JP2004158180A - Disk playback device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reliability of the operation of a disk playback device by accurately counting the number of cross tracks even if optical disks have different recording density. <P>SOLUTION: A pickup means is driven so that a light spot crosses a track of an optical disk while the pickup means reading a high frequency signal of the disk. A first detecting means obtains first detection output being a peak side and having a charge-discharge time constant for a peak side of the high frequency obtained from the pickup means. A second detecting means obtains second detection output being a bottom side and having a charge-discharge time constant ( the larger charge-discharge time constant than the charge-discharge time constant for the peak side) for the bottom side of the high frequency signal. A subtraction means obtains a ripple waveform in accordance with a crossed track by subtracting the second detection output from the first detection output. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a disc reproducing apparatus, and in particular, even in a situation where a plurality of kinds of optical discs having different recording densities are available recently, a disc capable of obtaining an optimum special reproduction control or the like for these discs. It relates to a playback device.

  Conventionally, compact disks (CD) and laser disks (LD) dedicated to music have been developed as optical disks. A disc reproducing apparatus for reproducing these discs is provided with a repeat function for repeatedly reproducing a music at a specified address, or a heading function for jumping to a music at a specified address and starting reproduction.

  To realize such a function, the number of tracks crossing from the designated address and the current address is calculated, and the pickup device is moved in the radial direction of the disk by the calculated number of tracks. Then, the head is checked after confirming whether or not the address information of the track at the moved position is the designated address.

  In order to realize the above cueing function, it is necessary to have a function for counting the number of tracks crossed while the pickup device is moving in the radial direction of the disk. The principle for obtaining the track number count will be described below.

  As shown in FIG. 7A, when the reflected light is read while moving the optical pickup device at a predetermined speed in the radial direction of the disk, the level difference of the read high-frequency signal between the track information section and the track is obtained. Occurs. When this high-frequency component is subjected to waveform detection, a relatively good sine curve is obtained as shown in FIG.

  That is, when the light spot is on the track during the traverse, the amplitude of the high-frequency component is high, and when it is between the tracks, the amplitude of the high-frequency component is low. Ideally, when the light spot is between the tracks, the amplitude should disappear. However, since the outer circumference of the light spot covers the adjacent tracks on both sides, crosstalk between the tracks occurs, and as shown in FIG. Such an amplitude occurs. Crosstalk is determined by the recording density (track interval) of an optical disk and the size of a light spot.

  Therefore, if one cycle of the signal waveform in FIG. 7B is counted as one track, the number of tracks crossed can be known. Hereinafter, a means for obtaining such information on the number of tracks will be referred to as a cross track counting means.

  By the way, recently, moving picture video data, audio data, and sub-picture data (for example, subtitle data) are compressed and recorded at high density on a compact compact disc (a disc having the same radius as the CD). Regarding subtitles, a system has been developed in which a plurality of types of subtitles in different languages are recorded, and at the time of reproduction, audio of a desired language and subtitles of a desired language can be freely selected and reproduced. This type of optical disk is tentatively referred to as a DVD (digital versatile disk). For DVDs, DVD-ROMs and DVD-RAMs are being developed.

  Here, comparing the capacity of the CD and the DVD, the capacity of the CD is 650 Mbits and the capacity of the DVD is about 7 times 4.7 Gbits, and the recording density is remarkably large. Therefore, when reproducing a DVD, a 650 nm beam, for example, is used as a laser beam for irradiating a track, instead of the 780 nm wavelength used in the conventional CD reproduction. In this case, an optical system having a high numerical aperture (high NA) is used to optically focus the laser beam. Further, in the case of a CD, the thickness of a disk substrate is specified as 1.2 mm. However, in the case of a DVD, when the thickness is set to 1.2 mm due to a thin beam, the disk is susceptible to tilt (substrate inclination). The half 0.6 mm disk substrate (substrate) is used. Furthermore, while a CD has a track pitch of 1.6 μm and a minimum pit width of 0.9 μm, a DVD has a track pitch of 0.74 μm and a minimum pit width of 0.4 μm, and DVDs have a smaller track pitch than CDs. It is fine and cannot use the same control form as the tracking servo.

