JPH0850724A - Reproducing equipment - Google Patents

Abstract

PURPOSE:To allow a coded information signal to be contained in a wobbling signal for forming a wobbling track, to enable recording of a time code or the like without increasing redundancy of a data track and to separate the information signal easily from a reproduction signal. CONSTITUTION:A wobbling track is formed beforehand in a disk 41. A recording signal from a recording circuit 66 is supplied to a semiconductor laser 56 and recorded on an optical disk 41. A readout light of the optical disk 41 is received by a photosensor 63 and a main reproduction signal is formed by an addition circuit 68. The component of a wobbling signal in the main reproduction signal is detected by a synchronous detection circuit 75, a tracking error signal is formed, while demodulation is made by a demodulating circuit 80, and thus a time code is obtained. Reproduced data are obtained by an EFM demodulating circuit 73 and a data processing circuit 74.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus for optically reproducing a signal from a disk-shaped recording medium, and more particularly to a wobbling signal modulated by an information signal, for example, a time code, and a wobbling signal modulated by the wobbling signal. The present invention relates to a reproducing device for reproducing a signal from a disc-shaped recording medium on which tracks are formed.

[0002]

2. Description of the Related Art A three-spot method, a push-pull method, a wobbling method and the like have been proposed as a method of detecting a tracking error when reproducing an optical disk. In the three-spot system, two sub-beam spots are located on both sides of the track, and the main beam spot is located at the center of the track, and the reflected light of the two sub-beams is paired on both sides of the main light sensor. A tracking error is detected from the difference output of the pair of optical sensors. In the push-pull method, a beam is applied to the center of the track, the reflected light is detected by a two-division optical sensor, and the difference output of the two optical sensors due to the bias of the diffracted light is detected as a tracking error. The wobbling method is a method in which a tracking error is detected from the synchronous detection output of the reproduction signal and a signal that vibrates the reproduction beam by causing the reproduction beam to meander on the spiral track, and a method of wobbling the track side at a predetermined frequency. There is. For wobbling, for example, 22.05 [kh
z] sine wave signal.

The optical disc rotation method is C
AV (constant angular velocity method) and CLV (constant linear velocity method)
There is. The CLV can increase the data recording density compared to the CAV, but requires a CLV servo that controls the rotation speed according to the radial position of the optical disc. The position of the disk in the radial direction is detected by a position detector such as a potentiometer which works in conjunction with the movement of the optical head.

[0004]

The use of a position detector such as a potentiometer to detect the position of the optical head causes an increase in cost, and the position cannot always be detected accurately. It is desirable that the position of the optical head on the optical disk can be detected from the reproduction signal without separately providing a position detector. As one method,
It is conceivable to record the time code. However, recording the time code on the data track itself reduces the effective amount of data that can be recorded on a single disc. Further, when the time code is modulated and recorded, PSK modulation may be used. PS
The K modulation forms the modulated signal shown in FIG. 12B with a phase corresponding to “1” and “0” of the data shown in FIG. 12A, respectively. However, there is a problem that the phase of the modulated signal becomes discontinuous.

Therefore, an object of the present invention is a reproducing apparatus for reading a signal from a disk-shaped recording medium on which a wobbling track is formed, without using a position detector and without increasing data redundancy. Another object of the present invention is to provide a reproducing apparatus capable of obtaining an information signal such as a time code.

[0006]

According to the present invention, in a reproducing apparatus for optically reproducing a signal from a disk-shaped recording medium, a wobbling signal having a predetermined frequency is coded as an information signal having a frequency lower than the predetermined frequency. An optical head for scanning a wobbling track from a disc-shaped recording medium having a wobbling track formed by a signal modulated based on the optical head and a tracking of the optical head based on the reproduction signal reproduced by the optical head. Control means for controlling the signal, first demodulation means for demodulating an information signal coded from the reproduction signal reproduced by the optical head, and conversion of the reproduction signal reproduced by the optical head into a pulse signal And a second demodulation means for demodulating the pulse signal converted by the conversion means, A reproducing apparatus, characterized in that it comprises a signal demodulated by the second demodulation means and data processing means for data processing.

