JP4481241B2 - Optical pickup - Google Patents

Description

  The present invention relates to an optical pickup that records and / or reproduces information by irradiating an information recording medium such as an optical disk, and in particular, protects the recording surface by correcting spherical aberration. The present invention relates to an optical pickup capable of accurately recording and / or reproducing information on an information recording medium having a layer.

  As a technique for recording and reproducing digital data, optical disks such as CD (Compact Disk), MD (Mini-Disk), DVD (Digital Versatile Disk) and the like are widely used as information recording media. An optical disk is a general term for a recording medium that irradiates light on a disk in which a thin metal plate is protected with plastic and reads a signal by a change in reflected light. The optical disk includes a magneto-optical disk.

An optical pickup is a device that records and / or reproduces information by irradiating light onto an optical disc. FIG. 16 shows a front view of the main configuration of a conventional optical pickup. As shown in FIG. 16, the optical pickup includes a light source 101, a collimating lens 102, an objective lens 103, and a driving means 107 for the collimating lens. Light emitted from the light source 101 is collimated by the collimator lens 102 and then focused on the recording surface of the information recording medium 104 by the objective lens 103.

  In recent years, high-density optical discs such as Blu-ray Discs have been developed, and the capacity of optical discs has been significantly increased. In such a high-density optical disc, a protective layer that transmits light is generally formed on a recording surface on which information is recorded.

  In the optical pickup described above, when information is recorded and / or reproduced on an optical disc having such a protective layer, spherical aberration may occur when light emitted from the light source 101 passes through the protective layer. Are known.

  Therefore, conventionally, in order to perform accurate information recording / reproduction, a technique for correcting such spherical aberration by moving the collimating lens 102 in the optical axis direction by the driving device 107 has been proposed.

  For example, Patent Document 1 describes a lens driving device that converts rotation of a motor into parallel movement along the optical axis direction by a gear mechanism and transmits the translation to a collimator lens holder. This lens driving device moves the collimator lens so as to cancel the spherical aberration according to the thickness of the light transmission layer of the information recording medium by moving the collimator lens holder in the optical axis direction.

  However, in the technique of Patent Document 1, the collimating lens may be driven beyond the movable range of the collimating lens. When the collimating lens is driven beyond the movable range in this manner, the collimating lens or its peripheral members are damaged. Therefore, a technique for detecting the end of the movable range of the collimator lens, that is, the end position or the start position, has been proposed.

As an example of such a technique, Patent Document 2 discloses a technique in which a shielding plate is provided on a lens holding member that holds a collimating lens, and a position at which the shielding plate is inserted into a photo interrupter is detected as a reference position. A technique is described in which spherical aberration is corrected by moving the holding member from this reference position to a position where the amplitude of the information reproduction signal is maximized. The reference position is the end of the movable range of the lens holding device, that is, the end of the movable range of the collimating lens.
JP 11-259906 A (published September 24, 1999) Japanese Patent Laying-Open No. 2005-78735 (published March 24, 2005)

However, in the conventional technique described above, the position of the collimating lens cannot be obtained in real time when the collimating lens is moved for spherical aberration correction.

  For example, in the optical disk device described in Patent Document 2 described above, the position of the lens holding device is detected by detecting the insertion / removal of the shielding plate to / from the photo interrupter, so the lens holding device is the end of the movable range. Only when it is in the “reference position”, the position of the lens holding device, that is, the position of the collimating lens can be detected. That is, in the conventional recording / reproducing apparatus, when the user turns on the power and starts up the recording / reproducing apparatus, or when the user replaces the optical disk, there is no means for knowing the position of the collimating lens at that time.

  Therefore, in order to prevent the collimating lens from being driven beyond its movable range during the spherical aberration correction operation, the collimating lens is temporarily moved to the end of the movable range, and then the spherical aberration correction is started. It is necessary to take Therefore, there is a problem that it takes a long time to start up the recording / reproducing operation after spherical aberration correction after the user turns on the power.

  The present invention has been made in view of the above-described conventional problems, and provides an optical pickup capable of acquiring position information of a collimating lens in real time.

  In order to solve the above-described problems, an optical pickup according to the present invention is an optical pickup that includes a light source and a lens group including a collimator lens, and guides light emitted from the light source to a recording medium by the lens group. The parallelism detecting means for detecting the parallelism of the luminous flux emitted from the projector can be provided.

  When the distance between the collimating lens and the light source is equal to the focal length of the collimating lens, the light beam emitted from the light source through the collimating lens (the light beam emitted from the collimating lens) becomes parallel light. Further, when the distance between the collimating lens and the light source becomes smaller than the focal length, the emitted light beam from the collimating lens becomes divergent light, and the degree of divergence increases as the distance between the collimating lens and the light source becomes smaller. On the other hand, when the distance between the collimating lens and the light source becomes larger than the focal length, the emitted light beam from the collimating lens becomes convergent light, and the degree of convergence increases as the distance between the collimating lens and the light source increases. That is, the parallelism of the emitted light beam from the collimating lens changes monotonously according to the size of the interval between the collimating lens and the light source.

  The optical pickup can detect the parallelism of the emitted light from the collimating lens by the parallelism detecting means. Therefore, the optical pickup can detect the position of the collimating lens, that is, the distance between the collimating lens and the light source, as the parallelism of the emitted light beam from the collimating lens. That is, the optical pickup can obtain the position information of the collimating lens in real time.

  In addition, the optical pickup includes an interval changing unit that changes an interval between the collimator lens and the light source, and the interval changing unit changes the interval so that at least a detection result of the parallelism detecting unit becomes a predetermined value. It is preferable.

  In the optical pickup, first, the collimating lens is positioned at a predetermined starting position, and then the collimating lens is positioned at an optimal position for recording or reproducing information while moving the collimating lens from the starting position. According to the above configuration, the collimating lens can be positioned at this starting position by the interval changing means while the position of the collimating lens is detected in real time by the parallelism detecting means. Therefore, the collimating lens can be directly moved to a position close to the position of the collimating lens after the spherical aberration correction without once moving the collimating lens to the end of the movable range of the collimating lens. As a result, it is possible to shorten the time from the start-up of the optical pickup to the completion of spherical aberration correction.

  The optical pickup includes light source control means for controlling the amount of light emitted from the light source, and the light source control means is based on the detection result of the parallelism detection means as the divergence of the emitted light beam from the collimating lens increases. It is preferable that the amount of emitted light is controlled so that the amount of emitted light is relatively large.

  By changing the positions of the collimating lens and the light source, the parallelism of the light traveling from the collimating lens to the recording medium changes, so that the amount of light incident on the recording medium varies. Therefore, if the light source is controlled only by the emitted light quantity detection means, recording and reproduction may not be stable. According to the above configuration, since the amount of light emitted from the light source can be controlled in accordance with such a change in the position of the collimating lens, stable recording and reproduction can be performed.

  The optical pickup according to the present invention is an optical pickup that includes a light source and a lens group including a collimator lens, and guides light emitted from the light source to a recording medium by the lens group, and receives light emitted from the collimator lens. And a light reception amount detection unit that detects the amount of light received on the light reception surface, and the detection result of the light reception amount detection unit changes monotonously according to the interval between the collimating lens and the light source. It can be set as the structure by which the light-receiving surface is provided.

  According to the above configuration, since the detection result of the received light amount detection unit changes monotonously according to the distance between the collimating lens and the light source, the position information of the collimating lens can be obtained in real time as the detection result of the received light amount detection unit. it can.

