KR100662285B1 - Method for servo controlling of optical record/player - Google Patents

Abstract

The present invention relates to a servo method of an optical recorder that performs tracking servo using a tracking error signal detected by a push-pull method, and more particularly, an MPP_TE signal and an auxiliary photodetector generated from an electrical signal output from a center photodetector of an optical detector. The gain value (k) of the SPP_TE signal is varied by comparing the magnitude and phase difference with the SPP_TE signal generated from the electrical signal output from the DPP_TE signal (= MPP_TE-kSPP_TE) by applying the variable gain value (k). By generating, it is possible to generate a tracking error signal well even when the track pitch is changed. In addition, when the track pitch changes a lot, or when the track pitch changes severely as the track crosses in and out, the tracking error signal is detected by the MPP method. Otherwise, the tracking error signal is detected by the DPP method. By doing so, the stability of the servo can be maintained even if the track pitch changes severely.

MPP_TE, SPP_TE, DPP_TE, Gain Variable

Description

Servo control method of optical record player {Method for servo controlling of optical record / player}

1 is a block diagram of a general optical recording and reproducing apparatus for performing servo of an optical recording medium.

FIG. 2 is a diagram showing the arrangement of a general photodetector composed of a center photodetector and an auxiliary photodetector.

3A is a general diagram illustrating an example in which the track cross direction of the main beam and the auxiliary beam in the free running state is an outer circumferential direction;

3B is a general view illustrating an example in which the track cross direction of the main beam and the auxiliary beam is in the inner circumferential direction in the free running state;

3C is a general diagram showing an example of a pair of tracking auxiliary beam spots arranged before and after the information decoding main beam spot.

4A to 4C conceptually show a result of detection of a main beam and an auxiliary beam on a photo detector when a track pitch of a disc is changed for an optical pickup for detecting DPP_TE signals.

(a) indicates that when the track pitch is normal,

(b) shows that when the track pitch is narrower than normal,                 

(c) is a diagram in which the track pitch is wider than in the normal case

5 is a block diagram of an optical record player for servo control according to the present invention;

6A to 6F are signal waveform diagrams generated in each part of FIG. 5 when the track pitch is normal.

7A to 7F are signal waveform diagrams generated in each part of FIG. 5 when the track pitch becomes narrower than the normal state.

8A to 8F are signal waveform diagrams generated in each part of FIG. 5 when the track pitch becomes wider than the normal state.

Explanation of symbols for main parts of the drawings

401: MPP_TE signal generator 402: LPF

403: MTZC signal generator 404: SPP_TE signal generator

405: LPF 406: STZC signal generator

407: control signal generation unit 408: switching unit

409: gain control unit 410: DPP_TE signal generator

411: signal shaping unit 412: servo control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium system, and more particularly, to a servo control method of an optical recording player that performs tracking servo by a push-pull method.                         

BACKGROUND With the development of audio and video media, optical recording medium recording and reproducing apparatuses for recording and reproducing video and audio data on semi-permanent optical recording media have been developed.

The optical recording medium, that is, the optical disk used for the functions such as reproduction and recording in the optical recording medium recording and reproducing apparatus, is a read-only ROM type and a once-writable worm according to its function and use. Types and rewritable types that can be recorded repeatedly are divided into three types.

The ROM type optical disc includes a compact disc read only memory (CD-ROM) and a digital versatile disc read only memory (DVD-ROM), and a warm optical recording medium may be written once. Recordable Compact Discs (CD-Rs) and Recordable Digital Versatile Discs (DVD-Rs).

In addition, freely repeatable rewritable optical discs include a rewritable compact disc (CD-RW) and a rewritable digital versatile disc (DVD-RW, DVD-RAM, DVD + RW). have.

Fig. 1 is a general block diagram of an optical disk recording and reproducing apparatus for recording data on such optical disks and reproducing the recorded data, wherein the optical pickup 102 condenses on the objective lens under the control of the servo control unit 104. The light beam is placed on the signal track of the optical disk 101, and the light reflected from the signal recording surface is focused again by the objective lens and then incident on the light detector for detection of the focus error signal and the tracking error signal.                         

