JP2009181679A - Optical module, pickup device, and recording disk playback device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform reading capable of suppressing, as much as possible, the influence of a light receiving part on both of tracking control and focusing control, the light receiving part being divided into three areas for the focus control and the tracking control to access recorded information in a recording disk. <P>SOLUTION: The light receiving part of the optical module for recording disk reading includes: a focus-adjusting light receiving part for receiving a part of return light in a focus-adjusting area demarcated over a predetermined reference line parallel to the tangential line of a track to which the optical module is corresponding when the optical module is located in a predetermined position between the innermost peripheral part and outermost peripheral part; and a track-adjusting light receiving part for receiving a part of the return light in a track-adjusting area demarcated into first and second track-adjusting areas sandwiching the predetermined reference line, which does not interfere in the focus-adjusting area, in the return light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical module that adjusts light emitted from a light source to read a record in a recording disk that is an information recording medium. The present invention also relates to a pickup device including the optical module and a recording disk reproducing device.

  In order to support reading of a plurality of types of recording disks, a recording disk reproducing apparatus having a pickup device having two sets of reading light sources and objective lenses is used. In such a reproducing apparatus, one objective lens is installed on the radial line of the recording disk, but the other objective lens is arranged so as to be out of the radius. Here, in order to read the recording information in the recording disk, it is necessary to accurately irradiate the track in the recording disk with the light emitted from the light source. Therefore, a push-pull method or an advanced push-pull method is used in which return light returned from the recording disk is divided into right and left by a reference line along the tangent line of the track, and tracking is performed by using the difference.

  A tracking technique using this advanced push-pull method is disclosed in Patent Document 1. In the advanced push-pull method, the light receiving portion of the return light is divided into six as shown in FIG. 4 of Patent Document 1, and the light reception signals of the respective divided regions are added and subtracted, thereby adjusting the tracking. Here, in this technique, when the arrangement of the objective lens is deviated from the radial line of the recording disk as described above, the tracking at the time of lens shift generated by the objective lens following the eccentricity of the recording disk is improved. Therefore, among the dividing lines that divide the light receiving portion, the inclination of the dividing line that extends in the tangential direction of the track and divides the light receiving portion into two is adjusted (see FIG. 6 in Patent Document 1).

Further, in Patent Document 1, a technique is disclosed in which the light receiving portion is roughly divided into two parts, and finally divided into six parts to cope with the advanced push-pull method. However, Patent Document 2 discloses a different light receiving part division. The law is disclosed. As shown in FIG. 1 of Patent Document 2, the light receiving unit is divided into three, and focus adjustment and tracking adjustment to the recording disk are performed based on the light reception signals in the respective divided regions.
JP 2006-31913 A Japanese Patent Laid-Open No. 9-161282

  In the above prior art, when performing tracking control of the emitted light by the push-pull method using the light receiving portion divided into two by the reference line parallel to the track tangent, the lens shift caused by the tracking of the objective lens to the recording disk It is claimed that tracking control by the advanced push-pull method is useful in order to suppress the influence of the above. In addition, the influence on the tracking control that occurs when the pickup device is transported at a position deviated from the radial line of the recording disk, that is, the return light including the tracking component used in the advanced push-pull method and the tracking component are not included. In order to alleviate the decrease in the tracking performance in tracking control caused by the return light not being received by the light receiving unit set in advance in the advanced push-pull method and being received by an unscheduled light receiving unit, the light receiving unit is divided. A predetermined line is adopted as the line. In other words, the above-described prior art is intended to solve the tracking control problem that occurs when the advanced push-pull method is adopted based on the light-receiving portion divided into two by the reference line parallel to the tangent line of the track.

  However, tracking control is possible if the push-pull method or the advanced push-pull method is used by using the light receiving unit divided into two by the reference line parallel to the tangent line of the track as in the above prior art. In focus control, which is another important control in accessing the recording disk, various measures must be taken for the optical system in order to use the divided light receiving section. In the above prior art, focus control is performed using astigmatism by providing a cylindrical lens in the optical system. That is, the number of parts constituting the playback device increases, which is problematic in terms of downsizing and cost reduction.

  Therefore, in order to efficiently perform tracking control and focus control, the light receiving unit is divided into three parts as shown in Patent Document 2 as a configuration of the light receiving unit, and a light receiving signal for tracking control and light reception for focus control. Signal is detected. However, when the light receiving unit having such a configuration is employed, each pickup device that is originally set to receive specific return light when the pickup device including the light receiving unit is transferred at a position off the radial line of the recording disk. The light receiving unit can easily receive the return light that is not planned, and there is a possibility that the influence affects both the tracking control and the focus control.

  In the present invention, in view of the problems described above, a pickup including a light receiving unit in a light receiving unit in which the configuration of the light receiving unit is divided into three areas for focus control and tracking control in order to access recording information in the recording disk. An optical module that suppresses the influence on both tracking control and focus control as much as possible when the apparatus is transported at a position deviated from the radial line of the recording disk, a pickup apparatus including the optical module, and the pickup apparatus An object of the present invention is to provide a recording disk reproducing apparatus.

  In order to solve the above problems, in the present invention, when the relative position of the optical module to the recording disk is a predetermined position, a line parallel to the tangent of the track is set as a predetermined reference line, and the light receiving unit is divided into three The return light is divided according to the predetermined reference line and received by each light receiving portion. That is, by determining a predetermined reference line that enables both tracking control and focus control, the pickup device including the light receiving unit is separated from the radial line of the recording disk by using the light receiving unit divided in three. It is intended to eliminate as much as possible the effect of being transferred in position.

