JPS63175234A - Generating device for tracking error signal of optical disk player - Google Patents

Abstract

PURPOSE:To increase a range of the tracking servo control by providing the polarity to the pulse signal obtained from a phase difference detecting means in response to the phase relation between output signals of two elements set at the same column position against the tracking direction of a 4-split photodetecting element. CONSTITUTION:The output signals of elements 1a and 1d or 1b and 1c of a 4-split photodetecting element 1 are compared with the threshold value and converted into the binary signals. Then EXOR gates 4 and 5 secure the exclusive OR of said binary signals for each value between those diagonal elements 1a and 1d or 1b and 1c of the element 1. Then a pulse signal X is produced with polarity corresponding to the phase relation between the output signals of the elements 1a and 1d or 1b and 1c set at the same column position to the track direction with the pulse width equivalent to the phase difference between output signals P and Q of both gates 4 and 5. Then a tracking error signal is obtained by integrating the signal X. In such a way, a range of the tracking servo control can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking error signal generation device for an optical disc player.

First and fifth, a conventional example of a tracking error signal generation device for an optical disc player is shown. In this device, each element 1a to 1d of the 4-split light receiving element 1 of the pickup is
are connected to comparators 3a to 3d via IV (current-voltage) converters 2a to 2d, respectively.

Each of the comparators 3a to 3d shapes the waveform of the input signal and converts it into high and low level binary signals. EXOR gates 1 to 4 take the exclusive OR of each output signal of comparator 3a and 3G, and EXOR gate 5 takes the exclusive OR of each output signal of comparator 3a and 3G.
The exclusive OR of each output signal b and 3d is taken. EXO
The output of the R gate 4 is connected to the clock input terminal cp of the D flip-flop 7, and also to the D flip-flop 70 via the inverter 6a.
It is connected to the reset terminal R of the knob 8. The output of EXOR gate 5 is the clock input terminal c of D flip-flop 8.
p.

It is also connected to the reset terminal R of the D flip 70 tube 7 via the inverter 6b. D flip-flop7.
A voltage Vcc is supplied to each input faD and the set terminal S of 8. Each output terminal Q of the flip-flop 70 tube 7°8 is connected to a differential amplifier 9, which subtracts the output level of the flip-flop 8 from the output level of the flip-flop 7 and applies the result to an LF-F (low-pass filter). >10, and a tracking error signal is output from LPFlo.

As shown in FIG. 5, the four-division light-receiving cable 1 is divided into a cross shape, and each of the elements 1a to 1d is arranged so that the cables 1a and 1b and the elements iC and 1d are positioned symmetrically with respect to the track direction of the disk. Then, the cable 1b and the IC are placed on the upstream side of the pit, and the element 1 is placed on the upstream side of the pit.
a and ld are located on the downstream side of the pit.

In the tracking error signal generation device having such a configuration, the current flowing through each element 1a of the four-part light receiving element 1 is I-
It is converted into a C voltage by the V converter 2a, and the voltage 1 to 1
- It is converted into a binary code having a square waveform by the comparator 3a depending on the magnitude relationship with the value. Similarly, the current flowing through each of the other elements 1b to 1d of the four-division light receiving element 1 is also I.
-2 The output voltages of the IV converters 2b to 2d are respectively converted into voltages by the converters 2b to 2d, and the output voltages of the IV converters 2b to 2d are converted to binary signals by the comparators 3b to 3d, respectively. Due to this conversion to the 211a signal, even if the output current of the elements 1a to 1d fluctuates due to asymmetry in the light intensity distribution of the spot on the light receiving element 1 or asymmetry due to movement, the pit array and the irradiation beam are Phase information is detected accurately. Therefore, the binary codes (a to d) output from the comparators 3a to 3d depending on the pit row, the irradiation beam, and the phase state are as shown in FIG.

By taking the exclusive OR of the binary signal a outputted from the comparator 3a and the binary signal SC outputted from the comparator 3C, the signal P is obtained by taking the exclusive OR of the binary signal a outputted from the comparator 3a, and the binary signal @ outputted from the comparator 3b. The signal Q
As shown in FIG. 6, the signal P is inverted by the inverter 6a to become the signal P, and the signal Q is inverted by the inverter 6b to become the signal 0.

The level QA at the output terminal Q of the D flip-flop 7 is equal to the signal P.
The rising edge of signal 0 causes a high level, and the falling edge of signal 0 causes a low level. Further, the level QB of the output GaQ of the D flip-flop 8 becomes high level at the rising edge of the signal Q, and becomes low level at the falling edge of the signal QP.

