KR100189898B1 - Tracking servo control method for an optical disc system - Google Patents

Abstract

The present invention relates to a tracking servo control method of an optical disk system, comprising: dividing a frequency of a tracking error signal output from an optical pickup at a predetermined ratio and outputting the square wave signal in the form of a square wave signal to a central processing unit; Counting by input; A step of giving a predetermined command to the servo controller by the central processing unit based on the count value; and a step of driving the servo motor by the servo controller based on the command; The accuracy of control can be maintained even at a high speed search without using.

Description

How to control tracking servos in optical disk systems

1 is a schematic block diagram showing a general optical disk system.

2 is a waveform diagram illustrating a problem of the conventional tracking servo control method.

3 is a circuit diagram of an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

101: drive unit 102: optical pickup

103: signal amplification unit 104: data processing unit

105, 310: central processing unit 106: servo control unit

301: Diode

302, 303, 304, 305: D flip flop

306, 307: differential circuit 308, 309: inverter

The present invention relates to a tracking servo control method of an optical disc system.

In general, an optical disk system refers to a system to which an optical disk drive such as a compact disk read only memory drive (CD-ROM drive) or a compact disk player (CD player) is applied. Servos used in an optical disk drive in an optical disk system include a focus servo, a tracking servo, a sled servo, and a spindle servo. There are four things. The focus servo is a servo that controls the optical system of the optical pickup so that the focus of the laser beam irradiated from the optical pickup is aligned on the Pit of the optical disk. The tracking servo is a servo that controls the optical system of the optical pickup so that the laser beam of the optical pickup follows the track. The slad servo is a servo that controls the slad motor that moves the optical pickup from the inner circumference to the outer circumference of the optical disk. The spindle servo is a servo that controls the spindle motor so that the optical disk not only rotates at a constant linear velocity (CLV) but also brakes with high accuracy. Such an optical disk system is in a trend of increasing speed, and the maintenance of reliability is an important issue.

1 is a schematic block diagram showing a general optical disk system. As shown in FIG. 1, the driving unit 101 drives the optical pickup 102 and the turn table (not shown), and the data signal and the servo signal generated by the optical pickup 102 are signal amplified. The unit 103 is amplified by, for example, an RF amplifier. The data signal amplified by the signal amplifier 103 is input to the central processing unit 105, for example, a CPU (Central Processing Unit) through the data processing unit 104, for example, a digital signal processor. In addition, the servo signal amplified by the signal amplifier 03 is input to the central processing unit 105 through a servo controller, for example, a servo signal processor. The central processing unit 105 controls the data processing unit 104 and the servo control unit 106, and the servo control unit 106 drives the driving unit 101 with the servo control signal.

In the optical disk system as shown in FIG. 1, the tracking servo control method includes projecting two beams having a phase difference of 180 ° to each other across the corresponding pit of the optical disk, and then applying the reflected light difference to the optical pickup 102. It is to control the position of the optical system. The photometric difference appears as the output difference of two optical sensors, for example two photodiodes of the optical pickup 102, and is called a tracking error signal. In such a tracking servo control method, conventionally, after the tracking error signal from the optical pickup 102 is amplified by the signal amplifier 103, the rising edge of the amplified signal is raised by the servo controller 106. ) And the falling edge (Fal1ing edge) output the detected square wave signal. The central processing unit 105 counts and processes the tracking square wave signal, and then issues a command related to tracking to the servo controller 106. Accordingly, the servo control unit 106 drives a sled motor in the driving unit 101 as a tracking servo control signal. In the conventional tracking servo control method, since the servo controller 106 directly detects a rising edge and a falling edge of the amplified signal to form a tracking square wave signal, The tracking square wave signal is broken.

2 is a waveform diagram illustrating a problem of the conventional tracking servo control method. As shown in FIG. 2, as the search speed of the optical pickup (102 in FIG. 1) increases, the period of the tracking error signal from the optical pickup (102 in FIG. 1) becomes shorter. In addition, the period of the tracking square wave signal from the servo controller (106 in FIG. 1) is also shortened. From this point in time, an area in which the waveform of the tracking square wave signal is broken is generated. In FIG. 2, reference numeral 201 denotes an area where the waveform of the tracking square wave signal is broken during the fast search. In order to solve such a problem, a conventional sensor is attached around the slad motor in the driving unit (101 in FIG. 1). That is, the central processing unit (105 in FIG. 1) maintains the accuracy of the tracking servo control by reflecting the output of the sensor during the high-speed search. However, there is a problem in that the system design is complicated as well as attaching a separate sensor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a tracking servo control method capable of maintaining control accuracy even at a high speed search without using a separate sensor.

