JPH07254155A - Optical disk and tracking device of sampled servo system - Google Patents

Abstract

PURPOSE:To obtain an optical disk which eliminates a cutting machine having an optical device to execute wobbling by positioning all pits of a servo field including clock pits on tracks. CONSTITUTION:The synchronizing pits of the respective tracks are formed in the same radial direction. The clock pits for tracking servo are formed on the tracks simultaneously with clock extraction after the synchronizing pits. The clock pits on the respective pits within three pieces of the track groups are not formed on the same radius and are formed on the same straight line in the radial direction on every other three pieces of the tracks. The optical disk is formed by positioning the servo fields (not shown in Fig.) for each of the respective segments. Then, the optical disk having an inter-track interval of 0.8mum is obtd. without using the cutting machine having the optical device to execute wobbling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sampled servo type optical disk and a tracking device provided in a player playing the optical disk.

[0002]

2. Description of the Related Art In an optical disc having a sampled servo system recording format, a servo field pre-formatted for generating signals necessary for disc performance such as a sync signal, a tracking error signal, and a reproduction clock signal is provided in each segment. It is provided in front of each data field. For example, in the format that complies with the ISO standard, one sector consists of 43 segments (18 bytes each), and the sector synchronization signal and sector address are pre-formatted in the leading segment. In each remaining segment, the first 2 bytes are a servo field and the remaining 16 bytes are a data field. In the servo field, three pre-pits are formed, and the two preceding pits are wobbled in different directions in the radial direction from the track by 1/4 of the track pitch. These two pits are used for generating a tracking error signal, and one pit located on the remaining track is used for generating a reproduction clock signal.

On the other hand, the applicant of the present invention has proposed a recording format of a sampled servo type optical disk capable of double-density recording, which has already been disclosed as Japanese Patent Laid-Open No. 3-64978. Also in the servo field of the double-density recording format, two pits are wobbled in different directions in the radial direction from above the track for generating a tracking error signal.

[0004]

However, in order to form the wobbling pits on the disc, the light beam must be swung left and right during the disc cutting, and an optical device for wobbling the cutting machine is required. there were. Therefore, an object of the present invention is to provide an optical disc and a tracking error signal and a reproduction clock signal by arranging pits in a servo field so that a cutting machine equipped with an optical device for wobbling is not used. An object is to provide a tracking device for an optical disc.

[0005]

The optical disc of the present invention comprises:
In addition to the sync pit for generating the sync signal, a servo field having a clock pit for generating the reproduction clock signal and the tracking error signal, and a data field for recording data after the servo field are provided. An optical disc of a constant angular velocity type of a sampled servo system provided in a track, wherein the synchronization pits of each track are located in the same radial direction, and are composed of a series of n (n is an integer of 3 or more) tracks. In the track group, the clock pits on each track do not exist on the same straight line in the radial direction, and the clock pits on every nth track are on the same straight line in the radial direction.

Further, the tracking device of the present invention is located after the servo field having a servo field having a clock pit for generating a reproduction clock signal and a tracking error signal in addition to the synchronous pit for generating a synchronization signal. Each track has a data field for recording data, and the sync pits of each track are located in the same radial direction. In one track group consisting of a series of n tracks, clock pits on each track are provided. Are not on the same straight line in the radial direction, and clock pits on every nth track are on the same straight line in the radial direction. Reading means for irradiating a beam to read information recorded as pits on an optical disc , A synchronization detecting means for detecting the time when the synchronous pit is read from the read signal by the reading means, and a time corresponding to the distance from each synchronous pit to each clock pit in one track group based on the detection output of the synchronous detecting means. Timing signal generating means for generating timing signals when the time has elapsed, n holding means for individually holding read signals by the reading means at the time of generation of each timing signal, and holding signal levels of the n holding means Of the n holding means that is determined corresponding to the holding means that holds the maximum value of the two, the difference between the two signal levels held by the two holding means is output as a tracking error signal. It is characterized by that.

[0007]

According to the optical disk of the present invention, the sync pits are located in the same radial direction in the servo field of each track, and the clock pits on each track are the same in one track group consisting of a series of n tracks. The clock pits on the nth track that do not exist on the straight line in the radial direction are on the same straight line in the radial direction.

