KR100277023B1 - Tracking Servo - Google Patents

Abstract

The present invention relates to a tracking servo device that accurately detects a head portion, reduces a direct current component difference in high frequency signals in the head portion and a recording area portion, and realizes a stable tracking servo.

The tracking servo apparatus of the present invention is capable of detecting the header portion, signal track discrimination means connected to the detection means for discriminating signal tracks of the hills and valleys, and connected to the detection means to discriminate the header portion when the header portion is not detected. A similar signal generating means for generating a similar header part discrimination signal, a counting means connected to the similar signal generating means to count the similar header part discriminating signal, and a mirror area connected to the counting means having position information of the recording area, for detecting the same; And a mirror portion detecting means and a header portion discriminating signal generating means which are commonly connected to the detecting means and similar signal generating means to generate an authentic header portion discriminating signal.

The tracking servo device of the present invention can realize stable tracking servo by detecting the exact positions of the header and mirror areas and accurately determining the tracks of the hills or valleys in the recording area in the optical recording medium comprising the header and the recording area. have.

Description

Tracking Servo

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for an optical disc, and more particularly, to a tracking servo device that accurately detects a head portion, reduces a DC component difference in high frequency signals in the head portion and a recording area portion, and realizes a stable tracking servo.

In optical recording media such as conventional Compact Disk-Pewritable (CD-RW) and Compact Disc-Recordable (CD-R), the beam of light from the objective lens is centered on the center of the signal track. To follow, the tracking servo is implemented in a so-called push-pull method.

The push-pull tracking servo uses a difference of signals detected from the signal tracks in a photo detector (PD) positioned to the left and right of the signal track travel direction.

However, such a push-pull tracking servo has a mount like Digital Versatile Disk-RAM (hereinafter referred to as “DVD-RAM”) that has a superior recording density than the compact disc-based optical recording media. The tracking servo in the optical recording medium having a structure in which the track of the track and the groove is alternately repeated every one rotation of the track causes a problem that the track of the peak and the valley whose phase is reversed must be followed.

FIG. 1 shows a tracking error signal of a DVD-RAM having a structure in which tracks of peaks and valleys are alternately repeated for each revolution of the track.

FIG. 1 (A) shows a track of hills and valleys in which the signal track of the disc is alternately repeated every one revolution of the track.

Referring to FIG. 1 (B), in a track of a goal whose current center is A point, when performing a tracking servo that causes the light beam from the objective lens OL to follow the center of the signal track, tracking of a “+” value is performed. The error signal should be a tracking servo by moving the actuator in the circumferential direction of the disk, and the tracking error signal of “-” value is performed by the tracking servo in the circumferential direction of the disk.

On the contrary, when the tracking servo is performed in the case of the track of the mountain where the current center is B, the tracking error signal of the “+” value should perform the tracking servo in the disc inner circumferential direction and the tracking error signal of the “-” value of the track error in the outer circumferential direction. By doing a tracking servo. Therefore, the tracking servo of an optical recording medium using both mountain and valley tracks as a signal track must accurately determine the current signal track according to the mountain track or the valley track and selectively reverse polarity.

Therefore, the push-pull tracking servo can maintain a stable tracking servo system only by following either one of the mountain or valley signal tracks.

2 shows a tracking error signal detected by the header portion.

The DVD-RAM disc includes a recording area portion in which user information such as audio / video is recorded, and a header portion having identification information such as an address of the recording area portion. This header portion is further divided into a mountain identification information area including identification information (header information) of a mountain track and a valley identification information area including identification information (header information) of a track of a goal.

Header information in the header portion is embossed and recorded in a pit. 2 (a) shows a signal detected in the valley identification information area having header information of the track of the goal and a tracking error signal detected in the track of the goal. Here, the signal detected in the track of the goal is a Wobbled Prepit (Wpp) signal. 2 (b) shows a signal detected in the mountain identification information area having the header information of the mountain track and a tracking error signal detected in the mountain track.

3 shows a block diagram for detecting a conventional header portion.

