JP2009110628A - Optical disk device, and driving control method of optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce track error offset caused by variation of layer thickness of optical disks by digital processing without adopting a special optical system configuration. <P>SOLUTION: This optical disk device includes a signal processing part which generates a track error signal Tr according to Tr=(A-D)-maä(B1+B2)-(C1+C2)} based on differential signals (A-D) showing a difference between respective light receiving element signals A and D of divided light receiving elements, differential signals ä(B1+B2)-(C1+C2)} showing a difference of respective sum signals of C1 and C2, and a coefficient ma set based on a ratio of tilt of DC offset in accordance with lens shift for a predetermined direction. The signal processing part sets the coefficient ma based on a radial position of the recording medium when recording or reproducing is performed for a predetermined recording layer of the optical recording medium. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to, for example, an optical disc apparatus and an optical disc drive control method, and more particularly to a technical field for reducing track error offset due to variations in optical disc layer thickness.

  Conventionally, a DVD (Digital Versatile Disc), which is an optical disk, is widely used as a recording medium for recording content with a large amount of information such as moving images. In the DVD, the content is recorded on a recording layer whose capacity is increased by multilayering.

  In such an optical disk apparatus that reads / writes information from / to the optical disk, the reflected light of the irradiated light on the information recording surface of the optical disk is received by a light detection unit divided into a plurality of regions, and the push-pull method is used. Thus, a track error signal is detected.

  Here, the “push-pull method” refers to an objective lens when the distribution of reflected light from the surface of an optical disc such as a DVD changes depending on the positional relationship between the light spot and the guide groove or pit row, and a track shift occurs. This is a technique characterized in that a track error signal is obtained using the difference in the amount of light by making use of the asymmetry above.

  By the way, in an optical disk apparatus that employs a tracking servo system based on the push-pull method that detects a track error signal with one beam, when the objective lens moves in the radial direction (perpendicular to the track) of the optical disk and the optical axis shifts, light detection is performed. The spot on the vessel translates, resulting in a DC offset in the detected push-pull signal itself.

In order to avoid such a problem, for example, in Patent Document 1, the light receiving element of the photodetector is divided into a plurality of regions, and the light reception outputs A, B1, B2, C1, C2 from the respective regions that receive the light spot. , D based on the track error signal Tr,
Tr = (AD) -ma {(B1 + B2)-(C1 + C2)}
And the coefficient ma is set based on the ratio of the slope of the DC offset according to the lens shift.

  However, such setting is performed only at one reference disk radius at the time of inserting the optical disk. Therefore, when recording / reproduction is performed by the optical disk device according to the prior art, the ratio of the slope of the DC offset according to the lens shift differs mainly due to the spherical aberration due to the layer thickness according to the radial position of the optical disk, which is the track error. It becomes a factor of signal degradation. As a result, the track error signal is deteriorated as the distance from the disk radial position increases with reference to the disk radial position where the ratio of the slope of the DC offset according to the lens shift is measured in order to determine the coefficient ma. The tracking servo characteristics such as off-track and off-track have been seriously hindered.

  In order to solve the problem of spherical aberration, Patent Document 2 has a concentric electrode pattern, and corrects spherical aberration caused by the thickness error of the cover layer according to the voltage applied to each electrode. A technique using a liquid crystal element is disclosed (see paragraph [0011] of the same document).

JP 2007-66450 A JP-A-2005-293809

  However, in the technique disclosed in Patent Document 2, a special configuration must be adopted to solve the spherical aberration problem, which makes the configuration complicated and increases the cost.

  Accordingly, the present invention employs a one-beam push-pull tracking servo optical pickup, and reduces the track error offset due to variations in the optical disc layer thickness by digital processing without employing a special optical system configuration. And

  The optical disc apparatus according to the first aspect of the present invention is divided into at least two parts in a predetermined direction on the optical recording medium, and both divided end parts are further divided into at least three parts in a direction perpendicular to the predetermined direction. A case where a divided light receiving element is provided, and a light detecting means for detecting return light from the optical recording medium by the divided light receiving element, and recording or reproduction on a predetermined recording layer of the optical recording medium having a plurality of layers The first difference signal that is the difference between the light receiving element signals of the central divided light receiving element among the three divided light receiving elements and the end portion in the vertical direction of the three divided light receiving elements. Based on a coefficient set based on the ratio of the slope of the DC offset corresponding to the lens shift with respect to the predetermined direction and the second difference signal that is the difference between the sum signals of the light receiving element signals of the two divided light receiving elements And track And a signal processing means for setting the coefficient based on the radial position of the optical recording medium when recording or reproducing is performed on a predetermined recording layer of the optical recording medium. .

  Therefore, the coefficient is suitably set based on the radial position of the optical recording medium by the signal processing means.

