远心同-离轴混合数字全息高分辨率重建方法

Telecentric in-line-and-off-axis hybrid digital holographic high-resolution reconstruction method

现存的同-离轴混合数字全息技术可同时解决同轴全息共轭像消除困难和离轴全息分辨率受限的问题,但需预测衍射距离,不仅复杂耗时,且精度有限;而远心成像技术可获得非衍射图像,无需预测衍射距离,并具有可消除球面像差和散焦像差等特性.因此,本文将远心成像技术引入同-离轴混合数字全息技术中,提出一种远心同-离轴混合数字全息高分辨率重建方法.该方法利用远心同-离轴混合数字全息系统,分别采集聚焦的离轴全息图和同轴全息图;进而将离轴全息图获得的低分辨率相位信息与同轴全息图获得的振幅信息相复合,作为迭代恢复过程的物光复振幅初始值,并分别在空域和频域进行约束迭代,实现高分辨率重建.实验结果表明,该方法无需衍射距离等先验信息,便可很好地消除共轭像和系统畸变的干扰,并可充分利用图像传感器的空间带宽积,实现物体的高分辨率重建.

In-line digital holography usually employs a phase retrieval algorithm to decouple the phase information but fails to eliminate the unwanted DC and twin image terms when the measured sample does not agree with the sparsity.While the off-axis digital holography can efficiently remove the unwanted image terms but can not reserve the high frequencies of the sample to realize high resolution.The in-line-and-off-axis hybrid digital holography was then developed to provide a relatively high resolution digital holographic imaging without considering the effect of the unwanted terms.In other words,the in-line-and-off-axis hybrid digital holography merges all of the best virtues of the mentioned-above methods in an efficient and elegant way.However,this state-of-the-art method requires prior knowledge about the diffraction distance,which results in time-consuming and low accuracy.In other sense,telecentric technology can realize non-diffractive imaging without the knowledge about the diffraction distance or spherical aberration or defocusing aberration.Therefore,in this paper,a novel in-line-and-off-axis hybrid digital holography is proposed by introducing telecentric imaging architecture,and the corresponding reconstruction method is further proposed by utilizing constrained iterative approach.In this method,telecentric in-line-and-off-axis hybrid digital holography is first used to acquire focused off-axis and in-line holograms,respectively.The low resolution phase information is reconstructed from the off-axis hologram by using Fourier transform method with the help of the sample-free off-axis hologram,and then multiplexed with the amplitude information obtained from the in-line hologram to act as the initial complex amplitude in the iterative recovery process.As a result,constrained iterations are carried out in the spatial domain and frequency domain to realize high resolution and high speed reconstruction.After simulations,we build an experimental setup and demonstrate the operation of the method with USAF resolution target,onion cells and bee wings.Both the simulation and experimental results show that the proposed method can require no prior knowledge to suppress the phase disturbance caused by the unwanted image terms and optical aberrations,resulting in high speed and full utilization of spatial bandwidth product of the digital camera to yield high resolution reconstruction.We hope that the proposed method will have most practical applications in the case where large resolution,high speed and good quality are needed.