The photo detector includes a plurality of photo detectors, and an electrical signal proportional to the amount of light obtained from each photo detector is output to the RF and servo error generator 103.

The RF and servo error generation unit 103 is an RF signal for reproducing data, a focus error (FE) signal for servo control, a tracking error (TE) signal from an electrical signal output from each photodetector of the photodetector. And the like.

The detected RF signal is output to a data decoder (not shown) for reproduction, and servo error signals such as FE and TE are output to the servo controller 104.

The servo controller 104 processes the focus error (FE) signal to output a driving signal for focusing control to the focus servo driver 105, and processes the tracking error (TE) signal to process the driving signal for tracking control. Is output to the tracking servo driver 106.

At this time, the focus servo driver 105 moves the optical pickup 102 up and down by driving the focus actuator in the optical pickup 102 so that the optical disk 101 follows the vertical movement along with the rotation.

The tracking servo driver 106 moves the objective lens of the optical pickup 102 in the radial direction by driving the tracking actuator in the optical pickup 102 to correct the position of the beam and track a predetermined track. .

In addition, when the entire optical pickup needs to be moved, the sled servo driver 107 receives the sled control signal of the servo controller 104 and drives the sled motor 108 to drive the optical pickup main body. In direct direction.

In this case, the tracking control used for the CD and DVD-based optical discs in the RF and servo error generation unit 103 and the servo control unit 104 is generally a 3-beam method, a push-pull (PP) method, and a phase difference. There are various methods such as differential phase detection (DPD).

Here, in the three-beam method, assuming that a photo detector is configured as shown in Fig. 2, a pair of tracking side beam spots are formed before and after the main beam spot for information decoding as shown in Figs. 3A to 3C. I am placing it. That is, the auxiliary beams are arranged in opposite directions from the track center by one quarter of the track interval as shown in FIG. 3C.

At this time, arranging the auxiliary beams as described above is for preventing the omission of detection signals and for avoiding crosstalk from adjacent tracks. 3A illustrates an example in which the track cross direction of the main beam and the auxiliary beam is in the outer circumferential direction in the free running state, and FIG. 3B illustrates an example in the track cross direction of the main beam and the auxiliary beam in the free running state in the inner circumferential direction. Figure is shown.

In this case, the photodetector is generally composed of a center photodetector for detecting the amount of light of the main beam and an auxiliary photodetector for detecting the amount of light of the auxiliary beam. For example, as shown in FIG. It consists of four photodetectors (PDA, PDB, PDC, PDD), each of which is divided in a radial direction, i.e., divided into four, and the auxiliary photodetector includes two photodetectors each positioned at the top and bottom of the center photodetector. PDE, PDF). Here, the tracking error signal is obtained by processing (e-f) the electrical signals e, f output from the auxiliary light detecting elements PDE and PDF.

In addition, the push-pull method divides the photodetecting element of the photodetector into two in accordance with the track direction and then detects the tracking error signal from the light quantity balance of both photodetecting elements. This utilizes the fact that the intensity distribution of light diffracted and reflected by the pit and then incident on the objective lens changes with the relative positional change between the pit and the spot.

If the shadow of the pit is equally detected by both photodetectors, the tracking error signal TE becomes zero, which is called tracking on (or on track). Conversely, a state in which the light error is shifted left and right from the track center and the tracking error signal TE has a + or-value is called tracking off (or off track).

If the optical detector comprises four optical detection elements (PDA, PDB, PDC, PDD) divided into four parts, i.e., divided into four directions in the signal track direction and the radial direction of the optical disc, the tracking error signal by the PP method is The electrical signals a, b, c, and c output from the photodetecting element of the photodetector can be obtained by (a + c)-(b + c). At this time, if the photo detector is divided into two in the track direction, the tracking error signal (= I1-I2) is detected from the light quantity balance of both photodiodes I1 and I2. That is, a + c in FIG. 2 corresponds to I1 and b + c corresponds to I2.

