KR0154953B1 - Focus servo apparatus for use in an optical disc playback system - Google Patents

Abstract

The present invention relates to a focus servo device of an optical disk reproducing apparatus, comprising: a first calculating unit (10) for detecting a focus error signal, a second calculating unit (20) for squarely summing a predetermined number of focus error signals, and a focus; A comparator 30 for detecting a deviation signal, a code determiner 50 for determining a sign of a focus deviation signal, a gain compensator 40 for outputting a gain compensation signal for focus, and a focus error signal Of the phase compensator 60 for compensating for the phase error, the controller 70 for generating a focus control signal, the drive signal generator 80 for generating a drive signal for focus, and the drive signal generator 80. A third operation unit 90 for summing output signals and disturbance signals, an optical pickup unit 100 for performing focus by driving in accordance with an output signal of the third operation unit 90, and an optical pickup unit 100 for focusing; On the optical disc after being focused It includes an optical detector 110, and a conversion amplification unit (120) for generating a feedback signal by converting and amplifying the current signal into a voltage signal of a predetermined level to generate a current signal corresponding to the reflected light intensity and configuration.

Therefore, the present invention has the effect of efficiently controlling the focus of the light for reading data accurately regardless of the characteristic change of the focus servo device due to long time use.

Description

Focus servo device of optical disc player

1 is a schematic block diagram showing a focus servo device of a conventional optical disk reproducing apparatus.

2 is a block diagram of a focus servo device of an optical disk reproducing apparatus according to a preferred embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10,20,90: calculation unit 30: comparison unit

40: gain compensation unit 50: sign determination unit

60: phase compensation unit 70: control unit

80: drive signal generator 100: optical pickup

110: light detector 120: conversion amplifier

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus servo device of an optical disk reproducing apparatus, and more particularly, to a focus servo device capable of accurately reading data recorded on an optical disk by keeping the focus constant regardless of the surface vibration of the optical disk. .

Typical optical disc players include a compact disc player (CDP), a laser disk player (LDP) and a compact disk graphic player (CDGP). A device capable of playing only audio, and a laser disk player and a compact disk graphic player are devices capable of simultaneously playing back video and audio.

On the other hand, in recent years, a video compact disc player capable of reproducing video and audio signals by compressing video and audio signals and recording them on a disc has also been developed and continues to develop to improve its performance.

In addition, such optical disc reproducing apparatuses reproduce images and / or audio recorded on optical discs and output them through a screen and / or a speaker, and thus have better signal quality than other conventional image and / or audio reproducing apparatus. And / or reproduce signals in sound quality, generate no noise due to irregular reproduction and modulation, have very little distortion, no ghosts, and random access.

On the other hand, in such an optical disc reproducing apparatus, light is used to read data, and in order to read data accurately recorded on the optical disc, it is necessary to focus light exactly on the data plane recorded on the optical disc. That is, the focus should be followed according to the vertical movement caused by the rotation of the optical disk.

In addition, a focus servo device is adopted to focus the light irrespective of the vertical vibration of the optical disc in the reproducing apparatus of such an optical disc, which is used to read the light used to read the data recorded on the optical disc face to the optical disc face. The optical pickup unit that focuses, that is, the objective lens is moved up and down in accordance with the movement of the optical disk to focus the light accurately on the surface of the optical disk, thereby reading the data recorded on the optical disk accurately.

1 is a schematic block diagram showing a focus control apparatus of a conventional optical disk player.

As shown in FIG. 1, a conventional focus control apparatus includes a controller 20 for compensating a focus error and generating a driving control signal according to the present invention, an actuator for driving according to an output signal provided from the controller 20, That is, the drive unit 30, the optical pickup unit 40 for outputting the detected value by executing the optical pickup for focus according to the drive of the drive unit 30, and the output value and the focus target value of the optical pickup unit 40 Comparing unit 10 for outputting the error value by calculating the.

As a result, the focus control apparatus of the optical disk reproducing apparatus uses the focus error value calculated by the difference between the output value of the optical pickup unit 40 and the preset focus target value, so that the control unit 20 obtains a gain margin. ) And a signal for driving the driver 30 so as to secure a phase margin. Accordingly, the driver 30 is driven to execute the focus control.

However, such a conventional focus servo device has a disadvantage in that the focus control gain in the focus servo device is changed due to disturbance due to long-term use, thereby failing to obtain correct servo characteristics.

Accordingly, the present invention has been devised to solve the conventional problems as described above, and an object of the present invention is to provide a constant control of the focus of light even when the focus control gain value of the focus servo changes with long-term use. The present invention provides a focus servo device capable of automatically adjusting a control gain value.

