Park I S, Middleton R J C, Coggrave C R, Ruiz P D, Coupland J M
Appl Opt. 2018 Jan 1;57(1):A235-A241. doi: 10.1364/AO.57.00A235.
A hologram is a recording of the interference between an unknown object wave and a coherent reference wave. Providing the object and reference waves are sufficiently separated in some region of space and the reference beam is known, a high-fidelity reconstruction of the object wave is possible. In traditional optical holography, high-quality reconstruction is achieved by careful reillumination of the holographic plate with the exact same reference wave that was used at the recording stage. To reconstruct high-quality digital holograms the exact parameters of the reference wave must be known mathematically. This paper discusses a technique that obtains the mathematical parameters that characterize a strongly divergent reference wave that originates from a fiber source in a new compact digital holographic camera. This is a lensless design that is similar in principle to a Fourier hologram, but because of the large numerical aperture, the usual paraxial approximations cannot be applied and the Fourier relationship is inexact. To characterize the reference wave, recordings of quasi-planar object waves are made at various angles of incidence using a Dammann grating. An optimization process is then used to find the reference wave that reconstructs a stigmatic image of the object wave regardless of the angle of incidence.
全息图是未知物波与相干参考波之间干涉的记录。如果物波和参考波在空间的某些区域充分分离且参考光束已知，那么就有可能对物波进行高保真重建。在传统光学全息术中，通过用记录阶段使用的完全相同的参考波仔细重新照射全息图板来实现高质量重建。为了重建高质量的数字全息图，必须从数学上知道参考波的精确参数。本文讨论了一种技术，该技术可获取表征源自新型紧凑型数字全息相机中光纤源的强发散参考波的数学参数。这是一种无透镜设计，其原理类似于傅里叶全息图，但由于数值孔径较大，通常的傍轴近似不能应用，且傅里叶关系不准确。为了表征参考波，使用达曼光栅在不同入射角下对准平面物波进行记录。然后使用优化过程来找到能重建物波的消像散图像的参考波，而不管入射角如何。