  The optical pickup according to the present invention is an optical pickup that includes a light source and a lens group including a collimator lens, and guides light emitted from the light source to a recording medium by the lens group, and receives light emitted from the collimator lens. A light receiving surface for detecting the amount of light received on the light receiving surface, and the light receiving surface is fixed in a relative position with respect to a light beam emitted from the collimator lens and received by the light receiving surface. In addition, when the light beam emitted from the collimating lens is parallel light, the light receiving surface is provided so that the outer periphery of the spot of the light beam received by the light receiving surface passes on the light receiving surface. Can do.

  As described above, the parallelism of the luminous flux emitted from the collimating lens changes monotonously depending on the distance between the collimating lens and the light source. As the parallelism changes, the diameter of the light beam also changes monotonously. That is, as the divergence of the light beam increases, the diameter of the light beam increases.

  According to the configuration of the above optical pickup, when the relative position of the light receiving surface is fixed with respect to the light beam emitted from the collimating lens and received by the light receiving surface, and the light beam emitted from the collimating lens is parallel light The light receiving surface is provided so that the outer periphery of the spot of the light beam received by the light receiving surface passes over the light receiving surface. Therefore, the spot diameter also changes monotonously with a monotonous change in the diameter of the light beam emitted from the collimating lens. Accordingly, the spot area, that is, the amount of light received on the light receiving surface also changes monotonously. By detecting this received light amount by the received light amount detector, the interval between the collimating lens and the light source can be detected as the received light amount on the light receiving surface.

  The optical pickup includes an interval changing unit that changes an interval between the collimating lens and the light source, and the interval changing unit changes the interval so that at least a detection result of the received light amount detection unit becomes a predetermined value. It may be a configuration.

  The optical pickup may be configured such that the detection result of the received light amount detection unit is input to the interval changing means via a low-pass filter.

  According to the above configuration, since the high-frequency component in the detection result of the received light amount detection unit is removed and input to the interval changing means, the collimating lens is more accurate without performing erroneous collimating position control due to the output fluctuation of the light source. Position control can be performed.

  The optical pickup includes a light source control unit that controls the amount of light emitted from the light source, and the light source control unit has a small interval between the collimating lens and the light source based on at least a detection result of the received light amount detection unit. It is preferable to control the amount of emitted light so that the amount of emitted light becomes relatively larger as it becomes.

  The optical pickup according to the present invention is an optical pickup that includes a light source and a lens group including a collimator lens, and guides light emitted from the light source to a recording medium by the lens group, and receives light emitted from the collimator lens. And at least two areas, and a detection element for detecting the amount of light received in each area, the detection result of the detection element corresponding to one of the areas, or two or more areas The difference between the sum of the detection results of the detection elements corresponding to and the detection result of the detection elements corresponding to one other region, or the sum of the detection results of the detection elements corresponding to two or more other regions is a collimator. The light receiving surface may be provided so as to change monotonously according to the distance between the lens and the light source.

  According to the above configuration, the detection result of the detection element corresponding to one of the areas, or the sum of the detection results of the detection elements corresponding to two or more areas, and the detection element corresponding to the other one area As a difference between the detection result or the sum of the detection results of the detection elements corresponding to two or more other regions, information on the distance between the collimating lens and the light source, that is, position information of the collimating lens can be obtained in real time.

The optical pickup according to the present invention is an optical pickup that includes a light source and a lens group including a collimator lens, and guides light emitted from the light source to a recording medium by the lens group.
A light receiving surface that receives the light beam emitted from the collimating lens and is divided into at least two regions, and a detection element that detects the amount of light received in each region. The light receiving surface is emitted from the collimating lens and is received by the light receiving surface. The relative position with respect to the received light beam is fixed, and when the light beam emitted from the collimating lens is parallel light, the outer periphery of the spot of the light beam received by the light receiving surface passes on the light receiving surface. The light receiving surface may be provided.

  The optical pickup is provided with the light receiving surface so that the emitted light beam from the collimating lens is incident on all regions of the light receiving surface when the light beam emitted from the collimating lens is parallel light. It may be a configuration.

  Sum of the detection results of the detection elements corresponding to one of the above-mentioned areas or the detection results of the detection elements corresponding to two or more areas when the emitted light beam from the collimating lens is incident on all areas of the light receiving surface And the sum of the detection results of the detection elements corresponding to one other region or the detection results of the detection elements corresponding to two or more other regions are monotonous depending on the distance between the collimating lens and the light source. To change.

  Therefore, according to the above configuration, the position of the collimating lens can be accurately detected at a position where the light beam emitted from the collimating lens becomes parallel light and a position in the vicinity thereof. At the time of spherical aberration correction, the collimating lens emits light from the collimating lens around the position where it is parallel light, and the collimating lens is moved back and forth in the optical axis direction from this position. Determine the position. That is, according to the above configuration, it is possible to accurately detect the position of the collimating lens during the spherical aberration correction operation. Further, as described above, conventionally, the spherical aberration correction has been started from the end of the movable range of the collimating lens. According to the above configuration, the collimating lens is emitted from the collimating lens before the spherical aberration correcting operation. It becomes easy to position in advance at a position where the light beam is parallel light or a position in the vicinity thereof. Therefore, the time required for spherical aberration can be shortened.

  The optical pickup preferably includes a position information calculation unit that calculates position information of the collimating lens based on the detection result of each detection element.

  The optical pickup includes an interval changing unit that changes an interval between the collimating lens and the light source, and the interval changing unit changes the interval so that at least a calculation result of the position information calculation unit becomes a predetermined value. It can also be configured.

  In the optical pickup, it is preferable that the position information is input to the interval changing means via a low-pass filter.

  The optical pickup includes a light source control unit that controls the amount of light emitted from the light source, and the light source control unit reduces the distance between the collimating lens and the light source based on at least the calculation result of the position information calculation unit. Accordingly, it is preferable to control the amount of emitted light so that the amount of emitted light becomes relatively large.

  The light receiving surface may be provided in an optical path of a light beam from the collimating lens toward the recording medium, and the lens group includes an objective lens, and the diameter of the objective lens is larger than the diameter of the light beam emitted from the collimating lens. The light receiving surface may be arranged on the outer edge side of the cross-sectional shape of the light beam from the collimating lens toward the recording medium, rather than the objective lens.

  According to the above configuration, light that is not incident on the objective lens is incident on the light receiving surface. Therefore, the position of the collimating lens can be detected using light that is not used for recording / reproduction of the recording medium. Therefore, there is an effect that the utilization efficiency of light from the light source is high.

  Further, the lens group includes at least an objective lens that is driven in a radial direction of the recording medium, the diameter of the objective lens is set smaller than the diameter of the light beam emitted from the collimator lens, In the tangential direction, it is also possible to adopt a configuration in which the lens is disposed on the outer edge side of the cross-sectional shape of the light beam directed from the collimator lens toward the recording medium rather than the objective lens.

  The objective lens is driven in the radial direction during tracking correction operation. According to the above configuration, even if the objective lens is driven in the radial direction, the position of the collimating lens is detected without reducing the light incident on the objective lens. Can do.

  The optical pickup may include a branching unit that splits the light emitted from the collimating lens into a first light beam incident on the recording medium and a second light beam incident on the light receiving surface.

  The optical pickup may include a condensing lens that condenses the second light flux on a light receiving surface. As a result, the light can be concentrated on the light receiving surface, and thus the sensitivity of the detection element is increased.

  The optical pickup includes branching means for branching the light emitted from the collimating lens into a first light beam incident on the recording medium and a second light beam incident on the light receiving surface, and astigmatism in the second light beam. A configuration including astigmatism generating means for generating occurrence may be used.

  According to the above configuration, the shape of the light beam spot on the light receiving surface changes depending on the parallelism of the light beam emitted from the collimating lens. Since the change in the spot shape can be detected as a difference in detection results between the detection elements as described above, the position of the collimating lens can be detected in real time.