When the irradiation beam spot is located on the center line of the pit row, the binary signals a and d, and the binary code C, are equal, as shown in FIG. 6 (II). , the binary signals @b, c lead the binary signals a, d by 1/4 period, so the signals P and Q become equal, and the signals P and ○ become equal, and D
The output levels QA and QB of the flip 70 tube 7.8 are maintained at a low level. Therefore, since the output X of the differential amplifier 9 becomes the reference level, the level of the tracking error signal Y obtained from the LPFIO becomes O.

When the irradiation beam spot is shifted from the center line of the pit row, the signal P output from the EXOR gate 4 is shifted from the element 1a, as shown in FIGS. 6(I) and (II[).
The signal Q output from the EXOR gate 5 becomes a phase difference pulse of the diagonal components of the IC, and the signal Q obtained from the flip-flop 7 is a phase difference pulse of the diagonal components of the elements 1b and 1d. This is the pulse width representing the deviation of the irradiation beam spot in one direction with respect to the pit row. Also, the reliability obtained from flip-flop 8 is F4.
QB represents the amount of deviation of the irradiation beam spot from the pit row in the other direction in the disk radial direction, and is the pulse width.

Therefore, the signals Q^ and QB are sent to the differential amplifier 9 and then to the LP
A tracking error signal Y is obtained via the FIO.

However, in such a tracking error signal generation device, when the phase difference between the signals P and Q exceeds the pulse width of the signals P and Q, a state occurs where A and QB are alternately at a level of Since the pulse width signal X representing the amount of deviation of the beam spot with respect to the pit row cannot be obtained from the output of the differential amplifier 9, there is a drawback that the control range of the tracking servo is narrow.

1. An object of the present invention is to provide a lagging signal generation device that can expand the control range of a tracking servo.

The tracking error signal generating device of the present invention compares the output signal of each element of the 4-split light-receiving element with a threshold value and converts the output signal into a binary code, and 2 The exclusive OR of the value codes is taken by each EXOR gate, and the pulse width is equivalent to the phase difference between the output signals of the two EXOR gates, depending on the phase relationship of the output signals of each element located in the same column in the track direction. It is characterized by generating a pulse signal with a different polarity and integrating the pulse signal to obtain a tracking error signal.

! -1-1 Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 shows a tracking error generation device according to the invention. In this figure, the same parts as those in the device shown in FIG. 5 are given the same reference numerals, and a D flip-flop 14 and AND gates 1 to 15.degree. 16 are newly provided.

The input end of the D flip-flop 14 is the comparator 3b.
The input terminal Cp is connected to the output of the comparator 3C. A voltage VCC is supplied to the set terminal S and the reset terminal R. The AND gate 15 outputs the signal QA output from the output terminal Q of the D flip-flop 7 and the signal Qc output from the output terminal Q of the D flip flop 70 tube 14.
The AND gate 16 takes the logical product of the signal Qa output from the output terminal Q of the D flip processor 18 and the signal Qc output from the output rAQ of the D flip 70 tube 14. Each output signal of AND gates 15 and 16 is supplied to differential amplifier 9. The rest of the configuration is the same as the device shown in FIG.

In the tracking error generation device according to the present invention having such a configuration, Flip Flora! The operation from 7.8 to the signals QA and QB outputted is the same as that of the conventional device shown in FIG. 5, and there are C as shown in FIG.

Further, as shown in FIG. 2, the comparator 3b at the rising edge of the signal C output from the comparator 3C
The signal output from the flip-flop 14 is the output D
The signal Qc is output from aQ, and the inverted signal of the signal Qc is output from the output terminal 0 of the flip-flop 14 as the signal Qc.

When the irradiation beam spot (It) is located on the center line of the pit row 12 as shown in FIG.
As shown in II), the output levels QA and QB of the D flip-flop 7.8 remain low, so the signals Qc and C
The output level Q of AND gate 15 and 16 is independent of IC.
X, QY become low level, and the level of racking error signal Y becomes O.

Further, as shown in FIG. 3, if the irradiation beam spot (I) is shifted from the center line of the pit row 12 to the inside of the disk, for example, as shown in FIG. A pulse-width signal QA is obtained that does not represent the deviation of the irradiation beam spot with respect to the pit row in one direction in the radial direction.At this time, at the rising edge of the signal C, the signal C is at a low level, so the flip-flop 14 The signal Qc output from the 1g Q
c becomes high level. Therefore, signal Q equal to signal QA
× is obtained from the AND gate 15, and the output signal QY of the AND gate 16 becomes low level.

