JP2006053969A - Disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disk device preventing the quality of a reproducing/recording signal from being degraded caused by steady defocusing. <P>SOLUTION: A laser beam emitted from a laser diode 22 is applied to the recording surface of a magneto-optical disk 62 by an optical lens 14. An FE signal detection circuit 36 detects the shifting amount of the optical lens 14 from a focal point based on the laser beam reflected on the recording surface. A focus control circuit 38 outputs a control voltage having a voltage value corresponding to the detected shifting amount. The output voltage value of the control voltage is added to the voltage value of an offset voltage set in a register 42 by an adder 40. The optical lens 14 is arranged in the position of an optical axis direction corresponding to the control voltage output from the adder 40. The control voltage output from the adder 40 is smoothed by an LPF 46. A CPU 54 updates the votlage value of the offset voltage set in the register 42 based on a difference value between the smoothed voltage value and a reference voltage value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a disk device, and more particularly to a disk device that irradiates a recording surface of a disk recording medium with laser light through an optical lens.

An example of a conventional device of this type is disclosed in Patent Document 1. According to this prior art, an offset value that maximizes the amplitude of a TE (Tracking Error) signal is set in the register when performing a seek process, and the amplitude of an RF (Radio Frequency) signal when performing an RF signal decoding process. Is set in the register. The focus servo system performs focus control in consideration of the offset value set in the register. As a result, it is possible to accurately detect a signal that is noticed in each of the different operating states.
JP 2002-157755 A [G11B 7/09]

    However, in the prior art, the offset value is not changed according to the warp of the disk. Then, when a disc having warpage is reproduced, defocus corresponding to the reproduction position appears as a steady deviation. The quality of the reproduction signal decreases due to this steady deviation.

    SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a disc device that can prevent a reduction in quality of a reproduction signal / recording signal due to steady defocusing.

  The disk device according to the present invention includes a generating means for generating laser light, an optical lens for irradiating the recording surface of the disk recording medium with the laser light generated by the generating means, and an optical axis direction based on the laser light reflected by the recording surface Detecting means for detecting the amount of deviation of the position of the optical lens from the in-focus position, output means for outputting a control voltage having a voltage value corresponding to the amount of deviation detected by the detecting means, and output voltage means for the voltage value of the offset voltage. Adding means for adding to the voltage value of the output control voltage, arrangement means for arranging the optical lens at a position in the optical axis direction corresponding to the control voltage output from the adding means, and smoothing the control voltage output from the adding means Smoothing means and updating means for updating the voltage value of the offset voltage with the difference value between the voltage value smoothed by the smoothing means and the reference voltage value. That.

  The laser beam generated by the generating unit is irradiated onto the recording surface of the disk recording medium by the optical lens. The detecting means detects a deviation amount from the focal point of the position of the optical lens in the optical axis direction based on the laser light reflected by the recording surface, and the output means has a voltage value corresponding to the detected deviation amount. Outputs control voltage. The voltage value of the output control voltage is added to the voltage value of the offset voltage by the adding means. The optical lens is arranged by the arranging unit at a position in the optical axis direction corresponding to the control voltage output from the adding unit. The control voltage output from the adding means is also smoothed by the smoothing means. The update means updates the voltage value of the offset voltage with the difference value between the voltage value smoothed by the smoothing means and the reference voltage value.

  The offset voltage indicates a voltage value corresponding to the defocus amount. The optical lens is disposed at a position on the optical axis corresponding to the control voltage in consideration of the voltage value of the offset voltage. As a result, a voltage corresponding to the defocus amount is removed from the control voltage generated by the generation unit. The focus approaches the in-focus point. As a result, deterioration of the quality of the reproduction signal or recording signal is prevented.

  The disc device according to the invention of claim 2 is dependent on claim 1, and the reference voltage value is a voltage value necessary for disposing the optical lens at a reference position in the optical axis direction.

  According to a third aspect of the present invention, there is provided a disc apparatus according to the first or second aspect, further comprising generating means for generating a reproduction signal based on the laser beam reflected by the recording surface.

