Spatial coherence analysis for optical scanning holography.

In optical scanning holography (OSH), the system can be operated in coherent mode by using a pinhole detector, or in incoherent mode by using a spatially integrating detector. In the coherent mode, the three-dimensional (3D) amplitude transparency of an object is recorded and thus the phase of the object can be retrieved. On the other hand, it is the 3D intensity transparency of the object recorded in the incoherent mode and thus the speckle can be suppressed. OSH in both coherence modes has been well investigated. However, there is no discussion on the case between the coherent mode and incoherent mode, namely, the partial-coherent mode. In this paper, we derived for the first time, to the best of our knowledge, the formula of OSH in various modes of coherence. We found the detector in OSH plays the role of a kind of filter for the field. The retrieved amplitude transparency of the object is thus nonlinearly processed by the mask function of the detector. Consequently, the reconstructed image cannot benefit from the implementation of the partial-coherent mode. On the contrary, significant artifacts usually appear among the reconstructed image and thus the image quality degrades.