JP2008293601A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup which detects, in a simple and inexpensive configuration, a reference position for moving a movable lens movably provided in the optical axis direction to correct the spherical aberration. <P>SOLUTION: In this optical pickup 1, the collimator lens 4 is movably arranged in the optical axis direction to correct the spherical aberration, and a second optical detector 10 to detect the power of the light beam from the light source 2 receives part of the light beam emitted from the light source 2 through the collimator lens 4. Then, the reference position for moving the collimator lens 4 is detected by utilizing the phenomenon that the converging and diverging state of the light beam changes when moving the collimator lens 4 and the detecting state changes in the second optical detector 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical pickup device that enables reading and writing of information by irradiating an optical recording medium with a light beam, and in particular, a movable lens that is movable in the optical axis direction in order to correct spherical aberration. The present invention relates to a configuration of an optical pickup device.

  Optical recording media such as compact discs (hereinafter referred to as CDs) and digital versatile discs (hereinafter referred to as DVDs) are widely used. Further, in recent years, in order to increase the amount of information on an optical recording medium, research to increase the density of information that can be recorded on the optical recording medium has been advanced, and information such as a Blu-ray disc (hereinafter referred to as BD) can be recorded at high density. Optical recording media are also starting to be put into practical use. Reading of information from such an optical recording medium and writing of information to the optical recording medium are performed using an optical pickup device.

  By the way, the BD is a two-layer disc having two recording layers according to the standard, and a transparent cover layer (here, the recording layer and the recording layer) provided to protect the recording layer by the position of the recording layer. The thickness of the intermediate layer provided between the two is also expressed as a transparent cover layer. For this reason, in the optical pickup device corresponding to BD, the generation of spherical aberration caused by the difference in the thickness of the transparent cover layer becomes a problem.

  And in the optical pickup device corresponding to BD, since it is necessary to narrow down the beam spot of the light beam condensed on the recording layer of the optical recording medium, laser light having a short wavelength (for example, wavelength 405 nm) is used, An objective lens having a large numerical aperture (NA) (for example, NA = 0.85) is used. For this reason, in the optical pickup device corresponding to BD, the influence of spherical aberration generated in proportion to the fourth power of the NA of the objective lens becomes large, and a mechanism for correcting the spherical aberration becomes essential.

  There have been many proposals for a mechanism for correcting such spherical aberration. For example, an expander lens having at least one movable lens that moves in the optical axis direction is disposed in the optical system of the optical pickup device, and the movable lens is A mechanism for correcting spherical aberration by moving in the optical axis direction has been proposed (see, for example, Patent Documents 1 and 2). Similarly, as a mechanism for correcting spherical aberration using a movable lens, a technique for moving a collimator lens arranged in an optical system of an optical pickup device in the optical axis direction is also known.

  By the way, when the spherical aberration is corrected by moving the movable lens in this way, for example, as shown in Patent Documents 1 and 2, the reference position of the movable lens is detected, and the distance from the reference position is determined. Management is performed according to the number of pulses of the stepping motor. In the configuration of Patent Document 1, in order to detect the reference position of the movable lens, a shielding plate and a position sensor (for example, a photo interrupter) having a light emitting unit and a light receiving unit are used.

However, in the case of the configuration of Patent Document 1, since it is necessary to separately prepare a position sensor such as a photo interrupter, there is a problem that the manufacturing cost of the optical pickup device increases. Considering such points, the optical pickup device of Patent Document 2 includes a shielding plate that moves integrally with the movable lens in the optical axis direction, and at least a part of the laser light emitted from the light source by the shielding plate. A light detecting means for detecting a reference position which is a movement reference of the movable lens when the light is blocked, and the light detecting means narrows down the laser light emitted from the light source and the light source and irradiates the signal surface. Between the two and a photodetector provided in advance. According to this, since a position sensor such as a photo interrupter having a light emitting part and a light receiving part is not required, the optical pickup device can be provided at low cost.
JP 200345068 A JP 2006-244646 A

  However, in the case of the configuration of Patent Document 2, a front plate photodetector or an optical disk provided in advance for detecting and controlling the laser power of the laser light source by providing a shielding plate that moves integrally with the movable lens. It is necessary to configure the optical system of the optical pickup device so that the shielding plate blocks the laser light in any of the photodetectors for detecting the return light provided to detect the return light reflected by the signal surface There is. For this reason, there are cases where the configuration of the optical system of the optical pickup apparatus becomes complicated, such as restrictions on the configuration of the optical system of the optical pickup apparatus and the necessity of arranging an extra beam splitting prism.