If it is assumed that the photo detector is shown in FIG. 2, the main beam PP (MPP) signal MPP_TE is obtained by converting the electrical signals a, b, c and c outputted from the center photodetection element of the photo detector into (a + c). It can be obtained by-(b + c), and the SPP (Side Beam PP) signal SPP_TE can be obtained by (ef) the electric signals e and f output from the auxiliary photodetecting element of the photodetector. In addition, the DPP (Differential PP) signal DPP_TE may be obtained by MPP_TE-SPP_TE. Here, the photo detector is divided into four optical detection elements (PDA, PDB, PDC, PDD), which are divided in four directions, i.e., in the signal track direction and the radial direction of the optical disk, or the optical detection element I1 divided into two in the track direction. PP2 and MPP signal are the same concept.

For example, a conventional CD generates a tracking error signal using a 3-beam method, and a CD recorder, particularly a CD-R / RW, generates a tracking error signal (DPP_TE) by a differential push pull (DPP) method. That is, when the tracking error signal MPP-TE is detected by the MPP method by receiving the signal output from the center photodetector, the amount of the MPP signal MPP_TE is large, which causes DC offset due to lens shift.

Therefore, in the CD-R / RW, the offset of the MPP_TE is compensated by using the DPP scheme (DPP_TE = MPP_TE-SPP_TE) because of the DC offset in the MPP scheme. That is, the SPP_TE is detected in order to remove the offset caused by the lens shift, which is a disadvantage of the tracking error signal generated by the MPP_TE, the multiplied by the appropriate gain k after the detected SPP_TE is compensated for the offset of the MPP_TE to compensate for the DPP tracking error Generate the signal DPP_TE.

At this time, in generating the DPP_TE signal, the optical system is configured such that the auxiliary beam is generated at the Tp / 2 position so that the position of the auxiliary beam is located at the left and right of the signal track.

On the other hand, the track pitch is generally defined in the specification, but the track pitch may change during disc manufacture or as the disc becomes denser. In addition, the track pitch may vary depending on the depth of the pit, the characteristics of the optical pickup, the characteristics of the deck, and the like.

However, in the related art, since the gain k multiplied by the SPP_TE signal is fixed, a DPP error signal DPP_TE may not be properly generated when the track pitch is changed.

That is, (a) to (c) of FIG. 4 conceptually show a result of detecting the main beam and the auxiliary beam on the optical detector when the track pitch of the disk is changed for the optical pickup for detecting the DPP_TE signal.

FIG. 4A shows a case where the track pitch is normal, FIG. 4B shows a case where the track pitch is narrower than normal, and FIG. 4C shows a case where the track pitch is wider than the normal. .

At this time, although the beam size differs according to optical pickup in FIG.4 (a)-(c), it expresses as the same thing. 6 to 8 show examples of the MPP_TE signal and the SPP_TE signal detected in each case described above.

That is, when the track pitch is normal as shown in FIG. 4A, it can be seen that the phases of the MPP_TE signal and the SPP_TE signal are opposite in polarity and the same magnitude. On the other hand, when the track pitch is narrowed as shown in (b) of FIG. 4, it can be seen that the magnitude of the MPP_TE signal and the magnitude of the SPP_TE signal are smaller than that of the normal, and the phase does not exactly differ by 180 degrees. Similarly, when the track pitch is widened as shown in FIG. It can be seen that.

For example, as shown in FIG. 4B, when the track pitch is narrowed, the size of the main beam detected by the photodetector decreases, and the phase of the SPP_TE signal changes with respect to the MPP_TE signal. That is, when the phase difference between the MPP_TE signal and the SPP_TE signal is normal, the difference is exactly 180 degrees. When the track pitch is narrowed, the difference is 180 degrees, and the difference is 180-Φ depending on the degree. In this case, the amplitude of the SPP_TE signal is smaller than the MPP_TE signal because the phase difference is not 180 degrees in the case of I1-I2. That is, the phase difference between the two auxiliary beams becomes smaller, resulting in a smaller amplitude of the SPP_TE signal, which may adversely affect the track servo.

