JPH02203438A - Optical disk - Google Patents

Abstract

PURPOSE:To decrease the count number of pregrooves and to shorten the access time by providing pilot grooves formed with the one-round component of the pregrooves to a prescribed depth in the positions of every predetermined number of unit tracks. CONSTITUTION:Recording surfaces 7 and the pregrooves 6 are alternately provided on the tracks of a substrate 2. The pilot grooves 8 formed with the one- round component of the pregrooves 6 to the prescribed depth are provided in the positions of every predetermined number of the unit tracks. Namely, as the pilot grooves 8 are provided, when an optical head accesses the pregrooves 6 in the direction perpendicular thereto, the pilot grooves are detected at the amplitude different from the amplitude of the other pregrooves from the relation between the depth of the grooves and the track error signal. The positions of the pilot grooves 8 are thus detected. The need for counting every group to be jumped is eliminated in this way. The count number of the grooves is thus decreased and the access time is shortened.

Description

[Detailed Description of the Invention] [Summary] An object of the present invention is to provide an optical disc used in an optical disc device for recording information, which can reduce access time by reducing the number of pregroove counts. In an optical disc having a recording surface and a pregroove alternately on the tracks of a substrate, a pilot in which one round of the pregroove corresponding to the track is formed at a specific depth at a position for each predetermined number of unit tracks. A groove is provided, and when the optical head accesses the optical disk,
Configure it for quick access.

[Industrial application field]

The present invention relates to an optical disc used in an optical disc device for recording information.

Optical recording and reproducing devices are a field in which the market is rapidly expanding from recording and reproducing image information to devices that can record computer codes due to their features such as mass storage, non-contact recording, and exchangeable media. be.

[Conventional technology]

FIG. 5 is a diagram showing the structure of a conventional optical disc.
In the figure (bl is an enlarged cross-sectional view of part A in Figure 5(a)), the reference symbol is an optical disc, which is composed of the following parts. 2 is a member made of glass or plastic, etc. 3 is a protective film,
4 is a recording layer, and 5 is a protective film. Further, a guide groove (pregroove) 6 for track servo is spirally carved in the substrate 2 from the center toward the outside.

For example, in the case of an optical disc having a diameter of 30 cm, the number of these 60 pregrooves is approximately 54,000 at a pitch of 1.6. When the optical head accesses from the current track on the optical disk to the target track to be moved, an electric signal is obtained by photoelectrically converting the change in the amount of light due to the pregroove 6 traversed by the known bush pull method, that is, a track error signal. (Track erro
The target track is found while counting the number of tracks (groups; grooves) to jump from r Stgnal (hereinafter abbreviated as TES).

FIG. 6 is a diagram showing a TBS using a conventional optical disc. In this waveform diagram, the horizontal axis is the position (travel distance), and the vertical axis is the amplitude (
voltage). The signal waveform corresponding to the moving distance detected by crossing the pregroove maintains a constant amplitude, and the number of pregrooves (number of tracks) can be determined by counting the number of peaks of this waveform.

[Problem to be solved by the invention]

In the conventional optical disc 1, as described above, when the optical head attempts to access a track on the optical disc, it is necessary to count all the groups to jump, and the counting operation takes time to access. There was a point.

The present invention has been made in view of the above-mentioned conventional problems.
An object of the present invention is to provide an optical disc capable of shortening access time by reducing the number of group counts.

[Means to solve the problem]

FIG. 1 is a diagram showing the structure of the present invention. In an optical disc 1 having a recording surface 7 and a pregroove 6 alternately on the tracks of a substrate 2, one circumference of the pregroove corresponding to the track is placed at a predetermined position for each unit track number to a specific depth. A pilot groove 8 is provided,
When the optical head accesses the optical disk 1, it is configured to be able to access at high speed. Specifically, the position for each unit track number determined in advance is divided into the number of tracks for long-distance access and the number of tracks for medium-distance access. A main pilot groove 9 and a sub-pilot groove 10 are divided into a number of sections, and one round of the pregroove corresponding to the track of each section is formed at specific different depths.
It consists of an optical disc equipped with

[For production]

When the optical head containing the focus servo accesses the pregroove 6 in a direction perpendicular to it, the TBS obtained as shown in the principle diagram of FIG. 3 is a predetermined number of unit tracks (for example, several hundred tracks) La Since a pilot groove 8 is provided at each position with a specific depth corresponding to one circumference of the pre-groove corresponding to the track, the second
From the relationship between the depth of the groove and the amplitude of the TES shown in the figure, the detected amplitude is different from the amplitude in other pregrooves.

Therefore, the position of the biloft group 8 can be detected by a comparator (not shown) that compares it with a required threshold value Va.

Further, as shown in FIG. 4, as an application example, the predetermined number of unit tracks is divided into Lm, the number of tracks for long-distance access (for example, several thousand tracks), and Ls, the number of tracks for medium-distance access (for example, several hundred tracks), By providing the main pilot groove 9 and the sub-pilot groove 10, each of which is formed at a specific different depth for one round of the pre-groove corresponding to each number of sections, TBS exceeding the threshold values Vb and Vc, respectively, can be obtained. Therefore, the vicinity of the target track position can be detected at higher speed using the above-mentioned principle.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Note that, in order to make the explanation of the configuration and operation easier to understand, the same parts are given the same reference numerals throughout all the figures, and repeated explanation thereof will be omitted.

