Method and device for detecting focal point

Details Method and device for detecting focal point Method and device for detecting focal point

1985-09-05

1987-01-13

Wan, Gene

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

250204, 369 45, G01J 120, G11B 712

Patent

active

046366253

ABSTRACT:
Less than half of a laser beam reflected from an optical information storage medium through an objective lens is detected by a detector having two light detecting areas. The sum of output signals from the light detecting areas of the detector is employed to detect when the objective lenas enters a focusing range. The difference between the output signals is employed to detect when the laser beam is focused on the optical information storage medium.

REFERENCES:
patent: 4503324 (1985-03-01), Yokota

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