JP2005078664A - Optical disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize stable track servo in accordance with variations in amplitude of a tracking error signal. <P>SOLUTION: In the case of coarse seek (YES in S5), a tracking error signal in coarse seek is measured (S10) and when the measured signal is larger than the prescribed signal level (YES in S10), the gain of the tracking signal is reduced (S11), and when the measured signal is smaller than the prescribed signal (NO in S10), the gain of the tracking error signal is raised (S12). Also in the case of fine seek (NO of S5), rack jump driving an objective lens is performed (S8). Then, the tracking error signal is measured (S10), when it is larger than the prescribed signal level (YES in S10), the gain of the tracking error signal is reduced (S11), when it is smaller (NO in S10), the gain of the tracking error signal is raised (S12). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus that records and reproduces information by irradiating an optical recording disc with a light beam as a light spot, and particularly relates to a technique that enables stable tracking servo.

  The optical disc apparatus is configured to irradiate a track on the recording surface of the optical disc to record / reproduce information. At the time of recording / reproduction, for example, as described in Patent Document 1, Track servo based on a tracking error signal is performed so that the spot appropriately follows a recorded track or an unrecorded track.

  In addition, in a read (playback) or write (record) command that occurs during normal operation, the seek operation that moves before the read (write) address (track) that operates the actual data is the current address and the target Depending on the distance to the address, a relatively low-precision and high-speed moving means, for example, a rough seek to move the carriage on which the optical pickup is mounted using a stepping motor, and a relatively high-precision and low-speed moving means, for example, the pickup objective lens This is executed in combination with a track jump, which is a precise seek to drive and finely move the light spot. When the light spot reaches the target track (target address), the seek operation ends. Even if the amplitude of the track error signal is remarkably changed at this position, the track servo is stabilized at the start of reading or writing.

  FIG. 5 is a flowchart of the operation related to the conventional seek control. In the seek operation, the current address on the disk is acquired by the control unit installed in the apparatus (S101), and the current address and the seek target address. To determine whether or not seek is necessary (S102), and calculates the number of tracks to be moved from the difference between the current address and the target address (S103).

  A relatively low-precision and high-speed moving means according to the seek distance, for example, a rough seek that moves the carriage using a stepping motor, and a relatively high-precision and low-speed moving means such as a pickup objective lens to drive the light spot It is determined whether to use a track jump, which is a precise seek to move.

Then, a peak / bottom hold circuit for measuring the peak and bottom values of the tracking error signal is initialized (S104), and if the determination result is a rough seek to move the carriage (YES in S105), the stepping motor is calculated from the number of tracks. The number of steps is converted into the number of steps (S106), and coarse seek is executed to move to a position near the target address (S107). If it is a precise seek (NO in S105), a precise seek for driving the objective lens is executed (S108).
JP 9-305977 A

  Incidentally, the amplitude gain of the tracking error signal is generally determined at the inner peripheral position of the optical disc, and the amplitude variation of the tracking error signal due to the disc position is absorbed by the gain margin in the track servo. In some cases, the amplitude fluctuation of the tracking error signal is remarkably large and cannot be absorbed by the track servo as in the prior art.

  An object of the present invention is to provide an optical disc apparatus that solves the above-described problems of the prior art and enables stable track servoing in response to amplitude fluctuations of a tracking error signal.

  In order to achieve the above object, an invention according to claim 1 is directed to an optical pickup for recording / reproducing information by irradiating a track on a recording surface of a recording disk with a light beam as a light spot; In an optical disc apparatus comprising means for moving the light spot in the radial direction and means for moving the light spot relatively large in the radial direction of the recording disk, the amplitude of the tracking error signal in the vicinity of the target track during recording / reproduction And an amplitude changing means for changing the amplitude of the detected tracking error signal to a preset signal level. With this configuration, the amplitude of the tracking error signal at the target position of the seek operation is provided. Even if there is a fluctuation, the track servo is stabilized at the start of recording / playback. Can.

  According to a second aspect of the present invention, in the optical disk apparatus according to the first aspect, the amplitude of the tracking error signal is detected during the track jump of the light spot during recording / reproduction. In the / reproduction command, the recording / reproduction operation can be performed without deteriorating the access time.

  According to a third aspect of the present invention, in the optical disk apparatus of the first aspect, the amplitude of the tracking error signal is detected during a rough seek in which the light spot moves relatively large in the radial direction of the recording disk during recording / reproduction. With this configuration, the recording / reproducing operation can be performed without deteriorating the access time in the recording / reproducing instruction.