  Specifically, the present invention guides the light source and the light emitted from the light source to a recording disk which is an information recording medium having a track in the recording area, and condenses the light returned from the recording disk as return light. A light guide part; and a light receiving part for receiving the return light collected by the light guide part, and for accessing the recording information in the recording disk, from the innermost peripheral part of the recording disk An optical module that is transported on a predetermined transport line outside the radius of the recording disk between the outermost peripheral portions, wherein the light receiving unit includes the return light and the optical module includes the innermost peripheral portion and the innermost peripheral portion. When the optical module is at a predetermined position with respect to the outer peripheral portion, the optical module receives a part of the return light in a focus adjustment area defined across a predetermined reference line parallel to the tangent line of the corresponding track. Fo A track adjustment light-receiving unit and track adjustment defined in the first track adjustment region and the second track adjustment region with the predetermined reference line sandwiched between the return light and the focus adjustment region. And a track adjusting light receiving portion for receiving a part of the return light in the work area.

In the optical module according to the present invention, the emitted light from the light source is guided to the recording disk, and the return light reflected and returned by the light receiving unit is received by the light receiving unit, so that the recorded information in the recording disk can be accessed. It becomes possible. At this time, in order to accurately acquire the recording information, it is necessary to irradiate the light emitted from the light source against the track of the recording disk. Therefore, focus control for controlling the focus of the emitted light with respect to the track and tracking control for controlling the relative position of the emitted light with respect to the track are required.

  Therefore, the optical module includes a focus adjustment light-receiving unit that receives a part of the return light for focus control and a track adjustment light-receiving unit that receives a part of the return light for tracking control. Yes. A part of the return light received by each light receiving unit is return light corresponding to a focus adjustment area and a track adjustment area defined with reference to a predetermined reference line. The focus adjustment area and the track adjustment area are defined based on a predetermined reference line. In addition, since the track adjustment area is formed by the first track adjustment area and the second track adjustment area, the light receiving unit of the optical module according to the present invention receives the return light received by the three divided light receiving units. In this way, the recording information in the recording disk is accessed.

  The predetermined reference line is a line parallel to the tangent of a predetermined track in the recording disk corresponding to the optical module when the optical module is located between the innermost peripheral portion and the outermost peripheral portion on the predetermined transfer line. . In other words, the influence on the focus control and tracking control that occurs when the optical module is transported on the predetermined transport line is that the inclination of the tangent of the track corresponding to the optical module with respect to the predetermined transport line is the predetermined transport of the optical module. It can be said that it is a reference line set in order to make the absolute value of the amount of change as small as possible in consideration of the fact that it changes depending on the position on the line. That is, assuming that the reference line is the track tangent when the optical module is at the innermost peripheral part or the outermost peripheral part, the absolute value of the amount of change is the largest. Therefore, in the optical module according to the present invention, the predetermined reference By adopting the line, it is intended to suppress the influence on the focus control and the tracking control (hereinafter referred to as “the present effect”) due to the optical module being transferred on the predetermined transfer line.

  The focus adjustment area is defined so as to straddle the predetermined reference line, so that it is possible to receive the return light necessary for focus control and suppressing the influence as much as possible. It becomes. The track adjustment area defines the first track adjustment area and the second track adjustment area across the predetermined reference line, and is a return light necessary for track control. Thus, it is possible to receive the return light that has been suppressed. Thus, in the optical module according to the present invention, a part of the return light is divided into focus control and track control with reference to the predetermined reference line, and each is received by the corresponding light receiving unit, This makes it possible to achieve both focus control and tracking control that eliminate the influence of this case as much as possible.

  Here, in the optical module, the optical module is servo-controlled in a relative position with respect to the predetermined track to follow the predetermined track in the recording disk, and the inclination of the predetermined reference line with respect to the predetermined transfer line is When the optical module is at the innermost peripheral portion, the amount of change in the inclination of the predetermined innermost reference line parallel to the track tangent corresponding to the optical module with respect to the predetermined transfer line, and the optical module is the outermost peripheral The change amount of the predetermined outermost reference line parallel to the tangent of the track corresponding to the optical module when the optical module is located with respect to the predetermined transfer line is such that the optical module has the innermost peripheral part and the outermost peripheral part. The amount of leakage of the return light in the track adjustment area to the focus adjustment light-receiving unit when it is transported between the servo control follows the servo control. So as to fall within a predetermined range to determine the, it may be set.

That is, in the optical module, the followability of the servo control is determined based on the amount of return light in the track adjustment area leaking into the focus adjustment light receiving unit, and the servo followability is maintained well. As described above, the predetermined reference line is set so as to be the amount of change in the inclination of the predetermined reference line with respect to the predetermined transfer line within the transfer range of the optical module. Here, the predetermined reference line may be set in consideration of not only the servo control for tracking control as described above but also the followability in servo control for focus control. In that case, the amount of change of the inclination of the predetermined reference line with respect to the predetermined transfer line from the inclination of the predetermined innermost reference line with respect to the predetermined transfer line, and the inclination of the predetermined outermost reference line with respect to the predetermined transfer line Is the amount of leakage of return light in the focus adjustment region into the track adjustment light-receiving unit when the optical module is transferred between the innermost peripheral part and the outermost peripheral part. Is set to fall within a predetermined range for determining the followability in servo control for focus control.

