JPH01154329A - Optical disk - Google Patents

Abstract

PURPOSE:To execute continuous reproduction with plural optical heads without track jumping by forming spiral grooves in clockwise and counterclockwise directions in respective prescribed regions. CONSTITUTION:The spiral grooves are formed in the clockwise direction in the region of radius r1 to r2 of an optical disk 10 and the spiral grooves are formed in the counterclockwise direction in the region of the radius r2 to r3. On the other hand, the optical head ha moves in a concentrical direction and the optical head hb moves in an outside circumferential direction. The optical heads ha, hb are first positioned at the point of the radius r2. The optical heads ha, hb move along the spirals of the grooves 4a, 4b respectively by the moving quantity (k) and are positioned at the points of the radii (r2-k), (r2+k) in one second after the optical disk 10 rotates clockwise. The total value of the radii of the two optical heads ha, hb is always 2r2. Since the radial positions are propositional to line speeds, the total of the line speeds of the optical heads ha, hb attains a specified value as well. The optical heads ha, hb are, therefore, capable of executing continuous reproduction without track jumping.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc used for optical disc loading, and more particularly to an optical disc that is mainly composed of video signals and that reproduces, records and reproduces moving pictures, still images, audio, code signals, etc.

[Conventional technology]

Conventionally, this kind of optical disc is, for example, as shown in Fig. 2(a).
, as shown in (b).

In the optical disc 1 shown in FIG. 2(a), concentric groups 2a and 2b are formed. In this case, when the optical disk 1 rotates once during continuous playback, the optical head needs to make a track jump to the inside or outside. However, such track jumps usually make it difficult to control the servo of the optical head drive unit and cause the playback operation to become unstable.Therefore, a configuration to eliminate track jumps was developed as shown in Fig. 2 (b). ) is being considered. This creates clockwise or counterclockwise spiral grooves on the optical disc 1, respectively, in groups 3a and 3.
With this structure, the optical head accesses the groups 3a and 3b along the spiral, thereby eliminating the need for track jumps.

Incidentally, recently, methods of using a plurality of optical heads have been increasing in order to record a large amount of information on an optical disk. In such cases, rather than moving multiple optical heads in the same direction, it is better to move one optical head from the center to the outer circumference and move the other from the outer circumference to the center to keep the line of all optical heads in line. It has been studied that if the total speed is kept at a constant value, it is advantageous to be able to record at a higher density.

However, when the above-described method is applied to the optical disc as shown in FIG. It is necessary to jump two tracks per rotation.

[Problem that the invention seeks to solve]

In this way, when a conventional optical disc is reproduced using multiple optical heads, track jumps of the optical heads are required even in Fig. 2(a), Φ), so the servo operation of the optical head drive control section is There was a problem that it became unstable.

[Means for solving problems]

In the present invention, radius r1 to radius rl+m (however, 0(m(
A clockwise or counterclockwise spiral group formed in the area up to (r2-r1)/2) and a radius r2
−n (where 0<n<(r 2 - r 1 )/2) to a radius r2, and includes a spiral group in the opposite direction to the above group.

[Effect]

The present invention can be applied to clockwise and counterclockwise groups.
Multiple optical heads perform continuous playback without track jumps.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, 4a is a spiral group formed in a clockwise direction from radius r1 to radius r2 of optical disc 1o, and 4b is a spiral group formed from radius r2 to radius r2 of optical disc 1o. This is a spiral group formed counterclockwise in a region up to radius r3. Further, it is assumed that ha and hb are optical heads, and the optical head ha moves in the direction of the center of the circle, and the optical head hb moves in the direction of the outer circumference.

Assuming that the optical head ha v hb is initially located at a radius r2, the clockwise rotation of the optical disk 10 causes the optical heads ha and hb to move ff1k along the spirals of groups 4a and 4b after 'seconds. and will be located at radii (r2-k) and (r2+k), respectively. Therefore, two optical heads ha + hb
It is clear that the sum of the radial positions of is always 2·r2.

Furthermore, since the radial position is proportional to the linear velocity, the sum of the linear velocities of these optical heads ha and hbO also remains constant.

As described above, in this embodiment, the groups 4a and 4b are spirally arranged clockwise and counterclockwise, so that the optical heads ha and hb can perform continuous playback without track jumping.

〔Effect of the invention〕

As described above, according to the present invention, two clockwise and counterclockwise spiral groups are formed in predetermined areas, so continuous playback can be performed without track jumps even when a plurality of optical heads are used. Furthermore, since the servo operation is stable and the linear velocity is constant, even higher density recording is possible.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an embodiment of the present invention, Fig. 2(a)
, (b') is a plan view of a conventional example. 4a, 4b...group, 1011...optical disk, ha, hb...optical head.

Claims (1)

[Claims] In an optical disc in which the area from radius r1 to radius r2 (r1<r2) is a playable or recording/playable area, radius r1 to radius r1+m (where 0<m<(r2-r)
A clockwise or counterclockwise spiral group formed in the area up to 1)/2) and an area from radius r2-n (however, 0<n<(r2-r1)/2) to radius r2 1. An optical disc characterized in that a spiral group is formed in a direction opposite to the group.