JP2772034B2 - Optical disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to an optical disc device.

(Prior Art) Recently, a so-called sample servo type optical disk apparatus has been developed which uses an optical disk in which information for obtaining a servo signal is recorded in a predetermined position in a concentric or spiral track direction in advance. ing.

FIG. 4 shows an outline of this type of sample servo type optical disk. In the figure, 1 is a track, 2 is a data area for recording or reproducing an information signal, and 3 is a servo area in which information for obtaining a servo signal is recorded in advance.

FIG. 5 is an enlarged view of a part of FIG. 4. The servo area 3 includes a clock pit 4 for obtaining a timing for writing and reading a signal, and a wobble for obtaining a tracking signal. It comprises a dot 5, a mirror unit 6 for obtaining a focus signal, and a part generally called a gray code pattern 7 for detecting a relative movement between the optical head and the track 1.

The gray code pattern 7 is used when the frequency at which the optical head crosses the track exceeds half the sampling frequency for obtaining the tracking signal, and when the correct cross track number cannot be known by the tracking signal, This is for detecting the relative speed between the head and the track.

FIG. 6 shows an example of a conventional gray code pattern 7. In this example, 16 patterns A to P are set, and the same pattern is repeated every 16 tracks.

On the other hand, a circuit for detecting the gray code pattern 7 is configured as shown in FIG.

In FIG. 7, a reflected signal 8 from the optical disk is converted into binary data 10 by a waveform shaper 9 and guided to a clock regenerator 11, where a clock signal is generated based on a clock pit portion of the binary data 10. 12 is played. Also,
Timing generator 13 based on recovered clock signal 12
Are the various timing signals necessary for the operation of this system.
Generate. On the other hand, the binarized data 10 created by the waveform shaper 9 is input to the first shift register 15, and the data of the gray code pattern 7 in FIG. 6 is captured.

The gray code data 16 thus obtained is transferred from the first shift register 15 to the second shift register 17 for each sample.
The number of cross tracks 20 and the movement direction 21 between one sample are output by comparing the patterns of the shift register outputs 16 and 19 in the cross track number detection unit 18.

Next, data capture of the above-described gray code pattern 7 will be described with reference to FIG.

In the figure, e and i are reflection signals from the optical disk when it is assumed that the optical head has passed on track E at one sample point and on track I at the next sample point. These are binarized by the waveform shaper 9 into Qe and Qi. Here, Qe and Qi are
8B, the gray code Ge, Gi is obtained as the output Gpe, Gpi of the first shift register 15 and the second shift register 17 as shown in FIG. 8B. This gray code Gpe (0010,1000), Gpi (0100,
0001) is compared by the cross-track number detecting section 18 based on the relationship shown in FIG.

Here, the clock signal 12 from the clock regenerator 11 on which the operation of the timing generator 13 is based includes signal phase fluctuations due to various factors such as a disk defect and mechanical vibration commonly called jitter. . When the amount of jitter exceeds 1/2 of the clock signal period, data cannot be accurately reproduced. This effect will be further described with reference to FIG.

First, referring to the time chart shown in FIG. 9, Qi is the waveform shaper 9 that calculates the reflection signal from the optical disk 7 assuming that the optical head has passed the track I at a certain sample point in the same manner as described above. This is a quantified signal. Further, it is assumed that the gray code sample signal S when the gray code on the track I is sampled contains jitter, and this is indicated as S '. The gray code Gi 'sampled by S' is transferred to a first shift register.
The output Gpi 'of 15 is obtained as shown in the figure.

In such a case, the output gray code Gpi ′ (000
1,1000) is determined by the cross-track number detection unit 18 to be a pattern on the track P even though it is on the track I. As a result, the number of cross tracks 20 and the moving direction 21 are erroneously output as 5, minus (−), and accurate position and speed detection may not be performed.

(Problems to be Solved by the Invention) As described above, in the conventional optical disk device, when detecting a relative movement between a light spot and a gray code during a high-speed seek operation, it is necessary to accurately detect the gray code. There was a problem that can not be.

