EP0135750A2
Expired / Lapsed
EP
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Optical information recording and reproducing apparatus
Assignee: Hitachi Ltd
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Filing: 1984-08-07
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Granted: —
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Expires: 2004-08-07
Abstract
Abstract In an optical information recording and reproducing apparatus having a laser light source (1) and an optical system so that a beam from the laser light source is irradiated through the optical system on an information recording medium (20) to record and reproduce information, an acousto-optic modulator (4) is disposed in the optical system for receiving the beam from the laser light source, and a modulation unit (101) is provided which comprises an oscillator (50) for generating a plurality of signals at different frequencies, a modulator (51) for modulating the outputs of the oscillator and an adder (52) for adding together the outputs of the modulator.
Inventors
- 👤 Toshimitsu D104-Go Hitachi-Koyasudai Kaku
- 👤 Keiji Kataoka
- 👤 Yoshito Tsunoda
- 👤 Kazuo Shigematsu
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 19:16
CPC Classifications
G; G11; G11B; G11B27/00; G11B27/36; G11B7/00; G11B7/004; G11B7/12; G11B7/125; G11B7/128; G11B7/08; G11B7/09; G11B7/0908; G11B7/0909
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
115 words
An optical information recording and reproducing apparatus comprising: a laser light source (1); an optical system having an acousto-optic modulator (4) receiving a beam from said laser light source and focusing a beam from said acousto-optic modulator on an information recording medium (20); a detecting system receiving light reflected from said information recording medium, for detecting a change in quantity of the reflected light; and a modulation unit (101) including oscillation means (50) for generating a plurality of signals at different frequencies, modulation means (51) for modulating outputs of said oscillation means and means (52) for adding together outputs of said modulation means and driving said acousto-optic modulator with an output of said adding means.
Claim 2
Dependent Claim
115 words
An optical information recording and reproducing apparatus comprising: a laser light source (1); an optical system having an acousto-optic modulator (4) receiving a beam from said laser light source and focusing a beam from said acousto-optic modulator on an information recording medium (20); a detecting system receiving light reflected from said information recording medium, for detecting a change in quantity of the reflected light; and a modulation unit (101) including oscillation means (50) for generating a plurality of signals at different frequencies, modulation means (51) for modulating outputs of said oscillation means and means (52) for adding together outputs of said modulation means and driving said acousto-optic modulator with an output of said adding means.
Claim 3
Dependent Claim
99 words
An optical information recording and reproducing apparatus according to Claim 1 wherein said laser light source is a semiconductor laser emitting an elliptical beam, and said optical system comprises a lens (2) for making parallel the beam from said semiconductor laser, a first cylindrical lens (3) for constricting the parallel beam in the minor axis direction and transmitting a constricted parallel beam to said acousto-optic modulator, optical means (5, 6) for shaping the beam from said acousto-optic modulator into a circular beam, and a lens (10) for focusing the beam from said optical means on said information recording medium.
Claim 4
Dependent Claim
50 words
An optical information recording and reproducing apparatus according to Claim 2 wherein said optical means comprises a second cylindrical lens (5) having the same characteristic as that of said first cylindrical lens, and a beam shaper (6) for shaping the beam from said second cylindrical lens into the circular beam.
Claim 5
Dependent Claim
46 words
An optical information recording and reproducing apparatus according to Claim 2 wherein said optical means comprises a second cylindrical lens (5) having a focal length which is a multiple of a focal length of said first cylindrical lens by an aspect ratio of said elliptical beam.
Claim 6
Dependent Claim
78 words
An optical information recording and reproducing apparatus according to Claim 1 wherein said information recording medium is made of a recording material from which the recorded information is erasable, said modulation unit applies a plurality of signals at different frequencies to said acousto-optic modulator to cause it to produce a plurality of beams, and specified ones of said plurality of beams are used to form, on said information recording medium, an elliptical spot for erasing the recorded information.
Claim 7
Dependent Claim
22 words
An optical information recording and reproducing apparatus according to Claim 5 wherein said information recording medium is a chalcogenide family recording film.
Claim 8
Dependent Claim
72 words
An optical information recording and reproducing apparatus according to Claim 1 wherein said oscillation means includes two oscillation circuits (50-0, 50-1) for generating signals at different frequencies, said modulation means includes two gate circuits (51-0, 51-1) for modulating outputs of said two oscillation circuits independently, and said acousto-optic modulator generates two beams one of which is used for recording information and the other of which is used for reading the recorded information.
Claim 9
Dependent Claim
158 words
An optical information recording and reproducing apparatus having a laser light source (1) and an optical system so that a beam from said laser light source is irradiated through said optical system on an information recording medium (20) to record, reproduce and erase information, characterized in that there are provided an acousto-optic modulator (4) disposed in said optical system for receiving the beam from said laser light source, and a modulation unit (101) including oscillation means (50) for generating a plurality of signals at different frequencies, modulation means (51) for modulating outputs of said oscillation means and means (52) for adding together outputs of said modulation means, that said modulation unit applies the plurality of signals at different frequencies to said acousto-optic modulator to cause it to produce a plurality of beams, and that specified ones of said plurality of beams are used to form, on said information recording medium, an elliptical spot for erasing the recorded information.
