A disturbance-free surface profile measuring system with sinusoidal phase integrating-bucket modulation

A surface profile measuring system based on fringe projection and sinusoidal phase integrating-bucket modulation has been thoroughly studied and described in detail. Fringe projection can be achieved using Mach-Zehnder interferometer structure and Young's double pinhole principle. Sinusoidal phase modulation can be achieved by driving the piezoelectric transducer with a cosine voltage signal. To achieve a good insensitivity to disturbances, we build up a feedback subsystem for phase compensation, and a disturbance-free performance can be achieved with a phase stability of 5.25 mrad for fringes, which is conducive to the high-resolution surface profile measurement. By measuring the surface profile of an aluminum plate for twice over an interval of 10 min, the repeatability is about 13 nm. Experiment results confirm that the proposed profile measuring system is applicable for practical application with high accuracy.