Laser feedback interferometric system for both displacement and absolute distance measurement

A laser feedback interferometric system for measuring both the displacement and absolute distance of non-cooperative objects is presented. The system is based on a laser-diode pumped Nd:YAG microchip laser，and it is comprised of a frequency-shifted laser feedback interferometer, a frequency-modulated microchip laser based on pumping modulation and a phase-sensitive detection device. The principle of frequency-shifted laser feedback interference is introduced. The principle and method of displacement and absolute distance measurements are elaborated. The measurement resolution was analyzed. The displacement and absolute distance of a blacken workpiece surface were detected experimentally in the laboratory. The results prove that the interferometric system has high sensitivity and relaxed requirement for the reflectivity of the UUT surface, and meets the need of both displacement and absolute distance measurements for uncoupled objects.