Enhanced Autofocusing in Optical Scanning Holography Based on Hologram Decomposition

Optical scanning holography is a compact and powerful method for capturing hologram of a wide three-dimensional (3-D) view scene. After a hologram has been taken, it is often necessary to determine the locations of the focal plane on which the objects are residing, so that the 3-D scene can be numerically reconstructed for further analysis or processing. Recent research has shown that automatic detection of the depth (focal plane) of objects represented in a hologram can be conducted with entropy minimization method. Despite the success, the method could fail if the entropy information of objects in a hologram are interfering with each other. In this paper, we propose a method based on the hologram decomposition to overcome this problem. Briefly, the hologram is decomposed into subholograms and the focal plane distance is determined separately for each subobject. Simulation results reveal that our proposed method has good accuracy and reliability.