JP2705233B2 - Tracking control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device of an optical reproducing apparatus for optically reading a signal recorded on a recording medium.

2. Description of the Related Art In recent years, an optical device that optically reads an information signal by performing focus control and tracking control on a recording medium, such as a compact disk, has been increasingly used.

FIG. 2 is a block diagram of a tracking control device conventionally used, wherein 1 is a disk as a recording medium, 2 is a motor for rotating the disk, 3 is an optical head for reading signals from the disk, 4 is a traverse motor for moving the optical head in the radial direction of the disk, 5 is a belt for transmitting the torque of the traverse motor, 6 is a worm for feeding the optical head, 7 is focus control means, and 8 is focus search means. , 9 is an out-of-focus detecting means, 10 is a logic device, 12 is a tracking error detection circuit for synthesizing and generating a tracking error signal, 13 is a switch for turning on / off the tracking error signal, and 14 is a low level for increasing the low-frequency gain. The frequency compensating circuit is composed of an operational amplifier 15, resistors 16, 17, 18 and a capacitor 19. Reference numeral 21 denotes a resistor, and reference numeral 22 denotes a variable resistor, which forms an offset adjustment circuit. Reference numeral 23 denotes a phase compensation circuit, which includes an operational amplifier 24, resistors 25, 26, and 28 and a capacitor 27. Reference numeral 29 denotes a tracking driving device that drives the optical head 3 in the tracking direction. Reference numeral 30 denotes a traverse driving device that drives a traverse motor to move the optical head.

The operation of the tracking control device configured as described above will be described below.

First, the disk 1 is rotated by the motor 2 and the focus position is searched for by the focus search means 8, and then focus control is performed by the focus control means 7.

Then the switch 13 is turned on by the logical device 10,
The signal read by the optical head 3 and the tracking error signal synthesized by the tracking error detection circuit 12 are passed through the switch 13 from the low-frequency compensation circuit 14 to the phase compensation circuit.
23, the optical head 3 is controlled through the tracking drive circuit 29. Here, the low-frequency compensation circuit 14 has a frequency characteristic as shown by the solid line in FIG. 3 and raises the low-frequency gain required to follow the eccentricity of the disk. It has such a frequency characteristic and prevents the oscillation of the control system by leading the phase to the phase.The optical head 3, the tracking error detection circuit 12, the low-frequency compensation circuit 14, the phase compensation circuit 23,
The tracking drive circuit 29 forms tracking control means.

When the focus is deviated due to vibration or a scratch on the disk 1, a defocus signal is supplied to the logic circuit 10 from the defocus detection means. Then, the focus search means operates in response to a command from the logic device 10 to start the focus pull-in operation again. While the focus is out of focus, the switch 13 is also turned off to turn off the tracking.

When following the track of the disc, the range that the optical head alone can follow is narrow, so that the entire optical head 3 is moved by the traverse motor 4 through the traverse drive 30 by the output of the tracking drive 29.

Further, an offset adjusting circuit is configured by the semi-fixed resistor 22 and the resistor 21, and the adjustment is performed so as to eliminate the influence of a delay due to a load of the traverse motor or the like and an electrical offset of the tracking driving device 29. The purpose of the offset adjustment is when the disc 1 is damaged, for example, if the load on the traverse motor is heavy and the delay is large, and if there is no offset adjustment,
Since the tracking error signal is lost at the flaw, the optical head 3 is displaced, and when the flaw is completed, the tracking is deviated, and a correct signal is not output for a while. However, when the tracking error signal is lost, if the offset adjustment is performed so that the optical head 3 just passes the track position where the main body should be, the tracking position does not shift even if the tracking error signal is lost due to scratches. As soon as the wound is over, the correct signal is restored.

Problems to be Solved by the Invention However, conventionally, offset adjustment has been indispensable in order to improve playability (performance on a scratched disc) as described above. In addition, even if the offset is correctly adjusted, if the load on the traverse motor is uneven, the position of the traverse motor deviates from the optimum offset position, and the playability deteriorates.

An object of the present invention is to solve the above-mentioned problems, and to provide a tracking control device that does not require offset adjustment and that does not deteriorate playability even when the load on the traverse motor is uneven.

Means for Solving the Problems In order to solve the above problems, the tracking control device of the present invention enables switching of the low-frequency gain of a low-frequency compensation circuit, and increases the DC gain when tracking control is normal. It is.

Effect of the Invention With the above configuration, the DC gain is extremely high when the tracking control is ON, so that even if the load on the traverse motor is large and the delay is large, the offset adjustment can be performed when the tracking drive device has an electrical offset. Without this, the average value of the tracking error signal before entering the flaw is 0 and it is 0 even after entering, so that tracking does not shift between the flaws, so that playability can be performed without offset adjustment. Is good.

Further, even if the load of the traverse motor is uneven and the amount of delay changes, tracking does not shift between scratches, so that playability is good.

