Patent ID: 7317513

Claim:
A distance measurement apparatus comprising: a focusing element that focuses light in a focal plane whose respective distance from the focusing element depends on a respective wavelength of the light, such that the respective wavelength of light is reflected from a focal spot on a target surface back toward the focusing element when the target surface is located at the respective distance; a light-amplifying gain medium having an intracavity facet and a rear facet, the light-amplifying gain medium providing light to and receiving light from the focusing element; and a wavelength sensing device: wherein: when the distance measuring apparatus is operably arranged relative to the target surface a resonant cavity is formed between the rear facet and the target surface; the light-amplifying gain medium predominantly receives the respective wavelength of light reflected from the focal spot on the target surface and preferentially amplifies and emits the received predominant respective wavelength of light; and the wavelength sensing device is arranged to sense the respective wavelength of light amplified by the light-amplifying gain medium and to provide a signal corresponding to that respective wavelength, wherein the respective wavelength corresponds to the respective distance such that the signal is indicative of the respective distance.