Reflective encoder with reduced background noise

Details Reflective encoder with reduced background noise Reflective encoder with reduced background noise

2007-12-04

2007-12-04

Lee, Patrick J. (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

C250S231140, C250S231180, C250S225000, C033S0010PT, C341S011000

Reexamination Certificate

active

11352193

ABSTRACT:
An encoder having a code scale and an emitter detector module is disclosed. The code scale includes alternating reflective and opaque stripes. The emitter-detector module includes a light source that generates light and directs a portion of the generated light to the imaging element and a photodetector that generates a signal representing an intensity of light having a linear polarization in a predetermined direction received by the photodetector, the light source and the photodetector are encapsulated in a transparent medium, wherein there is a gap between the transparent medium and the code scale. The predetermined direction is chosen to reduce the intensity of light received by the photodetector that is reflected from an interface between the transparent medium and the gap. A polarization filter can also be included in the light source to further improve the rejection of the light reflected from the interface of the transparent medium and the gap.

REFERENCES:
patent: 5498870 (1996-03-01), Ishizuka
patent: 6437318 (2002-08-01), Egloff et al.
patent: 7182258 (2007-02-01), Foo et al.
patent: 2006/0255252 (2006-11-01), Yamamoto et al.

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