  In view of the above problems, an object of the present invention is to simplify a reference position, which is a movement reference of a movable lens provided so as to be movable in the optical axis direction so as to correct spherical aberration, without using a shielding plate. It is another object of the present invention to provide an optical pickup device that can be detected with an inexpensive configuration.

  In order to achieve the above object, the present invention is disposed between a light source, an objective lens that focuses a light beam emitted from the light source on a recording layer of an optical recording medium, and the light source and the objective lens. In an optical pickup device comprising a movable lens movable in the optical axis direction and a light detection means for detecting the light beam power of the light beam emitted from the light source, the movable lens moves in the optical axis direction. The convergence and divergence state of the light beam passing therethrough is changeable, and the light detection means is provided so as to receive a part of the light beam emitted from the light source and passing through the movable lens, and the movable lens The detection of the reference position, which is the movement reference of the movable lens, can be performed by utilizing the fact that the convergence state of the light beam is changed by the movement of the light beam and the detection state of the light detection means changes. And wherein the dividing.

  According to this configuration, the reference position of the movable lens that is movable in the optical axis direction so that the spherical aberration can be corrected by using the light detection means provided for detecting and controlling the light beam power in the optical pickup device. Therefore, it is not necessary to separately provide a position sensor such as a photo interrupter. In addition, since the movable lens moves, the convergence and divergence state of the light beam passing through it changes, and the detection state in the light detection means changes, so that the reference position of the movable lens is detected. In addition, it is not necessary to provide a shielding plate as found in the conventional configuration. Therefore, it is possible to provide an optical pickup device that can detect a reference position, which is a reference for movement of a movable lens provided so as to be movable in the optical axis direction, with a simple and inexpensive configuration.

  According to the present invention, in the optical pickup device having the above-described configuration, when the movable lens is moved, the light amount of the light beam detected by the light detection unit changes with the movement of the movable lens, and the movable lens is moved. The reference position may be the position of the movable lens when the peak is obtained by providing the peak within the movable range of the lens.

  In this configuration, the position of the movable lens when the light amount of the light beam detected by the light detection means shows a peak does not vary as long as the configuration of the optical pickup device is constant. Therefore, the position of the movable lens when the light amount of the light beam received by the light detection means shows a peak can be set as the reference position by moving the movable lens.

  According to the present invention, in the optical pickup device having the above-described configuration, when the movable lens is moved within a movable range, the beam spot diameter of the light beam detected by the light detection unit gradually decreases toward the minimum diameter. The light receiving area formed on the light detecting means has the same shape as the beam spot of the minimum diameter (meaning the same size). And a second light receiving region surrounding the first light receiving region, and the reference position is such that a light beam is received only in the first light receiving region. In this case, the position of the movable lens may be used.

  In this configuration, the position of the movable lens when the beam spot diameter of the light beam detected by the light detection means becomes the minimum diameter does not change. Therefore, the position of the movable lens where the beam spot diameter of the light beam becomes the minimum diameter by the light detection means, that is, the position of the movable lens when the light beam is received only in the first light receiving region is set as the reference position. it can. In this configuration, since there is no need to search for a position where the light amount of the light beam received by the photodetector reaches a peak, it is movable when the light amount of the light beam received by the light detection means shows a peak. Compared to the above-described configuration in which the lens position is the reference position, the configuration for detecting the reference position can be simplified.

  In the optical pickup device having the above-described configuration, the movable lens may be a collimating lens. The configuration in which spherical aberration is corrected by moving the collimating lens is preferable because the configuration of the optical system is simpler than the configuration in which spherical aberration is corrected using an expander lens. Further, even in a configuration in which the collimating lens is moved to correct the spherical aberration, it is necessary to detect the reference position of the collimating lens, which is preferable because the reference position can be detected by the configuration of the present invention. .

