Optical recording medium, reproducing system, method of reproduc

Details Optical recording medium, reproducing system, method of reproduc Optical recording medium, reproducing system, method of reproduc

1995-08-28

1998-09-15

Krynski, Willaim

Stock material or miscellaneous articles

Circular sheet or circular blank

428 642, 428 644, 428913, 3692751, 369284, B32B 300

Patent

active

058076409

DESCRIPTION:

BRIEF SUMMARY
DETAILED DESCRIPTION OF THE INVENTION

1. Industrial Application Field of the Invention
The present invention relates to prevention of duplication of a recording medium, and more particularly to an optical disk with a duplication preventing function, a method of fabricating such an optical disk, a method of reproducing an optical disk, a reproducing system, a method of fabricating an optical disk original record, and a method stopping an illegal program operation.
2. Description of the Prior Art
Generally, fabrication of Optical disks succeeds manufacturing of the original record, master, mother and stamper, and optical disks are duplicated and mass-produced from the stamper in accordance with the injection molding technique. The stamper can sometimes be manufactured directly from the original record. Generally, a photoresist is applied onto a glass-made surface-grinded substrate and photosensitized with a laser beam intensity-modulated in accordance with an information signal being recorded before being developed so as to form an irregular configuration comprising signals and/or grooves corresponding to the photosensitivities. These signals and grooves will hereinafter be referred generally to as signals pits.
FIG. 6 is a block diagram showing a conventional recording system for an original record, where a laser optical system for focusing control and a beam expander in a recording laser optical system are omitted from the illustration. In FIG. 6, the whole of the original recording recording system is designated at 61A where numeral 1 represents a recording laser, 2 denotes an optical modulator, 3 depicts a mirror, 4 indicates a lens actuator, 5 stands for a glass plate onto which a photoresist is applied, 6 represents a spindle motor, 7 denotes a signal source, and 8 depicts a recording equalizer. A signal generated from the signal source 7 is subjected to change of its pulse duration (width) by a constant quantity in the recording equalizer 8, before being inputted into the optical modulator 2 to be used to intensity-modulate the laser light emitted from the recording laser 1. The intensity-modulated laser light passes through the mirror 3 and further through a lens, focusing-controlled by the lens actuator 4, before exposing the photoresist on the glass plate 5.
On the other hand, an optical disk reproducing system focuses a semiconductor laser beam on a signal surface of an optical disk and then converts the intensity of the reflected light from the signal surface into an electrical signal (which is called an RF signal) by means of a photodiode or the like of an optical pickup device, which signal is waveform-shaped to be demodulated to a digital signal which in turn, is subjected to a digital signal processing, thus reproducing the original signal.
FIG. 7 is a block diagram showing a prior optical disk reproducing system 47A. In FIG. 7, numeral 9 represents an optical disk, 10 designates an optical pickup, 11 denotes a spindle motor, 12A indicates an analog waveform shaping section, 13 stands for a digital demodulating section, 14 represents a digital signal processing section, 15 designates a control section, 16 denotes a focus servo section, 17 depicts a tracking servo section, and 18 indicates a rotational servo section. Further, numeral 20A stands for a control section for controlling the entire reproducing operation and for issuing a display signal to a display section 41.
A signal immediately before demodulation of the digital signal, i.e., an RF signal, has eye patterns, one example of which is illustrated in FIG. 2. The difference (which is called asymmetry) may occur more or less between the center of the eye pattern and the center of the amplitude thereof, while, even if the difference therebetween takes place to some extent, the slice level Vs is corrected by an automatic correcting slice circuit 31 at the time of the demodulation to a digital signal so that the central voltage Vs of the eye pattern is automatically detected as indicated in the waveform (9) of FIG. 3 before slicing it. A

REFERENCES:
patent: 4961182 (1990-10-01), Saito et al.
patent: 5410527 (1995-04-01), Ashinuma
patent: 5475664 (1995-12-01), Shimizume et al.
patent: 5590111 (1996-12-01), Kirino et al.

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