An optical disc apparatus according to a second aspect of the present invention is an optical disc apparatus that records or reproduces information with respect to an optical recording medium, and is divided into at least two in a predetermined direction on the optical recording medium, and the divided end portions Has a divided light receiving element that is further divided into at least three parts in a direction perpendicular to the predetermined direction, the photodetector that detects return light from the optical recording medium by the divided light receiving element, and the both ends The difference signal (A−D) which is the difference between the light receiving element signals A and D of the central divided light receiving element among the divided light receiving elements divided into at least three in the vertical direction of the part, and the vertical of the both end parts The difference signal {(B1 + B) which is the difference between the sum signals of the light receiving element signals B1 and B2, C1 and C2 of the two divided light receiving elements at the end in the vertical direction among the divided light receiving elements divided into at least three in the direction ) - (a C1 + C2)}, based on the coefficient ma that is set based on the ratio of the slope of the DC offset corresponding to the lens shift for said predetermined direction, a track error signal Tr,
Tr = (AD) -ma {(B1 + B2)-(C1 + C2)}
A signal processing unit that executes processing to be generated according to
The signal processing unit sets the coefficient ma based on the radial position of the recording medium when performing recording or reproduction on a predetermined recording layer of the optical recording medium during the processing.

  Therefore, the coefficient ma is suitably set based on the radial position of the optical recording medium by the signal processing unit.

  In the second aspect, the signal processing unit calculates the coefficient ma corresponding to a predetermined radial position of the optical recording medium at the start adjustment, and at the seek time, the optical recording calculated at the start adjustment is performed. The coefficient ma corresponding to the radial position to be recorded or reproduced may be set based on the relationship between the radial position of the medium and the value of the coefficient ma.

  In the second aspect, the signal processing unit calculates a coefficient ma corresponding to at least two predetermined radial positions of the optical recording medium at the time of start adjustment, and at the time of seek, the optical recording medium The coefficient ma corresponding to the predetermined radial position closest to the radial position to be recorded or reproduced may be set.

  Alternatively, in the second aspect, the signal processing unit calculates the coefficient ma corresponding to a predetermined radial position of the optical recording medium at the time of start adjustment, and at the time of seek, the above-mentioned value calculated at the start adjustment The coefficient ma corresponding to the radial position to be recorded or reproduced may be set based on the approximate expression that is the relationship between the radial position of the optical recording medium and the value of the coefficient ma.

  In the second aspect, the approximate expression may be a linear function or a quadratic function with the radial position of the optical recording medium as a variable.

  The optical disk drive control method according to the third aspect of the present invention is divided into at least two in a predetermined direction on the optical recording medium, and the divided ends are at least further in a direction perpendicular to the predetermined direction. An optical disc drive control method by an optical disc apparatus having a divided light receiving element divided into three and having a light detecting means for detecting return light from the optical recording medium by the divided light receiving element, wherein the signal processing means comprises: When recording or reproduction is performed on a predetermined recording layer of an optical recording medium having a plurality of layers, a first difference which is a difference between light receiving element signals of a central divided light receiving element among the three divided light receiving elements. A second difference signal that is the difference between the sum signals of the light receiving element signals of the two divided light receiving elements at the end in the vertical direction among the three divided light receiving elements, and the predetermined signal For direction A tracking error signal is generated based on a coefficient set based on the ratio of the slope of the DC offset corresponding to the sensor shift, and when recording or reproducing on a predetermined recording layer of the optical recording medium, The coefficient is set based on the radial position of the optical recording medium.

  Accordingly, the coefficient is preferably set based on the radial position of the optical recording medium.

The optical disk drive control method according to the fourth aspect of the present invention is divided into at least two in a predetermined direction on the optical recording medium, and both divided end portions are perpendicular to the predetermined direction. An optical disc drive control method by an optical disc apparatus comprising at least a divided light receiving element divided into three and provided with a photodetector for detecting return light from the optical recording medium by the divided light receiving element. The processing unit is a difference signal (A−D) that is a difference between the light receiving element signals A and D of the central divided light receiving element among the divided light receiving elements divided into at least three in the vertical direction at both ends, and the above This is the difference between the sum signals of the light receiving element signals B1 and B2, C1 and C2 of the two divided light receiving elements at the end in the vertical direction among the divided light receiving elements divided at least in the vertical direction at both ends. Differential signal And - {(B1 + B2) (C1 + C2)}, based on the coefficient ma that is set based on the ratio of the slope of the DC offset corresponding to the lens shift for said predetermined direction, a track error signal Tr,
Tr = (AD) -ma {(B1 + B2)-(C1 + C2)}
Execute the process to generate according to
In the process, when recording or reproducing is performed on a predetermined recording layer of the optical recording medium, the coefficient ma is set based on the radial position of the recording medium.

  Accordingly, the coefficient ma is suitably set based on the radial position of the optical recording medium.

