JP3635815B2 - Tracking servo control circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tracking control circuit employed in an optical disk device such as a CD (Compact Disk) player.
[0002]
[Prior art]
In an optical disc player, in order to accurately read the pit information carved on the disc, the optical beam for the track of the disc is set so that the information reading light beam spot accurately traces on the track which is a pit row. Tracking servo control is indispensable for controlling the relative position of the spot in the radial direction of the disk.
[0003]
In this tracking servo control, based on the reflected light beam from the disk surface, a deviation of the light beam spot with respect to the track in the radial direction of the disk is detected as a tracking error signal, and a tracking actuator is used with a drive voltage corresponding to the magnitude of the tracking error signal , The position of the light beam spot is continuously corrected, and control is performed so that the light beam spot always traces the center of the track.
[0004]
By the way, when the disc player is in a reproducing operation or the like, if a reflected light from the disc surface cannot be obtained due to some sudden cause, for example, a defect such as a scratch on the disc surface, the level of the tracking error signal is increased. Since it fluctuates in a higher direction than normal, for example, a so-called off-track state is established by the tracking servo gain corresponding to the tracking error signal level.
Therefore, a defect detection circuit is provided in the tracking servo circuit of the disc player, and when a defect is detected, the servo gain is lowered to lower the followability to the defect, thereby preventing the transition to the off-track state. A tracking servo control circuit is used.
[0005]
FIG. 4 is a block diagram showing a configuration of a tracking servo control circuit of a conventional CD player adopting this defect tracking system.
As shown in FIG. 4, the tracking servo control circuit 10 includes an optical pickup 11 including a drive system such as a track actuator, an RF amplifier 12, a tracking error amplifier 13, a defect detection circuit 14, a system controller 15, a register 16, and gain adjustment. The circuit 17 and the tracking servo circuit 18 are configured.
[0006]
In such a configuration, the optical pickup 11 generates an electric signal S11 based on the reflected light beam level irradiated on the optical disc DK and reflected from the disc surface, and is input to the RF amplifier 12 and the tracking error amplifier 13.
The RF amplifier 12 generates an RF signal S12 as shown in FIG. 5 based on the input signal S11 and outputs the RF signal S12 to the defect detection circuit 14.
The tracking error amplifier 13 generates a tracking error signal S13 based on the input signal S11 and outputs the tracking error signal S13 to the gain adjustment circuit 17. The tracking error signal S13 is ideally “0” when the beam spot is located at the center of the track, and when it deviates from the center of the track, it has a polarity corresponding to the deviation direction and corresponds to the deviation amount. It shows a so-called S-characteristic with a large size.
[0007]
Here, when the disk DK has a defect DF, the reflected light from the disk DK cannot be obtained, and the RF signal S12 also has a predetermined waveform at a location corresponding to the defect as shown in FIG. 5B. Not obtained, this area is detected as a defect by the defect detection circuit 14 and is output to the system controller 15 as a detection signal S14.
[0008]
In the system controller 15, when the defect detection signal S <b> 14 is input, tracking gain adjustment data consisting of, for example, 4 bits is transferred to the internal register 16. The data to the internal register 16 is supplied to the gain adjustment circuit 17.
The gain adjustment circuit 17 attenuates the level of the tracking error signal S13 with an attenuation rate based on the supplied adjustment data, performs servo gain adjustment, and inputs the tracking drive signal S17 to the tracking servo circuit 18. The tracking servo circuit 18 performs tracking servo adjustment based on the adjusted tracking drive signal S17.
In this way, the servo gain is lowered in accordance with the presence or absence of a defect on the disk surface, the followability to the defect is lowered, and off-tracking is difficult.
[0009]
[Problems to be solved by the invention]
As described above, the system controller 15 in the tracking servo control circuit 10 receives the active defect detection signal S14 and only determines that there is a defect on the disk DK surface. Data is being transferred.
However, although the defect detection signal S14 is active only during a period corresponding to the defect on the disk DK surface, as shown in FIG. 5, the system controller 15 detects the presence or absence of the defect on the disk DK surface. Therefore, the defect detection signal S14 must be constantly monitored.