For example, if the track pitch is narrowed down to Tp / 8, the 45-degree phase difference occurs in the SPP_TE signal, so that the magnitude is significantly reduced.

Similarly, even when the track pitch is wide, the amplitude of the MPP_TE signal is the same as in the normal case, but as the amplitude of the SPP_TE signal decreases, the phase of the SPP_TE signal changes with respect to the MPP_TE.

Therefore, when the DPP_TE signal is generated using the SPP_TE signal whose amplitude and phase are distorted as described above, the DPP_TE signal may have an offset with respect to the amplitude and track center TC of the DPP_TE.

In other words, when the track pitch is narrowed or widened, the SPP_TE signal is made smaller and the phase is shifted from the MPP_TE signal. The SPP_TE signal is generated like a noise component. When the DPP_TE signal is generated using the generated SPP_TE signal, distortion may occur in the DPP_TE signal.

As described above, when the distortion occurs in the DPP_TE signal, the tracking servo may not be properly performed, and thus the servo may become unstable, resulting in track slippage.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to adjust the gain value (k) multiplied by SPP_TE according to the degree of change of the track pitch so that the DPP_TE signal is well generated even if the track pitch is changed. The present invention provides a servo control method for an optical recorder.

In the servo method of the optical recorder according to the present invention for achieving the above object, it detects the MPP_TE signal from the electrical signal output from the center light detection element, and the SPP_TE signal from the electrical signal output from the auxiliary light detection element Detecting a phase difference between the MPP_TE signal and the SPP_TE signal detected in the step, and varying a gain value k multiplied by the SPP_TE signal according to the detected phase difference. And multiplying a gain value by the SPP_TE signal to obtain a difference from the MPP_TE signal and outputting the difference as the final tracking error signal.

The phase difference detecting step may include generating a first track zero cross signal MTZC from the MPP_TE signal and generating a second track zero cross signal STZC from the SPP_TE signal, and combining and combining the MTZC signal and the STZC signal. Thereafter, the step of setting the time axis size of the AND-combined signal as the phase difference of the SPP_TE signal with respect to the MPP_TE signal.

The phase difference detecting step is characterized by detecting whether the track pitch is narrower or wider than the normal state by determining the state of the MTZC signal from the signal generated by the end combination.

The generating of the last tracking error signal may include detecting a periodicity of the STZC signal, selecting and outputting a zero value if the periodicity of the STZC signal is not detected, and selectively outputting the SPP_TE signal if the periodicity is detected; After multiplying the variable output by the gain signal selected in step, the difference between the MPP_TE signal is obtained and outputted as a final tracking error signal.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

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

The present invention compares the magnitude and phase difference between the MPP_TE signal generated from the electrical signal output from the center photodetector of the photodetector and the SPP_TE signal generated from the electrical signal output from the auxiliary photodetector and then varies the gain of the SPP_TE signal. By generating the DPP_TE signal, the tracking error signal is well generated even when the track pitch is changed.

