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中国物理学会期刊

针对微尺寸X射线源的非相干全息层析成像

CSTR: 32037.14.aps.72.20230920

Tomographic incoherent holography for microscale X-ray source

CSTR: 32037.14.aps.72.20230920
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  • 现阶段在惯性约束聚变实验中, 无论是对黑腔等离子体或是内爆靶丸区域的单次成像诊断都无法分辨深度方向上的辐射强度信息, 即探测器获取的图像均是沿探测方向上的强度积分. 本文介绍了一种利用非相干全息技术对微尺寸X射线源的层析成像方式. 所述的非相干全息成像技术具有将光源的三维空间信息编码并压缩至二维全息图的成像机制, 再结合基于压缩感知的全息图重建算法, 能够从二维全息图中恢复出沿探测方向不同物距上光强的二维分布情况. 为了验证该成像方案的可行性, 本文模拟了轴向长度为16 mm的光源非相干全息成像过程, 并通过压缩感知算法重建模拟生成的非相干全息图, 得到间距为4 mm的层析光强分布结果.

     

    At present, in the experiment on inertial confinement fusion (ICF), no single imaging diagnosis of the black cavity plasma or the implosion target region can distinguish the emission intensity information in the depth direction, that is, the images acquired by the detector are intensity integral along the detection direction. In this paper, a tomographic imaging method using incoherent holography for microscale X-ray source is introduced. The incoherent holographic imaging technology has an imaging mechanism that encodes and compresses the three-dimensional space information of the light source into a two-dimensional hologram. In the theoretical part, we examine the imaging mechanism of incoherent holographic tomography. Then the compress sensing model which is appropriate for this incoherent tomography is investigated. Combined with the hologram reconstruction algorithm based on compress sensing, the two-dimensional distributions of light intensity at different object distances along the detection direction can be recovered from the two-dimensional hologram. In order to verify the feasibility of this imaging scheme, we simulate the incoherent holographic imaging process of a light source with an axial length of 16 mm, and obtain the tomography light intensity distribution result with a spacing of 4 mm by reconstructing the corresponding incoherent hologram through using the backpropagation algorithms, Wiener filtering algorithm, and compress sensing algorithm. All reconstruction methods mentioned above can recover the corresponding letter light source at a certain object distance, indicating the potential of incoherent holographic technology for three-dimensional imaging. For the backpropagation reconstruction image, there is a large amount of series noise at the edge of the light source signal, which affects signal recognition in practical applications. Although the Wiener filtering algorithm can recognize the image signal to some extent, the low contrast of the reconstructed image results in the distribution of target source strength mixed with background noise. Compared with the algorithm based on the Wiener filtering and backpropagation, compress sensing theory provides a more professional technique for the ill-condition problem. Results from compress sensing reconstruction show that the crosstalk noise is significantly reduced, and the intensity distribution on the objective plane of the light source is basically concentrated in the signal area. The peak-signal-to-noise ratio of reconstructed image is continuously optimized as the number of iterations increases. Besides, the axial and horizontal resolution caused by the innermost ring radius of Fresnel zone plate are also analyzed, indicating that a shorter innermost ring radius can improve the horizontal resolution, bur reduce the axial resolution.

     

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