount of light received by the light amount monitor 19 decreases as the collimator lens 4 moves away from the light source 2.

  Therefore, in the present embodiment, the light amount monitor 19 is arranged in the V direction with respect to the light source 2 for BD. As shown in FIGS. 4 and 5, in the V direction, unlike the other directions, when the collimator lens 4 moves away from the light source 2, the amount of light received by the light amount monitor 19 decreases. In order to control the amount of light emitted from the light source 2 based on the amount of light from the light source 2 detected by the light amount monitor 19, it is preferable that the rate of change in the amount of light received by the light amount monitor 19 is small. Also from this point, it is preferable to arrange the light quantity monitor 19 in the V direction with respect to the light source 2 for BD.

  Further, in the optical pickup device 1, at the start of the BD recording / reproducing operation, the light source 9 for DVD and CD emits light with a constant light amount, and the collimator is based on the light amount of the light source 9 detected by the light amount monitor 19. The position of the lens 4 is detected. For this purpose, it is preferable that the change in the amount of light detected by the light amount monitor 19 when the collimator lens 4 moves is large to some extent. As shown in FIG. 5, the change rate of the detected light amount of the light amount monitor 19 is the largest when it is arranged in the H direction with respect to the light source. However, in the H direction, the amount of received light is small as shown in FIG.

  Therefore, in the optical pickup device 1 of the present embodiment, the light amount monitor 19 is positioned in a 45-degree direction that is intermediate between the H direction and the V direction with respect to the light source 9 for DVD and CD. The direction of 45 degrees is preferable because the amount of light received by the light amount monitor 19 is large to some extent as shown in FIG. 4, and the rate of change in the amount of light received by movement of the collimator lens 4 is also somewhat large as shown in FIG. In addition, as long as it is between the H direction and the V direction, the direction is not limited to 45 degrees.

  Next, the operation of the optical pickup device 1 will be described.

  The optical pickup device 1 detects the position of the collimator lens 4 in the optical axis direction at the start of the BD recording / reproducing operation, and then moves the collimator lens 4 to a specified position corresponding to the optical disc 30 that is a BD. Thereafter, recording and reproduction operations are started.

  First, an operation for detecting the position of the collimator lens 4 in the optical axis direction at the start of the BD recording / reproducing operation will be described.

  The controller 25 causes the light source 9 for DVD and CD to emit light. A part of the light emitted from the light source 9 is reflected by the polarization beam splitter 13 and enters the light amount monitor 16, and the remaining light passes through the polarization beam splitter 13. A part of the light from the light source 9 that has passed through the polarization beam splitter 13 is detected by a light amount monitor 19 installed in the holder 17.

  The light amount detection unit 21 detects the light amount of light detected by the light amount monitor 16, and the APC drive unit 22 makes the emission light amount of the light source 9 constant at a predetermined light amount based on the light amount detected by the light amount detection unit 21. Control to be.

  In a state in which the light source 9 emits light with a predetermined light amount by the control of the APC driving unit 22, the light amount detection unit 20 detects the light amount of light detected by the light amount monitor 19, and the detection result is used as the position detection unit 23. Output to.

  Between the position of the collimator lens 4 in the optical axis direction and the light amount of light detected by the light amount monitor 19, there is a relationship as shown in the 45-degree data in FIG. When the light source 9 emits light constantly with a predetermined light amount, the position detector 23 determines the position of the collimator lens 4 in the optical axis direction as shown in FIG. 4 and the light amount detected by the light amount monitor 19. A lens position table indicating the relationship is stored in advance, and the current position of the collimator lens 4 in the optical axis direction is detected based on the lens position table and the light amount detection result input from the light amount detection unit 20. .

  When the current position of the collimator lens 4 in the optical axis direction is detected in this way, the controller 25 drives the motor to drive the stepping motor 18 and move the collimator lens 4 to a specified position corresponding to the optical disk 30. The unit 24 is controlled. The controller 25 determines whether or not the collimator lens 4 has reached a specified position based on the position detection result based on the lens position table by the position detection unit 23 and the detection result of the light amount detection unit 20 while the stepping motor 18 is being driven. When the prescribed position is reached, the motor driving unit 24 stops the driving of the stepping motor 18.