Further, in the tracking device of the present invention, when the time corresponding to the distance from the synchronous pit to each clock pit in one track group elapses from the time when the synchronous pit is detected, the reading signal by the reading means is set to n.
2 held by two holding means of n holding means each of which is determined by the holding means that holds the maximum value of the holding signal levels of the n holding means. The difference between the two signal levels, that is, the difference between the black stroke amounts is output as a tracking error signal.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. Figure 1 shows a double density recording CAV (Constant A
It shows a pit formed in the servo field of an optical disc of ngular velocity type. 1 for that disc
A servo field is formed as a prepit for each segment of each track. In FIG. 1, each track shown by the one-dot chain line is formed at a half pitch of the conventional pitch, for example, at an interval of 0.8 μm. In each track, a sync pit is formed at the beginning of the segment.
The synchronization pits of each track are located in the same radial direction. After the synchronization pit, a clock pit is formed on the track for tracking servo as well as clock extraction. A series of three-track clock pits constitutes one track group, and the positions of the respective pits from the synchronous pits are different for each track in the track group.
That is, in the three track groups, the clock pits on each track do not exist on the same straight line in the radial direction, and the clock pits on every third track do not exist on the same straight line in the radial direction.

The respective clock pits of the three tracks are the first clock pits of the clock pits of the inner track,
The clock pit of the next track is the second clock pit,
Further, assuming that the clock pit of the next track is the third clock pit, the positions of the first clock pit, the second clock pit, and the third clock pit are away from the synchronization pit in this order. Letting aT be the distance from the rear edge of the synchronization pit to the first clock pit, bT be the distance from the rear edge of the synchronization pit to the second clock pit, and cT be the distance from the rear edge of the synchronization pit to the third clock pit. bT-aT = cT-bT = nT. here,
a, b, c, n are positive integers, and a <b <c.
T is 1 bit long. The first, second and third clock pits are repeatedly formed in the outer peripheral direction of the disc. A data field (not shown) is located after such a servo field for each segment.

FIG. 2 is a disc player (not shown) for playing the disc having the servo field shown in FIG.
The tracking device provided in FIG. In this tracking device, the pickup 11
A light beam for reading information is emitted from the optical disc, and is a read signal RF read from the disc by the pickup 11.
A (high frequency) signal is supplied to the A / D converter 12. RF
After the signal is converted into a digital RF signal in the A / D converter 12, the clock pit phase detectors 13a-13
c, the threshold calculation unit 14 and the edge interval / synchronization detection unit 15. Clock pit phase detector 13
Each of a to 13c obtains a phase error signal indicating the sample value difference before and after the clock pit waveform from the digital RF signal according to the clock sampling signal. The sampling positions before and after the clock pit waveform are, for example, S shown in FIG.
₁ and S ₂ . Clock pit phase detectors 13a to 13
The PLL circuit 16 is connected to c via the changeover switch SW1, and the PLL circuit 16 generates a reproduction clock pulse. This clock pulse is supplied to the A / D converter 12, the edge interval / synchronization detection unit 15, and the timing generation unit 17.

The threshold calculation unit 14 is a digital R
The positive and negative peak levels of the F signal are detected every predetermined period,
An intermediate value between the positive and negative peak levels is calculated as the threshold level. When the edge interval / synchronization detection unit 15 detects a digital RF signal that exceeds the threshold level, the time that exceeds the threshold level is obtained by counting the clock pulses from the PLL circuit 16, and when the count value of the clock pulses is equal to or greater than the first predetermined value, the synchronization is performed. A synchronization detection signal indicating the detection of pits is generated.

A timing generator 17 is connected to the edge interval / sync detector 15. Timing generator 17
Generates a clock sampling signal and timing signals AS, BS, CS by counting the clock pulses from the PLL circuit 16 with reference to the time when the synchronization detection signal is generated, and the clock sampling signal is the clock pit phase detector 13a ...
13c is supplied separately. Timing signal AS
Is generated corresponding to the first clock pit position, the timing signal BS is generated corresponding to the second clock pit position, and the timing signal CS is generated corresponding to the third clock pit position. Also, the timing signals AS, BS, C
S is generated on the basis of the synchronization pit regardless of whether the first to third clock pits exist.