  In the fourth aspect, the signal processing unit calculates a coefficient ma corresponding to a predetermined radial position of the optical recording medium at the start adjustment, and at the seek time, the optical recording calculated at the start adjustment is performed. The coefficient ma corresponding to the radial position to be recorded or reproduced may be set based on the relationship between the radial position of the medium and the value of the coefficient ma.

  In the fourth aspect, the signal processing unit calculates a coefficient ma corresponding to at least two predetermined radial positions of the optical recording medium at the time of start adjustment, and at the time of seek, the optical recording medium The coefficient ma corresponding to the predetermined radial position closest to the radial position to be recorded or reproduced may be set.

  Alternatively, in the fourth aspect, the signal processing unit calculates the coefficient ma corresponding to a predetermined radial position of the optical recording medium at the time of start adjustment, and at the time of seek, the above-mentioned value calculated at the start adjustment The coefficient ma corresponding to the radial position to be recorded or reproduced may be set based on the approximate expression that is the relationship between the radial position of the optical recording medium and the value of the coefficient ma.

  In the fourth aspect, the approximate expression may be a linear function or a quadratic function with the radial position of the optical recording medium as a variable.

  According to the present invention, an optical disc apparatus that employs a one-beam push-pull tracking servo optical pickup and reduces track error offset due to variations in the layer thickness of the optical disc by digital processing without adopting a special optical system configuration, An optical disk drive control method can be provided.

  The best mode for carrying out the present invention (hereinafter simply referred to as an embodiment) will be described below in detail with reference to the drawings.

  FIG. 1 shows and describes the configuration of an optical disc apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, a collimator lens 2 and a polarizing beam splitter (PBS) 3 are sequentially arranged on the optical path of the light emitted from the semiconductor laser 1. A quarter-wave plate 4 and an objective lens 5 are sequentially disposed on the light transmission side of the PBS 3. An optical disk 6 that is an example of an optical recording medium is positioned on the laser beam output side of the objective lens 5. On the return light side optical path in the return path of the PBS 3, there are a condenser lens 7, a half mirror 8, two photodetectors (PD1) 9 for detecting the return light separated by the half mirror 8, and a photodetector (PD2). ) 10 is provided. The detection signals of the two photodetectors (PD1) 9 and (PD2) 10 are input to the signal processing unit 11.

  In the signal processing unit 11, a track error signal Tr and a focus error signal Fo are generated, and the signals Tr and Fo are output to a servo control system (not shown), and tracking servo and focus servo are executed by pickup or lens driving. The Of course, the signal processing unit 11 may be disposed inside or outside the optical pickup 100.

  Among the above configurations, the photodetectors 9 and 10 function as, for example, light detection means, and the signal processing unit 11 functions as, for example, signal processing means. Of course, for example, a data recording medium using light interference fringes can also be adopted as the optical recording medium.

  In such a configuration, the light emitted from the semiconductor laser 1 is collimated (that is, converted into parallel light) by the collimator lens 2 and then enters the PBS 3. PBS3 has a polarizing mirror. The incident light beam passes through the PBS 3, is converted into circularly polarized light by the quarter wavelength plate 4, and is collected on the optical disk 6 by the objective lens 5.

  The light reflected by the optical disk 6 passes through the objective lens 5 and the quarter-wave plate 4, is converted into linearly polarized light orthogonal to the forward polarized light, and is reflected by the PBS 3. The light reflected by the PBS 3 is condensed by the condenser lens 7 and separated into two by the half mirror 8, and then one light is received at a position close to L from the condensing point S1 to the half mirror 8 side. The light is received by a photodetector (PD1) 9 having a surface, and the other light is received by a photodetector (PD2) 10 having a light receiving surface at a position L away from the condensing point S2 to the half mirror 8 side. Is done.

  Here, the configuration of the photodetectors (PD1) 9 and (PD2) 10 is, for example, as shown in FIG. That is, the photodetector (PD1) 9 and the photodetector (PD2) 10 are divided into three in the radial direction (disc radial direction) in a symmetrical pattern with respect to the center line.

  In FIG. 2, as shown in FIG. 2A, the photodetector (PD1) 9 is divided into three in a radial direction (disk radial direction) which is a predetermined direction in a symmetric pattern with respect to the center line. Further, the light receiving portions at both ends in the radial direction other than the central portion I are divided into three in the direction perpendicular to the radial direction, that is, the track direction (B1, A, B2, and C1, D, C2), for a total of seven. The divided light receiving elements A, B1, B2, C1, C2, D, and I are configured.

  Further, in FIG. 2, as shown in FIG. 2B, the photodetector (PD2) 10 is divided into three in the radial direction (disk radial direction) in a symmetrical pattern with respect to the center line. It consists of divided light receiving elements E, H, and J.

  Under such a configuration, the photodetector (PD1) 9 receives the light spot at a position close to the half mirror by L from the light condensing point S1, and the photodetector (PD2) 10 condenses the light. A light spot at a position L away from the half mirror from the point S2 is received.