  Here, in the optical module described above, the light receiving unit for focus adjustment corresponds to two regions formed by dividing the focus adjustment region according to the predetermined reference line and is adjacent to each other. An element and a second light receiving element may be included, and the return light in the focus adjustment region may be guided to the vicinity of an adjacent portion between the first light receiving element and the second light receiving element. That is, the focus adjustment light-receiving unit is composed of a first light-receiving element and a second light-receiving element, and the return light in the focus adjustment area is guided to the vicinity of the adjacent portion so that the knife edge method (Fucault method) or the like. Focus control based on can be performed. At this time, the adjacent portion is located along a predetermined reference line, and the predetermined reference line is set to suppress the influence on the focus control as described above. The used focus control can be performed better.

  Here, in the optical module described above, the entire area of the return light is formed by the track adjustment area including the focus adjustment area, the first track adjustment area, and the second track adjustment area. The focus adjustment area is demarcated across the predetermined reference line so as to be symmetrical to the left and right across the predetermined reference line, and the track adjustment area is the focus of the entire area of the return light. The first track adjustment region and the second track adjustment region are formed by dividing the region excluding the adjustment region into left and right with the predetermined reference line as a center. That is, the entire area of the return light is composed of a focus adjustment area and a track adjustment area including a first track adjustment area and a second track adjustment area, so that a so-called three-divided light reception is performed. It will be.

  In the optical module described above, the track including the focus adjustment area, the first track adjustment area, and the second track adjustment area for the return light collected by the light guide section. The image forming apparatus further includes a dividing unit that divides into adjustment regions, and the focus adjustment light receiving unit and the track adjustment light receiving unit each receive a part of the return light divided by the dividing unit. Good. That is, the optical module includes a dividing unit as an optical element that divides the return light into regions for focus control and tracking control. This makes it possible to suppress the influence of the present case on the focus control and tracking control as much as possible. In addition, as an example of the division unit, a plurality of areas divided in correspondence with the track adjustment area including the focus adjustment area, the first track adjustment area, and the second track adjustment area. A hologram element having

  Here, in the optical module described above, the predetermined position may be an intermediate position between the innermost peripheral portion and the outermost peripheral portion. That is, the amount of change of the predetermined position with respect to the inclination of the predetermined reference line with respect to the predetermined transfer line and the inclination of the predetermined innermost reference line with respect to the predetermined transfer line, and the predetermined outermost reference line with the predetermined transfer The amount of change relative to the line, in other words, the position where the width of the absolute value of the amount of change can be minimized.

Here, the present invention can also be grasped from the side of a pickup device for accessing recorded information in a recording disk including an optical module. That is, the pickup device according to the present invention is the above-described optical module, wherein the light guide unit includes an optical module having a plurality of light sources as light sources for a plurality of types of recording disks, and records information in the recording disks. A pickup device for reading, wherein an objective lens that guides light emitted from each light source to a corresponding type of recording disk is provided corresponding to each of the plurality of light sources included in the light guide unit. One of the light sources and the objective lens corresponding to the one light source are transferred between the innermost peripheral portion and the outermost peripheral portion of the recording disk on a radial line of the recording disk, Of these, the other light sources other than the one light source and the objective lens corresponding to the other light sources may be transferred on the predetermined transfer line. With this configuration, it is possible to configure a pickup device that supports a plurality of types of recording disks. For example, a pair of one light source and one objective lens transferred on the radial line of the recording disk is associated with a recording disk that preferably has access to the recording information on the radial line, and another light source The other objective lens pair may correspond to a recording disk that does not necessarily require access to the recording information on the radial line. The predetermined transfer line may be parallel to the radial line of the recording disk.

  Further, when the present invention is viewed from the side of the pickup device as described above, the pickup device according to the present invention includes the optical module described above, and is a pickup device for reading recorded information in the recording disk. A focus adjusting unit that adjusts a focus of light emitted to the recording disk by the light guide unit based on a part of the return light received by the focus adjusting light receiving unit, and a track adjusting light receiving unit. A track adjusting unit that adjusts a relative position of the optical module with respect to a track in the recording disk based on a part of the received return light.

  Further, based on a part of the return light received by the focus adjustment light-receiving unit and a part of the return light received by the track adjustment light-receiving unit, the recording information that the recording disk has is recorded. It may be a pickup device provided with a recording information detection unit for detection.

  Here, the present invention can also be grasped from the side of a recording disk reproducing apparatus including a pickup device. That is, a recording disk reproducing apparatus according to the present invention includes the above-described pickup device, and includes a reproducing unit that reproduces the recording information in the recording disk based on the recording information detected by the recording information detecting unit.

  Pickup including a light receiving unit in an optical module, a pickup device, and a reproducing device having a light receiving unit whose structure is divided into three areas for focus control and tracking control in order to access recorded information in a recording disk When the apparatus is transported at a position deviating from the radial line of the recording disk, the influence on both tracking control and focus control can be suppressed as much as possible.

<Example 1>
Now, embodiments of an optical module, a pickup device, and a recording disk reproducing device according to the present invention will be described with reference to the accompanying drawings. In addition, the said Example shows an example of the optical module etc. which concern on this invention, and does not limit the scope of rights of this invention.

