JP3139745B2 - Optical disk header information detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk header information detecting apparatus, and more particularly to an apparatus for detecting header information from prepits of an optical disk using both lands and grooves as recording tracks.

[0002]

2. Description of the Related Art In a recordable optical disk, a pre-groove is provided as a track guide groove, and recording / reproduction is performed by detecting a track position shift signal from the groove.
In order to improve the track density in such an optical disc, a method has been proposed in which both a groove portion and a land portion between the grooves are used as recording tracks. In such land-groove recording optical discs, the track interval is narrow, so that it is difficult to provide header information by independent pre-pits (pre-pits) in each track as in a conventional optical disc.

Therefore, as shown in FIG. 3, it is conceivable to form header information by pre-pits 9 at the boundary between the land track 12 and the groove track 11 and to use the same header information from both the land track and the groove track. (Intermediate (shared) addressing). In this case, the beam spot 10 moving along the track
On the other hand, one of the header information indicates whether the prepit is formed on the left or right side.

As a method for detecting such header information, the same push-pull method as that for detecting a track error signal from a pregroove is assumed. In the push-pull method, the reflected light of the optical disk is divided into two in the direction orthogonal to the track.
This is to detect the positional deviation of the pre-groove from the difference in the amount of received light, which is detected by the split photodetector.

[0005]

However, in the above-described conventional push-pull method, since the signal is used in a low frequency band for servo which follows the track position deviation, the same high frequency component as the recording information signal is directly used. The information on the pre-pits cannot be detected. For this reason, there has been an inconvenience that a push-pull signal detection circuit having a wide band capable of newly detecting pre-pit information is required.

[0006]

An object of the present invention is to provide an optical disk header information detecting device which can solve the disadvantages of the prior art and can easily detect the header information without requiring a track error signal having a wide band and a high S / N. To do so.

[0007]

According to a first aspect of the present invention, there is provided a photodetector for receiving reflected light from prepits formed on a land-groove recording type optical disk medium by an intermediate addressing method . An optical head having a track error detection circuit that generates a track error signal based on the output of the photodetector, and an information signal detection circuit that generates a signal corresponding to the unevenness of the pre-pits based on the output of the photodetector, A header information detection circuit for detecting header information based on the position of the prepit with respect to the track center obtained from the output of the track error detection circuit and the unevenness of the prepit obtained from the output of the information signal detection circuit. ing.

According to the second aspect of the present invention, a two-divided photodetector is provided as the photodetector, and the track error detecting circuit tracks the servo signal band from the output of the two-divided photodetector by a push-pull method. Generate an error signal,
The configuration is adopted.

According to the third aspect of the present invention, a quadrant photodetector is provided as a photodetector, and the track error detection circuit generates a track error signal from the output of the quadrant photodetector by the heterodyne method. , Is adopted.

In the present invention, a four-divided photodetector is provided as the photodetector, and the track error detection circuit generates a track error signal from the output of the four-divided photodetector by a phase difference method. To do.

The invention according to claim 5 employs a configuration in which the information signal detection circuit detects header information from the sum of outputs of the elements of the multi-divided photodetector.

[0012]

[0013] Accordingly, the above-mentioned object is achieved.

In these inventions, reproduction of prepits from an optical disk is performed by irradiating a small spot from the optical head 2 onto the medium surface. The optical head detects a track error signal and an information signal based on a change in the total amount of reflected light from the medium, and sends the information signal to the track error detection circuit 3 and the information detection circuit 4, respectively. The detection of the track error signal at this time is sufficient if there is a signal band similar to the conventional servo band. The header can be recognized by the header information detection circuit 5 from the output of the two signals of the track error detection circuit 3 and the information detection circuit 4.
In general, the header information is arranged on the boundary between the land and the groove as a block having a certain length in consideration of the ease of pit formation. Therefore, the band of the track error signal in the header area does not detect pit information one by one, but only detects whether a block of a certain length is arranged on the left or right. Since the information signal of the pit is obtained by detecting the information signal based on the change in the total amount of reflected light, it is sufficient if the position of each block can be specified.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to FIG. In FIG. 1, an optical disc 1 is capable of land / groove recording, and employs an intermediate address system for a header portion. The optical head 2 is a conventional general optical head for this kind of optical disk.
The output of the photodetector provided in the optical head 2 is input to a track error detection circuit 3 and an information signal detection circuit 4 at the subsequent stage. The output of the track error detection circuit 3 and the output of the information signal detection circuit 4 are input to a header information detection circuit 5.

The optical disk medium 1 is provided with land groove tracks and prepits as shown in FIG.
The configuration of the pre-pits may be one provided on the right or left side other than the one provided on the left and right of the track center as shown in FIG.

Recording and reproduction on the optical disk are performed by irradiating the medium surface with a minute spot from the optical head 2. The optical head detects a track error signal and an information signal based on a change in the total amount of reflected light from the medium, and sends the information signal to the track error detection circuit 3 and the information detection circuit 4, respectively. The detection of the track error signal at this time is sufficient if there is a signal band similar to the conventional servo band. The header can be recognized by the header information detection circuit 5 from the output of the two signals of the track error detection circuit 3 and the information detection circuit 4.

