Resolution Improvement In FZA Lens-Less Camera By Synthesizing Images Captured With Different Mask-Sensor Distances

Abstract

Fresnel zone aperture (FZA) lens-less camera is a class of computational imaging systems that employs an FZA as a coded mask instead of an optical lens. FZA lens-less camera can perform fast deconvolution reconstruction and realize the re-focusing function. However, the reconstructed image’s spatial resolution is restricted by diffraction when using the conventional method derived from the geometrical optics model. In a previous study, we quantitatively analyzed the diffraction propagation between mask and sensor. Then we proposed a color-channel synthesis reconstruction method based on wave-optics theory. This study proposed a novel image reconstruction method without distorting the color information, comprehensively synthesizing two images captured with different mask-sensor distances to mitigate the diffraction influence and improve the image resolution. The numerical simulation and optical experiment results confirm that the proposed method can improve the spatial resolution to about two times that of the conventional method based on the geometrical optics model.