Reflective optical encoder device with light beams applied as sp

Details Reflective optical encoder device with light beams applied as sp Reflective optical encoder device with light beams applied as sp

1989-11-28

1991-01-22

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

369 4437, G01D 534

Patent

active

049873016

ABSTRACT:
A reflective rotary optical encoder device for detecting an angular speed or position of a movable member includes an optical encoder disc rotatable with the movable member, the optical encoder having an encoder track composed of a series of equally spaced pits alternating with inter-pit lands therebetween, the pits and the inter-pit lands having equal lengths l. A laser beam pickup applies three laser beams as respective laser beam spots to the optical encoder and detects laser beams reflected from the laser beam spots on the optical encoder to produce electric signals representative of the encoder track. Adjacent light beam spots on the optical encoder are spaced at a pitch P expressed by: ##EQU1## where n is an integer of 1 or more. The length l may be substantially the same as or larger than the diameter of each of the laser beam spots. The electric signals produced by the laser beam pickup include a focus servo signal, a tracking servo signal, and two signals each representative of encoder track which are out of phase with each other by a phase angle of 90.degree..

REFERENCES:
patent: 4680466 (1987-07-01), Kuwahara et al.
patent: 4795901 (1989-01-01), Kitazawa
patent: 4827123 (1989-05-01), Gray

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