JPH076524A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent the deterioration in the characteristics of tracking servo by asynchronous disturbance in rotation of a medium used with the optical recording and reproducing device. CONSTITUTION:Two sets of optical heads and tracking servo circuits are packaged and the outputs of lead lag filters 15 within the servo circuits of the parties opposite to each other are taken into their own circuits. While the servo error signals of their own circuits are monitored by a CPU 21 via an A/D converter 20, the mixing rate of the lead lag filter outputs is so determined as to minimize the servo errors, by which the servo errors are compressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for a magneto-optical disk or the like, and more particularly to a tracking servo system for positioning an optical head.

[0002]

2. Description of the Related Art In a conventional device of this type, a revolving memory servo as shown in FIG. 5 is used as a tracking servo system for compressing a residual servo error component due to eccentricity of a recording medium such as a magneto-optical disk used. Used the method. The operation will be briefly described below. Two-phase tracking detection signal T output from an optical head (not shown)
For a and Tb, the difference signal amplifier 51 and the sum signal amplifier 52 generate a difference signal and a sum signal of the both signals, and the difference signal is gain-corrected by the AGC amplifier 53 according to the change of the sum signal, and an error occurs. It is input to the amplifier 54. Error amplifier 54
Is subjected to phase compensation by a lead / lag filter 55, passed through a switch 56, a mix amplifier 57, and converted into an actuator drive current by a voltage / current conversion amplifier 58 (drive amplifier). The error amplifier 54 performs servo operation so that the input difference signal becomes GND (residual servo error is zero). The switch 56 is for turning on and off the tracking servo operation, and the track jump pulse generator 59 generates a pulse for controlling the track jump. These are controlled by the CPU unit 61.

In addition, a circulating memory unit 63 is mounted in order to compress an error signal synchronized with the rotation of the recording medium, such as an eccentric component of the recording medium. In the loop memory unit 63, the residual error signal for one rotation of the recording medium for one rotation is accumulated in the internal memory for a fixed sampling time and is output to the mix amplifier 57 at the same timing in the next cycle. With this method, the steady residual error synchronized with the rotation can be compressed to about 1/10, and the servo following performance can be improved.

[0004]

In the circuit configuration using the circulation memory unit 63 described above, the frequency component synchronized with the rotation can be compressed, but the frequency component asynchronous with the rotation generated by the motor for rotating the recording medium or the like. For such frequencies, the residual error components of the sampling point and the output point of the next cycle are not equal, and rather there is the problem that the main servo characteristics deteriorate as disturbance.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical recording / reproducing apparatus capable of realizing a tracking servo system which is effective not only for disturbance not synchronized with rotation but also for disturbance not synchronized with rotation.

[0006]

SUMMARY OF THE INVENTION The present invention is an optical recording / reproducing apparatus for irradiating a rotating optical recording / reproducing medium with a light beam to record / reproduce an information signal. The optical head includes a tracking actuator that follows the formed track and a tracking signal detector, and two sets of tracking servo circuits that drive and control the tracking actuator, respectively, and the two optical heads perform optical recording. They are arranged 180 ° opposite to the center of rotation of the reproduction medium,
In the track following operation, the residual servo error signal component of each tracking servo circuit is output to each other, and the residual servo error signal component of the other side is superimposed on its own tracking servo circuit.

Further, according to the present invention, each of the tracking servo circuits generates a difference signal and a sum signal of the two-phase tracking detection signals from the corresponding optical heads, and a sum signal amplifier, and the sum signal. An AGC amplifier that corrects the gain of the difference signal according to the change of
The lead lag includes an error amplifier that receives the output signal of the amplifier and operates to reduce the residual servo error to zero, and a lead lag filter that receives the output of the error amplifier and performs phase compensation thereof. The output of the filter is output to the tracking servo circuit of the other party, and further, a mix amplifier for superimposing the output of the lead-lag filter and the output of the lead-lag filter in the tracking servo circuit of the other party is included. An optical recording / reproducing device is obtained.

According to the present invention, each of the tracking servo circuits further includes a variable gain amplifier for receiving the output of the lead / lag filter in the tracking servo circuit of the other side and extracting the AC component thereof, and the error amplifier. An optical recording / reproducing apparatus including a CPU that determines the gain of the variable gain amplifier according to the output of the optical recording / reproducing apparatus.

[0009]

In the optical recording / reproducing apparatus of the present invention, another optical head is provided at a position opposed to one optical head by 180 °. This operates in parallel with the first optical head in order to improve the data transfer rate of the device. The output of the lead-lag filter of the tracking servo circuit is input to the mix amplifier of the other tracking servo circuit, and the mixing ratio of this mix amplifier is determined by observing the servo error by the CPU.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. 1 shows a tracking servo circuit according to an embodiment of the present invention, and FIG. 2 shows a recording / reproducing system using the tracking servo circuit shown in FIG.

First, FIG. 2 will be described. This recording / reproducing system includes a magneto-optical disk 1, an optical head 2, a laser diode drive circuit 3, a magnetic field generating circuit 4 for applying a magnetic field to the magneto-optical disk 1, and an RF reproduced by the optical head 2.
An RF amplifier 5 for amplifying a reproduction signal, a focus servo circuit 6 for focus control, and a tracking servo circuit 7 are included.