  In addition, the optical pickup includes an addition unit that calculates the sum of the detection results of the detection elements, and the light receiving surface so that the calculation result of the addition unit is constant regardless of the interval between the collimating lens and the light source. And a light source control unit that controls the amount of light emitted from the light source, and the light source control unit controls the amount of emitted light so that the calculation result of the addition unit is constant. Good.

  According to the above configuration, the light receiving surface for the position of the collimator lens and the detection element can also serve as means for detecting the amount of light emitted from the light source. Therefore, a reduction in the number of members, a reduction in cost, and a reduction in size of the optical pickup can be realized.

  In addition, the optical pickup includes an addition unit that calculates the sum of the detection results of the detection elements, and the light receiving surface is arranged so that the calculation result of the addition unit is constant regardless of the interval between the collimating lens and the light source. A light source control unit that controls the amount of light emitted from the light source, and the light source control unit calculates the calculation result of the addition unit as the distance between the collimating lens and the light source decreases based on the position information. The configuration may be such that the amount of emitted light is controlled so that is relatively large.

  The optical pickup of the present invention includes parallelism detection means for detecting the parallelism of the light beam emitted from the collimating lens.

  The parallelism of the light beam emitted from the collimator lens changes monotonously according to the distance between the collimator lens and the light source. Therefore, according to the said structure, the space | interval of a collimating lens and a light source, ie, the positional information on a collimating lens, can be obtained in real time by a parallelism detection means.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
(1-1) Outline of Configuration of Optical Pickup An optical pickup according to this embodiment will be described below with reference to FIG. FIG. 1 is a block diagram showing a main configuration of the optical pickup according to the present embodiment.

  The optical pickup according to the present embodiment is a recording / reproducing apparatus that includes an optical system 40 and a control unit 30 and records and / or reproduces information with respect to the recording medium 4 using light. In the recording medium 4, a light-transmitting protective layer 4a is formed on the recording surface 4b side on the recording layer.

  The optical system 40 includes a light source 1, a lens group (collimating lens 2, objective lens 3), a photodetector 6 (light receiving surface, received light amount detection unit, detection element) for detecting the collimating lens position, and a driving means 7 for the collimating lens. (Interval changing means) and a photodetector 8 for monitoring the light source. The photodetector 6 includes a light receiving surface 6A. On the other hand, the control means 50 includes a low-pass filter 30a, a drive means control unit 30b (interval changing means), a gain adjustment circuit 30c (light source control means), and an APC (Auto Power Control) circuit 30d (light source control means).

  When recording or reproducing information on the recording medium 4, the light emitted from the light source 1 passes through the collimating lens 2 and is condensed on the recording surface 4 b by the objective lens 3. The reflected light from the recording surface 4 b includes a signal for controlling focus and tracking with respect to the recording medium 4 or a recording signal recorded on the recording medium 4. The reflected light is incident on the objective lens 3 and then guided to a light receiving element (not shown). Regarding members not shown, conventionally known members can be applied to the optical pickup.

(1-2) Position Information of the Collimating Lens 2 The photodetector 6 according to the present embodiment detects the amount of light received by the light receiving surface 6A, and thereby the parallelism (divergence / convergence degree) of the collimating lens outgoing light beam 20 is detected. Is supposed to be detected. And the drive means control part 30b controls the drive means 7 based on the detection result of this photodetector 6, and adjusts the position of the collimating lens 2. FIG.

  In other words, in the present embodiment, the photodetector 6 is a parallelism detecting unit that detects the parallelism of the collimating lens 2. The driving unit 7 and the driving unit control unit 30b function as an interval changing unit that changes the interval between the collimating lens 2 and the light source 1.

  Here, the relationship between the parallelism of the collimating lens output light beam 20 and the position of the collimating lens 2 will be briefly described.

  When the distance between the collimating lens 2 and the light source 1 is equal to the focal length of the collimating lens 2, the collimating lens outgoing light beam 20 becomes parallel light. On the other hand, when the distance between the collimating lens 2 and the light source 1 is smaller than the focal length of the collimating lens 2, the collimating lens outgoing light beam 20 diverges. Therefore, as the distance between the collimating lens 2 and the light source 1 decreases, the light diameter of the collimating lens outgoing light beam 20 increases. When the distance between the collimating lens 2 and the light source 1 is larger than the focal length of the collimating lens 2, the collimating lens outgoing light beam 20 converges. Accordingly, as the distance between the collimating lens 2 and the light source 1 increases, the light diameter of the light emitted from the collimating lens 2 decreases.

  Note that the parallelism here means that the collimating lens outgoing light beam 20 when the distance between the collimating lens 2 and the light source 1 coincides with the focal length of the collimating lens 2 is parallel light, and is compared with this parallel light. This means how much the collimating lens outgoing light beam 20 is diverging or converging. As described above, the degree of divergence of the parallelism of the collimating lens output light beam 20 monotonously increases as the distance between the collimating lens 2 and the light source 1 decreases.

  As shown in FIG. 1, the photodetector 6 detects a part of a light beam (collimated lens output light beam 20) emitted from the collimator lens 2 and directed to the objective lens 3. Specifically, the photodetector 6 is a so-called photodiode, and includes a light receiving surface 6A and a light detection element (not shown).

  The light receiving surface 6A is disposed so that a part of the collimating lens outgoing light beam 20 is incident thereon. Further, the relative position of the light receiving surface 6A with the collimating lens outgoing light beam 20 is fixed. That is, in the present embodiment, the position of the light receiving surface 6A with respect to the collimating lens 2 is fixed in the direction perpendicular to the optical axis direction of the collimating lens 2. The light detection element detects the amount of light received at the light receiving surface 6A and outputs a signal 6i corresponding to the amount of received light to the control means 30. Here, the amount of received light means the irradiation area of light on the light receiving surface.

  A method for detecting the distance between the light source 1 and the collimating lens 2 using the photodetector 6 will be specifically described with reference to FIG.

  2A to 2C are plan views showing the relationship between the distance between the collimating lens 2 and the light source 1 and the spot shape of the collimating lens outgoing light beam 20 irradiated onto the light receiving surface 6A. 2A is a plan view showing a light receiving surface when the collimating lens outgoing light beam 20 becomes convergent light, FIG. 2B shows parallel light, and FIG. 2C shows divergent light. FIG. 2D is a graph showing the correlation between the position of the collimating lens 2 and the output signal from the photodetector 6. FIG. 2 (d) also shows the correspondence with FIGS. 2 (a) to 2 (c).

  As described above, the diameter of the collimating lens outgoing light beam 20 varies depending on the position of the collimating lens 2. Therefore, as shown in FIGS. 2A to 2C, the spot area of the collimating lens outgoing light beam 20 on the light receiving surface 6 </ b> A varies depending on the distance between the collimating lens 2 and the light source 1.

  In particular, as shown in FIG. 2B, the light receiving surface 6A of the present embodiment has an outer periphery of the cross-sectional shape of the light beam passing over the light receiving surface 6A when the collimating lens outgoing light beam 20 is parallel light. Are arranged as follows. Therefore, when the collimating lens is positioned at or around the position where the collimating lens outgoing light beam 20 is parallel, the area of the collimating lens outgoing light beam 20 incident on the light receiving surface 6A changes as the collimating lens 2 moves. As a result, the output value of the signal 6i from the photodetector 6 increases monotonously as the distance between the collimating lens 2 and the light source 1 decreases near the point b (the point where the collimating lens outgoing light beam 20 is parallel). (FIG. 2 (d)). As described above, the light receiving surface 6 </ b> A of the photodetector 6 is provided so that the detection result of the light detecting element changes monotonously according to the distance between the collimating lens 2 and the light source 1.

