Patent ID: 7777722

Claim:
An input device, comprising: a light selection control; a first light source; a second light source; and at least one controller configured to: (a) activate the first source so as to illuminate a surface external to the input device with light emitted from the first source, (b) track motion of the surface relative to the input device based on reflection into at least one imaging array of the light emitted from the first source, (c) determine whether a plurality of light source selection criteria is satisfied, including at least determining whether: a user has selected the second light source with the light selection control; an illumination level of light reflected from the surface external to the input device is less than a first user adjustable threshold value; and a contrast level of light reflected from the surface external to the input device is less than a second user adjustable predetermined threshold value by comparing the contrast level with a plurality of autocorrelation values calculated as one of an absolute value of a difference between adjacent non-edge pixel outputs and an absolute value of a difference squared between adjacent non-edge pixel outputs, and (d) in response to determining that the one or more light source selection criteria are satisfied, track motion of the surface relative to the input device based on reflection into the at least one imaging array of light emitted by the second source.