Rotary optical encoder employing multiple subencoders with common reticle substrate

Abstract

A rotary optical position encoder for detecting angular position includes a light source, a monolithic scale disk including an optical scale pattern, a monolithic reticle substrate including sets of reticle aperture patterns between the light source and the scale disk, detection and conversion circuitry, and digital processing circuitry. The light source, scale disk, reticle substrate, and detection and conversion circuitry form a plurality of optical sub-encoders at angular positions about the rotational axis, each sub-encoder having an optical path extending from the light source to the detection and conversion circuitry via a respective set of reticle aperture patterns and the optical scale pattern. The digital processing circuitry is operative to combine digital position output values of the sub-encoders to generate an encoder position output value. The optical sub-encoders can include incremental position encoders that provide high-resolution position indications with improved thermally stability due to the use of a shared reticle substrate. Additional optical sub-encoders provide zero-reference or 'index' indications as well as a coarse absolute position.