Coherent modulation imaging realized by coaxial shift of an amplitude mask

Abstract

As a lensless imaging technology, coherent modulation imaging (CMI) can reconstruct the complex amplitude of the object from the measured intensity distribution. In this paper, a new CMI scheme is proposed. A random binary amplitude mask is introduced between the light source and the object. The incident light is modulated by the mask and the speckle field is generated to illuminate the object. The object can then be accurately recovered with the iterative phase retrieval algorithm by means of moving the mask several times in the axial direction and recording the corresponding diffraction pattern. Compared to the existing CMI schemes, the experimental system of the proposed method is simple and compact. No spatial light modulator or phase plate is required. Both numerical simulations and experiments are performed to verify the feasibility of the method. The influence of moving times, moving interval and pixel size of the mask on the reconstruction accuracy are analyzed in detail. In addition, the image registration encountered in the experiment is discussed.