Abstract

The phase of an interferogram carries the desired information for various applications, such as 3D profilometry, which can measure the surface 3D topography of optical elements. The phase can be obtained with a phase shift interferometer by acquiring a series of interferograms while changing the optical path difference. The optical path difference is generated by a piezoelectric actuator pushing reference mirror. However, the phase achieved by the interferometer has severe error due to the nonlinear characteristic of the piezoelectric actuator. To eliminate the phase error, we propose an open-loop control system to correct the nonlinear characteristic of the piezoelectric actuator. The control system integrates a micro-programmed control unit, a 16-bit digital-to-analog converter, two amplifiers, an inbuilt high-resolution strain gauge sensor, a signal processing unit, and a 24-bit analog-to-digital converter with our software to achieve the purpose. The experimental result of the system can accurately linearize the piezoelectric actuator. Both its control principles as well as its experimental validation are depicted in this paper.

© 2019 Optical Society of America

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