Patent ID: 8941052
Filing Date: 2015-01-27
Classification: F21V,G01D

Abstract:
1. An illumination portion of an optical encoder which comprises a scale grating, an imaging portion, and a detector portion, the illumination portion comprising: a light source configured to output light having a wavelength λ; a structured illumination generating portion configured to input the light and output structured illumination wherein the structured illumination comprises an illumination fringe pattern oriented transversely to the measuring axis direction; a first filtering lens; a spatial filtering aperture configuration; and a second filtering lens, wherein: the first filtering lens is configured to focus the structured illumination proximate to a plane of the spatial filter aperture configuration; the spatial filtering aperture configuration includes a central portion that is configured to block zero and higher-order light included in the structured illumination and an open aperture portion proximate to the central portion that is configured to output +1 order and −1 order portions of the structured illumination to the second filtering lens; and the second filtering lens is configured to output the structured illumination to a plane of the scale grating as filtered structured illumination with an illumination fringe pitch P