OPTICAL DISPLACEMENT DETECTION OVER VARIED SURFACES

Embodiments of the present invention enable an optical device to track on a diffusing surface over which a transparent and/or translucent and/or optically smooth surface is placed. Some embodiments are directed towards detecting when an optical device is lifted off the surface it was resting on. Embodiments also include a sensing system that detects the z distance (distance to the tracking surface) and improves image quality by improving the effectiveness of the optical sensor subsystem and/or the illumination subsystem at the detected z distance. Other embodiments include a system and method that enables an optical device to track on a transparent and/or translucent and/or optically smooth surface alone. This may involve dark-field imaging based on certain features (e.g., dirt) already present on the transparent surface. Alternately, this may involve creating features such as droplets, spreading dirt residue, and creating thermal spots, which can be used for tracking.