  The signal processing unit 11 inputs a light receiving element signal detected by the photodetector (PD1) 9 and calculates a track error signal Tr by the following equation. Here, the light receiving element signals from a total of seven divided light receiving elements are A, B1, B2, C1, C2, D, and I.

Tr = (AD) -ma {(B1 + B2)-(C1 + C2)} (1)
Here, ma is a correction coefficient for correcting the influence of the lens error of the track error signal Tr. A single optical detector (PD1) 9 has a far-field receiving optical pickup configuration for detecting the main signal and the correction signal of the tracking error signal. Here, the far field refers to a method of detecting light before the focused focal point, as in the photodetector (PD1) 9 shown in FIG.

  Hereinafter, a case where the objective lens 5 is shifted in the radial direction as the disk radial direction will be considered.

  FIG. 3 shows the correspondence between the shift amount of the objective lens 5 in the radial direction and the track error signal Tr calculated by the equation (1), and the shift amount of the objective lens 5 and the equation (1). A graph relating to a correspondence relationship with each signal value of (AD) and {(B1 + B2) − (C1 + C2)} as components will be described.

  In FIG. 3, the lens shift [mm] indicates a change in each signal when the central portion is 0 and a lens shift occurs in a range of −0.25 to +0.25 from the central portion.

  The position of the lens shift 0 in the center is a state in which the objective lens 5 is disposed at the correct track position of the optical disc 6. FIG. 3 shows changes in each signal when the objective lens 5 has a lens shift in the range of −0.25 to +0.25 in the radial direction.

  As the objective lens 5 is shifted, the DC level of the (AD) signal is offset. The (AD) signal is a signal with a relatively large slope, and the (AD) signal is large when the lens shift is in the-direction, and the (AD) signal is large when the lens shift is in the + direction. Get smaller. That is, it can be seen that the (AD) signal has a DC level offset as a direct current component with a relatively large slope.

  On the other hand, the DC level of the {(B1 + B2)-(C1 + C2)} signal is offset with a slope different from that of the (AD) signal. That is, as shown in FIG. 3, the {(B1 + B2) − (C1 + C2)} signal is a signal having a relatively small slope and has a relatively small slope. When the lens shift is in the −direction, {(B1 + B2) − (C1 + C2)} The signal becomes large, and the {(B1 + B2)-(C1 + C2)} signal becomes small when the lens shift is in the + direction. That is, the {(B1 + B2)-(C1 + C2)} signal has a DC level offset as a direct current component with a relatively small slope, which is different from the (AD) signal.

  Therefore, in this embodiment, first, the coefficient ma set in the calculation formula (1) of the track error signal Tr is set to the slope of the DC offset of the (AD) signal that can be calculated from the graph shown in FIG. (B1 + B2) − (C1 + C2)} The DC offset slope ratio of the signal is set. When the track error signal Tr is calculated by setting the coefficients in this way, only a pure track error signal with no DC level offset is obtained from the track error signal Tr even if a lens shift occurs.

  However, in the case of performing recording / reproduction at various addresses on the optical disk, that is, the disk radial position with the conventional configuration as described above, a track error occurs when the objective lens is made to follow the tracking by the disk radial position and the lens is shifted. An offset variation that cannot be corrected occurs in the signal. For example, as shown in FIG. 4, the optical disc has a variation in the layer thickness that varies depending on the radial position of the disc, and due to the variation in the layer thickness, the optical disk has an outside of the objective lens indicated by the solid line as shown in FIG. A so-called spherical aberration occurs in which the focal position differs between the light of the diameter and the light of the inner diameter of the objective lens indicated by the dotted line.

  In FIGS. 5A to 5C, the optical disc 6 is assumed to have a structure in which a recording layer 6b and a protective layer 6a are sequentially laminated on a base 6c.

  FIG. 5A shows a state in which the film thickness is small and spherical aberration occurs, and FIG. 5B shows a state in which the film thickness is appropriate and no spherical aberration occurs, and FIG. Indicates that the film thickness is large and spherical aberration occurs. In both cases where the film thickness is thin or thick, spherical aberration becomes a problem. Such spherical aberration appears as a difference in light intensity distribution on the photodetectors 9 (PD1) and 10 (PD2), and the difference in the light intensity distribution causes a DC offset of the [AD] signal. The ratio of the slope and the slope of the DC offset slope of the [(B1 + B2) − (C1 + C2)] signal changes, thereby causing a deviation from the coefficient [ma] obtained with the disk radius of a certain layer thickness.

  Here, FIG. 6 shows the relationship between the spherical aberration (here, third-order spherical aberration (mλrms)) and the coefficient ma. As the spherical aberration increases, the ideal ideal value of the coefficient ma decreases. This can also be read from the figure.

