Patent ID: 8546741

Claim:
An optical finger navigation device comprising: an image sensor to generate an image representative of light detected at a pixel array, wherein the pixel array has a pixel pitch which at least partially defines a surface area of a pixel; a tracking surface that is approximately parallel to the image sensor, wherein a first distance between and substantially orthogonal to planes of the tracking surface and the image sensor is insufficient under a set of illumination constraints to produce at the image sensor a speckle size above a threshold, wherein the threshold is approximately one order of magnitude less than the pixel pitch; and an optical element interposed between the tracking surface and the image sensor, wherein the optical element comprises at least one optical redirection surface to redirect light along an optical path of a second distance between the tracking surface and the image sensor, wherein the second distance is sufficient under the set of illumination constraints to produce at the image sensor a speckle size of at least the threshold.