Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1984-05-29
1986-12-23
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369 45, G01J 120
Patent
active
046313974
ABSTRACT:
Focussing error detecting apparatus includes a composite lens formed of a single glass lens and a single plastic lens and a photodetector disposed behind the composite lens in opposed relation thereto. The glass lens has a uniform focal length, the plastic lens is formed of a pair of lens regions divided by a flat interface including an optical axis of light incident on the composite lens, and the pair of lens regions have back focal lengths different from each other and optical axes spaced apart from each other. The photodetector is placed so that its photodetecting face is at a middle point between converged points of light emitted from the pair of lens regions on the optical axis of the incident light when the light incident on the composite lens is focussed. The photodetector comprises first and second photodetecting sensors for receiving light passed through portions of the first lens region which are respectively spaced apart from and adjacent to the flat interface and third and fourth photodetecting sensors for receiving light passed through portions of the second lens region which are respectively spaced apart from and adjacent to the flat interface so that a focusing error signal is produced from the difference between the sum of first and fourth photodetected signals from the first and fourth photodetecting sensors and the sum of second and third photodetected signals from the second and third photodetecting sensors.
REFERENCES:
patent: 4376303 (1983-03-01), Lurie
patent: 4513408 (1985-04-01), Nomura et al.
Kubota Shigeo
Ohsato Kiyoshi
Eslinger Lewis H.
Madoo L. W.
Nelms David C.
Sinderbrand Alvin
Sony Corporation
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