JPH09106552A - Seek control method - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] A wobbling track is formed in advance by a signal obtained by modulating a wobbling signal based on address information.
The target data can be sought based on this address information. A preamble signal is extracted at the output of an adder circuit 17. The absolute time counter 19 generates the time code of the hour, minute, second and frame from the frame pulse A. A switching signal K corresponding to each bit of the time code is formed, and the switch circuit 15 is controlled by the signal K. The switch circuit 15 is a "0" series which is a pulse signal of 24 samples with a frequency of 20.05 kHz, or a "1" in which the twelfth sample is at a high level and the thirteenth sample is at a low level. Series, time code "0",
Select corresponding to "1". Then, a preamble is added, and a wobbled track is formed as a pre-groove according to the signal modulated based on the time code. The target data position is sought based on this time code.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc-shaped recording medium applied to an optical disc, for example, an optical disc, and more particularly to recording / reproducing data on / from information having information such as an absolute time code recorded as a guide groove. The present invention relates to a seek control method for controlling a seek operation of an optical pickup to be performed.

[0002]

2. Description of the Related Art A three-spot method, a push-pull method, a wobbling method, etc. have been proposed as a tracking error detection method for reproducing an optical disc. 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-divided optical sensor, and the difference output between 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. Wobbling is, for example, 22.05 [k
Hz].

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

[0004]

The use of a position detector such as a potentiometer for detecting the position of the optical pickup causes an increase in cost, and the position cannot always be detected accurately. It is desirable that the position of the optical pickup on the optical disk can be detected from the reproduced signal without providing a separate position detector. One method is to record a time code. However, recording the time code on the data track itself reduces the effective amount of data that can be recorded on one disc. When recording a time code by modulating it, it is conceivable to use PSK modulation. The PSK modulation forms the modulated signal shown in FIG. 12B having 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.

Accordingly, an object of the present invention is to provide a disk-shaped recording medium in which a wobbling track for detecting a tracking error is formed in advance, and a deflection control signal used for forming the wobbling track is:
Apply address information, no position detector, and
It is an object of the present invention to provide a seek control method that makes it possible to obtain position information without increasing data redundancy and record / reproduce target data based on this address information.

[0006]

According to a first aspect of the present invention, in a seek control method for controlling a seek operation of an optical pickup, a wobbling track whose wobbling cycle is modulated so as to include address information of an optical disc is used for addressing. This is a seek control method for extracting information and controlling the seek operation of the optical pickup based on the extracted address information.

A signal obtained by modulating a wobbling signal based on address information is used as the deflection control signal. The wobbling signal is used to detect a tracking error. For example, it is a signal having a frequency of 22.05 [kHz]. The address information is an absolute time code of a CD format which changes at a frequency lower than 22.05 [kHz], for example, 75 [Hz]. Even when the address information is superimposed, the deflection control signal has the predetermined frequency of the wobbling signal as a whole. Therefore, when the disc-shaped recording medium is reproduced, the wobbling signal of the predetermined frequency component can be separated from the reproduction signal, and the information signal can be extracted from the signal of the predetermined frequency component. Thus, since the deflection control signal has the address information, it is possible to seek the desired data on the disk-shaped recording medium based on the address information.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. This description is made 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. Modified example

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

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) in which information other than the music signal can be recorded is prepared. The subcode consists of eight independent bits (PQRSTUVW
, Which is referred to as), and currently two channels, P and Q, are used. In one frame, the above 8
The independent bits are EFM modulated and inserted. Each channel of the subcode is configured with 98 bits included in 98 frames as one block.

In the music signal and in the data of channel Q in the lead-out track, "AMIN", "AS"
An absolute time code referred to as “EC” or “AFRAME” is inserted. The absolute time code is “00:00:00” at the start of the program area, and changes according to the running time of the disk. From the above frame frequency, it is set to (1 second = 75 frames) in CD. Minutes, seconds, and frames of the absolute time code are
It is represented by two digits of the BCD code. That is, the minute and second change between (00-59) and the frame is (00
To 74), and a total of six characters of the 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. With EFM, the occupied frequency band is narrowed, the clock component is increased, and the DC component is reduced.

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

The change frequency of the absolute time code is 75 [H
z], a sampling frequency of 44.1 [kHz] includes 588 samples in one cycle. 4 each
One bit of the absolute time code data of 6 BCD characters (24 bits in total) of bits is a predetermined number, for example, 24 bits.
Samples (2 × 12 modulation bits) are allocated. As shown in FIG. 4A, 588 samples (= 1/75)
(Second)), a preamble having a length of 12 samples is added to the beginning of the data, 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. For the data bit “1”, the twelfth sample of the 24 samples is changed from low level to high level,
The third sample is changed from high level to low level,
Other samples are modulated into a sequence similar to the data bit “0” (“1” sequence). Also, the preamble is
The pattern is such that a high level and a low level are alternately repeated every three samples. "0" of the data bit is DC
Modulated to a free sequence. This sequence has a repetition frequency of 21.05 [kHz] and includes a sine wave component for tracking control. The “1” sequence corresponding to the data bit “1” is also DC-free, and the run length is limited to two samples. The “0” sequence corresponding to the data bit “0” is more preferable than the “1” sequence in terms of a sine wave component for tracking control. In the absolute time code, since the continuous length of “0” is longer than that of “1”, the “0” sequence is more preferable than the “1” sequence. The sequence corresponding to the preamble is also DC-free and occurs once every (1/75) second.