  In view of the above problems, the present embodiment proposes an adjustment method that employs a one-beam push-pull tracking servo optical pickup to reduce track error offset due to variations in layer thickness. The present embodiment is characterized in that the coefficient [ma] is set to two or more different values according to the disk radial position.

  Hereinafter, with reference to the flowchart of FIG. 7, a start adjustment sequence performed at the time of insertion of the optical disc by the optical disc apparatus according to the embodiment of the present invention will be described.

  When the optical disk is inserted into the drive (step S101), the focus servo is turned on (step S102). Next, the counter x for obtaining the coefficient [ma] is cleared to 0 (step S103), and moved to the disk radius position r (0) (step S104).

Subsequently, the ratio between the average value of the A-D signal and the average value of the (B1 + B2)-(C1 + C2) signal when this constant distance shift process is executed, that is,
Average value of AD signal / (B1 + B2) − (C1 + C2) average value of signal = [ave (AD)] / [ave ((B1 + B2) − (C1 + C2))] (2)
Is calculated (step S105).

Then, the correction coefficient [ma] is changed to ma = [ave (A−D)] / [ave ((B1 + B2) − (C1 + C2))] (3)
(Step S106).

  Thus, the loop is repeated until the above steps S104 to S106 are repeated n times the specified number of times, and n coefficients [ma (0),... Ma (n−1) corresponding to the respective disk radial positions [ma ] Is determined (step S107), and the start adjustment is terminated.

  Here, with reference to FIGS. 8 and 9, the correction coefficient [ma] calculation processing in steps S105 and S106 of FIG.

  In step S105 in FIG. 7, a DC driving current is supplied to the objective lens actuator to shift the lens by a certain amount. This is because the objective lens 5 of the optical pickup shown in FIG. 1 is shifted by a certain distance in the radial direction of the disk, and the average value ave (A-D) of the A-D signal when this certain distance shift process is executed, A process of calculating the ratio of the average value ave ((B1 + B2)-(C1 + C2)) of the (B1 + B2)-(C1 + C2) signal from the above equation (2) is executed.

  This process will be further described. The graph shown in FIG. 8 is similar to FIG. 3 described above, the shift amount of the objective lens of the optical pickup, the track error signal (Tr) calculated by the above equation (1), and the configuration of the above equation (1). It is a graph which shows the correspondence with each signal value of [AD] and [(B1 + B2)-(C1 + C2)] as an element.

  It is assumed that a certain amount of lens shift in step S105 in FIG. 7 is executed up to [−0.1] in the left direction in the graph shown in FIG. After this lens shift process, the ratio of the average value of the A-D signal and the average value of the (B1 + B2)-(C1 + C2) signal when the shift process of the constant distance is executed is calculated from the above equation (2).

  The average value ave (AD) of the AD signal corresponds to the height of the triangle [a] shown in FIG. 8, and the average value ave ((B1 + B2) − (C1 + C2) of the (B1 + B2) − (C1 + C2) signal. )) Corresponds to the height of the triangle [b] shown in FIG.

  FIG. 9 shows and explains a conceptual diagram in which these triangles are extracted.

  That is, the height h1 of the triangle [a] shown in FIG. 9 is an average value of the A-D signals when the lens shift is performed up to [−0.1] in the left direction in the graph shown in FIG. It corresponds to ave (AD). Further, the height h2 of the triangle [b] shown in FIG. 9 is the average of the (B1 + B2) − (C1 + C2) signals when the lens shift is performed up to [−0.1] in the left direction in the graph shown in FIG. It corresponds to the value ave ((B1 + B2) − (C1 + C2)).

  Thus, each average value corresponds to the slope of the DC level of each signal.

  In step S105, the ratio of the slopes of these two signals (h1 / h2) is calculated by the above equation (2), and in step S106, the correction coefficient [ma] is set by the above equation (3). It is running.

  Next, with reference to FIG. 10, a sequence at the time of seek by the optical disc apparatus according to the embodiment of the present invention will be described in detail.

  First, a rough movement is made to the seek target address (step S110). Next, the target seek address is compared with the intermediate positions of the respective radial positions of r (0),..., R (n−1) for which ma (0),. (Steps S120 to S12 (n-2)). Then, a coefficient [ma] suitable for each radial position is set (steps S130 to S13 (n-1)), and a track jump which is a final moving means for reaching the target address is performed (step S111). Thus, the seek is finished. By performing such control, even for a disk having a very varied layer thickness, track servo is executed by detecting a good track error with little DC offset when the field of view fluctuates.

  In this embodiment, coefficients ma (0),..., Ma (n−1) respectively corresponding to the radial positions r (0),..., R (n−1) obtained by the start adjustment in steps S101 to S107. ) Are set directly, but in this case, the coefficient ma changes digitally depending on the radial position.

