JP2005085352A - Tracking control method and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tracking control method for performing stable tracking servo even at the boundary part between a recorded area and an unrecorded area. <P>SOLUTION: The difference between a (signal TR+) and a (signal TR-) is obtained and an offset (TEOFS) is injected so that the center of the difference signal reaches a reference voltage in a track-off state, thereby generating a TE signal. A Peak detecting circuit 12 detects the peak level of the TE signal, a Bottom detecting circuit 12 detects the bottom level of the TE signal, and a low-pass filter circuit 13 detects the DC level of the TE signal. The difference between a signal FE+ and a signal FE- is obtained and an offset (FEOFS) is injected so that a focus position can be changed to an arbitrary position, thereby generating a FE signal. At a recorded/unrecorded boundary, focus control is performed so that the level of a tracking error signal in a track jump state is an intermediate level between the peak level and bottom level, thereby adjusting the offset quantity of the tracking error signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus for recording / reproducing information on an optical disc by an optical pickup.

  As optical disc devices, audio CDs, CD-ROMs, CD-R / RWs, DVDs, and the like have already been put into practical use, and application to various fields and development for high performance are being actively conducted. . Particularly recently, with the rapid market expansion of personal computers, the penetration rate of built-in optical disk devices in personal computers has increased.

  In an optical disc apparatus, in order to accurately record or reproduce information, it is necessary that the laser light applied to the optical disc accurately follows the track of the optical disc. This control is performed by generating a tracking error signal and controlling the tracking actuator based on the tracking error signal.

  In addition, it is necessary for the laser light applied to the optical disc to be properly focused on the reflecting surface of the optical disc, and for that purpose, means for controlling the distance between the objective lens that collects the laser light and the optical disc is important. It becomes. This control is performed by generating a focus error signal and controlling the focus actuator based on the focus error signal.

  Here, the focus error signal is a signal indicating a deviation in the focal direction between the light beam spot emitted from the objective lens provided in the optical pickup and the recording surface of the optical disc. The tracking error signal is a signal indicating a deviation in the optical disc radial direction between the light spot and the information track of the optical disc.

  The configuration of the optical disc apparatus will be described with reference to FIG.

  In FIG. 1, an optical disc apparatus irradiates an optical disc 1 with laser light and receives light reflected by the optical disc 1, and converts the reflected light from the optical disc 1 obtained by the optical pickup 2 into a current. , A detector 3 for outputting a signal for reading data from the optical disc 1, an output signal for detecting a focus error, and an output signal for detecting a tracking error, and an output signal output from the detector 3, from which a tracking error signal (hereinafter referred to as an error signal) And a signal calculation unit 4 that generates a focus error signal (hereinafter sometimes abbreviated as “FE signal”).

  The TE signal and the FE signal are input from the signal calculation unit 4 to a digital servo processor (hereinafter abbreviated as “DSP”) 7. The DSP 7 controls the tracking actuator 6 that drives the optical pickup 2 so that the optical pickup 2 follows the track of the optical disc 1 on the basis of the TE signal, and between the objective lens provided in the optical pickup 2 and the optical disc 1. The focus actuator 5 is controlled so that the distance between them is appropriate.

  The above processing of the DSP 7 is executed under the control of the CPU 8.

  A means for generating a tracking error signal and a focus error signal from the output signal output from the detector 3 will be described with reference to FIGS.

  FIG. 5 shows tracking control by the push-pull method, and shows an operation of irradiating the pit 22 formed on the track center 21 of the optical disc with laser light and receiving the reflected light from the pit 22 by the detectors 24 and 25. Thus, half of the spot 23 of the laser light is received by the detector 24 and the other half of the spot 23 is received by the detector 25. The detector 24 obtains a signal TR +, and the detector 25 obtains a signal TR-.

  A difference is made in the circuit shown in FIG. 6 between TR + and TR− obtained in this way, and an TE signal is generated by injecting an offset (TEOFS) so as to be a reference voltage in the track-off state.