The A / D converter 12 is further connected to three sample memories 21a to 21c. A timing signal AS is supplied from the timing generator 17 to the sample memory 21a and a timing signal BS is supplied to the sample memory 21b in order to determine the time when each of the sample memories 21a to 21c stores the output signal of the A / D converter 12. And the timing signal C is supplied to the sample memory 21c.
S is supplied. Each of the sample memories 21a to 21c stores the output signal of the A / D converter 12 in accordance with the timing signal, and outputs the stored signal to the next new signal storage.

A subtractor 22 is connected to the outputs of the sample memories 21b and 21c, and the sample memories 21a and 21c are connected.
A subtractor 23 is connected to the output of the sample memory 21
A subtractor 24 is connected to the outputs of a and 21b. The subtractor 22 subtracts the stored output signal of the sample memory 21b from the stored output signal of the sample memory 21c. The subtractor 23 subtracts the stored output signal of the sample memory 21c from the stored output signal of the sample memory 21a. Similarly, the subtractor 24 subtracts the stored output signal of the sample memory 21a from the stored output signal of the sample memory 21b. The changeover switch SW2 is connected to the outputs of the subtracters 22 to 24. The maximum value detection circuit 25 is connected to the changeover switch SW2, and the changeover switch SW2 selects any one of the output signals of the subtractors 22 to 24 according to the selection signal output from the maximum value detection circuit 25. Output. The maximum value detection circuit 25 is connected to the outputs of the sample memories 21a to 21c, detects the maximum value of the stored output signals of the sample memories 21a to 21c, and generates a selection signal according to the result of obtaining the maximum value. To do.

In such a configuration, the A / D converter 12 obtains a sample value according to the clock pulse from the RF signal read by the pickup 1 from the disc and digitizes it. An intermediate value between the positive and negative peak levels of the digital RF signal is calculated as the threshold level by the threshold calculation unit 14. When a digital RF signal exceeding the threshold level is detected, the time exceeding the threshold level is obtained in the edge interval / synchronization detecting section 15 by counting clock pulses.

The edge interval / sync detector 15 generates a sync detection signal when the count value of the clock pulses is equal to or larger than the first predetermined value. The clock pit phase detecting unit 13 generates the clock sampling signal that counts the clock pulses based on the time when the synchronization detection signal is generated and indicates the reading time points of the first to third clock pits in the timing generating unit 17.
a to 13c. The clock sampling signal is individually generated corresponding to the first, second and third clock pits, the clock sampling signal for the first clock pit is supplied to the phase detector 13a, and the clock sampling signal for the second clock pit is supplied. Is supplied to the phase detection unit 13b, and the clock sampling signal for the third clock pit is supplied to the phase detection unit 13c. Each of the clock pit phase detectors 13a to 13c obtains a phase error signal indicating a sample value difference before and after the clock pit waveform from the digital RF signal according to the supplied clock sampling signal.

The digital RF signal output from the A / D converter 12 is stored in the sample memory 21a when the timing signal AS is generated, is stored in the sample memory 21b when the timing signal BS is generated, and is stored in the timing signal CS.
Is stored in the sample memory 21c. Therefore, when the information reading point of the pickup 11 is located at or near the track where the first clock pit is formed, the level stored in the sample memory 21a becomes maximum, and the maximum value detection circuit 25 generates the first selection signal. . The changeover switches SW1 and SW2 are set to the selected position A in response to the first selection signal, and the phase error signal output from the clock pit phase detection unit 13a is supplied to the PLL circuit 16 via the changeover switch SW1. The PLL circuit 16 generates a reproduction clock pulse according to the phase error signal from the phase detector 13a. Further, a signal obtained by subtracting the storage output signal of the sample memory 21b from the storage output signal of the sample memory 21c is output from the subtractor 22 to the changeover switch SW2.
Is output as a tracking error signal via.

Similarly, when the information reading point of the pickup 11 is located at or near the track where the second clock pit is formed, the level stored in the sample memory 21b becomes the maximum, and the maximum value detection circuit 25 makes the second selection. Generate a signal. Changeover switch SW according to the second selection signal
1 and SW2 are respectively at the selected position B, and the phase error signal output from the clock pit phase detector 13b is supplied to the PLL circuit 16 via the changeover switch SW1. P
The LL circuit 16 generates a reproduction clock pulse according to the phase error signal from the phase detector 13b. In addition, from the storage output signal of the sample memory 21a,
A signal obtained by subtracting the stored output signal of c is output as a tracking error signal from the subtractor 23 via the changeover switch SW2.