  However, since the actual layer thickness changes continuously, the obtained coefficients ma (0),..., Ma (n−1) are set to make ma more smoothly follow the change in the layer thickness. Of course, approximation may be performed using approximation means such as linear function approximation or quadratic function approximation, and the coefficient ma may be changed continuously with respect to the radial position.

  Hereinafter, an improved example of the present embodiment that employs such an approximation means will be described.

  First, a start adjustment sequence performed when an optical disc is inserted by an optical disc apparatus according to an improved example of an embodiment of the present invention will be described with reference to a flowchart of FIG. When the optical disk is inserted into the drive (step S201), the focus servo is turned on (step S202), the counter x for obtaining the coefficient [ma] is cleared to 0 (step S203), and the disk radius position r (0) (Step S204).

  Next, a ratio between the average value of the A-D signal and the average value of the (B1 + B2)-(C1 + C2) signal when this constant distance shift process is executed is calculated by the above equation (2) (step S205), and the correction coefficient [ ma] is set by the above equation (3) (step S206). The loop is repeated until these steps S204 to S206 are repeated n times the specified number of times, and n coefficients [ma] up to ma (0),... Ma (n−1) corresponding to the respective disk radial positions are obtained. Determination (step S107), an approximate expression ma (r) is calculated from the calculated ma (r (0)),... Ma (r (n-1)) (step S208), and the start-up adjustment is terminated.

For example, when linear function approximation is adopted,
ma (r) = Ar + B (A and B are predetermined numbers) (4)
It becomes.

  Next, with reference to FIG. 12, a sequence at the time of seek by the optical disc apparatus according to the improved example of the embodiment of the present invention will be described in detail.

  First, a rough movement is made to the seek target address (step S210). Next, ma (r) corresponding to the disk radius position r is set based on the above equation (4) (step S211), and a track jump which is the final moving means for reaching the target address is performed (step S212). Thus, the seek is finished. By performing such control, even for a disk having a very varied layer thickness, track servo is executed by detecting a good track error with little DC offset when the field of view fluctuates.

  By the way, the calculation processing of the track error signal Tr based on the processing of the above-described embodiment can be applied to pickups having various configurations.

  Therefore, FIG. 13 shows a pickup configuration that realizes a reduction in size, and the detection processing of the track error signal Tr by this configuration will be described in detail.

  As shown in FIG. 13, a prism 52 is disposed on the optical path of the laser light of the semiconductor laser 51, and the light reflected by the PBS film 53 formed on the 45-degree inclined surface 64 of the prism 52. On the road, a quarter-wave plate 54, a collimating lens 55, and an objective lens 56 are arranged in this order. On the prism bottom surface 61 of the prism 52, photodetectors (PD1) 59 and (PD2) 60 are arranged. The light detector (PD1) 59 is disposed so that the light receiving surface is positioned on the light transmission path of the PBS film 53 of the prism 52 of the reflected light 52 from the optical disc 57, and the light detector (PD2) 60 is reflected by the light detector (PD2) 60. The light receiving surface is disposed on the reflection optical path of the half mirror film 59 of the light prism 52 and the mirror coat of the prism upper surface 63.

  In such a configuration, light emitted from the semiconductor laser 51 is reflected 45 degrees by the PBS film 53 formed on the 45-degree inclined surface 64 of the prism 52 and converted into circularly polarized light by the quarter-wave plate 54. After that, the light is collimated by the collimating lens 55 and condensed on the optical disk 57 by the objective lens 56. The light reflected by the optical disk 57 passes through the objective lens 56, the collimating lens 55, and the quarter wavelength plate 54 and is converted into linearly polarized light orthogonal to the forward polarized light. The light converted into the linearly polarized light is divided into light that is transmitted through the PBS film 53 on the 45-degree inclined surface 64 of the prism 52, 50% transmitted through the half mirror film 58 on the prism bottom surface 61, and light that is reflected 50%. The light transmitted through the half mirror film 58 is received by the photodetector (PD1) 59 disposed on the prism bottom surface 61.

  On the other hand, the light reflected by the half mirror film 58 is reflected by the mirror coat 62 on the prism upper surface 63 and enters the prism bottom surface 61 again. The light incident on the prism bottom surface 61 is received by a photodetector (PD2) 60 disposed on the prism bottom surface 61.

  In this pickup configuration, the photodetector (PD1) 59 and the photodetector (PD2) 60 have the photodetector configurations shown in FIGS. 2 (a) and 2 (b), respectively.

  That is, as shown in FIG. 2A, the photodetector (PD1) 59 is divided into three in the radial direction (disk radial direction) in a symmetrical pattern with respect to the center line, and further, other than the central portion (I). A total of seven divided light receiving elements (A, B1, B2, C1, C2, D, I) in which the light receiving portions at both ends are divided into three in the track direction (B1, A, B2, and C1, D, C2), respectively. It is set as a photodetector composed of Further, as shown in FIG. 2 (b), the photodetector (PD2) 60 has a total of three divided light receiving elements divided into three in the radial direction (disk radial direction) in a symmetrical pattern with respect to the center line. It is set as a photodetector composed of (E, H, J).

