JP2696917B2 - Optical disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly to an optical disk device that records and reproduces information by light.

[Conventional technology]

In optical discs, which are recording media using light,
In order to follow a target track, it is necessary to obtain a track error signal from the disk. As a method for following such a track, in a recordable optical disk, there is a method in which a continuous pre-groove is formed and a track error signal is obtained by using diffracted light from the pre-groove.

According to this method, when the optical disk device is mounted on an optical disk device and driven to rotate by using a pre-groove provided on the optical disk, a converging spot can be used to control a target track to follow.

[Problems to be Solved by the Invention] However, a problem with this method is that errors tend to occur in the track error signal with respect to the inclination of the disk during use. That is, tracking is easily influenced by the tilt of the optical disk mounted on the apparatus, and depending on the degree of the disk tilt, the tracking error signal is greatly affected, which may hinder tracking control.

Therefore, as shown in FIG. 5, a pre-pit 2 wobbled with respect to the track center 1 is formed at a predetermined interval, and a focused spot 3 from a pair of wobbled pits is formed.
A method of obtaining an error signal from the amount of light reflected by the light source has been considered.

The method using the wobbling pits 2 has an advantage that the change of the error signal with respect to the disk inclination is small as compared with the method using the pregroove.

However, in the system using the wobbling pits 2, the following problem occurs when the stability of the servo is to be improved.

That is, the wobbling pit 2 is provided along the track as shown in FIG.

Increasing the number of wobbling pits 2 for obtaining a track error signal can shorten the sampling period. However, in this case, an area where information can be recorded, that is, a data area is restricted.

As described above, the above-described method has an advantage over the above-described pre-groove method with respect to the disk tilt, however, on the other hand, since sampling is performed at regular intervals, a wide servo band is required in order to widen the servo band. It is necessary to reduce the interval between the bling pits 2 and increase the sampling frequency, and there is a disadvantage that the area where information can be recorded is reduced by the amount corresponding to the formation of the wobbling pit. In addition, if pits are lost due to defects, there is a problem that tracking accuracy is reduced.

An object of the present invention is to provide an optical disk device that does not cause the above-described problems.

[Means for solving the problem]

The present invention relates to a multi-beam type optical head capable of simultaneously forming a plurality of condensed spots, and an optical disc having concentric or spiral tracks provided with sampling servo pre-pits at predetermined intervals. An optical disk device to be used, wherein when the number of condensed spots formed by the optical head is n and the interval between prepits for sampling servo is L, m is an integer satisfying m ≦ n and the position of the prepit is adjacent track. It is characterized in that there is an approximate L / m shift in the track direction between adjacent blocks or between adjacent blocks having a predetermined number of tracks as one block.

[Action]

By irradiating the prepits which are shifted by approximately L / m in the track direction between adjacent tracks or adjacent blocks with n focused spots, even if the interval between the prepits on the negative track is L, the L Sampling can be performed at a cycle shorter than the corresponding cycle.

For example, as shown in FIG. 2, if pre-pits are formed on the same track at intervals of L and the number of condensed spots formed by the optical head is three, the position of the pre-pit between adjacent tracks is L / 3. If they are shifted only sequentially, sampling can be performed at the cycle of L / 3, and the sampling cycle can be increased without shortening the pre-pit interval.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. As shown in FIG. 1, the optical disk device includes an array LD5, a half mirror 6, a condenser lens 8, and a plurality of photodetectors.
13 and a multiplexer to which the output of each photodetector 13 is supplied
10, an error detector 11, and a lens drive circuit 12.

The array LD5 and the like constitute a multi-beam type optical head capable of simultaneously forming a plurality of condensed spots.

The optical disc 9 mounted on the apparatus of this embodiment is of a type having concentric or spiral tracks provided with sampling servo prepits at predetermined intervals.

The relationship between the optical head described above and the optical disk 9 is as follows.

That is, as shown in FIG. 2, for example, when the number of condensed spots 3 formed by the optical head is three and the interval between the prepits 2 is L, the distance between adjacent tracks (or, as will be described later, (The number of tracks is one block) and the positions of the pre-pits 2 are set so as to be shifted by approximately L / 3 in the track direction.

Generally speaking, the optical disc device according to the present invention is provided with a multi-beam type optical head capable of simultaneously forming a plurality of condensed spots 3 and prepits 2 for sampling servo at predetermined intervals. In an optical disc apparatus provided with an optical disc 9 having concentric or spiral tracks, the number of condensed spots 3 formed by the optical head is n, m is an integer satisfying m ≦ n, and a sampling servo Assuming that the interval between the prepits 2 is L, the prepits 2 are located between adjacent tracks or between adjacent blocks each having a fixed number of tracks as one block.
Are sequentially shifted by approximately L / m in the track direction.