  In the optical pickup apparatus having the above-described configuration, the optical recording medium may include a Blu-ray disc. In the current BD, the problem of spherical aberration is particularly serious, and a mechanism for correcting spherical aberration is essential. Therefore, in the optical pickup device corresponding to the BD, the effect that the reference position as the movement reference of the movable lens provided to be movable in the optical axis direction can be detected with a simple and inexpensive configuration is particularly effective.

  According to the optical pickup device of the present invention, a simple and inexpensive configuration without using a shielding plate can be used as a reference position for a movable lens provided to be movable in the optical axis direction so that spherical aberration can be corrected. Can be detected.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, embodiment shown here is an example and this invention is not limited to embodiment shown here.

(First embodiment)
FIG. 1 is a schematic diagram showing the configuration of the optical pickup device of the first embodiment. The optical pickup device 1 of the first embodiment is provided so as to be able to read information recorded on a BD (optical recording medium 20) and write information to the BD. As shown in FIG. 1, the optical system of the optical pickup device 1 includes a light source 2, a polarization beam splitter 3, a collimator lens 4, a rising mirror 5, a quarter wavelength plate 6, an objective lens 7, 1 photo detector 8, the condensing lens 9, and the 2nd photo detector 10 are provided.

  The light source 2 is a semiconductor laser that emits laser light having a wavelength of 405 nm band for BD. The driving of the light source 2 is controlled by the light source control unit 13. When reading information from the optical recording medium 20 or writing information to the optical recording medium 20, the light source controller 13 performs APC (Auto) so that the laser power of the laser light emitted from the light source 2 is constant. The driving of the light source 2 is controlled by (Power Control) driving. The light source control unit 13 receives information on the laser power of the laser light emitted from the light source 2 from the second photodetector 10 that functions as a so-called front monitor photodetector.

  In the present embodiment, the number of light sources is one. However, when the optical pickup device is compatible with optical recording media other than BD (for example, DVD, CD), the number of light sources may be increased as appropriate. Absent.

  The polarization beam splitter 3 has a function of transmitting one of two linearly polarized light whose polarization directions are orthogonal to each other and reflecting the other. The optical pickup device 1 is configured such that laser light is transmitted in the forward path and laser light is reflected in the return path.

  The collimating lens 4 is provided so that its position can be moved in the optical axis direction, and the convergence / divergence state of the laser light passing through the collimating lens 4 can be changed. The BD, which is an optical recording medium 20 that the optical pickup 1 can handle, is a two-layer disc provided with two recording layers 20a as a standard (FIG. 1 shows only one recording layer for convenience). However, there are two recording layers). For this reason, as described above, the thickness of the transparent cover layer 20b differs for each recording layer 20a, and the occurrence of spherical aberration becomes a problem when information recorded on the BD is read by the optical pickup device 1. Therefore, the collimating lens 4 is provided so as to be movable in the optical axis direction, and the spherical aberration can be corrected by changing the convergence / divergence state of the laser light incident on the objective lens 7.

  The collimating lens 4 can be moved in the optical axis direction by a collimating lens driving unit 11. FIG. 2 is a schematic plan view showing the configuration of the collimating lens driving unit 11 provided in the optical pickup device 1.

  As shown in FIG. 2, the collimating lens driving unit 11 includes a movable holder 21, two guide shafts 22, a lead nut 23, a screw 24, and a stepping motor 25. The movable holder 21 that holds the collimating lens 4 is slidably supported by the two guide shafts 22. A lead nut 23 is attached to the movable holder 21, and a screw 24 is engaged with the lead nut 23. The screw 24 is rotatably provided by a stepping motor 25.

  For this reason, when the screw 24 is rotated by the stepping motor 25, the movable holder 21 slides on the guide shaft 22 according to the rotation direction of the screw 24, and the position of the collimating lens 4 is moved. At this time, since the stepping motor 25 is used, the movement amount of the movable lens 21 can be accurately managed by the step amount from the reference position if a reference position serving as a movement reference of the collimating lens 4 is provided. The collimating lens driving unit 11 is controlled by the collimating lens driving control unit 12. Further, a reference position serving as a movement reference for the collimating lens 4 will be described later.

