JPH02172021A - Optical disk - Google Patents

Abstract

PURPOSE:To attain sure high speed access by parting the interval of pits formed on a track at least by 2-channel pits. CONSTITUTION:Tracks A-P are expressed in total 16 kinds of gray code patterns and two pits 2, 3 are formed in one track. Moreover, the two pits 2, 3 are parted over two channel pits without fail. Thus, 12-channel pits are used for a gray code part 1. Thus, the pit strings comprising the pits in such a way is detected as a binarized signal and the track on which the pit string is located is recognized to attain sure high speed access.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to optical discs.

(Prior Art) Generally, in an optical disc, the following three types of control are basically required when writing and reading information.

(1) Tracking control: Control that causes the spot of a light beam for writing and reading information to follow a predetermined track.

(21M readout timing control; control to match the rotation of the optical disc with the readout timing.

(3) Focusing control; control to align the focal position of the optical disc (focus of the objective lens) with the recording surface of the optical disc.

In order to perform these controls, it is necessary to generate error signals corresponding to each. A sample servo method has been proposed as one method for obtaining these error signals. As shown in FIG. 6, data bytes 13, which are information recording areas, and servo bytes 14, which store servo information for discrete control, are alternately formed on tracks 12 of an optical disk 11, and information is written and When reading, the servo information for the above control is stored in the servo byte 14.
This is a method to read from. A set of one data byte 13 and servo byte 14 is called a segment 15, and a predetermined number of segments 15 are arranged on the track 12 at equal intervals. The format of an optical disc in which servo information is recorded discretely in advance in this way is called a sample servo format, and is formed in a spiral or concentric shape on the optical disc.

FIG. 7 is an enlarged view of the servo cutting tool 14. As shown in this figure, the servo bite 14 within one segment has two wobbled pits 15a and 15b.

It consists of one clock pit 16, a mirror portion 17 in which no information is stored, and a gray code portion 18 consisting of a plurality of recording signals.

As shown in the figure, the wobbled pits 15a and 15b are
Track center line 19 on both sides of track center 1s19
They are formed at the same distance from each other and at regular intervals. When a pickup (not shown here) that irradiates a light beam spot moves on the track due to the rotation of the optical disk, these two wobbled pits 15
a, 15b and detect the reflected light with an optical sensor,
get the output. Then, a control signal is generated so that the difference in output becomes zero, that is, so that the light beam spot moves accurately on the track center line 19. Tsumashiwoprud・
The pits 15a and 15b are for performing the tracking control.

As shown, the clock pit 16 is located at the center of the track @
One is formed on 19. The light beam spot detects this clock pit 16, thereby providing timing for accessing the data byte 13, allowing accurate reading of information. In other words, the clock pit 16 is used to control the read timing.

As shown in the figure, the mirror portion 17 has a certain area on the track that has no pits at all, and has a mirror surface that reflects light. When the light beam spot passes through this mirror portion 17, it returns as reflected light, and this reflected light is detected by an optical sensor. If the reflected light is focused on the optical sensor via a cylindrical lens, for example, when the distance between the optical sensor and the mirror part 17 changes, the focal length of the cylindrical lens will also change, so the reflected light that is focused on the optical sensor will be reduced. The overall shape of changes.

If the state of this change is obtained as an output difference, it becomes possible to control the distance between the optical sensor and the mirror part 17 to always be kept constant.

In other words, the mirror portion 17 is for performing the focusing control.

As shown, the gray code section 18 has two pits 20a and 20b within a certain area on the track.
It has a pit row consisting of. The positions of these two pits are different for each track, and here
The 6fi pattern is repeated. This gray code section 18 detects the position of the pickup during high-speed access to the target track (access at such a speed that the number of cross tracks cannot be determined from the increase or decrease of the tracking signal due to the sampling frequency). It is for the purpose of Then, during high-speed access, this pattern is read sequentially and compared with the previously sampled pattern.
It is possible to detect the cross-track direction and number of cross-tracks up to the track.

