JPH0323520A - Optical disk device and optical disk - Google Patents

Abstract

PURPOSE:To improve the reliability of track access operation by selecting and outputting the detection result of a first or second cross track number detecting means in accordance with the access speed. CONSTITUTION:At the time of slow track access, the detection signal obtained from the whole of a prescribed bit pattern, which has parts changing in every track and at intervals of plural tracks, for detection of the number of cross tracks is used to detect the number of cross tracks by a first cross track number detecting means 6. At the time of quick track access, the detecting signal obtained from the part changing at intervals of plural tracks out of the prescribed bit pattern for detection of the number of cross tracks is used to detect the number of cross tracks by a second cross track number detecting means 7. Thus, the number of cross tracks is correctly detected to improve the reliability of track access operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical disc device and an optical disc that record and reproduce information using a sample servo type optical disc.

(Prior Art) A sample servo type optical disk has servo patterns 22 intermittently formed on a track 21 formed in a spiral or concentric pattern as shown in FIG.

During recording and reproduction, signals necessary for clock reproduction, tracking, and track access are obtained from the detection signal corresponding to the servo pattern 22.

FIG. 3 shows a known example of the servo pattern 22.
Wobbled bits 31 and 32 arranged left and right with respect to the center of the track 21, and a gray code section 33,
The mirror part 34 and clock bit 35 are set to H. The wobbled bits '31 and 32 are used to obtain tracking signals, the mirror part 34 is used to obtain focus error signals, and the clock bit 35 is used for recording and recording.
This is to generate both clock signals during playback.

The gray code section 33 is a specific code that changes for each track 21 to detect the number of tracks that the light beam crosses (cross track number) when the light beam moves relatively on the optical disk 1 for track access or the like. In this example, 16 types of patterns are set, and the same pattern is repeated every 16 tracks. During track access, the delay code pattern is read from the detection signal corresponding to the Gray code section 33 at each sample timing. For example, if the gray code patterns on tracks A and B of the gray code section 33 are shown in FIGS. 6(a) and (b), the detection signals obtained from the gray code section 33 by the photodetector are as shown in FIG. ), and by binarizing and shaping them using a clock signal, we get the result shown in Fig. 6(e) (
The Gray code pattern is read as shown in r).

By comparing the Gray code pattern read at the current sample timing with the Gray code pattern read at the previous sample timing, it is possible to detect the number of cross tracks between both sample timings as well as track cross direction information. can. For example, the third
When there are 16 types of Gray code patterns as in the example shown in the figure, the number of cross tracks up to 8 tracks can be detected.

In addition, by estimating the relative moving speed of the destination beam with respect to the optical disk from the number of cross tracks and further integrating the number of cross tracks at each zamble timing, it is possible to calculate the total number of cross tracks during access and to By knowing the moving distance, it is possible to perform controls such as switching the track access speed.

In this way, a track access operation is performed based on information such as the number and direction of cross tracks, the relative moving speed of the light beam, and the total number of cross tracks. In general, track access is performed at a high speed at first when the distance to a single marker track is relatively long, and as the vehicle approaches the target track, the speed is decelerated and the access is performed at a low speed.

By the way, when a track is accessed, a detection signal is obtained not only on the track but also from the area between tracks, although the level is low, and since the light beam spot has a certain size, there is a risk of crosstalk from adjacent tracks. effects on the detection signal from each track. Due to the effects of detection signals from the inter-track area and crosstalk from adjacent tracks, the peak position of the detection signal from the Gray code section 33 may shift during high-speed track access, and the clock signal obtained from the clock bit 35 may shift. If the phase is disturbed, the Gray code pattern may be read as a pattern different from the original pattern. The fact that the Gray code section 33 is composed of two bits each as shown in FIG. 3, and that it is necessary to read both of the two bits correctly in order to read the Gray code pattern correctly, also causes such reading errors. This is one of the reasons why it tends to occur.

When the Gray code pattern is read as a pattern different from the length, there are cases where it is read as a pattern that does not exist on the optical disc, and cases where it is read as another pattern on the optical disc. In the former case, no information on the number of cross tracks can be obtained, but in the latter case, a different number of cross tracks than the actual number is plausibly detected.

(Problem to be solved by the invention) As mentioned above, in the conventional method, especially when accessing at high speed,
Due to the influence of detection signals from the inter-track area and crosstalk from adjacent tracks, the Gray code pattern for detecting the number of cross tracks may be read incorrectly.

For this reason, it is difficult to accurately detect the number of cross tracks, and there is a high possibility that the relative moving speed of the light beam and the total number of cross tracks estimated from the number of cross tracks will be incorrect, and the reliability of track access operation will be reduced. The problem was that it was low.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disc device and an optical disc that can accurately detect the number of cross trunks during track access on a sample servo type optical disc.