  According to the present invention, the offset voltage indicates a voltage value corresponding to the defocus amount. The optical lens is disposed at a position on the optical axis corresponding to the control voltage in consideration of the voltage value of the offset voltage. As a result, a voltage corresponding to the defocus amount is removed from the control voltage generated by the generation unit. The focus approaches the in-focus point. As a result, deterioration of the quality of the reproduction signal or recording signal is prevented.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

  Referring to FIG. 1, an optical disc apparatus 10 of this embodiment includes an optical pickup (optical system) 12 provided with an optical lens 14. The optical lens 14 is supported by a tracking actuator 16, a tilt actuator 18 and a focus actuator 20. The laser light emitted from the laser diode 22 is irradiated onto a recording surface of a magneto-optical disk 56 such as an ASMO (Advanced Storage Magneto Optical disc) through the optical system components shown in FIG. The magneto-optical disk 62 is mounted on a spindle 64 and is rotated by a spindle motor 66. The magneto-optical disk 62 is a ZCLV (Zone Constant Linear Velocity) disk, and the rotational speed decreases as the optical pickup 12 moves from the inner periphery to the outer periphery.

  The laser light emitted from the laser diode 22 is split by a grating (not shown). Thus, one main beam M and two sub beams S1 and S2 are generated. The generated beams M, S1, and S2 are converged by the optical lens 14 and then irradiated onto the recording surface of the magneto-optical disk 56 in the manner shown in FIG. The main beam M is applied to a desired track, and the sub beams S1 and S2 are applied to adjacent tracks on both sides of the desired track. Note that convex land tracks and concave groove tracks are alternately formed on the recording surface of the magneto-optical disk 56. “L” and “G” shown in FIG. 2 mean a land track and a groove track, respectively.

  The main beam M and the sub beams S1 and S2 reflected by the recording surface pass through the optical lens 14, and are further split by a Wollaston prism (not shown). The main beam M is split into beams Ma, Mb and Mc, the sub-beam S1 is split into S1a, S1b and S1c, and the sub-beam S2 is split into S2a, S2b and S2c. The beam Ma has the same components as the main beam M, but the beams Mb and Mc have only the vertical deflection component and the horizontal deflection component of the main beam M, respectively. The same applies to sub-beams S1 and S2, where beam S1a (S2a) has the same components as sub-beam S1 (S2), but beams S1b (S2b) and S1c (S2c) are It has only a horizontal deflection component.

  The photodetector 22 is configured as shown in FIG. The beam Ma is detected by the detection elements 22a to 22d, and the beams Mb and Mc are detected by the detection elements 22i and 22j, respectively. On the other hand, the beam S1a is detected by the detection elements 22e and 22f, and the beam S2a is detected by the detection elements 22g and 22h. On the other hand, beams 1b, 1c, 2b and 2c are not detected by any of the detection elements.

  Returning to FIG. 1, the TE signal detection circuit 26 performs an operation according to Equation 1 on the outputs of the detection elements 22a to 22h, and generates a TE signal by a DPP (Differential Push Pull) method. Further, the FE signal detection circuit 36 performs an operation according to Equation 2 on the outputs of the detection elements 22a to 22d to detect an FE (Focus Error) signal. Further, the RF signal detection circuit 48 performs an operation according to Equation 3 on the outputs of the detection elements 22i and 22j to detect the RF signal. Note that “A” to “J” in Equations 1 to 3 correspond to the outputs of the detection elements 22a to 22j, respectively.

  The tracking control circuit 28 performs a seek process or a tracking control process based on the TE signal output from the TE signal detection circuit 26, and generates a sled motor control voltage and a tracking actuator control voltage. The PWM modulation circuit 30 generates a PWM signal having a pulse width corresponding to the thread motor control voltage, and applies the generated PWM signal to the thread motor 34. The PWM modulation circuit 32 generates a PWM signal having a pulse width corresponding to the tracking actuator control voltage, and supplies the generated PWM signal to the tracking actuator 16. The rotational speed and direction of the sled motor 34 and the radial position of the optical lens 14 are controlled by such a tracking servo system.

  The focus control circuit 38 generates a focus actuator control voltage based on the FE signal output from the FE signal detection circuit 36, and supplies the generated focus actuator control voltage to the adder 40. On the other hand, the register 42 is set with a voltage value of an offset voltage. The adder 40 adds the voltage value of the offset voltage set in the register 42 to the voltage value of the focus actuator control voltage given from the focus control circuit 38.

  The focus actuator control voltage having the added voltage value is supplied to the PWM modulation circuit 44. The PWM modulation circuit 44 generates a PWM signal having a pulse width corresponding to the focus actuator control voltage, and supplies the generated PWM signal to the focus actuator 20. The focus, that is, the position of the optical lens 14 in the optical axis direction is adjusted by such a focus servo system.