FIG. 5 is a block diagram illustrating an optical recording / reproducing apparatus for servo control according to the present invention, and generates an MPP_TE signal that generates a tracking error signal MPP_TE by the MPP method by using an electrical signal output from a center photodetector of a photodetector. The unit 401, a first LPF 402 for low pass filtering the MPP_TE signal, and an MTZC signal generator 403 for detecting a peak-to-peak voltage MPP Vpp and a zero cross signal of the low pass filtered MPP_TE signal. ), An SPP_TE signal generator 404 for generating a tracking error signal SPP_TE using the electrical signal output from the auxiliary photodetector of the photodetector, and a second LPF for low pass filtering the SPP_TE signal. 405), an STZC signal generation unit 406 for detecting the peak-to-peak voltage SPP Vpp of the low pass filtered SPP_TE signal and the zero cross signal, and a peak-to-voltage MPP Vpp of the MPP_TE signal and zero chroma. Determining the magnitude and phase difference between the MPP_TE signal and the SPP_TE signal from the signal MTZC and the peak-to-peak voltage SPP Vpp of the SPP_TE signal and the zero cross signal STZC to determine the servo control method and control accordingly A control signal generator 407 which determines a gain k multiplied by the SPP_TE signal and is switched according to a control signal of the control signal generator 407 to be output by the second LPF 405. A switching unit 408 for selectively outputting an SPP_TE signal or a zero value, and a gain adjusting unit for varying a gain k of a signal output through the switching unit 408 according to a control signal of the control signal generator 407 409, a tracking error for generating a tracking error signal (eg, a DPP_TE signal) by obtaining a difference between the gain-controlled SPP_TE signal and the MPP_TE signal output from the first LPF 402 by the gain adjusting unit 409. Signal generator 410, the generated After shaping the racking error signal (DPD_TE) it consists of a signal shaping unit 411 for output to the servo control section 412. The

)이며, 도 8의 (a) 내지 (f)는 트랙 피치가 넓어진 경우(즉, MPP_TE 신호와 SPP_TE 신호의 위상차가 180도보다 많이 나는 경우 ; 180+

)에 상기 도 5의 각 부에서 검출되는 동작 파형도들이다.6A to 6F show normal track pitches (ie, a phase difference between the MPP_TE signal and the SPP_TE signal remains 180 degrees apart), and FIGS. 7A to 7F show the track pitches. Becomes narrower (i.e., the phase difference between the MPP_TE and SPP_TE signals is less than 180 degrees;

(A) to (f) in FIG. 8, when the track pitch is wide (that is, when the phase difference between the MPP_TE signal and the SPP_TE signal is greater than 180 degrees;

) Are operational waveforms detected by each part of FIG. 5.

That is, in FIGS. 6 to 8, (a) is a waveform diagram of the MPP_TE signal generated by the MPP_TE signal generator 401, and (b) is a waveform diagram of the SPP_TE signal generated by the SPP_TE signal generator 404. (C) is a track zero crossing (MTZC) signal detected from the MPP_TE signal, (d) is a track zero crossing (STZC) signal detected from the SPP_TE signal, and (e) is (c), ( This signal is the AND combination of the MTZC signal and STZC signal of d). In addition, (f) is a waveform diagram of the DPP_TE signal generated from the results of (a) to (e) described above.

The present invention configured as described above assumes that the photo detector is configured as shown in FIG. 2. Then, the MPP_TE signal generating unit 401 (a + c)-the electrical signals a, b, c, c output from the center photodetecting element of the photo detector as shown in (a) of Figs. (b + c) generates an MPP_TE signal and then low pass filters the first LPF 402 to remove glitch. The MPP_TE signal low-pass filtered by the first LPF 402 is input to the MTZC signal generator 403, and the MTZC signal generator 403 is configured with the peak-to-peak voltage (MPP Vpp) of the MPP_TE signal. The MTZC signal, which is turned on / off at the track zero cross point of the MPP_TE signal, is generated as shown in FIGS. 6 to 8 and output to the control signal generator 407. For example, when the MPP_TE signal is AC-coupled and sliced to an internal reference level, an MTZC signal is generated.

Meanwhile, the SPP_TE signal generator 403 generates the SPP_TE signal by (ef) the electric signals e and f output from the auxiliary photodetector of the photo detector as shown in (b) of FIGS. 6 to 8. Low pass filtering in the second LPF 405 to remove glitch. The low pass filtered SPP_TE signal from the second LPF 405 is input to the STZC signal generator 406, and the STZC signal generator 406 is coupled with the peak-to-peak voltage SPP Vpp of the SPP_TE signal. The STZC signal, which is turned on / off at the track zero cross point of the SPP_TE signal, is detected and output to the control signal generator 407 as shown in FIGS. For example, when the SPP_TE signal is AC-coupled and sliced to an internal reference level, an STZC signal is generated.