FIG. 1 is a block diagram showing an embodiment of a tracking control device according to the present invention. In FIG. 1, 1 is a disk as a recording medium, 2 is a motor for rotating the disk, 3 is an optical head for reading a signal from the disk, and 4 is an optical head for moving the optical head in the radial direction of the disk. A traverse motor, 5 is a belt for transmitting the torque of the traverse motor, 6 is a worm for sending the optical head, 7 is focus control means, 8 is focus search means, 9 is defocus detection means, 10 is a logic device, and 11 is a logic device. Tracking deviation detection means, 12 is a tracking error detection circuit that generates a tracking error signal by synthesis, 13 is a switch that turns on / off the tracking error signal, 14 is a low-frequency compensation circuit that increases low-frequency gain, and operational amplifiers 15, It consists of resistors 16, 17, 18, a capacitor 19 and a switch 20. Reference numeral 23 denotes a phase compensation circuit, which includes an operational amplifier 24, resistors 25, 26, and 28 and a capacitor 27. Reference numeral 29 denotes a tracking driving device that drives the optical head 3 in the tracking direction. Reference numeral 30 denotes a traverse driving device that drives a traverse motor to move the optical head.

The operation of the tracking control device configured as described above will be described below.

First, the disk 1 is rotated by the motor 2 and the focus position is searched for by the focus search means 8, and then focus control is performed by the focus control means 7. At this time, since the switch 13 is OFF and the switch 20 is ON, the tracking control is OFF.

Then the switch 13 is turned on by the logical device 10,
The signal read by the optical head 3 and the tracking error signal synthesized by the tracking error detection circuit 12 are passed through the switch 13 from the low-frequency compensation circuit 14 to the phase compensation circuit.
23, the optical head 3 is controlled through the tracking drive circuit 29. Here, the low-frequency compensation circuit 14 has a frequency characteristic as shown by the solid line in FIG. 3 when the switch 20 is ON, and has a frequency characteristic as shown by a broken line when the switch 20 is OFF, and follows the eccentricity of the disk. The phase compensating circuit 23 has a frequency characteristic as shown in FIG. 4 to advance the phase and prevent the oscillation of the control system by increasing the gain of the optical system.
3, the tracking error detecting circuit 12, the low frequency compensating circuit 14, the phase compensating circuit 23, and the tracking driving circuit 29 constitute a tracking control means.

The tracking error detecting means 11 operates as shown in FIG. 5. In FIG. 5, A is an output signal of the optical head 3, B is an output signal when A is depressed in the direction of the light level, and C is an output signal. Output when B does not output for a certain period of time. This C is the output of the tracking error detection 11.

When a signal indicating that tracking is not lost is output from the tracking error detecting means 11 after the switch 13 is turned on, the switch 20 is turned off by a command from the logic device 10.

When the focus is out of focus due to vibration or a scratch on the disk 1, an out-of-focus signal is supplied from the out-of-focus detecting means 9 to the logic device 10. Then, the focus search means operates in response to a command from the logic device 10 to start the focus pull-in operation again. While the focus is out of focus, the switch 13 is also turned off and the switch 20 is turned on to turn off the tracking. When only tracking is deviated without defocusing, a defocusing signal is output from the defocusing detection means 11 to a logic device.
Supplied to 10. Then, the switch 20 is turned ON to prevent runaway of tracking.

When following the track of the disc, the range that the optical head alone can follow is narrow, so that the entire optical head 3 is moved by the traverse motor 4 through the traverse drive 30 by the output of the tracking drive 29.

Here, when the switch 20 is turned off, the DC gain becomes the oven gain of the operational amplifier 7, and therefore becomes extremely high. Therefore, even if the load on the traverse motor is large and the tracking delay is large,
Even if there is an offset at 29, the average value of the output of the tracking detection circuit 12 before entering the flaw is almost 0 and is 0 even after entering, so that tracking does not shift between the flaws, and Good playability without adjustment.

When the tracking is OFF, the switch 20 is ON, so that the electric charge of the capacitor 19 is discharged. When the tracking is ON, the electric charge of the capacitor 19 is not skipped.

Effects of the Invention As described above, according to the present invention, with a simple configuration, the playability is good without offset adjustment, and even when the traverse delay changes due to uneven load on the transformer motor, the playability is improved. Your abilities don't get worse. Therefore, it can be manufactured at low cost, and no adjustment man-hour is required. Further, since there is no adjustment, the adjustment does not shift due to vibration or temperature change during transportation.

[Brief description of the drawings]

1 is a block diagram of a tracking control device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional tracking control device, FIG. 3 is a frequency characteristic diagram of a low-frequency compensation circuit, and FIG. FIG. 5 is a waveform diagram for explaining the operation of the tracking deviation detecting means. 1 ... Disc, 2 ... Motor, 3 ... Optical head, 4
... traverse motor, 5 ... belt, 6 ... warm, 7 ... focus control means, 8 ... focus search means, 9 ... focus defocus detection means, 10 ... logic device, 11 ... tracking defocus detection means , 12 ... Tracking error detection circuit, 14 ... Low frequency compensation circuit, 23 ...
Phase compensation circuit, 29: tracking drive device, 30: traverse drive device.

Claims (1)

(57) [Claims] An optical head for reading an information signal from a recording medium; focus control means for condensing light from the optical head on the recording medium; defocus detection means for detecting defocus; A tracking control means having a switchable low-frequency compensation circuit for causing the light of the optical head to follow the track of the recording medium, and lowering the DC gain of the low-frequency compensation circuit at the time of tracking OFF and out of focus, and the focus control is normal. A tracking control device comprising a logic device that outputs a signal to raise when tracking is ON.