KR960014656B1 - Tracking pull-in method & apparatus of optical disk system - Google Patents

Abstract

calculating maximum value by measuring zero crossing interval of the track crossover signal during one turn of a disc; setting a tracking pull-in point reference value using the maximum value; comparing the measured value of the interval with the tracking pull-in point reference value; checking the level of 4SUM signal if the measured value is not less than the reference value; trying the tracking pull-in if the level of 4SUM signal is in 'LOW' logical state. The apparatus comprises: a 4 divisional photo diode; the first and the second photo diode; an adder; a subtracter; a pulse shaper; a processor; a tracing servo controller; an actuator drive; and a tracking pull-in device.

Description

Tracking pull-in method and apparatus in optical disk system

1 is a diagram showing a movement path of a spot caused by an eccentricity.

FIG. 2A shows the track crossing signal, and FIG. 2B shows the sum of the signals from the four photodiodes.

3a to 3e show signal waveforms according to the position of the beam spot, FIG. 3a is a cross-sectional view of a disk, FIG. 3b is a track crossing signal, 3c is a sum of signals from four photodiodes, and 3d is an actuator The driving current, Fig. 3E, shows the sum of the signals from the four photodiodes after the waveform conversion.

4 is a block diagram according to an embodiment of a tracking retracting apparatus according to the present invention.

5 is a flowchart illustrating a tracking ingress method according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking pull method and apparatus for an optical disk system, and more particularly, to a tracking pull method and apparatus using a signal obtained by adding a track crossing signal and four photodiode signals (hereinafter, referred to as 4SUM signal). .

Typically, discs have small widths formed in a spiral track from the inner circumference to the outer circumference. FIG. 1 is a diagram illustrating a movement path of a beam spot due to an eccentricity, and it can be seen that 10 times of special cross section occurs from P1 to P10 during one rotation of the disk.

When the disc rotates, as shown in FIG. 1, the track crossing signal appears as shown in FIG. 2a due to the variation of the center and the rotation center of the disc, and at this time, the 2SUM signal of the four-segment photodiode detecting the RF signal is shown in FIG.

In the conventional tracking lead-in method for the optical disc system, as shown in FIG. 2A, the tracking on point is taken at a point between a to c or close to b of the track crossing signal generated by the eccentricity. That is, the processor (CPU) measures the distance between the zero crossing points by using the track crossing signal as an input, and attempts to track tracking by taking the midpoint of the maximum value as the entry point.

However, in this case, even when the tracking point of the track crossing signal (Fig. 2a) is precisely found and tracked in, the actual spot on the disc is located between a to e on the disc cross section (Fig. 3a). As a result, the amount of overshoot of the track error signal and the time required for stabilization of the tracking servo are different immediately after the tracking entry. In some cases, the pulling operation may fail.

The tracking servo controls the optical spot to be located in the groove (point c in Figure 3a) to read the data. That is, the control is performed such that the track crossing signal appearing in accordance with the position of the optical spot approaches zero (3 in FIG. 3B).

The control characteristics of the tracking servo according to the position of the optical spot when entering by the conventional tracking pulling method are as follows.

One). When the optical spot is in the section between a and b of FIG. 3A: The tracking servo moves the actuator in the outer direction since the optical spot is located on the inner side from the point c. Therefore, the tracking servo drives the actuator with (+) current (1 to 2 in Fig. 3d) to move the actuator in the circumferential direction, and the track crossing signal is increased from 1 to 2 as in Fig. 3d. Will change to In other words, the control proceeds in the direction in which the track crossing signal increases immediately after the entry, and the overshoot amount increases, and the time taken for stabilization becomes long. Therefore, the tracking servo becomes unstable immediately after the entry.

2). When the optical spot is in the section between d and e of FIG. 3a: The tracking servo moves the actuator in the inner direction since the optical spot is located on the outer side from the point c. Therefore, the tracking servo drives the actuator with (-) current (section 4 to 5 in Fig. 3d) to move the actuator in the inner circumferential direction, and the track crossing signal increases from 4 to 5 as in Fig. 3d. Will change to In other words, the control proceeds in the direction in which the track crossing signal increases immediately after the entry, and the overshoot amount increases, and the time taken for stabilization becomes long. Therefore, the tracking servo becomes unstable immediately after the entry.

3). When the optical spot is placed in the section between b and d of FIG. 3a: Since the optical spot is located exactly on the groove, the general control is performed in which the track crossing signal becomes smaller when the actuator is driven according to the magnitude of the track crossing signal. Therefore, the tracking servo becomes stable immediately after the drawing.