  According to a fourth aspect of the present invention, there is provided an optical disc apparatus according to any one of the first to third aspects, further comprising a filter that removes a direct current component in the tracking error signal. Even if there is a lens shift in the objective lens, the amplitude of the tracking error signal can be accurately measured.

  According to the optical disk apparatus of the present invention, the track servo can be stabilized at the start of recording / reproduction even if the tracking error signal fluctuates at the target position of the seek operation. Realizes reliable track servoing that responds to fluctuations.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the overall configuration of an optical disk apparatus for explaining an embodiment of the present invention. 1 is an optical disk that is a recording disk, 2 is a spindle motor that rotationally drives the optical disk 1, and 3 is a spindle motor 2. A spindle motor control system 4 that performs drive control is a spindle motor control unit.

  An optical pickup 5 is mounted on the carriage 6 and can move in the radial direction of the optical disk 1. Further, the optical pickup 5 includes a light beam emitted from a laser diode as a light source as is well known. Is provided with an objective lens for irradiating the track on the recording surface of the optical disc as a light spot, and a lens actuator for driving the objective lens so that the light spot properly irradiates the track.

  7 is an actuator drive system for driving the lens actuator, 8 is a feed drive system for driving the carriage 6 for coarse seek movement, 9 is a servo control circuit for controlling the actuator drive system 7 and the feed drive system 8, and 10 is A signal detection system 11 for detecting various signals (RF signal, tracking signal, focus signal, etc.) at the time of reading / writing (reproducing / recording) in the optical pickup 5, 11 is a signal / detected from the optical disk 1 via the signal detection system 10. It is a data processing circuit that performs data error correction or data extraction operation.

  Reference numeral 12 denotes a central processing unit (CPU) that controls the entire optical disk apparatus, and reference numeral 13 denotes an external interface that transmits and receives commands and data to and from a host device such as an external personal computer.

  In FIG. 1, the actuator drive system 7 and the feed drive system 8 are driven and controlled by a servo control circuit 9 at the time of read / write to perform seek movement in the radial direction of the optical pickup 5, focus control of the objective lens, and tracking control. Thus, the light beam is favorably irradiated as a light spot to the target address on the optical disk 1. The optical pickup 5 reads recorded information from the optical disc 1 at the time of reading to obtain a read signal, and generates a recording pulse at the time of writing to record the information in a recording area (track) of the optical disc 1.

  The optical disk apparatus is in an idling state when there is no read or write command. When a read command is received, a read PLL (phase-locked loop) is pulled in, and the read is performed in consideration of a waiting time for stabilization in the servo control circuit 9. The seek operation by the actuator drive system 7 and the feed drive system 8 is executed up to the target address before the start address (track). This state is a tracking state, and reading is started when the read start address is read.

  When the write command is received, the spindle motor 2 is settled, the write PLL is pulled in, and the seek operation is performed up to the target address before the write start address in consideration of the waiting time for the servo control circuit 9 to become stable. Execute. This state is a tracking state, and writing is started when the write start address is read.

  The seek operation includes a relatively low-precision and high-speed moving means, for example, a rough seek for moving the carriage 6 using the stepping motor 2 according to the distance between the current address and the target address, and a relatively high-precision and low-speed moving means, for example, This is executed in combination with a track jump which is a precise seek to move the light spot by the objective lens of the optical pickup 5. When the light spot by the objective lens of the optical pickup 5 reaches the target address (target track), the seek operation ends.

  By the way, as shown in FIG. 3, when the tracking error signal amplitude varies significantly depending on the radial position on the optical disc, if the tracking operation is performed in this state, the tracking operation becomes impossible or tracking is possible. However, if the servo is weak, the tracking error will increase, and if the servo is too strong, it will oscillate. In either case, read performance is degraded if read, and write quality is degraded if written.

  For this reason, in this embodiment, a control system having a configuration as shown in FIG. 2 is provided, and a stable tracking state is ensured even when the amplitude of the tracking error signal varies significantly depending on the radial position on the optical disk. The operation flow as shown in FIG.

  FIG. 2 is a block diagram showing a configuration of a main part in the present embodiment, in which 20 is an amplifier, 21 is a high pass filter (HPF), 22 is a peak / bottom hold circuit, 24 and 25 are digital / analog converters, Reference numeral 26 denotes a comparator. Further, the servo control circuit 9 is provided with a phase compensation circuit 27, a gain compensation circuit 28, an actuator drive control circuit 29, and the like. Note that TE in the figure indicates a tracking error signal.

  FIG. 4 is a flowchart of the operation related to seek control in this embodiment. In the seek operation, the CPU 12 acquires an address on the current disk (S1), and calculates the distance between the current address and the seek target address. Whether or not seek is necessary is determined (S2), and the number of tracks to be moved is calculated from the difference between the current address and the target address (S3).