Referring to FIG. 3, a conventional header detector detects a high pass filter (HPF) 2 to which a tracking error signal 1 is supplied, and a comparator 3 connected in series to an output terminal of the high pass filter (HPF) 2. And a one short trigger 4 connected in series to the output terminal of the comparator 3.

The tracking error signal 1 detected in the track of the mountain or valley is high band filtered by the high pass filter 2, which is compared with a predetermined reference level in the comparator 2 and digitalized. The signal from the comparator 3 is a discontinuous signal in which the header portion is recognized. The one-shot trigger is a function of holding the recognized header portion signal to mask the entire header portion in the one short trigger 4. Generate a header mask signal using.

At this time, the setting of the time constant value of the one-shot trigger should be prioritized. When the time constant value (τ = RC) is small, there may be a discontinuous section in the middle of the header mask signal due to the hold time of too short time. When the time constant value τ = RC is too large, a header mask signal for a longer time than the header portion is generated.

4 shows a high frequency signal RF detected in a recording area portion and a header portion in a conventional DVD-RAM.

Referring to FIG. 4, when the optical pickup proceeds from the header to the track center when the tracking servo is off, the detected high frequency signal appears distorted according to the header information signal recorded in the pit, and the recording area. When the data is not recorded, the signal is detected as a signal of a DC component, and when the data data is recorded, a high frequency signal RF according to the data is detected.

When the high frequency signal RF detected by the header unit is input to an equalizer, the signal is distorted at the header boundary due to a change in the DC level. In addition, when this signal is input to an auto gain controller (AGC), only a part of the header portion and the recording area portion signal are amplified and output at the saturation level. This results in a problem of inefficient use of the automatic gain control AGC.

Therefore, the conventional tracking servo device is difficult to detect an accurate header mask signal, and causes a problem of inefficiently amplifying the high frequency signal RF of the header portion and the recording area portion.

Accordingly, an object of the present invention is to provide a tracking servo device capable of accurately detecting a header portion and continuously estimating signal tracks of peaks and valleys in a recording area portion.

Another object of the present invention is to provide a tracking servo device that ensures detection margins for equalization, bit slice, etc. by reducing the DC level difference of the high frequency signal RF.

Another object of the present invention is to provide a tracking servo device that improves the reliability of header detection by generating a pseudo header signal when the header is not detected.

1 is a diagram showing a tracking error signal of an optical recording medium consisting of a signal track of a normal mountain and valley.

2 is a diagram showing a tracking error signal in a normal header portion.

3 is a schematic block diagram of a header detection unit in a conventional tracking servo device.

4 is a waveform diagram showing a high frequency signal detected by an optical recording medium comprising a normal header portion and a recording area portion.

5 is a detailed circuit diagram illustrating a signal detector in a tracking servo device according to an embodiment of the present invention.

6 is a detailed circuit diagram illustrating an IRF signal generator of a signal detector in a tracking servo device according to an embodiment of the present invention.

7 is a schematic block diagram of a tracking servo device according to an embodiment of the present invention.

8 is a waveform diagram showing a signal waveform of a tracking servo device according to an embodiment of the present invention.

9 is a waveform diagram showing a high frequency signal having the same DC level generated in the tracking servo device according to the embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

2: high pass filter 3: comparator

4: One short trigger 8: Tracking error signal generator

9: high pass filter 11: clamper

14: comparator 15: polarity inversion

19: correction tracking error signal generation unit 27: wobbled clock signal detection unit

32: header signal processing unit 34: mountain / valley determination unit

36: window generator

38: header presence / failure / virtual header signal generator

40: channel clock generator 42: phase comparator

44: filter 46: VCO

48: divider 50: wobble signal generator

52: EXOR gate 54: AND gate

56: standby window generating unit 58: OR gate

60: header mask / mirror generator 62: virtual header counter

R1 to R30: resistors C1 to C6: capacitors

5,6,7,10,13,15,16,17,20,21,23,25,31,33: addition amplifier

18,22,24,26,28,29,30: switcher

In order to achieve the above object, the tracking servo device of the present invention includes a detecting means for detecting a header portion, a signal track discriminating means connected to the detecting means to discriminate signal tracks of a hill and a valley, and a header portion not connected to the detecting means. Pseudo signal generating means for generating a pseudo header part discriminating signal so as to discriminate the header part when not in use, counting means connected to the pseudo signal generating means to count the pseudo header part discriminating signal, and position of the recording area connected to the counting means. And mirror area detecting means for detecting a mirror area having information, and header part discriminating signal generating means which is commonly connected to the detecting means and similar signal generating means to generate a true header part discriminating signal.

