US 4,458,980 AGranted

Optical reproducing head

AssigneeSony Corporation

InventorsHiroshi Ohki, Chiaki Kojima

Life of this patent

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Abstract

An optical reproducing head for reproducing an information signal recorded on an optical record medium includes a semiconductor laser for generating a laser beam, a first off-axis hologram lens irradiated with the laser beam from the semiconductor laser to produce a beam of parallel rays of light that has an optical axis which is off-set with respect to the optical axis of the laser beam, a second off-axis hologram lens irradiated with the beam of parallel rays of light from the first off-axis hologram lens to generate a focused beam which has an optical axis which is off-set with respect to the optical axis of the beam of parallel rays of light and has an optical axis perpendicular to the optical record medium, and a photo-detector detecting the intensity of a non-diffracted wave beam from the first off-axis hologram lens means, the non-diffracted wave beam being at least part of the focused beam which has been reflected from the optical record medium and has been diffracted by the second off-axis hologram lens. The output of the photodetector is used to produce a focus error signal and a tracking error signal for controlling the focus servo and tracking servo operations.

Claims2

Dependent claims

An optical reproducing head for reproducing an information signal recorded on an optical record medium having a reflective layer, comprising:

semiconductor laser means for radiating a laser beam;
first off-axis hologram lens means receiving said laser beam radiated from said semiconductor laser means as a first input wave beam for producing a first beam of parallel rays of light as a first output wave beam, each of said first input wave beam and said first output wave beam having an optical axis which is inclined with respect to the other;
second off-axis hologram lens means receiving said first output wave beam from said first off-axis hologram lens means as a second input wave beam for projecting a focused beam as a second output wave beam onto said optical record medium, each of said second input wave beam and said second output wave beam having an optical axis which is inclined with respect to the other, and said focused beam having an optical axis perpendicular to said optical record medium;
and
photo-detector means for detecting variations in the intensity of a non-diffracted wave beam from said first off-axis hologram lens means, said non-diffracted wave beam being at least a part of the focused beam which has been reflected from said optical record medium and has been diffracted by said second off-axis hologram lens means.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/189,577Filed 23 Sep 1980
Priority: JP 54-12304725 Sep 1979
Granted: 10 Jul 1984
Term ends: Not estimatedThe source records don’t support an estimate.

Classification14 codes

G11B 7/1381
Means for guiding the beam from the source to the record carrier or from the record carrier to the detector: non-lens elements for altering the…
G03F 7/04
Photosensitive materials: chromates
G11B 7/085
Disposition or mounting of heads or light sources relatively to record carriers: with provision for moving the light beam into, or out of, its…
G11B 7/123
Heads, e.g. forming of the optical beam spot or modulation of the optical beam: integrated head arrangements, e.g. with source and detectors…