As a deflection control signal for forming a wobbling track, a composite signal obtained by superimposing a wobbling signal and an information signal is used. The wobbling signal is used to detect tracking errors.
For example, the signal has a frequency of 22.05 [kHz]. The information signal is an absolute time code of the CD format which changes at a frequency lower than 22.05 [kHz], for example, 75 [Hz]. Since the frequency of the information signal is sufficiently lower than that of the wobbling signal, the deflection control signal as a whole has the predetermined frequency of the wobbling signal even when the information signal is superimposed. Therefore, when the disc-shaped recording medium is reproduced, the signal of the predetermined frequency component can be separated from the reproduced signal, and the information signal can be extracted from the signal of the predetermined frequency component. Thus, since the deflection control signal has the information of the absolute time code, the position of the head on the disk-shaped recording medium can be detected without increasing the redundancy of data.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. This description will be given in the following order. a. Time code and modulation rules b. Modulation circuit c. Formation of pre-groove d. Wobbling signal generation circuit e. Disc recording / reproducing circuit f. Modification

A. Time Code and Modulation Rule In this embodiment, a spiral pre-groove (guide groove) is wobbled (oscillated) at the time of recording to form an optical disc, and the time code is recorded on the pre-groove itself. As this time information, an absolute time code adopted in a CD (Compact Disc) is used. This absolute time code has a one-to-one correspondence with the scanning position of the head (pickup) of the optical disk, gives information on the disk diameter when the optical disk is rotated by the CLV (constant linear velocity) method, and also provides data access. Gives address information at time.

A signal is recorded on a CD with 588 bits of channel bits as one frame, and the frame frequency at a predetermined linear velocity is 7.35 [kHz]. C
In D, a space (user's bit or subcode) capable of recording information other than a music signal is prepared. The subcode consists of 8 independent bits (PQRSTUVW
, Which is referred to as), and currently two channels, P and Q, are used. Within one frame, the above 8
Independent bits are EFM-modulated and inserted. Each channel of the subcode is composed of 98 bits included in 98 frames as one block.

In the music signal and the data of the channel Q in the lead-out track, "AMIN""AS
An absolute time code called "EC""AFRAME" is inserted.The absolute time code is "00 minutes 00 seconds 00 frames" at the start of the program area and changes according to the running time of the disc. From the above frame frequency, it is set to (1 second = 75 frames) in CD. The minutes, seconds, and frames of the absolute time code are
It is expressed by two digits of the BCD code. That is, the minutes and seconds change between (00-59), and the frame changes to (00
˜74) and a total of 6 characters of BCD code are used.

EFM as channel coding
(Eight to Fourteen Modulation) converts a signal of 8 bits per symbol into 14 bits according to a predetermined rule. The EFM narrows the occupied frequency band, increases the clock component, and reduces the DC component.

On the other hand, in the tracking method of wobbling the pre-groove, a sine wave of 22.05 [kHz] is used. Therefore, when the absolute time code of the CD format is recorded as the wobbling pregroove, it is necessary to reproduce the sine wave signal having the above-mentioned frequency in a stable phase. In this example, (22.0
The absolute time code is modulated based on the sampling frequency of 5 × 2 = 44.1 [kHz].

The frequency of change of the absolute time code is 75 [H
z], the sampling frequency of 44.1 [kHz] includes 588 samples in one period. 4 each
A predetermined number, for example 24
Samples (2 × 12 modulation bits) are assigned. As shown in FIG. 4A, 588 samples (= 1/75
A preamble having a length of 12 samples is added to the beginning of (seconds), followed by data of (24 × 24 = 576) samples.