[Structure of the Invention] (Means for Solving the Problems) The optical disc device of the present invention uses a first detection cross-track number detection means to detect the number of cross tracks for each track and for a plurality of tracks during low-speed track access. The number of cross tracks is detected using a detection signal obtained from the entire specific pit pattern (for example, a gray code pattern) that has a part that changes every time. The number of cross tracks is detected using a detection signal obtained from a portion of a specific pit pattern for detection that changes for each of a plurality of tracks.

Further, in the optical disc of the present invention, the specific pit pattern formed on the track for detecting the number of cross tracks is composed of at least two groups of pits,
The first group has a pattern that changes from track to track (e.g., a Gray code pattern), and the second group has pits formed at the same channel bit position on a track over at least two adjacent tracks, preferably the bit is It is characterized in that other bits on the same track and pits at different positions on adjacent tracks are separated by two or more channel bits.

(Function) During high-speed track access, the number of cross tracks is detected by a detection signal from a portion of a specific pit pattern on a track of an optical disc that changes for each track, that is, a portion where the pattern changes from track to track are relatively small. be done. In this case, although the accuracy of the detected number of cross tracks is low, there is a low possibility that the pattern will be erroneously read even during high-speed track access in which the light beam is relatively moved at high speed.

On the other hand, for low-speed track access, as in the past, detection from a specific pit pattern as a whole (the number of cross tracks is detected by the g signal, but because the light beam moves relatively at low speed, the pattern may be read incorrectly). The number of cross tracks is determined with high accuracy.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an optical disc device according to the present invention, and particularly shows the configuration of a portion related to detection of the number of cross tracks.

In FIG. 1, an optical disk 1 is, for example, a sample servo type optical disk as shown in FIGS. 2 and 3. During recording and reproduction, an optical head 2 irradiates a light beam, and the reflected light is emitted from the optical head 2. is detected by a photodetector to obtain an electrical signal (hereinafter referred to as a detection signal).

The detection signal output from the optical head 2 is input to a clock regeneration circuit 3 and a binarization shaping circuit 5. The clock signal obtained by the clock regeneration circuit 3 is input to a timing generation circuit 4 and a binarization shaping circuit 5.

The clock regeneration circuit 3 extracts a signal corresponding to the clock pit 35 in FIG. 3 from the detection signal, performs waveform shaping, and regenerates a clock signal. The timing generation circuit 4 generates various timing signals necessary for each section in FIG. 1 based on this clock signal.

The binarization shaping circuit 5 binarizes the detection signal, which is an analog signal output from the optical head 2, and further shapes it into a square wave using a clock signal.

FIG. 4 shows an example of the binarization shaping circuit 5, and FIG.
It is a waveform chart of each part of a figure. In FIG. 4, the converter 41 converts the detection signal a shown in FIG. 5(a) into the detection signal a shown in FIG. 5(b).
The signal is binarized as shown in , and a binarized signal b is output. The D-type flip-flop 42 reads the binary signal b at the rising edge of the clock signal C shown in FIG. 5(C), and outputs the signal d shown in FIG. 5(d) from the Q terminal.

The AND circuit 44 sends the output signal d of the flip-flop 52 and the clock signal C to the delay circuit 43 as shown in FIG.
), a delayed clock signal e delayed for a certain period of time is used manually to generate a fifth clock synchronized with the clock signal C.
A binary shaped signal f shown in Figure (r) is output.

The output signal of the binarization shaping circuit 5 is input to first and second cross-track number detection sections 6 and 7 and memories 8 and 9. Consider a case where the servo pattern 22 on the optical disc 1 includes a gray code section 33 as shown in FIG. In this case, the first cross-track number detection unit 6 detects the entire Gray code section 33, that is, the portion that changes for each track (the right bit in the Gray code section 33) 33a, and the portion that changes for each of a plurality of tracks ( gray code part 3
The number of cross tracks is detected by the detection signals from both bits 33b and 33b.

On the other hand, the second cross-track number detecting section detects the number of cross-tracks only based on the portion of the Gray code section 33 that changes for each plurality of tracks, that is, the detection signal from the left bit 33b of the Gray code section 33.

Memories 8 and 9 are cross track number detection units 6 and 7, respectively.
For example, a shift register is used to store and hold the pattern (binarized shaped data) of the detection signal from the Gray code unit 33 at the previous sampling timing, which is necessary for the above.

Note that the memories 8 and 9 may store and hold patterns of all detection signals from the delay code section 33, and in that case, one memory can be shared as the memories 8 and 9. Also, the memory 9 has the right bit 33b of the Gray code section 33.
The pattern of the detection signal may be stored and held.