The procedure for reading this gray coat portion 18 will be described. 7th
The gray coat part of track A and track B in the figure is
The output from the gray coat section 18 is shown in the figure (
(b) and (C) of the same figure show the binarized and formatted output of this output. The control guide inside the optical disk device includes the eighth
A total of 16 types of binarized patterns of pit strings as shown in FIG. 3(C) are stored in advance, and the detected patterns and the stored patterns are compared. For example, since the pattern is stored in advance, the position of the pickup is detected, and the number of cross tracks is detected in the next layer. Here, the number of cross tracks from track A to track B is 1.
It is determined that In this way, if the same signal as the binarized pattern of the 16 types of pit rows can be obtained, the accurate pickup position and the number of cross tracks can be detected. By making the spot of the light beam irradiated onto the disk surface a certain size, it is possible to obtain a signal like that shown in Figure 8(b) even between tracks, although the output level is low. It is. However, when doing this, the 8th track was affected by the pits of both trucks.
Composite pattern outputs such as those shown in Figures (b) and (C) may occur. When this pattern is obtained, it is determined that a reading error has occurred since it is not a pattern that can be used to detect the position of the pickup, and the number of cross tracks is not detected. Therefore, similar operations are performed many times until one pattern is obtained.

In order to avoid this, there is a method of using, for example, a composite ratio cover turn of the pits of both trucks to detect the position of the pickup. However, even if this method is used, the following problems occur. Now, as shown in Figure 9, the disk output Qa-b is 2
If the signal spans two channel pits, a signal between tracks can be obtained as described above, but the peak of the disc output a-1) may be read narrowly as shown in (a) in the same figure. If this happens, either one of the pulses will be output as shown in FIG. 6(b), or no pulse will be output at all. A further problem is when performing high-speed access, for example, when several samples are passed between each track.
Suppose that between tracks A and B, Qa-b shown in FIG. 9(b)
When l and Qa-62 are output alternately, even though the pickup is actually moving in one direction, it is detected as if the direction of movement is changing minutely, so it can be accurately detected. It is impossible to know the movement of the pickup.

(Problems to be Solved by the Invention) As described above, in order to detect the intersection between a pickup and a truck during high-speed access, conventional techniques have been used to detect the intersection of a pickup and a truck by using a binary dead cover turn in a Gray code part or by combining adjacent Gray code parts. A method was used in which the binary output pattern was memorized and compared with the actual pattern. However, even with this method, accurate high-speed access may not be possible in some cases. The present invention solves these problems and
The purpose is to provide an optical disc that enables reliable high-speed access.

[Structure of the invention] (Means for solving the problem) In order to achieve the above object, the present invention includes (i)
In an optical disc in which position control is performed by recognizing a track in which a pit string is located by detecting a pit string consisting of a plurality of pits formed on a track as a binary signal, the distance between the pits is determined at least The two channel pits were separated. In addition, ■In optical discs where position control is performed by detecting a pit string consisting of a plurality of pits formed on a track as a binary signal to recognize the track in which the pit string is located, The pits in the composite pit row formed by combining the pit rows were set to be at least two channel pits apart.

(Function) By performing K as in (2), even if the disk output on the track is narrowly read, an erroneous binary signal will not be generated. Moreover, by doing as shown in (3), even when using a combination of pit rows, an erroneous binarized signal is similarly prevented from being generated. Therefore, an optical disc that enables reliable high-speed access is provided.

(Example) The present invention will be explained below with reference to the drawings.

FIG. 1 is a diagram showing an example of a Gray code pattern used in the present invention. Tracks A to P are represented by a total of 16 types of gray code patterns, and two pits 2.3 are formed in one track. Further, here, these two pits 2.3 are always formed at least two channel pits apart. By doing this, 12 channel pits are used in the gray code section 1 in this embodiment.