  Returning to FIG. 1, the raising mirror 5 reflects a part of the laser beam sent from the collimating lens 4 to make the laser beam in a direction orthogonal to the recording layer 20 a of the optical recording medium 20. Further, the remaining part sent from the collimating lens 4 is transmitted and guided to the second photodetector 10 side.

  The quarter wavelength plate 6 is arranged so as to be circularly polarized when linearly polarized light is incident. Further, the circularly polarized light incident on the quarter wavelength plate 6 is converted into linearly polarized light. The quarter wavelength plate 6 functions as an optical isolator in cooperation with the polarization beam splitter 3.

  The objective lens 7 focuses the incident laser light on the recording layer 20 a of the optical recording medium 20. The objective lens 7 can be moved in a focus direction parallel to the optical axis direction and a direction parallel to the radial direction of the optical recording medium 20 by an actuator (not shown). As a result, the objective lens 7 can always be focused on the recording layer 20a of the optical recording medium 20, and a beam spot formed by being condensed by the objective lens 7 is formed on the optical recording medium 20. Can always follow the track being played.

  The laser beam condensed on the recording layer 20 a of the optical recording medium 20 is reflected, passes through the objective lens 7, and the polarization direction is orthogonal to the laser beam (linearly polarized light) emitted from the light source 2 by the quarter wavelength plate 6. The linearly polarized light is reflected by the rising mirror 5, passes through the collimating lens 4, is reflected by the polarizing beam splitter 3, and is condensed on the first photodetector 8.

  The first photodetector 8 includes a light receiving region (not shown) and converts an optical signal into an electrical signal. The electrical signal converted by the first photodetector 8 is sent to a signal processing unit (not shown), where an RF signal, a focus error signal (FE signal), a tracking error signal (TE signal), and the like are generated. Information is read by the RF signal, and servo control (focusing control, tracking control) is performed based on the FE signal and the TE signal.

  The condenser lens 9 has a function of condensing the laser light emitted from the light source 2 and transmitted through the raising mirror 5 onto the second photodetector 10.

  The second photodetector 10 has, for example, a circular light receiving region (not shown), receives the laser light emitted from the light source 2 there, and sets the laser power level of the laser light emitted from the light source 2. To detect. The level of the detected laser power is sent to the light source control unit 13 and emitted from the light source 2 when reading information from the optical recording medium 20 or recording information on the optical recording medium 20 as described above. The light source 2 is controlled so that the laser power of the laser beam is constant.

  The second photodetector 10 is also used to detect a reference position that is a movement reference of the collimating lens 4 that is provided so as to be movable in the optical axis direction. For this reason, as shown in FIG. 3, the amount of light beam detected in the light receiving region of the second photodetector 10 (indicated by the light receiving rate in FIG. 3) The optical pickup device 1 is designed so that when it is moved from one end to the other, it changes with the movement and shows a peak within the movable range of the collimating lens 4.

  Specifically, for example, when the collimating lens 4 is disposed in the vicinity of the center of the movable range, the beam spot formed on the second photodetector 10 is in the most narrowed state (has the smallest diameter). The optical system of the optical pickup device 1 is configured so that the diameter of the light receiving region formed in a circle is substantially the same as the spot diameter of the above-mentioned most narrowed beam spot. In this manner, the movement of the collimating lens 4 changes the convergence / divergence state of the laser light passing through the collimating lens 4, thereby changing the size of the beam spot formed on the second photodetector 10. The light receiving rate in the second photodetector 10 changes. And the peak of the light reception rate is also obtained.

  Since the position of the collimator lens 4 when the light reception rate thus obtained is maximum is constant, the position of the collimator lens 4 when the light reception rate is maximum is set as a reference position serving as a movement reference. It can be. Therefore, by detecting the position of the collimating lens when the light receiving rate reaches a peak using the second photodetector 10, a reference position serving as a movement reference of the collimating lens 4 provided to be movable in the optical axis direction is detected. it can.