The control signal generator 407 detects the magnitude and phase difference between the MPP_TE signal and the SPP_TE signal to determine a k value multiplied by the SPP_TE signal. In addition, the control signal generator 407 determines the servo method.

In an embodiment, the control signal generator 407 performs an AND combination of the MPP_TE signal and the SPP_TE signal as shown in FIGS. 6 to 8E, and detects a phase difference between the MPP_TE signal and the SPP_TE signal from the result. .

In the present invention, there is no phase difference when the phase difference between the MPP_TE signal and the SPP_TE signal is exactly 180 degrees for the convenience of description, that is, the phase between the MPP_TE signal and the SPP_TE signal is greater than or less than 180 degrees. Defines the case that the phase difference has occurred.

In other words, when the track pitch is normal as shown in FIG. 6, the signal that is AND-combined as shown in FIG. 6E is not generated. This is because the phase of the SPP_TE signal is neither fast nor slow and is exactly 180 degrees different from the MPP_TE signal, so that there is no phase difference. However, when the track pitch is narrowed as shown in FIG. 7 or when the track pitch is widened as shown in FIG. 8, the phase of the SPP_TE signal is greater than or less than 180 degrees with respect to the MPP_TE signal, that is, the phase is slower than 180 degrees. Or fast In this case, it is defined that a phase difference has occurred.

Therefore, in the present invention, the phase difference detected for adjusting the gain value k of SPP_TE can be known from the AND combination result. That is, when φ is detected as shown in Figs. 7 and 8 (e), the signal magnitude on the time axis of φ is a phase difference defined in the present invention.

Here, if the current track pitch is narrowed or widened, it can be known whether the SPP_TE signal is as slow as φ degrees or as fast as φ degrees with respect to the MPP-TE signal.

Therefore, it is possible to determine whether the track pitch is wider or narrower than the normal state by looking at the state of the MTZC signal from the signal generated by the AND combination.

For example, as shown in FIG. 7, when the high period of the MTZC signal is detected at the rising edge of the AND-combined signal, the phase of the SPP_TE signal is 180-φ degrees slower with respect to the current MPP_TE, that is, the track pitch is narrower than the normal state. You can judge that you lost. On the contrary, when the low period of the MTZC signal is detected at the rising edge of the AND-combined signal as shown in FIG. have.                     

The control signal generator 407 determines the k value to be proportional to the detected phase difference. That is, as the phase difference increases, the magnitude of the SPP_TE signal decreases as shown in FIGS. 7 and 8 (b). In this case, the control signal is generated in the direction of increasing the k value and output to the gain adjusting unit 409.

On the other hand, the control signal generator 407 also determines the servo control method. That is, the tracking error signal is generated by the DPP method to perform the tracking servo or by the MPP method to determine whether to perform the tracking servo.

For example, when multiple STZC signals are detected in one cycle of MTZC, there is no periodicity in the STZC signal. In this case, the track pitch changes a lot, or the track pitch changes severely while the optical pickup tracks the outer periphery. In this case, the SPP_TE signal is not detected properly because the track pitch is severely changed. Therefore, in this case, since severe distortion may occur in the DPP_TE signal, it is better to perform the tracking servo with the tracking error signal detected by the MPP method rather than the DPP method. If the servo is performed with the tracking error signal detected by the MPP method, the sled may follow the track sensitively.

For example, the control signal generator 407 checks how many STZC signals are detected in one MTZC cycle and outputs a control signal to the switching unit 408 at the next stage. If not many are detected, a control signal is generated to select the SPP_TE signal output from the second LPF 405.

The switching unit 408 selects a zero value or the SPP_TE signal output from the second LPF 405 according to the control signal of the control signal generator 407 and outputs the signal to the gain adjusting unit 409. The gain controller 409 varies the gain value k according to the gain control signal output from the control signal generator 407 and multiplies the signal output through the switching unit 408.

