摘要
太赫兹波对非极性材料具有良好的穿透性,与太赫兹波强度成像相比,相衬成像能够更好的反映物体的内部结构。本文提出了基于TPX透镜的连续太赫兹波像面数字全息相衬成像方法,研究了全息记录和再现过程,利用曲面拟合畸变校正去除TPX透镜引入的二次相位畸变。实验搭建了太赫兹像面数字全息成像系统,利用振幅型西门子星样品对系统的成像分辨率进行了定量分析,同时对有机材料和生物样品两种相位型样品进行成像,实验验证了该相衬成像方法的有效性。在太赫兹波段引入像面成像,有利于提高太赫兹成像分辨率及成像质量,在生物医学成像、无损检测等领域具有广泛的应用前景。
The wavelength of terahertz wave is between those of infrared wave and microwave,with the characteristics of penetration,strong water absorption,and low photon energy,etc. Terahertz imaging has been are widely used in biomedical imaging,anti-terrorism security and non-destructive testing and other fields. The good penetration of terahertz wave is beneficial to detect the internal structure of objects. Phasecontrast imaging can better reflect the internal structure of objects,compared with simple terahertz intensity imaging. Continuous terahertz wave phase-contrast imaging can be divided into point-by-point scanning acquisition method with a single-point detector and full-field recording method with a surface array detector. The former has a low data acquisition rate and cannot image large samples quickly;the latter has a fast data acquisition rate,but also places higher demands on the detector′s pixel size and dynamic range.Continuous terahertz wave digital holographic imaging records the hologram by a faceted detector,and then obtains the complex amplitude information of the sample by a reconstruction algorithm. According to different optical path structures,continuous terahertz wave digital holography can be divided into in-line digital holography and off-axis digital holography. In-line digital holography can make full use of the spatial bandwidth product of the detector,but requires a sufficiently high energy ratio of direct and diffracted light after passing through the sample,as well as the problem of twin image interference. Off-axis digital holography introduces a certain angle between the object light and the reference light,which solves the twin image problem and makes the reconstruction process simple.Off-axis image-plane digital holography uses a microscope objective to directly collect the imaging information of the object. Compared with off-axis Fresnel digital holography,this imaging method has fast computation and high resolution,and has been widely applied at visible wavelengths. Besides,this imaging method has been combined with some other high-resolution imaging techniques,resulting in multi-angle illumination digital holography,structured light illumination digital holography etc. However,due to the lack of terahertz devices and the strong absorption of terahertz by polar substances,the terahertz full-field phase-contrast imaging usually requires a compact and simple optical path structure. To the best of my knowledge,no relevant work on terahertz image-plane digital holography has been reported yet. In recent years,various terahertz devices such as lasers,detectors and gratings have been developed rapidly. New terahertz imaging elements such as large numerical aperture terahertz lenses and terahertz solid immersion objectives have emerged,providing strong hardware support for the development of terahertz imaging. In this paper,a continuous terahertz wave image-plane digital holographic imaging method based on TPX lens is proposed. The holographic recording and reproduction process is studied,and the quadratic phase distortion introduced by TPX lens is removed by surface fitting distortion correction. The digital holographic imaging system of terahertz image plane is built. The imaging resolution of the system is quantitatively analyzed by using an amplitude Siemens star sample. Then two phase samples of organic materials and biological samples are imaged. The experiment verifies the effectiveness of the phase contrast imaging method. The introduction of image plane imaging in terahertz band is conducive to improve the resolution and quality of terahertz imaging. It has a wide application prospect in biomedical imaging,nondestructive testing and other fields.
作者
王云新
朱江磊
赵洁
王大勇
戎路
林述锋
WANG Yunxin;ZHU Jianglei;ZHAO Jie;WANG Dayong;RONG Lu;LIN Shufeng(College of Physics and Optoelectronics,Faculty of Science,Beijng University of Technology,Beijing 100124,China;Beijing Engineering Research Center of Precision Measurement Technology and Instruments,Beijing 100124,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2022年第4期108-115,共8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)。
关键词
太赫兹成像
数字全息
离轴数字全息
像面数字全息
畸变校正
Terahertz imaging
Digital holography
Off-axis digital holography
Image-plane digital holography
Aberration correction
