Pick-up device for optical disk readout using waveguide gratings
First Claim
1. An optical device for detecting focus error, tracking error and recorded data in a read-only or read-write optical head system, comprising:
- a diffraction grating consisting of a grating plate having a plurality of linear gratings and respectively associated waveguides for input coupling an optical beam;
an optical condensing lens;
a focus detector;
a tracking detector;
a data detector;
a mounting frame having internal stops and openings for holding said grating plate, condensing lens, and detectors, said mounting frame having openings for wire feedthrough to said detectors; and
an incline on said mounting frame for receiving said grating plate and tilting said grating plate at a preselected angular orientation for input coupling;
wherein all of said optical beam that is processed for detecting focus and tracking error is input coupled into said waveguide by said diffraction grating.
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Abstract
An optical device for detecting focus error, tracking error and recorded data in an optical head system has a grating plate having a plurality of gratings and waveguides. The gratings are fabricated by holographic exposure of a resist layer spin-coated onto a glass substrate. The gratings include a processing grating to efficiently input couple light into the waveguide and to effect a desired change in the input coupling efficiency with defocus of a beam of light at an optical disk. The optimum pattern of the processing grating is based on the location and intensity variation of diffraction orders in the beam returning from the optical disk and appodization of the beam. Unfocused beams and large active areas of the detectors relax the tolerance for detector placement so that placement is not critical. The four focus and tracking detectors and data detector needed for complete signal processing are compactly formed on single chip.
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Citations
22 Claims
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1. An optical device for detecting focus error, tracking error and recorded data in a read-only or read-write optical head system, comprising:
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a diffraction grating consisting of a grating plate having a plurality of linear gratings and respectively associated waveguides for input coupling an optical beam; an optical condensing lens; a focus detector; a tracking detector; a data detector; a mounting frame having internal stops and openings for holding said grating plate, condensing lens, and detectors, said mounting frame having openings for wire feedthrough to said detectors; and an incline on said mounting frame for receiving said grating plate and tilting said grating plate at a preselected angular orientation for input coupling; wherein all of said optical beam that is processed for detecting focus and tracking error is input coupled into said waveguide by said diffraction grating. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An optical device for detecting focus error, tracking error and recorded data in a read-only or read-write optical head system using a beam of light with a cross-sectional area, comprising:
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a diffraction grating consisting of a grating plate having a plurality of linear gratings and respectively associated waveguides for input coupling the beam, said gratings having patterns of parallel grooves to produce optical signals for focus error detection and tracking error detection; a focus detector; a tracking detector; an optical condensing lens, said lens reducing the cross-sectional area of the beam to easily fit the beam onto active areas of a data detector for data detection; a mounting frame having internal stops and openings for holding said grating plate, condensing lens, and detectors, said mounting frame having openings for wire feedthrough to said detectors; and an incline on said mounting frame for receiving said grating plate and tilting said grating plate at a preselected angular orientation for input coupling the beam, wherein all of the beam that is processed for detecting focus and tracking error is input coupled into said waveguide by said diffraction grating. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A method for forming an optical device for detecting focus error, tracking error and recorded data in a read-only or read-write optical head system, comprising:
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forming a diffraction grating consisting of a grating plate having a plurality of linear gratings and respectively associated waveguides for input coupling an optical beam; forming an optical condensing lens; forming a focus detector; forming a tracking detector; forming a data detector; forming a mounting frame having internal stops and openings for holding said grating plate, condensing lens, and detectors, said mounting frame having openings for wire feedthrough to said detectors; and forming an incline on said mounting frame for receiving said grating plate and tilting said grating plate at a preselected angular orientation for input coupling, wherein all of said optical beam that is processed for detecting focus and tracking error is input coupled into said waveguide by said diffraction grating. - View Dependent Claims (21, 22)
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Specification