The selector 10 selects the detection result of the cross-track number detection section 6 during low-speed track access, and selects the detection result of the second cross-track number detection section 7 during high-speed track access, according to an access mode switching signal for switching the track access mode. The results are selected and the final cross-track detection signal 11 is output.

The error detection circuit 12 is for detecting errors in the Gray code pattern in the output signal of the binarization shaping circuit 5.
For example, Fig. 6(e)(r) which is a gray code pattern.
Errors are detected by storing in advance t6 types of patterns of pulse pairs as shown in , and comparing these with the detected Gray code pattern. Detected Gray code pattern force <. tc! If it does not match any of the detected Gray code patterns, it is assumed that the detected Gray code pattern is incorrect and the error detection signal 13 is output.

Cross track number detection signal 11 and error detection signal 13
is supplied to a track access control circuit (not shown).

'7J1 and the second cross-track number detection units 6, 7 detect the pattern of the detection signal from the entire Gray code unit 33, the pattern of the detection signal from only the left bit 33a, and the patterns stored in the memories 8, 9, respectively. The number of cross tracks is detected by comparing the pattern with the existing pattern. Here, the third
As shown in the figure, since the bit 33b on the right side of the gray code section 33 changes for each track, the first cross track number detection section 6 can identify the track 21 for each track. Since the bit 33a changes every 4 tracks, the second cross track number detection section 7 changes every 4 tracks.
Tracks 21 can only be identified for each track.

For example, a certain consecutive sample timing SX, Sx+1
．． "x+2'" At x+3, it is assumed that in the actual song, the light beam moves relatively on the optical disc 1 as shown in tracks A→C→F→I in FIG. At this time, if we pay attention to the bit 33a on the left side of the gray code section 33, since the bit 33a is at the same position in track A and 1/rack C, the light beam will be transmitted to tracks -3 to +3 during the sample timing S -Sx+1X. It is expected that progress will be made. Note that the light beam jumps over, for example, 16 Gray code patterns at once, and the light beam becomes +13 to +1.
It can be considered that 9 tracks, or -13 to -19 tracks have progressed, and considering the maximum speed at which the movable part can move from the mass, maximum acceleration, friction, maximum acceleration time, etc. of the movable part of the optical head 2, Although these possibilities can be determined, the specifications of the Gray code unit 33 are generally set so that such things will not occur, so such things are not considered.

Next, in track F at sample timing Sx+2, bit 33a is located at a different position than the sample timing at S and Sx+1, so it is thought that the light beam has advanced 1 to 7 tracks between sample timings Sx+1 and Sx+2. It will be done. The same holds true for sample timings Sx+2 to Sx+3.

The second cross-track number detection unit 7 calculates the number of cross-tracks between sample timings as follows based on this information. First, the average value of the number of possible cross tracks is associated with each pattern (position) change of the left bit 33a of the Gray code section 33.

For example, if the same pattern of bits 33a are detected consecutively by the first cross-track number detection unit 7, 0 track, which is the average value of the possible cross-track numbers -3 to +3, is set as the cross-track number. , or one or two tracks in the track access direction is set as the number of cross tracks in consideration of the fact that high-speed track access is in progress. Also, if the pattern of the pit 33a changes to an adjacent pattern (for example, from a pattern on track A-D to a pattern on track E-H or a pattern on track M-P
(If the pattern changes to the above pattern), set +4 or -4 tracks as the number of cross tracks.

During high-speed track access, the number of cross tracks estimated at each sample timing, which is determined by the second cross track number detection section 6, is sent to the track access control circuit via the selector 10 as a cross track number detection signal 11.
It is considered a person as a person. The track access control circuit adds the number of cross tracks determined by the second cross track number detection section 6 to determine the current approximate relative position of the light beam with respect to the optical disc 1. Furthermore, it is also possible to know the relative moving speed of the light beam with respect to the optical disc 1 from the number of cross tracks between sample timings, and to generate a feedback signal for controlling the access speed.

The track access control circuit performs high-speed track access using the thus obtained relative position and relative velocity information. The cross track number detection signal 11 used during this high-speed track access is transmitted to the Gray code section 33.
This is obtained only from the left bit 33a, which has a small change from one time to the next. Therefore, even during high-speed track access, the right pit 33b changes for each track.
As in the conventional technique in which a cross-track number detection signal is obtained using a detection signal obtained from the entire Gray code section 33 including
The number of detected cross tracks does not vary greatly.

Then, when the light beam approaches the target track due to high speed track access, the track access operation is switched to low speed mode. During this low-speed track access, the gray code 3 is detected by the first cross track number detection unit 6.
The number of cross tracks detected based on the detection signals obtained from the entire track access control circuit 3 is input to the track access control circuit via the selector 10 as a number of cross track detection signals 11.

