EP0283002A2
Expired / Lapsed
EP
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Optical head
Assignee: Panasonic Holdings Corp
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Filing: 1988-03-16
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Granted: —
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Expires: 2008-03-16
Abstract
Abstract An optical head for reproducing optical recording medium has reflection optical means, such as a reflection type astigmatic optical Fresnel lens (7A) or reflection type light-beam-dividing (into at least two beams) Fresnel lens, grating or prisms, on or above a surface of a beam splitter (4), so that light returning from the optical recording medium (6) travels in the beam splitter to photo-detector means in at least two divided parts. The size of the optical head is reduced by setting the optical path from the reflection optical means to the photo-detector inside the beam splitter.
Inventors
- 👤 Teruhiro Shiono
- 👤 Kentaro Setsune
- 👤 Osamu Yamazaki
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 15:28
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/135; G11B7/1356; G11B7/08; G11B7/09; G11B7/0908; G11B7/0909; G11B7/0916; G11B7/1353; G11B7/1381
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
240 words
An optical head comprising: a light source for emitting a light beam, a beam splitter for splitting said laser light beam incident to its light incident face into at least two light beams, one in straight direction and the other in a different direction, an objective lens for focusing a light splitted by the beam splitter to make a focused spot and project it on an optical recording means, to make a return light reflected from said optical recording means, photo-detector means comprising plural photo-detection elements provided on or above a face of said beam splitter, reflection optical means which is provided on or above a return light output face which is other than a return light output face to which said light source is opposing, with respect to said return light from said optical recording means, said reflection optical means reflecting light beam incident thereto in plural different manners, first manner being that when said focused spot is made nearer than the recording face of said recording medium its reflected light beam makes a first image to make said photo-detector issue a first signal, when said focused spot is made farther than said recording face its reflected light beam makes a second image to make said photo-detector issue a second signal, and when said focused spot is made accurately on said recording face its reflected light beam makes a third image to make said photo-detector issue a third signal.
Claim 2
Dependent Claim
240 words
An optical head comprising: a light source for emitting a light beam, a beam splitter for splitting said laser light beam incident to its light incident face into at least two light beams, one in straight direction and the other in a different direction, an objective lens for focusing a light splitted by the beam splitter to make a focused spot and project it on an optical recording means, to make a return light reflected from said optical recording means, photo-detector means comprising plural photo-detection elements provided on or above a face of said beam splitter, reflection optical means which is provided on or above a return light output face which is other than a return light output face to which said light source is opposing, with respect to said return light from said optical recording means, said reflection optical means reflecting light beam incident thereto in plural different manners, first manner being that when said focused spot is made nearer than the recording face of said recording medium its reflected light beam makes a first image to make said photo-detector issue a first signal, when said focused spot is made farther than said recording face its reflected light beam makes a second image to make said photo-detector issue a second signal, and when said focused spot is made accurately on said recording face its reflected light beam makes a third image to make said photo-detector issue a third signal.
Claim 3
Dependent Claim
47 words
An optical head in accordance with claim 1 wherein said reflection optical means is astigmatic optical element, for producing an astigmatic light beam which is reflected thereby and travels in said beam splitter towards said photo-detector, and said photo-detector means has at least two divided detector elements.
Claim 4
Dependent Claim
56 words
An optical head in accordance with claim 1 wherein said reflection optical means is a beam-dividing element to divide said light beam to at least two light beams, which travels in said beam splitter towards said photo-detector, and said photo-detector means has at least a pair of photo-detector, each pair comprising at least two divided parts.
Claim 5
Dependent Claim
23 words
An optical head in accordance with claim 1 wherein said reflection optical means is a diffraction element which makes diffraction of incident light.
Claim 6
Dependent Claim
20 words
An optical head in accordance with claim 1 wherein said refraction optical means is formed integral with said beam splitter.
Claim 7
Dependent Claim
18 words
An optical head in accordance with claim 1 wherein said photo-dectector is formed integral with said beam splitter.
Claim 8
Dependent Claim
33 words
An optical head in accordance with claim 1 wherein said photo-detector is of PIN-type, PN-type or Schottky-type amorphous Si amorphous SiGe or amorphous SiSn or amorphous SiGeSn formed on a transparent conductive film.