A method of actually generating the “1” sequence and the preamble sequence will be described with reference to FIG.
As shown in FIG. 5A, 24 samples of the “1” series
It is formed by adding a ternary signal that becomes (+1) in the twelfth sample and (-1) in the thirteenth sample with respect to the “0” sequence. The sequence of 12 samples corresponding to the preamble is “0” as shown in FIG. 5B.
The sequence is formed by adding signals that become (+1) in the eighth and fourteenth samples, respectively, and become (−1) in the eleventh and seventeenth 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
[Hz]) input terminal to which the frame pulse A 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 a frame pulse A and a clock pulse B, respectively. The clock pulse B is used as a clock input for the T flip-flop 3 and the decimal counter 4. The period 2T shown in FIG.
"0" series C is generated. The frame pulse A is supplied to the T flip-flop 3 and the decimal counter 4 as a clear input.

A frame pulse A is supplied as a set input of the SR flip-flop 5, and a carry output of the decimal 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 which becomes low level in a period from the frame pulse A to 12T is obtained. 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-decimal counter 8. The carry output E of the 24-base counter 8 clears the 24-base counter 8 and
Carry output E is supplied to addition circuit 9.

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

The parallel output of the 24-decimal counter 8 is
0 is supplied. The output signal of the decoder 10 generated when the content of the 24-decimal counter 8 becomes 12 is (1) the generation circuit 1
1 and the output signal of the decoder 10 generated when the content of the 24-decimal counter 8 becomes 13 is supplied to the (-1) generation circuit 12. Therefore, (1) FIG.
As shown in F, a 1-level pulse signal F is generated,
(-1) As shown in FIG.
Is generated. These pulse signals F and G are added by the adding circuit 13 and the adding circuit 1
3 is supplied to the adder circuit 14. Addition circuit 1
4 is supplied with the "0" sequence C from the T flip-flop 3, so that the output signal of the adder circuit 14 becomes the "1" sequence.

The "0" series and "1" series are supplied to two input terminals of the switch circuit 15, respectively. The switching circuit 15 is controlled by a switching signal K from a switching signal generation circuit 18, and data from the switching circuit 15 is supplied to a synthesis circuit 20. The synthesis circuit 20
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 a value logic signal generating circuit 16 and an adding circuit 17. As shown in FIG. 3H, the ternary logic signal generation circuit 16 synchronizes the frame pulse A with (0100-100100-10)
A pulse signal H having a value is generated. The pulse signal H and the “0” series C are supplied to the adding circuit 17, and the adding circuit 1
7, the preamble is obtained. A modulated sequence is obtained at the output terminal 21 of the synthesis circuit 20.

Reference numeral 19 denotes 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 are composed of two BCDs.
FIG. 2 shows an example of “28 minutes, 34 seconds, 63 frames”. In this case, “(0010) (1000) (0011) (0100) (0110)
(0011) "has 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
As shown in FIG. 3J, in synchronization with the pulse signal I, each data bit of the absolute time code is fetched, and when the data bit is "0", the switching signal K is low and when the data bit is "1", the switching signal K is high. (FIG. 3K) is formed. The “0” sequence is selected by the switch circuit 15 when the switching signal K is at a low level, and the “1” sequence is selected by the switch circuit 15 when the switching signal K is at a high level.

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 at CLV by a spindle motor 27. Reference numeral 28 denotes a recording laser, for example, an argon ion laser. An optical pickup 29 in which a laser beam from a recording laser 28 is surrounded by a broken line.
Is reflected by the galvanomirror 30 and is irradiated on the photoresist 26 via the objective lens 31. When the galvanometer mirror 30 is rotated by the galvanometer motor 32,
The laser beam is wobbled in the radial direction.

The galvano motor 32 is supplied with a drive signal from a mirror driver 33. 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 modulation circuit described above and a band limiting filter. The photoresist 26 is exposed to a spiral and wobbled pregroove by a laser beam.

