JP2892325B2 - Optical disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an optical disc apparatus for recording and reproducing an optical disc. 2. Description of the Related Art A wobbling method is known as one of methods for detecting a tracking error when reproducing an optical disk. One specific form of the wobbling method is a method in which a wobbled groove (groove) is formed (pre-formatted) on an optical disc in advance, and tracking error information is extracted by a push-pull signal. [0003] In the conventional optical disk, the wobbling information of the groove has taken into account only tracking error information. When recording / reproducing an optical disk, it is necessary to detect information on a position on the optical disk. Conventionally, together with data to be recorded,
Such positional information was recorded. As a result, there is a problem that the amount of data that can be recorded in the recordable area is reduced. Accordingly, it is an object of the present invention to provide an optical disk apparatus capable of increasing the amount of data recordable on an optical disk by including wobbled grooves not only with tracking information but also with position information. is there. According to the present invention, there is provided an optical disk having a width smaller than the diameter of a beam spot to be irradiated, and having grooves formed in advance in the width direction and wobbled at a predetermined frequency. On the other hand, a detector divided in accordance with the radial direction of the optical disc is provided, and the detector reflected from the optical disc is provided .
An optical disc device detects a beam with a detector and detects position information included in wobbling information of a groove based on a difference signal between the divided detectors . Since the wobbled groove contains not only tracking information but also position information, there is no need to record position information in a recordable area together with data, and the amount of data recorded on the optical disk can be increased. An 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 shown in an enlarged manner in FIG. 2, the groove 2 to be wobbled is preformatted. The wobbling frequency of the groove 2 is set to 22.05 [kHz]. The groove 2 has clock information and information of an absolute time code similar to that of a CD (compact disk).
The information on the absolute time code is described in "Compact Disc Reader" (March 20, 1983, 1st edition, 3rd printing, issuance office: Ohmsha) which is a document distributed before the filing of the present application. And position information on the disk. The width w of the groove 2 is determined by setting the track pitch to q
Then, (w ≧ 1 / 2q), 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 RMI (Radial Modulation Index) of the traverse signal decreases.
When the RMI decreases, a sufficient signal amplitude cannot be obtained corresponding to the point at which the reproduction beam crosses the track when scanning in the radial direction of the optical disk, causing a problem of incorrect 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 level of the reproduced output of the land (land level) is set to (land level <groove level), so that the RMI of the traverse signal is suppressed from decreasing. 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) qλ / 9 <d <λ / 6 In the recording film 3 deposited on the surface of the optical disk 1, the reflectance of the portion after recording increases. For example, a reflectance modulation film such as bismuth tellurium antimony selenium. Pits are recorded on the bottom surface in the groove 2. Unlike the present invention, when recording a signal on an optical disk having a wobbled groove, it is conceivable that the signal is recorded in an area between the grooves, that is, in a land. However, since the wobbling phases of adjacent grooves in the radial direction of the optical disc do not coincide with each other, in other words, the width of the land constantly changes, the fluctuation of the sum signal (referred to as HF signal) of the two-divided detector is extremely large. Had a big problem. In addition, the fact that the wobbling phases do not coincide with each other makes it difficult to include position information for the wobbled groove and obtain this position information as a difference signal of the two-divided detector. According to the present invention, in order to record in the groove, a portion outside the reproduction spot is applied to both side edges of the groove having the same phase, and the fluctuation of the HF signal is reduced.
Further, a stable push-pull signal (difference signal of the two-divided detector) 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. An absolute time code as position information can be stably reproduced from the push-pull signal. Further, since recording is performed in the wide groove, the film in the recording spot has good planarity and the S / N of the reproduction signal is improved. The above-mentioned recorded optical disk is reproduced by an optical system comprising a semiconductor laser 4, an objective lens 5, a λ / 4 plate 6, a beam splitter 7 and a collimator lens 8,
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 addition circuit 12 and the subtraction circuit 13 via the amplifier 11A.
Are supplied to the addition circuit 12 and the subtraction circuit 13 via the.
Assuming that the output signal of the amplifier 11A is Sa and the output of the amplifier 11B is Sb, (Sa + S
b) The HF signal is formed, and the subtraction circuit 13
A push-pull signal (Sa-Sb) is formed. The HF signal taken out to the output terminal 14 is
It contains pit information and is supplied to a demodulation circuit (not shown) of 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 band pass filter 16. The output signal of the band pass filter 16 is supplied to the waveform shaping circuit 17. The clock signal generated in the waveform shaping circuit 17 is supplied to the spindle servo circuit 18. The spindle servo circuit 18 controls a spindle motor 19 to drive the optical disc 1 at CLV. The output signal of the waveform shaping circuit 17 is supplied to the FM decoder 20, and the output terminal 21 obtains absolute time information. According to the present invention, since the wobbled groove includes not only the tracking information but also the position information, it is not necessary to record the position information in the recording area on the disk, and the groove can be recorded on the disk. Data volume can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a reproducing apparatus according to an embodiment of the present invention. FIG. 2 is a partially enlarged view of an optical disk to which the present invention is applied. [Description of Signs] 1 ... optical disk, 2 ... groove, 3 ... recording film, 4 ... semiconductor laser, 9 ... two-segment detector, 1
2 ... Addition circuit, 13 ... Subtraction circuit

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-61-236046 (JP, A)                 JP-A-61-260432 (JP, A)                 JP-A-58-91544 (JP, A)                 JP-A-55-28516 (JP, A)

Claims (1)

(57) [Claims] A detector having a width smaller than the diameter of the beam spot to be irradiated and having a groove wobbled at a predetermined frequency in the width direction and an optical disk having a groove formed in advance , which is divided in a radial direction of the optical disk. And the beam reflected from the optical disk is detected by the detector.
Out, the optical disk apparatus adapted to detect the position information included in the wobbling information of the groove on the basis of a difference signal of the segmented detector.