Since the system controller 15 actually controls the entire optical disc system and also controls other servo systems or displays, it is a heavy load to constantly monitor the defect detection signal S14.
[0010]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a tracking servo control circuit that can reduce the load of a system controller that controls the entire system.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a drive for correcting the position of irradiated light on a medium surface according to a tracking error signal level obtained according to the reflected light level of light irradiated on the medium surface. A tracking servo control circuit for obtaining an output, which detects a region where predetermined reflected light is not obtained and falls below a predetermined level as a defect, generates a defect detection signal, and until a reset signal is input A latch circuit that latches the defect detection signal and outputs an active latch signal; a gain adjustment circuit that attenuates the tracking error signal level with an attenuation rate based on gain adjustment data to obtain the drive output; and the gain the adjustment data is output to the gain adjustment circuit, the output state of the latch circuit monitors at predetermined monitoring period, a latch signal Accession In the case of I Bed is a reset signal and outputs to the latch circuit performs a plurality of output monitoring in the monitoring period, when the predetermined number of times the monitoring operation of the plurality of times, the latch signal is active, the tracking servo A system controller that outputs gain adjustment data for attenuating the gain to the gain adjustment circuit.
[0012]
The present invention also provides a tracking servo that obtains a drive output for correcting the position of irradiated light on the medium surface according to the tracking error signal level obtained according to the reflected light level of the light irradiated on the medium surface. A defect detection circuit that detects a region where a predetermined reflected light is not obtained and falls below a predetermined level as a defect and generates a defect detection signal; and the defect detection signal until a reset signal is input A latch circuit that outputs an active latch signal, a gain adjustment circuit that attenuates the tracking error signal level with an attenuation rate based on gain adjustment data, and obtains the drive output, and an output of the latch circuit is active a counter to count the number of times becomes, the gain adjustment data is output to the gain adjustment circuit, a predetermined monitoring period The count value of the counter is monitored, if the count value is a predetermined value, and outputs a reset signal to said latch circuit, monitors the count value of the plurality of times in the monitoring period, the monitoring operation of the plurality of times And a system controller that outputs gain adjustment data for attenuating the tracking servo gain to the gain adjustment circuit when the count value reaches a predetermined value .
[0013]
According to the present invention, gain adjustment data is supplied to the gain adjustment circuit by the system controller , and the tracking error signal level is attenuated with an attenuation rate based on the gain adjustment data supplied in the gain adjustment circuit. Further, the defect detection signal output is previous value held by the latch circuit, in controlling the entire Oite system to the system controller, when a margin, so as to monitor the signal output after the latch, the latch at predetermined intervals The output is monitored and the latch circuit is reset each time.
If the number of times the latch output becomes active reaches the predetermined number, the latch circuit is reset, and the gain adjustment data for attenuating the tracking servo gain is gained as the defect appears frequently. Output to the adjustment circuit, the servo gain is attenuated and adjusted, the followability to defects is reduced, and the occurrence of off-track is prevented.
[0014]
Further, according to the present invention, the counter value of the counter that counts the number of active latch outputs on the output side of the latch circuit is monitored every predetermined period, and when the count value reaches the predetermined value, the latch circuit is reset. At the same time, the gain adjustment data is output to the gain adjustment circuit, and the servo gain is attenuated to reduce the follow-up to the defect, thereby preventing the occurrence of off-track.
In this way, the load on the system controller that controls the system is reduced.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
First Embodiment FIG. 1 is a block diagram showing a first embodiment of a tracking servo control circuit of a CD player according to the present invention, and FIG. 2 is a diagram showing a main waveform of FIG. .
[0016]
As shown in FIG. 1, the tracking servo control circuit 20 includes an optical pickup 21 including a drive system such as a tracking actuator, an RF amplifier 22, a tracking error amplifier 23, a defect detection circuit 24, a latch circuit 25, a system controller 26, and a register. 27, a gain adjustment circuit 28, and a tracking servo circuit 29. DK indicates an optical disk.