When information is recorded, the recording signal is sent to the laser diode drive circuit 3, the laser light is subjected to a predetermined modulation, and the signal is recorded on the recording surface of the magneto-optical disk 1. Further, the optical head 2 is internally provided with a laser diode 2
-1, collimator lens 2-2, beam shaping prism 2
-3, the polarization beam splitters 2-4 and 2-5, and the objective lens 2-6, and the laser light emitted from the laser diode 2-1 passes through the above-mentioned path and is applied to the magneto-optical disk 1. The light from the polarization beam splitter 2-5 is 1 /
Photoelectric conversion is performed by the reproduction signal detector 2-9 via the four-wave plate 2-7 and the lens 2-8. On the other hand, the light from the polarization beam splitter 2-4 is sent to the track error detector 2-12 via the lens 2-10 and the beam splitter 2-11, where the tracking detection signals Ta and Tb are obtained. The other light from the beam splitter 2-11 passes through the knife edge 2-13 and the focus error detector 2-.
14 where the focus error signals Fa and F are sent.
b is obtained. The outputs of the tracking servo circuit 7 and the focus servo circuit 6 are drive amplifiers 7a and 7a, respectively.
6a to the lens actuator 2-15,
The position of the objective lens 2-6 is controlled. The output of the tracking servo circuit 7 is also supplied to the positioner motor 8 via the drive amplifier 7b.

In FIG. 1, two-phase tracking detection signals Ta and Tb output from the optical head 2 are difference-amplified by a difference signal amplifier 11, gain-corrected by an AGC amplifier 13, and input to an error amplifier 14. To do. In addition, A
In the GC amplifier 13, the sum signal of the tracking detection signals Ta and Tb is input from the sum signal amplifier 12, and the gain is automatically adjusted according to the change amount. Also, error amplifier 1
In 4, the servo operation is performed so that the input difference signal becomes GND (residual servo error is zero).

The output of the error amplifier 14 is phase-compensated by the lead / lag filter 15, passes through the switch 16 and the mix amplifier 17, and is converted into a lens actuator drive current by the drive amplifier 7a (voltage / current conversion amplifier). 2-15 are driven.

The CPU unit 21 controls the start and end of the servo operation and the control of the track jump via the track jump pulse generator 19. The above operation is the same as the conventional device.

The apparatus of the present invention includes two sets of optical heads and tracking servo circuits, but only one set is shown in FIG. The tracking servo circuit outputs the output of its own lead / lag filter 15 to the tracking servo circuit of the other party, and also inputs the output of the lead / lag filter of the other party tracking servo circuit to the variable gain amplifier 22. The variable gain amplifier 22 extracts only the AC component of the input signal, and the gain is C
It is set by the PU unit 21. In the CPU unit 21, the output of the error amplifier 14 is converted into a digital value by the A / D converter 20, and the residual error is monitored, and the gain of the variable gain amplifier 22 is adjusted so that the integrated value for one rotation of the recording medium becomes minimum. Has been decided. Further, while the track jump is being executed, the output to the other party is output at the GND level.

FIG. 3 shows a servo error signal in the state of being subjected to a disturbance asynchronous with the rotation. In this device, as shown in FIG. 4, two optical heads are arranged to face each other by 180 ° about the rotation axis of the recording medium, and as a result, two servo heads obtained from the two optical heads are arranged. The disturbance component of the error signal has a phase difference of 180 °. In this device, attention is paid to this point, and the above-described configuration is used to cancel the disturbance component, so that the compression rate of the servo error can be improved even with respect to the disturbance asynchronous with the rotation.

[0018]

As described above, according to the present invention, the servo error signals of the two optical heads are input from the other side and superposed on their own actuator drive signals, so that a disturbance synchronized with the rotation of the recording medium is generated. Not only this, it is possible to prevent an increase in residual errors due to asynchronous disturbance, and obtain stable tracking servo characteristics.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a recording / reproducing system to which the present invention is applied.

FIG. 3 is a diagram showing a waveform of a servo error signal when being affected by an asynchronous disturbance.

FIG. 4 is a diagram showing an arrangement of two optical heads according to the present invention.

FIG. 5 is a block diagram of a conventional tracking servo circuit.

[Explanation of symbols]

 11 difference signal amplifier 12 sum signal amplifier 13 AGC amplifier 14 error amplifier 15 lead / lag filter 16 switch 17 mix amplifier 19 track jump pulse generator 20 A / D converter 21 CPU unit 22 gain variable amplifier

Claims (3)

[Claims] 1. In an optical recording / reproducing apparatus for irradiating a rotating optical recording / reproducing medium with a light beam to record / reproduce an information signal, the light beam follows a track formed on the surface of the optical recording / reproducing medium. The optical head includes an actuator and a tracking signal detector, and two sets of tracking servo circuits for driving and controlling the tracking actuator. Each of the two optical heads is 180 degrees with respect to the center of rotation of the optical recording / reproducing medium.
° It is arranged so as to face each other, and outputs the residual servo error signal component of each tracking servo circuit to each other in the track following operation, and superimposes the residual servo error signal component of the other side on its own tracking servo circuit. Optical recording and reproducing device. 2. The optical recording / reproducing apparatus according to claim 1, wherein each of the tracking servo circuits generates a difference signal amplifier and a sum signal of a two-phase tracking detection signal from a corresponding optical head and a sum signal amplifier. A signal amplifier, an AGC amplifier that corrects the gain of the difference signal according to the change of the sum signal, an error amplifier that operates to reduce the residual servo error to zero by receiving the output signal of the AGC amplifier, and the error A lead-lag filter for receiving the output of the amplifier and compensating its phase, and outputting the output of the lead-lag filter to the tracking servo circuit on the other side; and further, the output of the lead-lag filter and the other side. Optical recording characterized by including a mix amplifier for superimposing the output of the lead-lag filter in the side tracking servo circuit Playback device. 3. The optical recording / reproducing apparatus according to claim 2, wherein each of the tracking servo circuits further receives the output of the lead / lag filter in the tracking servo circuit of the other side and extracts a gain of the AC component. An optical recording / reproducing apparatus comprising: a variable amplifier and a CPU that determines the gain of the gain variable amplifier according to the output of the error amplifier.