Optical focusing device

Details Optical focusing device Optical focusing device

1979-12-18

1981-10-20

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

369 45, G01J 136

Patent

active

042963168

ABSTRACT:
An optical information system is provided with an optical focussing device for adjusting a position of an objective lens. The optical focussing device is comprised of a photosensing unit to which a part of a light beam reflected from a disc and passed through the objective lens is projected through a semitransparent mirror and a cylindrical lens. The photosensing unit for detecting a shape of the projected image of the light beam is assembled by a first photo-cell having a narrow photoelectric surface extending in the direction of movement of the projected image and second and third photo-cells each having a rectangular photoelectric surface closely disposed to the first photo-cell surface. The second and third photo-cells are connected to a adder to sum signals detected by both cells. The adder and the first photo-cells connected to a differential amplifier to compare the signal detected by the first photo-cell with the output of the adder. The differential amplifier is connected to a objective lens moving unit to supply a lens moving signal to the unit, thereby moving the objective lens to a predetermined position.

REFERENCES:
patent: 4079247 (1978-03-01), Bricot et al.
patent: 4163149 (1979-07-01), Sawano et al.
patent: 4209793 (1980-06-01), Ueno

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