  At the time of spherical aberration correction, the collimating lens 2 usually creates a divergent light and convergent light state by moving the collimating lens 2 back and forth from this position around the time when the light beam from the collimating lens 2 is parallel light, and the protective layer 4a. Corresponding to the thickness of the lens (spherical aberration). Therefore, the fact that the position of the collimating lens 2 can be detected in the vicinity of the position where the collimating lens outgoing light beam 20 becomes parallel light can be widely applied from a recording medium having a thick protective layer 4a to a thin recording medium. So it is useful.

  Actually, the signal 6i does not change linearly as shown in the figure with respect to the parallel degree of the emitted light. The reason for this is that the semiconductor laser light emitted from the light source 1 has a Gaussian intensity distribution (the intensity at the center is the largest, and the intensity decreases toward the periphery). However, the signal 6i can be used as the position information of the collimating lens 2 because it changes monotonously depending on the parallelism of the collimating lens outgoing light beam 20.

  Further, if the distance between the collimating lens 2 and the light source 1 is remarkably large, the light beam 20 emitted from the collimating lens cannot be received by the photodetector 6, and if this distance is too small, the entire area of the light receiving surface 6A is collimated. The lens outgoing light beam 20 is irradiated, and the signal 6i does not change monotonously according to this interval. That is, the signal 6i only needs to change monotonously according to the distance between the collimating lens 2 and the light source 1 at least within the movable range of the collimating lens 2, and the distance between the collimating lens 2 and the light source 1 exceeds this range. There is no need to change monotonically depending on

  As described above, the position information of the collimating lens 2 can be obtained in real time by detecting the amount of light received by the light receiving surface 6A by the light detecting element. In particular, since the photodetector 6 is a non-divided photodetector in which the light receiving surface 6A is not divided, there is an advantage that it is inexpensive.

(1-3) Installation Position of Light-Receiving Surface It is preferable that the light-receiving surface 6A is disposed at a position where the optical pickup does not reduce light used for recording or reproducing information with respect to the recording medium 4. According to this, it is possible to realize an optical pickup having a high light utilization efficiency (ratio of irradiation light on the recording surface 4b with respect to the emitted light intensity of the light source 1).

  The position where the light receiving surface 6A is provided will be described in more detail.

  3A and 3B are cross-sectional views of the collimating lens outgoing light beam 20. FIG. In the optical pickup of the present embodiment, a tracking servo operation is performed as in a normal reproducing / recording apparatus. In other words, in order to cause the light spot to follow the desired information track on the recording medium 4, the objective lens 3 is moved in the radial direction of the recording medium 4 (radial direction in FIGS. 1 and 3B) by a driving mechanism (not shown). Driven. Therefore, as shown in FIG. 3A, the diameter of the collimating lens outgoing light beam 20 is larger than the diameter of the objective lens 3 so that the outgoing light from the collimating lens 2 enters the objective lens 3 even if the objective lens 3 moves. Is also set larger. That is, the collimating lens outgoing light beam 20 includes light 20a that does not enter the objective lens 3 at the outer edge portion in the cross section thereof. This light 20 a is not used for recording or reproducing information on the recording medium 4.

  The light receiving surface 6A is preferably arranged so as to receive the light 20a. By doing so, the parallelism of the collimating lens outgoing light beam 20 can be detected without reducing the light used for recording or reproducing information on the recording medium 4.

  As described above, the objective lens 3 is driven in the radial direction of the recording medium 4 during the tracking servo operation. Accordingly, in the cross section of the light beam 20 emitted from the collimator lens 20, the light 20 b on the outer edge side of the objective lens 3 in the tangential direction of the recording medium 4 (the portion indicated by the oblique lines in FIG. 3B) is used for recording and reproducing information. Not used. Therefore, the light receiving surface 6A is more preferably arranged to receive the light 20b. That is, it is preferable that the light receiving surface 6 </ b> A is disposed on the outer edge side of the collimating lens outgoing light beam 20 with respect to the objective lens 3 in the tangential direction of the recording medium 4.

  According to the said structure, there exists an advantage that the freedom degree of the position of 6 A of light-receiving surfaces increases more. That is, the accuracy required for adjusting the position of the light receiving surface 6A can be reduced.

In particular, as shown in FIG. 4, in general, the photodetector 6 has a light receiving surface 6A disposed inside the exterior package 6p. Therefore, in order to irradiate the collimator lens outgoing beam 20 on the light receiving surface. 6A, exterior packaging 6p of the photodetector 6 will be entering the inside of the light beam from the light-receiving surface 6A. Therefore, disposing the light receiving surface 6A at a position as shown in FIG. 3B is useful for avoiding injuries.

(1-4) Collimating Lens Position Adjustment As described in (1-2) above, the output signal 6i of the photodetector 6 becomes the position signal of the collimating lens 2 in the present embodiment. The signal 6i from the photodetector 6 is input to the drive means control unit 30b through the low pass filter 30a. Drive means control unit 30 b controls the driving unit 7 based on the signal 6i. This control, drive means 7 drives the co re formate lens 2 to adjust the position of the collimator lens 2.

  Since the recording medium 4 includes the protective layer 4a, spherical aberration due to a thickness error of the protective layer 4a occurs when information is recorded on or reproduced from the recording medium 4. For this reason, the optical pickup includes a servo system for correcting spherical aberration. This servo system detects the amplitude of the reproduction signal obtained from the recording medium 4 while moving the collimating lens 2 by the driving means 7, and adjusts the position of the collimating lens 2 to a position where the amplitude of the reproduction signal is maximized. Is.

  The optical pickup according to the present embodiment can adjust the position of the collimating lens 2 to a predetermined start position before performing the spherical aberration correction operation. A method for adjusting the collimating lens position will be described.

  First, when the optical pickup is turned on and the optical pickup starts up, emission of light from the light source 1 is started. When light is emitted from the light source 1, the position information of the collimating lens 2, that is, the 6i signal is output from the photodetector 6 to the control means 30 as described in (1-3) above.

  The control means 30 includes a storage unit (not shown), and the storage unit stores in advance the output value of the 6i signal when the collimating lens 2 is at a predetermined position. Hereinafter, this position is referred to as a start position, and this value is referred to as a reference value. The drive means control section 30b controls the drive means 7 so that the output value of 6i approaches this reference value, and stops the operation of the drive means 7 when these two values match. In this way, the collimating lens 2 is fixed at the start position.

  With the collimating lens 2 fixed at the start position, the spherical aberration correction operation is started. That is, the collimating lens 2 is moved from this starting position, and the collimating lens 2 is fixed at the position where the amplitude of the reproduction signal is maximized as described above.

  The start position described above is preferably an average position of the collimating lens after spherical aberration correction. That is, it is preferable that the collimating lens is in an optimum position when the thickness of the protective layer 4a is a standard center value or when the protective layer 4a has an average protective layer thickness of a disk distributed on the market.

  Thus, according to the optical pickup of the present embodiment, the position of the collimating lens can always be grasped. That is, the position of the collimating lens when the optical pickup is turned on can be detected. Therefore, before starting the spherical aberration correction operation after the power is turned on, the spherical aberration correction operation can be started without once moving the collimating lens to the end of the movable range.

  More specifically, according to the optical pickup of the present embodiment, the movement of the collimating lens in the spherical aberration correction can be started from a position very close to the position after the spherical aberration correction. That is, the moving distance of the collimating lens when correcting spherical aberration can be kept very small. Therefore, the startup time of the optical pickup can be shortened.

