Automatic focusing apparatus

Details Automatic focusing apparatus Automatic focusing apparatus

1977-07-28

1979-07-31

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

358128, G01J 136

Patent

active

041631498

ABSTRACT:
In automatic focusing apparatus comprising a laser source, optical means for causing a light beam from the laser source to follow an information track on an information recorded medium, a photodetector which consists of quartered photodetection portions and to which a reflected light beam from the information track is guided through a cylindrical lens, and means for controlling the focusing of the light beam by the use of an error signal obtained from the shape and the intensity distribution of a light spot on the four photodetection portions, the improvement wherein a compensation signal is created from the absolute value of a difference between outputs from one set of the opposing photodetection portions and the absolute value of a difference between outputs from the other set of the opposing photodetection portions, to compensate for a disturbance ascribable to a movement of the light spot on the photodetector which arises in correspondence with the error signal.

REFERENCES:
patent: 4051527 (1977-09-01), Braat
patent: 4059841 (1977-11-01), Bricot et al.
patent: 4065786 (1977-12-01), Stewart

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