Further, when the information reading point of the pickup 11 is located at or near the track where the third clock pit is formed, the level stored in the sample memory 21c becomes the maximum, and the maximum value detection circuit 25 causes the third selection signal to be output. To occur. Changeover switch SW1, according to the third selection signal
SW2 becomes the selected position C, and the phase error signal output from the clock pit phase detection unit 13c is supplied to the PLL circuit 16 via the changeover switch SW1. PLL
The circuit 16 generates a reproduction clock pulse according to the phase error signal from the phase detector 13c. Further, a signal obtained by subtracting the storage output signal of the sample memory 21a from the storage output signal of the sample memory 21b is output as a tracking error signal from the subtractor 24 via the changeover switch SW2.

FIGS. 4A to 4C show the timing signal A.
The relationship between the RF signal level obtained according to S, BS, and CS and the information reading point of the pickup 11 is shown. As shown in FIG. 4A, the RF signal level of the first clock pit sampled according to the timing signal AS is as shown in FIG. 4A, when the information reading point of the pickup 11 is on the track t ₁ in which the first clock pit of the disc is formed. the maximum one time, decreases with distance from it, becomes minimal in the middle of the track t ₃ when the track t ₂ of the second clock pits are formed third clock pit is formed, raised toward the next track t ₁ To do. The RF signal level by the second clock pit sampled according to the timing signal BS and the RF signal level by the third clock pit sampled according to the timing signal CS are also as shown in FIGS. 4 (b) and 4 (c). This is similar to the case of the RF signal level by one clock pit.

4D to 4F show the relationship between the output levels of the subtractors 22 to 24 and the information reading point of the pickup 11. That is, the output level of the subtractor 22 will be described. As shown in FIG. 4D, the pickup 1 is placed on the track t ₁ in which the first clock pit is formed.
It becomes 0 when there is an information reading point of 1, decreases from that point on the track t ₂ side, and becomes minimum on the track t ₂ . It increases as it gets closer to the track t ₃ side, and becomes maximum on the track t ₃ . The output levels of the subtracters 23 and 24 are also the same as the change of the output level of the subtractor 22 as shown in FIGS. 4 (e) and 4 (f).

Pickup 11 from FIGS. 4 (a)-(c)
When the information reading point of (1) moves across the disk in the radial direction, a tracking error signal as shown in FIG. 4 (g) is obtained. FIG. 5 shows the sampling timing of the RF signal when the information reading point of the pickup 11 is moved. That is, when the information reading point moves near the track where the second clock pit is formed on the disk as shown by the broken line, the segments N and N +
At 1, the level of the RF signal corresponding to the second clock pit becomes high. Therefore, the timing signals AS and B
The maximum value detection circuit 25 generates a second selection signal according to each signal level sampled at the time of generation of S and CS,
This means that the information reading point has moved near the track where the second clock pit is formed. As a result, as described above, the changeover switches SW1 and SW2 are set to the selection position B in response to the second selection signal, and the phase error signal output from the clock pit phase detector 13b is transferred to the PLL circuit via the changeover switch SW1. 16 are supplied. In this case, B ′ and B ″ shown in the figure represent the time when the clock sampling signal for the clock pit phase detection unit 13b is generated. Further, the storage output signal of the sample memory 21c is subtracted from the storage output signal of the sample memory 21a. The signal is output from the subtractor 23 as a tracking error signal via the changeover switch SW2.

In the segment N, the information reading point passes through the track side where the first clock pit is formed.
The output value stored in the sample memory 21a is the sample memory 2
It becomes larger than the stored output value of 1c. On the other hand, segment N +
In No. 1, since the information reading point passes through the track side where the third clock pit is formed, the stored output value of the sample memory 21c becomes larger than the stored output value of the sample memory 21a. Therefore, for segment N, segment N + 1
Then, the polarity of the tracking signal is inverted.

In the above embodiment, the first to the first
Although three continuous tracks having the third clock pit are one track group, the clock pits may be formed with four tracks as one track group as shown in FIG.
Further, as shown in FIGS. 1 and 6, the distance from the synchronization pit to the clock pit is gradually increased toward the outer peripheral side of the disk in one track group, but it is not necessary to be sequentially increased. In one track group, the clock pits on each track may not be present on the same straight line in the radial direction.