The tracking servo device of the present invention includes tracking error detecting means for detecting a tracking error signal from an optical disc on the basis of a difference in light quantity on both sides of the track, channel signal detecting means for detecting a channel signal by filtering the tracking error signal, and a channel signal. Header portion detecting means for detecting the header portion on the basis of the base, polarity inverting means for inverting the polarity of the tracking error signal as the track accessed by the light beam changes to a track of a hill or valley, and a DC offset component included in the tracking error signal. It is provided with correction tracking error generating means for removing and maintaining the previous tracking error value in the header portion.

Other objects and features of the present invention other than the above object will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 5 to 9.

5 to 7, a description will be given with reference to FIG. 9 showing signal waveforms in the tracking servo device of the present invention.

5 is a detailed circuit diagram of a signal detection unit in the tracking servo device of the present invention.

Referring to FIG. 5, in the tracking servo device of the present invention, the signal detector includes a tracking error signal generator 8 for generating a tracking error signal TE1 detected as a light quantity difference signal in a four-segmented photodiode of an optical pickup; A high pass filter 9 connected to one output end of the tracking error signal generator 8 to detect the channel signal Ch2, and a one end output terminal of the high pass filter 9 to maintain a constant pulse width in the recording area. A wobbled clock signal detector 27 for detecting the wobbled clock signal WBL_CLK, which is a square wave signal, and the other output terminal of the high pass filter 9 are connected to a high frequency signal having a different level value in the header portion in the form of a square wave. The signal of the mountain or valley is connected to the other output terminal of the header part signal detector 14 and the tracking error signal generator 8 for converting and detecting the first header part signal HD_H and the second header part signal HD_L. Tracking error depending on the track A polarity inversion unit 15 for selectively inverting the polarity of TE1 and a correction connected to an output terminal of the polarity inversion unit 15 to remove a DC offset signal included in the tracking error signal and to hold the tracking in the header unit. A correction tracking error signal generator 19 for generating the tracking error signal TE is provided.

The tracking error signal generator 8 includes a first adder amplifier 5 for detecting one side signal A + D and two second additions for detecting the other side signal B + C among signals existing on the left and right in the track travel direction. An amplifier 6 and a third adder 7 connected to the output terminals of the first adder 5 and the second adder 6 detect the tracking error signal TE.

Among the signals detected by the four-segment photodiode of the optical pickup, the D signal is supplied to the inverting terminal of the first adder amplifier 5 via the first resistor R1, and the A signal is made through the second resistor R2. It is supplied to the inverting terminal of the first adder amplifier 5 and supplied to the third resistor R3 to follow the output terminal of the first adder amplifier 5. Among the signals detected by the four-segment photodiode of the optical pickup, the C signal is supplied to the inverting terminal of the second adder amplifier 6 through the fourth resistor R4, and the B signal is made through the fifth resistor R5. In addition to being supplied to the inverting terminal of the second adder amplifier 6, it is supplied to the sixth resistor R6 to follow the output terminal of the second adder amplifier 6. The non-inverting terminals of the first and second adder amplifiers 5 and 6 are supplied with a reference voltage Vref having a predetermined level value. The signal from the first adder amplifier 5 is supplied to the non-inverting terminal of the third adder amplifier 7 via the seventh resistor R7, and the signal from the second adder amplifier 6 is connected to the eighth resistor ( The inverting terminal of the third adder amplifier 7 is supplied via R8). The voltage on the second node N2 is followed to the third node N3 via the tenth resistor R10. At this time, the reference voltage Vref via the ninth resistor R9 is supplied to the first node N1. The output signal of the third adder 7 is an addition signal of A + D- (B + C) as the tracking error signal TE1. The tracking error signal TE1 is commonly supplied to the high pass filter 9 and the polarity inverting unit 15 via the third node N3.