  As described above, when the collimator lens 4 is moved to a specified position corresponding to the optical disc 30, the controller 25 turns off the light source 9 for DVD and CD, and performs recording and reproducing operations for the BD. The light source 2 emits light.

  The P-polarized light emitted from the light source 2 passes through the polarization beam splitter 6, is converted into a substantially parallel light beam by the collimator lens 4, is converted into circularly polarized light by the quarter-wave plate 5, and then the objective lens. 3 is condensed on the recording layer of the optical disc 30.

  The circularly polarized reflected light reflected by the optical disk 30 passes through the objective lens 3, is converted to S-polarized light by the quarter-wave plate 5, passes through the collimator lens 4, and is reflected by the polarizing beam splitter 6. The light is incident on the photodetector 7 by the detection lens 8.

  The light detected by the photodetector 7 is converted into an electrical signal, which is used to generate an information signal, a focus error signal, a tracking error signal, and the like in a signal processing circuit (not shown).

  As described above, in the BD, spherical aberration occurs in the objective lens 3 due to an error in the thickness of the cover layer of the optical disc 30. In order to correct this spherical aberration, the controller 25 moves the collimator lens 4 by driving the stepping motor 18 by the motor driving unit 24 based on the amplitude of the light detected by the photodetector 7.

  A part of the light from the light source 2 enters the light amount monitor 19, and the light amount detection unit 20 detects the light amount of the light detected by the light amount monitor 19. The APC driving unit 22 emits the light source 2 based on the light amount detected by the light amount detecting unit 20 in order to make the emitted light amount of the objective lens 3 substantially constant even when the collimator lens 4 moves for correcting spherical aberration. Control the amount of light.

  Here, the APC control of the light source 2 will be described. FIG. 6 shows the amount of light emitted from the objective lens 3 when the collimator lens 4 is moved in the optical axis direction and when the amount of light emitted from the light source 2 is constant and when the APC drive is performed using the detection result of the light amount detector 20. It is a figure which shows a change.

  Even if the amount of light emitted from the light source 2 is constant, the light utilization rate changes as the collimator lens 4 moves in the optical axis direction, so the amount of light emitted from the objective lens 3 changes. As shown in FIG. 6, when the amount of light emitted from the light source 2 is constant, the amount of light emitted from the objective lens 3 decreases as the collimator lens 4 moves away from the light source 2. For this reason, in order to make the amount of light emitted from the objective lens 3 substantially constant even when the collimator lens 4 moves, it is necessary to control the amount of light emitted from the light source 2 to increase as the collimator lens 4 moves away from the light source 2. There is.

  On the other hand, the amount of light received by the light amount monitor 19 changes as the collimator lens 4 moves. As described above, in the optical pickup device 1, the light amount monitor 19 is arranged in the V direction with respect to the BD light source 2, so that the emitted light amount of the light source 2 is as shown in FIGS. 4 and 5. In a fixed case, when the collimator lens 4 moves away from the light source 2, the amount of light received by the light amount monitor 19 decreases. If the amount of light emitted from the light source 2 is controlled so that the amount of light received by the light amount monitor 19 that changes in this way is substantially constant, the amount of light emitted from the light source 2 is controlled to increase as the collimator lens 4 moves away from the light source 2. become. For this reason, by using the detection result of the light quantity detection unit 20 and APC driving the light source 2 by the APC drive unit 22, as shown in FIG. 6, the emission light quantity of the objective lens 3 can be controlled to be substantially constant. .

  Next, DVD and CD recording and reproducing operations will be described. First, the controller 25 causes the light source 9 for DVD and CD to emit light. A part of the P-polarized light emitted from the light source 9 is reflected by the polarization beam splitter 13 and enters the light amount monitor 16, and the remaining light passes through the polarization beam splitter 13.

  The light amount detection unit 21 detects the light amount of light detected by the light amount monitor 16, and the APC drive unit 22 makes the emission light amount of the light source 9 constant at a predetermined light amount based on the light amount detected by the light amount detection unit 21. Control to be.