  Since the position of the collimating lens cannot be detected in real time with the conventional optical pickup, the starting position is the average position of the collimating lens after correcting the collimating lens spherical aberration as in the optical pickup of the present embodiment. It cannot be.

  Further, according to the above configuration, since the position of the collimating lens 2 can be detected from the signal output of the photodetector 6, a means such as a photo interrupter for detecting the end of the collimating lens movable range becomes unnecessary.

  The control means 30 is a computer, and the drive means control unit 30b may be realized by hardware, or may be realized by software by executing a predetermined program on the control means 30. The same applies to the storage unit.

(1-5) Low-pass filter Although a semiconductor laser can be suitably used as the light source 1, the amount of light emitted from the semiconductor laser becomes unstable due to the return light from the recording medium 4. Control is performed to obtain optical output.

  In general, fluctuations in light output due to return light include high frequency components. Therefore, it is effective to provide a low-pass filter (LPF) 30a that removes high-frequency components before the drive means control unit 30b so as to prevent erroneous collimation position control due to output fluctuation of the light source. The adjustment of the collimating lens position only needs to be normally followed in the order of milliseconds, so the LPF band is set to about several KHz. As a result, stable collimating lens position control that is not affected by laser noise is possible.

(1-6) Light Source Control The light source monitor photodetector 8 shown in FIG. 1 detects the amount of light emitted from the light source 1. The detection result of the photodetector 8 is input to the APC circuit 30d, and the APC circuit 30d controls the light source 1 so that the detection result is constant. By doing so, the amount of light emitted from the light source 1 can be kept stable.

  However, even if the amount of light emitted from the light source 1 is constant, the amount of light incident on the recording medium 4 varies depending on the distance between the collimating lens 2 and the light source 1. This point will be described with reference to FIG.

  FIG. 5 is a front view showing the relationship between the distance between the collimating lens 2 and the light source 1 and the amount of light incident on the objective lens 3. FIG. 5B shows a case where the collimating lens outgoing light beam 20 is parallel light, and FIG. 5A shows a case where the collimating lens outgoing light beam 20 diverges, that is, the distance between the collimating lens 2 and the light source 1 is larger than in FIG. When the collimating lens output light beam 20 converges, (c) shows the main configuration of the optical pickup when the distance between the collimating lens 2 and the light source 1 is larger than that in (b).

  As shown in FIGS. 5A and 5B, when the amount of light emitted from the light source 1 is constant, the amount of light incident on the objective lens 3 decreases as the distance between the collimating lens 2 and the light source 1 decreases. . That is, as the distance between the collimating lens 2 and the light source 1 decreases, the amount of light incident on the recording medium 4 decreases.

  Therefore, in the optical pickup of the present embodiment, a light source monitor signal output from the photodetector 8 according to the amount of light emitted from the light source 1 is input to the APC circuit 30d via the gain adjustment circuit 30c. Yes. The signal 6i from the photodetector 6 is also input to the gain adjustment circuit 30c. The gain adjustment circuit 30c performs gain adjustment on the light source monitor signal based on the signal 6i from the photodetector 6 (FIG. 1).

  That is, the gain adjustment circuit 30c adjusts the circuit gain based on the signal 6i so that the light source monitor signal input to the APC circuit 30d decreases as the distance between the collimating lens 2 and the light source 1 decreases. When the distance between the collimating lens 2 and the light source 1 is small, the gain is decreased to reduce the input signal to the APC circuit 30d. Therefore, the APC circuit 30d controls the light source 1 so as to emit larger light. In this way, it is possible to correct a decrease in the amount of incident light on the recording medium 4 due to the divergence of the collimating lens outgoing light beam 20.

  Conversely, when the collimating lens 2 is far from the light source 1 (FIG. 5C), the gain can be increased to increase the input signal to the APC circuit 30d. The APC circuit 30d works so as to emit a smaller light output from the light source 1, and can correct an increase in the amount of incident light on the recording medium 4 due to the convergence of the collimating lens emitted light beam 20. That is, the gain adjustment circuit 30c and the APC circuit 30d function as light source control means.

  With the configuration shown in FIG. 1, the amount of light incident on the recording medium 4 can be stabilized by the above operation even if the position of the collimating lens 2 changes.

[Embodiment 2]
(2-1) Outline of Configuration of Optical Pickup An optical pickup according to the present embodiment will be described with reference to FIG. In addition, about the member which has a function similar to the optical pick-up of FIG. 1, while attaching | subjecting a same sign, the description is abbreviate | omitted.

  As shown in FIG. 6, the optical pickup according to the present embodiment includes an optical system 42 and a control unit 32. The optical system 42 includes a beam splitter 5 between the collimating lens 2 and the objective lens 3, a photodetector 60 instead of the photodetector 6, and a light source monitoring photodetector 8. The configuration is the same as that of the optical system 40 of the first embodiment. In addition, not only a beam splitter but the reflective optical element conventionally used for an optical pick-up can be used suitably.

  The control unit 32 has the same configuration as the control unit 30 of the first embodiment except that it includes a calculation unit 32e (position information calculation unit) and an addition unit 32f. However, in Embodiments 2 to 9, the members given the same alphabet in the control unit have the same functions. Therefore, description about these members may be omitted.

  The beam splitter 5 splits the collimating lens outgoing light beam 20 into a first light beam 21 and a second light beam 22. The first light beam 21 is a light beam incident on the recording medium 4, and the second light beam 22 is a light beam incident on the light receiving surface 60 </ b> A of the photodetector 60.

(2-2) Position Information of Collimating Lens 2 As the photodetector 60, the photodetector 6 of the first embodiment can be used, but in this embodiment, the light receiving surface 60A of the photodetector 60 is It is assumed that the area is divided into two areas 62a and 62b. Below, the acquisition method of the positional information of the collimating lens 2 using the photodetector 60 of this Embodiment is demonstrated based on FIG.

Photodetector 6 0 comprises a light receiving surface 60A which is divided into two regions 62a · 62b, and a photodetector element which outputs a signal corresponding to the received light amount of each light-receiving surface to the control unit 32 (not shown) . As shown in FIG. 7, the dividing line that divides the regions 62a and 62b is circular. That is, the region 62a is circular, and the region 62b is provided so as to surround the outer periphery of the region 62a.

  The arithmetic unit 32e described above is a subtracter, and the difference signal is obtained by calculating (62i−62j) from the signal 62i from the light detecting element corresponding to the region 62a and the signal 62j from the light detecting element corresponding to the region 62b. Is calculated. As will be described below, this difference signal is position information of the collimating lens 2.

  FIGS. 7A to 7C are plan views showing the relationship between the position of the collimating lens 2 and the spot of the second light beam 22 on the light receiving surface 60A of the present embodiment, and FIG. 4 is a graph showing the correlation between the position of the collimating lens 2 and the difference signal obtained from the calculation unit 32e. FIG. 7D also shows the correspondence with FIGS. 7A to 7C.

The position (FIG. 7B) where the light diameter of the second light beam 22 matches the light diameter of the region 62a is hereinafter referred to as position A. As already described, the larger the distance between the collimating lens 2 and the light source 1, the smaller the light diameter of the collimating lens outgoing light beam 20 becomes. Therefore, as shown in FIG. 7 (a), when the collimating lens 2 from the position A is the distance from the light source 1, the diameter of the second light flux 22 on the light receiving surface of the photodetector 6 0 is smaller than the diameter of the region 62a . That is, the outgoing light does not enter the region 62b. Accordingly, at this time, the output value of the signal (62i-62j) is equal to the signal output value at the position A (a in FIG. 7D).