FIG. 2 is a diagram showing a composite pattern of adjacent Gray code patterns of FIG. 1.

For example, if the spot of the light beam passes between tracks A and B in FIG. 1, a pattern such as tracks AB in FIG. 1A2 will be read.

As shown in Figure 1 for Trucks A and B, the position of pit 2.4, which is the 1st channel pit of the two pits, remains unchanged, and pit 3, which is the 9th channel pit of Truck A, is the 6th channel pit of Truck B. The position has been changed to the pit eye. Since these pits 2 and 3.5 are separated by two or more channel pits, the pulse output positions in this track A-B are all separated by two or more channel pits.

Figure 3 shows the disc output of tracks A-B and tracks B-C. The level of disk output is low, but
) Since there are no pits in the matching channel pits, pit interference does not occur. Therefore, even between tracks, when binarization is performed, pit positions will not shift or two pits will not become one. Furthermore, in this embodiment, since all 16 types of track-to-track patterns are different, a total of 32 types of patterns can be obtained, and the pickup position can be determined more accurately.

Further, according to this embodiment, the following effects are also produced. In general, during high-speed access in which several tracks are advanced in one sample period, the signal processing time required to read and judge all the Gray code patterns in FIG. 1 may become a problem. In this pattern, 14 out of 16 tracks have
There is a pit at the 1st channel pit or the 12th channel pit, so by reading only this,
The number of cross tracks can be quickly counted every about 8 tracks.

FIG. 4 is a diagram showing a second embodiment of the present invention. In this embodiment as well, there are two pits on one track, and a total of 16 types of pit patterns are set. The patterns read between tracks are always separated by two or more channel pits, as shown in FIG. 5, and the patterns are all different as in the first embodiment. Therefore,
Even between tracks, when binarization is performed, pit positions do not shift or two pits become one.

In addition, in this embodiment, the pit pattern is more regular than in the first embodiment, and the number of channel pits in the entire gray code section is large, so that when a human checks the pattern displayed on paper, it is difficult to check. easy to do,
Convenient to handle.

In the above embodiments, the pit pattern is of the 16m type, but it is of course possible to use a pit pattern for detecting the number of cross tracks having a pit pattern other than this. Furthermore, these pit patterns do not need to be changed for each track; for example, by arranging two of the same pit patterns adjacent to each other on 16 tracks, a total of eight types of pit patterns can be formed. You can also do that. Of course, three or more pit patterns with the same pit pattern may be placed adjacent to each other. By doing so, in an optical disk device that performs high-speed access such as passing through several tracks with one sample, there is no need to use a variety of pit patterns, and control becomes easy.

〔Effect of the invention〕

As described above, according to the present invention, an optical disc that enables reliable high-speed access is realized.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the gray code pattern of the optical disc according to the first embodiment of the present invention, FIG. 3 is a diagram showing how the output signal is binarized and shaped according to the present invention, and FIG. Figures 5 through 5 are diagrams showing the gray code pattern of an optical disc according to the second embodiment of the present invention, Figure 6 is a diagram showing a sample servo type optical disc, and Figure 7 is a diagram showing the pit arrangement of a general servo bite. FIG. 8 is a diagram showing the pit arrangement of the Gray code section and its binary signal, and FIG. 9 is a diagram showing a case where the binary shaping of the output signal is inappropriate. 1... Gray code section, 5... Pit,... Optical disk, 4... Servo information area.

Claims (2)

[Claims] (1) In an optical disc in which position control is performed by recognizing a track in which a pit row is located by detecting a pit row consisting of a plurality of pits formed on a track as a binary signal, An optical disc characterized in that the interval is at least two channel pits apart. (2) In an optical disc in which position control is performed by recognizing a track in which a pit string is located by detecting a pit string consisting of a plurality of pits formed on a track as a binary signal, on the adjacent tracks. An optical disc characterized in that the pits in a composite pit row formed by combining the pit rows are at least two channel pits apart.