A fiber-optic sinusoidal phase modulating (SPM) interferometer was proposed for the acquisition and reconstruction of three-dimensional (3-D) surface profile. Sinusoidal phase modulation was induced by controlling the injection current of light source. The surface profile was constructed on the basis of fringe projection. Fringe patterns are vulnerable to external disturbances such as mechanical vibration and temperature fluctuation, which cause phase drift in the interference signal and decrease measuring accuracy. A closed-loop feedback phase compensation system was built. In the subsystem, the initial phase of the interference signal, which was caused by the initial optical path difference between interference arms, could be demodulated using phase generated carrier (PGC) method and counted out using coordinated rotation digital computer (CORDIC) , then a compensation voltage was generated for the PZT driver. The bias value of external disturbances superimposed on fringe patterns could be reduced to about 50 mrad, and the phase stability for interference fringes was less than 6 mrad. The feasibility for real-time profile measurement has been verified.

Date Published: 6 March 2015
PDF: 7 pages
Proc. SPIE 9446, Ninth International Symposium on Precision Engineering Measurement and Instrumentation, 94460V (6 March 2015); doi: 10.1117/12.2180668

Published in SPIE Proceedings Vol. 9446:
Ninth International Symposium on Precision Engineering Measurement and Instrumentation
Junning Cui; Jiubin Tan; Xianfang Wen, Editor(s)