KR19980014066A - Tracking servo apparatus of optical pickup - Google Patents

Abstract

The present invention relates to a tracking servo apparatus for an optical pickup capable of simultaneously performing a tracking servo by a single tracking servo apparatus when the phase difference between the E and F beams which are side beams in the 3-beam type optical pickup apparatus is ± 180.

The present invention is characterized in that the tracking error signal phase inversion means for inverting the phase of the tracking error signal generated by the tracking error signal generation means, the comparison means for comparing the high frequency signal read from the disk with the reference signal and outputting the resultant signal, An integrating means for integrating a signal output from the integrating means and an integration value output from the integrating means to discriminate a phase difference of a side beam and generate a tracking error signal or a selection signal of an inverted tracking error signal according to the discrimination result, And tracking error signal selection means for selecting and outputting the tracking error signal or the inverted tracking error signal output from the tracking error signal generation means and the tracking error signal phase inversion means, respectively, in accordance with the tracking error signal selection signal outputted from the tracking error signal selection means .

Description

Tracking servo apparatus of optical pickup

FIG. 1 is an example of a tracking servo system of a conventional optical pickup. FIG.

FIG. 2 is a waveform diagram of a high-frequency signal RF and a tracking error signal TE of FIG. 1; FIG.

FIG. 3 shows another example of a tracking servo apparatus of the conventional optical pickup.

FIG. 4 also shows the high frequency signal and the tracking error signal and the inverted tracking error signal waveform of FIG. 3; FIG.

FIG. 5 is a block diagram of a tracking servo apparatus of an optical pickup according to the present invention; FIG.

FIG. 6 is a detailed circuit diagram of each part of FIG. 5;

7 is a waveform diagram of each input / output waveform when the phases of E and F signals in FIG. 5 are 180. FIG.

8 is a waveform diagram of each input / output waveform when the phases of E and F signals in FIG. 5 are -180.

DESCRIPTION OF THE REFERENCE NUMERALS

100: optical detecting unit 101: tracking error signal generating unit

102: tracking error signal phase inverting unit 103:

104: integrating unit 105: microcomputer

106: tracking error signal selection unit 107: phase compensation unit

108: drive unit 109: tracking actuator

DETAILED DESCRIPTION OF THE INVENTION [

The present invention relates to a tracking servo for an optical pickup. More particularly, the present invention relates to a tracking servo for an optical pick-up, To a tracking servo apparatus of a pickup.

FIG. 1 is an example of a conventional tracking servo apparatus of the conventional optical pickup. As shown in FIG. 1, the optical pickup apparatus 1 includes a photodetector 1 for detecting the peripheral beams E and F among the light reflected from the disc, A subtractor 2 for converting the side beam current into a voltage and subtracting the side beam current to generate a tracking error signal TE; And a drive unit 4 for driving the tracking actuator 5 in accordance with the signal output from the phase compensation unit 3. [

The operation of the tracking servo system of the conventional optical pickup will be described in detail with reference to FIG.

First, when the phase of the side beam is 180. + -. Alpha., The side beam current detected by each of the photodetectors E and F in the photodetector 1 is changed to a voltage in the subtractor 2 and subtracted, Is output as the tracking error signal TE shown in FIG. 2 (B).

The tracking error signal TE thus outputted is supplied to the drive unit 4 after the phase compensation is performed in the phase compensation unit 3. The drive unit 4 drives the tracking actuator 5 in accordance with the signal Tracking is performed.

Here, if tracking is turned on at the rising edge portion of the tracking error signal as shown in (b) of FIG. 2, the RF reads the pit surface shown in (A) of FIG.

If the tracking error signal is an inverted signal (the phase difference of the E and F signals is -180, the tracking is turned on in (a), (b), and the RF reads the mirror surface (disk) The state becomes absent.

Next, FIG. 3 is another example of the conventional tracking servo apparatus.

A photodetector 1 for detecting a perimeter beam of light reflected from a disk; a photodetector 1 for converting the side beam current detected by the photodetector 1 into a voltage and subtracting the side beam to generate a tracking error signal; A phase inverting unit 6 for inverting the phase of the tracking error signal outputted from the subtracting unit 2 and a tracking error signal output from the phase inverting unit 6, And a driving unit 4 for driving the tracking actuator 5 in accordance with the signal output from the phase compensating unit 3. The phase compensating unit 3 compensates the phase of the tracking error signal

The operation of the conventional tracking servo apparatus configured as described above will be described with reference to FIG.

