Research On Phase-shift Controller Based On White Light Interferometry

Phase-shifting interferometry is one of the key technologies of the ultraprecise measurement and nano-detection,alse a main branch of modern optical measurement .It is an non-contact method with which has high sensitivity, precision and real-time measurement.As one of the most popular technolo-gies,phase-shifting interferometry is becoming a big concern among the acade-mics at home and abroad.This paper mainly discussed the theory of phase-shifting interference and the principle of converse piezoelectric effect of PZT. The position sensitive detector always detects the micrometric displacement of PZT at a certain voltage and creats a feedback loop with the micrometric displacement to control the voltage.Adopting the PID control technology,the system of closed-loop control includes voltage driving,photoelectric detection and displacement compensator.In this paper,it mainly expounds the design mothod of hardware and software in the system.PSD capturs the position of lightspot and transforms it into the weak current signal,the current signal passes magnifying,sieving its waves, sampling,coming into A/D conversion,and then acquired and processed by microcomputer.Comparting the result with the value, adopt PID control Algorithm to reduce the error and output accurate analog voltage by digital-analog converter.The voltage drives the PZT deformat linily and then the micrometric displacement of PZT is in the monitoring of the photoelectric detection device.The systerm effectively solves the non-linear,the creep characteristics of PZT,improves the measuring accuracy largely.The systerm communicates with PC through USB communication,achieves automation of phase-shift control.