Patent ID: 7238932

Claim:
An optical position sensing device for sensing a two-dimensional displacement, comprising: a first photosensor including a plurality of photodetectors arranged parallel to a first axis, the plurality of photodetectors including at least a first pair and a second pair of photodetectors, wherein the photodetectors of the first and second pairs are arranged adjacent to and in an alternating manner with each other; a second photosensor including a plurality of photodetectors arranged parallel to a second axis, the plurality of photodetectors including at least a third pair and a fourth pair of photodetectors, wherein the photodetectors of the third and fourth pairs are arranged adjacent to and in an alternating manner with each other, and the first and the second axes are at an angle with respect to each other; and an encoder positioned to interfere with a path of light incident on the photosensors such that a pattern of light and shadow is cast onto the photosensors, wherein the encoder and the photosensors are able to move with respect to each other, resulting in modulation of light received by the photosensors, and are arranged such that when the encoder moves relatively in a direction parallel to the first axis, the modulation of light received by the second photosensor is larger than the modulation of light received by the first photosensor, and when the encoder moves relatively in a direction parallel to the second axis, the modulation of light received by the first photosensor is larger than the modulation of light received by the second photosensor.