Each of the data bits "0", "1" and the preamble is modulated as shown in FIG. 4B.
The data bit “0” is modulated into a series (“0” series) in which 24 samples alternate between high level and low level. The data bit “1” is the 12th sample of 24 samples.
The thirteenth sample is changed from the low level to the high level, the thirteenth sample is changed from the high level to the low level, and the other samples are modulated into a sequence (“1” sequence) similar to the data bit “0”. . Also, the preamble is
It is a pattern in which a high level and a low level are alternately repeated every three samples. Data bit “0” is DC
It is modulated into a free sequence. This series has a repetition frequency of 21.05 [kHz] and contains a sine wave component for tracking control. The "1" series corresponding to the "1" of the data bit is also DC free, and the run length is limited to 2 samples. The "0" series corresponding to the "0" of the data bit is more preferable than the "1" series in terms of a sine wave component for tracking control. Since the continuous length of the absolute time code is longer in "0" than in "1", the "0" series is set as a preferable pattern than the "1" series. The sequence corresponding to the preamble is also DC-free and occurs once every (1/75) seconds.

A method of actually generating the "1" sequence and the preamble sequence will be described with reference to FIG.
As shown in FIG. 5A, the 24 samples of the “1” series are
It is formed by adding a ternary signal that becomes (+1) at the 12th sample and (-1) at the 13th sample to the “0” sequence. The sequence of 12 samples corresponding to the preamble is “0” as shown in FIG. 5B.
It is formed by adding signals to the sequence, which are (+1) at the 8th and 14th samples and (-1) at the 11th and 17th samples, respectively.

B. Modulation Circuit As described above, FIG. 1 shows an example of a modulation circuit that modulates each “0” or “1” of a data bit into a series of 24 samples of a predetermined pattern.

In FIG. 1, 1 is a frame frequency (75
Input terminal to which frame pulse A of [Hz] is supplied, 2
Is an input terminal to which a clock pulse B having a frequency of 44.1 [kHz] is supplied. The period of the clock pulse B is represented by T. 3A and 3B show the frame pulse A and the clock pulse B, respectively. The clock pulse B is used as a clock input to the T flip-flop 3 and the binary counter 4. From the T flip-flop 3 to the cycle 2T shown in FIG. 3C
"0" sequence C of is generated. The frame pulse A is supplied as a clear input to the T flip-flop 3 and the binary counter 4.

The frame pulse A is supplied as a set input of the SR flip-flop 5, and the carry output of the binary counter 4 is supplied as a reset input thereof. Therefore, the negative output terminal of the SR flip-flop 5 is
As shown in D, a pulse signal D that is at a low level is obtained in the period from frame pulse A to 12T. This pulse signal D is supplied to the AND gate 6 and the edge detection circuit 7. The clock pulse B is supplied to the AND gate 6, and the clock pulse passed through the AND gate 6 is supplied to the 24-base counter 8. The carry output E of the 24-base counter 8 clears the 24-base counter 8 and
The carry output E is supplied to the adder circuit 9.

The carry output E of the 24-base counter 8 is generated every 24T after the pulse signal D becomes high level, as shown in FIG. 3E. Further, the edge detection circuit 7 generates a pulse signal that coincides with the rising edge of the pulse signal D, and this pulse signal is supplied to the addition circuit 9.
Therefore, the pulse signal I from the adder circuit 9 is generated every 24T after the period of 12T of the preamble, as shown in FIG. 3I.

The parallel output of the 24-base counter 8 is the decoder 1
0 is supplied. The output signal of the decoder 10 generated when the content of the 24-base counter 8 becomes (1) the generation circuit 1
The output signal of the decoder 10, which is supplied to 1 and is generated when the content of the 24-bit counter 8 becomes 13, is supplied to the (-1) generation circuit 12. Therefore, from (1) generation circuit 11 to FIG.
As shown in F, a pulse signal F of 1 level is generated,
As shown in FIG. 3G, (-1) generating circuit 12 outputs (-1)
The pulse signal G having the level of is generated. These pulse signals F and G are added by the adder circuit 13, and the adder circuit 1
The output signal of No. 3 is supplied to the adder circuit 14. Adder circuit 1
Since the "0" series C from the T flip-flop 3 is supplied to 4, the output signal of the adder circuit 14 becomes the "1" series.