As described above, when the track pitch or the width of the pit is narrowed to increase the recording density, the position of the optical spot immediately after the entry has a significant effect on the tracking entry. There is a problem that becomes difficult.

Accordingly, an object of the present invention is to find the entry point using the track crossing signal, to check the level of the signal from the four photodiodes so that the optical spot is always located in the groove (groove) at the entry point The present invention provides a tracking entry method for stable entry.

Another object of the present invention is to provide an apparatus which is most suitable for realizing the above-mentioned tracking lead-in method in an optical disk signal.

In order to achieve the above object, in the optical disc system, the tracking retracting method according to the present invention measures a zero crossing interval of a track crossing signal during a single turn of the disc to obtain a maximum value. A second step of setting a tracking entry point reference value using the maximum value: a third value for comparing the measured measurement value of the zero crossing interval of the track crossing signal with the tracking entry point reference value set in the second step again Step 4: Checking the level of the 4SUM signal when the measured value is equal to or greater than the reference value in the third step: And tracking in the level when the level of the 4SUM signal is 'low' logic in the fourth step It characterized in that it comprises a fifth step to try.

In order to achieve the above object, in the optical disc signal, the tracking retracting apparatus according to the present invention is a four-segment photodiode for reading data recorded on the optical disc and converting it into an electrical signal: first and second photodiodes for the tracking chair. : An adder for generating a 4SUM signal by adding a signal output from the four-segment photodiode: To generate a track crossing signal by obtaining a difference signal between an output signal of the first photodiode and an output signal of the second photodiode Subtractor: Pulse shaper for making the 4SUM signal output from the adder into a square wave: Instructing tracking entry by monitoring the 4SUM signal output from the pulse shaper and the track crossing signal output from the subtractor, and controlling all the pulling operations. Processor for: Tracking actuator by the instruction of the processor A tracking servo controller and an actuator driver for controlling driving and controlling the driving of the tracking actuator by a track crossing signal output from the subtractor immediately after the drawing; and a track which is turned on by an inlet command of the processor and output from the subtractor And a switch for applying a crossing signal to the tracking servo controller and the actuator driver.

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

4 is a block diagram according to an embodiment of the tracking lead-in apparatus according to the present invention in an optical disk signal.

The configuration of the block diagram shown in FIG. 4 includes four-part photodiode 10 for reading data from an optical disk, first and second photodiodes 11 and 12 for tracking control, and four-part photodiode ( The adder 2 makes 4SUM signals (a + b + c + d) from the signals a, b, c, and d output from 10), and the 4SUM signals, which are square waves output from the adder 2, as square waves. A first subtractor 1 for generating a track crossing signal TES by subtracting the output signal of the second photodiode 12 from the output signal of the first photodiode 11 and the pulse shaper 5 to be produced; A switch 6 for switching the output signal TES of the first subtractor 1 under the control of the processor 7 to form a square wave, and a second signal for producing an RF signal from the output signal of the quadrature photodiode 10. 2 subtracter 3, the 4SUM signal output from the pulse shaper 5 and the track crossing signal output from the first subtracter 1 are monitored and Inputs the processor 7 for instructing the locking inlet to the switch 6, the tracking servo controller and the actuator driver 8, the tracking lead signal output from the processor 7 and the track crossing signal output from the switch 6; The tracking servo control part and actuator drive part 8 which control the tracking actuator 9 so that a beam spot may track | track a track, and the tracking actuator 9 are comprised.

FIG. 5 is a flowchart illustrating a tracking insertion method according to the present invention. Steps 100 to 120 are steps of obtaining a maximum value by measuring a zero crossing interval of the track crossing signal during one rotation of the disc. Step 140 is a step of setting the tracking incoming point reference value using the maximum value obtained in step 120, and steps 150 and 160 are again set in step 130 the measured value measuring the zero crossing interval of the track crossing signal Comparing with the tracking entry point reference value, step 170 is a step of checking the level of the 4SUM signal when the measured value is greater than or equal to the reference value in step 160 and steps 180 through 200 are levels of the 4SUM signal in step 170. In this 'low' logic state, tracking ingress is attempted.

Next, the operation of the present invention will be described with reference to FIGS. 1 to 5.

As shown in FIG. 1, when the center of rotation and the center of the disc do not coincide and eccentricity is generated by Δr, the beam spot is crossed. At this time, the track crossing signal is the same as in FIG. 2a, the track in point is in the sections a to c of the track crossing signal, and the actual optical spot is located in the section of P1 to P10 or P5 to P6 in FIG. Holding on to a tracking on point is easy to pull in.