In order to achieve the above object, a tracking servo control method of an optical disk system according to the present invention comprises: dividing a frequency of a tracking error signal output from an optical pickup at a predetermined ratio and outputting the square wave signal in the form of a square wave signal; Inputting a signal to the central processing unit and counting the signal, the central processing unit giving a predetermined command to the servo controller based on the count value, and the servo controller driving the slad motor based on the command. It is characterized by.

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

3 is a circuit diagram for implementing an embodiment of the present invention. Referring to the operation of Figure 3 as follows. First, the tracking error signal from the optical pickup (102 in FIG. 1) is half-wave rectified through the diode 301. Here, each of the D flip-flops 302, 303, 304, and 305 divides the frequency of the signal input to the clock CLK terminal into two and outputs them to the Q terminal. Accordingly, the 1D flip-flop 302 receives a signal obtained by dividing the frequency of the half-wave rectified signal by 2, and the 2D flip-flop 303 receives a signal obtained by dividing the frequency of the half-wave rectified signal by 4, and the 3D flip-flop 304 ) Denotes a signal in which the frequency of the half-wave rectified signal is divided by eight, and the 4D flip-flop 305 outputs a 16-divided splatter signal in which the frequency of the half-wave rectified signal is divided. The reason for dividing the frequency of the tracking error signal in this manner is to prepare for the fast search of the optical pickup (102 in FIG. 1). Of course, the half-wave rectified signal is converted into a square wave signal while passing through the 1D flip-flop 302. The 16 divided signal is differentiated by a capacitor 306 and a resistor 307 to detect a rising edge and a falling edge. Two inverters 308 and 309 amplify and output only the signal corresponding to the rising end, and do not output the signal corresponding to the falling end. Accordingly, the central processing unit 310 receives one pulse for every 16 tracking error pulses from the optical pickup (102 in FIG. 1). The central processing unit 310 counts the input tracking square wave signal, and then the central processing unit issues a predetermined command to the servo controller (106 in FIG. 1) based on the count value. Of course, the tracking control algorithm of the central processing unit 310 should reflect that one pulse is input per 16 tracking error pulses from the optical pickup (102 in FIG. 1). The servo control unit 106 of FIG. 1 drives the slad motor based on a command from the central processing unit 310. Thus, by dividing the frequency of the tracking error signal into the central processing unit 310, it is possible to maintain the accuracy of control even at a high speed search without using a separate sensor.

The present invention is not limited to the above embodiment, and its use and improvement are possible at the level of those skilled in the art.

As described above, according to the tracking servo control method of the optical disk system according to the present invention, it is possible to maintain the precision of the control even at high speed without using a separate sensor.

Claims (4)

Dividing the frequency of the tracking error signal output from the optical pickup at a predetermined ratio, outputting the square wave signal in the form of a square wave signal, inputting the square wave signal to a central processing unit, and counting the square wave signal; And a step of giving a predetermined command to the beam control unit and driving the slad motor by the servo control based on the command. The optical disc system according to claim 1, wherein the tracking error signal is an electrical signal for the reflected light difference after projecting two beams having a phase difference of 180 degrees to each other across the corresponding pit of the optical disc. Tracking servo control method. Half-wave rectifying the tracking error signal output from the optical pickup, dividing the frequency of the half-wave rectified signal at a predetermined ratio, outputting it in the form of a square wave signal, and detecting a rising edge of the square wave signal. And inputting and counting the detected signal to a central processing unit, giving a predetermined command to the servo controller by the central processor based on the count value, and the servo controller is configured to operate the slad motor based on the command. A tracking servo control method for an optical disc system, characterized in that it comprises a step of driving. 4. The optical disc system according to claim 3, wherein the tracking error signal is an electrical signal for the reflected light difference after projecting two beams having a phase difference of 180 degrees to each other across the corresponding pit of the optical disc. Tracking servo control method.