JP2004047000A - Servo gain adjusting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately set the servo gain of focusing and tracking of a recordable optical disk such as CDR, CDRW. <P>SOLUTION: A servo circuit 24 sets the servo gain based on a FE (focus error) signal obtained at a front end 20 and a TE (tracking error) signal. In that case, a pit detecting circuit 30 detects existence of parts by a signal from the front end 20, when pits do not exist, the servo gain is set to a higher value than the optimum value in which the servo gain is obtained. Thereby, the appropriate servo gain can be set when a part in which pits exist is read. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to focus or tracking servo gain adjustment in a recording / reproducing apparatus for a recordable optical disc such as a CDR or a CDRW.
[0002]
[Prior art]
2. Description of the Related Art Recordable optical disks such as CDRs and CDRWs have been known, and are widely used for recording music information and various data.
[0003]
The CDR and CDRW perform recording and reproduction by irradiating a recording surface of an optical disc with laser light. Recording is performed by irradiating the dye on the optical disk with light to form optical pits, and reproduction is performed by reading these pits. Therefore, at the time of recording / reproducing, it is necessary to focus the laser on the recording surface and perform tracking so as to surely irradiate light to the pit position. In a normal CD, only reproduction is required, but focus and tracking are the same.
[0004]
For this purpose, the optical recording / reproducing apparatus has a servo system for controlling a focus and tracking by moving a lens system in an optical pickup in accordance with a detection signal of a photodetector for detecting reflected light from an optical disk. . In particular, the optical disk is not necessarily flat, and the focus and tracking servo systems must perform control following the rotation of the optical disk. If the gain of the servo system (servo gain) is too small, recording and reproduction become unstable. . In addition, if the servo gain is too large, there is a problem that the servo system becomes unstable due to following scratches and the like.
[0005]
Therefore, in the optical disk recording / reproducing apparatus, when the optical disk is set, the optical pickup adjusts the focus and tracking signal levels at the position where the IN switch at the outer peripheral position of the optical disk is separated, and adjusts each servo gain. Is determined.
[0006]
[Problems to be solved by the invention]
This servo gain adjustment was originally performed for a read-only CD, and is similarly performed for a recordable optical disc such as a CDR or CDRW.
[0007]
In a read-only CD, pits are formed in aluminum, and a light detection signal (PD signal) for focusing and tracking is constant in any portion, and there is no problem in adjusting the servo gain in any portion. .
[0008]
However, in the case of CDR or CDRW, there is a difference in a PD signal between a recorded portion and an unrecorded portion. This is because no pits are formed in the unrecorded portion, so that the PD signal becomes larger than in a recorded portion in which pits have already been formed in recording.
[0009]
That is, in the recorded portion, the PD signal is smaller than the unrecorded portion by about 3 dB to 5 dB. The initial state of the recordable disc is an unrecorded state, and is a normal recorded state at the time of additional recording or rewriting. Therefore, there are a recording state and an unrecorded state at the focus and tracking adjustment positions.
[0010]
Conventionally, no attention has been paid to this point, and when performing adjustment in an unrecorded portion and performing track jump or tracing in a recorded portion, the servo gain becomes insufficient and becomes unstable. was there.
[0011]
It is conceivable that the servo gain is always set to a large value. However, in this case, there is a problem in that the servo gain reacts to the flaw as described above and becomes unstable.
[0012]
The present invention has been made in view of the above problems, and has as its object to provide a servo gain adjusting device capable of appropriately setting a focus or tracking servo gain for a recordable optical disc such as a CDR or a CDRW. I do.
[0013]
[Means for Solving the Problems]
The present invention relates to a servo gain adjusting device that adjusts a servo gain in focusing or tracking on a recordable optical disc, and includes a photodetector that detects reflected light from a recording surface of the recordable disc, and a light detector that detects the reflected light from the photodetector. It is characterized by comprising pit detection means for detecting the presence or absence of a pit from a detection signal, and servo gain setting means for setting a servo gain according to the detection result of the pit detection means.
[0014]
As described above, when the servo gain is adjusted by the pit detection means, the servo gain is changed so as to increase by a predetermined amount. Therefore, when focusing or tracking is actually performed in a portion having a pit, focusing and tracking can be performed with an appropriate servo gain.
[0015]
Further, the servo gain setting means sets the optimum servo gain determined according to the intensity of the reflected light from the photodetector when there is a pit in the detection result of the pit detection means, and when there is no pit, It is preferable that the servo gain be larger than the servo gain determined according to the intensity of the reflected light from the photodetector. As a result, it is possible to guarantee an error when the operation is performed in a portion having no pit.
