Patent ID: 7482575

Claim:
A rotary optical position encoder for detecting angular position about a rotational axis, comprising: a light source; a monolithic scale disk including an optical scale pattern; a monolithic reticle substrate between the light source and the scale disk, the reticle substrate including a plurality of sets of reticle aperture patterns; detection and conversion circuitry; and digital processing circuitry coupled to the detection and conversion circuitry, wherein: the light source, scale disk, reticle substrate, and detection and conversion circuitry are configured to form a plurality of optical sub-encoders at respective angular positions about the rotational axis, each sub-encoder having a respective optical path extending from the light source to the detection and conversion circuitry via a respective set of reticle aperture patterns of the reticle substrate and the optical scale pattern of the scale disk, each sub-encoder generating a respective digital position output value, the plurality of sub-encoders including two incremental position sub-encoders, and the digital processing circuitry is operative to combine the digital position output values of the sub-encoders to generate an encoder position output value, the combining including calculating an average of the respective digital position output values of the two incremental position sub-encoders.