Research On Self - Mixing Interference Measurement Of Sinusoidal Phase Modulation

The laser self-mixing interference technology is a rising sensing technology, it has the features of simple, compact, self-aligning and independent of optical coherent lengths compared to other laser interference. This technology has been applied to a great deal of aspects such as vibration measurement, displacement measurements, speed measurement and so on. In order to improve the displacement measurement accuracy of the self-mixing interferometer, some researchers have taken a great deal of research on modulation and demodulation technology of the self-mixing interference. Sinusoidal phase modulating technique has the advantages of high precision, achieved easily in real systems, and other advantages, it’s suitable for accurate measurement of the large global, high speed displacement.Phase modulation is introduced by electro-optic crystals in the external cavity and modulated self-mixing interference signal demodulation is achieved by Fourier analysis method. Results of displacement measurements and piezoelectric motion parameters in the course of the experiment show that this measurement method is feasible.In order to make better estimates displacement measurement performance of sinusoidal phase modulating self-mixing interferometer, this paper designs sinusoidal phase modulating self-mixing interferometer measurement system based on Agilent 5529A calibrator. We compared the results of sinusoidal phase modulating self-mixing interferometer and Agilent 5529A calibrator in the range of millimeter, micrometer and nanometer, which provided evidence that the range of millimeters displacement is measured at sub-micrometer accuracy and the range of micrometers and nanometer displacement measurement can reach accuracy of 18 nm and 7nm respectively in the common laboratorial environment.Besides, in order to promote the practical use of our system, we designed a cat’s eye reflector as the inspection mirro, which greatly reduces the difficulties of adjusting. By using CAD software to design and process instrumentation shell, we made the sinusoidal phase modulating self-mixing interferometer easier to carry and set.