FIG. 1 is a diagram showing the structure of the present invention, and FIG. 1(a)
1(b) is an enlarged sectional view of section B in FIG. 1(a). In both figures,
Reference numeral 8 indicates a biloft group, which is formed deeper than the pregroove 6 in this example.

The formation location will be described later with reference to FIG.

Figure 2 shows the depth and TES of the grooves (groups) used in the present invention.
FIG. 2 is a diagram showing the relationship between amplitudes of the recording surface 7 in FIG.
The TBS amplitude corresponding to the reflected light is set as the reference value of zero in this figure. As you can see from this figure, the depth of the groove is λ/8
The maximum amplitude is P at , and the amplitude decreases whether it is deeper or shallower than that. Therefore, if the depth λ/8 of the groove corresponding to the TBS amplitude is taken as the pilot groove 8, and the depth r of the groove corresponding to the TBS amplitude is taken as the pre-groove 6, the pre-groove will be as shown in FIG. TBS amplitude corresponding to groove 6 and viroft group 8
Since the TES amplitude P exceeds the threshold value Va at the position, the position of the pilot groove 8 can be easily detected using a comparator (not shown) having the threshold value Va. If the positional interval La of the pilot groove 8 is several hundred tracks (for example, 500 tracks), counting can be made easier than the conventional method of counting all the tracks when accessing the optical head.

In other words, it is possible to approach the target track position while counting in units of 500 tracks, and the count number is 5.
When it becomes less than 00 tracks, high-speed access becomes possible by switching to the conventional counting method from the biloft group 8 in which less than 00 tracks has been detected to the target track.

FIG. 4 is a diagram showing an embodiment of the present invention. In the figure,
9 is a main pilot groove, and the number of tracks Lr@ in the section to the adjacent main pilot groove is set to several thousand tracks (for example, 5000 racks), and 10 is a sub-pilot groove, where the number of tracks between adjacent main pilot grooves The number of tracks Ls in the section up to 9 is set to several hundred tracks (for example, 500 tracks). The groove depth of each pilot groove is as shown in FIG. 2. The groove depth λ/8 corresponding to the TBS amplitude is defined as the main pilot groove 9, and the groove depth q corresponding to the TBS amplitude is defined as the sub-pilot groove 10. If the depth r of the groove corresponding to the TBS amplitude is pregroove 6, then
As shown in the TBS waveform shown in FIG. 4, the position of the main pilot groove 9 exceeding the threshold value Vb can be detected for every 5000 tracks, and the position of the sub-pilot groove 10 exceeding the threshold value Vc can be detected for every 500 tracks.

In other words, the optical head approaches the target track position by counting every 5000) ranks, and when it reaches less than 5000) ranks, the third track position is reached.
Access can be completed using the means shown in the figure. This allows for easier counting and faster access than the method shown in FIG.

The above explanation assumes that the depth of the main pilot groove 9 is λ/8, the depth of the sub-pilot groove 1o is q,
Although the depth of the groove of the pre-groove 6 is set as r, the groove depth of the main pilot groove 9 is set as r, the depth of the sub-pilot groove 10 as q1 It can also be realized by setting the depth to λ/8 and reversing the dark value setting of a comparator (not shown). Also,
Since only the depth of the pregroove is changed, it can also be applied to magneto-optical disks.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, predetermined groups are set as the main pilot groove and the sub-pilot groove. By counting the sub-pilot grooves, track counting can be omitted, which has the effect of enabling faster access than in the past.

FIG. 6 is a diagram showing a TBS using a conventional optical disc.

1, 2, and 4, 1 is an optical disk, 2 is a substrate, 6 is a pregroove, 7 is a recording surface, 8 is a pilot groove, 9 is a main pilot groove, 10 is a
indicate sub-pilot grooves, respectively.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of the present invention, Fig. 2 is a diagram showing the relationship between the depth of the groove used in the present invention and the TBS amplitude, Fig. 3 is a diagram showing the principle of the present invention, and Fig. 4 is a diagram showing the implementation of the present invention. Figure 5 shows an example of the structure of a conventional optical disc. p trou + fu - (-71 7 heather, 46th month 1:1 possible);! ! Fig. 2 (b) α ■ / 1 B section stock large # face concave half-fire al / l mercenary 9 wood T leap 1st heng place rumors Fig. 3 of Phys., 杢 Fukazuki autograph beginning example 9o; 7βQ Fig. CI) - 帥et m as sword tr-, s'+ym+b+ Cl1l) Fig./IA part 肱大analysis m valley 5 east branch Figure 5

Claims (2)

[Claims] (1) Optical disc (1) comprising recording surfaces (7) and pregrooves (6) alternately provided on tracks of a substrate (2)
A pilot groove (8) is provided at a position for each predetermined number of unit tracks to a specific depth for one round of the pregroove corresponding to the track, and the optical head accesses the optical disc (1). An optical disc characterized by being configured to allow high-speed access. (2) Divide the position of each predetermined unit track number into long-distance access tracks and medium-distance access tracks, and specify one round of the pregroove corresponding to the track for each number of divisions. Claim (1) characterized in that a main pilot groove (9) and a sub-pilot groove (10) are formed at different depths.
1) The optical disc described above.