Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1997-08-01
1998-12-15
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369 4441, G11B 700
Patent
active
058500812
ABSTRACT:
A method of generating a focus error signal in an optical pickup device including a photodetector including a light receiving surface for receiving the reflected light and divided into first to fourth quadrants defined in a tangential direction and in a radial direction from the center of the light receiving surface and at least four elements positioned in a centrally symmetric relationship with respect to the center of the light receiving surface within the first to fourth quadrants. A preliminary focus error signal is generated as an output difference between an addition output of one pair of the elements placed on centrally symmetric positions of the photodetector and an addition output of the other pair of the elements placed on centrally symmetric positions of the photodetector. A tangential push-pull signal is generated as an output difference between an addition output of one pair of the elements placed along the radial direction of the photodetector and an addition output of the other pair of the elements placed along the radial direction of the photodetector. A radial push-pull signal is generated as an output difference between an addition result of one pair of the elements placed along the tangential direction of the photodetector and an output result of the other pair of the elements placed along the tangential direction of the photodetector. The tangential push-pull signal and the radial push-pull signal is multiplied to generate a correction signal. The difference between the preliminary focus error signal and the correction signal is calculated to generate a focus error signal.
REFERENCES:
patent: 4866689 (1989-09-01), Satokata
patent: 5255252 (1993-10-01), Katayama
patent: 5444233 (1995-08-01), Sasaki
Pioneer Electronic Corporation
Pyo Kevin
Westin Edward P.
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