  FIG. 3 is a graph showing the change in the light receiving rate in the second photodetector 10 with respect to the change in the position of the collimating lens 4 in the optical pickup device 1. The light receiving rate at the second photodetector 10 is a percentage expressed as a percentage when the amount of laser light emitted from the light source 2 is 1. The zero position at the collimating lens position in FIG. 3 is determined appropriately and does not indicate the reference position. The plus direction based on this zero position corresponds to the direction in which the collimating lens 4 is brought close to the rising mirror 5. To do. FIG. 3 is an example of the present embodiment, and the change in the light receiving rate at the second photodetector with respect to the change in the collimating lens position depending on the configuration of the optical system (design and arrangement of the optical member). Will change.

  In the present embodiment, the light receiving area of the second photodetector 10 included in the optical pickup device 1 is circular. However, the present invention is not limited to this. For example, as shown in FIG. The light receiving area (A to D may be independent light receiving areas) may be used. In this way, for example, when the optical pickup device 1 is assembled, it is easy to adjust the displacement of the second photodetector 10 with respect to the optical axis, and the second photodetector 10 can be easily placed at an accurate position.

  Next, in the optical pickup device 1 of the present embodiment, a flow in the case of detecting a reference position serving as a movement reference of the collimating lens 4 will be described with reference to FIG. The reference position of the collimating lens 4 is detected by a command from the controller 14 that controls the entire optical pickup device 1, for example, every time before reproduction or recording of the optical recording medium 20 is started. FIG. 5 is a flowchart showing a flow of detecting a reference position which is a movement reference of the collimating lens 4.

  First, a command is issued from the controller 14 to the collimating lens drive control unit 12, and the collimating lens 4 is moved to one end of the movable range (step S1). At this point, since the reference position that is the movement reference of the collimating lens 4 has not yet been detected, for example, the previously detected reference position may be used. At this stage, it is not necessary to move precisely to the end of the movable range.

  Next, according to a command from the controller 14, the light source control unit 13 supplies a predetermined current to the light source 2, and controls the light source 2 so that the current value becomes constant (step S2). At this stage, when the light source 2 is APC-driven, the amount of light detected by the second photodetector 10 becomes constant, and the reference position of the collimating lens 4 cannot be determined. Therefore, the current is controlled to be constant.

  By supplying a predetermined current to the light source 2, laser light is emitted, and collection of light amount data detected by the second photodetector 10 is started (step S3). The light amount data is collected by the controller 14. Then, a command is issued from the controller 14 to the collimating lens drive control unit 12, the movement of the collimating lens 4 is started (step S4), and the collimating lens 4 is moved to the other end of the movable range (step S5). Whether or not the movable range has been moved to the other end may be determined based on a previously detected reference position.

  Next, the controller 14 uses the detected light quantity data to find the position of the collimator lens 4 when the light quantity shows a peak, and detects this position as a reference position (step S6). Thereafter, the position of the collimating lens 4 is moved with reference to the reference position detected here.

  In addition, after the reference position serving as the movement reference of the collimating lens 4 is detected, information is read from the optical recording medium 20 and information is written to the optical recording medium 20. The light source controller 13 switches the driving of the light source 2 to APC driving (step S7).

  In this embodiment, since the collimating lens 4 is moved from one end to the other end of the movable range with reference to the previously detected reference position, the range in which the collimating lens 4 is moved becomes inaccurate, and the amount of light is reduced. There may be a case where the position of the collimating lens 4 in the case of showing a peak cannot be detected. In such a case, after step S6, the previously detected reference position may be corrected and steps S1 to S6 may be performed again.

(Second Embodiment)
The optical pickup device of the second embodiment is different from the optical pickup device 1 of the first embodiment except for the configuration of the second photodetector 10 and the method of detecting the reference position that is the movement reference of the collimating lens 4. Is basically the same. Therefore, only this different point will be described below. Further, the same reference numerals are given to the portions overlapping with those in the first embodiment.