  The focus actuator control voltage output from the adder 40 is also supplied to the LPF 46. The LPF 46 smoothes the focus actuator control voltage and applies the smoothed voltage Vav to the CPU 54. The CPU 54 calculates a difference value Vdif between the applied smoothing voltage Vav and the reference voltage value Vref (= 2.5 V), and updates the voltage value of the current offset voltage with the calculated difference value Vdif.

  The ECC decoder 50 performs a decoding process on the RF signal output from the RF signal detection circuit 48 to generate a reproduction signal. The RF signal is also subjected to jitter detection processing by the jitter detection circuit 52. The CPU 54 gives a correction command to the tilt correction circuit 56 so that the jitter detected by the jitter detection circuit 52 decreases. The tilt correction circuit 56 generates a tilt actuator control voltage according to the correction command. The PWM modulation circuit 58 generates a PWM signal having a pulse width corresponding to the generated tilt actuator control voltage, and supplies the generated PWM signal to the tilt actuator 18. The tilt, that is, the direction of the optical lens 14 is adjusted by such a tilt servo system.

  When updating the voltage value of the offset voltage set in the register 42, the CPU 54 executes processing according to the flowchart shown in FIG. The control program corresponding to this flowchart is stored in the flash memory 60. First, in step S1, the smoothed voltage Vav output from the LPF 46 is captured. In the subsequent step S3, a difference value Vdif (= Vav−Vref) between the captured smoothing voltage Vav and the reference voltage value Vref is calculated. In step S5, the calculated difference value Vdif is written in the register 42. The voltage value of the offset voltage set in the register 42 is updated with the difference value Vdif.

  When the optical lens 14 is moved in the radial direction of the magneto-optical disk 62 in the order of position A → position B → position C in a state where the magneto-optical disk 62 is warped as shown in FIG. The voltage value of the set offset voltage is updated in the order of 0 → ΔF1 → ΔF1 + ΔF2. The operation at this time will be described with reference to FIGS. 6 (A) to 6 (C), FIGS. 7 (A) to 7 (C), and FIGS. 8 (A) to 8 (C).

  6A to 6C show temporal changes in the focus actuator control voltage, and FIGS. 7A to 7C show changes in the focus actuator control voltage with respect to the position of the optical lens 14. 8A to 8C show changes in the level of the FE signal with respect to the position of the optical lens 14.

  When the focus control at the position A is not affected at all by the warp, the focus actuator control voltage changes around the reference voltage value Vref as shown in FIG. At this time, the offset voltage value of the register 42 indicates “0”. The focus is adjusted aiming at a focal point FP0 (reference position) shown in FIG. 7A or FIG. 8A.

  Note that the voltage value of the focus actuator control voltage corresponding to the in-focus FP0 corresponds to the reference voltage value Vref. 6A to 6C are caused by surface wobbling of the magneto-optical disk 62. FIG.

  When the optical lens 14 is moved from the position A to the position B, the focus control is affected by the warp, and defocus corresponding to “DF1” occurs in the optical axis direction of the optical lens 14. As shown in FIG. 6B, the focus actuator control voltage changes around a voltage value Vav1 higher than the reference voltage value Vref. The focus cannot reach the focal point FP1 shown in FIG. 7B or FIG. 8B, and changes around the non-focus point P1. When such defocus DF1 occurs, the offset voltage value of the register 42 is updated from “0” to “ΔF1”.

  By updating the offset voltage value, the out-of-focus P1 shown in FIG. 7B is the intersection of the vertical axis that defines the focus actuator control voltage output from the adder 40 and the horizontal axis that defines the position of the optical lens 14. It becomes. The focal point FP1 on the graph shown in FIG. 8B moves toward the origin. As a result, the focus further approaches the in-focus FP1 from the non-in-focus P1.

  When the optical lens 14 moves from the position B to the position C, the focus control is further affected by the warp. In the state where the offset voltage corresponding to “ΔF1” is applied, defocus corresponding to “DF2” occurs in the optical axis direction of the optical lens 14. The focus actuator control voltage changes around a voltage value Vav2 higher than the voltage value Vav1 as shown in FIG. 6C. The focus cannot reach the focal point FP2 shown in FIG. 7C or FIG. 8C, and changes around the non-focus point P2. When such defocus DF2 occurs, the offset voltage value of the register 42 is updated from “ΔF1” to “ΔF1 + ΔF2”.

