Patent ID: 8508726

Claim:
A rotary position detector comprising: a housing having an inner space; a shaft extending into the housing inner space, the shaft rotatable about an axis thereof; a light source positioned to emit light rays into the housing inner space; a light detector positioned within the housing inner space in a spaced relation to the light source, the light detector comprising a first number of segmented light sensors disposed in pairs about the axis, each pair comprising one “A” detector element and one “B” detector element, the pairs disposed so that each “A” detector element is circumferentially positioned between two “B” detector elements and each “B” detector element is positioned between two “A” detector elements; a light blocker positioned between the light detector and the light source, the light blocker comprising a second number of opaque, substantially equal-surface-area elements rotatable with the shaft, the second number equal to one-half of the first number, wherein a radial extent of the light blocker elements is less than a radial extent if the light sensors; and a signal connection to the light detector for measuring an amount of light impinging on the segmented light sensors to thus measure a rotary position of the shaft.