These "0" series and "1" series are supplied to the two input terminals of the switch circuit 15, respectively. The switch circuit 15 is controlled by the switching signal K from the switching signal generating circuit 18, and the data from the switching circuit 15 is supplied to the synthesizing circuit 20. The synthesis circuit 20 is 5
A preamble of 12 samples is added for every 88 samples. The preamble is supplied with the frame pulse A 3
It is formed by the value logic signal generation circuit 16 and the addition circuit 17. As shown in FIG. 3H, the ternary logic signal generation circuit 16 synchronizes with the frame pulse A and outputs three (0100-100100-10) signals.
Value pulse signal H is generated. The pulse signal H and the “0” series C are supplied to the adder circuit 17, and the adder circuit 1
The preamble is obtained from 7. A modulated sequence is obtained at the output terminal 21 of the synthesis circuit 20.

Reference numeral 19 is a CD based on the frame pulse A.
An absolute time counter that generates an absolute time code in a format. FIG. 2 shows the configuration of the absolute time counter 19, in which each frame, second, and minute consists of two BCDs.
FIG. 2 shows an example of “28 minutes 34 seconds 63 frames”, and in this case, “(0010) (1000) (0011) (0100) (0110)
Six characters of BCD "(0011)" have occurred. The absolute time code from the absolute time counter 19 is supplied to the switching signal generation circuit 18. Switching signal generation circuit 18
Then, in synchronization with the pulse signal I, as shown in FIG. 3J, each data bit of the absolute time code is taken in, and the switching signal K of low level when the data bit is “0” and high level when the data bit is “1”. (FIG. 3K) is formed. When the switching signal K is low level, the "0" series is selected by the switch circuit 15, and when the switching signal K is high level, the "1" series is selected by the switch circuit 15.

C. Formation of Pregroove FIG. 6 shows a cutting system for forming a pregroove on an optical disc. In FIG. 6, reference numeral 25 denotes a glass disk, and a photoresist 26 is applied on the glass disk 25. The glass disk 25 is rotated by CLV by a spindle motor 27. 28 is a recording laser, for example, an argon ion laser. The laser beam from the recording laser 28 is reflected by the galvano mirror 30 of the optical head 29 surrounded by the broken line, and is applied to the photoresist 26 via the objective lens 31. By rotating the galvanometer mirror 30 by the galvanometer motor 32, the laser beam is wobbled in the radial direction.

A drive signal from the mirror driver 33 is supplied to the galvano motor 32. The wobbling signal is supplied from the wobbling signal generation circuit 34 to the mirror driver 33. Wobbling signal generation circuit 34
Is composed of the above-mentioned modulation circuit and band limiting filter. A spiral and wobbling pre-groove is exposed on the photoresist 26 by a laser beam.

In FIG. 7, reference numeral 7 denotes an optically cut glass master, and when developed, a concave portion corresponding to the pre-groove is formed in the photoresist 26 as shown by. Next, aluminum 35 is vapor-deposited on the photoresist 26 (). Furthermore, nickel plating 36
Is applied (), and the nickel plating 36 is removed to produce a metal master (). A stamper is made from this metal master, and the optical disc 41 is manufactured through the steps of injection molding, recording layer formation and protective film addition by the stamper (). Optical disc 41
Has a polycarbonate substrate 37, a recording layer 38 and a transparent protective film 39, and a pre-groove 40 is formed in the recording layer 38. If necessary, the optical disc 41 has a laminated structure, and double-sided recording is possible.

The recording layer 38 is made of a material such as SbSe or BiTe in the case of a write-once (WORM) optical disk, and is made of a material such as TbFeCo in the case of an erasable optical disk such as a magneto-optical disk. The present invention can also be applied to a phase-change type optical disk that utilizes a crystal-amorphous phase change. The pre-groove 40 is
The groove is a U groove or a V groove, and pits are formed on the pregroove 40 or in a region between the pregrooves. FIG. 8 shows a part of the pre-groove 40 formed on the optical disc 41. The diameter of the optical disc 41 is the same as that of the CD.

D. Wobbling Signal Generation Circuit FIG. 9 shows a wobbling signal generation circuit, and 45 is the modulation circuit shown in FIG. From the modulation circuit 45,
A pulse train modulated with an absolute time code in CD format is generated. This pulse train basically has a repetition frequency of 22.05 [kHz], and the band is limited by passing the pulse train through a filter. The band limitation toward the low frequency side is necessary to suppress interference with the tracking error signal, and the bandwidth limitation toward the high frequency side is necessary to suppress interference with the EFM modulation signal (reproduction data).

