Compact polyphase optical position encoder

Abstract

A compact polyphase optical encoder subassembly for installation in host equipment is disclosed. The subassembly includes a moveable scale; and, a unitized rotatable housing for aligning a light source, a mask and a photodetector array having at least a pair of photodetector areas symmetrically disposed about an axis of rotation of the housing and responsive to light energy from the light source in further response to relative position of the scale. The housing further includes in its preferred form a bolt having a widened head and a threaded shank for passing through an opening in a base of the host, a threaded nut engageable with the shank opposite to the head for thereby securing the bolt to the base, and a compressible washer for enabling a predetermined range of vertical compression between the head and the base as the nut is tightened on said shaft. The housing further includes a light source holder which in preferred form comprises a central support, a reflective surface in optical alignment with the photodetector array and being aligned and supported by the central support, and a lateral arm spaced away from the central support, the lateral arm for holding the light source in optical alignment with the reflective surface, whereby the subassembly may be made very compact in terms of height and still provide a substantial distance between the light source and the mask, thereby minimizing penumbra effects.