There are various techniques for accurately performing tracking control. For example, a technique for stably performing tracking control at the time of track jump is described in (Patent Document 1).
JP-A-6-150343

  The tracking control has the following problems when performing a track jump at the boundary between the recorded area and the unrecorded area of the optical disc. The TE signal at the boundary between the recorded area and the unrecorded area will be described with reference to FIGS.

  FIG. 7 shows the operation in which the detectors 24 and 25 receive the reflected light from the pit 22 by irradiating the laser beam onto the pit 22 formed on the track center 21 which is the boundary between the recorded area and the unrecorded area of the optical disc. The half of the laser beam spot 23 is received by the detector 24, and the other half of the spot 23 is received by the detector 25. The detector 24 obtains a signal TR +, and the detector 25 obtains a signal TR-.

  FIG. 8A shows a condensing state of the laser beam when the spot 23 shown in FIG. 7A is formed, and FIG. 9A shows a waveform of the TE signal at this time. Further, FIG. 8B shows a condensing state of the laser beam when the spot 23 shown in FIG. 7B is formed, and FIG. 9B shows a waveform of the TE signal at this time. Similarly, FIG. 8C shows a condensing state of the laser light beam when the spot 23 shown in FIG. 7C is formed, and FIG. 9C shows the waveform of the TE signal at this time.

  Although the spot diameter is large in FIG. 7A, this is because, as shown in FIG. 8A, the laser light beam 32 collected by the objective lens 31 focuses on the optical disc 1 above. It is. When the laser beam is applied to the position where the pit is formed, the amount of reflected light is reduced. However, in the case shown in FIG. 8A, the TR + signal is reduced due to the influence of the recorded area. As a result, the waveform of the TE signal shown in FIG. 9A is distorted at the boundary between the recorded area and the unrecorded area.

  Although the spot diameter is small in FIG. 7B, this is because the laser light beam 32 collected by the objective lens 31 is focused at the position of the optical disc 1 as shown in FIG. 8B. It is. In this case, since the laser beam is sufficiently focused on the reflection surface of the optical disk, neither TR + signal nor TR− signal is lowered due to the influence of the recorded area. As a result, the waveform of the TE signal shown in FIG. 9B does not cause waveform distortion at the boundary between the recorded area and the unrecorded area.

In FIG.7 (c), the spot diameter is large, but as shown in FIG.8 (c),
This is because the laser beam 32 condensed by the objective lens 31 is focused below the optical disc 1. When the laser beam is applied to the position where the pit is formed, the amount of reflected light is reduced, but in the case shown in FIG. 8C, the TR-signal is reduced due to the influence of the recorded area. As a result, the waveform of the TE signal shown in FIG. 9C causes waveform distortion at the boundary between the recorded area and the unrecorded area.

  Thus, at the boundary between the recorded area and the unrecorded area, the amount of reflected light is affected by the spread of the spot diameter of the laser light applied to the position where the pits 22 are formed, and the light received by the detectors 24 and 25. The level fluctuates and the TE signal is distorted. Therefore, the TE signal is extremely offset at the boundary between the recorded area and the unrecorded area, the recording characteristics and the reproduction characteristics are deteriorated, and in the worst case, the tracking servo is not applied. In particular, at the time of recording, since the drive is always controlled at the boundary between the recorded area and the unrecorded area, the control tends to be unstable, and the tracking control is broken.

  The present invention has been made to solve the above problems, and provides a tracking control method capable of applying stable tracking servo even at the boundary between a recorded area and an unrecorded area. An object of the present invention is to provide an optical disc apparatus with improved recording / reproduction quality using a tracking control method.

  The present invention has been made in order to solve the above-described problem, and when the optical pickup is moved to the boundary between the recorded area and the unrecorded area of the optical disc and the still operation is performed, the peak level of the tracking error signal is obtained. And the bottom level and the DC level are measured, and the focus error control is performed so that the level of the tracking error signal in the track jump state is an intermediate level between the peak level and the bottom level. It is a tracking control method characterized by adjusting.