  The above-described DVD naturally requires the heading function as described above. However, a problem arises when the same cross track counting means as in the related art is used to realize this heading. This is because in the DVD, the distance between tracks is narrow due to the high recording density, resulting in a high-frequency signal as shown in FIG. 8A, and a pulse component having a high peak value also occurs between tracks. . Even if such a high-frequency signal is envelope-detected, a good sine curve cannot be obtained as shown in FIG. 8B, so that it cannot be used for cross-track counting. Even if this waveform is used for cross-track counting, errors increase and cause malfunction.

  Therefore, an object of the present invention is to provide a disk reproducing apparatus capable of accurately counting the number of cross tracks and improving the reliability of operation even for optical disks having different recording densities.

  In order to achieve the above object, the present invention provides a pickup means for optically reading a high-frequency signal recorded on an information track of an optical disc, and a light source for the pickup means while reading the high-frequency signal. A driving means for driving the pickup means so that the spot crosses the track of the optical disc; and a charge / discharge time constant for the peak side of the high-frequency signal obtained from the pickup means, the first being the peak side. A first detection means for obtaining a detection output; and a charge / discharge time constant for the bottom side of the high-frequency signal obtained from the pickup means (however, a charge / discharge time constant larger than the charge / discharge time constant for the peak side). A second detection means for obtaining a second detection output on the bottom side, and the second detection means for obtaining the second detection output from the first detection output. And a subtraction means for obtaining a ripple waveform corresponding to tracks traversed by subtracting the detection output (track cross signal).

  According to the present invention, even if the optical discs have different recording densities, the number of cross tracks can be accurately counted, and the operation reliability can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an embodiment showing one feature of the present invention. Reference numeral 11 denotes an optical disk (such as a CD or DVD), which is driven to rotate by a disk motor 12. Reference numeral 21 denotes an optical pickup device, which is controlled to move in the radial direction of the disk by a pickup motor (not shown). The high-frequency modulated signal output from the optical pickup device 21 is input to the preamplifier 22 and amplified to a predetermined level.

  The high-frequency signal output from the preamplifier 22 is input to the tracking error detection unit 100 and the track cross detection unit 101. The track cross detection unit 101 includes a peak detection circuit 102 that detects a peak side of a high-frequency signal, and a bottom detection circuit 103 that detects a bottom side of the high-frequency signal. Further, the track cross detecting section 101 has a subtractor 104 for subtracting the output of the bottom detection circuit from the output of the detected peak detection circuit.

  The output of the subtractor 104 is input to the traverse control unit 105. The tracking error signal detected by the tracking error detection unit 100 is also input to the traverse control unit 105.

  Now, when a traverse command signal is input from the traverse command unit 106, the traverse control unit 105 controls a pickup motor (not shown) of the optical pickup device 21 to move the optical pickup device 21 in the radial direction of the disc. Move control to. At this time, the sine waveform from the track cross detection unit 101 is monitored in order to know how many tracks have been crossed. The number of track crosses is grasped by detecting how many periods the sine waveform has occurred.

  Here, the tracking error signal is used together for the following reason. If the tracking error signal is monitored after the movement of the optical pickup device 21 is started, the number of tracks crossed can be known by counting the number of repetitions of increase and decrease of the error signal. However, in practice, the disk may move relatively in the opposite direction to the original moving direction due to the eccentricity of the disk. In order to eliminate this problem, a track cross detection unit 101 is provided to obtain a track cross signal. This is because the movement direction of the optical pickup device can be detected by monitoring the phase difference between the track cross signal and the tracking error signal.

  That is, when the optical pickup device 21 is controlled to move outward from the center of the disk, the change pattern of the tracking error signal should take a similar pattern every time it crosses each track. A tracking error signal having a predetermined phase relationship with respect to a change in the track cross signal. However, if the optical pickup device 21 moves relatively in the direction opposite to the original moving direction due to the eccentricity of the disk, the phase change pattern of the tracking error signal with respect to the track cross signal changes, so that the track Can be recognized in the opposite direction. Therefore, in such a case, the counting of the number of tracks can be adjusted.