  Depending on the distance, a relatively low-precision and high-speed moving means, for example, a coarse seek that moves the carriage using a stepping motor, or a relatively high-precision and low-speed moving means such as a pickup objective lens is used to drive the light spot. It is determined whether it is a track jump that is a precise seek to be moved.

  Then, a peak / bottom hold circuit for measuring the peak and bottom values of the tracking error signal is initialized (S4), and if the determination result is a rough seek to move the carriage (YES in S5), the stepping motor is calculated from the number of tracks. The number of steps is converted (S6), and coarse seek is executed to move to a position near the target address (S7). At this time, if the moving distance is small, it is assumed that the target address is in the vicinity (S9), and the tracking error signal during the coarse seek is measured (S10). If the signal level is greater than the predetermined signal level (YES in S10), the gain of the tracking error signal is decreased (S11). If the signal level is smaller (NO in S10), the gain of the tracking error signal is determined. (S12).

  If the determination result is a precise seek (NO in S5), a precise seek (track jump) for driving the objective lens is executed (S8). Here, the tracking error signal is measured (S10), and if it is larger than the predetermined signal level (YES in S10), the gain of the track error signal is lowered (S11), and if it is smaller (NO in S10), the track error signal Is increased (S12).

  Then, the above operation is repeated until the magnitude is repeated in comparison with a predetermined signal level (S11 to S14), and the amplitude gain of the tracking error signal is determined. That is, in the measurement of the amplitude of the tracking error signal in step (S10), if there is a variation in the signal amplitude, the tracking signal has a gain width in setting the amplitude gain of the tracking signal, and thus does not necessarily match the target value. Therefore, in the present embodiment, when the signal levels are compared, the case where the comparison results alternate in steps (S11 to S14) is regarded as coincident with the target value, and the amplitude gain of the tracking error signal is determined. I am doing so. Then, seek is executed with the tracking error signal having the determined amplitude gain (S15 to S17).

  In this embodiment, the tracking error signal gain control in the seek control as described above allows the tracking error signal amplitude at the target position to be a constant level even if the amplitude of the tracking error signal varies depending on the position in the disk radial direction. Therefore, tracking servo can be applied stably.

  During the track jump, a lens shift occurs because the objective lens of the optical pickup 5 moves in a direction crossing the track. Due to this lens shift, the tracking error signal has a DC (direct current) correlated with the lens shift. ) Component is superimposed.

  Therefore, in this embodiment, as shown in FIG. 2, a high-pass filter (HPF) 21 is provided, and the amplitude of the tracking error signal from which the DC component is removed through the HPF 21 is measured. However, the amplitude of the tracking error signal can be accurately measured.

  The present invention is applied to an optical disc apparatus that records / reproduces information by irradiating a light spot to an optical recording disc such as a CD, DVD, CD-R, CD-RW, etc., and particularly a tracking servo system thereof. It is effective for use.

1 is a block diagram showing the overall configuration of an optical disc apparatus for explaining an embodiment of the present invention. The block diagram which shows the structure of the principal part in this embodiment. Explanatory diagram showing the difference in tracking error signal amplitude depending on the radial position of the disk Flowchart of operation related to seek control in this embodiment Flowchart of operation related to seek control in a conventional optical disc apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 5 Optical pick-up 6 Carriage 7 Actuator drive system 8 Feed drive system 9 Servo control circuit 10 Signal detection system 11 Data processing circuit 12 Central processing unit (CPU)
21 High-pass filter (HPF)
22 Peak / Bottom Hold Circuit 27 Phase Compensation Circuit 28 Gain Compensation Circuit 29 Actuator Drive Control Circuit

Claims (4)

An optical pickup for recording / reproducing information by irradiating a light beam as a light spot to a track on a recording surface of the recording disk; means for minutely moving the light spot in a radial direction of the recording disk; In an optical disc apparatus comprising means for moving the light spot relatively large in the radial direction,
An optical disc apparatus comprising amplitude changing means for detecting the amplitude of a tracking error signal in the vicinity of a target track during recording / reproduction and changing the detected amplitude of the tracking error signal to a preset signal level.   2. The optical disc apparatus according to claim 1, wherein the amplitude of the tracking error signal is detected during a track jump of the light spot during recording / reproduction.   2. The optical disk apparatus according to claim 1, wherein the amplitude of the tracking error signal is detected during a rough seek in which the light spot moves relatively greatly in the radial direction of the recording disk during recording / reproduction.   4. The optical disk apparatus according to claim 1, further comprising a filter that removes a direct current component in the tracking error signal.

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