Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1986-02-11
1988-05-03
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369 45, G01J 120, G11B 509
Patent
active
047422181
ABSTRACT:
A focus error detection apparatus and an optical disk apparatus comprising a focusing lens for focusing reflected light coming from a light reflecting surface which is to be adjusted at the focal point of a projected light beam; a beam splitter means for dividing the output light of said focusing lens into a first and a second focused light beam; a first and a second photo-detector disposed respectively on the optical paths of said first and said second focused light beam, one of which is located behind the convergence point of said first focused light beam and the other of which is located before the convergence point of said second focused light beam, each of them generating outputs proportional to the amount of light within a predetermined region of the received light image, when it varies so that it is enlarged; and a circuit generating a focus error signal by using the difference between the outputs of said two photo-detectors.
REFERENCES:
patent: 4460989 (1984-07-01), Russell
patent: 4622659 (1986-11-01), Hazel et al.
Hishiki Masaaki
Kaku Toshimitsu
Kamisada Toshimasa
Kato Tuyoshi
Maeda Takeshi
Allen Stephone B.
Hitachi , Ltd.
Nelms David C.
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