KR19990050072A - How to Adjust Servo Gain of Optical Disc System - Google Patents

Abstract

The present invention relates to a servo gain adjustment method of an optical disc system that adjusts loop gain of a servo control circuit that performs servo control on an optical pickup unit that converts reflected reflected light into an electrical signal after injecting a laser beam into the disk. A first step of generating an RF signal from an electrical signal output from the optical pickup unit and detecting a level of the generated RF signal; A second step of determining whether the optical pickup unit traces a track surface on which data on the disk is recorded or a track surface on which data is not recorded, based on a change in the level of the RF signal; When the optical pickup unit traces a track surface on which data on the disk is recorded, the servo control circuit performs servo control on the optical pickup unit based on a first loop gain, and the optical pickup unit performs the optical pickup unit. When tracing a track surface on which data on the disk is not recorded, the servo control circuit includes a third step of performing servo control on the optical pickup unit based on a second loop gain.

Description

How to Adjust Servo Gain of Optical Disc System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo gain adjustment method for an optical disc system, and more particularly, to a servo gain adjustment method for adaptively adjusting loop gains to a track surface on which data on a disk is recorded and a track surface on which data is not recorded. .

In general, an optical disc system is equipped with various servo functions. For example, a focusing servo, a tracking servo, an optical system servo, and an APC (Automatic Power Control) servo are representative servo functions.

Here, the focusing servo described above is a servo that controls the track surface of the disk to be located within the depth of focus of the laser beam generated by the optical pickup unit even when the disk is vibrated because the optical pickup unit tracks the track of the disk while performing non-contact playback. The tracking servo is a function that controls the optical pickup unit to trace along the track center of the disc.

In addition, the optical system servo serves to move the entire optical pickup unit in a radial direction, and the APC serves to maintain a constant amount of reflected light of the laser beam on the disk.

As is well known, such a servo function is executed by a feedback control circuit which detects an output response and obtains an operation signal compared with a reference input, and then determines an operation amount accordingly, and a feedback control circuit for executing the servo function. The characteristics required for designing are the normal characteristics (normal deviation), stability (decayability), response speed, and the like.

Here, the normal characteristics (normal deviation), stability (decayability), and response speed required for designing a feedback control circuit for executing the servo function are how the loop gain of the system is set in the end. The general loop gain setting is set by experiment and the like.

That is, in the servo control circuit of the optical disc system, the optical response unit detects an output response based on light reflected from the disc after the predetermined laser beam is incident on the disc, and compares the output response with a reference level to generate an operation signal. The loop gain is set so that the normal characteristics, stability, and response speed of the system can be satisfied while repeating the process of determining the manipulated value accordingly.

On the other hand, in setting such a loop gain, conventionally, a predetermined laser beam is incident on the track surface on which the disk data is recorded, and then the output response is made based on the light reflected from the track surface on which the data is recorded. The loop gain was set based on the detection.

By the way, in the case of a disc capable of recording / reproducing in recent years, not only a disc on which data is recorded but also a disc on which data is not recorded. In the case of disc editing, as shown in Fig. 1, a track surface A on which data is recorded on one disc and a track surface B that do not exist coexist. Nevertheless, in the servo control circuit of the conventional optical disc system, since the loop gain is set using the disc on which the data is recorded, the track in which the optical pickup unit does not record the data, in particular, during reproduction of the disc as shown in FIG. Servo error occurs when the surface is traced or traversed.

That is, the reflected light reflected from the track surface on which the data is recorded and the reflected light reflected from the track surface on which the data is not recorded are naturally different from each other. Although the output response characteristic based on the reflected light and the output response characteristic based on the reflected light reflected from the track surface on which data is not recorded are different from each other, conventionally the reflected light reflected from the track surface on which data is recorded is different. Since the loop gain of the servo control circuit is set from the output response characteristic based on this, there is a problem that a servo error occurs when tracing or traversing a track surface on which data is not recorded.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and when a disc is reproduced, the track surface on which the data on the disc is recorded and the track surface on which the data is not recorded are discriminated and looped adaptively with or without data recording. It is an object of the present invention to provide a servo gain adjusting method for adjusting gain.

In order to achieve the above object, the present invention provides an optical disc system for adjusting a loop gain of a servo control circuit that performs servo control on an optical pickup unit for converting reflected light into electrical signals after injecting laser light into the disc. A servo gain adjusting method, comprising: a first step of generating an RF signal from an electrical signal output from the optical pickup unit and detecting a level of the generated RF signal; A second step of determining whether the optical pickup unit traces a track surface on which data on the disk is recorded or a track surface on which data is not recorded, based on a change in the level of the RF signal; When the optical pickup unit traces a track surface on which data on the disk is recorded, the servo control circuit performs servo control on the optical pickup unit based on a first loop gain, and the optical pickup unit performs the optical pickup unit. When tracing a track surface on which data on the disk is not recorded, the servo control circuit includes a third step of performing servo control on the optical pickup unit based on a second loop gain.

1 is a diagram showing a data recording structure of a disc;

2 is a hardware configuration diagram for performing a servo gain adjustment method of the present invention;

3 is a detailed flowchart of a servo gain adjustment method according to a preferred embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10; Optical pickup unit 20; Error signal detector

30; A / D conversion unit 40; Digital signal processor

50; D / A converter 60; Driving part

70; RF amplifier 80; RF level detector

90; Disk 100; Host computer

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

2 shows a servo control circuit for performing the servo gain adjustment method of the present invention.