Accordingly, an object of the present invention is to provide an optical disc apparatus capable of accurately detecting the relative movement between a light spot and a gray code during a seek operation at high speed even when jitter occurs.

[Structure of the Invention] (Means for Solving the Problems) An optical disk device of the present invention for solving the above problems has concentric or spiral tracks, and stores servo information intermittently provided on these tracks. In addition to positioning the optical head based on the pit pattern, a pit pattern that can be distinguished from that provided on another track by pit arrangement in the servo information is provided in such a manner that the same pit pattern appears for each of a plurality of tracks. As a reference, a gray code determined according to each pit pattern is detected based on a pit detection signal appearing in a channel bit of a predetermined minute period, and a gray code detected last time and a gray code detected this time are compared, so that a track is detected. Detects the number of crossings and the relative moving speed or moving direction of the optical spot with the optical disc. In the optical disk device, the pit pattern defining the gray code is defined by a pit device written on a pid writing line separated by at least three channel bits, and the circuit for detecting the gray code includes a detection value of each channel bit. And an OR circuit for inputting the output of the shift register for three channel bits including the channel bits corresponding to each pit writing line and the channel bits on both ends thereof, and ORing these three inputs and outputting the result. It is characterized by having it.

Further, in the above optical disk, it is preferable that the pit pattern defining the gray coat is such that the presence or absence of one pit is inverted with respect to adjacent tracks.

(Operation) In the present invention, the pit pattern defining the gray code is defined by a pit arrangement written on a pit writing line separated by at least three channel bits, and the circuit for detecting the gray code determines the detected value of each channel bit. A shift register for shifting, and an OR circuit for inputting three channel bits including an output of the shift register, including a channel bit corresponding to each pit writing line and both end channel bits, and ORing these three inputs and outputting the result. Have.

Therefore, even if the detection of the pit pattern is separated by one channel bit due to the jitter, the pit pattern can be corrected on a predetermined pit writing line, so that it is not mistaken for other pit patterns.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows a gray code pattern of the optical disk device according to the present invention.

In the figure, A to P are tracks, each of which is composed of 16 different patterns repeated. Further, a to l are channel bits measured by a predetermined timing signal with reference to the clock pit 4 shown in the conventional example.

The gray code pattern in this example is composed of channel bits b,
Each pit pattern is defined differently from other pit patterns by pits written on pit writing lines corresponding to e, h, and k. A pattern group consisting of these 16 pit patterns A to P is formed on an optical disk. Appear repeatedly in the radial direction.

The intervals between the pit writing lines are all three channel bits apart in this example.

Further, the pit pattern of this example is in a mode in which the presence / absence of only one pit is inverted with respect to the pit patterns of adjacent tracks. This is a fast seek
Even if an adjacent pit is erroneously detected, the adjacent pit is determined to be an adjacent track, and the error is limited to a maximum of one track.

FIG. 2 shows a circuit configuration for detecting the gray code pattern.

In the figure, the binarized data 30 after waveform shaping is taken into a shift register 32 with a gray code sample signal 31,
As a result, pattern data 33 of 12 channel bits is obtained. In this case, the information channel bits b, e, h, k among the 12 channel bits corresponding to al in FIG.
, And OR circuits 34 to 37 take a logical sum of three channel bits obtained by adding one channel bit on each side of the OR circuit.

In other words, the configuration is such that the OR circuit 34 takes the OR of the channel bits a to c around the information channel bit b and the OR circuit 35 of the d to f around the information channel bit e. In addition, g to g around the information channel bit h
i is ORed by an OR circuit 36, and j to l around the information channel bit k are ORed by an OR circuit 37. As a result, as will be described later, channel bits b, e, h, k
The gray code 38 of bits can be obtained accurately.

Next, the operation of the above embodiment, particularly the operation when jitter occurs, will be described with reference to FIG.