Claim 10
Dependent Claim
158 words
An optical information recording and reproducing apparatus having a laser light source (1) and an optical system so that a beam from said laser light source is irradiated through said optical system on an information recording medium (20) to record, reproduce and erase information, characterized in that there are provided an acousto-optic modulator (4) disposed in said optical system for receiving the beam from said laser light source, and a modulation unit (101) including oscillation means (50) for generating a plurality of signals at different frequencies, modulation means (51) for modulating outputs of said oscillation means and means (52) for adding together outputs of said modulation means, that said modulation unit applies the plurality of signals at different frequencies to said acousto-optic modulator to cause it to produce a plurality of beams, and that specified ones of said plurality of beams are used to form, on said information recording medium, an elliptical spot for erasing the recorded information.
Claim 11
Dependent Claim
22 words
An optical information recording and reproducing apparatus according to Claim 8 wherein said information recording medium is a chalcogenide family recording film.
Claim 12
Dependent Claim
38 words
An optical information recording and reproducing apparatus according to Claim 8 wherein said plurality of beams from said acousto-optic modulator form, on said information recording medium, said elliptical spot (ES) and a circular spot (WS) spaced apart therefrom.
Claim 13
Dependent Claim
99 words
An optical information recording and reproducing apparatus according to Claim 8 wherein said laser light source is a semiconductor laser emitting an elliptical beam, and said optical system comprises a lens (2) for making parallel the beam from said semiconductor laser, a first cylindrical lens (2) for constricting the parallel beam in the minor axis direction and transmitting a constricted parallel beam to said acousto-optic modulator, optical means (5, 6) for shaping the beam from said acousto-optic modulator into a circular beam, and a lens (10) for focusing the beam from said optical means on said information recording medium.
Claim 14
Dependent Claim
50 words
An optical information recording and reproducing apparatus according to Claim 11 wherein said optical means comprises a second cylindrical lens (5) having the same characteristic as that of said first cylindrical lens, and a beam shaper (6) for shaping the beam from said second cylindrical lens into the circular beam.
Claim 15
Dependent Claim
46 words
An optical information recording and reproducing apparatus according to Claim 11 wherein said optical means comprises a second cylindrical lens (5) having a focal length which is a multiple of a focal length of said first cylindrical lens by an aspect ratio of said elliptical beam.
Claim 16
Dependent Claim
175 words
An optical information recording and reproducing apparatus having a laser light source (1) and an optical system so that a beam from said laser light source is irradiated through said optical system on an information recording medium (20) to record, reproduce and erase information, characterized in that there are provided an acousto-optic modulator (4) disposed in said optical system for receiving the beam from said laser light source, and a modulation unit (101) including oscillation means (50) for generating at least two signals at different frequencies, modulation means (51) for modulating outputs of said oscillation means independently and means (52) for adding together outputs of said modulation means, that said modulation unit applies signals at least two different frequencies to said acousto-optic modulator to cause it to produce at least two beams one of which forms, on said information recording medium, a spot (WS) for recording information and the other of which forms, on said information recording medium, a spot (ES) spaced apart from the information recording spot and used for reading the recorded information.
Claim 17
Dependent Claim
175 words
An optical information recording and reproducing apparatus having a laser light source (1) and an optical system so that a beam from said laser light source is irradiated through said optical system on an information recording medium (20) to record, reproduce and erase information, characterized in that there are provided an acousto-optic modulator (4) disposed in said optical system for receiving the beam from said laser light source, and a modulation unit (101) including oscillation means (50) for generating at least two signals at different frequencies, modulation means (51) for modulating outputs of said oscillation means independently and means (52) for adding together outputs of said modulation means, that said modulation unit applies signals at least two different frequencies to said acousto-optic modulator to cause it to produce at least two beams one of which forms, on said information recording medium, a spot (WS) for recording information and the other of which forms, on said information recording medium, a spot (ES) spaced apart from the information recording spot and used for reading the recorded information.
Claim 18
Dependent Claim
74 words
An optical information recording and reproducing apparatus according to Claim 14 wherein said oscillation means includes at least two oscillation circuits (50-0, 50-1) for generating signals at different frequencies, said modulation means includes at least two gate circuits (51-0, 51-1) for modulating outputs of said at least two oscillation circuits independently, and one of said gate circuits is driven by a pulse indicative of information to be recorded and the other is DC driven.
Claim 19
Dependent Claim
99 words
An optical information recording and reproducing apparatus according to Claim 14 wherein said laser light source is a semiconductor laser emitting an elliptical beam, and said optical system comprises a lens (2) for making parallel the beam from said semiconductor laser, a first cylindrical lens (3) for constricting the parallel beam in the minor axis direction and transmitting a constricted parallel beam to said acousto-optic modulator, optical means (5, 6) for shaping the beam from said acousto-optic modulator into a circular beam, and a lens (10) for focusing the beam from said optical means on said information recording medium.
Claim 20
Dependent Claim
50 words
An optical information recording and reproducing apparatus according to Claim 16 wherein said optical means comprises a second cylindrical lens (5) having the same characteristic as that of said first cylindrical lens, and a beam shaper (6) for shaping the beam from said second cylindrical lens into the circular beam.
Claim 21
Dependent Claim
46 words
An optical information recording and reproducing apparatus according to Claim 16 wherein said optical means comprises a second cylindrical lens (5) having a focal length which is a multiple of a focal length of said first cylindrical lens by an aspect ratio of said elliptical beam.
References Cited (Backward Citations)
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