Sinusoidal wavelength-scanning interferometer with double feedback control for real-time measurement of one-dimensional step-profile

Advanced materials and devices for sensing and imaging : 17-18 October 2002, Shanghai, China. : Oct 2002, Shanghai, ChinaAn optical path difference (OPD) and the amplitude of sinusoidal wavelength-scanning are controlled with double feedback control system in an interferometer, so that a ruler marking every wavelength and a ruler with scales smaller than a wavelength are generated. These two rulers enable us to measure an OPD longer than a wavelength in real time. A linear CCD image sensor is used to measure one-dimensional step-profiles in real-time. Two different step profiles with a step height of 1 μm and 20 μm, respectively, are measured with the measurement error less than 8 nm. Measuring time for one measuring point is 0.04 s