Optical Measurement Device
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
By varying the wavelength of light used in a heterodyne interferometer, the former half wavelength ambiguity can be eliminated and the resultant variation in phase of the interferometer output unambiguously determines optical path length differences. In Fig. 1, coherent light source 1 directs light of tunable, variable wavelength through beam splitter 2 to a wavelength calibrator 3. Other light from source 1 continues to beam splitter 4 and is directed as the signal arm 5 of the interferometer to beam scanning and focusing system 6 and to three-dimensional object 7. Reflected light returns through system 6, splitter 4 to detector 8 that may include several photodetectors.