Impact of the Imperfect Polarizing-Beam Splitter and Quarter-Wave Plate and Non-Ideal Laser Beam on the Accuracy of Nano-Displacement Laser Encoder

Abstract

Abstract:In this paper, periodic nonlinear error of laser encoder for nano-displacement measurement caused by imperfection of polarizing-beam splitter (PBS), quarter-wave plate (QWP), and laser source is modeled by using the Jones matrix analysis. The results reveal that the peak-topeak nonlinearity resulting from imperfect PBS and QWP, and non-orthogonality and ellipticity of the polarized laser beams is obtained as 14.82 nm. Also, considering typical values of transmittance and reflectance coefficients of PBS and different retardation errors of QWP, the first-order and second-order nonlinearities are respectively revealed resulting from imperfect PBS and QWP.Keywords: Jones matrix, nano-displacement, nonlinearity error, polarizing-beam splitter, nanometrology, quarter-wave plate.