  Even in such a downsized pickup configuration, control using the track error signal Tr according to the above-described embodiment is realized.

  As described above in detail, according to the configuration of an embodiment of the present invention, the light receiving portions at both ends divided into three in the radial direction corresponding to the disk radial direction are further divided into three in the track direction perpendicular to the radial direction. The divided first photodetector and the second photodetector divided in the radial direction are applied, and a track error signal is generated mainly by an input signal from the first photodetector. Therefore, according to the optical disc apparatus and the optical disc drive control method according to the present embodiment, it is possible to reduce the DC offset of the track error at the time of lens shift due to spherical aberration of the disc having a large layer thickness variation.

  The embodiment of the present invention has been described above, but the present invention is not limited to this, and it is needless to say that various improvements and changes can be made without departing from the spirit of the present invention.

  For example, regarding the setting of the coefficient ma corresponding to the disk radial position at the time of start adjustment, the coefficient ma corresponding to the disk radial position of three or more points is set, and an approximate expression is calculated by the least square method based on them, and seek is performed. It may be used sometimes.

1 is a configuration diagram of an optical disc apparatus according to an embodiment of the present invention. The block diagram of the photodetector employ | adopted as an optical disk apparatus. Correspondence between the shift amount of the objective lens in the radial direction and the track error signal Tr, and the correspondence between the shift amount of the objective lens and each signal value of (AD) and {(B1 + B2)-(C1 + C2)} Graph related to the relationship. The figure which shows the relationship between a disc radius position and layer thickness. (A) thru | or (c) is a figure which shows notionally the influence of spherical aberration. The figure which shows the relationship between spherical aberration and coefficient ma. The flowchart explaining the starting adjustment sequence performed at the time of insertion of the optical disk by the optical disk apparatus which concerns on one embodiment of this invention. The figure for supplementarily explaining calculation processing of correction coefficient [ma]. The figure for supplementarily explaining calculation processing of correction coefficient [ma]. 6 is a flowchart for explaining in detail a sequence at the time of seek by the optical disc apparatus according to the embodiment of the present invention. The flowchart explaining the sequence of starting adjustment performed at the time of insertion of the optical disk by the optical disk apparatus which concerns on the improvement of one embodiment of this invention. 6 is a flowchart for explaining in detail a sequence at the time of seek by the optical disc apparatus according to an improved example of the embodiment of the present invention. The figure which shows the pick-up structure which implement | achieved size reduction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Collimating lens, 3 ... Polarizing beam splitter, 4 ... 1/4 wavelength plate, 5 ... Objective lens, 6 ... Optical disk, 7 ... Condensing lens, 8 ... Half mirror, 9 ... Photodetector, DESCRIPTION OF SYMBOLS 10 ... Photodetector, 11 ... Signal processing part, 12 ... Optical disk, 12b ... 1st recording layer, 12d ... 2nd recording layer

Claims (12)