FIG. 1 is a diagram showing a configuration of a playback device 30 that plays back a recording disk. The playback device 30 is a device that plays back information recorded on a recording disk. A specific configuration of the reproducing apparatus 30 is that a spindle motor (not shown in FIG. 1) is provided in the approximate center of the apparatus main body 33 (which is shown as a spindle motor 32 in FIG. 2 described later), and is driven to rotate by the spindle motor. A turntable 34 is provided. When the recording disk is reproduced, the recording disk is arranged on the turntable 34. The description of the turntable 34 in FIG. 1 is shown in a transparent state so that the configuration of the playback device 30 can be easily understood.

  In addition, the reproducing device 30 is provided with a pickup device 20 that reads recorded information from a rotating recording disk. The pickup device 20 performs linear motion according to the rotation of the transfer motor 23a, the feed screw 23b, and the feed screw 23b so as to correspond to the track position of the recording information having information to be read, and the main body of the pickup device 20 Is transferred between the inner peripheral side and the outer peripheral side of the recording disk by a transfer device 23 comprising a base member 23c that also serves as a recording medium. The pickup device 20 has two objective lenses 21a and 21b (also referred to as “objective lens 21” when these objective lenses are comprehensively shown) in order to enable reading of a plurality of types of recording disks. Is provided. The optical system in the pickup device 20 including the objective lens 21 will be described in detail later. Further, the reproducing device 30 is used as a delivery mechanism for transporting a recording disc inserted by the user to the turntable 34 or ejecting the recording disc placed on the turntable 34 to the outside of the reproducing device 30. A roller 35 is provided.

  Next, the optical system in the pickup device 20 and the detection signal processing unit obtained there will be mainly described with reference to FIG. FIG. 2 schematically shows the playback apparatus 30 shown in FIG. In order to simplify the explanation and to help understanding of the present invention, in FIG. 2, a part of the configuration of the playback device 30 is omitted or simplified. For example, in FIG. 2, the description of the turntable 34 on which the recording disk 1 is arranged is omitted. Further, the optical system components such as the optical module 10 are originally installed inside the base member 23c (see FIG. 1), but FIG. 2 facilitates understanding of the present invention. Therefore, it is arranged on the base member 23c.

  The reproducing device 30 includes the optical module 10 according to the present invention and the pickup device 20. Here, the optical module 10 has an optical system for accessing the recording information in the recording disk 1, and details thereof will be described later. The pickup device 20 is a device for reading recorded information in the recording disk 1, and a collimator lens 22 that forms light emitted from a light source in the optical module into parallel light, and parallel light from the collimator lens 22. And an objective lens 21 that focuses the light onto a predetermined track of the recording disk 1. The pickup device 20 is provided with an actuator 25 for finely adjusting the relative position of the objective lens 21 with respect to the recording disk 1. Further, a transfer device 23 including a transfer motor 23a and the like for transferring the entire pickup device including the optical module 10 is provided.

  With the above-described configuration, when the recording disk 1 is reproduced, the pickup device 20 including the optical module 10 is transferred in a predetermined direction by the transfer device 23 while the recording disk 1 is rotationally driven by the spindle motor 32. The recording information is read sequentially. Here, at the time of reproducing the recording disk 1, control related to irradiation of the emitted light from the light source to the track is performed by the control unit 24 (for example, constituted by a CPU). The control unit 24 controls the focus of the emitted light with respect to the track and controls the relative positions of the emitted light so that the emitted light is accurately irradiated onto the track. Therefore, a function unit that performs the former control (hereinafter referred to as “focus control”) is referred to as a focus control unit 24a, and a function unit that performs the latter control (hereinafter referred to as “tracking control”) is referred to as a tracking control unit 24b. Both control units are included in the control unit 24. The control unit 24 is electrically connected to the optical module 10, and performs each control based on a detection signal from the optical module 10.

Further, the control unit 24 includes a detection unit 24c as a functional unit, and the detection unit 24c uses the detection signal from the optical module 10 to detect the recording information in the recording disk 1. The recording information detected by the detection unit 24c is transferred to the reproduction unit 31 in the reproduction apparatus 30, and the reproduction process of the recorded information is performed.

  Here, FIG. 3 shows a schematic configuration when the reproducing apparatus 30 shown in FIG. 2 is viewed from above, centering on a range in which the pickup apparatus 20 is transferred. The pickup device 20 includes the first objective lens 21a and the second objective lens 21b as the objective lens 21, thereby enabling reading of a plurality of types of recording disks. Here, the pickup device 20 is transferred from the innermost peripheral portion to the outermost peripheral portion in the recording area of the recording disk 1 in FIG. 3 by the transfer device 23, and the transfer drawn by the objective lens 21a at the time of the transfer. The locus L1 and the transfer locus L2 drawn by the objective lens 21b are parallel to each other. Here, the transfer locus L2 is a line overlapping the radius line of the recording disk 1, and the transfer locus L2 is offset from the transfer locus L1 along the surface of the recording disk 1 by a distance of ΔL.

  As the reproducing apparatus 30 that can read a plurality of types of recording disks by using two objective lenses as described above, a CD / DVD and a Blu-Ray (registered trademark) disk (hereinafter referred to as “BD”) are described. )). Here, due to the detection method used in reading the recorded information of the CD / DVD, it is necessary to move the objective lens on the radial line of the recording disk. On the other hand, it is not always necessary to read the recorded information on the BD by using the push-pull method or the like. Therefore, in this embodiment, the objective lens 21a is used for reading recorded information on a BD, and the objective lens 21b is used for reading recorded information on a CD / DVD.