The digital high-pass filter 46 connected to the modulation circuit 45 is provided to limit the band on the low frequency side, and has a frequency characteristic indicated by 50 in FIG. In FIG. 10, fn is 22.05
[KHz] and fs represent 44.1 [kHz], respectively.

The output signal of the digital high-pass filter 46 is supplied to the digital low-pass filter 47. The digital low pass filter 47 has a frequency characteristic indicated by 51 in FIG. As the digital low pass filter 47, a configuration using oversampling is used. Digital low pass filter 47
Is output to the D / A converter 48. The D / A converter 48 converts the high level and the low level of the pulse signal into DC voltages of appropriate values, respectively. D / A converter 48
Is supplied to the analog low-pass filter 49. A wobbling signal is generated from the analog low pass filter 49. This wobbling signal is supplied to the mirror driver 33 (see FIG. 6).

E. Disc Recording / Reproducing Circuit FIG. 11 shows an example of a disc recording / reproducing circuit to which the present invention is applied. The optical disk 41 having the same size as the CD is rotated by the spindle motor 55 at CLV. Various types of optical heads are known as optical heads, but in this example, an optical head incorporating both a focus adjustment section and a tracking control section is used.

The optical head includes a semiconductor laser 56, a collimator lens 57, a beam splitter 58, and a 1/4 wavelength plate 5.
9, an objective lens 60, an actuator 61 including a coil and a magnet for moving the objective lens 60, and an optical sensor 63 to which a laser beam from a beam splitter 58 is given via a cylindrical lens 62. A drive signal is supplied to the semiconductor laser 56 via the recording / reproducing changeover switch 64.

The recording data from the terminal 65 is recorded by the recording circuit 66.
The recording signal from the recording circuit 66 is supplied to the semiconductor laser 56 through the recording side terminal r of the recording / reproducing changeover switch 64. The recording circuit 66 is provided with a circuit for adding a redundant code of an error correction code, an EFM modulation circuit, a recording timing control circuit, and the like. Optical disc 4
At the time of reproducing 1, the predetermined DC voltage 67 is supplied to the semiconductor laser 56 via the reproducing side terminal p of the recording / reproducing changeover switch 64.

The return beam from the optical disc 41 is applied to the optical sensor 63 via the beam splitter 58 and the cylindrical lens 62. The optical sensor 63 has a four-divided detector configuration. Assuming that the output signals of the respective sensors of the optical sensor 63 are A, B, C and D, the addition circuit 68 forms the main reproduction signal represented by [(A + B) + (C + D)] and the subtraction circuit 69 [ (A + B)-
A focus error signal represented by (C + D)] is formed. This focus error signal is supplied to the focus servo circuit 70, and a control signal for focus servo is supplied to the actuator 61.

The main reproduction signal from the adder circuit 68 is supplied to the waveform shaping circuit 71 and the bandpass filter 72. In the waveform shaping circuit 71, the reproduction signal is converted into a pulse signal, and this pulse signal is supplied to the EFM demodulation circuit 73. The reproduction signal from the EFM demodulation circuit 73 is supplied to the data processing circuit 74. The reproduction data obtained from the data processing circuit 74 is supplied to the optical disc control circuit provided between the optical disc drive device and the computer.

The bandpass filter 72 has a function of (22.05).
It has a pass band of [kHz] ± 900 [Hz]), and the component of the reproduction signal corresponding to the pre-groove is the band pass filter 7
The output signal of the bandpass filter 72 is separated by 2, and is supplied to the synchronous detection circuit 75 and the waveform shaping circuit 79. The synchronous detection circuit 75 has 22.05 from the terminal 76.
A sinusoidal signal of [kHz] is supplied. Synchronous detection circuit 75
Is supplied to the low pass filter 77, and the tracking error signal is extracted from the low pass filter 77. This tracking error signal is supplied to the tracking servo circuit 78, and the tracking servo circuit 78 gives a tracking control signal to the actuator 61.

