Optical encoder

Details Optical encoder Optical encoder

1990-12-27

1991-11-26

Evans, F. L.

Optics: measuring and testing

By polarized light examination

With light attenuation

250237G, G01B 1114, H01J 4014

Patent

active

050678167

ABSTRACT:
In an optical encoder of a three grating system, a pitch P2 of a second grating for illuminating a first grating is set at a value larger than a pitch P1 of the first grating and a length of a light transmitting portion of the second grating is set at a value smaller than or equal to the length of the pitch P1. With this arrangement, the incoherency between illuminating lights transmitted through the second grating is improved and an SN ratio of a detection signal is raised. Further, when the reflection type optical encoder is to be realized by use of the three grating system, the second grating and third grating are formed separatedly on the second scale at positions different from each other, and further, a plurality of the third gratings different in phase from each other are formed, so that a plurality of light receiving signals different in phase from one another can be obtained. With this arrangement, the reflection type optical encoder of a desirable three grating system can be realized.

REFERENCES:
patent: 3768911 (1973-10-01), Erickson
patent: 3812352 (1974-05-01), MacGrovern
patent: 4049965 (1977-09-01), Pettigrew
patent: 4079252 (1978-03-01), Brake

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