Reduction of effect of DOE's diffraction efficiency via optical-digital joint design

Abstract

Diffractive optical elements can simplify the system structure due to their unique negative dispersion properties for imaging systems. It is difficult for single-layer diffractive optical elements (SLDOEs) to maintain high diffraction efficiency over a wide waveband. We propose a design method using optical–digital joint design to reduce the image blur caused by low diffraction efficiency. This method directly and clearly images in the waveband of higher diffraction efficiency, and indirectly images through imaging reconstruction in the waveband of lower diffraction efficiency. A point spread function model considering the effect of roughness on diffraction efficiency during processing is proposed to recovery the blurred image. We design a dual waveband infrared imaging system using SLDOE for 3.7μm~4.8μm and 7.7μm~10μm. The MTF for each field of view at 17 lp/mm are respectively greater than 0.7 and 0.5. The reconstructed image of LWIR is obviously subjectively clearer than the original image, and multiple evaluation function values are better than the original image. The results show that the design method can improve the image blur caused by reduced diffraction efficiency and SLDOEs can be applied to the design of dual waveband infrared imaging systems.