If a zero value is output from the switching unit 408, a zero value is output to the DPP_TE signal generation unit 410 regardless of the gain value k, and if the SPP_TE signal is output from the switching unit 408, the zero value is output. The variable gain value k is multiplied by the SPP_TE signal and output to the DPP_TE signal generator 410.

The DPP_TE signal generator 410 subtracts the signal output from the gain adjuster 409 to the MPP_TE signal output from the first LPF 402 and outputs the signal to the signal shaping unit 411.

At this time, when the zero value is output from the gain adjuster 409, the tracking error signal output from the DPP_TE signal generator 410 becomes an MPP_TE signal. On the other hand, if the kSPP_TE signal is output from the gain adjuster 409, the tracking error signal output from the DPP_TE signal generator 410 becomes DPP_TE (= MPP_TE-kSPP_TE).

The signal shaping unit 411 performs waveform shaping for adjusting the offset, bias, and gain of the tracking error signal output from the DPP_TE signal generating unit 410, and then outputs the waveform to the servo controller 412.

As described above, according to the servo control method of the optical recorder according to the present invention, the MPP_TE signal generated from the electrical signal output from the center photodetector of the photodetector and the SPP_TE generated from the electrical signal output from the auxiliary photodetector By comparing the magnitude and phase difference with the signal, the gain of the SPP_TE signal is varied and the variable gain value is applied to generate the DPP_TE signal (= MPP_TE-kSPP_TE), so that a tracking error signal is well generated even when the track pitch is changed. . As a result, since the servo is stable, track slipping and the like can occur.

In addition, when the track pitch changes a lot or the track pitch changes severely while crossing the track in and out, the tracking error signal is detected by the MPP method. Otherwise, the tracking error signal is detected by the DPP method. By doing so, the stability of the servo can be maintained even if the track pitch changes severely.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (6)

A tracking error signal is generated by generating a tracking error signal from a center photodetector for detecting reflected light of a main beam for information decoding and an electrical signal output from a photodetector in which a pair of auxiliary photodetectors are disposed before and after the center photodetector. In the servo control method of the optical recorder, Detecting a main push-pull tracking error signal (MPP_TE) from the electrical signal output from the center light detection element, and detecting an auxiliary push-pull tracking error signal (SPP_TE) from the electric signal output from the auxiliary light detection element; Detecting a phase difference between the MPP_TE signal and the SPP_TE signal detected in the step, and varying a gain value k multiplied by the SPP_TE signal according to the magnitude of the detected phase difference; And And multiplying the SPP_TE signal by the gain value varied in the above step, obtaining a difference from the MPP_TE signal, and outputting the difference as the final tracking error signal. The method of claim 1, wherein the phase difference detecting step Generating a first track zero cross signal (MTZC) from the MPP_TE signal and a second track zero cross signal (STZC) from the SPP_TE signal; And after combining the MTZC signal and the STZC signal, setting the time axis size of the AND-combined signal to the phase difference of the SPP_TE signal with respect to the MPP_TE signal. The method of claim 2, wherein the phase difference detection step And determining whether or not the track pitch is narrower or wider than the normal state by determining the state of the MTZC signal from the signal generated by the end combination. The method of claim 3, wherein the phase difference detecting step A servo of the optical recording / reproducing apparatus characterized by detecting whether the track pitch is narrower or wider than the normal state by checking whether the MTZC signal is high or low at the start time of the signal generated by the end combination. Control method. 3. The method of claim 2, wherein generating the final tracking error signal Detecting a periodicity of the STZC signal; Selecting and outputting a zero value if the periodicity of the STZC signal is not detected and selectively outputting the SPP_TE signal if a periodicity is detected; And multiplying a variable gain by a signal selected and output in the step, and obtaining a difference from the MPP_TE signal to output a final tracking error signal. The method of claim 5, wherein the periodicity detection step And counting and detecting the number of STZC signals generated during one cycle of the MTZC signal.

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