The high pass filter 9 includes an eleventh resistor R11 to which the reference voltage Vref is supplied, and a first capacitor C1 connected to the eleventh resistor R11 via the fourth node N4. .

Since the tracking error signal TE1 is supplied to the first capacitor C1 via the third node N3 to remove the direct current component, the signal on the fourth node N4 is a high-band filtered signal. The signal on the fourth node N4 appears as a channel signal Ch2 in the waveform as shown in FIG. 8A and is commonly supplied to the wobbled clock signal detector 27 and the comparator 14.

The wobbled clock signal detector 27 includes a fourth adder amplifier 10 to which a channel signal Ch2 is supplied to its non-inverting input terminal, and a clamper 11 connected to an output terminal of the fourth adder amplifier 10; And a bandpass filter 12 connected to one output terminal of the clamper 11, and a fifth adder amplifier R15 connected in common to the other output terminal of the clamper 11 and the output terminal of the bandpass filter 12. .

The fourth adder amplifier 10 is supplied with its channel signal Ch2 to its non-inverting terminal via the fourth node N4, and the inverting terminal is connected to the output terminal. The signal from the fourth adder amplifier 10 is supplied to the clamper 11. The clamper 11 includes a twelfth resistor R12 to which a signal from the fourth adder amplifier 10 is supplied, and first and second diodes D1 and D2 commonly connected to the twelfth resistor R12. . The first and second diodes D1 and D2 are selectively turned on at a voltage equal to or greater than a turn-on voltage to clamp the signal through the twelfth resistor R12 to a specific level. This signal is band filtered by the bad pass filter 12 and supplied to the inverting terminal of the fifth adder amplifier 13 via the thirteenth resistor R13. In addition, the signal clamped by the clamper 11 is supplied to the non-inverting terminal of the fifth adder amplifier 13 via the fourteenth resistor R14. The fifteenth resistor R15 is connected between the non-inverting terminal of the fifth adder 13 and the output terminal of the fifth adder 13. The output signal of the fifth adder 13 is a wobbled clock signal WBL_CLK as a signal shown in a waveform diagram as shown in (d) in FIG.

The channel signal Ch2 is supplied to the comparator 14 to generate the first header part signal HD_H and the second header part signal HD_L by the comparator 14.

The comparator 14 includes a sixth adder 15 and a seventh adder 16 to which the channel signal Ch2 is commonly supplied via the fifth node N5.

The sixth adder 15 is supplied with a channel signal Ch2 to its inverting terminal via the twentieth resistor R20 and a reference voltage Vref through the nineteenth resistor R19. The twenty-first resistor R21 is connected between the base voltage source GND and the non-inverting terminal of the sixth adder amplifier 15. The seventh adder 16 is supplied with a channel signal Ch2 to its own non-inverting terminal via the seventeenth resistor R17, and the common power supply Vcc is supplied via the sixteenth resistor R16. The eighteenth resistor R18 is supplied with a reference voltage Vref and connected to the inverting terminal of the seventh adder amplifier 16.

The tracking error signal TE1 generated from the tracking error signal generator 8 is supplied to the polarity inversion unit 15 to selectively invert the polarity in accordance with the tracks of the hills or valleys in the recording area.

To this end, the polarity inversion unit 15 may include the eighth and ninth adder amplifiers 33 and 17 to which the tracking error signal TE1 is commonly supplied via the sixth node N6, and the mountain / valley determination signal ( L / G) is provided and has a first switch 18 connected in common to the output terminals of the eighth and ninth adder amplifiers 33,17.

The eighth adder 33 is supplied with the tracking error signal TE1 to its non-inverting terminal, and the inverting terminal is connected to the output terminal. Therefore, it serves as a buffer for maintaining the polarity of the tracking error signal TE1 via the sixth node N6. The ninth adder 17 is supplied with its tracking error signal TE1 via its twenty-second resistor R22 to its non-inverting terminal, and the inverting terminal is connected to the output terminal via the twenty-third resistor R23. . Therefore, the polarity of the tracking error signal TE1 via the sixth node N6 is inverted.

