KR19990012007A - Tracking balance adjuster of optical disc system - Google Patents

Abstract

According to the present invention, when the laser beam accurately traces the track center of the disk with the signal surface of the disk rotating in CLV positioned within the depth of focus of the laser beam, the level of the tracking error signal is set to a predetermined reference potential level value ( A tracking balance adjusting device of an optical disc system for adjusting T2), comprising: a first A / D converter (311) for converting a tracking error signal into a digital signal and outputting the digital signal; A second A / D converter 312 converting the tracking error signal into a digital signal and outputting the digital signal; A low pass filter 313 for removing noise of the digital tracking error signal output from the second A / D converter 312; A control unit (319) for detecting a tracking offset value by detecting the intermediate level value of the digital tracking error signal provided from the low pass filter (313), and calculating a difference between the reference potential level value and the intermediate level value; A register 315 for storing a tracking offset value detected by the controller 319; A subtractor 316 for calculating and outputting a difference between the digital tracking error signal output from the first A / D converter 311 and the tracking offset value provided from the register 315; A first switch (S2) for connecting the output terminal of the low pass filter (313) and the control unit (319) or the control unit (319) and the register (315) by the control unit (319); And a second switch S1 for controlling whether or not the register 319 and the subtractor 316 are connected under the control of the controller 319.

Description

Tracking balance adjuster of optical disc system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking balance adjusting device of an optical disc system, and more particularly to a digital tracking balance adjusting device capable of digitally performing a process for adjusting tracking balance.

An optical disc system is a system for non-contact reproduction of a recording bit signal engraved on a disc by a laser beam and digital signal processing thereof. In such an optical disk system, in particular, the optical pickup unit performs a function of converting light reflected from the signal surface of the disk into an electrical signal after the laser beam is incident on the signal surface of the disk.

1 is a detailed structural diagram of an optical pickup unit.

In FIG. 1, digital information is recorded along the track on the optical disc 11, and a laser beam focused by the objective lens 12 is incident on the signal surface of the disc 11. As shown in FIG. In addition, the focusing actuator coil 13 drives the objective lens 12 in the vertical direction so that the signal surface of the disk 11 is located within the depth of focus of the laser beam, and the tracking actuator coil 14 The objective lens 12 is driven in the left and right directions so that the laser beam for optical pickup can accurately trace along the track of the disk 11.

As such, driving the objective lens 12 such that the signal surface of the disk 11 is located within the depth of focus of the laser beam is commonly referred to as focusing servo, and the laser beam for optical pickup accurately traces along the track of the disk 11. Driving the objective lens 12 is called tracking servo.

Here, the tracking servo uses a tracking error signal indicating the extent to which the laser beam is out of the track of the disk 11, which will be described below with reference to FIG.

As shown in FIG. 2, the tracking servo device includes a tracking error signal detector 210, a phase compensation amplifier 220, a tracking driver 230, and a tracking actuator coil 240 to perform the following operations. do.

In FIG. 2, the tracking error signal detector 210 detects the tracking error signal from the output signal of the optical pickup unit 100 and provides the tracking error signal to the phase compensation amplifier 220, and the phase compensation amplifier 220 compensates for the phase. And amplifies the tracking driver 230 to provide it to the tracking driver 230. The tracking driver 230 drives the tracking actuator coil 240 to correspond to the output voltage level of the phase compensation amplifier 220, and the tracking actuator coil 240 rotates the objective lens inside the optical pickup unit 100. Perform tracking servo by adjusting in the right direction.

By such a tracking servo device, the laser beam of the optical pickup unit 100 can accurately trace along the track center of the disk 11. At this time, the tracking servo is performed based on the tracking error signal, and when the tracking error signal is 0, the laser beam of the optical pickup unit 100 should be positioned at the track center.

As such, when the tracking error signal is 0, the operation of adjusting the laser beam of the optical pickup unit 100 to be positioned at the track center is generally referred to as tracking balance adjustment. However, in the conventional tracking balance adjustment, after the variable resistor is provided at the input terminal of the phase compensation amplifier 220, the variable resistance is adjusted so that the tracking error signal is symmetrical with respect to the center potential in the tracking servo-off state. .

However, since the conventional tracking balance adjustment is performed analogously, there is a problem that accurate balance adjustment is difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a digital balance adjustment device that enables a more accurate tracking balance adjustment by digitally processing the tracking balance adjustment.