Claim 9
Dependent Claim
45 words
An optical head in accordance with claim 1 wherein said beam splitter is a polarizing beam splitter, a quater-wave plate is provided between said beam splitter and said objective lens, and another quater-wave plate is provided between said beam splitter and said reflection optical means.
Claim 10
Dependent Claim
25 words
An optical head in accordance with claim 8 wherein said beam splitter and at least one of said quater-wave plates are formed integral each other.
Claim 11
Dependent Claim
20 words
An optical head in accordance with claim 8 wherein said reflection optical means is made integral with said quater-wave plate.
Claim 12
Dependent Claim
31 words
An optical head in accordance with claim 1 wherein a collimation lens is provided between said beam light source and said beam splitter and said reflection optical means has focusing characteristics.
Claim 13
Dependent Claim
17 words
An optical head in accordance with claim 11 wherein said collimation lens is a transmission Fresnel lens.
Claim 14
Dependent Claim
17 words
An optical head in accordance with claim 1 wherein said objective lens is a transmission Fresnel lens.
Claim 15
Dependent Claim
19 words
An optical head in accordance with claim 11 wherein said collimation lens and said beam splitter are made integral.
Claim 16
Dependent Claim
19 words
An optical head in accordance with claim 1 wherein said objective lens and said beam splitter are made integral.
Claim 17
Dependent Claim
42 words
An optical head in accordance with claim 1 wherein said beam splitter has a non square quadrilateral section at a plane which is perpendicular to beam splitting plane of said beam splitter and is parallel to optical axes of light beams therein.
Claim 18
Dependent Claim
18 words
An optical head in accordance with claim 1 wherein said reflection optical means is of transparent synthetic lesin.
Claim 19
Dependent Claim
16 words
An optical head in accordance with claim 2 wherein said photo-detector is of four divided structure.
Claim 20
Dependent Claim
18 words
An optical head in accordance with claim 2 wherein said astigmatic optical element is reflection elliptical Fresnel lens.
Claim 21
Dependent Claim
22 words
An optical head in accordance with claim 2 wherein said astigmatic optical element is an astigmatic reflection Fresnel lens of off-axis type.
Claim 22
Dependent Claim
30 words
Method for making optical head in accordance with claim 4, wherein said reflection optical means is made by using a matrix made by electron-beam or ion-beam lithography or mechanical working.
Claim 23
Dependent Claim
30 words
Method for making optical head in accordance with claim 12 wherein said transmission Fresnel lens is made by using a matrix made by electron-beam or ion-beam lithography or mechanical working.
Claim 24
Dependent Claim
30 words
Method for making optical head in accordance with claim 13 wherein said transmission Fresnel lens is made by using a matrix made by electron-beam or ion-beam lithography or mechanical working.
Claim 25
Dependent Claim
19 words
Method for making optical head in accordance with claim 1 wherein said reflection layer is deposited by sputtering method.
Claim 26
Dependent Claim
19 words
An optical head in accordance with claim 4 wherein said diffraction element consists of gratings having sawtooth relief profile.
Claim 27
Dependent Claim
19 words
An optical head in accordance with claim 1 wherein reflection layer of said reflection optical means is Ag layer.
Claim 28
Dependent Claim
32 words
An optical head in accordance with claim 3 wherein said beam dividing element is reflection circular or elliptical Fresnel lens, or reflection cylindrical lens, or reflection cylindrical grating, or reflection convergence grating.
Claim 29
Dependent Claim
20 words
An optical head in accordance with claim 27 wherein said reflection Fresnel lens is an off axis type Fresnel lens.
Claim 30
Dependent Claim
16 words
An optical head in accordance with claim 3 wherein said beam-dividing element consists of reflection prisms.
Claim 31
Dependent Claim
14 words
An optical head in accordance with claim 27 wherein said grating has uniform period.
Claim 32
Dependent Claim
15 words
An optical head in accordance with claim 27 wherein said grating has symmetric relief profile.
References Cited (Backward Citations)
No citation records indexed.
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