JPH09106576A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a satisfactory signal and a satisfactory wobbling signal. SOLUTION: A wobbled group 2 is previously formed on a disk. Width (w) of this group 2 is set wider than a 1/2 track pitch (q) and narrower than the diameter of a reproducing beam spot. Information is recorded in a recording film 3 on the bottom surface of the group 2. The information is reproduced from the sum signals of detectors divided in the direction of disk diameter, and a tracking error is formed from the difference signal of these detectors. Besides, the wobbling information of the group 2 contains absolute time information, and this time information is extracted from a push-pull signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for recording / reproducing an optical disk.

[0002]

2. Description of the Related Art A wobbling method is known as one of tracking error detecting methods for reproducing an optical disk. One of the specific forms of the wobbling system is that wobbling grooves (grooves) are formed (pre-formatted) on the optical disc in advance, and tracking error,
This is a method of extracting information such as a clock by a push-pull signal. When a recording film whose reflectance increases when recording is used, conventionally, the groove width w is 1 / the track pitch q.
Since it is less than 2, (land level> groove level)
Had a relationship.

[0003]

When recording is performed on an optical disk having the above relationship (land level> groove level), the groove level rises and RMI (Radial
Modulation Index) decreases. This RMI means the degree of modulation of the traverse signal. When the RMI decreases, a sufficient signal amplitude cannot be obtained corresponding to the point across the track when the reproduction beam scans the radial direction of the optical disc.
The problem of wrong track count occurs.

Therefore, it is conceivable to record in the area between the wobbled grooves, that is, the land. When recorded on the land, the RMI increases and a traverse signal having a sufficient amplitude change corresponding to the track is obtained. However, since the wobbling phases of the adjacent grooves in the radial direction of the optical disc do not match, in other words, the width of the land constantly changes, the fluctuation of the sum signal (referred to as the HF signal) of the two-divided detector is extremely large. Had a big problem.

Therefore, the object of the present invention is to reduce the fluctuation of the HF signal in the land recording, and to reduce the R after recording.
An object of the present invention is to provide an optical disk device in which MI increases.

[0006]

SUMMARY OF THE INVENTION The present invention has a wobbling groove having a width not less than 1/2 of the track pitch and smaller than the diameter of the reproducing beam spot, and discrete value information is contained in the groove. It is an optical disk device that reproduces wobbling information of a groove based on a difference signal of a detector divided corresponding to a radial direction of the optical disk on which a pattern is formed.

A wide groove having a width equal to or more than 1/2 of the track pitch is formed and (land level <groove level). Since recording is done in this groove, R
MI rises. Also, in order to record in the groove,
The reproduction spot is applied to both side edges of the groove having the same phase, fluctuation of the HF signal is reduced, and a stable push-pull signal (difference signal of the two-divided detector) is obtained.
Further, since the recording is performed in the groove having a wide width, the flatness of the film in the recording spot is good, and the S / N of the reproduction signal is good.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 shows a reproducing apparatus to which the present invention is applied, and 1 is an optical disk. This optical disc 1
As enlarged and shown in FIG. 2, the wobbling groove 2 is pre-formatted. The wobbling frequency of the groove 2 is 22.05 [kHz]. The groove 2 has clock information and absolute time code information similar to that of a CD (compact disc).
If the track pitch is q, the width w of the groove 2 is
(W ≧ 1/2 q), which is smaller than the diameter of the reproduction spot. As an example, the width w and the depth d of the groove 2 are selected to the following values. Here, λ is the wavelength of the reproduction light.

(9/16) q <w <(12/16) q λ / 9 <d <λ / 6

Recording film 3 deposited on the surface of the optical disk 1.
Is a reflectance-modulating film such as bismuth tellurium antimony selenium whose reflectance increases in the portion after recording. Pits are recorded on the bottom surface in the groove 2.

To reproduce the above-mentioned recorded optical disc, the semiconductor laser 4, an optical system including an objective lens 5, a λ / 4 plate 6, a beam splitter 7 and a collimator lens 8, and 2
Reproduced by the split detector 9. 2-split detector 9
Is a light receiving element 10A divided in the radial direction of the optical disc 1.
And 10B. The output signal of the light receiving element 10A is supplied to the adding circuit 12 and the subtracting circuit 13 via the amplifier 11A, and similarly, the output signal of the light receiving element 10B is supplied to the amplifier 11B.
Is supplied to the adder circuit 12 and the subtractor circuit 13 via.
Assuming that the output signal of the amplifier 11A is Sa and the output of the amplifier 11B is Sb, the addition circuit 12 causes (Sa + S
The HF signal of b) is formed, and by the subtraction circuit 13,
A push-pull signal of (Sa-Sb) is formed.

The HF signal extracted at the output terminal 14 is
It contains pit information and is supplied to a demodulation circuit (not shown) for EFM (8 → 14 modulation). The push-pull signal taken out to the output terminal 15 contains a tracking error and is supplied to a tracking servo circuit (not shown). In the tracking servo circuit, a tracking error signal is formed by, for example, synchronous detection of the push-pull signal. Further, the push-pull signal is supplied to the bandpass filter 16. The output signal of the bandpass filter 16 is supplied to the waveform shaping circuit 17. The clock signal formed in the waveform shaping circuit 17 is supplied to the spindle servo circuit 18. The spindle servo circuit 18 controls the spindle motor 19 to drive the optical disc 1 with CLV. Also, the output signal of the waveform shaping circuit 17 is supplied to the FM decoder 20, and absolute time information is obtained at the output terminal 21.

[0013]

According to the present invention, since the pits are formed in the groove 2, both edges of the groove 2 having the same phase are applied to the outer portion of the reproduction spot, so that the fluctuation of the HF signal is extremely small. In addition, a stable push-pull signal can be obtained. For example, when the wobbling amplitude (peak-to-peak value) is ± 100 nm, the fluctuation of the HF signal can be 1% or less. Further, according to the present invention, after the recording, the difference between the groove level and the land level becomes larger, and the traverse signal can be stably obtained. Further, according to the present invention, since the recording is performed on the bottom surface in the wide groove, the flatness of the film in the recording spot is improved, and the reproduction signal with good S / N can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a playback device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of an optical disc to which the present invention is applied.

[Explanation of symbols]

1 ... Optical disc, 2 ... Groove, 3 ... Recording film, 4 ... Semiconductor laser, 9 ... Two-split detector, 1
2 ... addition circuit, 13 ... subtraction circuit

Claims (1)

[Claims] 1. An optical disc having a wobbled groove having a width not less than 1/2 of the track pitch and smaller than the diameter of the reproducing beam spot, and a discrete value information pattern is formed in the groove. Then, the optical disk device is adapted to reproduce the wobbling information of the groove based on the difference signal of the detector divided corresponding to the radial direction of the optical disk.