JPH0652558A - Servo controller for optical disk device - Google Patents

Abstract

PURPOSE:To reduce the cost of a servo controller and improve the degree of freedom in the circuit design of the controller. CONSTITUTION:The output signals of a low-pass filters 5 and 6 are alternately outputted to an A/D converter 8 by switching the connection between contacts 7a and 7c and connection between contacts 7b and 7c to each other in a switch 7 at a high speed by means of a control section 13. Digital signals from the A/D converter 8 are classified into two kinds of signals corresponding to the output signals of photoreceptor elements 1 and 2 by switching the connection between contacts 9a and 9b and connection between 9a and 9c to each other in a switch 9 so that the switching operation can be synchronized to that at the switch 7 by means of the section 13 and the two kinds of signals are respectively inputted to storage circuits 10 and 11. A digital arithmetic circuit 12 simultaneously reads out the digital signals from the circuit 10 and 11 and generates an error signal by performing prescribed arithmetic operation on both signals. Therefore, the circuit configuration of the this servo controller can be simplified, since no other A/D converter than the converter 8 nor analog arithmetic circuit is required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control device for an optical disk device which performs servo control based on signals detected by a plurality of light receiving elements.

[0002]

2. Description of the Related Art Generally, in an optical disk device, servo control such as tracking servo and focus servo is performed by using reflected light from the optical disk. Specific examples will be described below.

For example, in the servo controller as shown in FIG. 2, the current signals obtained by the two light receiving elements 21 and 22 are converted into voltage signals by the current-voltage converters 23 and 24, respectively, and the low-pass filter 25 is used. Bandwidth is limited at 26. Next, the analog arithmetic circuit 27 performs arithmetic operations on these voltage signals to generate error signals. This error signal is digitized by the AD converter 29 controlled by the controller 28, and the phase compensation circuit 30 performs phase compensation. Further, the error signal is converted into analog by the DA converter 31 controlled by the control unit 28, band-limited by the low-pass filter 32, and then input to the driver 33. Then, the actuator 3 to be controlled
4 is driven according to the error signal amplified by the driver 33.

Further, in the servo controller as shown in FIG. 3, two voltage signals are similarly obtained by the circuits up to the low pass filters 25 and 26. These voltage signals are supplied to the AD converters 36 and 37 controlled by the control unit 35.
Are digitized respectively. Next, in the digital arithmetic circuit 38, the digital signals from the AD converters 36 and 37 are arithmetically operated to generate an error signal, and the error signal is phase-compensated in the phase compensation circuit 30. After that, the phase-compensated error signal is processed and the actuator 34 is driven, as in the above-described servo control device.

In the above servo control device, the servo control is performed by performing such a series of processes.

[0006]

However, since the former servo control device obtains an error signal by analog operation, it is necessary to provide the analog operation circuit 27 in the preceding stage of the AD converter 29. The circuit configuration tended to be complicated.

In the latter servo control device, the error signal is obtained by digital calculation, and it is not necessary to provide the analog calculation circuit 27, but the output signals of the light receiving elements 21 and 22 are individually digitized. Therefore, a plurality of AD converters 36 and 37 are required, and the circuit configuration tends to be complicated.

Therefore, in the conventional servo control device, the cost required for hardware has risen and the degree of freedom in design has been lowered.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a servo control device having a simple circuit configuration and a low cost.

[0010]

A servo control device for an optical disk apparatus according to the present invention uses a plurality of light receiving elements for receiving reflected light from the optical disk and converting the light into an electric signal, and an electric signal obtained by the light receiving element. In order to solve the above problems, in a servo control device of an optical disk device including an error signal generating unit that generates an error signal by performing an arithmetic process and a driving unit that drives a control target based on the error signal. , Is characterized by taking the following means.

That is, the servo control device of the optical disk device described above is configured such that the electric signal from each light receiving element is switched at high speed to guide the electric signal to one output path, and the electric signal passed through the first switching device is converted into a digital signal. A second switching device which operates in synchronism with the digital conversion device for converting into a digital signal and the first switching device, distributes the digital signal from the digital conversion device to a plurality of output paths corresponding to the respective light receiving elements, and guides it to the error signal generating device. And means.

[0012]

In the above construction, one of the electric signals from the plurality of light receiving elements is selected by the first switching means and is guided to the digital converting means, where it is converted into digital. Further, the digital signal is guided to the error signal generating means through the second switching means.

