Research On The Diffraction Efficiency Of Multi-Layer Diffractive Optical Elements

Diffraction efficiency is an important characteristic of the diffractive optical elements (DOEs). The diffraction efficiency directly affects the MTF of the hybrid refractive-difrractive systems. Therefore, in this paper an in-depth study is given on the diffraction efficiency characteristics of the diffractive optical elements.In the approximation of scalar theory of diffraction, based on the theory of phase grating, the general formula that is used to calculate the diffraction efficiency of the phase grating is deduced, and then the diffraction efficiency general formulas of the single-layer DOE, the harmonic diffractive optical elements, the two-layer DOEs and the three-layer DOEs are respectively get.Through analyzing the diffraction efficiency characteristics of the above diffractive optical elements, the advantages and disadvantages of various diffractive optical elements are pointed out and the application restrictions are presented as well. At the same time the methods of improving the diffraction efficiency and increasing the incident angle on the diffraction surface is introduced.In the last part of the paper, using the negative dispersion properties and the apochromatism of the diffractive optical elements, two hybrid refractive-diffractive systems are respectively designed. It not only can reduce the weight and volume of the system, but also can improve the quality of image greatly.