During this low-speed track access, since the light beam moves at a low speed over the previous disk 1, the first cross-track number detection circuit 6 detects the number of cross-tracks using the detection signal from the entire gray code section 33. The number of cross tracks can be accurately detected on a track-by-track basis without erroneously reading the code pattern. Therefore, the track access control circuit, based on the cross-track number detected by the first cross-track number detection circuit 6,
A final retraction operation of the light beam to the target track can be performed.

Incidentally, in the above embodiment, the case where the servo pattern 22 on the optical disk is a pattern as shown in FIG. 3 has been described, but the present invention is not limited to this, and other patterns may be used. FIG. 7 shows only the Gray code section 50 of the servo pattern, and the Gray code pattern on each track 21 is
3 pits 51. , 52.53.

Of these three bits 51, 52.53, the center and rightmost bits 51.52 belong to the first group, and the leftmost bit 53 belongs to the second group. Here, the bits 51 and 52 constituting the first group have a pattern that changes for each track.

On the other hand, the bits 53 constituting the second group are formed at the same channel bit position on at least two adjacent tracks (eight tracks in the illustrated example). Furthermore, this bit 53 is separated by two or more channel bits from other bits 51 on the same track and from bits 53' located at different positions on adjacent tracks.

As in the present invention, when the second cross-track number detection unit 7 detects the number of cross-tracks using only the detection signal obtained from the portion that changes for each of a plurality of tracks during high-speed track access, the number of cross-tracks is detected in the inter-track area. A certain level drop or peak shift of the detection signal occurs. Therefore,
In the pattern of the Gray code section 33 as shown in FIG. 3, the left bit 33a may be mistaken for a bit on another track.

On the other hand, according to the example shown in FIG. 7, bit 53 is separated by two or more channel bits from other pits 51 on the same track and from bits 53' at different positions on adjacent tracks, so due to peak shift etc. Bit 53 is 1
Even if the bit 63 is read as a position separated by a channel bit, the position of the bit 63 can be accurately known. Therefore, the reliability of detecting the number of cross tracks can be further improved.

[Effects of the Invention] According to the present invention, it is possible to correctly detect the number of cross tracks even during high-speed track access in a sample servo type optical disc, and the reliability of track access operation can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical disk device according to the present invention, FIG. 2 is a plan view schematically showing an optical disk using a sample servo method, and FIG. 3 is a servo pattern on a conventional optical disk using a sample servo method. Figure 4 showing an example of
The figure shows a specific example of the binarization shaping circuit in FIG.
FIG. 5 is a timing diagram for explaining the operation of FIG. 4,
FIG. 6 is a diagram showing the pattern of the Gray code section on two adjacent tracks in FIG. 3, the detection signal from the Gray code section, and the binarized shaped waveform, and FIG. 7 is a diagram showing a preferred embodiment of the optical disc according to the present invention. FIG. 3 is a diagram showing a Gray code pattern for explaining an example. 1... Optical disk, 2... Optical head, 3... Clothball reproduction circuit, 4... Timing generation circuit, 5...
Binarization shaping circuit, 6.7... First and second cross track number detection section, 8, 9... Memory, 10.
- Selector (selection means), 11... Cross trunk number detection signal, 12... Error detection signal, 21... Track, 22... Servo pattern, 31, 32... Wobbled bit, 33.50 ...Gray code department, 33a
, 33b, 51 ~ 53-... Pit of Gray code part, 34... Part of Mira, 35... Chronok pit.

Claims (3)

[Claims] (1) An optical disc that records and reproduces information by irradiating a light beam onto an optical disc on which a predetermined servo pattern is formed, including a specific pit pattern that has a portion that changes for each track or for each multiple tracks. In the apparatus, first cross-track number detection means detects the number of cross-tracks when a light beam moves relatively on the optical disk using a detection signal obtained from the specific pit pattern; and the specific pit pattern. a second cross-track number detection means for detecting the number of cross-tracks using a detection signal obtained from a portion that changes for each of a plurality of tracks; 1. An optical disc device comprising: selection means for selecting and outputting the detection results of the number detection means. (2) In an optical disc in which a predetermined servo pattern including a specific pit pattern is formed on a track, the specific pit pattern is composed of at least two groups of pits, and the first group changes for each track. 1. An optical disc having a pattern, wherein the second group has pits formed at the same channel bit positions on the tracks over at least two adjacent tracks. (3) The optical disc according to claim 1, wherein the pit is separated by at least two channel bits from other pits on the same track and pits at different positions on adjacent tracks.