In order to achieve the above object, the present invention provides a level of a tracking error signal when the laser beam accurately traces the track center of the disk while the signal surface of the disk rotating with CLV is located within the depth of focus of the laser beam. A tracking balance adjusting device of an optical disc system for adjusting a set reference potential level value, the apparatus comprising: a first A / D conversion unit converting the tracking error signal into a digital signal and outputting the digital signal; A second A / D converter converting the tracking error signal into a digital signal and outputting the digital signal; A low pass filter for removing noise of the digital tracking error signal output from the second A / D converter; A control unit for detecting a tracking offset value by calculating a difference between the reference potential level value and the intermediate level value after detecting an intermediate level value of the digital tracking error signal provided from the low pass filter; A register for storing a tracking offset value detected by the controller; A subtractor for calculating and outputting a difference between the digital tracking error signal output from the first A / D converter and the tracking offset value provided from the register; A first switch for connecting the output terminal of the low pass filter and the control unit or the control unit and the register under control of the control unit; And a second switch for controlling whether the register is connected to the subtraction period under the control of the controller.

1 is a general structural diagram of an optical pickup unit;

2 is a schematic configuration diagram of a tracking servo device;

3 is a detailed configuration diagram of a tracking balance adjusting device according to a preferred embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

310: tracking error detection unit 311,312: A / D conversion unit

313: low pass filter 314,315: register

316: subtractor 317: tracking filter

318: D / A converter 319: control unit

330: tracking driving unit 340: focusing servo unit

350: Spindle Servo S1, S2, S3: Switch

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

3 shows a tracking balance adjusting device according to a preferred embodiment of the present invention.

As shown in FIG. 3, the tracking balance adjusting device includes a tracking error detector 310, two A / D (Analoge / Digital) converters 311 and 312, a low pass filter 313, two registers 314 and 315, Three switches S1, S2, S3, subtractor 316, tracking filter 317, D / A converter 318, control unit 319, tracking driver 330, focusing servo unit 340, spindle ( spindle) servo unit 350 and control unit 319.

In FIG. 3, the tracking error detector 310 generates a tracking error signal indicating the degree to which the laser beam for the optical pickup deviates from the track of the disc. The A / D converter 311 and the A / D converter 312 are respectively connected to the output terminal of the tracking error detector 310, and the A / D converter 311 digitally outputs a tracking error signal during tracking servo. The A / D converter 312 converts the tracking error signal to digital at the time of tracking balance adjustment.

The low pass filter 313 is connected to the output terminal of the A / D converter 312 to remove noise included in the tracking error signal. The register 315 also stores a tracking offset value generated when the tracking balance is not adjusted. The switch S1 is turned off at the time of tracking offset value calculation under the control of the controller 319, and is turned on when the tracking offset value calculation is completed.

The switch S2 is operated by the control of the control unit 319, and connects the output terminal of the low pass filter 313 and the control unit 319 when sampling the digital tracking error signal to detect the tracking offset value. After the tracking offset value is detected at 319, the controller 319 and the register 315 are connected. The switch S3 is turned off at the time of tracking offset value calculation under the control of the controller 319, and is turned on when the tracking offset value calculation is completed.

The control unit 319 stores a reference potential level value T2 for calculating a tracking offset in an internal memory, and after sampling the tracking error signal provided from the low pass filter 313, the reference potential stored in the internal memory. The tracking offset value is calculated based on the level value, and control is made whether or not the switches S1, S2, and S3 are connected.

The subtractor 316 calculates the difference between the output of the A / D converter 311 and the tracking offset value provided via the switch S2. The register 314 temporarily stores the tracking signal with the adjusted tracking balance provided from the subtractor 316. The D / A converter 318 converts the tracking error signal into an analog. The tracking driver 330 is connected to the switch S3 to drive the tracking actuator coil to correspond to the tracking error signal.

The focusing servo unit 340 drives the objective lens so that the signal surface of the disc is located within the depth of focus of the laser beam, and the spindle servo unit 350 controls the disc to rotate at CLV.

The operation description of the tracking balance adjusting device according to the embodiment of the present invention configured as described above is as follows.

First, to adjust the tracking balance, the controller 319 turns off the switches S1 and S3 and then controls the switch S2 to connect the output terminal of the low pass filter 313 and the input terminal of the controller 319. In addition, the controller 319 operates the focusing servo unit 340 and the spindle servo unit 350. As the spindle servo unit 350 operates, the disc (not shown) rotates with CLV (Constant Liner Velocity), and the tracking error detection unit 310 is a laser of the optical pickup unit (not shown). A tracking error signal indicative of the extent to which the beam is off track of the disc is detected and provided to the A / D converter 312.