First, when the phase difference of the side beams E and F detected by the photodetector 1 is -180, if the tracking is turned on as described above, the RF reads the mirror surface, so that the phase inverting unit 6 ) Inverts the phase of the tracking error signal so that the tracking error signal having the phase difference of -180 as shown in (b) of FIG. 4 becomes 180 as shown in (c).

The RF will then read the pit when tracking on.

That is, when the tracking is on, the servo is caught at the rising portion of the tracking error signal ⓐ 'b' 'ⓒ', and the RF reads the mirror surface. However, in the -TE, the servo is applied to the rising portion ⓐ ⓒ, It's about reading.

However, in the conventional tracking servo apparatus, the phase inverting unit is added or removed in hardware according to the phase of the TE. At this time, if the phase difference of E and F is -l80 in the tracking servo apparatus without the phase inversion unit, There was an unreadable problem.

In addition, there is an inconvenience that a system in which the phase difference of E and F is -180. Is inconvenient to insert a phase inversion section or readjust the fixed GRATING of the pickup.

In the above, GRATING is a component for adjusting the phase difference of E and F as an optical component of a pickup.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical pickup apparatus of a three-beam type, in which when the phase difference between the E and F beams, which are side beams, is ± 180, The tracking servo apparatus of the optical pickup being capable of simultaneously performing the tracking servo by the tracking servo apparatus of the optical pickup.

The technical means for achieving the object of the present invention is to convert the side beam current detected in the light detecting means for detecting light reflected from the disk into a voltage and subtract the converted voltage to generate a tracking error signal A tracking error signal phase inversion means for inverting the phase of the tracking error signal generated by the tracking error signal generation means and a comparison error means for comparing the high frequency signal read from the disk with a reference signal and outputting the resultant signal, And an integrating unit for integrating the signal output from the comparing unit and an integrated value output from the integrating unit to discriminate the phase difference of the side beam and output a selection signal of a tracking error signal or an inverted tracking error signal according to the discrimination result And the tracking error signal selection signal outputted from the microcomputer and the microcomputer La made of the tracking error signal generating means and the tracking error signal selecting means for the tracking error signal from the phase shift means selecting the tracking error signals and outputs a tracking error signal or the inverted output.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 5 is a block diagram of the tracking servo system of the optical pickup according to the present invention.

A photodetector 100 for detecting a side beam reflected from the disk, a photodetector 100 for converting the side beam current detected by the photodetector 100 into a voltage and subtracting the converted voltage to generate a tracking error signal A tracking error signal phase inverting unit 102 for inverting the phase of the tracking error signal generated by the tracking error signal generating unit 101 and a tracking error signal phase inverting unit 102 for inverting the phase of the high frequency signal An integration unit 104 for integrating the signal output from the comparison unit 103, and an integration unit 104 for integrating the integration value output from the integration unit 104, A microcomputer 105 for discriminating the phase difference of the side beams and generating a selection signal of a tracking error signal or an inverted tracking error signal according to the discrimination result, A tracking error signal selector 106 for selecting and outputting a tracking error signal or an inverted tracking error signal respectively output from the tracking error signal generator 101 and the tracking error signal phase inverter 102 according to a selection signal, A phase compensator 107 for compensating a phase of a signal output from the tracking error signal selector 107 and a drive unit 109 for driving the tracking actuator 109 with a signal output from the phase compensator 107 108).

The comparison unit 103 includes a coupling capacitor C2 for removing a direct current component of a high frequency signal read from the disc and outputting only a signal component, and a comparator for comparing a signal through the coupling capacitor C2 with a reference signal And a comparator 103a.

The tracking error signal selector 106 selects the tracking error signal from the tracking error signal generator 101 and the tracking error signal phase inverting unit 102 according to a tracking error signal selection signal output from the microcomputer 105 And a multiplexer 106a for selecting and outputting a tracking error signal or an inverted tracking error signal.

The operation and effect of the tracking servo system of the optical pickup according to the present invention will be described in detail with reference to FIGS. 6 to 8. FIG.

First, the high frequency signal RFI generated according to the phase difference of the E and F beams at the tracking ON state is obtained by removing the DC component from the coupling capacitor C2 in the comparator 103 and outputting only the signal component from the comparator 103a The high frequency signal read out from the disk is the same as that of FIG. 7 (a), and the above-mentioned signal is outputted to the comparing unit 103, The DC component is removed by the coupling capacitor C2 in the first comparator 103a and the comparator 103a compares the reference signal with the reference signal to obtain a signal as shown in FIG.