[0017]
The optical pickup 21 is a focus actuator that drives the objective lens in the optical axis direction so as to focus the light beam applied to the optical disk DK on the disk surface, and the light beam spot focused on the disk surface in the radial direction of the disk 21. It incorporates a tracking actuator to be moved, a light detection circuit that receives a reflected light beam from the disk surface based on the light beam applied to the optical disk DK, converts it into an electric signal S21, and outputs it to the RF amplifier 22 and tracking error amplifier 23. The optical disk DK is provided so as to be movable in the radial direction.
[0018]
The RF amplifier 22 receives an output signal S21 of a photodetection circuit (not shown) of the optical pickup 21, generates an RF signal S22, and outputs it to the defect detection circuit 24.
[0019]
The tracking error amplifier 23 receives an output signal S21 of a photodetection circuit (not shown) of the optical pickup 21 and becomes “0” when the beam spot is located at the center of the track, and when the beam spot is deviated from the center of the track, the direction of the deviation. A tracking error signal S23 having so-called S-characteristics having a polarity corresponding to the above and a magnitude corresponding to the deviation amount is generated and output to the gain adjustment circuit 28.
[0020]
When the defect detection circuit 24 receives the RF signal S22 and there is a defect DF in the disk DK, as shown in FIG. 2A, the reflected light from the disk DK cannot be obtained, and the RF signal S22. As shown in FIG. 2B, when a predetermined waveform is not obtained at a location corresponding to a defect, this region is detected as a defect, and a high level active defect is detected as shown in FIG. A signal S24 is generated and output to the latch circuit 25.
[0021]
The latch circuit 25 is reset by a reset signal RST input at a predetermined cycle T via the register 27, sets its output to a low level, and inputs a high-level defect detection signal S24 in this reset state. Then, the output is set to a high level until the next reset RST is input. That is, the latch circuit 25 functions as a previous value hold circuit.
[0022]
The system controller 26 is constituted by a microprocessor and controls the entire system such as control of servo system circuits such as tracking servo and focus servo. During this control, the output state of the latch circuit 25 is monitored every predetermined monitoring period T. When the latch output signal S25 is at the high level, the reset signal RST is output to the register 27, and the output is monitored, for example, m times in this monitoring period T, and n (n <m ) Times (for example, 5 times) When the latch output signal S25 is at a high level, it is assumed that defects such as scratches frequently appear on the disk surface, and the gain adjustment data S26 for attenuating the tracking servo gain together with the reset signal RST. Output to the register 27.
The gain adjustment data S26 is given as 4-bit data so that, for example, 16-stage attenuation adjustment is possible. For example, in the above monitoring operation, the data is set to increase the attenuation rate in accordance with the increase in the number of detection times of the high level latch output signal S25.
It should be noted that this gain adjustment data setting may be configured to be performed every time the high level latch output signal S25 is detected, although the load on the system controller 26 is slightly increased.
[0023]
The register 27 supplies the reset signal from the system controller 26 to the latch circuit 25 and supplies the gain adjustment data S26 to the gain adjustment circuit 28 as the signal S27.
[0024]
The gain adjustment circuit 28 attenuates the level of the tracking error signal S23 with an attenuation rate based on the supplied adjustment data, performs servo gain adjustment, and outputs the tracking drive signal S28 to the tracking servo circuit 29.
[0025]
The tracking servo circuit 29 performs tracking servo adjustment by driving the tracking actuator in accordance with the level of the tracking drive signal S28.
[0026]
Next, the operation of the above configuration will be described.
Here, it is assumed that the latch circuit 25 is in an initial state, that is, a reset state.
[0027]
The optical pickup 21 generates an electric signal S21 based on the reflected light beam level irradiated on the optical disk DK and reflected from the disk surface, and is input to the R amplifier 22 and the tracking error amplifier 23.
The RF amplifier 22 generates an RF signal S22 as shown in FIG. 2B based on the input signal S21 and outputs the RF signal S22 to the defect detection circuit 14.