The first switch 18 is the first and second to which the reference contact 0 connected to the correction tracking error signal generator 19 and the output signals of the eighth and ninth adder amplifiers 33 and 17 are supplied, respectively. The tracking error signal generator is provided with a selection contact (X, Y) to correct the tracking error signal TE1 whose polarity is selectively reversed according to the logic value of the mountain / gol determination signal L / G supplied as a control signal. The signal path is switched to supply to (19).

The correction tracking error signal generation unit 19 is supplied with a tracking error signal TE1 whose polarity is selectively reversed by the polarity inversion unit 15 in accordance with the track of the hill or valley, thereby removing the DC offset component from the tracking error signal. And a correction tracking error signal TE in which tracking is held in the header portion.

The correction tracking error signal generator 19 includes a tenth adder amplifier 20 having its inverting terminal connected to the reference contact point 0 of the first switch 18 and an output terminal of the tenth adder amplifier 20. An eleventh adder 21 having its own non-inverting terminal connected thereto, second and third switching units 22 and 24 commonly connected to an output terminal of the eleventh adder 21, and a second section. Connected to an output terminal of the twelfth adder 23 connected to the ventilation 22, the thirteenth adder 25 connected to the third switch 24, and the thirteenth adder 25; A fourth switch 26 is provided.

The second switch 22 holds a specific logic value (e.g., a logic value of a low) in a mirror area that contains position information of an unembossed recording area portion of a mountain or valley signal track. A reference contact (0), a first selection contact (X), and a second selection contact (Y) are provided to be selectively switched to the mirror region determination signal (Eighth (n); Mirror). The third and fourth switches 24 and 26 selectively switch to a header mask signal (HDMSK in FIG. 8 (j)) which holds a specific logic value (e.g., a logic value of Low) in the header part. The reference contact 0, the first selective contact X and the second selective contact Y may be provided.

The non-inverting terminal of the tenth adder amplifier 20 is commonly connected to the inverting terminal and the output terminal of the twelfth adder 23 via the 26th resistor R26. The reference voltage Vref is supplied to the non-inverting terminal of the tenth adder amplifier 20 via the 27th resistor R27. The twenty-fifth resistor R25 is connected between the inverting terminal and the output terminal of the tenth adder amplifier 20, and the output terminal of the tenth adder amplifier 20 is the non-inverting terminal and the fourth switch of the eleventh adder amplifier 21. It is connected in common to the 1st selective contact X of (26). The inverting terminal of the eleventh adder 21 is connected in common to its output terminal and the first selective contact X of the third switch 24 and the second selective contact Y of the second switch 22. The first selective contact X of the second switch 22 and the second selective contact Y of the third switch 24 respectively pass through the 29th resistor R29 and the 28th resistor R28. Is connected to the ground voltage source GND. The reference contact point 0 of the second switch 22 is commonly connected to the non-inverting terminal of the second capacitor C2 and the twelfth adder 23 to which the reference voltage Vref is supplied. The reference contact 0 of 24 is commonly connected to the third capacitor C3 to which the reference voltage Vref is supplied and the non-inverting terminal of the thirteenth addition amplifier 25. The second and third capacitors C2 and C3 are used to remove the direct current component. The inverting terminal and the output terminal of the thirteenth adder amplifier 25 are connected, and the output terminal thereof is connected to the second selection contact Y of the fourth switching unit 26.

When the logic value of the mirror area determination signal (figure 8 (n)) supplied to the second switch 22 is kept low, the second switch 22 receives the reference contact point 0 at the second selective contact point Y. When connected and maintaining a high logic value, the reference contact 0 is connected to the first select contact X so that the signal from the eleventh adder 21 via the seventh node N7 is received. It is sampled in the mirror area and held in the other areas. Here, the DC offset component DC offset of the tracking error signal detected in the mirror area is removed by the twelfth adder 23.

When the logic value of the header mask signal (HDMSK in FIG. 8 (j)) is kept low, the third switch 24 and the fourth switch 26 each have a second reference contact 0 as the second switch. It is connected to the selection contact (Y). When the logic value of the header mask signal HDMSK is high, each reference contact 0 is connected to the first select contact X, so that tracking is held in the header part. The correction tracking error signal TE generated from the reference contact 0 of the fourth switch 26 is supplied to the input of the tracking servo system.