  According to the present invention, since the focus control is performed so that the level of the tracking error signal in the track jump state is an intermediate level between the peak level and the bottom level, at the boundary between the recorded area and the unrecorded area, The spot diameter of the laser beam irradiated to the position where the pit is formed spreads due to a shift in the focus direction, so that the amount of reflected light is affected and the light reception level of the detector fluctuates to cause distortion in the tracking error signal. This can be prevented. Therefore, stable tracking servo can be applied even at the boundary between the recorded area and the unrecorded area.

  According to the present invention, at the boundary between the recorded area and the unrecorded area, the spot diameter of the laser beam irradiated to the position where the pit is formed spreads due to the shift in the focus direction, so that the amount of reflected light is affected. As a result, it is possible to prevent the tracking error signal from being distorted due to fluctuations in the light receiving level of the detector. Therefore, stable tracking servo can be applied even at the boundary between the recorded area and the unrecorded area, and the recording / reproducing quality can be improved.

According to the first aspect of the present invention, when the optical pickup is moved to the boundary between the recorded area and the unrecorded area of the optical disc and the still operation is performed, the peak level, bottom level, and DC level of the tracking error signal are detected. And the focus error control is performed so that the level of the tracking error signal in the track jump state is an intermediate level between the peak level and the bottom level, and the offset amount of the tracking error signal is adjusted. This is a tracking control method.

  According to the present invention, since the focus control is performed so that the level of the tracking error signal in the track jump state is an intermediate level between the peak level and the bottom level, at the boundary between the recorded area and the unrecorded area, The spot diameter of the laser beam irradiated to the position where the pit is formed spreads due to a shift in the focus direction, so that the amount of reflected light is affected and the light reception level of the detector fluctuates to cause distortion in the tracking error signal. This can be prevented. Therefore, stable tracking servo can be applied even at the boundary between the recorded area and the unrecorded area.

  According to a second aspect of the present invention, in the tracking control method according to the first aspect, the focus control is performed by adding or subtracting a focus offset correction value depending on whether the offset amount of the tracking error signal is positive or negative. Features.

  According to the present invention, by adding or subtracting the focus offset correction value according to whether the tracking error signal offset amount is positive or negative, the tracking error signal offset amount can be within the optimum range, and the tracking error signal waveform Distortion can be corrected appropriately.

  According to a third aspect of the present invention, a peak detection circuit for measuring a peak level of a tracking error signal when a still operation is performed by moving an optical pickup to a boundary portion between a recorded area and an unrecorded area of an optical disk. And a bottom detection circuit that measures the bottom level of the tracking error signal, and a low-pass filter circuit that measures the DC level of the tracking error signal, and the level of the tracking error signal in the track jump state is the peak level An optical disc apparatus comprising a signal calculation unit that adjusts an offset amount of a tracking error signal by performing focus control so as to be an intermediate level from a bottom level.

  According to the present invention, the signal calculation unit that adjusts the offset amount of the tracking error signal by performing the focus control so that the level of the tracking error signal in the track jump state is an intermediate level between the peak level and the bottom level. As a result, the spot diameter of the laser beam applied to the position where the pits are formed at the boundary between the recorded area and the unrecorded area is widened due to a shift in the focus direction, which affects the amount of reflected light. As a result, it is possible to prevent the tracking error signal from being distorted due to fluctuations in the light receiving level of the detector. Therefore, it is possible to realize an optical disc apparatus capable of performing stable tracking servo even at the boundary between the recorded area and the unrecorded area.

  According to a fourth aspect of the present invention, in the optical disk device according to the third aspect, the signal calculation unit has an offset amount calculation unit for calculating an offset amount of the tracking error signal, and is obtained by the offset amount calculation unit. And a focus offset correction unit for adding or subtracting a focus offset correction value according to the sign of the offset amount of the tracking error signal.

  According to the present invention, by adding or subtracting the focus offset correction value according to whether the tracking error signal offset amount is positive or negative, the tracking error signal offset amount can be within the optimum range, and the tracking error signal waveform An optical disc apparatus capable of appropriately correcting the distortion can be realized.