FIG. 7 shows a glass master optically cut, and when developed, a concave portion corresponding to the pregroove is formed in the photoresist 26 as shown by. Next, aluminum 35 is deposited on the photoresist 26 (). Furthermore, nickel plating 3
6 is performed (), and the nickel plating 36 is peeled off 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 protection film addition by the stamper (). Optical disk 4
1 includes a polycarbonate substrate 37, a recording layer 38, and a transparent protective film 39, and the recording layer 38 includes a pre-groove 40
Are formed. 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 made of a material such as TbFeCo in the case of an erasable optical disk such as a magneto-optical disk. In addition, the present invention can be applied to a phase change type optical disk utilizing a crystal-amorphous phase change. The pre-groove 40
A pit is formed on the pre-groove 40 or in a region between the pre-grooves. FIG. 8 shows a part of the pre-groove 40 formed on the optical disc 41. The diameter of the optical disk 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 by the absolute time code of the 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. Band limitation toward the low band is necessary to suppress interference with the tracking error signal, and band limitation toward the high band is necessary to suppress interference with the EFM modulated signal (reproduced 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 a 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 supplied 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 having appropriate values, respectively. D / A converter 48
Is supplied to the analog low-pass filter 49. The analog low-pass filter 49 generates a wobbling signal. This wobbling signal is supplied to the mirror driver 33 (see FIG. 6).

E. Disc Recording / Reproducing Circuit FIG. 11 shows an example of the disc recording / reproducing circuit. The optical disk 41 having the same size as the CD has a spindle motor 55.
Is rotated by CLV. As the optical pickup 29, various structures are known, but in this example, an optical pickup in which both a focus adjustment unit and a tracking control unit are incorporated is used.

The optical pickup 29 is the semiconductor laser 5
6, collimator lens 57, beam splitter 58, 1 /
4 Wave plate 59, objective lens 60, actuator 61 composed of a coil and magnet for moving objective lens 60,
It is composed of an optical sensor 63 to which a laser beam from the beam splitter 58 is given via a cylindrical lens 62. A drive signal is supplied to the semiconductor laser 56 via a recording / reproduction switch 64.

The recording data from the terminal 65 is transmitted to a 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 / reproduction switch 64. The recording circuit 66 includes 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 disk 4
At the time of reproduction of 1, the predetermined DC voltage 67 is supplied to the semiconductor laser 56 via the reproduction side terminal p of the recording / reproduction switch 64.

The return beam from the optical disk 41 is applied to the optical sensor 63 via the beam splitter 58 and the cylindrical lens 62. The optical sensor 63 is configured as a four-part detector. Assuming that the output signals of the respective sensors of the optical sensor 63 are A, B, C, and D, the main reproduction signal represented by [(A + B) + (C + D)] is formed by the addition circuit 68, and the subtraction circuit 69 generates [ (A + B)-
(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 reproduced signal is converted into a pulse signal, and this pulse signal is supplied to the EFM demodulation circuit 73. The reproduced signal from the EFM demodulation circuit 73 is supplied to the data processing circuit 74. The reproduced data obtained from the data processing circuit 74 is supplied to an optical disk control circuit provided between the optical disk drive and the computer.

The bandpass filter 72 has a function of (22.05).
[KHz] ± 900 [Hz]), and the components of the reproduction signal corresponding to the pregroove are
The output signal of the band-pass filter 72 is supplied to the synchronous detection circuit 75 and the waveform shaping circuit 79. 22.05 from the terminal 76 to the synchronous detection circuit 75.
A [kHz] sine wave signal 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 a tracking control signal is given from the tracking servo circuit 78 to the actuator 61.

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

In the above-described embodiment of the present invention, since the frequency of the coded information signal (75 Hz) is sufficiently lower than the frequency of the wobbling signal (22.5 kHz), it is used as a wobbling signal for tracking control. It becomes easy to separate from the coded information signal, and therefore, the information signal can be multiplexed without causing any trouble to the tracking control.

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 pregroove signal of the optical disc.

[0041]

According to the present invention, a wobbling track for detecting a tracking error is formed in advance on a disk-shaped recording medium, and a deflection control signal for forming the wobbling track is provided with address information. By using the signal modulated based on the address information, the address information is recorded without increasing the redundancy of the data track, and when recording / reproducing such a disc, the target data is sought based on the address information. be able to.

[Brief description of the 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 chart used for explaining a modulation rule and a modulation method.

FIG. 6 is a schematic diagram illustrating 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 the optical disc.

FIG. 12 is a waveform diagram used for explaining 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 ...
Ternary logic signal generation circuit, 19 ... absolute time counter,
26 photoresist, 34 wobbling signal generation circuit, 40 pre-groove, 41 optical disk, 46 digital high-pass filter, 47
... Digital low-pass filter, 72 ... Band-pass filter, 75 ... Synchronous detection circuit

Claims (1)

[Claims] 1. A seek control method for controlling a seek operation of an optical pickup, wherein the address information is extracted from a wobbling track in which a wobbling cycle is modulated so as to include address information of an optical disc, and the extracted address is extracted. A seek control method for controlling a seek operation of the optical pickup based on information.