Patent ID: 8063355

Claim:
A reflective multi-turn optical encoder sub-module, comprising: a gear having an outer geared periphery and an upper surface having no apertures or holes disposed therethrough; a geared rotatable shaft attached to an underside of the gear; an optically reflective first area disposed on a first portion of the upper surface; an optically substantially non-reflective second area disposed on a second portion of the upper surface, and a substrate disposed above and opposing the upper surface, the substrate comprising a light emitter and first and second arrays of light detectors disposed and configured on the substrate such that first and second output signals provided by the first and second arrays of light detectors are out of phase with respect to one another by a predetermined phase difference; wherein the gear and the substrate are configured and arranged respecting one another such that at least portions of the light emitted by the light emitter and incident on the first area are reflected towards at least portions of the first and second arrays of light detectors for detection thereby as the gear and the substrate rotate in respect of one another, and at least portions of the light emitted by the light emitter and incident on the second area are substantially not reflected from the second area and are not detected by the first or second arrays of light detectors as the gear and the substrate rotate in respect of one another; and wherein the first array and second arrays of light detectors further comprise, respectively, concentric half-ring-shaped first inner and second outer pairs of light detectors.