  By updating the offset voltage value, the out-of-focus point P2 shown in FIG. 7C is the intersection of the vertical axis that defines the focus actuator control voltage output from the adder 40 and the horizontal axis that defines the position of the optical lens 14. It becomes. The focal point FP2 on the graph shown in FIG. 8C moves toward the origin. As a result, the focus further approaches the in-focus point FP2 from the non-in-focus point P2.

  As can be seen from the above description, the laser light emitted from the laser diode 22 is irradiated onto the recording surface of the magneto-optical disk 62 by the optical lens 14. The FE signal detection circuit 36 detects the amount of deviation from the focal point of the optical lens 14 based on the laser light reflected by the recording surface. The focus control circuit 38 outputs a focus actuator control voltage having a voltage value corresponding to the detected deviation amount.

  The output voltage value of the focus actuator control voltage is added by the adder 40 with the voltage value of the offset voltage set in the register 42. The optical lens 14 is disposed by the focus actuator 20 at a position in the optical axis direction corresponding to the focus actuator control voltage output from the adder 40.

  The focus actuator control voltage output from the adder 40 is also smoothed by the LPF 46. The CPU 54 updates the voltage value of the offset voltage set in the register 42 with the difference value between the smoothed voltage value and the reference voltage value.

  The offset voltage indicates a voltage value corresponding to the defocus amount. The optical lens 14 is disposed at a position on the optical axis corresponding to the focus actuator control voltage in consideration of the voltage value of the offset voltage. As a result, the voltage corresponding to the defocus amount is removed from the focus actuator control voltage output from the focus control circuit 38, and the optical lens 14 approaches the focal point. Thereby, the quality of the reproduction signal output from the ECC decoder 50 is improved.

  Although the reproducing operation has been described in this embodiment, the present invention can also be applied to a recording operation. In this embodiment, ASMO is adopted as a disk recording medium, but a DVD (Digital Versatile Disc) may be adopted instead.

It is a block diagram which shows the structure of one Example of this invention. It is an illustration figure which shows the state in which the main beam and the sub beam are irradiated to the recording surface. It is an illustration figure which shows an example of a structure of the photodetector applied to the FIG. 1 Example. It is a flowchart which shows a part of operation | movement of CPU applied to the FIG. 1 Example. It is an illustration figure which shows an example of the focus control operation | movement of the optical lens applied to the FIG. 1 Example. (A) is a waveform diagram showing an example of a change in the focus actuator control voltage at the position A shown in FIG. 5, and (B) is a waveform showing an example of a change in the focus actuator control voltage at the position B shown in FIG. FIG. 6C is a waveform diagram illustrating an example of a change in the focus actuator control voltage at the position C illustrated in FIG. 5. (A) is a graph showing a part of the focus control operation at the position A shown in FIG. 5, and (B) is a graph showing a part of the focus control operation at the position B shown in FIG. ) Is a graph showing a part of the focus control operation at the position C shown in FIG. (A) is a graph showing another part of the focus control operation at the position A shown in FIG. 5, and (B) is a graph showing another part of the focus control operation at the position B shown in FIG. FIG. 6C is a graph showing another part of the focus control operation at the position C shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Disk apparatus 12 ... Optical pickup 14 ... Optical lens 26 ... TE signal detection circuit 36 ... FE signal detection circuit 42 ... Register 48 ... RF signal detection circuit 50 ... ECC decoder 54 ... CPU

Claims (3)

Generating means for generating laser light,
An optical lens for irradiating a recording surface of a disk recording medium with laser light generated by the generating means;
Detecting means for detecting an amount of deviation from the focal point of the position of the optical lens in the optical axis direction based on the laser light reflected by the recording surface;
Output means for outputting a control voltage having a voltage value corresponding to the amount of deviation detected by the detection means;
Adding means for adding the voltage value of the offset voltage to the voltage value of the control voltage output by the output means;
Disposing means for disposing the optical lens at a position in the optical axis direction corresponding to the control voltage output from the adding means;
A disk device comprising: smoothing means for smoothing the control voltage output from the adding means; and updating means for updating the voltage value of the offset voltage with a difference value between the voltage value smoothed by the smoothing means and a reference voltage value .   The disk device according to claim 1, wherein the reference voltage value is a voltage value necessary for disposing the optical lens at a reference position in an optical axis direction.   The disk apparatus according to claim 1, further comprising a generation unit that generates a reproduction signal based on the laser beam reflected by the recording surface.

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