Two-color heterodyne optical zooming method for nanometer measurement

A two-color heterodyne optical zooming method is proposed to improve the signal-to-noise ratio in nanometer interferometry. By phase-compensation technique, a small displacement in the sensing arm results in an enlarged displacement in the reference arm. The latter displacement can be measured easily and accurately. The zoom factor K, which is determined by the two wavelengths that produce the synthetic wavelength, can be easily changed. Using the heterodyne technique, phase changes caused by the displacement can be measured with high accuracy. A linearity of 0.9997 and a standard deviation of 1.8 nm were experimentally obtained in a measurement range of 0.17 mum. (C) 2004 American Institute of Physics.