The second switching means is switched in synchronization with the first switching means and distributes the digital signal to a plurality of output paths corresponding to the respective light receiving elements, so that the first switching means sequentially switches. When it is done, it is switched accordingly. Therefore, the electric signal from each light receiving element is sequentially converted to digital and guided to the error signal generating means.

After that, when the error signal generating means performs arithmetic processing on the digital signal to generate an error signal, the error signal is returned to analog and then given to the driving means. As a result, the driving means operates according to the error signal.

As described above, according to the above construction, the signals from the respective light receiving elements are alternately converted into digital signals, so that a plurality of digital converting means, that is, AD converters, are provided according to the light receiving elements. There is no need. Further, since the arithmetic processing is performed with the digital signal as it is, it is not necessary to provide an analog arithmetic circuit.

[0016]

EXAMPLE An example of the present invention will be described below with reference to FIG.

As shown in FIG. 1, the servo control device according to this embodiment includes a light receiving element 1 and a current-voltage converter 3
4, low-pass filters 5 and 6, switch 7, and AD
The converter 8, the switch 9, the storage circuits 10 and 11, the digital arithmetic circuit 12, the control unit 13, the phase compensation circuit 14, the DA converter 15, the low-pass filter 16,
It is composed of a driver 17 and an actuator 18.

The light receiving elements 1 and 2 are detection elements for detecting the control light reflected by an optical disk (not shown),
For example, it consists of a photodiode. A reverse bias voltage is applied to these light receiving elements 1 and 2 in order to improve the response speed.

The voltage-current converters 3 and 4 are conversion circuits for converting the current signals output from the light receiving elements 1 and 2 into voltage signals, respectively. The low-pass filters 5 and 6 band-limit the output signals from the voltage-current converters 3 and 4, respectively, in order to prevent aliasing distortion from occurring in the digital conversion processing in the AD converter 8, and unnecessary high frequency components. Is designed to be removed.

The switch 7 has contacts 7a to 7c, and the contacts 7a and 7b are low-pass filters 5 and 6, respectively.
Of the AD converter 8, and the contact 7c is connected to the input side of the AD converter 8. The switch 7 switches the connection of the contacts 7a and 7c and the connection of the contacts 7b and 7c at high speed under the control of the control unit 13 to alternately output the output signals of the low-pass filters 5 and 6 to the AD converter 8. Has become
It has a function as a first switching means.

AD converter 8 serving as digital conversion means
Is a circuit that samples and quantizes the signal that has passed through the switch 7 and converts it into a digital signal.

The switch 9 has contacts 9a to 9c, the contact 9a is connected to the output side of the AD converter 8, and the contacts 9b and 9c are connected to the input sides of the memory circuits 10 and 11, respectively. . The switch 9 switches the connection of the contacts 9a and 9b and the connection of the contacts 9a and 9c at high speed under the control of the control unit 13 so as to separate the output signal of the AD converter 8 into two signals, which are respectively stored in the storage circuit 10. 11 and has a function as a second switching means.

The memory circuits 10 and 11 are composed of semiconductor memories, for example, and are circuits for temporarily holding the output signal of the AD converter 8. This memory circuit 10/11
Under the control of the control unit 13, the signals are output at the same timing.

The digital arithmetic circuit 12 as an error signal generating means is adapted to perform arithmetic processing such as subtraction on the signals passed through the memory circuits 10 and 11 to generate an error signal necessary for servo control. The control unit 13 controls switching of the switches 7 and 9 and operation control of the AD converter 8, the memory circuits 10 and 11 and the DA converter 15. In order to prevent the servo system from becoming unstable due to the phase delay of the error signal generated by the digital operation circuit 12, the phase compensation circuit 14 gives the error signal a phase margin to improve the steady-state characteristics of the servo system. Circuit.

The DA converter 15 is a circuit for weighting each bit of the digital error signal passed through the phase compensation circuit 14 to convert it into an analog signal. The low-pass filter 16 shapes the error signal from the DA converter 15 into a smooth waveform, and thus removes unnecessary harmonic components (quantization noise) from the error signal.

The driver 17 is a power amplifier which amplifies the error signal passed through the low pass filter 16 to a level required for the operation of the actuator 18. The actuator 18 as a drive unit is a device that drives an object to be controlled such as an objective lens (not shown). For example, a focus coil and a tracking coil are provided for driving the objective lens.

