3D打印衍射元件的高分辨太赫兹计算机辅助层析成像研究(特邀)  

High-resolution Terahertz Computed Tomography Using 3D Printed Diffractive Elements(Invited)

作　　者：王大勇[1,2] 宁冉 金晓宇 戎路 赵洁[1,2] 王云新 林述锋[1,2] WANG Dayong;NING Ran;JIN Xiaoyu;RONG Lu;ZHAO Jie;WANG Yunxin;LIN Shufeng(Department of Physics and Optoelectronics Engineering,Faculty of Science,Beijing University of Technology,Beijing 100124,China;Beijing Engineering Research Center of Precision Measurement Technology and Instruments,Beijing 100124,China)

机构地区：[1]北京工业大学理学部物理与光电工程系,北京100124 [2]北京市精密测控技术与仪器工程技术研究中心,北京100124

出　　处：《光子学报》2022年第7期107-118,共12页Acta Photonica Sinica

基　　金：国家自然科学基金(Nos.62075001,62175004);北京市教委科技重点项目(No.KZ202010005008)。

摘　　要：提出了一种由三维打印技术制作的用于0.3 THz波束调控的二元相位型衍射透镜,可产生轴向焦深为25 mm、腰斑直径为1 mm的太赫兹聚焦波束。将该聚焦波束应用于连续太赫兹波计算机辅助层析成像,不仅将成像分辨率提高到1.5 mm,而且由于扩大了系统景深,提高了成像保真度。这类利用三维打印技术制作的二元衍射元件可有效应用于低频太赫兹波段的光束调控,为太赫兹成像系统的性能优化以及聚焦元件的设计制备提供一种有效途径。Terahertz waves, located between the millimeter waves and infrared radiation in the electromagnetic spectrum,have unique penetration and imaging properties for diverse application scenarios.Terahertz computed tomography,derived from its ancestor in the X-ray domain,is known as a major transmissive three-dimensional terahertz imaging method to obtain the inner geometrical structure of the sample as well as its three-dimensional distribution of either absorption coefficient or refractive index. In this study,a three-dimensional printing binary diffraction lens is proposed to generate a convergent terahertz beam with a focal depth of 25 mm and a waist diameter of 1 mm,which enhances the resolution and reconstruction fidelity of a 0.3 terahertz computed tomographic system. For this terahertz binary diffractive lens,its focal depth is modulated by sets of concentric rings with standard step height and different integer multiples of step width. The phase delays caused by steps of binary heights are 0 and π,respectively. A simulated annealing algorithm is applied to find the premium structure of this annular phase modulator,in which the full width at half maximum of the focal spot as well as the maximum available depth-of-focus are selected as the constraints. This diffractive lens is constituted by 20 sets of concentric rings with minimum width of 0.5 mm,with a total effective diameter of 25 mm. It is fabricated by a threedimensional printer with a precision of 0.1 mm using a photosensitive resin material. Its refractive index and transmissive ratio are 1.66 and 82%, respectively. The step height is therefore set to 0.81 mm,corresponding to an optical path difference of half wavelength. In terms of depth-of-focus,both theoretical value and experimental value are approximately 25 mm,the latter of which is measured by an array microbolometer. The theoretical full width at half maximum of the focus spot is 1 mm while experimental one is approximately 0.8 mm. The disparity comes from incomplete coverage of the incident be

关 键 词：信息光学 太赫兹计算机辅助层析 光束调控 二元衍射透镜 三维打印技术 

分 类 号：O438.2[机械工程—光学工程]