Abstract: A non-contacting sensing method and apparatus is disclosed for positioning a surface, such as the surface of a workpiece. A collimated light beam is projected through a lens having a known focal length onto the surface. Suitable means such as a television camera is positioned to receive light reflected from the surface and provide a series of video pulses, wherein the number of pulses produced per television frame scan corresponds to the size of the light image focused onto the photosensitive element within the camera. The position of the surface relative to the lens is varied until the number of pulses produced per scan is at a minimum.