US Patent 7285766 Optical positioning device having shaped illumination

One embodiment relates to an optical displacement sensor for sensing relative movement between a data input device and a surface by determining displacement of optical features in a succession of frames. The sensor includes an illuminator and a detector. The illuminator has a light source and illumination optics to illuminate a portion of the surface with a planar phase-front. The detector has a plurality of photosensitive elements and imaging optics. The illuminator and the detector are configured such that the illuminated portion of the surface is less than fifty percent larger than a field of view of the photosensitive elements of the detector. Other embodiments are also described.