In general, taking into consideration the ease of pit formation,
The header information is arranged as a block having a certain length at the boundary between the land and the groove. Therefore, the band of the track error signal in the header area does not detect pit information one by one, but only detects whether a block of a certain length is arranged on the left or right. Since the information signal of the pit is obtained by detecting the information signal based on the change in the total amount of reflected light, it is sufficient if the position of each block can be specified.

FIG. 2 shows a method of detecting a track error.
As shown in FIG. 1A, a push-pull system in which a light beam 7 is received by a two-divided photodetector 6 and a difference signal is formed can be used. This is the same method as that for detecting a track error signal for pregroove servo, and has the advantage that it can be used without any particular change to the conventional optical head detection method.

On the other hand, the push-pull method has a problem that when a light beam moves as indicated by an arrow due to a lens shift or a tilt of a disk, an offset is easily generated in a detection signal. Therefore, as another method of detecting a track error signal, as shown in FIG. 2 (b), a sum signal of diagonal components is formed by using a four-division photodetector 8, thereby obtaining a heterodyne method or a phase difference method. , A track error signal can be detected. In the heterodyne method, a track error signal is formed by sampling a difference between two signals at a pit edge position, and in the phase difference method, a time difference in change between two signals due to a pit edge is detected.

These methods have a feature that an offset hardly occurs even when the light beam 7 moves. Also, in these systems, a wideband signal including pit edge position information is required as an output of the photodetector. However, since only a time-averaged track error signal is finally detected, a push Compared with the case where the information of the pre-pit is directly read by the pull method, the S / N of the photodetector output signal is not so required, so that there is an advantage that the circuit can be easily formed.

Here, in detecting the information signal, it is naturally possible to detect the total sum of the outputs of the split type photodetectors instead of providing a detector separately from the track error signal.

[0023]

The present invention is constructed and functions as described above. According to this, the track information signal and the information signal are separately detected, and the header information is detected by combining these two detection signals. Therefore, the header information can be easily detected without the need for a track error signal having a wide band and a high S / N.

When the track error signal is detected by the push-pull method, there is an advantage that the conventional optical head detection method can be used without any change.

On the other hand, when the heterodyne method or the phase difference method is used, an offset is hardly generated even when the light beam moves, and the photodetector is compared with the case where the information of the pre-pit is directly read by the push-pull method. The S / N of the output signal is not so required, which facilitates circuit creation.

In addition, when the information signal is obtained from the sum of the outputs of the multi-segmented photodetectors, the simplification of manufacture can be promoted by reducing the number of detectors, and the cost can be reduced by unifying the detectors. The present invention can provide an excellent optical disk header information detecting device that has never been achieved before.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating an embodiment of a photodetector;
(A) shows the case using the push-pull method, and (b) shows the case using the heterodyne method or the phase difference method.

FIG. 3 is a schematic configuration diagram showing a configuration of a prepit according to an intermediate (shared) address method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical disk medium 2 optical head 3 track error detection circuit 4 information signal detection circuit 5 header information detection circuit 6 two-segment photodetector 7 light beam 8 four-segment photodetector 9 prepit 10 beam spot 11 groove track 12 land track

Continuation of front page (56) References JP-A-7-29185 (JP, A) JP-A-63-53777 (JP, A) JP-A-63-161534 (JP, A) JP-A-1-223634 (JP) , A) JP-A-7-296390 (JP, A) JP-A-7-50014 (JP, A)

Claims (5)

(57) [Claims] 1. An optical head having a photodetector for receiving reflected light from prepits formed by an intermediate address method formed on a land-groove recording type optical disc medium, and a track error signal based on an output of the photodetector. A track error detection circuit to generate; an information signal detection circuit to generate a signal corresponding to the unevenness of the prepit based on an output of the photodetector; and a track center of the prepit obtained from an output of the track error detection circuit. An optical disc header information detecting device, comprising: a header information detecting circuit for detecting header information based on a position and unevenness of the pre-pit obtained from an output of the information signal detecting circuit. 2. A two-part photodetector is provided as the photodetector, and the track error detection circuit generates a track error signal from the output of the two-part photodetector by a push-pull method of a servo signal band. 2. The optical disk header information detecting device according to claim 1, wherein: 3. A four-divided photodetector is provided as the photodetector, and the track error detection circuit generates a track error signal from an output of the four-divided photodetector by a heterodyne method. The optical disk header information detecting device according to claim 1, wherein 4. A four-divided photodetector is provided as the photodetector, and the track error detection circuit generates a track error signal from an output of the four-divided photodetector by a phase difference method. The optical disk header information detecting device according to claim 1, wherein 5. The optical disk header information according to claim 2, wherein said information signal detection circuit detects said header information from a sum of outputs of respective elements of said multi-divided photodetector. Detection device.