When this signal is integrated by the integrator in the integrator 104, the signal becomes a high signal as shown in FIG. 7 (d), and is input to the microcomputer 105.

That is, when the phase difference of the E and F beams is 180, the signal input to the microcomputer 105 becomes a high signal (5 V). In this case, the microcomputer 105 outputs a selection signal for selecting a non-inverted tracking error signal And applies it to the error signal selection unit 106.

On the other hand, the current corresponding to the E and F beams reflected from the disk is converted into a voltage in the subtraction unit 101 and subtracted to generate a tracking error signal TE, Are input to the tracking error signal selection unit 106 and the tracking error signal phase inverting unit 102, respectively.

Accordingly, the tracking error signal phase inverting unit 102 amplifies the tracking error signal by non-inverting and inverting the phase of the tracking error signal, and outputs the phase-inverted tracking error signal -TE to the tracking error signal selector 106, .

In this case, since the selection signal applied to the tracking error signal selection unit 106 is a signal for selecting the non-inverted tracking error signal, the tracking error signal selection unit 106 selects the inversion And the output signal is transmitted to the tracking actuator 109 through the phase compensating unit 107 and the drive unit 108 in sequence to perform tracking servo do.

Next, when the phase difference of the E and F beams is -180, the high frequency signal read from the disk is the same as in (a) of the eighth embodiment, and the above signals are output to the coupling capacitor C2 is removed, it is a broken line as shown in (b) of FIG. 8, and is again compared with the reference signal in the comparator 103a to become a signal as shown in (C) of FIG.

When such a signal is integrated by the integrator in the integrator 104, the signal is converted to a low signal as shown in (D) of FIG. 8 and is input to the microcomputer 105.

That is, when the phase difference of the E and F beams is -180, the signal input to the microcomputer 105 becomes a low signal (0 V). In this case, the microcomputer 105 outputs a selection signal for selecting the inverted tracking error signal And applies it to the error signal selection unit 106.

On the other hand, the current corresponding to the E and F beams reflected from the disk is converted into a voltage in the subtraction unit 101 and subtracted to generate a tracking error signal TE, Are input to the tracking error signal selection unit 106 and the tracking error signal phase inverting unit 102, respectively.

Accordingly, the tracking error signal phase inverting unit 102 amplifies the tracking error signal by non-inverting and inverting the phase of the tracking error signal, and outputs the phase-inverted tracking error signal -TE to the tracking error signal selector 106, .

In this case, since the selection signal applied to the tracking error signal selection unit 106 is a signal for selecting the inverted tracking error signal, the tracking error signal selection unit 106 selects the tracking error signal, And the output signal is transmitted to the tracking actuator 109 through the phase compensating unit 107 and the drive unit 108 in sequence as described above so that tracking servo is performed .

As described above, according to the present invention, the tracking servo is performed by selecting the tracking error signal or the inverted tracking error signal according to the phase difference (180 or -180.) Of E and F, so that accurate tracking servo can be always performed.

In addition, since one tracking error device can perform tracking servo irrespective of the phase difference, if there is no inverter to phase-invert the tracking error signal, if the phase difference is -180 °, the inconvenience of mounting the inverter separately and re-adjusting the GRATlNG is eliminated There is an effect that can be made.

Claims (3)

A tracking error signal generation means for generating a tracking error signal by converting the side beam current detected by the light detection means into a voltage and subtracting the converted voltage from the detected light, A tracking error signal phase inversion means for inverting the phase of the tracking error signal generated by the tracking error signal generation means, comparison means for comparing the high frequency signal read from the disk with a reference signal and outputting the resultant signal, And a microcomputer for generating a tracking error signal or a selection signal of an inverted tracking error signal according to a result of the discrimination. The microcomputer of the present invention includes: A tracking error signal selection signal output from the microcomputer, And tracking error signal selection means for selecting and outputting the tracking error signal or the inverted tracking error signal output from the error signal generation means and the tracking error signal phase inversion means, respectively. The driving circuit according to claim 1, wherein the comparing means comprises: a coupling capacitor (C2) for removing a direct current component of a high frequency signal read from the disk and outputting only a signal component; And a comparator (103a) for comparing the output signal of the optical pickup with the tracking servo signal. The microcomputer (105) according to claim 1, wherein the tracking error signal selection means selects the tracking error signal output from the tracking error signal generation means and the tracking error signal phase inversion means, respectively, And a multiplexer (106a) for selecting and outputting an inverted tracking error signal.