In the tracking servo device of the present invention, the signal detector generates a high frequency signal RF having the same DC level center so as to facilitate level slicing. This will be described with reference to FIGS. 6 and 9.

Referring to FIG. 6, in the tracking servo device of the present invention, the IRF signal generation unit of the signal detection unit removes the high frequency signal RF, which is a light sum signal detected by the quadrant photodiode according to the logic value of the header mask signal HDMSK. First identification signal ID1 indicative of a header section having a fourth switching unit 28 for supplying the four capacitors C4 and respective different zero crossing levels, such as the waveform diagrams of the eighth (l) and (m) degrees. The fifth and sixth switches 29 and 30 to supply the channel signals Ch2 to the fifth and sixth capacitors C5 and C6, respectively, according to the logic value of the second identification signal ID2 and Fourth to sixth capacitors C4, C5 and C6 are provided with a fourteenth adder 31 in which its own non-inverting terminal is commonly connected.

The thirtieth resistor R30 is commonly connected to the non-inverting terminal of the fourteenth addition amplifier 31 and the fourth to sixth capacitors C4, C5, and C6 so that the voltage of the non-inverting terminal follows the output terminal. The fourth to sixth switchers 28, 29, and 30 have logic values of the header mask signal HDMSK and the first and second identification signals ID1 and ID2, which are control signals supplied thereto, high. It is connected at the time of holding and switched at the time of holding the logic value of the low so that a predetermined voltage is accumulated in the fourth to sixth capacitors C4, C5, and C6. This voltage is finally the same as the waveform of FIG. 9 (c) via the fourteenth adder 31 and the thirtieth resistor R30 to which the voltage of the specific level V1 is supplied to its non-inverting terminal. Generate a high frequency signal (IRF).

As another method of generating the high frequency signal IRF having the same DC level, the high frequency signal RF is connected to the fifth and sixth switches 29 and 30 instead of the channel signal CH2, and the first identification signal. Instead of ID1, an inverted signal of the header mask signal HDMSK can be used. (At this time, the second identification signal ID2, the sixth switch 30 and the sixth capacitor C6 are not used.

7 schematically shows a block diagram of the tracking servo device of the present invention.

In FIG. 7, a fifth diagram showing a signal detection unit in the tracking servo device of the present invention and an eighth diagram showing signal waveforms in the tracking servo device of the present invention will be described.

Referring to FIG. 7, the tracking servo device of the present invention includes a channel clock generator 40 generating a channel clock signal CH_CLK, a channel clock generator 40 and a comparator 14 shown in FIG. Is connected to the header signal processing unit 32 to generate a real header determination signal (Real_Header), and is connected in series with the header signal processing unit 32 to generate a hill / valley determination signal (L / G). Commonly connected to the goal determining unit 34, the header signal processing unit 32, and the wobbled clock signal detection unit 27 shown in FIG. 5, the wobbled clock signal WBL_CLK is counted, and the header signal processing unit 32 is counted. Is commonly connected to the window generator 36 for supplying a header window (HD_WINDOW) signal to the window generator 36 and the header signal processor 32, and optionally generates a virtual header decision signal (V_Header). And a header presence / absence determination / virtual header portion signal generator 38.

The channel clock generator 40 includes a voltage control oscillator (VCO) 46, a divider 48, a phase comparator 42, and a filter 44 connected to form a cyclic loop. In this way, a phase locked loop (PLL) is formed to generate a channel clock signal CH_CLK. The divider 48 divides the square wave signal generated by the VCO 46 into 186 and supplies the square wave signal divided by the 186 to the phase comparator 42. The phase comparator 42 compares the wobble signal Wobble supplied to it with the square wave signal divided by 186 and generates a voltage signal corresponding to the phase difference. The filter 44 removes a high frequency component noise signal included in this voltage signal and supplies it to the VCO 46. The VCO 46 adjusts the frequency of the square wave signal generated by itself in accordance with the input signal from the filter 44. The wobble signal WOBBLE supplied to the channel clock generator 40 is generated by the wobble signal generator 50 described later.

