Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1984-12-21
1987-08-18
Faber, Alan
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
369124, 369111, 369116, G11B 700, G11B 2010
Patent
active
046882030
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an optical recording and reproducing apparatus in which a laser beam is converged to a tiny beam spot and projected onto an optical disc to cause a thermal change therein thereby to effect signal recording and in which during a reproduction process, a beam spot having an intensity level lower than that of the beam for use in recording is projected onto the optical disc to reproduce the recorded signals.
BACKGROUND ART
Recent practice has been to converge a laser beam to a beam spot having a diameter of about 1 .mu.m and thereby to record and reproduce signals on and from an optical disc, respectively. Particularly, there has come into use an apparatus in which a recording material is evaporated onto an optical disc and a thermal change is caused in the recording material by applying a laser beam thereonto to thereby attain recording.
An example of a conventional optical recording and reproducing apparatus of the above-mentioned type will now be described with reference to the drawings.
FIG. 1 shows the construction of a conventional optical recording and reproducing apparatus. The laser beam from a semiconductor laser 1 is concentrated by a condenser lens 2 and then projected onto a convergent lens 5 through a total reflection mirror 4. The convergent lens 5 converges the incident beam to a tiny beam spot of about 1 .mu.m .phi. on an optical disc 8. The reflected beam from the optical disc 8 is passed again through the convergent lens 5 and the total reflection mirror 4 and sent to a beam splitter 3, from which it is received by a light detector 6. Numeral 7 designates a disc motor which rotates the optical disc 8. Numeral 9 designates a preamplifier for amplifying the output signal from the light detector 6 and applying it to a digital demodulator 11 through a signal processing circuit 10. Numeral 12 designates a semiconductor laser drive circuit which is responsive to the signal from a modulator 13 during a recording process to drive the semiconductor laser 1 by an electric current having a value sufficient enough to make its light output higher than the sensitivity of the recording material.
FIG. 2a shows the manner in which a signal is recorded along a guide track 14 in the form of a furrow or groove preliminarily formed on the optical disc 8 in the phase structure. FIG. 2b shows the waveform of an output signal of the preamplifier 9 generated by reproducing the thus recorded pits.
When the tiny beam spot is projected onto the recording material on the optical disc 8, the recording material is changed thermally and blackened as shown in FIG. 2a (the hatched portions). As shown by the output waveform of a reproduced signal in FIG. 2b, the blackened portions are increased in the reflectance (the reflectance increases in the upward direction (the positive direction) in the Figure). In other words, the signal is recorded at the portions of the recording material which are blackened to have an increased relectance. This recording is referred to as blackening recording. TeOx-type materials are used as suitable recording materials for the blackening recording. The TeOx-type materials allow recording therein, but erasing therefrom (restoration) is relatively difficult.
FIG. 3 explains recording materials suitable for the so-called whitening recording, and it shows the manner in which the pits are recorded along the guide track 14 like FIG. 2. In FIG. 3a, when the ting beam spot is projected onto the recording material on the disc, the material is changed thermally and whitened. As shown by the reproduced signal output waveform in FIG. 3b, the portions having the signal recorded therein and whitened are decreased in the reflectance (the reflectance also increases in the upward direction (the positive direction) in FIG. 3b as in the case of FIG. 2b). In other words, the signal is recorded in the portions which are whitened and decreased in the reflectance. This recording is referred to as whitening recording. Suitable materials for this system are TeGexOy-type
REFERENCES:
patent: 4243850 (1981-01-01), Edwards
patent: 4338644 (1982-07-01), Staar
patent: 4472748 (1984-09-01), Kato
patent: 4556967 (1985-12-01), Braat
Koishi Kenji
Matsuo Tamotsu
Satoh Isao
Faber Alan
Matsushita Electric - Industrial Co., Ltd.
LandOfFree
Optical recording and reproducing apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical recording and reproducing apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical recording and reproducing apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1122207