Optical encorder for detection having a moving reference point

Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system

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Details

356356, 250237G, G01D 534

Patent

active

059819413

ABSTRACT:
The present invention provides an optical encoder capable of using the recesses and convexes of a movable plate and a fixed plate to accurately generate a Z phase signal in synchronism with an A/B phase signal. Phase type diffraction gratings on the moving and fixed plates including a plurality of tracks with different grating pitches cause parallel coherent beams to interfere with one another, and a light receiving part detects the intensity of light to obtain a plurality of synchronous signals with different periods. On the other hand, the light receiving part detects light spots formed by condensing elements on the movable plate to generates a single pulse per rotation as a reference position. One of the plurality of synchronous signals that has the shortest period is selected as an A/B phase signal that depends on the movement of the movable plate. The conjunction of the reference position signal and the plurality of synchronous signals is determined as a Z phase signal indicating the origin of the movable plate, thereby obtaining a Z phase signal in synchronism with one pulse of the A/B phase signal.

REFERENCES:
patent: 5073710 (1991-12-01), Takagi et al.
patent: 5661296 (1997-08-01), Ishizuka et al.
patent: 5663497 (1997-09-01), Ishizuka
patent: 5694218 (1997-12-01), Fukui et al.

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