  Here, the present invention is characterized by means for obtaining a track cross signal in the track cross detecting section 101. That is, as described above, the track cross signal has a different high-frequency envelope waveform between disks having different recording densities. In particular, in the case of crossing tracks of a high-density disk, a pulse output is also generated between tracks, so that ordinary envelope detection results in a distorted waveform.

(A) Therefore, the present invention employs the following method as a first measure.

  That is, in the peak detection circuit 102, the charging time constant is reduced (T2) and the discharging time constant is increased (T1). On the other hand, in the bottom detection circuit 103, the charging time constant is increased (T2) and the discharging time constant is decreased (T1).

  FIG. 2 shows the principle of the high-frequency signal and the detection outputs 102a and 103a when the charge and discharge time constants of the detection circuits 102 and 103 are set as described above. In the detection output 102a, charging is performed promptly at the positive polarity level of the high-frequency signal (small time constant), and discharging is performed slowly at the negative polarity level (large time constant). Therefore, as shown in FIG. 2, an attempt is made to follow a change in the peak level on the positive polarity side. Conversely, in the detection output 103a, charging is performed gently (large time constant) at the positive polarity level of the high-frequency signal, and discharge is performed rapidly (small time constant) at the negative polarity level. Therefore, an attempt is made to follow a change in the peak level of the high frequency signal on the negative polarity side. However, even if there is a single pulse with a large noisy property during a period in which the pulse is coarse, the response is slow because the frequency is low, and the change in the peak level follows only in a portion where the pulse is dense.

  This makes it possible to obtain a track cross signal in which the discrimination between the tracks and the track information is clarified.

  The relationship between the time constants T1 and T2 is preferably 1 to 5 to 20. A more favorable result could be obtained if the relationship between the time constants T1 and T2 was 1:10.

  FIG. 4 shows a high-frequency waveform and a track cross signal when traversing.

  (B) In the present invention, the charge / discharge time constant (attack / release) of the peak detection circuit 102 is set small, and the charge / discharge time constant (attack / release) of the bottom detection circuit 103 is set large. This means that the sensitivity of the peak detection circuit 102 is high and the sensitivity of the bottom detection circuit 103 is low.

  FIG. 3 shows waveforms of the output of the peak detection circuit 102 and the output of the bottom detection circuit 103 obtained by setting such a time constant. At this time, the ratio of the time constant was within the range of (1/20) to (1/5) at the peak / bottom, and a good track cross signal was obtained without any problem. In addition, when the charge / discharge time constant of the bottom detection circuit 103 was "10" with respect to the charge / discharge time constant of the peak detection circuit 102 of "1", a good track cross signal could be obtained.

  As described above, according to the present invention, by lowering the sensitivity of the bottom detection circuit 103, the output waveform is not distorted by the pulse noise of crosstalk between adjacent tracks, and a good track cross signal can be obtained. Can be. Therefore, it is possible to obtain operational reliability such as track jump and heading reproduction during special reproduction.

  FIG. 5 shows the overall configuration of a disk reproducing apparatus using the present invention. An optical disk (CD or DVD or the like) 11 is driven to rotate by a disk motor 12. The movement of the optical pickup device 21 in the radial direction of the disk is controlled by a pickup motor (not shown). The high-frequency modulated signal output from the optical pickup device 21 is input to an equalizer 23 via a preamplifier 22 and equalized in waveform. The modulated signal whose waveform has been equalized is input to the data slicer 24 and binarized. The binarized signal is supplied to the data extraction unit 25. The data extraction unit 25 includes a data synchronous clock generator using a phase locked loop circuit (PLL circuit). Therefore, in the data extraction unit 25, a data clock is generated, and the modulation signal is sampled using the data clock. As a result, digital data recorded on the optical disk is extracted from the data extracting unit 25, and the digital data is input to the synchronization detecting / demodulating unit 26. The synchronization detection / demodulation unit 26 separates the synchronization signal and demodulates the modulation signal to the original bit code.

