Online calibration technology and stability evaluation of long-baseline homodyne laser interferometry

摘要

Online calibration technique for a long-baseline laser interferometer has been studied, which can be used for nanoscale displacement and vibration measurement. The method combined laser interferometer calibration with measurement to meet the needs of online calibration and state detection of long-baseline laser interferometer. Based on Phase Generated Carrier (PGC) demodulation technique, we add a calibration signal which we have already known to phase-modulated carrier, and according to the amplitude variations of calibration signal, we can achieve work condition monitoring of laser interferometer and measurement of environmental changes and the instruction of fluctuations. In the paper, a laser interferometer with 22-meter-long arm, resolution of 20pm and frequency range of DC ~ 200Hz used for displacement and vibration measurement was constructed, completed the online calibration software and hardware design, experimental results show that: by adding a calibration signal with frequency of 400Hz, amplitude 600nm, online condition monitoring of the laser interferometer can be realized. The advantages of this method is,that it can achieve online calibration for laser interferometer without increase burden in hardware, simplify the interferometer debugging process, improve operational efficiency, at the same time, it is of great significance and value to practical application of long-baseline laser interferometer.