Error analysis of interference signal modulation and demodulation in phase freezing technique

ZHANG Xiaoqing; JIA Yudong; CAO Wenjuan

doi:10.7510/jgjs.issn.1001-3806.2015.04.016

In order to reduce measurement errors with a laser feedback interference system measuring micro displacements of moving objects based on phase freezing technique, system errors induced by intervals of phase shift and vibrating amplitudes of reflecting surface were analyzed theoretically by means of MATLAB numerical simulation, interpolation and curve fit. In system experiments, interference signals produced by moving objects were collected and sampled by phase freezing principle so as to obtain multiple curves of optical power. Feature points were marked on the optical power curves to judge moving direction and reconstruct micro-displacement curves. Polynomial fitting based on the reconstructed micro displacement curves improved system measurement precision. Experimental results show that measurement resolution is superior to /20 (77.5nm) when fixed interval of phase shift is /5 and wavelength of laser is 1550nm. The maximum absolute error of actual measurement of micro-displacements is 47.98nm and the average value of peak-peak errors is less than 1nm. Phase freezing technique provides a new solution for laser feedback interferometer system to identify directions and realize high precision measurement of micro-displacements.

Error analysis of interference signal modulation and demodulation in phase freezing technique

1. Department of Measurement and Control Technology and Instrumentation, School of Instrumentation Science & Opto-electronic Engineering, Beijing Information Science and Technology University, Beijing 100192, China;

2. Key Laboratory of Modern Measurement & Control Technology of Ministry of Education, Beijing Information Science and Technology University, Beijing 100192, China

Received Date: 2014-06-06

Accepted Date: 2014-07-11

Available Online: 2015-07-25

Abstract: In order to reduce measurement errors with a laser feedback interference system measuring micro displacements of moving objects based on phase freezing technique, system errors induced by intervals of phase shift and vibrating amplitudes of reflecting surface were analyzed theoretically by means of MATLAB numerical simulation, interpolation and curve fit. In system experiments, interference signals produced by moving objects were collected and sampled by phase freezing principle so as to obtain multiple curves of optical power. Feature points were marked on the optical power curves to judge moving direction and reconstruct micro-displacement curves. Polynomial fitting based on the reconstructed micro displacement curves improved system measurement precision. Experimental results show that measurement resolution is superior to /20 (77.5nm) when fixed interval of phase shift is /5 and wavelength of laser is 1550nm. The maximum absolute error of actual measurement of micro-displacements is 47.98nm and the average value of peak-peak errors is less than 1nm. Phase freezing technique provides a new solution for laser feedback interferometer system to identify directions and realize high precision measurement of micro-displacements.

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Reference (14)

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Error analysis of interference signal modulation and demodulation in phase freezing technique

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