  The demodulated data is input to the error correction unit 27. The error-corrected demodulated data is input to the data processing unit 28, where processing such as data separation and analysis is performed. Note that demodulation processing may be performed after synchronization separation and error correction have been performed.

  The synchronization signal obtained by the synchronization detection is input to the disk servo circuit 31. The disk servo circuit 31 fetches a synchronization signal synchronized with the data clock, and controls the rotation of the disk motor 12 based on the frequency and phase of the synchronization signal. Then, during normal reproduction, the disk servo circuit 31 controls the rotation of the disk motor 12 so that a predetermined frequency and phase of the synchronization signal in the synchronization detection / demodulation unit 26 are obtained.

  The output of the preamplifier 22 is input to the track cross detection unit 101, and the detection output of the track cross detection unit 101 is input to the traverse control unit of the system control unit 61. The system control unit 61 can control the movement of the pickup device 21 in the radial direction of the disk by controlling the pickup motor drive unit 35.

  The output of the preamplifier 22 is further input to the error signal generator 32. The error signal generator 32 generates an error signal suitable for each servo system using an output signal from the photoelectric conversion element of the optical pickup device 21 as described later. An error signal and a three-beam tracking error signal are generated. The error signal generator 32 generates a sub-beam sum signal as described later.

  The focus error signal is supplied to a focus servo circuit 33, and the phase difference tracking error signal and the three-beam tracking error signal are input to a tracking servo circuit 34. The output of the focus servo circuit 33 is supplied to a focus drive unit of the optical pickup device 21. The output of the tracking servo circuit 34 is supplied to the tracking drive unit of the optical pickup device 21 and also to the pickup motor drive unit 35. The pickup motor is a motor that controls the movement of the optical pickup device 21 in the radial direction of the disk, and is driven when supplementing tracking control or during a jump operation.

  When a plurality of optical systems are prepared in the pickup device 21, an aperture (NA) switching signal is supplied from the system control unit 61. In response to the NA switching signal, when the pickup device 21 is of a two-lens switching system (two optical lens systems are prepared), the lens is switched, and in the case of the aperture switching system, the aperture of the aperture is switched. Done. When the pickup device 21 is a bifocal lens system (two focal points exist in the optical axis direction), the switching need not be particularly performed.

  FIG. 6 shows a basic configuration of the pickup unit and the error signal generation unit 32 for obtaining a focus error signal, a three-beam tracking error signal, a phase difference tracking error signal, and the like in the optical pickup device 21.

  That is, the portion of the optical pickup device 21 will be described. The light emitter 21a emits irradiation light, and the irradiation light is split into a plurality of diffraction lights by the diffraction grating 21b. Of the diffracted light, the 0th-order diffracted light forms a main beam spot on the information track of the optical disc. The reflected light of the main beam spot is guided by the half mirror 21c and detected by the four-division diodes A, B, C, and D constituting the main beam detector. Further, two first-order diffracted lights of the plurality of diffracted lights form a sub-beam spot in a positional relationship sandwiching the information track of the disk before and after the main beam spot in the track direction. The reflected lights of the two sub-beam spots are guided by the half mirror 21c and detected by the sub-diodes E and F constituting the sub-beam detector.

  Outputs of the photodiodes A to F are introduced into buffer amplifiers 22a to 22f, respectively. The outputs A and C of the buffer amplifiers 22a and 22c are added by the adder 51 and output as an (A + C) signal. The outputs B and D of the buffer amplifiers 23b and 32d are added by the adder 52 and output as a (B + D) signal. The outputs of the adders 51 and 52 are input to a subtractor 53, subjected to an arithmetic processing of (A + C)-(B + D), and taken out as a focus error signal. The focus error signal is further input to the S-shaped level detection circuit of the focus control unit 54, and the focus state is detected. The focus control unit 54 controls the focus state to be stable. That is, the focus control unit 54 controls the current of the focus coil that drives the objective lens of the pickup device so that the amplitude of the focus error signal having the S-characteristic becomes zero (predetermined level). Thereby, focus control is realized.

