Sinusoidal phase modulating interferometry system for 3D profile measurement

• We establish a all-fiber interferometer with sinusoidal phase modulation, and achieve the high-density interference fringe projection.
• We build a closed-loop compensation system with a good suppression property for the external disturbance.
• By measuring the dynamic deformation of rubber membrane, the feasibility for dynamic profile reconstruction has been demonstrated.

We describe a fiber-optic sinusoidal phase modulating (SPM) interferometer for three-dimensional (3D) profilometry, which is insensitive to external disturbances such as mechanical vibration and temperature fluctuation. Sinusoidal phase modulation is created by modulating the drive voltage of the piezoelectric transducer (PZT) with a sinusoidal wave. The external disturbances that cause phase drift in the interference signal and decrease measuring accuracy are effectively eliminated by building a closed-loop feedback system. The phase stability can be measured with a precision of 2.75 mrad, and the external disturbances can be reduced to 53.43 mrad for the phase of fringe patterns. By measuring the dynamic deformation of the rubber membrane, the RMSE is about 0.018 mm, and a single measurement takes less than 250 ms. The feasibility for real-time application has been verified.