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

The current signals output from the light receiving elements 1 and 2 are converted into voltage signals by the current-voltage converters 3 and 4, respectively, and then band-limited by the low-pass filters 5 and 6 and output to the switch 7. .

In the switch 7, first, the contact 7a and the contact 7c are connected under the control of the controller 13, so that the output signal of the low-pass filter 5 is sent to the AD converter 8 and converted into a digital signal. At this time, in the switch 9, since the contact 9a and the contact 9b are connected in synchronization with the operation of the switch 7 under the control of the control unit 13, AD
The digital signal from the converter 8 is input to the storage circuit 10 and stored therein.

When the connection of the switch 7 is switched by the control of the control unit 13 and the contact 7b and the contact 7c are connected, the output signal of the low-pass filter 6 is converted into the AD converter 8.
And converted into a digital signal. At this time, the connection of the switch 9 is switched under the control of the control unit 13 similarly to the switch 7, and the contact 9a and the contact 9c are switched.
Since and are connected, the digital signal from the AD converter 8 is input to and stored in the storage circuit 11.

In this way, the analog signals output from the low-pass filters 5 and 6 are digitized alternately by the switches 7 and 9 and stored.

The digital signals stored in the memory circuits 10 and 11 are read out at the same time and the digital arithmetic circuit 12 is read.
Entered in. The digital arithmetic circuit 12 performs a predetermined arithmetic operation on both signals to generate an error signal. The error signal is subjected to phase compensation suitable for servo control by the phase compensation circuit 14, and then converted into an analog signal by the DA converter 15. The analog error signal is band-limited by the low-pass filter 16, further amplified by the driver 17, and given to the actuator 18. As a result, the actuator 18 operates by an amount corresponding to the error signal.

As described above, in the servo control device according to this embodiment, the output signals of the light receiving elements 1 and 2 are switched by the switch 7.
Thus, by performing time division at high speed, digital conversion processing can be performed by one AD converter 8. Further, in the above servo control device, since the switches 7 and 9 are switched in synchronism with each other, a digital signal corresponding to the output signals of the light receiving elements 1 and 2 can be obtained, and the digital arithmetic circuit 12 digitally outputs the signals. It is possible to perform arithmetic processing in. Therefore, it becomes possible to perform servo control with a simple circuit configuration.

[0034]

As described above, the servo control device for the optical disk device of the present invention comprises the first switching means for switching the electric signals from the respective light receiving elements at high speed to guide them to one output path, and the first switching means. An error signal is generated by operating the digital conversion means for converting the passed electric signal into a digital signal and the first switching means in synchronization with each other and distributing the digital signal from the digital conversion means to a plurality of output paths corresponding to the respective light receiving elements. And a second switching means that leads to the means.

As a result, the electric signals from the respective light receiving elements are alternately converted into digital signals, so that it is not necessary to provide a plurality of digital converting means according to the light receiving elements. Further, since the arithmetic processing is performed with the digital signal as it is, the analog arithmetic circuit becomes unnecessary. Therefore, the circuit configuration can be simplified, the cost of the servo control device of the optical disk device can be reduced, and the degree of freedom in circuit design can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a servo control device of an optical disk device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of a servo control device of a conventional optical disc device.

FIG. 3 is a block diagram showing a schematic configuration of a servo control device of another conventional optical disc device.

[Explanation of symbols]

 1 and 2 light receiving element 7 switch (first switching means) 8 AD converter (digital conversion means) 9 switch (second switching means) 12 digital arithmetic circuit (error signal generation means) 17 actuator (driving means)

Claims (1)

[Claims] 1. A plurality of light-receiving elements for receiving reflected light from an optical disc and converting it into an electric signal, and an error signal generating means for generating an error signal by subjecting the electric signal obtained by the light-receiving element to arithmetic processing. In the servo control device of the optical disk device, which includes: and a driving unit that drives the controlled object based on the error signal, a first switching unit that switches the electric signal from each light receiving element at high speed and guides the signal to one output path. A digital conversion means for converting the electric signal passed through the first switching means into a digital signal, and a digital conversion means operating in synchronization with the first switching means to output the digital signals from the digital conversion means to a plurality of output paths corresponding to the respective light receiving elements. A servo control device for an optical disk device, comprising: a second switching means for distributing and guiding the error signal to the error signal generating means.