Research Of The Design Method Of Diffractive Optical Elements Based On The Ravleigh-Sommerfeld Diffraction Theory

Traditional diffractive optical elements(DOE)are limited by the sampling method and the forward and backward diffiraction algorithms.Therefore,they usually work in the paraxial and far field and their imaging surface is flat.With the expansion of the application area of DOE,the requirements for the working area of DOE have begun to change.For example,they work in the near field and have large diffraction angles,or their imaging surface are curved.Based on the Rayleigh-Sommerfeld diffraction theory,the design method for the near-field DOE with large diffraction angle which the correlation coefficient between the actual diffraction pattern and the target diffraction pattern is obviously better than the existing design method of the DOE with large diffraction angle in the near-field region;the design method of DOE for large depth curved surface imaging which the ratio of its depth to the farthest working distance is more than 0.3.The main research work includes:1.Under the condition of large diffraction angle,the relation of space position of sampling points between the DOE surface and the imaging surface is studied based on the theory of coherent imaging when the iterative algorithm is used to design diffractive optical elements.2.By reducing the dimensions of discrete matrix of the light field information and the point spread function,the forward and backward diffraction algorithms without far-field and paraxial approximation is obtained.3.Through the above sampling method and the forward and backward diffraction algorithms are used to improve the GS algorithm,the design method for the near-field DOE with large diffraction angle is obtained,and the design steps and cases are given.4.Under the condition that the imaging surface is curved,the relation of space position of sampling points between the DOE surface and the imaging surface is studied based on the theory of coherent imaging when the iterative algorithm is used to design diffractive optical elements.5.The design method for the near-field DOE with large diffraction angle is improved by the above sampling method.Then the design method of DOE for curved surface imaging is obtained.This method is suitable for designing the DOE for large depth curved surface imaging.And the design steps and cases are given,6.Based on the relation of space position of sampling points between the DOE surface and the imaging surface,the variation of imaging resolution with diffraction angle and curved surface is studied.