The header signal processing unit 32 is supplied with the first and second header part signals HD_H and HD_L, the channel clock signal CH_CLK, and the header window HD_WINDOW signal, and the first and second header part signals HD_H, The HD_L is masked by the header window (HD_WINDOW) signal and synchronized with the rising edges of the first and second header part signals HD_H and HD_L. Header_H and a second header determination signal (figure 8 (f); Header_L) are generated. The real header determination signal generated in the header signal processing unit 32 (Fig. 8 (g); Real_Header) outputs the OR of the first header determination signal Header_H and the second header determination signal Header_L. Appears as a signal.

The mountain / goal determination unit 34 receives the first header determination signal Header_H and the second header determination signal Header_L from the header signal processing unit 32, respectively, and the D / Flip flops. It is supplied to the D input and the clock signal of the to generate a mountain / valley determination signal (L / G) having a different logical value in the track of the mountain or valley. As another method of detecting the mountain / goal determination signal L / G, one of the first header determination signal Header_H and the second header determination signal Header_L may be converted into a D-Flip flop. Even if the D input is supplied and the header mask signal HDMSK is supplied as a clock signal, it is possible to have different logic values in the track of the mountain or valley.

The window generator 36 is connected to the wobbled clock signal detector 27 shown in FIG. 5 to receive the wobbled clock signal WBL_CLK, which is then counted from the count or channel clock generator 40. The channel clock signal CH_CLK is counted, and the header window signal (figure 8 (h) HD_WINDOW) is supplied to the header signal processing unit 32 at the predicted time point of the successive header portion. Then, a predetermined time is counted from the start of the header window signal HD_WINDOW, and a T1 signal having a logic value High with a constant pulse width in the middle of the header portion is transmitted to the header presence / absence determination / virtual header portion signal generator 38. Supply.

The header presence / failure determination / virtual header unit signal generator 38 receives the real header unit determination signal Real_Header, a T1 signal, and a driving voltage V_ACTIVE signal generated from a standby window generator 56 to be described later. When the (V_ACTIVE) signal is set, it is driven to determine whether the real header part determination signal Real_Header is detected from the T1 signal. At this time, if it is determined that the real header part determination signal Real_Header has not been detected, the current VH_D signal (signal continuously generated by the number of counters set to generate the virtual header part determination signal V_Header) is referred to. A virtual header part determination signal V_Header is generated.

In addition, the tracking servo device of the present invention performs an OR operation on the real header part determination signal Real_Header and the virtual header part determination signal V_Header to generate OR of the authentic header part determination signal Header. And OR via the header mask / mirror generator 60 and the header mask / mirror generator 60 and the eighth node N8 which are commonly connected to the channel clock generator 40 and the OR gate 58. Common connection to the virtual header counter 62 commonly connected to the gate 58 and the header presence / decision / virtual header unit signal generator 38, and to the header mask / mirror generator 60 and the virtual header counter 62. Generation of a wobble signal commonly connected to the standby window generator 56, the hill / valley determination unit 34, and the wobbled clock signal detection unit 27 and the header mask / mirror generation unit 60 shown in FIG. The part 50 is provided.

The OR gate 58 generates the header presence / absence / virtual header part signal from the header signal processing unit 32 via the ninth node N9 via the real header part determination signal Real_Header and the eighth node N8. The virtual header section determination signal V_Header is supplied from the section 38, and the result is logical-conjugated to generate an authentic header section determination signal Header.

The header mask / mirror generator 60 receives the authenticity header determination signal (Header) and the channel clock signal (CH_CLK), from the start of the authenticity header determination signal (Header) of the channel clock signal (CH_CLK) After counting a certain number (the length of the authenticity header determination signal Header), the header mask signal HDMSK, the second header mask signal (Fig. 8 (k); HDMSK2), the first identification signal ID1 and the first A second identification signal ID2 and a mirror area determination signal (eighth (n); Mirror) are generated. The first identification signal ID1 and the second identification signal ID2 are switching signals of the high frequency signal RF as control signals of the fifth and sixth switching units 29 and 30, as shown in FIG. Accordingly, the first identification signal ID1 and the second identification signal ID2 should be envelope signals of the first header part signal HD_H and the second header part signal HD_L, respectively. The signal L / G is input to the select terminal of the multiplexer and is generated using a signal before or after a predetermined time of the header mask signal HDMSK.

