Adaptive Interferometer Testing Technology With Dymanic Comsenption Based On SLM

With the improvement of optical processing level,the application of aspheric surface in optical design has developed rapidly in recent thirty years,and it is gradually replacing the spherical mirror as the mainstream of optical system.Accordingly,the surface error detection of aspheric optical component is more difficult than that of spherical component,and has more restrictions.Therefore,it is necessary to add the corresponding compensator in optical testing system so that the detection results are completely determined by the surface difference between the measured surface and the ideal aspheric surface.At present,the optical compensators used for aspheric and freeform surface detection are mainly static compensator such as compensation lens group and computer-generated hologram.The characteristics of such compensators are that the structure is calculated in advance according to the detection optical path and customized production,so the production cycle of the obtained compensators is long and has no reusability,which greatly increases the detection cost of aspheric optical components.At present,the problems that need to be solved in the field of optical interference detection mainly include two aspects.One is the detection demand for optical surfaces with large curvature and large aperture which makes the sampling frequency of interference fringes beyond the limit.This situation puts forward higher requirements for the dynamic range of existing compensation methods and the spatial frequency of image sampling.This demand promotes the application of super-resolution imaging in detection technology and the development of multiple compensation technology.The other is to make the detection process and system universal and intelligent based on the dynamic compensation,which breaks the limitation of ' one to one' customized manufacturing of compensators,reduces manufacturing costs and improves detection efficiency.Based on the requirements of intelligent dynamic detection in the field of interference detection,this thesis introduces the idea of real-time wavefront correction technology in the field of adaptive optics.Based on the dynamic modulation ability of spatial light modulator,combined with the aberration theory as the basis of system evaluation,a dynamic interference detection technology that can realize adaptive compensation for unknown surfaces is proposed.Specific contents include :(1)The mathematical principle and implementation method of stochastic parallel gradient descent algorithm in adaptive optics are studied.The Zernike polynomial fitting method of aberration in the interference system is analyzed in the frequency domain.The performance parameters that have a clear response to each change of Zernike polynomial are selected as the cost function of the system optimization,and the Adam optimizer is introduced to enhance the convergence efficiency of the algorithm,so that the SPGD algorithm is suitable for the technical requirements of interference detection.(2)The related algorithms are written to test the ability of the algorithm to optimize the wavefront compensation,and the system simulation is carried out based on the optical simulation software to verify the rationality of the cost function and the convergence ability of the algorithm.The algorithm performance under different fitting terms and different target surfaces is compared and analyzed.The RMS value of the wavefront aberration after compensation can reach the sub-wavelength level without a large number of high-order aberrations,which basically meets the zero-position condition.(3)The optical path is built to verify the proposed dynamic interference detection scheme.The surface shape of the reflective liquid crystal spatial light modulator is measured,and the aberration generated by its own surface shape is corrected using the algorithm proposed in this thesis.At the same time,the accuracy of the phase modulation is calibrated,and the curve of the phase modulation response is drawn to realize the compensation of the modulation error.Finally,the interferogram basically meets the zero detection condition.