A high precision phase extraction method in heterodyne interferometer based on FPGA

Abstract

The high-precision phase extraction method directly determines the final measurement performance of the heterodyne laser interferometer. This paper proposes a digital quadrature phase-locked (DQPL) method with sub-nanometer precision based on FPGA hardware and compiled on the LABVIEW FPGA platform. DQPL method can accurately extract the phase difference of the two optical signals in the heterodyne laser interferometer. The validity and stability of the method have been verified by simulations and experiments. The experimentally obtained measurement resolution is 0.074 nm, and the measurement standard deviation obtained by the Monte Carlo method is 0.22 nm.

A Picometre-Level Resolution Test Method without Nonlinearity for Heterodyne Interferometer Measurement Electronics

“…Secondly, different phase calculation principles will also result in differences in resolution. At present, many different phase unwrapping methods [17][18][19], such as pulse filling and phase-locked amplification, have been proposed to improve resolution. Finally, there is a form of accommodation between the above two factors; that is, the signal-to-noise ratio of the electrical signal from the photodetector should be sufficient to achieve the highest resolution of the phase meter.…”

“…The currently used test methods can be divided into three categories, namely, electrical methods, methods based on the PZT stage, and equivalent methods. Within electrical methods, a signal generator is used to offer electrical signals as ideal interference signals [8,9,12,[17][18][19] to directly test the resolution of the phase meter. However, it is evident that this method ignores the influence of noise on the resolution during the photoelectric conversion process.…”