Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1976-12-21
1978-08-29
Dahl, Lawrence J.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
1791003V, 358128, G01J 120
Patent
active
041106075
ABSTRACT:
The invention relates to a system for detecting the height fluctuations of a surface on a recording medium in an optical recording or reproducing apparatus. A light source emits a main light beam for recording or reproducing. An optical system, including an objective lens, focuses the main light beam into a spot on the surface. A first reflecting mirror introduces a sublight beam into the peripheral part of the main light beam. The sub-light beam advances in a forward path through the objective lens to be projected onto the recording surface and reflected thereby. The sub-beam returns again through the objective lens along the peripheral part of the main light beam, but on the opposite side from said forward path. A second reflecting mirror extracts the sub-light beam in the return path out of the light to operate a detector which detects fluctuations in the distance between the objective lens and the recording surface and to produce control signals maintaining a constant distance between the objective lens and recording surface.
REFERENCES:
patent: 3716845 (1973-02-01), Chaffin
patent: 3932700 (1976-01-01), Snopko
patent: 4044378 (1977-08-01), Laub
Frosch et al., "Optical Surface Microtopography Measurement and/or Automatic Focussing", IBM Technical Disclosure Bulletin; pp. 504, 505, Jul. 1972.
Honjo Yoshihiko
Kuroda Junji
Dahl Lawrence J.
Victor Company of Japan Ltd.
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