These signals Qx and QY are sent to the differential amplifier 9 and then to the LPFI
A tracking error signal Y is obtained via O. What phase difference between signals P and Q, i.e., signal ′i′″iQ
When the pulse width of A becomes larger than the pulse widths of signals P and Q, a situation occurs in which the signals QA and QO are alternately high, but since the signal @Qc is low, the output signal QY of the AND gate 16 is low. level, so it is possible to prevent the influence of the signal QB on the output of the differential amplifier 9.

For example, if the irradiation beam spot (I[l) is shifted from the center line of the pit row 12 to the outside of the disk,
As shown in FIG. 2 (I[I), a signal QB with a pulse width representing the deviation of the irradiation beam spot with respect to the pit row in the other direction in the radial direction of the disk is obtained from the seven lip-flop 7. At this time, at the rising edge of the signal C, the signal b_G; is at a high level, so the signal Qc output from the flip-flop 14 is at a high level, and the signal Qc is at a low level.

Therefore, the signal @QvIfi which is equal to the signal Y no QB is 1q from the AND gate 16, and the output signal Q of the AND gate 15 is
is at a low level. The signals Q× and 'OY are passed through a differential amplifier 9 and then through PFlo to form a tracking error signal YSm. When the phase difference between signals P and Q, that is, the pulse width of signal QB becomes larger than the pulse widths of signals P and Q, a state occurs in which signals QA and QB are alternately high level, but since signal Qc is low level, Since the output signal Qx of the AND gate 15 is at a low level, the influence of the signal QA on the output of the differential amplifier 9 can be prevented.

FIGS. 4(a) and 4(b) show RF (iQ frequency) signals and ]-
The waveform of the racking error signal (solid line) is shown. The broken line in FIG. 4(b) shows the waveform of the tracking error signal in the case of the conventional device, and a more accurate tracking error signal can be obtained than in the conventional device.

In the embodiment of the present invention described above, the signal is supplied to the input terminal of the D flip-flop 14, and the input terminal C
Although the signal C is supplied to the input terminal Cp, the present invention is not limited thereto. For example, the signal d may be supplied to the input terminal of the flip-flop 14, and the signal a may be supplied to the input terminal Cp.

As described above, in the tracking error signal generation device of the present invention, the pulse width r corresponding to the phase difference between the output signals P and Q of the two EXOR gates, and each element at the same rank in the pit row direction. Since a pulse signal X4r with a polarity corresponding to the phase relationship of the output signals of (la, 1d, or lb, IC) is generated, even if the phase difference between signals P and Q exceeds the pulse width of signals P and Q, the irradiation beam spot will be It is possible to obtain a signal 8× of the pulse width representing the deviation with respect to the pit row.

Therefore, by using a tracking error signal obtained by integrating the pulse signal

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of each part of the device shown in FIG. 1, FIG. 3 is a diagram showing the relationship between the irradiation beam spot and the pit, and FIG. The figure is a waveform diagram showing an RF signal and a tracking error signal when a beam spot crosses a pit row by the device shown in FIG. 1, and FIG. 5 is a circuit diagram showing a conventional example of a tracking error signal generating device.
FIG. 6 is a waveform diagram showing the operating state of each part of the device shown in FIG. Explanation of symbols of main parts 1...Four division light receiving element 4.5...EXOR gate 7.8.14...D flip-flop 22...
・・・Differential amplifier

Claims (1)

[Claims] A tracking error signal generation device for an optical disc player that irradiates a light beam onto a track consisting of pit rows on an optical disc surface and generates a tracking error signal according to the reflected light. a four-division light-receiving element which is divided into four parts and arranged so that the disk radial direction and track tangential direction are the dividing directions and receives the reflected light, and each output signal of one diagonally-related element in the four-division light-receiving element. a first conversion means that compares each output signal with a threshold value and converts each into a binary signal; and compares each output signal of the other diagonally related element in the four-split light receiving element with a threshold value and converts each output signal into a binary signal. a second conversion means, a first EXOR gate that takes an exclusive OR of each binary signal of the first conversion means, and a second EXOR gate that takes an exclusive OR of each binary signal of the second conversion means; Said first and second EXO
The phase difference detection means includes: a phase difference detection means for generating a pulse signal having a pulse width corresponding to the phase difference of each output signal of the R gate; and an integration means for integrating the pulse signal to obtain the tracking error signal. A tracking error signal generation device characterized in that a pulse signal obtained from the four-division light-receiving element has a polarity according to a phase relationship of output signals of two elements located in the same column in the track direction in the four-division light-receiving element.