  On the other hand, as shown in FIG. 7C, when the collimating lens 2 approaches the light source 1 from the position A, the diameter of the second light beam 22 on the light receiving surface becomes larger than the diameter of the region 62a. That is, light enters both the regions 62a and 62b, and the amount of light received in the region 62b increases as the collimating lens 2 approaches the light source 1. Therefore, the signal (62i-62j) becomes smaller as the collimating lens 2 approaches the light source 1 with the position A as a boundary (c in FIG. 7D).

Actually, the signal (62i-62j) does not change linearly with respect to the degree of parallelism of the collimating lens outgoing light beam 20. For this reason, in addition to the reason described in (1-2) above, the spot of the second light beam 22 on the light receiving surface is circular, and the region 62a and 62b are also irradiated across the circular boundary line. Therefore, it is mentioned that the light irradiation area in the region 6 2 b does not change linearly with respect to the parallel degree of the collimating lens outgoing light beam 20. However, since the signal (62i-62j) monotonously changes as the collimating lens output light beam 20 becomes diverging light at the position A, the position of the collimating lens 2 is detected at a position closer to the light source 1 than the position A. be able to.

(2-3) Position Adjustment of Collimating Lens Position adjustment of the collimating lens 2 in the optical pickup of the present embodiment is the same as that of Embodiment 1 except that the signal (62i-62j) is used instead of the signal 6i. . The arithmetic unit 32e may be realized by hardware, or may be realized by software by executing a predetermined program on the control unit 32.

As described above, in this embodiment, functions as a parallelism detection means photodetector 6 0 and computing unit 32e detects the parallelism of the collimating lens 2.

(2-4) Low-pass filter Since the signal (62i-62j) calculated as the position information of the collimating lens in this embodiment is a difference signal, the in-phase component of the light output fluctuation of the light source 1 is theoretically determined by differential calculation. There is an advantage that it can be removed. However, when the received light amounts in the regions 62a and 62b are equal, the output fluctuation component of the light source, which is in-phase noise, can be removed by this differential calculation. However, when the received light amounts are not equal, the output fluctuation component of the light source is It remains in the signal (62i-62j). For this reason, it is effective to provide a low-pass filter (LPF) 32a that removes high-frequency components before the moving means control unit 32b so as to prevent erroneous collimated position control due to output fluctuations of the light source 1 (FIG. 6). Details of the low-pass filter have been described in (1-5) above, and will not be described.

(2-5) Light source control In the present embodiment, the photodetector 60 also serves as a photodetector for light source monitoring.

As shown in FIG. 7 (a) ~ (b) , since all of the second light flux 22 is incident on the light receiving surface, the amount of light received by the optical detector 6 0 monotonically increased according to the amount of light emitted from the light source 1 To do. That is, (62i + 62j) is constant regardless of the distance between the light source 1 and the collimating lens 2.

  Therefore, a signal (62i + 62j) corresponding to the amount of light emitted from the light source 1 can be obtained by performing the calculation of (62i + 62j) by the adder 32f (position information calculation unit). Based on this signal, the APC circuit The light source 1 can be controlled by 32d. As a result, the cost of the optical pickup can be reduced.

[Embodiment 3]
The optical pickup according to the present embodiment has the same configuration as that of the optical pickup according to the second embodiment (FIG. 6) except that the control means 33 is provided instead of the control means 32 with reference to FIG. The control means 33 includes a gain adjustment circuit 33 c in addition to the members of the control means 32.

As described in (2-5) above, the signal (62i + 62j) obtained in the adder 33f increases monotonously according to the amount of light emitted from the light source 1. Therefore, the optical pickup according to the present embodiment includes the gain adjustment circuit 33c and the gain adjustment circuit 33c based on the calculation result (emitted light amount information) of the adder 33f and the calculation result (62i-62j, position information) of the calculation unit 33e. The light source 1 is controlled by the APC circuit 33d. The control of the light source 1 by the gain adjustment circuit 33c and the APC circuit 33d is the same as described in the above section (1-6). That is, the optical pickup of the present embodiment, except that the light detectors 6 0 and adder 33f in place of the optical detector 8, also controls the light source 1 by the above (1-6) the same operation as column I can say that.

[Embodiment 4]
The optical pickup of the present embodiment has the same configuration as that of the optical pickup of the third embodiment, except that the light receiving surface 60A of the photodetector 60 has a configuration as shown in FIG.

  FIGS. 9A to 9C are plan views showing the relationship between the distance between the collimating lens 2 and the light source 1 and the spot shape of the second light beam 22 on the light receiving surface. FIG. 9A is a plan view showing a light receiving surface when the collimating lens outgoing light beam 20 becomes convergent light, (b) becomes parallel light, and (c) shows divergent light. FIG. 9D is a graph showing the correlation between the position of the collimating lens 2 and the calculation result (62i-62j) of the calculation unit 33e. FIG. 9D also shows the correspondence with FIGS. 9A to 9C.

  In the present embodiment, the light emitted from the collimating lens 2 is always incident on the regions 62a and 62b regardless of the position of the collimating lens 2. Therefore, the signal (62i-62j) simply decreases as the distance between the collimating lens 2 and the light source 1 decreases (FIG. 9 (d)). That is, regardless of the position of the collimating lens 2, the (62i-62j) signal changes monotonously according to the distance between the collimating lens 2 and the light source 1. Therefore, according to the present embodiment, position information of the collimating lens 2 in a wide range can be obtained regardless of the position of the collimating lens 2. Note that “regardless of the position of the collimating lens 2” means “regardless of the position of the collimating lens 2 within the movable range” as described above.

  As in the present embodiment, within the movable range of the collimating lens 2, the collimating lens 2 and the light receiving surface 60 are connected to each other so that the second light beam 22 is always incident on both the regions 62a and 62b. What is necessary is just to arrange | position to such a positional relationship. That is, the light receiving surface 60A is arranged so that the second light beam 22 is incident on both the regions 62a and 62b when the collimating lens 2 is at the end of its movable range, that is, the position farthest from the light source 1. That's fine.

  In addition to this arrangement, when the collimating lens outgoing light beam 20 is parallel light, the light receiving surface 60A is arranged so that the second light beam 22 is incident on both the regions 62a and 62a across the dividing line. The configuration (FIG. 9B) is sufficient. According to this configuration, the position of the collimating lens 2 can be detected at a position where the collimating lens outgoing light beam 20 is parallel light and in the vicinity of this position.

  As already described, at the time of spherical aberration correction, the collimating lens 2 usually has a divergent light and a convergent light state by moving the collimating lens 2 back and forth from this position around the time when the light beam from the collimating lens 2 is parallel light. And is made to correspond to the thickness of the protective layer 4a (spherical aberration). Therefore, the fact that the position of the collimating lens 2 can be detected in the vicinity of the position where the collimating lens outgoing light beam 20 becomes parallel light can be widely applied from a recording medium having a thick protective layer 4a to a thin recording medium. So it is useful.

  Further, since the signal (62i + 62j) indicating the amount of light received by the second light beam 22 on the light receiving surface is constant within the movable range of the collimating lens 2, this signal can be used for controlling the light source 1 in the third embodiment. As stated.

[Embodiment 5]
The optical pickup of the present embodiment has the same configuration as that of the fourth embodiment except that the light receiving surface 60A is divided into regions 65a and 65b by a linear dividing line (FIG. 10).

  FIGS. 10A to 10C are plan views showing the relationship between the distance between the collimating lens 2 and the light source 1 and the spot shape of the second light beam 22 on the light receiving surface. 10A is a plan view showing a light receiving surface when the collimating lens outgoing light beam 20 becomes convergent light, FIG. 10B shows parallel light, and FIG. 10C shows divergent light. FIG. 10D is a graph showing the correlation between the position of the collimating lens 2 and the calculation result (65i-65j) of the calculation unit 33e. FIG. 10D also shows the correspondence with FIGS. 10A to 10C.