The virtual header counter 62 counts the virtual header determination signal V_Header in synchronization with the mirror area determination signal Mirror, and then decrements the VH_D signal if the count value is not "0", and decreases it to "0". In this case, the standby count generator 56 is reset until the clear count signal CLR_GER is reset and the value of the VH_D signal is loaded into the counter to indicate the next authentic header determination signal Header. Drive it. If the original value of the VH_D signal is "0", the clear count signal CLR_GER is always set. When the driving voltage signal V_ACTIVE generated by the virtual header counter 62 is reset, the header presence / failure / virtual header part signal generator 38 refers to the VH_D signal to determine the virtual header determination signal V_Header. Will occur.

The wobble signal generator 50 is provided with an EXOR gate 50 to which a mountain / goal determination signal L / G and a wobbled clock signal WBL_CLK are supplied, and a header mask signal HDMSK to which an exclusive OR gate 50 is supplied. And an AND gate 54 connected thereto.

The mountain / goal determination signal L / G and the wobbled clock signal WBL_CLK are subjected to an exclusive OR operation on the EXOR gate 50 and supplied to one input terminal of the AND gate 54. The AND gate 54 generates a wobble signal by performing a logical AND operation on the header mask signal HDMSK and the signal from the EXOR gate 50.

As described above, the tracking servo device of the present invention is stable in an optical recording medium consisting of a header portion and a recording area portion, by detecting the exact positions of the header portion and the mirror region, and accurately determining the tracks of the hills or valleys in the recording region portion. Tracking servo can be implemented.

The tracking servo device of the present invention can secure the detection margin by equalizing, bit slice, etc. by reducing the DC level difference of the high frequency signal RF.

The tracking servo device of the present invention can improve the reliability of header detection by generating a pseudo header signal when the header portion is not detected.

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

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

Claims (5)

An optical recording medium comprising a recording area comprising a signal track of hills and valleys, in which user data is recorded, and a header portion containing identification information of the recording area, comprising: detection means for detecting the header portion, and connected to the detection means; Signal track discriminating means for discriminating signal tracks of hills and valleys, pseudo signal generating means connected to said detecting means for generating a similar header portion discriminating signal so as to discriminate a header portion when said header portion is not detected, and said similar signal Counting means connected to a generating means for counting the pseudo header part discriminating signal, mirror area detecting means for detecting a mirror area having position information of the recording area connected to said counting means, said detecting means and said similar signal Number of header part discrimination signal generation common connected to the generating means to generate the authenticity header part discrimination signal A tracking servo device comprising a stage. The tracking servo device according to claim 1, wherein said counting means counts said pseudo header part discrimination signal with reference to a reference variable which is selectively varied. The method according to claim 1 or 2, wherein the counting means counts the pseudo header portion discrimination signal in synchronization with a mirror region determination signal holding a specific logical value in the mirror region, and optionally according to the count value. A tracking servo device, characterized by varying a reference set value. 3. The tracking servo according to claim 2, wherein the authenticity header part discrimination signal is detected by performing an OR operation on the header part discrimination signal detected by the detecting means and the pseudo header part discriminating signal detected by the similar signal generating means. Device. A drive of an optical disc having tracks of peaks and valleys formed therein and having a header portion containing identification information of the tracks and a recording area portion in which information is recorded, the tracking error signal from the optical disc based on the difference in light quantity on both sides of the track. Tracking error detecting means for detecting a signal, channel signal detecting means for detecting a channel signal by filtering the tracking error signal, header detecting means for detecting the header portion based on the channel signal, and a track accessed by an optical beam. Polarity inversion means for inverting the polarity of the tracking error signal as the mountain or valley track changes, and for removing the DC offset component included in the tracking error signal and maintaining the previous tracking error value in the header portion. A tracking servo device comprising a correction tracking error generating means.

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