JPH09171621A - Discoid recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium from which a playback signal and a wobbling signal can stably be reproduced. SOLUTION: A wobbling groove 2 is previously formed on a disk. The width (w) of this groove is >=1/2 as large as a track pitch q and smaller than the diameter of a reproduction beam spot. Information is recorded on a recording film 3 on the bottom surface of the groove 2. Further, the groove is so made wobbling that both the edges of the groove 2 are in phase with each other. The information is reproduced from the sum signal of a detector which is divided along a disk diameter and a tracking error is generated from the difference signal of this detector. Further, wobbling information on the groove 2 includes absolute time information, which is taken out of the difference signal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a disk-shaped recording medium.

[0002]

2. Description of the Related Art Optical discs as disc-shaped recording media,
It is known that an optical disc is preformed with wobbled grooves. This uses the playback output of the wobbled groove,
This is for obtaining information on tracking errors.

[0003]

When recording a signal on an optical disc having such wobbling grooves, it is conceivable to record the signals on the areas between the grooves, that is, on the lands. 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. Also, if the wobbling phases of adjacent grooves do not match,
There is a problem that it is difficult to obtain other information as a difference signal of the two-divided detector by including other information in the wobbling information.

Therefore, an object of the present invention is to provide a disk-shaped recording medium capable of solving the above-mentioned problem by making the edges on both sides of the groove have the same phase.

[0005]

According to the present invention, a groove having a width smaller than the diameter of a beam spot to be irradiated and having both edges wobbled at a predetermined frequency of the same phase is provided. It is a disk-shaped recording medium having a recording area in which a discrete-valued information pattern is formed.

The edges on both sides of the groove formed on the recording medium are wobbled in the same phase. Therefore, it is possible to prevent the fluctuation of the reproduction output (HF signal) of the signal recorded in the groove and to stably obtain the difference signal, so that it is possible to include other information in the wobbling information.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 shows a reproducing apparatus for reproducing an optical disc to which the present invention is applied, and 1 is an optical disc according to the present invention. In the optical disc 1, as shown in an enlarged manner in FIG. 2, a groove 2 to be wobbled is preformatted. The wobbling frequency of the groove 2 is 22.05 [kHz]. Groove 2
Has clock information and absolute time code information similar to that of a CD (compact disc).

The width w of the groove 2 is the track pitch q
Then, (w ≧ 1/2 q), which is smaller than the diameter of the reproduction spot. In this embodiment, a recording film whose reflectance increases when recording is performed is used. Therefore, when recording is performed in a groove, the level of the reproduction output of the groove (groove level) increases. As a result, the modulation degree RMI (Radial Modulation Index) of the traverse signal decreases.
When the RMI decreases, a sufficient signal amplitude cannot be obtained corresponding to the point where the reproducing beam scans the optical disc in the radial direction across the track, which causes a problem of erroneous track count. Therefore, in one embodiment of the present invention, a wide groove having a track pitch of 1/2 or more is formed,
The relationship between the groove level and the reproduction output level of the land (land level) is set to (land level <groove level), and the reduction of the RMI of the traverse signal is suppressed. 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 In the recording film 3 deposited on the surface of the optical disc 1, the reflectance of the portion after recording is increased. A reflectance modulation film such as bismuth tellurium antimony selenium. Pits are recorded on the bottom surface in the groove 2.

The reproduction of the above-described recorded optical disc is performed by a 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 output to 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.

[0012]

According to the present invention, a wobbled groove is formed in advance on a medium, a recording area is provided in the groove, and the edges on both sides of the groove have the same phase. According to this invention, the groove 2
Since the recording is performed inside, since both edges of the groove 2 having the same phase are applied to the outer portion of the reproduction spot, the fluctuation of the HF signal becomes extremely small, and 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. Even when the groove wobbling information includes other information such as absolute time code and clock information, the other information can be stably reproduced. 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 having a good S / N is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an example of a reproducing apparatus for reproducing an optical disc according to 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. A groove having a width smaller than a diameter of a beam spot to be irradiated and having both edges wobbled at a predetermined frequency of the same phase is provided, and a discrete value information pattern is formed in the groove. A disk-shaped recording medium having a recording area to be formed.