  According to the configuration of the present embodiment, as shown in FIGS. 10A to 10C, when the collimating lens outgoing light beam 20 is parallel light, the first and second regions 65 a and 65 b are crossed across the dividing line. The two light beams 22 are incident. Therefore, the position of the collimating lens 2 can be detected at and near the position where the collimating lens outgoing light beam 20 is parallel light, which is useful.

  In addition, since the signal (65i + 65j) indicating the amount of light received by the second light beam 22 on the light receiving surface is constant within the movable range of the collimating lens 2, this signal can be used for controlling the light source 1 in the third embodiment. As stated.

[Embodiment 6]
The optical pickup of the present embodiment has the same configuration as that of the third embodiment except that the light receiving surface 60A uses a light receiving surface that is divided into three regions 66a, 66b, and 66c by a linear dividing line. (FIG. 11).

  FIGS. 11A to 11C are plan views showing the relationship between the distance between the collimating lens 2 and the light source 1 and the spot shape of the second light beam 22 on the light receiving surface. FIG. 11A is a plan view showing a light receiving surface when the collimating lens outgoing light beam 20 becomes convergent light, (b) becomes parallel light, and (c) shows divergent light. FIG. 11D is a graph showing the correlation between the position of the collimating lens 2 and the calculation result {66j− (66i + 66k)} of the calculation unit 33e. FIG. 11D also shows the correspondence with FIGS. 11A to 11C.

As shown in FIG. 11A , the light receiving surface is divided into three regions 66a, 66b, and 66c by two straight lines parallel to each other, and the regions 66a and 66c sandwich the region 66b in the Y-axis direction. Is provided. That is, the dividing line between the region 66a and the region 66b and the dividing line between the region 66b and the region 66b are parallel to each other.

The calculation unit 33e (FIG. 8) acquires the position information of the collimating lens 2 based on the output signals 6 6 i, 6 6 j, and 6 6 k from the light detection elements corresponding to the regions 66a, 66b, and 66c, respectively. To do. The position information in this case is a position signal obtained by {66j− (66i + 66k)}.

In addition, the second light beam 22 is always incident on the regions 66a to 66c within the movable range of the collimator lens 2 (FIGS. 11A to 11C). Therefore, as shown in FIG. 11 (d), depending on the distance between the collimator lens 2 and the light source 1, the position signal of {6 6 j- (6 6 i + 6 6 k)} changes monotonically. That is, this position signal changes monotonously according to the position of the collimating lens 2.

  In the present embodiment, as shown in FIG. 11A, regions 66a and 66c are provided in the Y-axis direction with the region 66b interposed therebetween. According to this configuration, even if the second light beam 22 moves in the Y-axis direction, the calculation result of {66j− (66i + 66k)} is hardly affected. Therefore, for example, even if the position of the second light beam 22 on the light receiving surface is shifted in the Y-axis direction due to the shift of the position of the photodetector 60 (FIG. 8), the optical pickup according to the present embodiment is stable. A collimating lens position signal can be obtained.

  Further, in the present embodiment, by providing the three regions 66a, 66b, and 66c, it is possible to detect the spread of the second light beam 22 in both the positive and negative directions of the Y axis (that is, the spread of the collimator lens emitted light beam 20). . Therefore, it is possible to detect the change in the diameter of the collimating lens outgoing light beam 20 (that is, the change in the position of the collimating lens) with higher sensitivity than when using the light receiving surface divided into two regions by the linear dividing line. There is an effect.

The magnitude of the signal {6 6 j− (6 6 i + 6 6 k)} does not actually change linearly but changes monotonously with respect to the parallel degree of the collimating lens output light 20. Therefore, as described above, the position of the collimating lens can be controlled according to the magnitude of the position signal.

Further, since the signal (6 6 i + 6 6 j + 6 6 k) indicating the amount of light received by the second light beam 22 on the light receiving surface is constant within the movable range of the collimator lens 2, this signal can be used for controlling the light source 1. As already described in the third embodiment.

[Embodiment 7]
FIG. 12 shows the main configuration of the optical system of the optical pickup according to the present embodiment.

The optical pickup according to the present embodiment has the same configuration as that of the third embodiment except that an optical system 47 shown in FIG. That is, except that a condenser lens 10 is provided between the beam splitter 5 and the photodetector 6 0 has the same configuration as the optical system 42.

That is, this optical pickup, the second light flux 22 from the beam splitter 5, and is converged on the light receiving surface of the photodetector 6 0 through the condenser lens 10. Thus, as the photodetector 6 0, it can be used small light detector of the light receiving area. In general, the smaller the light receiving area, the faster the response of the photodetector. Therefore, the optical pickup of the present embodiment can detect the position of the collimating lens 2 and the intensity of the emitted light from the light source 1 at high speed. There is.

[Embodiment 8]
The optical pickup according to the present embodiment has the same configuration as that of the third embodiment except that an optical system 48 shown in FIG. 13 is provided instead of the optical system 42. That is, the same configuration as that of the third embodiment is provided except that a diffraction grating 50 is provided instead of the beam splitter 5. For step or the like from the second light flux 22 incident on the light detector 6 0 obtaining positional information of the collimating lens 2, as already mentioned.

In FIG. 13, it is provided with the diffraction grating child 50 immediately after the collimating lens 2, if between the light source 1 and the objective lens 3, may be arranged in any way.

Advantages of the optical pickup of the present embodiment, it is possible to use an inexpensive diffraction grating children produced by using a resin molding as the branch unit, a cost can be reduced. A hologram element can also be used as the diffraction grating.

[Embodiment 9]
The optical pickup according to the present embodiment includes an optical system 49 shown in FIG. 14 instead of the optical system 42, and the third embodiment is the same as the optical pickup 49 except that the light receiving surface 60A is divided into four regions as shown in FIG. The same configuration as that of the optical pickup is provided.

FIG. 14 is a block diagram showing a main configuration of the optical pickup. Further, FIG. 15 (a) ~ (c) is a distance between the collimating lens 2 and the light source 1, the relationship between the output light spot shape from the collimating lens 2 and is irradiated on the light receiving surface of the photodetector 6 0 FIG.

  FIG. 15A shows a light receiving surface when the emitted light from the collimating lens 2 becomes convergent light, (b) shows parallel light, and (c) shows a light receiving surface when the emitted light becomes divergent light. FIG. FIG. 15D is a graph showing the correlation between the position of the collimating lens 2 and the position signal {(69i + 69k) − (69j + 69l)} calculated by the calculation unit 33e (see FIG. 8). FIG. 15D also shows the correspondence with FIGS. 15A to 15C.

  The astigmatism generation means 11 generates astigmatism light by generating astigmatism in the second light flux from the beam splitter 5, and guides the astigmatism light to the photodetector 60.

  As the astigmatism generation means 11, for example, a lens conventionally known as astigmatism generation means such as a toric lens or a cylindrical lens can be suitably used.

  The configuration of the light receiving surface 60A and the collimator lens position information in the present embodiment will be described with reference to FIG.

  In the present embodiment, as shown in FIG. 15A, the light receiving surface is divided into four regions 69a to 69d by two orthogonal dividing lines. The light receiving surface is disposed at a position where the collimating lens output light spot on the light receiving surface is a minimum circle of confusion generated by the astigmatism generation unit 11 when the collimated lens output light is parallel light. Further, the direction of the dividing line makes an angle of approximately 45 degrees with the bus line of the astigmatism generating means 11.