The divided light receiving element is divided into at least two parts in a predetermined direction on the optical recording medium, and both divided end parts are further divided into at least three parts in a direction perpendicular to the predetermined direction. Light detecting means for detecting return light from the optical recording medium;
When recording or reproduction is performed on a predetermined recording layer of an optical recording medium having a plurality of layers, a first difference which is a difference between light receiving element signals of a central divided light receiving element among the three divided light receiving elements. A second difference signal that is the difference between the sum signals of the light receiving element signals of the two divided light receiving elements at the end in the vertical direction among the three divided light receiving elements, and the predetermined signal A tracking error signal is generated based on a coefficient set based on a ratio of a DC offset inclination corresponding to a lens shift with respect to a direction, and is recorded or reproduced on a predetermined recording layer of the optical recording medium. In this case, an optical disc apparatus comprising: signal processing means for setting the coefficient based on a radial position of the optical recording medium. In an optical disc apparatus for recording or reproducing information with respect to an optical recording medium,
The optical recording medium is divided into at least two parts in a predetermined direction, and the divided light receiving elements are divided into at least three parts in a direction perpendicular to the predetermined direction at both ends. A photodetector for detecting return light from the optical recording medium by the divided light receiving element;
A difference signal (A−D) that is a difference between the light receiving element signals A and D of the central divided light receiving element among the divided light receiving elements divided into at least three in the vertical direction of the both end parts, and the above-mentioned Of the divided light receiving elements divided into at least three in the vertical direction, the difference signal {() is the difference between the sum signals of the light receiving element signals B1 and B2, C1 and C2 of the two divided light receiving elements at the end in the vertical direction. B1 + B2) − (C1 + C2)} and a coefficient ma set based on the ratio of the slope of the DC offset corresponding to the lens shift with respect to the predetermined direction, the track error signal Tr is
Tr = (AD) -ma {(B1 + B2)-(C1 + C2)}
A signal processing unit that executes processing to be generated according to
The signal processing unit sets the coefficient ma based on a radial position of the recording medium when recording or reproducing the predetermined recording layer of the optical recording medium in the processing. apparatus. The signal processing unit calculates a coefficient ma corresponding to a predetermined radial position of the optical recording medium at the time of start adjustment, and at the time of seek, the radius position and coefficient of the optical recording medium calculated at the start adjustment. The optical disk apparatus according to claim 2, wherein a coefficient ma corresponding to a radial position for recording or reproduction is set based on a relationship with a value of ma. The signal processing unit calculates a coefficient ma corresponding to at least two or more predetermined radial positions of the optical recording medium at the time of start-up adjustment, and at the time of seek, the signal processing unit is positioned at the radial position where the optical recording medium is recorded or reproduced. The optical disk apparatus according to claim 2, wherein the coefficient ma corresponding to the predetermined radius position close to the center is set. The signal processing unit calculates a coefficient ma corresponding to a predetermined radial position of the optical recording medium at the time of start adjustment, and at the time of seek, the radius position and coefficient of the optical recording medium calculated at the start adjustment. The optical disk apparatus according to claim 2, wherein a coefficient ma corresponding to a radial position to be recorded or reproduced is set based on an approximate expression that is a relationship with a value of ma. 6. The optical disc apparatus according to claim 5, wherein the approximate expression is a linear function or a quadratic function with the radial position of the optical recording medium as a variable. The divided light receiving element is divided into at least two parts in a predetermined direction on the optical recording medium, and both divided end parts are further divided into at least three parts in a direction perpendicular to the predetermined direction. An optical disc drive control method by an optical disc apparatus provided with a light detecting means for detecting return light from the optical recording medium,
When the signal processing unit performs recording or reproduction with respect to a predetermined recording layer of an optical recording medium having a plurality of layers, each of the light receiving element signals of the central divided light receiving element among the three divided light receiving elements is used. A first difference signal that is a difference and a second difference signal that is a difference between the sum signals of the light receiving element signals of the two divided light receiving elements at the end in the vertical direction among the three divided light receiving elements. And a tracking error signal based on a coefficient set based on the ratio of the slope of the DC offset according to the lens shift with respect to the predetermined direction, and for a predetermined recording layer of the optical recording medium When recording or reproducing data, the coefficient is set based on the radial position of the optical recording medium. A divided light receiving element that is divided into at least two in a predetermined direction on the optical recording medium, and that both divided ends are further divided into at least three in a direction perpendicular to the predetermined direction; An optical disc drive control method by an optical disc apparatus provided with a photodetector for detecting return light from the optical recording medium by a divided light receiving element,
The signal processor
A difference signal (A−D) that is a difference between the light receiving element signals A and D of the central divided light receiving element among the divided light receiving elements divided into at least three in the vertical direction of the both end parts, and the above-mentioned Of the divided light receiving elements divided into at least three in the vertical direction, the difference signal {() is the difference between the sum signals of the light receiving element signals B1 and B2, C1 and C2 of the two divided light receiving elements at the end in the vertical direction. B1 + B2) − (C1 + C2)} and a coefficient ma set based on the ratio of the slope of the DC offset corresponding to the lens shift with respect to the predetermined direction, the track error signal Tr is
Tr = (AD) -ma {(B1 + B2)-(C1 + C2)}
Execute the process to generate according to
In the above process, when recording or reproducing is performed on a predetermined recording layer of the optical recording medium, the coefficient ma is set based on a radial position of the recording medium. The signal processing unit calculates a coefficient ma corresponding to a predetermined radial position of the optical recording medium at the time of start adjustment, and at the time of seek, the radius position and coefficient of the optical recording medium calculated at the start adjustment. 9. The optical disc drive control method according to claim 8, wherein a coefficient ma corresponding to a radial position to be recorded or reproduced is set based on a relationship with a value of ma. The signal processing unit calculates a coefficient ma corresponding to at least two or more predetermined radial positions of the optical recording medium at the time of start-up adjustment, and at the time of seek, the signal processing unit is positioned at the radial position where the optical recording medium is recorded or reproduced. The optical disk drive control method according to claim 8, wherein the coefficient ma corresponding to the predetermined predetermined radial position is set. The signal processing unit calculates a coefficient ma corresponding to a predetermined radial position of the optical recording medium at the time of start adjustment, and at the time of seek, the radius position and coefficient of the optical recording medium calculated at the start adjustment. 9. The optical disc drive control method according to claim 8, wherein a coefficient ma corresponding to a radial position to be recorded or reproduced is set based on an approximate expression that is a relationship with a value of ma. 12. The optical disk drive control method according to claim 11, wherein the approximate expression is a linear function or a quadratic function with the radial position of the optical recording medium as a variable.

Images