Research On Nonlinear Correction Method Of High-precision Wavelength Tuning Interference Phase Shift

With the rapid development of science and technology,large-aperture optical elements are widely used in many fields.As a main method for detecting large-aperture optical elements,phase-shift interferometry has been continuously developed and improved.The traditional phase-shift interference method is a hardware phase-shift method,such as pushing piezoelectric ceramics to achieve phase shift,etc.,but this method has a large measurement error for large-aperture optical elements;and the emergence of the wavelength-tuning phase shift method can overcome the problems of hardware phase shift,but there is phase shift nonlinearity error in wavelength tuned phase shift,which could affect the surface shape detection results.This dissertation mainly studies the phase shift correction in the process of wavelength tuning phase shift.The traditional one-dimensional time-domain Fourier transform phase shift correction method is to process a single sampling point to obtain the phase shift value.This dissertation adopts the phase shift correction method based on the extreme value function method,mainly by constructing the error function of each step phase shift,and obtaining the extreme value of the error function at each step phase to achieve accurate phase shift correction.At the same time,in order to reduce the measurement error,the effects of temperature,interference cavity length,and phase shift step size on phase shift correction results and surface shape measurement results were studied.The main research contents are as follows:First,the research status of phase-shift interferometry and wavelength-tuned phase-shift correction technology are described.The traditional phase shift correction method is compared with the phase shift correction method based on the extreme value function method for theoretical simulation and experimental comparison.The results show that the phase shift correction results obtained by this method are more accurate.In order to minimize the measurement error,the influence of temperature on the phase shift result was studied by ANSYS finite element analysis;meanwhile,the influence of interference cavity length and phase shift step size on the phase shift result was analyzed by matlab simulation.Then set up the experimental device to verify the above theoretical analysis,so as to obtain the best experimental measurement conditions.Based on this condition,the phase shift error was corrected with the phase-shift nonlinear correction method based on the extreme value function method,then using the wavelength-tuned phase-shift interferometer and zygo interferometer to realize the surface shape detection of optical plane mirror with a diameter of 100 mm.and by comparing the detection result with the measurement result of the absolute detection result.The results show that after the phase shift error is corrected,the measurement results of the wavelength-tuned phase shift interferometer are more consistent with the absolute detectionresults.Finally,the surface shape detection of the 320 mm large aperture optical plane mirror is completed.