(Embodiment 1)
The configuration of the optical disc apparatus according to the embodiment of the present invention will be described with reference to FIG.

  In FIG. 1, the optical disk apparatus according to the present embodiment includes an optical pickup 2 that irradiates an optical disk 1 with laser light and receives light reflected by the optical disk 1, and a reflection from the optical disk 1 obtained by the optical pickup 2. A detector 3 that converts light into current and outputs a signal for reading data from the optical disc 1, an output signal for detecting a focus error, and an output signal for detecting a tracking error; and a tracking error signal output from the detector 3; The signal calculation unit 4 generates a focus error signal.

  The TE signal and the FE signal are input from the signal calculation unit 4 to the digital servo processor (DSP) 7. The DSP 7 controls the tracking actuator 6 that drives the optical pickup 2 so that the optical pickup 2 follows the track of the optical disc 1 on the basis of the TE signal, and between the objective lens provided in the optical pickup 2 and the optical disc 1. The focus actuator 5 is controlled so that the distance between them is appropriate.

  The above processing of the DSP 7 is executed under the control of the CPU 8.

  A means for generating a tracking error signal and a focus error signal from the output signal output from the detector 3 will be described with reference to FIG.

  FIG. 2A shows a signal TR + obtained by irradiating a pit 22 formed on the track center 21 of the optical disk shown in FIG. 5 with a laser beam and receiving the reflected light from the pit 22 by the detectors 24 and 25. FIG. 2 shows a configuration of a circuit having means for generating a TE signal from a signal TR− and adjusting the waveform of the TE signal. FIG.

  In FIG. 2A, the signal TR + obtained by receiving half of the laser beam spot 23 shown in FIG. 5 by the detector 24 and the other half of the spot 23 received by the detector 25 are obtained. For the signal TR−, the difference is taken, and an TE signal is generated by injecting an offset (TEOFS) so that the center of the difference signal becomes the reference voltage in the track-off state.

  Further, a Peak detection circuit 11, a Bottom detection circuit 12, and a low-pass filter circuit 13 are provided. The Peak detection circuit 11 detects the peak level of the TE signal, and the Bottom detection circuit 12 detects the bottom level of the TE signal. The low-pass filter circuit 13 detects the DC level of the TE signal.

  FIG. 2B shows the difference between the signal FE + and the signal FE− obtained by irradiating the pits 22 formed on the track center 21 of the optical disk shown in FIG. A configuration of a circuit that generates an FE signal by injecting an offset (FEOFS) so as to be changed is shown.

  FIG. 3 shows an example of the waveform of the TE signal when a track jump occurs at the boundary between the recorded area and the unrecorded area. As described with reference to FIGS. 7 to 9, the recorded area of the optical disk is shown in FIG. There is a waveform distortion due to the laser beam being applied to the boundary between the unrecorded area and the unrecorded area. That is, the amplitude in the recorded area is different from the amplitude in the unrecorded area.

  The Peak detection circuit 11 shown in FIG. 2A detects such a peak level in the TE signal, the Bottom detection circuit 12 detects the bottom level of the TE signal, and the low-pass filter circuit 13 detects the DC level of the TE signal. It is to detect.

  Based on FIG. 4, a process for correcting the focus offset and adjusting the offset amount of the TE signal to correct the distortion of the waveform of the TE signal using the circuit shown in FIG. 2 will be described.

  The process of adjusting the offset amount of the TE signal described below is executed by the signal calculation unit 4.

After the optical pickup is moved to the boundary between the recorded area and the unrecorded area (S1), the detection circuit is initialized to measure the DC level of the TE signal (S2), the track jumps (S3), and the TE signal The peak level and the bottom level are measured (S4). Based on the measured DC level, peak level, and bottom level,
An offset amount (ofs) is obtained by calculating an offset amount (ofs) = (peak level−bottom level) / 2−DC level (S5). It is determined whether the offset amount (ofs) is positive (S6). As a result, if ofs> 0, focus offset correction processing for adding the focus offset correction amount α is performed (S7), and the above-described processing is performed. repeat.