In FIG. 1, the section having the beam spot positions P1 to P10 or P5 to P6 corresponds to the sections a to c in the track crossing signal of FIG. 2a, and thus attempts to find the sections a to c.

First, referring to FIG. 4, the processor (CPU) 7 inputs the track crossing signal TES generated by the eccentricity, and checks the period of the track crossing signal by using the built-in timer and counter. Calculate In addition, by monitoring the level of the 4SUM signal output from the pulse shaper 5, when the optical spot is located in the groove, the tracking servo control section and the actuator driving section 8 are inputted, and the switch 6 is turned on. After the drawing, the tracking servo controller and the actuator driver 8 directly receive the track crossing signal TES to control the tracking actuator 9.

This will be described with reference to the flowchart shown in FIG. 5.

Step 100 is an initial value setting step, and sets the maximum value and the reference value to '0'.

In step 110, the processor 7 measures the interval at which the track crossing signal crosses zero (that is, the signal level is changed from − → +) while the disc is rotated in one step. Find the maximum value.

In step 130, the tracking entry point reference value is set using the maximum value obtained in step 120. In other words, the maximum value obtained in step 120 becomes the longest section crossing zero in the track crossing signal, and half of the maximum value becomes an intermediate point between b and c sections. A value corresponding to half of the maximum value is set as the tracking entry point reference value.

In step 140, it is determined whether the disc has completed one revolution and returns to step 110 even when the disc is not completed. In step 140, the disc proceeds to step 150.

In step 150, as in step 110, a zero crossing interval is measured, and the measured value is compared with the reference value set in step 130 (step 160). Caught. If the measured value is smaller than the reference value in operation 160, the process returns to operation 150.

In step 170, the level of the 4SUM signal is checked so that the optical spot is always located in the groove immediately after the inlet. If the level of the 4SUM signal is 'low' logic (steps 3c and 3e) in operation 170, the tracking spot is attempted because the optical spot is located on the groove (operation 180). If the level of the 4SUM signal is 'high' in step 170, it is again determined whether the disc has completed 3 turns (step 190). If the 3 rotations are not completed, the process returns to step 150 and completes the 3 turns. If it is determined that the tracking incoming has failed (step 200).

The present invention is applicable to all reproduction magneto-optical disk signals. The focus error detection method of the signal to which the present invention is applied is astigmatism, and the tracking error detection method uses a three beam method.

As described above, the tracking entry method and apparatus according to the present invention in the optical disk signal has an advantage that stable tracking entry can be achieved because tracking entry is attempted when the beam spot is located in the groove.

In addition, when the tracking in is performed when the beam spot is located in the groove, the overshoot amount of the track crossing signal is reduced immediately after the tracking in, so that the tracking servo can be stabilized in a short time.

Claims (3)

The first step of obtaining the maximum value by measuring the zero crossing interval of the track crossing signal during one rotation of the disc: The second step of setting a tracking entry point reference value using the maximum value obtained in the first step: again the track A third step of comparing the measured value measuring the zero crossing interval of the crossing signal with the tracking entry point reference value set in the second step; when the measured value is equal to or larger than the reference value in the third step, A fourth step of checking a level; and a fifth step of attempting tracking in when the level of the 4SUM signal is 'low' in the fourth step. Four-segment photodiode for reading data recorded on an optical disk and converting it into an electrical signal: First and second photodiodes for tracking control: Adder for generating a 4SUM signal by adding signals output from the four-segment photodiode: A subtractor for generating a track crossing signal by obtaining a difference signal between an output signal of the first photodiode and an output signal of the second photodiode: a spreader for forming a 4SUM signal output from the adder into a square wave: in the pulse shaper A processor for instructing tracking induction by monitoring the output 4SUM signal and the track crossing signal output from the subtractor, and controlling all the pulling operations: controlling the driving of the tracking actuator by the pulling command of the processor, and immediately after the pulling. The track by the track crossing signal output from the subtracter; A tracking servo controller and an actuator driver for controlling the driving of a king actuator; and a switch for applying a track crossing signal, which is turned on by an inlet command of the processor and output from the subtractor, to the tracking servo controller and the actuator driver. Tracking inlet device characterized in that. The method of claim 1, wherein the processor checks the period of the track crossing signal to calculate a track on point, and checks the level of the 4SUM signal to enter the tracking servo controller and the actuator driver when an optical spot is located in the groove. Authorize the command, Tracking inlet device, characterized in that to switch on.