菲涅耳非相干相关全息术(Fresnel incoherent correlation holography,FINCH)利用在空间光调制器(spatial light modulator,SLM)上加载双透镜模式对同一物点光分束自相干,并通过改变加载的相位因子得到不同的相移全息图.本系统利用SLM可分区编码调制特性,将FINCH成像中SLM上分三次加载的0?,120?,240?相位双透镜掩模各提取1/3组成一幅复合相移模式加载,并研究了三种相位分布方式对FINCH成像质量的影响.结果表明:三个相位在SLM上分布间隔越大,再现像越清晰.在此基础上,提出了一种新的掩模加载方式,在SLM加载透镜阵列,每一个相位因子对应一个双透镜,具有一个光轴.实验表明,通过这种加载方式,通过SLM后形成的三个相移图能够一次在电荷耦合器上记录,并且三个相移图不重叠,然后通过MATLAB编程计算将不同相移角度的全息图分别提取出来,通过三步相移计算合成一幅包含有物光波的复值全息图,最后通过数值再现算法重建待测样品.此系统可用于对光源相干性较低的实时成像系统,也为微小形变测量、动态物体的观测提供了新方法,为非相干数字全息术的发展提供了新思路.%Fresnel incoherent correlation holography (FINCH) is a relatively innovative technology, which can achieve inco-herent 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?, 120?, and 240?, 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 micro-organisms 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.
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