Patent ID: 8188420

Claim:
An optical encoder, comprising: (a) a light emitter configured to emit a beam of light therefrom; (b) a code strip or code wheel configured to move along an axis of movement and comprising a plurality of alternating optically opaque and optically transmissive sections disposed along the axis, each of the optically opaque and optically transmissive sections having a width g/2, the optically transmissive sections being spaced apart from one another by a distance g/2, and (c) a light detector comprising a set of light detecting elements, each light detecting element comprising a pair of complementary light detectors arranged substantially parallel to the axis of movement, each light detector in each pair having a width d/2 or d/4, each light detecting element having a width d or 3d/4, the light detecting elements being arranged substantially parallel to the axis of movement; wherein the light beam shines upon the code strip or code wheel, portions of the light beam project through the optically transmissive sections to sweep across the set of light detecting elements as the code strip or code wheel moves along the axis of movement, g does not equal d, the ratio g/d equals 3M/(3M−1) when g is greater than d, the ratio g/d equals 3M/(3M+1) when g is less than d, and M is an integer.