Research On Micromorphology Measurement Technology Based On Swept Interference

Ultra-precision surface is widely used in modern manufacturing industry.The performance of the workpiece can be evaluated by measuring the microtopography of the surface.Optical interferometry has great potential because of its non-contact,high measurement accuracy and high speed.The sweep interferometry is more suitable for online detection because there is no 2? phase ambiguity problem of phase shift interferometry and no measurement error introduced by mechanical scanning.In this paper,microtopography measurement technology based on frequency sweep interference is studied,and its principle analysis and expe rimental verification are carried out.The main research contents are as follows:(1)Design the scheme of microtopography measurement system based on frequency sweep interference,including wavelength adjustable light source module,micro interferometer module and acquisition synchronization module,and establish the mathematical model of the system to theoretically analyze the feasibility of the system;(2)Study fringe analysis algorithm based on fast Fourier transform(FFT)and inverse FFT,tilt correct ion algorithm based on Zernike polynomial fitting,and step height assessment algorithm based on ISO 5436-1 standard;(3)Build a micro-morphology measurement system based on swept interference,and study the nonlinear error of the acousto-optic tunable filter.Experiments on planar mirrors show that different window widths and discarded phase edge points will affect the measurement accuracy.The optimal parameters of the algorithm are determined according to the results of the plane mirror test.and the optimal parameters were used for the test of standard step samples.The uncertainty of step measurement was 2.2nm(k=2),achieving nanoscale precision.