Enhanced reconstruction of spatially incoherent digital holograms using synthetic point spread holograms

Incoherent holography systems, in general, require complicated optical configurations to generate two mutually coherent object beams and create a stable self-interference hologram [1]. The invention of Fresnel incoherent correlation holography (FINCH) created possibilities to implement incoherent holography methods autonomously and also integrated them into other imaging methods easily [2, 3]. Coded aperture imaging methods (CAI) which were developed in the 20^th century, have been rebooted during the last five years for three-dimensional [4-6] and four-dimensional imaging [7] after the development of novel computational reconstruction methods. In CAI methods, the light from an object is scattered by a coded phase mask, and the scattered intensity distribution is recorded. The object intensity distributions are reconstructed using point spread holograms (PSHs) pre-recorded using a point object at all depths and spectrum using the same scatterer under identical experimental conditions. In FINCH, new imaging characteristics can be introduced by modulating the object wave by the corresponding phase function and interfering it with the unmodulated object wave [8]. This is because, in FINCH, the reconstruction mechanism by computational Fresnel back propagation does not change with respect to the modulating function. Therefore, the relative variations of the new optical fields are manifested during reconstruction. In CAI methods, however, the above approach cannot work as the reconstruction is carried out by cross-correlation with the PSH, which is dependent upon the modulation function. Consequently, the beam characteristics were not manifested during reconstruction [9]. In this study, we have developed a post-processing approach involving synthetic PSHs generated using a new iterative algorithm that can be applied to both FINCH-like as well as CAI methods efficiently. We believe that the proposed computational approach is a valuable tool for introducing unconventional imaging characteristics virtually to imaging systems [10].

References

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