According to a preferred embodiment for achieving the above object, the present invention provides an optical disc reproducing apparatus in which the focal length of light is increased as surface vibration occurs in the optical disc due to disturbance or the like when data recorded on the optical disc is reproduced. In a focus servo device for appropriately performing light focus control when a change is made, a focus error value due to a difference between a preset target value for focusing the light and a feed-back signal value of the focus servo device is obtained. Obtains and outputs a first calculation unit, a second calculation unit which squares a predetermined number of focus error values provided from the first operation unit, sums the sum, and outputs the output signal of the second operation unit by comparing with a preset reference value; A comparator for detecting a compensation deviation and outputting a deviation signal according to the difference; A sign determiner for determining and outputting a sign of the focus compensation deviation in comparison with a previous previous output value, a gain compensator for outputting a focus gain compensation signal according to an output signal of the comparator and the sign determiner, and the first operator A phase compensator for compensating a phase error of an output signal of the control unit, a control unit for generating a focus control signal according to a gain compensation signal provided from the gain compensator and an output signal of the phase compensator, and a control signal provided from the control unit A driving unit generating unit for generating a driving signal according to the present invention; a third calculating unit configured to add an output signal of the driving signal generator; and an error signal according to surface vibration of the optical disk due to the disturbance; An optical pickup unit which drives in accordance with an output signal to focus light on the optical disk; A light detector for detecting light reflected on the optical disk after being focused and generating a current signal corresponding to the detected intensity of light, and converting and amplifying the current signal generated by the light detector into a voltage signal having a predetermined level. And a conversion amplifier configured to generate the feedback signal provided to the first calculator.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing a focus servo device of the optical disk reproducing apparatus according to the preferred embodiment of the present invention.

As shown in FIG. 2, the present invention provides a first operation unit 10 for detecting an error signal according to a difference between a focus target value and a feedback signal, and a predetermined number of error signals provided from the first operation unit 10. A second calculation unit 20 that squares and sums each, a comparison unit 30 that compares an output signal of the second operation unit 20 with a preset reference signal, and detects a focus deviation signal according to the preset reference signal; A signal determining unit 50 for determining the sign of the focus deviation signal by comparing the current output signal with the previous output signal, and for output according to the output signal of the comparing unit 30 and the output signal of the code determining unit 50. A gain compensator 40 for outputting a gain compensation signal, a phase compensator 60 for compensating a phase error according to an error signal provided from the first calculator 10, a gain compensator 40, and a phase compensator Generate the focus control signal according to the output signal of 60 The control unit 70, a drive signal generator 80 that generates a focus drive signal according to the output signal of the controller, and a third calculator 90 that adds the output signal and the disturbance signal of the drive signal generator 80. And an optical pickup 100 that performs focus by driving in accordance with an output signal of the third calculation unit 90 to pick up light, and corresponds to an intensity of light reflected on the optical disk after being focused by the optical pickup 100. A conversion amplification unit for generating a feedback signal provided to the first calculation unit 10 by converting and amplifying the photo detector 110 generating a current, and a current signal generated by the photo detector 110 into a voltage signal having a predetermined level. And includes a portion 120.

First, in order to accurately read the data recorded on the optical disc, it is necessary to pick up the light so that the light generated for reading the data is accurately focused on the data recording point on the optical disc.

The first calculating unit 10 is a difference between the focus target value for accurate focus and the feedback signal calculated according to the previous focus target value and the surface vibration of the optical disk, that is, the disturbance and the optical pickup unit 100, that is, the focus error signal. Is calculated and provided to the phase compensator 60 and the second calculator.

Accordingly, first, the second calculator 20 squares a predetermined number of focus error signals provided from the first operator 10 for a predetermined time and adds the sums to the comparator 30.

The comparator 30 detects the focus deviation signal by comparing the signal provided from the second calculator 20 with a preset reference signal that is to be maintained for focus control to obtain a gain compensator 40 and a code determiner ( 50). Then, the sign determiner 50 compares the output value of the current comparator 30 with the output value of the previous comparator 30 to determine the sign of the focus deviation signal. The sign of the focus deviation signal thus obtained determines the driving direction of the optical pickup unit 100 in the upward or downward direction. When the output value of the current comparator 30 is smaller than the output value of the previous comparator 30, The driving direction of the optical pickup unit 100 is maintained by maintaining the previous code, and when the current output value is large, the driving direction of the optical pickup unit 100 is changed by changing the previous symbol. The gain compensator 40 generates a gain compensation signal for focus according to the output signal of the comparator 30 and the output signal of the sign determiner 50.

Meanwhile, the phase compensator 60 including the lag compensator 62 and the lead compensator 64 compensates for the phase error from the focus error signal output from the first calculator 10 and controls the controller ( 70) That is, the lag compensator 62 compensates for the phase delay, and the lead compensator 64 compensates for the phase. As such, the signal whose phase is compensated by the phase compensator 60 is provided to the controller 70.

