Patent ID: 8416191

Claim:
A navigation input device, comprising: (a) a light source configured to project an illumination light downwardly therefrom; (b) an aperture located beneath an illumination lens and configured to permit at least a portion of the illumination light to pass therethrough for incidence upon a navigation surface located below the aperture, wherein a diameter of the aperture ranges between about 0.25 mm and about 4 mm; (d) an imaging lens having a depth of field of about 12 mm, about 14 mm, about 16 mm, about 18 mm, or about 20 mm and a focal length ranging between about 6 mm and about 50 mm, the imaging lens being at least one of achromatic, telecentric, or double telecentric and being positioned and configured to receive at least a portion of upwardly reflected light formed by at least a portion of the illumination light being reflected from the navigation surface towards the imaging lens, the imaging lens being located a working distance above the navigation surface, the working distance ranging from between about 50 mm and about 80 mm, wherein the illumination light incident on the navigation surface has a substantially constant diameter as the working distance ranges over the depth of field; (e) a light detector comprising a sensor pixel array configured to receive at least a portion of the upwardly reflected light passing through the imaging lens and to convert such portion of the reflected light into imaging signals corresponding to individual pixels in the sensor pixel array, and (f) a navigation processor configured to receive and process the imaging signals corresponding to successively acquired image frames of the sensor pixel array such that output data corresponding to (X,Y) positions of the device with respect to the navigation surface are provided thereby, and further such that the output data include compensation or adjustment for changes in the working distance caused by the device being lifted or lowered in respect of the navigation surface, the changes in the working distance falling within the depth of field of the imaging lens.