Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1994-01-05
1995-12-12
Epps, Georgia Y.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4432, 369 4442, 369122, G11B 700
Patent
active
054756626
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an optical disc apparatus and particular to an optical disc apparatus for recording signals on both recording track of hollow and convex portions formed by a guide groove on a disc.
TECHNICAL BACKGROUND
Recently, the development of optical disc apparatus capable of recording and reproducing information signals such as video or voice signal has been active. In the optical disc apparatus capable of recording, a guide groove has previously formed on an optical disc substrate to form tracks. Hereinafter, the track formed by the guide groove is referred to as a hollow portion and the track formed by a portion lies between guide grooves is referred to as a convex portion. Recording or reproduction of the information signal is effected by focusing laser light on a flat portion of the hollow portion or the convex portion of these tracks. In the optical disc, a phase change type material or the like is used, a reflectivity of a recording film thereof changing. In general optical disc apparatus on the market, generally, an information signal is recorded on either of the hollow or convex portion and the other is provided as a guide band for separating adjacent tracks.
FIG. 14 is an enlarged perspective view of an optical disc used in such a prior art optical disc apparatus. In FIG. 14, numeral 1 is a recording layer formed of a phase change material for example. Numeral 2 denotes a recording mark. Numeral 3 is a focused spot of laser light. Numeral 4 is a hollow portion and numeral 5 is a convex portion having a width larger than the hollow portion 4. Numeral 6 denotes an address pit indicative of positional information on the disc. Here, the recording mark is a region whose reflectivity changes by application of laser light having a predetermined intensity. This records the information signal. Moreover, the address pit has been formed as hollow and convex portions of the substrate of the disc previously in the production processing of the optical disc. In FIG. 14, a transparent disc substrate through which incident light transmits is omitted.
A prior art optical disc apparatus using this optical disc will be described with reference to drawings.
FIG. 15 is a block diagram of such a prior art optical disc apparatus. In FIG. 15, numeral 7 is an optical disc and numeral 8 is a recording track which is a convex portion 5 here. Numeral 10 is a semiconductor laser, numeral 11 is a collimation lens for collimating the laser light emitted by the semiconductor laser 10 to output a collimated light, numeral 12 is a half mirror located on a light beam, and numeral 13 is an objective lens for focusing the collimated light transmitted through the half mirror 12 on a recording plane on the optical disc 7. Numeral 14 is a photodetector for receiving a reflection light from the optical disc 7 via the object lens 13 and the half mirror 12 and has two photodetection portions 14a and 14b separated in a direction parallel to the track direction of the disc to obtain a tracking error signal. Numeral 15 is an actuator for supporting the object lens 13. The above-mentioned parts are mounted on a head base not shown and form an optical head 16. Numeral 17 is a differential amplifier supplied with detection signals outputted by the photodetection portions 14a and 14b, and numeral 18 is a lowpass filter (LPF) supplied with a differential signal outputted by the differential amplifier 17. Numeral 19 is a tracking control circuit supplied with an output signal of the LPF 18 for supplying a drive current to the actuator 15. Numeral 20 is a summing amplifier supplied with the detection signals outputted by the photodetection portions 14a and 14b for outputting a summed signal. Numeral 21 is a highpass filter (HPF) supplied with the summed signal from the summing amplifier 20 for supplying a high frequency component to a reproducing signal processing circuit 22 mentioned later, and numeral 22 is the reproduction signal processing circuit supplied with the high frequency component of the summed signal
REFERENCES:
patent: 4423502 (1983-12-01), Dil
patent: 5134607 (1992-07-01), Fuji et al.
patent: 5199022 (1993-03-01), Suzuki et al.
patent: 5199023 (1993-03-01), Yamamoto et al.
patent: 5343454 (1994-08-01), Watanabe et al.
patent: 5351226 (1994-09-01), Mizumoto et al.
"High Track Density Magneto-Optical Recording Using a Crosstalk Canceller" by K. Kayanuma et al; SPIE vol. 1316 Optical Data Storage (1990); pp. 35-39.
Gotoh Yasuhiro
Miyagawa Naoyasu
Epps Georgia Y.
Hindi Nabil
Matsushita Electric - Industrial Co., Ltd.
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