Annular multi-focal-phase mask multiplexing based large depth of field imaging by interferenceless coded aperture correlation holography.

Extending depth-of-field (DOF) of the imaging system without modifying the structure and sacrificing imaging performances of the optical system is of great significance to broaden the capability and application of the imaging system. In this paper, the interferenceless coded aperture correlation holography(I-COACH) is developed to be a large-depth incoherent imaging system by employing an annular multi-focal coded phase mask (AM-CPM). Based on the analyses of axial defocus characteristics in I-COACH, the defocus compensation function is defined, the AM-CPM is designed and multiplexed on the system optical pupil, which plays the role of a gradual lens. In AM-CPM, multi-annular zones with different focal lengths are used to compensate different axial defocus aberrations and adjacent annular zones have symmetric axial defocus aberration correction capability according to the imaging characteristics of the system. The simulations and experimental results fully demonstrate that the axial point spread function distribution of the system obtained by AM-CPM is continuous and the development method enables the extension of the DOF of the I-COACH system by only single exposure point spread hologram. This solution is expected to provide great potential in the field of microscopic imaging and other fields of that based on I-COACH system.