  FIG. 6 is a schematic plan view showing the configuration of the second photodetector 30 provided in the optical pickup device of the second embodiment. As shown in FIG. 6, the second photodetector 30 includes a circular first light receiving region 30a and a second light receiving region 30a that is formed concentrically with the first light receiving region 30a and surrounds the first light receiving region 30a. Light receiving region 30b. The first light receiving region 30a and the second light receiving region 30b are not electrically connected, and both are independent.

  Also in the optical pickup device of the second embodiment, similarly to the case of the first embodiment, for example, when the collimating lens 4 is arranged near the center of the movable range, the beam spot formed on the second photodetector 30 The optical system of the optical pickup device 1 is configured so that is in the most narrowed state (has the smallest diameter). The diameter of the first light receiving region 30a formed in a circular shape on the second photodetector 30 is designed to be substantially the same as the spot diameter of the most narrow beam spot (substantially circular). Yes. On the other hand, the diameter of the second light receiving region 30b is set to an appropriate diameter larger than that of the first light receiving region 30a.

  In the present embodiment, the first light receiving region 30a is formed in a circular shape, but the present invention is not limited to this. For example, it may be a polygon in which the above-mentioned beam spot having the minimum diameter is inscribed, or may be a shape that is at least partially in contact with the above-mentioned beam spot having the minimum diameter and surrounds the beam spot. Further, the shape of the second light receiving region 30b may be different from that of the present embodiment.

  When the second light detector 30 is designed in this way, the first light receiving region 30a and the second light receiving region 30a and second light beams are moved until the beam spot formed on the second light detector 30 reaches the minimum diameter due to the movement of the collimating lens 4. The laser beam is detected both in the light receiving region 30b. On the other hand, when the collimating lens 4 moves to a predetermined position and the beam spot formed on the second photodetector 30 has the minimum diameter, the laser light is detected only by the first light receiving region 30a.

  Since the position of the collimating lens 4 is constant when the laser light is detected only in the first light receiving region 30a, the position of the collimating lens 4 in this case can be set as a reference position that serves as a movement reference. it can. Therefore, by detecting the position of the collimator lens 4 when the laser beam is detected only by the first light receiving region 30a using the second photodetector 30, the collimator lens 4 provided to be movable in the optical axis direction. It is possible to detect a reference position as a movement reference.

  Next, a flow in the case of detecting a reference position that is a reference for movement of the collimating lens 4 in the optical pickup device of the present embodiment will be described with reference to FIG. The reference position of the collimating lens 4 is detected by a command from the controller 14 that controls the entire optical pickup device. For example, it is performed every time before reproduction or recording of the optical recording medium 20 is started. FIG. 7 is a flowchart showing a flow of detecting a reference position which is a movement reference of the collimator lens 4 in the optical pickup device of the present embodiment.

  First, a command is issued from the controller 14 to the collimating lens drive control unit 12, and the collimating lens 4 is moved to one end of the movable range (step S11). At this point in time, the reference position that is the movement reference of the collimating lens 4 has not been detected yet, so the previously detected reference position may be used. This is the same as in the case of the first embodiment.

  Next, laser light is emitted from the light source 2, and monitoring of the detection state of the laser light by the second photodetector 30 is started by the controller 14 (step S12). Specifically, when laser light is detected in the first light receiving region 30a and the second light receiving region 30b (when the signal becomes larger than a certain threshold value, etc.), it is turned ON, and when the laser light is not detected It is set to OFF, and this state is monitored in association with the position of the collimating lens 4.

  Thereafter, a command is issued from the controller 14 to the collimating lens drive control unit 12, the movement of the collimating lens 4 is started (step S13), and the collimating lens 4 is moved to the other end of the movable range (step S14). Whether or not the other end has been moved may be determined based on the previously detected reference position, and is the same as in the first embodiment.

  Next, based on the monitoring result, the controller 14 receives the laser beam when the first light receiving region 30a is turned on and the second light receiving region 30b is turned off (that is, only the first light receiving region 30a is received). The position of the collimating lens 4 is detected, and this position is detected as a reference position (step S15). Thereafter, the position of the collimating lens 4 is moved with reference to the reference position detected here.

