# US 8,570,845 B2 · Optical head and optical information device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,570,845 B2 - Document ID: US8570845B2 - Status: Granted - Kind: B2 - Application number: 13/635,503 - Filed: 2011-03-18 - Published: 2013-01-10 - Granted: 2013-10-29 - Earliest claimed: 2010-03-25 - Assignees: Panasonic Corporation - Applicants: Hideki Nakata; Hidenori Wada; Masahito Nakao - Inventors: Hideki Nakata; Hidenori Wada; Masahito Nakao - Web page: https://patentgrep.com/patent/US8570845B2 ## CPC - G11B 7/1381: Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops (G11B7/1353 - G11B7/1369 take precedence) - G11B 7/0909: {by astigmatic methods} - G11B 7/131: Arrangement of detectors in a multiple array - G11B 7/1384: Fibre optics - G11B 7/1275: Two or more lasers having different wavelengths - G11B 2007/0013: {for carriers having multiple discrete layers} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract There are provided an optical head and an optical information device capable of downsizing the optical head, and capable of improving the qualities of a focus error signal, a tracking error signal, and a reproduction signal. A light detector (120) includes a light-receiving unit (121) for receiving a reflected light beam from an optical disc, and a package (125) for covering the light-receiving unit (121). The package (125) has a plurality of light guides (124) formed on a light-receiving surface on the light beam incident side of the light-receiving unit (121), and for guiding a reflected light beam to the light-receiving unit (121), and a light shield (114) for shielding a region except for a plurality of the light guides (124) from light. ## Claims ### Claim 1 An optical head for reproducing information from an information recording medium having two or more recording layers, the optical head comprising: a light source for emitting a light beam; an objective lens for converging the light beam emitted from the light source to the information recording medium; an astigmatism causing unit for causing an astigmatism in a reflected light beam reflected at the information recording medium; a light beam dividing unit for dividing an incident light beam; and a light detector for detecting the reflected light beam including the astigmatism caused therein by the astigmatism causing unit, wherein the light detector includes: a light-receiving unit for receiving the reflected light beam; a package for covering the light-receiving unit; and a film deposited on a surface of the light detector, wherein the film has a plurality of light guides for guiding the reflected light beam to the light-receiving unit, and a light shield for shielding a region except for a plurality of the light guides from light, wherein the light beam dividing unit divides the incident light beam into a main beam, a first sub-beam, and a second sub-beam, wherein the light-receiving unit includes a main beam light-receiving unit for receiving the main beam, a first sub-beam light-receiving unit for receiving the first sub-beam, and a second sub-beam light-receiving unit for receiving the second sub-beam, wherein the plurality of the light guides are each individually formed on light-receiving surfaces on light beam incident sides of the main beam light-receiving unit, the first sub-beam light-receiving unit, and the second sub-beam light-receiving unit, respectively, and wherein the first sub-beam light-receiving unit and the second sub-beam light-receiving unit are each disposed at a position where an other-layer stray light is not incident. ### Claim 2 (depends on 1) The optical head according to claim 1, wherein each shape of the plurality of light guides is a circular shape. ### Claim 3 (depends on 1) The optical head according to claim 1, wherein each shape of the plurality of light guides is a non-circular shape. ### Claim 4 (depends on 1) The optical head according to claim 1, wherein the package is formed of a resin. ### Claim 5 (depends on 4) The optical head according to claim 4, wherein the package is formed of silicone. ### Claim 6 (depends on 1) The optical head according to claim 1, wherein the package is formed of any of a resin, glass, and a metal, and wherein the plurality of the light guides include an opening formed in any of the resin, the glass, and the metal. ### Claim 7 (depends on 1) The optical head according to claim 1, wherein the package is formed of either a resin or glass, and wherein the light shield includes either a metal film or an optical film formed on a surface of either the resin or the glass. ### Claim 8 (depends on 1) The optical head according to claim 1, wherein the light beam dividing unit is disposed between the objective lens and the astigmatism causing unit, and divides the reflected light beam reflected at the information recording medium. ### Claim 9 (depends on 1) The optical head according to claim 1, wherein the light beam dividing unit is disposed between the light source and the objective lens, and divides the light beam emitted from the light source. ### Claim 10 (depends on 1) The optical head according to claim 1, wherein the light detector further includes a computation unit for performing a prescribed computation on an electric signal obtained by photoelectrically transducing the reflected light beam received at the light-receiving unit wherein the package covers the computation unit, and wherein the light shield entirely blocks a light beam incident on the computation unit. ### Claim 11 (depends on 1) The optical head according to claim 1, wherein the light detector further includes a computation unit for performing a prescribed computation on an electric signal obtained by photoelectrically transducing the reflected light beam received at the light-receiving unit, wherein the package covers the computation unit, wherein the computation unit includes a first computation circuit for generating a focus error signal, a second computation circuit for generating a tracking error signal, and a third computation circuit for generating a reproduction signal of the information recording medium, and wherein the package further has an opening formed on a circuit surface on a light beam incident side of the third computation circuit. ### Claim 12 (depends on 11) The optical head according to claim 11, wherein the opening formed on the circuit surface on the light beam incident side of the third computation circuit is formed with mutually different materials and methods. ### Claim 13 (depends on 1) An optical information device, comprising: the optical head according to claim 1, a driving unit for rotatably driving an information recording medium, and a control unit for controlling the optical head and the driving unit. ### Claim 14 An optical head for reproducing information from an information recording medium having two or more recording layers, the optical head comprising: a light source for emitting a light beam; an objective lens for converging the light beam emitted from the light source to the information recording medium; an astigmatism causing unit for causing an astigmatism in a reflected light beam reflected at the information recording medium; and a light detector for detecting the reflected light beam including the astigmatism caused therein by the astigmatism causing unit, wherein the light detector includes: a light-receiving unit for receiving the reflected light beam; a computation unit for performing a prescribed computation on an electric signal obtained by photoelectrically transducing the reflected light beam received at the light-receiving unit; and a package for covering the light-receiving unit and the computation unit, wherein the computation unit includes a first computation circuit for generating a focus error signal, a second computation circuit for generating a tracking error signal, and a third computation circuit for generating a reproduction signal of the information recording medium, wherein the first computation circuit, the second computation circuit, and the third computation circuit are formed on a same surface as the light-receiving unit, and wherein the package has an opening formed only on a circuit surface on a light beam incident side of the third computation circuit out of the first computation circuit, the second computation circuit, and the third computation circuit, and a light shield for shielding a region except for the opening from light.