  The optical system corresponding to the objective lens 21b for CD / DVD shown in FIG. 3 is a prior art, and is omitted in this specification. The optical module 10 is outlined with the optical system corresponding to the objective lens 21a for BD as the center. The configuration will be described with reference to FIGS. 4A and 4B. As shown in FIG. 4A, the optical module 10 includes a laser diode 12 serving as a light source, a hologram element 13 that functions as a beam splitter, and four photodetectors 11a to 11d that function as light receiving elements. In FIG. 4A, only the optical system for BD is shown, and the optical system for CD / DVD is not shown, but similarly, a light source, a light receiving element, etc. corresponding to the objective lens 21b are also provided. .

  Here, the emitted light from the laser diode 12 passes through the hologram element 13 once and is irradiated onto the recording surface of the recording disk 1, more precisely, the track corresponding to the recording information. Then, the light reflected by the recording disk 13 enters the hologram element 13 again as return light. Here, as shown in FIG. 4B, the light incident surface of the hologram element 13 has a circular shape and is divided into three regions RAB, RC, and RD by partitions 13L1 and 13L2. Specifically, as shown in FIG. 4B, the partition 13L1 divides the upper half of the circle, and the partition 13L2 further divides the remaining lower half region into half. The partition 13L2 intersects the partition 13L1 perpendicularly. Further, each region is provided with a diffraction grating, and each diffracted light is received by a corresponding photodetector. Specifically, the diffracted light in the region RAB is received by the photo detectors 11a and 11b, the diffracted light in the region RC is received by the photo detector 11c, and the diffracted light in the region RD is received by the photo detector 11d.

The light received by the photodetectors 11a and 11b is converted into an electric signal and then transferred to the focus control unit 24a, and the focus control of the objective lens 21a is performed by the focus control unit 24a. Specifically, the knife edge method is used in the focus control. In the knife edge method, a part of the return light divided by the region RAB of the hologram element 13 is condensed on the adjacent portions of the photodetectors 11a and 11b by an optical element (not shown). When the emitted light is focused on the track, the return light is condensed substantially in the state of a dot at the adjacent portion and is received almost equally by both photodetectors. On the other hand, if the focus is deviated, the return light is biased and received by either the photodetector 11a or 11b. Accordingly, the focus control unit 24a controls the focus of the objective lens 21a via the actuator 25 based on the difference between the detection signals from the photodetectors 11a and 11b.

  The light received by the photodetectors 11c and 11d is converted into an electric signal, and then transferred to the tracking control unit 24b. The tracking control unit 24b performs tracking control of the objective lens 21a. Specifically, the return light from the recording disk 1 becomes a so-called ball pattern as shown in FIG. In this ball pattern, a region where the light intensity is bright at the center and a region where the light intensity is weak at both sides are usually recognized. Then, when the position of the emitted light from the laser diode 12 with respect to the track is shifted, the relative position control of the emitted light with respect to the track, i.e., tracking control, is utilized by utilizing unevenness in the brightness of the regions on both sides. Is executed. Specifically, based on the difference between detection signals from the photodetectors 11c and 11d corresponding to the regions RC and RD of the hologram element 13 into which part of the return light enters, the objective lens is connected via the actuator 25 or the transfer device 23. 21a tracking control is performed.

  However, as described above, the objective lens 21a is transferred by the transfer device 23 not on the transfer locus L2 overlapping the radius line of the recording disk 1 but on the transfer locus L1 offset by ΔL therefrom. With reference to FIG. 5A and FIG. 5B, description will be made of the fact that the ball pattern of the return light reaches the light receiving element side in an inclined state. FIG. 5A is a diagram showing the relative positional relationship of the objective lens 21a with respect to the track, and FIG. 5B is a diagram showing the difference in the ball pattern of the return light at the two positions of the objective lens 21a shown in FIG. 5A. As shown in FIG. 5A, the pickup device 20 including the objective lens 21a has an innermost peripheral part (see FIG. 3) corresponding to the innermost track and an outermost peripheral part (similarly, see FIG. 3). Go back and forth between them. At this time, referring to the tangent of the track at the portion of the track irradiated with the light emitted from the laser diode 12, when the pickup device 20 is at the innermost peripheral portion, the tangent is the tangent TL1 shown in FIG. 5A. When the pickup device 20 is at the outermost peripheral portion, the tangent line is a tangent line TL2 shown in FIG. 5A.

  Here, since the transfer locus L1 is deviated from the radius line of the recording disk 1 by ΔL, the inclinations of the two tangents TL1 and TL2 with respect to the transfer tracks L1 and L2 are different. Although the objective lens 21b is not clearly shown in FIG. 5A, since the transfer locus L2 of the objective lens 21b overlaps the radial line of the recording disk 1, it is located at the innermost peripheral portion. Even in the case of being located at the outermost peripheral portion, as shown in FIG. 5A, the track tangent line RL1 is always perpendicular to the transfer locus L2.