First, for example, as shown in FIG.
When trying to sample the upper pattern, the data 39 obtained by binarizing the pattern on the track J is taken into the shift register 32 as a gray code sample signal 40. Here, it is assumed that jitter occurs such that the jitter amount exceeds 1/2 clock cycle, and the phase of the gray code sample signal 40 is irregularly shifted as indicated by 41. Due to this phase shift, the output of the shift register 32 changes from the original output 42 to 43
To gray code channel bits b, e, h, k
Will also change. That is, the gray code is shown in FIG.
As shown in the figure, 44 (010,010,000,010) to 45 (100,01
0,000,001), specifically the channel bit
b, e, h, k are shifted to a, e, h, l.

In this case, as described with reference to FIG. 1, since adjacent pits are separated by at least three channel bits in the track direction, channel bits 12 adjacent to the gray code channel bits b, e, h, and k are used. Is not included in the information pattern. Therefore, channel bits b,
Since three channel bits obtained by adding the channel bits on both sides of e, h, and k are ORed, even if the output of the shift register 32 changes due to jitter, the original value can be easily obtained. Channel bits b, e, h, k
Can be restored.

As described above, according to the present embodiment, pits adjacent in the track direction are formed at least three channel bits apart, and a channel bit including information in this pattern and a channel bit not including information on both sides of each channel bit are included. Since the logical sum is obtained, the original Gray code can be accurately restored even if the reproduced clock signal includes jitter of 1/2 clock cycle or more. Therefore, since the gray code can be accurately read, the relative movement between the light spot and the gray code during the seek operation at high speed can be accurately detected.

Further, in this example, as shown in FIG. 1, the gray code pattern has a mode in which the presence or absence of only one pit is inverted with respect to the pit pattern adjacent to each other. Even if a pit of a track is detected, no deviation of one or more tracks occurs.

In the above embodiment, the interval on the bit line is 3
Although the channel bits have been described, this may be a number greater than four, or a different spacing for each entry line.

The present invention is not limited to the above embodiments, but can be implemented in an appropriate mode by making appropriate design changes.

[Effects of the Invention] As described above, since the present invention is an optical disk device as described in the claims, even if jitter occurs, the relative position of the light spot and the gray code during a high-speed seek operation is high. Movement can be detected accurately.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing an example of a track access servo pattern of an optical disk device according to the present invention.
FIG. 3 is a circuit diagram showing a gray code pattern detection method, FIG. 3A is a time chart showing the operation of the example of FIG.
FIG. 3 (b) is an explanatory view showing a state in which channel bit data is shifted due to jitter, FIG. 4 is a view schematically showing an example of a sample servo type optical disk, and FIG. 5 is a view showing a part of the optical disk. FIG. 6 is an explanatory view schematically showing an example of a conventional gray code pattern, FIG. 7 is a block diagram showing an example of a cross track number detecting device, and FIGS. 8 (a) and (b). 9) is a time chart showing a conventional example of detecting a gray code pattern, and FIG. 9 is a time chart showing an operation when the conventional jitter amount exceeds 1/2 clock cycle. 32 shift register, 34-37 ... OR circuit AP: track al: channel bits b, e, h, k ... information channel bits 30 ... binarized data 31 ... gray code sample signal 33 ... 12 channel bits Pattern data 38 ... Gray code

Claims (2)

(57) [Claims] An optical head is positioned based on servo information provided intermittently on these tracks, and other tracks are arranged by pit arrangement in the servo information. A pit pattern that can be distinguished from the pit pattern provided in each of a plurality of tracks is provided in such a manner that the same pit pattern appears in each of a plurality of tracks. By detecting the gray code determined according to the pattern and comparing the previously detected gray code with the currently detected gray code, the number of track crossings and the relative moving speed or moving direction of the optical disk and the optical spot are detected. In an optical disc device, a pit pattern that defines the gray code is The circuit for detecting the gray code is defined by a pit device written on a pid writing line separated by at least three channel bits, and a circuit for shifting the detected value of each channel bit is provided. An optical disk device having an OR circuit for inputting three channel bits including a channel bit corresponding to a pit writing line and both-end channel bits, and ORing the three inputs and outputting. 2. The optical disk device according to claim 1, wherein the pit pattern defining the gray coat is such that the presence or absence of one pit is inverted with respect to adjacent tracks. Optical disk device.