Accordingly, the controller 70 provides a focus control signal according to the output signals provided by the gain compensator 40 and the phase compensator 60 to the drive signal generator 80, and the drive signal generator 80. Provides a driving signal according to the output signal provided from the controller 70 to the third operation unit 90.

In addition, the third calculating unit 90 sums and outputs the output signal of the driving signal generating unit 80 and the signal according to the surface vibration of the optical disk, that is, the error signal caused by the disturbance. Accordingly, the optical pickup unit 100 is driven according to the output signal of the third calculating unit 90 to focus the light on the optical disk, and the optical detector 110 focuses the light according to the driving of the optical pickup unit 100. Accordingly, the intensity of the light reflected on the optical disk surface is detected and a current signal is generated accordingly.

The conversion amplifier 120 converts the current signal output from the light detector 11 into a voltage signal of a predetermined level, and amplifies the signal, and provides the amplified value to the first calculator 10 as a feedback signal.

On the other hand, in general, in the optical disk reproducing apparatus, the relationship between the surface vibration of the optical disk, the focus target value and the suppression value, that is, the focus gain, according to the surface vibration can be expressed as follows;

G1 ≒ D ÷ R ---------------- (2)

(R: Target value D: Suppression value for surface vibration G1: D)

Here, the focus target value is a constant value, and the surface vibration of the optical disk can also be obtained by experiment.

Then, the predetermined maximum suppression value can be determined in consideration of other disturbances that may occur from the outside.

As a result, the control unit 60 must be designed to generate a gain control signal, that is, a focus control signal, so that the suppression value G1 can be maintained at a predetermined value. As a result, since the gain control signal is determined by the gain compensation value of the gain compensator 40, the output value of the control unit 60 can maintain a predetermined value even if the characteristic of the focus servo device is changed.

As described above, the present invention has the effect of efficiently controlling the focus of light for reading data accurately regardless of the characteristic change of the focus servo device due to long-term use.

While the invention has been shown and described with reference to certain preferred embodiments, those skilled in the art will recognize that various modifications and changes can occur without departing from the spirit and scope of the invention as set forth in the following claims.

Claims (3)

When reproducing the data recorded on the optical disc in the optical disc reproducing apparatus, the focus servo apparatus is adapted to execute the focus control of the light appropriately when the focal length of the light changes as the surface vibration occurs in the optical disc due to disturbance or the like. A first calculation unit (10) for obtaining and outputting a focus error value due to a difference between a predetermined target value for focusing the light and a feedback signal value of the focus servo device; A second calculation unit 20 which squares a predetermined number of focus error values provided from the first calculation unit 10 and sums them and outputs the sums; A comparator 30 which detects a focus compensation deviation by comparing the output signal of the second calculator with a preset reference value and outputs a deviation signal according thereto; A sign determination unit (50) for comparing the output value of the comparison unit (30) with the previous output value of the comparison unit (30) to determine and output the sign of the focus compensation deviation; A gain compensator (40) for outputting a focus gain compensation signal according to the output signals of the comparator (30) and the sign determiner (50); A phase compensator (60) for compensating for the phase error of the output signal of the first calculator (10); A controller 70 generating a focus control signal according to a gain compensation signal provided from the gain compensator 40 and an output signal of the phase compensator 60; A drive signal generator 80 generating a drive signal according to a control signal provided from the controller 70; A third calculating unit (90) for adding the output signal of the driving signal generating unit (80) and the error signal according to the surface vibration of the optical disk due to the disturbance; An optical pickup unit (100) for driving in accordance with an output signal of the third calculating unit (90) to focus light on the optical disk; An optical detector (110) for detecting the light reflected on the optical disk after being focused in the optical pickup unit (100) and generating a current signal corresponding to the detected intensity of the light; Reproducing and reproducing an optical disk including a conversion amplifier 120 for generating the feedback signal provided to the first calculation unit 10 by converting and amplifying the current signal generated by the optical detector 110 to a voltage signal of a predetermined level The focus servo device of the device. The optical pickup unit of claim 1, wherein the sign determination unit 50 determines the sign of the focus compensation deviation by comparing the output value of the comparison unit 30 with the previous output value of the comparison unit 30. A focus servo device of an optical disk reproducing apparatus, characterized by determining the driving direction of 100) in an upward direction or a downward direction. The driving direction of the optical pickup unit 100 according to claim 1, wherein the driving direction is changed according to the sign of the focus deviation signal and the sign of the focus deviation signal determined by the sign determination unit 50. If the output value of the comparator 30 is smaller than the output value of the previous comparator 30, the previous sign is maintained to maintain the driving direction of the optical pickup unit 100, and if the current output value is large, the previous sign is maintained. The servo drive of the optical disc reproducing apparatus is characterized by changing the driving direction of the optical pickup unit (100).