Here, the deviation between the tangent line TL1 and the tangent line RL1 is represented by an angle θ1, and is calculated as follows.
θ1 = arcsin (ΔL / innermost track radius)
The deviation between the tangent line TL2 and the tangent line RL1 is represented by an angle θ2, and is calculated as follows.
θ2 = arcsin (ΔL / outermost track radius)

Accordingly, the ball pattern of the return light obtained by the objective lens 21a is between the state shown in FIG. 5A corresponding to the innermost peripheral part and the state shown in FIG. 5B corresponding to the outermost peripheral part. It will change continuously according to the position of 20. That is, since it is the center line of the ball pattern of the return light (that is, a line parallel to the tangent line of the track, it is given the same reference number as the tangent lines TL1 and TL2 in FIG. 5B. In some cases, TL1 and TL2 may be used as reference numbers.) Is not perpendicular to the transfer trajectories L1 and L2, and the inclination varies depending on the position of the pickup device 20. As a result, when the hologram element 13 divided into three areas as shown in FIG. 4B is used, the return light corresponding to the normal tracking state in the tracking control enters the areas RC and RD of the hologram element 13. The ball pattern is not always constant and varies depending on the position of the pickup device 20.

  Here, in the tracking control by the tracking control unit 24b, servo control is performed so that the difference amount of the detection signals from the photodetectors 11c and 11d becomes substantially zero. However, in such a case, in order to prevent the servo control from becoming unstable due to fluctuations in the ball pattern incident on the regions RC and RD of the hologram element 13 as described above, Means such as lowering the gain are taken, and as a result, the followability of the servo control may be reduced.

  Similarly, in the focus control by the focus control unit 24a, the followability of the servo control may be reduced. This is because when the center line of the ball pattern varies between TL1 and TL2, the amount of variation in the region RAB of the hologram element 13 in the regions on both sides of the ball pattern where the light intensity is relatively dark increases. This is because the servo control of the focus control may become a factor that destabilizes. Therefore, in the hologram element 13 provided in the optical module 10 according to the present invention, the hologram element 13 is installed so as to suppress as much as possible the decrease in follow-up performance of the servo control in the tracking control and the focus control. It has been adjusted. The adjustment will be described with reference to FIGS. 6A and 6B.

  FIG. 6A shows the relative relationship of the center line of the ball pattern (in other words, the tangent of the track shown in FIG. 5A corresponding to the center line) with respect to the contour EL of the return light. In the objective lens 21a transferred along the transfer locus L1 offset by ΔL from the center line of the recording disk 1, as described above, the center line of the return light ball pattern varies between TL1 and TL2. That is, the angle formed by the center line with respect to the track tangent RL1 in the transfer locus L2 varies between θ1 and θ2. Therefore, in the adjustment of the hologram element 13, a line that is intermediate between the center lines TL1 and TL2, that is, a line that has an angle θ0 made with respect to the track tangent line RL1 is (θ1 + θ2) / 2 is used as a reference line. The reference line that intersects the tangent line RL1 at θ0 is defined as a predetermined reference line TL0.

  The technical significance of the predetermined reference line TL0 is that the absolute value of the fluctuation range of the detection signal for focus control and the detection signal for tracking control is minimized between θ1 and θ2 in which the ball pattern of the return light varies. This is a reference line corresponding to the reference angle θ0. The track tangent corresponding to the reference angle θ0 is the track tangent when the pickup device 20 having the objective lens 21a reaches an intermediate portion between the innermost peripheral portion and the outermost peripheral portion of the track.

  When the predetermined reference line TL0 is set, the hologram element 13 is attached to the pickup device 20 so that the delimiter 13L1 of the hologram element 13 overlaps the predetermined reference line (see FIG. 6B). By attaching the hologram element 13 in this way, an area RAB for focus control is formed across the predetermined reference line TL0, and a light receiving area of the ball pattern is formed symmetrically across the predetermined reference line TL0. It will be. At this time, both detectors are installed such that adjacent portions of the photodetectors 11a and 11b overlap the predetermined reference line TL0. In addition, for the regions RC and RD of the hologram element 13 for tracking control, the respective regions are formed on the left and right sides of the predetermined reference line TL0.

As described above, the hologram element 13 is installed with the predetermined reference line TL as a reference so that the return light having the ball pattern can suppress the follow-up deterioration of the servo control in the focus control and the tracking control as much as possible. The light is divided into elements and received by the corresponding photodetectors 11a to 11d. As a result, as shown in FIG. 3, even in the reproducing apparatus 30 to which the pickup device 20 including the objective lens is transferred at a position deviated from the radial line of the recording disk 1, the recorded information in the recording disk 1 is satisfactorily read. Can be done.

<Example 2>
Next, a second embodiment of the optical module 10 according to the present invention will be described with reference to FIG. FIG. 7A is a diagram showing the configuration of the hologram element according to the present embodiment, and FIG. 7B shows a photodetector that receives the return light divided by the hologram element 13 and the hologram element 13. It is a figure which shows a response | compatibility with the area | region divided. In addition, about the component same as the hologram element 13 shown to FIG. 4B, the detailed description is abbreviate | omitted by attaching | subjecting the same reference number.

  In the hologram element 13, in addition to the state shown in FIG. 4B, the region RC is divided into two regions RC1 and RC2 by a partition 13L3, and the region RD is partitioned into two regions RD1 and RD2 by the partition 13L4. The delimiters 13L3 and 13L4 are set in parallel to the delimiters 13L1. Each region of the hologram element 13 is provided with a diffraction grating, and each diffracted light is received by a corresponding photodetector. Specifically, the diffracted light in the region RAB is received by the photodetectors 110a and 110b, and the diffracted light in the outer region RC1 out of the region RC is received by the photodetector 110c, and is received in the inner region (partition 13L1 side) region RC2. The diffracted light is received by the photodetector 110d. Of the region RD, the diffracted light in the outer region RD1 is received by the photodetector 110f, and the diffracted light in the inner region RD2 is received by the photo detector 110e.