In addition, as shown in FIG.
Clock pits may be formed as a track group, and pits for discriminating odd-numbered tracks and even-numbered tracks may be provided. In FIG. 7, the pits on the lines A, C, D, and F from the synchronization pits are clock pits, and the lines on the lines B and E are odd-pit and even-track discrimination pits.

Further, the amount of crosstalk from the adjacent track is detected by comparing the level of the RF signal of the clock pit of one track with the level of the RF signal of the clock pit of the adjacent track from the levels held in the sample memories 21a to 21c. This can be used to remove crosstalk. Further, in the case of a disk having a set of three continuous tracks having the first to third clock pits, the selection signal generated from the maximum value detection circuit 25 changes the contents for each track, so that selection signal is used. Tracks can be counted.

[0028]

As described above, according to the optical disk of the present invention, the synchronization pits are located in the same radial direction in the servo field of each track, and on each track in one track group consisting of n tracks. The clock pits do not exist on the same radial straight line, and the clock pits on every nth track are on the same radial straight line. Therefore, since all the pits of the servo field including the clock pits are located on the track, it is not necessary to use a cutting machine equipped with an optical device for wobbling.

Further, in the tracking device of the present invention, when the time corresponding to the distance from the synchronous pit to each clock pit in one track group elapses from the time when the synchronous pit is detected, the reading signal by the reading means is set to n.
2 held by two holding means of n holding means each of which is determined by the holding means that holds the maximum value of the holding signal levels of the n holding means. The difference between the two signal levels, that is, the difference between the black stroke amounts is output as a tracking error signal. Therefore, the tracking error signal can be appropriately generated from the above-mentioned optical disc.

[Brief description of drawings]

FIG. 1 is a diagram showing a recording format of a servo field of an optical disc according to the present invention.

FIG. 2 is a block diagram showing a tracking device according to the present invention.

FIG. 3 is a diagram showing sampling positions before and after a clock pit waveform.

FIG. 4 is a waveform diagram showing the operation of the apparatus of FIG.

5A and 5B are a waveform diagram and a sampling timing diagram of an RF signal when the information reading point is moved.

FIG. 6 is a diagram showing another embodiment of the optical disc according to the present invention.

FIG. 7 is a diagram showing another embodiment of the optical disc according to the present invention.

[Explanation of symbols for main parts]

 11 Pickup 13a, 13b, 13c Clock pit phase detector 16 PLL circuit 17 Timing generator 21a, 21b, 21c Sample memory 22, 23, 24 Subtractor

Claims (2)

[Claims] 1. A servo field having a clock pit for generating a reproduction clock signal and a tracking error signal in addition to a synchronization pit for generating a synchronization signal, and a data recording part for recording data after the servo field. A sampled servo type constant angular velocity type optical disc having a data field and each track,
The sync pits of each track are located in the same radial direction,
1 consisting of a series of n (n is an integer of 3 or more) tracks
In the above track group, the clock pits on each track do not exist on the same straight line in the radial direction, and the clock pits on every nth track are on the same straight line in the radial direction. optical disk. 2. A servo field having a clock pit for generating a reproduction clock signal and a tracking error signal in addition to a sync pit for generating a synchronization signal, and data for recording data after the servo field. A data field is provided for each track, the sync pits of each track are located in the same radial direction, and the clock pits on each track are in the same radial direction in one track group consisting of a series of n tracks. A tracking device for a sampled servo type constant angular velocity type optical disc in which the clock pits on the nth track that do not exist on a straight line are on the same straight line in the radial direction, Reading means for irradiating and reading information recorded as pits on the optical disc; Synchronization detecting means for detecting the time of reading the synchronous pits from the read signal by the taking means, and a distance from the synchronous pits in the one track group to each of the clock pits based on the detection output of the synchronous detecting means. Timing signal generating means for generating timing signals when a corresponding time has elapsed, n holding means for individually holding read signals by the reading means at the time of generation of each of the timing signals, and n holding means. Of the holding signal level of the holding means, the difference between the two signal levels held by the two holding means of the n holding means is determined by the tracking error signal. And a calculating unit that outputs the tracking device.