  As a result, as shown in FIGS. 15A to 15C, the spot shape on the light receiving surface changes according to the parallelism of the light emitted from the collimator lens. That is, when the collimating lens exiting light is parallel light, the collimating lens exiting light spot is circular (FIG. 15B), and when the collimating lens exiting light is convergent light or diverging light, it is elliptical (FIG. 15 (a), (c)).

  As in the third embodiment, the optical elements corresponding to the respective regions 69a, 69b, 69c, and 69d on the light receiving surface output signals 69i, 69j, 69k, and 69l of output values corresponding to the amounts of light received in the respective regions. It outputs to the calculating part 33e. The calculation unit 33e calculates a difference signal by calculating the difference between the diagonal components in each region, that is, the calculation of {(69i + 69k) − (69j + 69l)}. As shown in FIG. 15D, in the present embodiment, the value of the difference signal simply increases as the distance between the collimating lens 2 and the light source 1 decreases. That is, the difference signal is a position signal of the collimating lens 2.

In the present embodiment, when the collimating lens outgoing light beam 20 is parallel light, the collimating lens outgoing light is incident on all of the regions 69a to 69d. Can be obtained. Further, in this embodiment, the position of the collimator lens outgoing light spot on the optical detector 6 0, even if displaced to either X · Y-axis direction, it is possible to obtain a stable collimator lens position signal.

  Note that the difference signal does not actually change linearly as shown in FIG. 15D with respect to the parallel degree of the emitted light. However, as described in the first embodiment, the collimating lens can be monotonously changed depending on the degree of parallelism of the collimating lens, and the position of the collimating lens can be controlled by using the difference signal as position information of the collimating lens 2.

  Further, as described in the first embodiment, the adder 33f can calculate a sum signal representing the total light amount incident on the photodetector 60 by performing the calculation (69i + 69j + 69k + 69l). The optical pickup of the present embodiment can also control the light source 1 using this sum signal.

  The photodetector 60 in the present embodiment is not limited to the configuration including the four-divided light receiving surface as described above as long as the astigmatism generated by the astigmatism generating unit 11 can be detected. .

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The optical pickup of the present invention can be suitably used as a recording / reproducing apparatus for recording and / or reproducing information with respect to an optical disc.

It is a block diagram which shows the principal part structure of the optical pick-up which concerns on embodiment of this invention. It is drawing which shows the position detection principle of the collimating lens 2 in this Embodiment, (a) is when collimating lens output light beam 20 becomes convergent light, (b) is parallel light, (c) is It is a top view which shows the light-receiving surface when it becomes a diverging light. Further, (d) is a graph showing the correlation between the position of the collimating lens 2 and the signal 6i. It is a cross-sectional view showing the collimating lens outgoing light beam 20 and the installation position of the light receiving surface 6A. It is a front view which shows the principal part structure of an optical pick-up when 6 A of light-receiving surfaces are arrange | positioned in the exterior package 6p. It is a front view which shows the space | interval of the collimating lens 2 and the light source 1, and the parallelism of the collimating lens output light beam 20, When (a) becomes collimated light, the collimating lens output light beam 20 becomes convergent light. (C) indicates when diverging light is obtained. It is a block diagram which shows the principal part structure of the optical pick-up in other embodiment of this invention. It is drawing which shows the position detection principle of the collimating lens 2 in this Embodiment, (a) is when collimating lens output light beam 20 becomes convergent light, (b) is parallel light, (c) is It is a top view which shows the light-receiving surface when it becomes a diverging light. Further, (d) is a graph showing the correlation between the position of the collimating lens 2 and the signal (62i-62j). It is a block diagram which shows the principal part structure of the optical pick-up in further another embodiment of this invention. It is drawing which shows the position detection principle of the collimating lens 2 in further another embodiment of this invention, (a) is when collimating lens output light beam 20 becomes convergent light, and (b) is parallel light. (C) is a top view which shows the light-receiving surface when it becomes a diverging light. Further, (d) is a graph showing the correlation between the position of the collimating lens 2 and the signal (62i-62j). It is drawing which shows the position detection principle of the collimating lens 2 in further another embodiment of this invention, (a) is when collimating lens output light beam 20 becomes convergent light, and (b) is parallel light. (C) is a top view which shows the light-receiving surface when it becomes a diverging light. Further, (d) is a graph showing the correlation between the position of the collimating lens 2 and the signal (65i-65j). It is drawing which shows the position detection principle of the collimating lens 2 in further another embodiment of this invention, (a) is when collimating lens output light beam 20 becomes convergent light, and (b) is parallel light. (C) is a top view which shows the light-receiving surface when it becomes a diverging light. Further, (d) is a graph showing the correlation between the position of the collimating lens 2 and the signal {66i− (66j−66k)}. It is a front view which shows the principal part structure of the optical system in other embodiment of this invention. It is a front view which shows the principal part structure of the optical system in other embodiment of this invention. It is a front view which shows the principal part structure of the optical system in other embodiment of this invention. It is drawing which shows the position detection principle of the collimating lens 2 in this Embodiment, (a) is when collimating lens output light beam 20 becomes convergent light, (b) is parallel light, (c) is It is a top view which shows the light-receiving surface when it becomes a diverging light. Further, (d) is a graph showing a correlation between the position of the collimating lens 2 and the signal {(69i + 69k) − (69j + 66l)}. It is drawing which shows the principal part structure of the conventional optical pick-up.

DESCRIPTION OF SYMBOLS 1 Light source 2 Collimating lens 3 Objective lens 4 Recording medium 4a Protective layer 4b Recording surface 6 Photodetector (light receiving surface, received light amount detection unit, detection element)
6A Light-receiving surface 30, 32, 33 Control unit 30, 32, 33a Low-pass filter 30, 32, 33b Drive unit control unit (interval changing unit)
30, 33c Gain adjustment circuit (light source control means)
30, 32, 33d APC circuit (light source control means)
32, 33e Calculation unit (position information calculation unit)
32, 33f Adder

Claims (5)

An optical pickup comprising a light source and a lens group including a collimator lens, and guiding light emitted from the light source to a recording medium by the lens group,
The collimating lens can move in the optical axis direction to correct spherical aberration,
A light receiving surface that receives the light beam emitted from the collimator lens, and a light receiving amount detection unit that detects the amount of light received on the light receiving surface,
The light receiving surface is provided so that the detection result of the light receiving amount detection unit changes monotonously according to the interval between the collimating lens and the light source,
The light receiving surface is provided in the optical path of the light beam from the collimating lens toward the recording medium,
The lens group includes an objective lens, and the diameter of the objective lens is set smaller than the diameter of the collimating lens exit beam,
2. The optical pickup according to claim 1, wherein the light receiving surface is disposed on the outer edge side of the cross-sectional shape of the light beam directed from the collimator lens to the recording medium rather than the objective lens . Provided with interval changing means for changing the interval between the collimating lens and the light source,
The optical pickup according to claim 1, wherein the interval changing unit changes the interval so that at least a detection result of the received light amount detection unit becomes a predetermined value . 3. The optical pickup according to claim 2 , wherein the detection result of the received light amount detection unit is input to the interval changing means via a low pass filter . A light source control means for controlling the amount of light emitted from the light source;
The light source control means controls the amount of emitted light based on at least the detection result of the received light amount detection unit so that the amount of emitted light is relatively increased as the distance between the collimating lens and the light source is reduced. The optical pickup according to claim 1 . The lens group includes at least an objective lens that is driven in the radial direction of the recording medium, and the diameter of the objective lens is set to be smaller than the diameter of the collimating lens exit beam,
2. The light according to claim 1, wherein the light receiving surface is disposed on an outer edge side of a cross-sectional shape of a light beam directed from the collimator lens toward the recording medium in the tangential direction of the recording medium. pick up.

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