Single-shot incoherent digital holography based on spatial light modulator

摘要

Fresnel incoherent correlation holography (FINCH) is a relatively innovative technology, which can achieve incoherent holograms by using the correlation between the object information and a Fresnel zone plate. In this method, the optical wave front scattered from an object propagates and is incident on a spatial light modulator which a phase mask is mounted on, and then the optical beam is split and phase shifted. The biggest advantage of the FINCH is that it can be matched with any standard optical imaging technology, which can realize microscopic imaging, telescopic imaging, spectroscopic imaging, etc. based on incoherent digital holography, and has important application prospect in remote sensing, astronomy, microscopy, and material analysis. In this paper, based on phase modulation characteristic of spatial light modulator, two types of masks are used. The first mask has an optical axis. And the results show that when the distribution intervals of the three phases on the spatial light modulator (SLM) are larger, the reconstruction image is clearer. On this basis, a new method of mode mounting on the SLM is put forward. The second mask has dual-lens array mode with three phases of 0 degrees, 120 degrees, and 240 degrees, and the three phases respectively correspond to their corresponding optical axis, which means that the mask has three optical axes. Both of the two masks can achieve the single-shot of FINCH. By comparing the two mask forms, we find that the field-of-view of the first mask is larger, which can image the entire resolution board; however, because the sub-phase shift holograms are mixed together and cannot be extracted, the quality of the reconstructed image is worse. The second one can extract three sub-holograms, and the reconstructed image has better quality; but because of smaller imaging field of view, it is suitable for the real-time imaging of microorganisms and objects. Experiments show that a compound digital hologram including three phase-shifting elements is recorded in charge-coupled device in this way. Three sub-holograms with different phase shift angles are extracted from the compound hologram, and there is no overlapping among the three phase shift holograms. Therefore, the three-phase-shifting technique is usually employed. The sample is reconstructed by numerical reconstruction algorithm. The proposed method may be useful in dynamic process real-time measurement and three-dimensional analysis of the object, and thus providing a new way to promote the development of incoherent digital holography.