  On the other hand, if not ofs> 0, it is determined whether the offset amount (ofs) is negative (S8). As a result, if ofs <0, focus offset correction processing for reducing the focus offset correction amount α is performed. (S9), the above-described processing is repeated. In this way, control is performed so that the offset amount (ofs) becomes zero, and the distortion of the waveform of the TE signal is corrected.

  As a result of the above processing, as shown in FIGS. 8A and 8C, even when the focal position of the laser beam 32 condensed by the objective lens 31 is deviated, the focus offset correction amount. By performing a focus offset correction process that adds or subtracts α, an appropriate focus position can be obtained as shown in FIG. As a result, the laser beam is sufficiently focused on the reflection surface of the optical disc, and the signal level of both the TR + signal and the TR− signal does not decrease due to the influence of the recorded area. As a result, TE signal waveform distortion can be prevented from occurring at the boundary between the recorded area and the unrecorded area, and stable tracking servo can be applied at the boundary between the recorded area and the unrecorded area. It becomes possible.

  Note that the control of the offset amount (ofs) is not necessarily limited to the case where the control is always performed so that ofs becomes 0, and the offset amount (ofs) is controlled to have an offset amount within a predetermined range as necessary. You can also.

  INDUSTRIAL APPLICABILITY The present invention can be used as an optical disk device that records and reproduces information on an optical disk with an optical pickup, and can realize an optical disk device with improved recording and reproduction quality.

The figure which shows the constitution of the optical disk device The figure which shows the means which produces | generates a tracking error signal and a focus error signal The figure which shows an example of the waveform of TE signal when a track jump is performed in the boundary part of the recorded area | region and an unrecorded area | region The figure which shows the process which correct | amends the focus offset and correct | amends the distortion of the waveform of TE signal The figure which shows the operation which irradiates the laser beam to the pit formed on the track center of the optical disk and receives the reflected light by the pit with the detector Diagram showing generation of TE signal The figure which shows the operation | movement which receives a laser beam on the pit formed on the track center which is a boundary part of the recorded area | region of an optical disk, and an unrecorded area | region, and receives the reflected light by a pit with a detector The figure which shows the condensing state of the laser beam at the boundary between the recorded area and the unrecorded area of the optical disc The figure which shows the waveform of TE signal

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Optical pick-up 3 Detector 4 Signal calculating part 5 Focus actuator 6 Tracking actuator 7 DSP
8 CPU
11 Peak detection circuit 12 Bottom detection circuit 13 Low pass filter circuit 21 Track center 22 Pit 23 Spot 24 Detector 25 Detector 31 Objective lens 32 Laser beam

Claims (4)

When the optical pickup is moved to the boundary between the recorded area and unrecorded area of the optical disc and the still operation is performed, the peak level, the bottom level, and the DC level of the tracking error signal are measured, and tracking is performed in the track jump state. A tracking control method comprising: performing focus control so that an error signal level is an intermediate level between a peak level and a bottom level to adjust an offset amount of the tracking error signal. The tracking control method according to claim 1, wherein the focus control is performed by adding or subtracting a focus offset correction value according to whether the offset amount of the tracking error signal is positive or negative. A peak detection circuit that measures the peak level of the tracking error signal and the bottom level of the tracking error signal when the optical pickup is moved to the boundary between the recorded area and the unrecorded area of the optical disc and the still operation is performed. And a low-pass filter circuit for measuring the DC level of the tracking error signal so that the level of the tracking error signal in the track jump state is an intermediate level between the peak level and the bottom level. An optical disc apparatus comprising a signal calculation unit that performs focus control and adjusts an offset amount of a tracking error signal. The signal calculation unit includes an offset amount calculation unit that calculates an offset amount of the tracking error signal, and adds a focus offset correction value according to the sign of the tracking error signal offset amount obtained by the offset amount calculation unit or 4. The optical disk apparatus according to claim 3, further comprising a focus offset correction unit that decreases.

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