Patent ID: 7732755
Filing Date: 2010-06-08
Classification: G01D

Abstract:
1. An encoder comprising a code scale having a plurality of tracks thereon; a plurality of bandpass filters applied to the plurality of tracks of the code scale, wherein each of the plurality of bandpass filters corresponds to a specific track of the code scale to filter out light outside of a corresponding band of wavelengths; an illumination system that illuminates said tracks; and a plurality of photodetectors, each photodetector receiving light from a corresponding one of said tracks and generating a signal indicative of a quantity of light received from that track, each photodetector being limited to detecting light in the band of wavelengths corresponding to that track, wherein each track generates light in the band of wavelengths corresponding to that track, and wherein said band of wavelengths corresponding to one of said tracks is different from said band of wavelengths corresponding to said tracks that are next to that track; wherein each track comprises a plurality of alternating reflective and absorptive stripes and wherein said photodetectors detect light from said illumination system that is reflected from said reflective stripes; and wherein one of said reflective stripes comprises the corresponding bandpass filter for limiting light leaving that reflective stripe to light in said band of wavelengths corresponding to that track.