  In the case of such a configuration, the controller 14 does not need to perform processing for detecting the peak of the light amount detected by the second photodetector 10 as in the first embodiment. The configuration for detecting the reference position can be simplified.

(Other)
In the first embodiment and the second embodiment described above, the configuration for detecting the reference position of the collimating lens has been described. However, the present invention is not limited to the case of the collimating lens. In the case of a movable lens that is arranged closer to the light source than a so-called front monitor photodetector (second photodetectors 10 and 30) and moves to change the convergence / divergence state of the laser light emitted from the light source. The present invention is applicable.

  In the embodiment described above, the optical pickup device corresponding to the BD is targeted. However, spherical aberration may be a problem even in the case of other optical recording media (such as HD-DVD) having a plurality of recording layers. Further, there is a problem even in an optical pickup device that is compatible with a plurality of types of optical recording media having different transparent cover layer thicknesses. Accordingly, in addition to the optical pickup device corresponding to the BD, a movable lens may be provided to correct the spherical aberration, and the present invention is also applied to such an optical pickup device.

  According to the optical pickup device of the present invention, it is possible to detect, with a simple and inexpensive configuration, a reference position serving as a movement reference of a movable lens that is provided so as to be movable in the optical axis direction so that spherical aberration can be corrected. Become. Therefore, the present invention is useful in the field of optical pickup devices.

FIG. 1 is a schematic diagram illustrating a configuration of an optical pickup device according to a first embodiment. These are the schematic plan views which show the structure of the collimating lens drive unit with which the optical pick-up apparatus of 1st Embodiment is provided. These are the graphs which show the change of the light reception rate in a 2nd photodetector with respect to the change of a collimating lens position in the optical pick-up apparatus of 1st Embodiment. These are the figures for demonstrating the modification of the 2nd photodetector with which the optical pick-up apparatus of 1st Embodiment is provided. These are the flowcharts which show the flow which detects the reference position used as the movement reference | standard of the collimating lens in the optical pick-up apparatus of 1st Embodiment. These are the schematic plan views which show the structure of the 2nd photodetector with which the optical pick-up apparatus of 2nd Embodiment is provided. These are the flowcharts which show the flow which detects the reference position used as the movement reference | standard of the collimating lens in the optical pick-up apparatus of 2nd Embodiment.

Explanation of symbols

1 Optical pickup device 2 Light source 4 Collimating lens (movable lens)
7 Objective lens 10, 30 Second light detector (light detection means)
20 optical recording medium 20a recording layer 30a first light receiving area 30b second light receiving area

Claims (5)

A light source;
An objective lens for condensing the light beam emitted from the light source on the recording layer of the optical recording medium;
A movable lens disposed between the light source and the objective lens and movable in an optical axis direction;
A light detecting means for detecting a light beam power of a light beam emitted from the light source;
In an optical pickup device comprising:
The movable lens is provided so as to be able to change a convergent divergence state of a light beam passing by moving in the optical axis direction,
The light detection means is provided so as to receive a part of a light beam emitted from the light source and passing through the movable lens,
A reference position serving as a movement reference of the movable lens is detected by utilizing the fact that the detection state of the light detection means is changed by changing the convergence / divergence state of the light beam by the movement of the movable lens. Optical pickup device. When the movable lens is moved, the light amount of the light beam detected by the light detection means is changed with the movement of the movable lens, and is provided so as to show a peak within the movable range of the movable lens,
The optical pickup device according to claim 1, wherein the reference position is a position of the movable lens when the peak is obtained. When the movable lens is moved within the movable range, the beam spot diameter of the light beam detected by the light detection means gradually decreases toward the minimum diameter, and gradually increases after reaching the minimum diameter. It is established so that the change that can be seen,
The light receiving area formed in the light detection means is composed of a first light receiving area having the same shape as the beam spot of the smallest diameter and a second light receiving area surrounding the first light receiving area,
2. The optical pickup device according to claim 1, wherein the reference position is a position of the movable lens when a light beam is received only in the first light receiving region.   4. The optical pickup device according to claim 1, wherein the movable lens is a collimating lens.   5. The optical pickup device according to claim 1, wherein the optical recording medium includes a Blu-ray disc.

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