The multiplexer 10 is used for selectively switching the output obtained by photoelectrically converting the reflected light of the plurality of condensed spots 3 by the respective photodetectors 13, and by supplying the output to the error detector 11. Tracking control is performed.

Specifically, the tracking control can be performed as follows.

As shown in FIG. 1, the light emitted from the array LD5 is condensed on the optical disk 9 as a multi-spot by the condenser lens 8. The reflected light from the disk is separated by the half mirror 6, and the light detector 13 detects the reflected light from each spot.

The output of each photodetector 13 is provided to a multiplexer 10, where the detection output of the reflected light from each spot is selectively switched and supplied to an error detector 11.

In this case, the input to the error detection circuit 11 can be given in the following cycle.

That is, as shown in FIG. 2, the pre-pit 2 is provided at a position slightly shifted left and right with respect to the track center 1. The pre-pits 2 are formed at intervals L. If the number of the condensed spots 3 formed by the optical head is three as described above, the three tracks can be recorded and reproduced simultaneously by arranging them in parallel on adjacent tracks as shown in the figure. In such a parallel operation, in the case shown in the figure, the positions of the prepits 2 are sequentially shifted by L / 3 between adjacent tracks.

Because of such a shift, sampling is performed even if the interval of the pre-pit 2 on the same track is L.
This can be done in the cycle of L / 3.

In this way, the output from each of the photodetectors 13 is detected by the multiplexer 10 as a spot for sampling, and is input to the error detection circuit 11. The error detection circuit 11 detects a track error signal. The lens drive circuit 12 is driven by this error signal to control the spot to pass through the center of the track.

The tracking control can be performed as described above. As described above, if the condensed spots for obtaining the track error signal are sequentially switched, the sampling can be performed at the cycle of L / 3, and the tracking can be performed on the same track of the pre-pit 2. Can be increased without shortening the interval of. That is, the servo band can be increased without shortening the interval between the formation of the sampling pre-pits 2, and
Servo stability is improved.

In this way, without sacrificing data space,
The servo stability can be improved, but this can also be performed as follows.

For example, in FIG. 2, it is considered that a track error signal is obtained from all three condensed spots, but if two of the three are used, the pre-pits may be formed shifted by L / 2, In this case, a double sampling period is obtained.

In the case where the array LD is used as the light source of the optical head, the interval between the condensed spots on the optical disk cannot be reduced so much, and the spot positions between adjacent tracks may be shifted as shown in FIG. . Even in this case, sampling can be performed with the pre-pit arrangement as shown in FIG. 2, but the sampling interval becomes non-uniform. Therefore,
As shown in FIG. 3, a uniform sampling interval can be obtained by adding the spot interval 1 between adjacent tracks to the change in the pre-pit position (L / 3 + 1).

Further, as described above, the formation of the converged spot by the optical head is not limited to the method of forming the condensed spot for each adjacent track.

That is, in the case where the converging spots are provided not by adjacent tracks but by a fixed number of tracks, for example, it is conceivable to provide every other converging spot 3 as shown in FIG. In this case, the positions of the pre-pits 2 may be changed between the two tracks as one block 4.

Furthermore, although each of the above examples described three spots, other numbers are possible at the same time.

 Therefore, the present invention is applicable when n is 2 or more.

In addition, the present invention can be applied not only to a recording and reproducing apparatus but also to a reproduction-only machine used for an application in which only reproduction is sufficient. The same can be said for a recording-only machine.

〔The invention's effect〕

As described above, according to the present invention, servo stability can be improved without reducing the data area.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of the relationship between a condensing spot and an optical disk, FIG. 3 is a diagram showing another example, and FIG. FIG. 5 is a view showing another example, and FIG. 5 is a view showing a conventional technique. DESCRIPTION OF SYMBOLS 1 ... Track center 2 ... Prepit 3 ... Condensing spot 4 ... Block 5 ... Array LD 6 ... Half mirror 8 ... Condensing lens 9 ... Optical disk 10 ... Multiplexer 11 ... Error detection circuit 12 …… Lens drive circuit 13 …… Photodetector

Claims (1)

(57) [Claims] An optical disk having a multi-beam type optical head capable of simultaneously forming a plurality of condensed spots and a concentric or spiral track provided with sampling servo pre-pits at predetermined intervals. And an optical disk device using the optical head, wherein the number of condensed spots formed by the optical head is n,
When the interval between the prepits for the sampling servo is L, m is an integer satisfying m ≦ n, and the position of the prepit is
An optical disc apparatus characterized in that the track is shifted by approximately L / m in the track direction between adjacent tracks or between adjacent blocks having a predetermined number of tracks as one block.