The waveform shaping circuit 79 obtains a pulse train modulated with an absolute time code in CD format.
This pulse train is supplied to the demodulation circuit 80, and the demodulation circuit 80
At, the pulse train is demodulated into absolute time coded data bits. The absolute time code obtained from the demodulation circuit 80 is supplied to a system controller (not shown) of the optical disk drive device, and is used for CLV servo of the spindle motor 55, control of the scanning position of the optical head during seek operation, and the like.

F. Modified Example The present invention can be applied not only to the time code of the CD format, but also to the case where other time code such as SMPTE or digital data other than the time code is modulated and recorded.

Further, according to the present invention, information such as a time code may be superimposed on a signal other than the signal of the pre-groove of the optical disc.

[0040]

According to the present invention, it is possible to superimpose another information signal such as a time code on the deflection control signal for forming the wobbling track for detecting the tracking error. A time code or the like can be recorded without increasing the track redundancy.

Further, according to the present invention, the wobbling signal and its frequency (22.05 kHz) sufficiently lower than the frequency (7.
Since the wobbling signal is modulated based on the coded information signal of 5 Hz), it is easy to separate the wobbling signal for tracking control and the coded information signal.

[Brief description of drawings]

FIG. 1 is a block diagram of a modulation circuit for modulating an absolute time code into a pulse train in an embodiment of the present invention.

FIG. 2 is a block diagram of a counter that generates an absolute time code.

FIG. 3 is a time chart for explaining the operation of the modulation circuit.

FIG. 4 is a waveform diagram used for explaining a modulation rule and a modulation method.

FIG. 5 is a waveform diagram used for explaining a modulation rule and a modulation method.

FIG. 6 is a schematic diagram showing a configuration of a cutting system.

FIG. 7 is a schematic diagram illustrating an example of a method for manufacturing an optical disc.

FIG. 8 is a schematic diagram showing a pre-groove on an optical disc.

FIG. 9 is a block diagram of an example of a wobbling signal generation circuit.

FIG. 10 is a frequency spectrum diagram used for explaining band limitation in the wobbling signal generation circuit.

FIG. 11 is a block diagram of an example of a recording / reproducing circuit of an optical disc.

FIG. 12 is a waveform diagram used to describe conventional PSK modulation.

[Explanation of symbols]

 1 Frame pulse input terminal 2 Clock pulse input terminal 4 Decimal counter 8 24 decimal counter 15 Switch circuit 16 3-value logic signal generation circuit 19 Absolute time counter 26 Photoresist 34 Wobbling signal generation circuit 40 Pre-groove 41 Optical disc 46 Digital high-pass Filter 47 Digital low-pass filter 72 Band-pass filter 75 Synchronous detection circuit

Claims (5)

[Claims] 1. A reproducing apparatus for optically reproducing a signal from a disc-shaped recording medium, wherein a wobbling signal having a predetermined frequency is modulated based on a coded information signal having a frequency lower than the predetermined frequency. An optical head for scanning the wobbling track from the disk-shaped recording medium having the formed wobbling track to reproduce a signal, and to control the tracking of the optical head based on the reproduction signal reproduced by the optical head. Tracking control means, first demodulation means for demodulating the coded information signal from the reproduction signal reproduced by the optical head, and the reproduction signal reproduced by the optical head into a pulse signal. Converting means and second demodulation for demodulating the pulse signal converted by the converting means Stage and playback apparatus characterized by comprising a data processing means for data processing a signal demodulated by the second demodulation means. 2. The reproducing apparatus according to claim 1, wherein the information signal is absolute time information. 3. The reproducing apparatus according to claim 1, wherein the wobbling track is a guide groove. 4. The reproducing apparatus according to claim 1, wherein the first demodulating means is a signal obtained by code-modulating a clock signal having a frequency twice the predetermined frequency based on the information signal. A reproducing apparatus characterized by demodulating the information signal. 5. The reproducing apparatus according to claim 1, wherein the scanning position of the optical head is controlled during a seek operation based on the demodulated coded information signal. apparatus.