[0016]
Preferably, the servo gain is adjusted by adjusting the amplitude level of an error signal of a servo system.
[0017]
By increasing the amplitude of the error signal, the dynamic range of the error signal can be increased.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a block diagram showing a configuration of an optical disk recording / reproducing device including a servo gain adjusting device according to one embodiment of the present invention.
[0020]
A recordable optical disk 10 such as a CDR or CDRW is rotated by a spindle motor 12 on a turntable. The rotation of the spindle motor 12 is detected by the FG detector 14, and the detected rotation signal is supplied to the motor servo 16. Then, the motor servo 16 adjusts the optical disk 10 to a predetermined rotation speed. Actually, the rotation speed is controlled with reference to ATIP (absolute time in pre-groove) reproduced from the optical disk 10 or time data in subcodes in the recorded data.
[0021]
An optical pickup 18 is provided in the vicinity of the optical disk 10 to read out a signal written on the optical disk 10. That is, the optical pickup 18 has a built-in laser light source, irradiates the optical disk 10 with light from the laser light source, and detects reflected light with a photodetector. Here, this photodetector is composed of a plurality of photoelectric conversion elements so that a focus error signal and a tracking error signal can be detected, and a PD signal, which is a read signal including these, is output from the optical pickup 18.
[0022]
Note that the optical pickup outputs a writing laser in accordance with the supplied writing signal, so that a signal can be recorded on the optical disc 10.
[0023]
The PD signal from the optical pickup 18 is supplied to a front end circuit 20 for processing a read analog signal, subjected to processing such as amplification and waveform shaping, and supplied to a data processing circuit 22. The data processing circuit performs various data processing such as demodulation processing and error correction processing, and generates and outputs a reproduced signal. In the case of writing, data supplied from the outside is subjected to a modulation process or the like to form a pulse signal for writing, which is supplied to the optical pickup 18.
[0024]
Further, a focus error signal (FE signal) and a tracking error signal (TE signal) obtained from the PD signal are obtained from the front end 20, and are supplied to the servo circuit 24. The servo circuit 24 performs focus and tracking by controlling the focus actuator 26 and the tracking actuator 28 based on the FE signal and the TE signal.
[0025]
Here, in the present embodiment, the PD signal is supplied from the front end 20 to the pit detection circuit 30, where it is detected whether or not there is a pit. That is, if a pit exists, a change in the signal intensity according to the presence of the pit should be detected. If no pit exists, the signal intensity is almost constant. Therefore, the presence or absence of a pit is detected from the intensity change state of the PD signal.
[0026]
Then, the pit detection result in the pit detection circuit 30 is supplied to the servo circuit 24. The servo circuit 24 adjusts the level of the focus error signal and adjusts the servo gains of the focus servo system and the tracking servo system at the time of starting the reproduction of the optical disk 10. At this time, the detection result of the pit detection circuit 30 is used. I do. That is, when a pit is detected, the servo gain is kept at the normal adjustment value, but when no pit is detected, the servo gain is set to be larger by 3 dB to 5 dB.
[0027]
Here, the adjustment operation in the servo circuit 24 will be described. First, adjustment of the focus servo system will be described with reference to FIG.
[0028]
First, the optical pickup 18 is set to an initial position on the outer peripheral side of the optical disk by a moving mechanism in the radial direction (S11). This initial position is a position where the IN switch for turning on the reading operation by moving the optical pickup 18 in the outer peripheral direction is apart. Here, the focus of the optical pickup 18 is adjusted from the PD signal obtained by the optical pickup 18 so that the FE signal becomes a predetermined level (S12). At this time, the focus and tracking servos are turned off, and the FE signal level is adjusted so that the amplitude value of the S curve of the FE signal becomes 1.2 Vp-p. The FE signal is based on, for example, an astigmatism method, and shows an S curve by adjusting focus. Therefore, focus adjustment is performed at a point where the FE signal becomes 0, and the amplification level of the FE signal is adjusted so that the amplitude of the S curve of the FE signal becomes 1.2 V.
[0029]
Next, a tracing operation is performed with the focus servo system and the tracking servo system turned on (S13), and a predetermined disturbance is applied in that state to adjust the gain of the focus servo system so as to obtain an appropriate servo gain (S14). ). That is, the gain is set to a value that can sufficiently follow the change in focus due to the distortion of the optical disk and is less likely to be affected by scratches or the like.