In FIG. 2, the servo control circuit includes an optical pickup unit 10, an error signal detector 20, an A / D (Analog / Digital) converter 30, a digital signal processor 40, and a D / A converter ( 50, the driver 60, the RF amplifier 70, the RF level detector 80, and the disk 90, and the host computer 100 adjusts the loop gain of the digital signal processor 40.

The error signal detector 20 detects a servo error signal from the optical pickup unit 10 and provides the servo error signal to the A / D converter 30. The A / D converter 30 converts an analog servo error signal into digital and provides the digital signal to the digital signal processor 40.

The digital signal processing unit 40 digitally processes the servo error signal based on the loop gain provided from the host computer 100, generates a servo control signal based on the servo error amount, and generates a digital signal to the D / A converter 50. The D / A converter 50 converts the analog signal into an analog signal and provides the converted signal to the driver 60.

The driver 60 performs servo control on the optical pickup unit 10 according to a servo control signal converted into an analog signal. Meanwhile, the RF amplifier 70 generates, amplifies, and outputs an RF signal from an electrical signal provided from the optical pickup unit 10, and the RF level detector 80 detects the level of the RF signal to the host computer 100. to provide.

The host computer 100 determines whether the track of the disk 90 currently being tracked by the optical pickup unit 10 is the surface on which data is recorded, based on the level of the RF signal input from the RF level detector 80. After that, the first loop gain corresponding to the track surface on which data is recorded is set and provided to the digital signal processing unit 40, and the second loop gain corresponding to the track surface on which data is not recorded is set to digital. It is provided to the signal processor 40.

3 is a detailed flowchart illustrating a servo gain adjustment method according to an exemplary embodiment of the present invention, which will be described below with reference to FIG. 2.

First, in the normal reproducing mode (S1), the optical pickup unit 10 converts the reflected light that is reflected after the laser beam is incident on the track of the disc 90 to be provided to the RF amplification unit 70. .

The RF amplifier 70 generates and amplifies and outputs an RF signal from an electrical signal input from the optical pickup unit 10, and the RF level detector 80 detects the level of the RF signal of the RF amplifier 70. It is provided to the host computer 100 (S2). At this time, when the optical pickup unit 10 traces the track of the disc 90, when the trace surface on which the data is recorded is traced, an RF signal of a predetermined pulse waveform is generated, but no data is recorded. When the track surface is traced, an RF signal with little change in waveform is generated.

Therefore, if the level of the signal input from the RF level detection unit 80 has been fixed at a constant level even though the preset time T has elapsed (S3), the current optical pickup unit 10 Determines that the track surface on which data is not recorded is traced, and if the level of the signal input from the RF level detector 80 is a predetermined pulse waveform (S3), the current optical pickup unit 10 It is judged that the track surface recorded is being traced.

When the optical pickup unit 10 is currently tracing a track surface on which data is not recorded, the host computer 100 determines the first loop gain set correspondingly to the digital signal processing unit 40 when the optical pickup unit 10 traces the track surface on which data is not recorded. (S4), the optical pickup unit 10 traces the track surface on which the data is recorded, and provides the digital signal processor 40 with the second loop gain set corresponding thereto (S5).

On the other hand, the error signal detection unit 20 generates a servo error signal from the electrical signal provided from the optical pickup unit 10 and provides it to the A / D conversion unit 30, the A / D conversion unit 30 is analog The servo error signal is converted into digital and provided to the digital signal processor 40.

The digital signal processor 40 digitally processes the servo error signal, generates a servo control signal based on the servo error amount, and provides the servo control signal to the D / A converter 50, wherein the first signal is provided from the host computer 100. The servo control signal based on the loop gain or the second loop gain is generated and provided to the D / A converter 50, and the D / A converter 50 converts the analog signal into an analog signal and provides it to the driver 60. do.

Therefore, the driver 60 performs servo control on the optical pickup unit 10 according to the servo control signal converted into an analog signal.

As described above, the present invention discriminates the track surface on which the data on the disk is recorded and the track surface on which the data is not recorded upon disc playback, and adaptively adjusts the loop gain according to whether data is recorded or not. It is effective to prevent servo error.

Claims (2)

In the servo gain adjustment method of an optical disc system for adjusting the loop gain of a servo control circuit which performs servo control on an optical pick-up unit that converts reflected light reflected back into an electrical signal after the laser beam is incident on the disk. A first step of generating an RF signal from an electrical signal output from the optical pickup unit and detecting a level of the generated RF signal; A second step of determining whether the optical pickup unit traces a track surface on which data on the disk is recorded or a track surface on which data is not recorded, based on a change in the level of the RF signal; When the optical pickup unit traces a track surface on which data on the disk is recorded, the servo control circuit performs servo control on the optical pickup unit based on a first loop gain, and the optical pickup unit performs the optical pickup unit. When tracing a track surface on which data on the disk is not recorded, the servo control circuit includes a third step of performing servo control on the optical pickup unit based on a second loop gain, the servo gain of the optical disk system. Adjustment method. The method of claim 1, wherein the second step is: Determining that the optical pickup unit traces a track surface on which data on the disk is recorded if the level of the RF signal changes within a predetermined time; And determining that the optical pickup unit traces a track surface on which the data on the disk is not recorded when the RF signal level is fixed for the predetermined time.