  The outputs of the adders 51 and 52 are input to a phase difference detection unit 55. The phase difference detector 55 detects the phase difference between the (A + C) signal and the (B + D) signal. This detection signal is used as a phase difference tracking error signal. This phase difference tracking error signal is used as an effective signal when a disk (for example, DVD) having a narrow track pitch is reproduced.

  The outputs of the buffer amplifiers 22e and 22f are subjected to subtraction processing by a subtractor 56 to generate an (EF) signal. This (EF) signal is used as a three-beam tracking error signal. The three-beam tracking error signal is used as an effective signal when a disk (for example, a CD) having a wide track pitch is reproduced.

  The adder 57 performs A + B + A + C + B + D to generate an HF signal. The HF signal is a modulation signal and is input to the equalizer 23. Next, one of the phase difference tracking error signal and the three-beam tracking error signal is selected by the selector 58 and input to the tracking control unit 57. The tracking controller 57 controls the tracking coil of the optical pickup device 21 according to the acquired tracking error signal so that the tracking error is eliminated.

  Returning to FIG. As shown in FIG. 5, this system is provided with a track cross detection unit 101, which counts track cross signals during a track jump for special reproduction and a head search for a specific file, and The number can be accurately grasped. The traverse control unit and the traverse command unit are included in the system control unit 61.

FIG. 1 shows an embodiment of the present invention. FIG. 4 is a diagram showing a high-frequency signal and two detection outputs shown for explaining an operation example of the present invention. FIG. 9 is a diagram showing a high-frequency signal and two detection outputs similarly shown for explaining another operation example of the present invention. FIG. 9 is a diagram showing a high-frequency signal and two detection outputs shown for explaining still another operation example of the present invention. FIG. 1 is a diagram showing an overall configuration of a disc reproducing apparatus using the present invention. FIG. 5 is a diagram showing a pickup device, a preamplifier, and an error signal generator of FIG. 4. FIG. 4 is an explanatory diagram of a high-frequency signal and a track cross signal obtained from a low-density disk. FIG. 3 is an explanatory diagram of a high-frequency signal and a track cross signal obtained from a high-density disk.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 11 ... Optical disk, 12 ... Disk motor, 21 ... Optical pickup device, 22 ... Preamplifier, 100 ... Tracking error detection part, 101 ... Track cross detection part, 102 ... Peak detection circuit, 103 ... Bottom detection circuit, 104 ... Subtraction Unit 105: traverse control unit 106: traverse command unit

Claims (2)

Pickup means for optically reading a high-frequency signal recorded on an information track of an optical disc;
Driving means for driving the pickup means, while the pickup means reads the high-frequency signal, and such that the light spot of the pickup means crosses the track of the optical disc;
First detection means for obtaining a first detection output on the peak side with a charge / discharge time constant for a peak side of the high-frequency signal obtained from the pickup means;
A second detection output on the bottom side having a charge / discharge time constant for the bottom side of the high-frequency signal obtained from the pickup means (a charge / discharge time constant larger than the charge / discharge time constant for the peak side). Second detection means for obtaining
A disc reproducing device comprising: a subtraction unit that subtracts the second detection output from the first detection output to obtain a ripple waveform (track cross signal) corresponding to a traversed track. Pickup means for optically reading a high-frequency signal recorded on an information track of an optical disc;
Driving means for driving the pickup means, while the pickup means reads the high-frequency signal, and such that the light spot of the pickup means crosses the track of the optical disc;
It has a charge / discharge time constant for the peak side of the high-frequency signal obtained from the pickup means, and has different time constants of a charge time constant T1 and a discharge time constant T2 (T2 vs. T1 has a relationship of 1: 5 to 20). First detection means for detecting the first detection output to obtain a first detection output on the peak side;
A charge / discharge time constant for the bottom side of the high-frequency signal obtained from the pickup means (a charge / discharge time constant larger than the charge / discharge time constant for the peak side), and a charge time constant T2 and a discharge time constant Second detection means for detecting with a time constant of T1 (T2: T1 is a relation of 1 to 5 to 20) and obtaining a second detection output on the bottom side;
A disc reproducing device comprising: a subtraction unit that subtracts the second detection output from the first detection output to obtain a ripple waveform (track cross signal) corresponding to a traversed track.

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