  The hologram element 13 configured as described above is also attached to the pickup device 20 so that the partition 13L1 overlaps the predetermined reference line TL0, as in the case of the above embodiment. Thereby, also in the present embodiment, the return light having the ball pattern is divided into each element in a state where the follow-up deterioration of the servo control in the focus control and the tracking control can be suppressed as much as possible. Therefore, the followability of both controls is ensured.

  Further, focus control and tracking control in the present embodiment will be described below. As for the focus control, the light received by the photodetectors 110a and 110b is converted into an electric signal and then transferred to the focus control unit 24a, and the focus control of the objective lens 21a is performed by the focus control unit 24a. Since the details are as described above, the description is omitted.

  Accordingly, the tracking control will be described. The light received by the photodetectors 110c to 110f is converted into an electric signal and then transferred to the tracking control unit 24b, and the tracking control unit 24b performs the tracking control of the objective lens 21a. Here, among the regions RC and RD, the regions RC2 and RD2 located inside are not caused by the relative position of the emitted light with respect to the track, but return light caused by the lens shift of the objective lens 21a or the inclination of the recording disk 1 It is known that intensity changes occur. Therefore, by using the light intensity of the return light corresponding to these regions RC2 and RD2, it is possible to eliminate the influence of the lens shift and the tilt of the recording disk 1 and perform the tracking control more reliably.

Specifically, ΔS determined by the following equation is used.
ΔS = ((Sc + Sd) − (Se + Sf)) − α (Sd−Se)
Sc: detection value of return light by the photo detector 110c Sd: detection value of return light by the photo detector 110d Se: detection value of return light by the photo detector 110e Sf: detection value of return light by the photo detector 110f α: feedback amount That is, ΔS is By further subtracting a detection signal corresponding to the influence of the lens shift or the like from the difference between the detection signals from the photodetectors 110c and 110d corresponding to the regions RC and RD of the hologram element 13 into which a part of the return light enters, the outgoing light This is a more accurate calculation of the deviation from the track. Note that the feedback amount α may be appropriately determined in consideration of the stability of servo control for tracking control performed in the actual pickup device 20. Note that the region RC and the region RD can be further appropriately divided.

<Other examples>
As described above, the optical module 10 according to the present invention sets the predetermined reference line TL0 in order to appropriately divide the return light from the recording disk 1 for performing the focus control and tracking control of the objective lens 21a satisfactorily. Is. Therefore, as long as the division of the return light according to the predetermined reference line TL0 is executed, this corresponds to the embodiment of the present invention. For example, in the above-described embodiment, only the hologram element 13 is installed to be inclined according to the predetermined reference line TL0. However, the entire optical module 10 including the hologram element 13 may be installed to be inclined according to the predetermined reference line TL0.

  Even when the hologram element is installed at an angle, the important point is that the separators 13L1 and 13L2 for defining the areas RAB, RC, and RD are installed at an angle. As for the orientation of the diffraction grating, the orientation of the diffraction grating can be arbitrarily selected as long as the photodetectors corresponding to the respective regions can be appropriately arranged.

  In addition, as shown in FIG. 8 instead of the configuration shown in FIGS. 2 and 3, when the reproducing apparatus 30 has a structure in which the raising mirror 40 is interposed between the objective lens 21 a and the optical module 10, The position of the mirror 40 is set to a position corresponding to a track that is a tangent line that coincides with the predetermined reference line TL0, and the trajectory of the light by the rising mirror 40 is tilted so as to follow the predetermined reference line TL0. Is adjusted. Note that the orientation of the hologram element 13 is adjusted so that the partition 13L1 of the hologram element 13 in the optical module 10 coincides with the predetermined reference line TL0.

  The predetermined reference line is derived as a line positioned between the tangent lines TL1 and TL2. However, the predetermined reference line is not limited to the intermediate position as long as the follow-up performance of the servo control in the focus control and tracking control is not deteriorated. You may employ | adopt the line | wire of the arbitrary positions between TL1 and TL2 as a predetermined reference line.

It is a figure which shows the structure of the reproducing | regenerating apparatus of the recording disc based on the Example of this invention. 1 is a first diagram illustrating a schematic configuration of an optical module, a pickup device, and a playback device according to an embodiment of the present invention. It is a 2nd figure which shows schematic structure of the pick-up apparatus and reproducing | regenerating apparatus which concern on the Example of this invention. It is a figure which shows schematic structure of the optical module which concerns on the Example of this invention. It is a figure which shows the correlation with the hologram element shown to FIG. 4A, and a photodetector. It is a figure which shows the relative positional relationship of an objective lens and a recording disk in the reproducing | regenerating apparatus based on the Example of this invention. It is a figure which shows the ball | bowl pattern of the return light from a recording disk corresponding to the position of the objective lens shown to FIG. 5A. It is a figure which shows the predetermined reference line for the optical module which concerns on this invention. It is a figure which shows the hologram element installed according to the predetermined reference line shown by FIG. 6A. It is a figure which shows another Example of the hologram element in the optical module which concerns on this invention. It is a figure which shows another Example of the optical module which concerns on this invention, a pick-up apparatus, and a reproducing | regenerating apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Recording disc 10 ... Optical module 11a, 11b, 11c, 11d ... Photo detector 110a, 110b, 110c, 110d, 110e, 110f ... Photo detector 12 ... Laser diode 13 ··· Hologram elements 13L1, 13L2, 13L3, 13L4 ··· Separation 20 ··· Pickup devices 21, 21a and 21b · · · Objective lens 22 · · · Collimator lens 23 · · · Transfer device 23a ... Transfer motor 23b ... Feed screw 23c ... Base member 24 ... Control unit 25 ... Actuator 30 ... Reproducing device TL0 ... Predetermined reference line