[0030]
Then, the pit detection circuit 30 makes a pit determination (S15). This is performed by determining whether or not there is a pit from the intensity change state of the reflected light of the optical disk 10 as described above.
[0031]
Then, if the determination in S15 is YES, the above-described gain adjustment is left as it is, and the process is terminated. On the other hand, if the determination in S15 is NO, the FE signal level adjusted in S12 is increased by about 3 to 5 dB (S16).
[0032]
Thus, by increasing the FE signal level, the amplitude of the S curve of the FE signal increases. As a result, the voltage value of the FE signal for the focus shift increases, and the servo gain increases. Since the FE signal level at the location where the pit exists is about 3 to 5 dB lower than the FE signal at the location where the pit does not exist, the adjustment result performed at the location where the pit does not exist is different from the adjustment performed at the location where the pit exists. Can be modified to an equivalent.
[0033]
In order to adjust the servo gain, the gain of the servo system itself may be adjusted. However, as in the present embodiment, it is more preferable to adjust the FE signal level because the dynamic range of the servo system can be widened.
[0034]
Next, adjustment of the tracking servo system will be described with reference to FIG. The basic procedure is the same as for focus.
[0035]
First, the optical pickup 18 is set at the initial position (S21), and the tracking of the optical pickup 18 is adjusted so that the TE signal is at a predetermined level (S22). At this time, the focus and tracking servos are turned off, and the TE signal level is adjusted such that the amplitude value of the S curve of the TE signal becomes 1.2 Vp-p.
The TE signal is, for example, a signal indicating a difference between reflected light intensities of sub-spots on both sides of the main spot, and shows an S-curve by adjusting tracking. Therefore, tracking adjustment is performed at a point where the TE signal becomes 0. The amplification level of the TE signal is adjusted such that the amplitude of the S curve of the TE signal becomes 1.2 V.
[0036]
Next, a tracing operation is performed with the focus servo system and the tracking servo system turned on (S23), and a predetermined disturbance is applied in this state to adjust the gain of the tracking servo system so as to obtain an appropriate servo gain (S24). ). That is, the gain is set to a value that can sufficiently follow the fluctuation of the tracking due to the distortion of the optical disk and is less likely to be affected by scratches or the like.
[0037]
Then, the pit detection circuit 30 makes a pit determination (S25). Then, if the determination in S25 is YES, the above-described gain adjustment is left as it is, and the process is terminated. On the other hand, if the determination in S15 is NO, the TE signal level adjusted in S22 is increased by about 3 to 5 dB (S26). Also in this case, the servo gain itself may be increased.
[0038]
As described above, according to the present embodiment, when the focus or tracking is adjusted in a portion having no pit, the FE signal level and the TE signal level are changed to 3 to 5 dB higher. Therefore, when focusing or tracking is actually performed in a portion having a pit, focusing or tracking can be performed with an appropriate servo gain.
[0039]
【The invention's effect】
As described above, according to the present invention, when the servo gain is adjusted by the pit detection means, the servo gain is changed so as to increase by a predetermined amount. Therefore, when focusing or tracking is actually performed in a portion having a pit, focusing and tracking can be performed with an appropriate servo gain.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a disk recording / reproducing device including an optimum recording power control device according to an embodiment.
FIG. 2 is a flowchart illustrating a procedure of a focus adjustment process.
FIG. 3 is a flowchart illustrating a processing procedure of tracking adjustment.
[Explanation of symbols]
10 optical disk, 18 optical pickup, 20 front end, 22 data processing circuit, 24 servo circuit, 26 focus actuator, 28 tracking actuator, 30 pit detection circuit.

Claims (3)

A servo gain adjustment device that adjusts a servo gain in focusing or tracking on a recordable optical disc,
A photodetector for detecting light reflected from the recording surface of the recordable disc,
Pit detection means for detecting the presence or absence of a pit from a detection signal from the photodetector; servo gain setting means for setting a servo gain according to a detection result of the pit detection means;
A servo gain adjusting device having: The apparatus according to claim 1,
The servo gain setting means sets the optimum servo gain determined according to the intensity of the reflected light from the photodetector when there is a pit in the detection result of the pit detection means, and sets the optical gain when there is no pit in the detection result. A servo gain adjusting device that sets a servo gain larger than a servo gain determined according to the intensity of light reflected from a detector. The apparatus according to claim 1 or 2,
A servo gain adjusting device for adjusting the servo gain by adjusting the amplitude level of an error signal of a servo system.

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