Design of a four-zone amplitude random mask for lensless imaging systems

Lensless camera is an inventional optical imaging system that can work without a typical lens system. Usually, a lensless camera works with a mask. The mask can be an amplitude one or a phase one. Considering the cost of processing, amplitude mask is preferred for its common processing method. In this paper, we find a phenomena called 'mask degeneration'. Such a situation happens when the lensless camera works in a real scene. The realworking mask pattern is not the one designed originally, it is a composite pattern in which the mask patterns of different displacements are superimposed over one another. A simulation about the mask degeneration is operated and the simulation satisfies well with the experiment. Based on these theories, a four-zone amplitude random mask for lensless imaging systems is designed. This random mask can work well in a situation when the mask degenerates. What's more, the final result of one shoot for the lensless camera has been enlarged to almost twice the size by composing the four zones' output pictures.