Claims (12)

A light source;
A light guide unit that guides the emitted light from the light source to a recording disk that is an information recording medium having a track in a recording area, and condenses the light returned from the recording disk as return light;
A light receiving portion for receiving the return light collected by the light guide portion, and for accessing the recording information in the recording disc, between the innermost peripheral portion and the outermost peripheral portion of the recording disc. An optical module transported on a predetermined transport line outside the radius of the recording disk,
The light receiving unit is
Of the return light, when the optical module is at a predetermined position between the innermost peripheral part and the outermost peripheral part, the optical module is defined across a predetermined reference line parallel to the tangent of the corresponding track. A focus adjustment light-receiving unit that receives a part of the return light in the focus adjustment region,
Of the return light, the return light does not interfere with the focus adjustment area and is within the track adjustment area defined by the first track adjustment area and the second track adjustment area across the predetermined reference line. A light receiving unit for track adjustment that receives a part of the light,
Optical module. The optical module is servo-controlled relative to the predetermined track to follow the predetermined track in the recording disk;
The predetermined innermost reference line parallel to the tangent of the corresponding track of the optical module when the optical module is at the innermost peripheral portion of the predetermined reference line with respect to the predetermined transfer line is relative to the predetermined transfer line. When the optical module is located at the outermost peripheral portion, the change amount between the predetermined outermost reference line parallel to the tangent to the track corresponding to the optical module when the optical module is at the outermost peripheral portion, When the optical module is transferred between the innermost peripheral part and the outermost peripheral part, the amount of leakage of the return light in the track adjustment area into the focus adjustment light receiving unit is the followability of the servo control. Set to be within a predetermined range for determining
The optical module according to claim 1. The light receiving unit for focus adjustment includes a first light receiving element and a second light receiving element that correspond to two areas formed by dividing the focus adjustment area according to the predetermined reference line and are adjacent to each other,
Return light in the focus adjustment area is guided in the vicinity of an adjacent portion of the first light receiving element and the second light receiving element.
The optical module according to claim 1 or 2. The entire area of the return light is formed by the track adjustment area including the focus adjustment area, the first track adjustment area, and the second track adjustment area,
The focus adjustment area is demarcated across the predetermined reference line in a symmetrical state across the predetermined reference line,
The track adjustment area includes the first track adjustment area formed by dividing an area excluding the focus adjustment area in the entire area of the return light into left and right with the predetermined reference line as a center. Having the second track adjustment area,
The optical module according to claim 1. A dividing unit configured to divide the return light collected by the light guide unit into the track adjustment region including the focus adjustment region, the first track adjustment region, and the second track adjustment region; And more,
The focus adjustment light-receiving unit and the track adjustment light-receiving unit respectively receive a part of the return light divided by the division unit.
The optical module according to claim 1. The dividing unit is a hologram element having a plurality of regions divided in correspondence with the track adjustment region including the focus adjustment region, the first track adjustment region, and the second track adjustment region. is there,
The optical module according to claim 1.   The optical module according to any one of claims 1 to 6, wherein the predetermined position is an intermediate position between the innermost peripheral portion and the outermost peripheral portion. 8. The optical module according to claim 1, wherein the light guide unit includes an optical module having a plurality of light sources as light sources for a plurality of types of recording disks, and recording information in the recording disks. A pickup device for reading
In correspondence with each of the plurality of light sources that the light guide unit has, an objective lens that guides the emitted light from each light source to a corresponding type of recording disk is provided,
One of the plurality of light sources and the objective lens corresponding to the one light source are transferred between the innermost peripheral portion of the recording disk and the outermost peripheral portion on a radial line of the recording disc,
The other light sources except the one light source among the plurality of light sources and the objective lens corresponding to the other light sources are transferred on the predetermined transfer line.
Pickup device.   The pickup device according to claim 8, wherein the predetermined transfer line is parallel to a radial line of the recording disk. A pickup device that includes the optical module according to any one of claims 1 to 7, and that reads recorded information in the recording disk.
A focus adjustment unit that adjusts the focus of the emitted light to the recording disk by the light guide unit based on a part of the return light received by the focus adjustment light-receiving unit;
A track adjusting unit that adjusts a relative position of the optical module with respect to a track in the recording disk based on a part of the return light received by the track adjusting light receiving unit;
A pickup device comprising:   Recording for detecting recording information of the recording disk based on a part of the return light received by the focus adjustment light receiving unit and a part of the return light received by the track adjustment light receiving unit The pickup device according to claim 10, further comprising an information detection unit. A playback device for a recording disk comprising the pickup device according to claim 11,
A disk feeding / discharging mechanism for feeding the recording disk into or out of the reproducing apparatus;
A turntable that rotatably supports the recording disk fed into the playback device by the delivery mechanism at a predetermined reading position;
A motor for rotationally driving the turntable;
A transfer device for transferring the pickup device for reading the recording disk;
A reproducing unit for reproducing the recording information in the recording disk based on the recording information detected by the recording information detecting unit of the pickup device;
A playback device for a recording disk, further comprising:

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