The tracking error amplifier 23 generates a tracking error signal S23 based on the input signal S21 and outputs the tracking error signal S23 to the gain adjustment circuit 28.
[0028]
Here, when the disk DK has a defect, the reflected light from the disk DK cannot be obtained, and the RF signal S22 also obtains a predetermined waveform at a location corresponding to the defect as shown in FIG. However, this area is detected as a defect by the defect detection circuit 24 and is output to the latch circuit 25 as a high-level defect detection signal S24.
[0029]
The latch circuit 25 is in a reset state by a reset signal RST input at a predetermined cycle T via the register 27, and its output is set to a low level, but a high-level defect detection signal S24 is input. Accordingly, the output is set to a high level until the next reset RST is input. The latch output signal S25 is output to the system controller 26.
[0030]
The system controller 26 controls the entire system in parallel. The output state of the latch circuit 25 is monitored every predetermined monitoring period T. When the latch output signal S25 is at a high level, the reset signal RST is output to the register 27, whereby the latch circuit 25 is reset.
For example, when the output is monitored m times in this monitoring period T and n (n <m) times in the m monitoring operations and the latch output signal S25 is at a high level, there is a defect such as a scratch on the disk surface. As appearing frequently, gain adjustment data S26 for attenuating the tracking servo gain is output to the register 27 together with the reset signal RST.
The data to the internal register 27 is supplied to the gain adjustment circuit 28.
[0031]
The gain adjustment circuit 28 attenuates the level of the tracking error signal S23 with an attenuation rate based on the supplied adjustment data, performs servo gain adjustment, and outputs the tracking drive signal S28 to the tracking servo circuit 29. The tracking servo circuit 29 performs tracking servo adjustment based on the adjusted tracking drive signal S28.
In this way, when a defect on the disk surface is frequently detected, the servo gain is lowered to reduce the followability to the defect, thereby making it difficult to off-track.
[0032]
As described above, the latch circuit 25 that holds the defect detection signal S24 from the defect detection circuit 24 until the reset signal RST is input is provided, and the entire system is controlled. During this control, every predetermined monitoring period T The output state of the latch circuit 25 is monitored, and when the latch output signal S25 is at a high level, the reset signal RST is output to the register 27, and the output is monitored m times, for example, in this monitoring period T. If the latch output signal S25 is at the high level n (n <m) times in the monitoring operation, it is assumed that defects such as scratches frequently appear on the disk surface, and gain adjustment data S26 for attenuating the tracking servo gain. Is provided to the register 27 together with the reset signal RST. In the control of the entire disk system, when there is a margin, the presence or absence of defects on the disk surface can be detected by monitoring the signal output S25 after latching, so that the load on the system controller 26 is greatly reduced. There is.
[0033]
Second Embodiment FIG. 3 is a block diagram showing a first embodiment of the tracking servo control circuit of the CD player according to the present invention.
[0034]
The difference between the second embodiment and the first embodiment is that a program counter 30 for counting the number of outputs of the active latch output signal S25 (high level) is provided on the output side of the latch circuit 25, and the system controller 26 Is that the gain adjustment data is output based on the count value S30.
The counter 30 has its count value programmable by the system controller 26 and is reset by a reset signal RSTC. The reset timing can take various forms such as the output timing of the gain adjustment data, or the output when the preset maximum count value is reached.
[0035]
According to the second embodiment, in addition to the effect of the first embodiment described above, the system controller 26 does not need to store the number of times that the latch output signal has become active high level. There is an advantage that the load on the system controller 26 can be further reduced.
[0036]
【The invention's effect】
As described above, according to the present invention, there is no need to constantly monitor the detection signal level output from the defect detection circuit, and there is an advantage that the load on the system controller can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of a tracking servo control circuit of a CD player according to the present invention.
FIG. 2 is a timing chart for explaining the operation of FIG. 1;
FIG. 3 is a block diagram showing a second embodiment of a tracking servo control circuit of a CD player according to the present invention.
