编码掩模红外成像系统的建模与指标分析

Modeling and Analysis of Coded Aperturelnfrared Imaging Systems

一种编码掩模红外成像系统的建模方法,模型由两个功能部分组成:编码掩模和理想透镜组成的成像部分以及实际透镜的非理想成像部分.其中,第一部分可表达为掩模按照掩模到镜头前平面的距离发生菲涅尔衍射的作用,第二部分可表达为平行光照射光瞳结构并按照同样的距离发生菲涅尔衍射后的聚焦结果.因此,编码掩模成像系统的点扩散函数PSF可以由编码掩模的衍射模式和实际透镜的PSF组成.根据编码掩模的评价函数以及系统PSF的估计,研究发现,基于Dammann光栅结构的编码掩模模式对于直接成像和图像恢复重建具有比较均衡的性能.实验结果表明,对于直接成像的编码掩模成像系统,其掩模应该具有较强的随机性,而对于图像重建系统需具有较多的周期性结构.

The model of coded aperture infrared imaging systems consists of two functional components,the coded mask imaging with ideal focused lenses and the imperfection of practical lenses.The first part can be represented by mask＇s Fresnel diffraction,which transmitted from mask to front lens.The other part is pupil＇s Fresnel diffraction transmitted in the same distance.The system＇s point spread function（PSF） can then be represented by the diffraction pattern of the mask and the PSF of the practical lenses.Imaging results with inclined plane waves are also analyzed to achieve the variation of PSF within the view field.According to indices for mask pattern evaluation and system＇s PSF assessment,mask pattern we proposed based on Dammann grating has a balanced performance for direct imaging and imaging reconstruction.Experimental results show that mask pattern for direct imaging should have more random structures,while more periodic structures in system with image reconstruction.