Terahertz coaxial holographic imaging system and imaging method based on multiple recording distances

Abstract

The invention discloses a terahertz coaxial holographic imaging system and an imaging method based on multiple recording distances. The invention particularly relates to an iterative reproduction method based on multiple recording distances and belongs to the technical field of the terahertz imaging technology. The invention aims to solve the problem of conjugate images and the zero-level image interference during the terahertz coaxial digital holographic imaging process. The imaging includes two processes: namely hologram recording and complex amplitude reproducing. During the hologram recording process, a hologram of multiple recording distances and the acquisition of the illumination light are realized through horizontally moving a detector along the direction of an optical axis. During the complex amplitude reproducing process, the complex-amplitude diffraction propagation is respectively conducted for the hologram and the illumination light sequentially between every two recording surfaces, and the recording value of each recording surface is updated as a constraint condition for the complex amplitude. The phase information of the hologram and the illumination light is restored through the repeated round-trip iteration operation. Finally, the high-fidelity object surface complex-amplitude distribution without conjugate images and the zero-level image interference can be obtained.

Description

technical field [0001] The invention belongs to the technical field of holographic imaging, and relates to a coaxial digital holographic imaging method, in particular to a coaxial digital holographic imaging method using iterative calculation. Background technique [0002] Terahertz digital holographic imaging has attracted more and more attention in the field of terahertz imaging due to its advantages of lossless, label-free, lens-free, and dynamic full-field acquisition of quantitative amplitude and phase information. Coaxial digital holography is very suitable for long wavelength, immature components, In the terahertz field where the detector spatial frequency is not high and the size of the area array is small, its disadvantage is that there are conjugate images and zero-order image interference in the reconstruction results. In order to suppress the conjugate image in the reconstruction results, various phase restoration methods are proposed to obtain the complex ampli...

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Problems solved by technology

[0004] Although the above coaxial digital holographic phase restoration imaging method eliminates the twin images in the detection sample image through iterative data analysis, the iterative method adopted by the coaxial digital holographic phase restoration imaging method to solve the problem of twin images is mainly to first acquire A hologram and background image at a recording surface, and multiple iterations are performed between the recording surface and the object surface according to this hologram and background image, thereby eliminating twin images; however, it is precisely because the iteration of the imaging method is in It is carried out between the recording surface and the object plane, so it needs the support of the object plane. The imaging target must meet certain conditions to use this imaging method and ensure its imaging effect. For those imaging targets that do not meet the conditions, due to the calculation process There are constraints on the object, so it is difficult to effectively implement the object plane constraints for these more special imaging targets, resulting in the degradation of the imaging structure, and the final reconstructed complex amplitude image of the object has a large error

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