  The light from the light source 9 that has passed through the polarization beam splitter 6 is converted into a substantially parallel light beam by the collimator lens 11, converted into circularly polarized light by the quarter-wave plate 12, and then recorded on the optical disk 30 by the objective lens 10. Focused on the layer.

  The circularly reflected light reflected by the optical disk 30 passes through the objective lens 10, is converted to S-polarized light by the quarter-wave plate 12, passes through the collimator lens 11, and is reflected by the polarizing beam splitter 13. The detection lens 15 enters the photodetector 14.

  The light detected by the photodetector 14 is converted into an electrical signal, which is used to generate an information signal, a focus error signal, a tracking error signal, etc. in a signal processing circuit (not shown).

  As described above, in the present embodiment, the light source 9 for DVD and CD is made to emit light at a predetermined light amount, and the holder based on the light amount from the light source 9 detected by the light amount monitor 19 installed on the holder 17. Since the position of the collimator lens 4 mounted on the optical axis direction in the optical axis direction is detected, a dedicated detector for detecting the position of the collimator lens 4 and a dedicated optical path are not required. For this reason, it is possible to detect the position of the collimator lens 4 in real time without complicating or increasing the size of the apparatus configuration.

  Since the light quantity monitor 19 only detects a part of the light from the light source 9, it is only necessary to attach it by mechanical positioning when assembling the apparatus, and there is no need to adjust the position. For this reason, it is not necessary to prepare an adjusting device while suppressing an increase in the number of steps for assembling the device.

  As shown in FIG. 7, instead of the light quantity monitor 16 of FIG. 1, a light quantity monitor 27 that is disposed in the same package as the semiconductor laser of the light source 9 and detects light leaking from the rear surface of the semiconductor laser chip is used. Also good. Further, as shown in FIG. 7, a collimator lens 11 for DVD and CD may be mounted on the holder 17.

  The positions of the light quantity monitors 16 and 27 used for controlling the emitted light quantity of the light source 9 for DVD and CD are not limited to the positions shown in FIGS. 1 and 7, but for DVD and CD as shown in FIG. When the collimator lens 11 is configured to be movable, the collimator lens 11 is closer to the light source 9 than the collimator lens 11 in order to avoid fluctuations in the amount of light from the light source 9 due to movement of the collimator lens 11. Is preferred.

DESCRIPTION OF SYMBOLS 1 Optical pick-up apparatus 2,9 Light source 3,10 Objective lens 4,11 Collimator lens 5,12 Quarter wave plate 6,13 Polarization beam splitter 7,14 Photo detector 8,15 Detection lens 16,19,27 Light quantity Monitor 17 Holder 18 Stepping motor 20, 21 Light amount detection unit 22 APC drive unit 23 Position detection unit 24 Motor drive unit 25 Controller 30 Optical disc

Claims (2)

A first light source that emits light of a predetermined wavelength;
A second light source that emits light having a wavelength different from that of the first light source;
An objective lens for causing the light emitted from the first light source to enter the optical disc;
A divergence angle conversion element that is provided between the first light source and the objective lens and changes a divergence angle of light emitted from the first light source;
Moving means for moving the holder holding the divergence angle conversion element in the optical axis direction;
In the holder, a first light amount monitor that is provided at a position where the light emitted from the first and second light sources can enter, and detects the light emitted from the first and second light sources, respectively.
A second light amount monitor for detecting light emitted from the second light source;
Light source control means for controlling the emitted light amounts of the first and second light sources based on the light amounts of light detected by the first and second light amount monitors,
When the second light source emits light and the light amount emitted from the second light source is controlled to a predetermined light amount based on the light amount detected by the second light amount monitor by the light source control means, Light comprising: position detecting means for detecting the position of the divergence angle conversion element in the optical axis direction based on the amount of light from the second light source detected by the first light amount monitor. Pickup device.   The first light quantity monitor is a direction in which the spread angle of light from the first light source is maximum with respect to the first light source, and light from the second light source with respect to the second light source. The optical pickup device according to claim 1, wherein the divergence angle is arranged between a maximum direction and a minimum direction.

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