The A / D converter 312 converts the input tracking error signal into a digital signal and provides it to the low pass filter 313, and the low pass filter 313 removes and outputs noise of the input digital tracking error signal. The output signal of the low pass filter 313 is provided to the controller 319, and the controller 310 samples the level of the digital tracking error signal input from the low pass filter 313 at predetermined cycle intervals to store the internal memory. Store in

After performing the sampling operation for a predetermined time, the control unit 319 compares / computes each sampling value stored in the internal memory to each other and calculates the maximum value Tmax and the minimum value Tmin of the tracking error signal, respectively. Detect.

After detecting the tracking error signal of the maximum level and the tracking error signal of the minimum level, the controller 319 calculates the sum (Tmax + Tmin) of the two values and then calculates the intermediate value T1 of the calculated result value again.

When the calculation on the intermediate value T1 is completed, the control unit 319 detects the preset reference potential level value T2 from the internal memory for adjusting the tracking balance, and then the intermediate value T1 and the preset reference potential. The difference (T1-T2 = Tc) of the level value T2 is calculated.

Here, it can be said that the difference Tc between the above-described intermediate value T1 and the preset reference potential level value T2 corresponds to a tracking offset value that causes the tracking balance to be out of order.

Therefore, the controller 319 controls the switch S2 to connect the controller 319 and the register 315, and then provides the calculated tracking offset value Tc to the register 315.

The register 315 stores the tracking offset value Tc provided from the control unit 319 in the internal memory. Thereafter, the controller 319 turns on the switch S1 to connect the output terminal of the register 315 and the subtractor 316, and turns on the switch S3 to operate the tracking servo.

As the tracking servo is operated, the tracking error signal is input to the A / D converter 311, and the A / D converter 311 converts the input tracking error signal into digital and provides the subtractor 316. Here, the tracking offset signal output from the aforementioned A / D converter 311 may include a tracking offset component.

Accordingly, the subtractor 316 removes the offset value included in the tracking error signal. That is, the subtractor 316 subtracts and outputs the tracking offset value Tc provided from the register 315 from the tracking error signal output from the A / D converter 311.

The tracking error signal output from the subtractor 316 is temporarily stored in the register 314 and then provided to the tracking filter 317, which tracks the phase of the tracking error signal and adjusts the gain. To the D / A converter 318.

The D / A converter 318 converts the tracking error signal input from the tracking filter 317 into an analog and provides it to the tracking driver 330. Therefore, the tracking driver 330 drives the tracking actuator coil (not shown) based on the analog tracking error signal input.

As described above, the present invention allows the tracking balance adjustment to be automatically processed digitally, thereby making it possible to perform more accurate tracking balance adjustment.

Claims (2)

When the signal beam of the disk rotating in CLV is located within the depth of focus of the laser beam, when the laser beam accurately traces the track center of the disk, the level of the tracking error signal is set to the reference potential level value T2. In the tracking balancer of an optical disc system that adjusts to: A first A / D converter 311 converting the tracking error signal into a digital signal and outputting the digital signal; A second A / D converter 312 converting the tracking error signal into a digital signal and outputting the digital signal; A low pass filter 313 for removing noise of the digital tracking error signal output from the second A / D converter 312; A control unit (319) for detecting a tracking offset value by calculating a difference between the reference potential level value and the intermediate level value after detecting an intermediate level value of the digital tracking error signal provided from the low pass filter (313); A register 315 for storing a tracking offset value detected by the controller 319; A subtractor (316) for calculating and outputting a difference between the digital tracking error signal output from the first A / D converter (311) and the tracking offset value provided from the register (315); A first switch (S2) for connecting the output terminal of the low pass filter (313) and the control unit (319) or the control unit (319) and the register (315) under the control of the control unit (319); And a second switch (S1) for controlling whether or not the register (319) and the subtractor (316) are connected under the control of the control unit (319). The method of claim 1, The controller 319 is: The digital tracking error signal provided from the low pass filter 313 is sampled at a predetermined time interval, stored in an internal memory, and then compared / computed with the sampling values. The value of the tracking error signal is the maximum value (Tmax). ) And the minimum value Tmin, respectively, the sum of the detected maximum value and the minimum value, and then the sum of the maximum value and the minimum value are divided by 2 to detect the intermediate level value of the digital tracking error signal. Tracking tracking device of the system.