Optical mouse with uniform level detection

Abstract

An optical mouse includes a housing movable across a work surface with a source of non-coherent light in the movable housing for illuminating the work surface at a low or grazing angle of incidence, and may include a two dimensional array of photodetectors, each of which may produce an output in response to light reflected from surface irregularities on the illuminated work surface. The housing may include a memory for storing the photodetector outputs captured at one or more times. Circuitry in the housing may track movement of the housing relative to the work surface by comparing at least some of the photo detector outputs captured at a first time with at least some of the photo detector outputs captured at a second time depending upon whether a characteristic condition in the photo detector outputs, such as uniformity, is detected. The circuitry may track movement of the housing by comparing light reflected from the surface irregularities a first time with light reflected there from at a second time unless a detectable image is not included therein.