FIG. 4 is a block diagram showing a configuration example of a tracking servo control circuit of a conventional CD player.
FIG. 5 is a timing chart for explaining the operation of FIG. 4;
[Explanation of symbols]
20, 20a ... Tracking servo control circuit, 21 ... Optical pickup, 22 ... RF amplifier, 23 ... Tracking error amplifier, 24 ... Defect detection circuit, 25 ... Latch circuit, 26 ... System controller, 27 ... Register, 28 ... Gain adjustment circuit , 29... Tracking servo circuit, 30... Counter, DK.

Claims (11)

A tracking servo control circuit that obtains a drive output for correcting the position of irradiation light on a medium surface according to a tracking error signal level obtained according to a reflected light level of light irradiated on the medium surface,
A defect detection circuit that detects a region where predetermined reflected light is not obtained and falls below a predetermined level as a defect and generates a defect detection signal;
A latch circuit that latches the defect detection signal and outputs an active latch signal until a reset signal is input;
A gain adjustment circuit that attenuates the tracking error signal level with an attenuation rate based on gain adjustment data to obtain the drive output;
The gain adjustment data is output to the gain adjustment circuit, the output state of the latch circuit monitors at predetermined monitoring period, when the latch signal is active, a reset signal and outputs to the latch circuit, the A system that performs output monitoring a plurality of times in a monitoring cycle and outputs gain adjustment data for attenuating the tracking servo gain to the gain adjustment circuit when the latch signal is active a predetermined number of times in the monitoring operation. A tracking servo control circuit having a controller. An RF signal generation circuit for generating an RF signal corresponding to the reflected light level;
The tracking servo control circuit according to claim 1, wherein the defect detection circuit generates a defect detection signal based on the RF signal. The system controller, the tracking servo control circuit according to claim 1, wherein the latch output to set the data for the gain adjustment according to the number becomes active. 4. The tracking servo control circuit according to claim 3 , wherein the system controller sets the gain adjustment data so as to increase an attenuation rate in accordance with an increase in the number of times the latch output becomes active . It has a register that holds the gain adjustment data and reset signal output from the system controller,
The tracking servo control circuit according to claim 1, wherein the gain adjustment data held in the register is supplied to a gain adjustment circuit, and a reset signal is supplied to a latch circuit. A tracking servo control circuit that obtains a drive output for correcting the position of irradiation light on a medium surface according to a tracking error signal level obtained according to a reflected light level of light irradiated on the medium surface,
A defect detection circuit that detects a region where predetermined reflected light is not obtained and falls below a predetermined level as a defect and generates a defect detection signal;
A latch circuit that latches the defect detection signal and outputs an active latch signal until a reset signal is input;
A gain adjustment circuit that attenuates the tracking error signal level with an attenuation rate based on gain adjustment data to obtain the drive output;
A counter that counts the number of times the output of the latch circuit becomes active;
The gain adjustment data is output to the gain adjustment circuit, and the count value of the counter is monitored every predetermined monitoring period. When the count value is a predetermined value, a reset signal is output to the latch circuit and the monitoring period System that monitors the count value a plurality of times and outputs gain adjustment data for attenuating the tracking servo gain to the gain adjustment circuit when the count value reaches a predetermined value in the plurality of monitoring operations. A tracking servo control circuit having a controller. The tracking servo control circuit according to claim 6, wherein a count value of the counter is programmable. An RF signal generation circuit for generating an RF signal corresponding to the reflected light level;
The tracking servo control circuit according to claim 6, wherein the defect detection circuit generates a defect detection signal based on the RF signal. The tracking servo control circuit according to claim 6, wherein the system controller sets the gain adjustment data according to a count value of the counter. The tracking servo control circuit according to claim 6, wherein when the count value of the counter reaches a set value, the system controller outputs a reset signal that resets the counter. It has a register that holds the gain adjustment data and reset signal output from the system controller,
The tracking servo control circuit according to claim 10, wherein gain adjustment data held in the register is supplied to a gain adjustment circuit, and a reset signal is supplied to a latch circuit and a counter.

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