连续太赫兹波数字全息生物样品成像方法研究

Terahertz (THz) radiation, due to its unique characters of low-energy, high-penetration, water-absorption, etc, has been widely used in biomedical imaging. A high-resolution, non-invasive, no-label, real-time, whole-field imaging method is proposed for biological samples based on continuous-wave (CW) THz digital holography. Firstly, based on the transmission and coherent characteristics of CW THz radiation, we would investigate the imaging mechanisum of the terahertz digital holography with the exact diffraction propagation theory, and quantitatively assess the inherent relationship of the spatial resolution, field of view, depth of focus and depth of field, which are key issues for evaluating the imaging system. Correspongingly, the optimization of the imaging system is carried out considering the measurement conditions of biological samples. Secondly, based on the sub-pixel shifting and the filtering process, high quality terahertz digital holograms would be obtained. Also,in order to increase the numerical aperture of the imagin g system, the two-dimensional grating would be applied to collect high-frequency components of the object wavefront. The phase retrieval algorithm based on extrapolation would be develeoped to recover the phase information on the recording plane and overcome the limitation of the detector. The high-resolution, high-fidelity quantitative distribution of the amplitude and phase information would be therefore obtained from the THz holograms. The experimental setup will be built with the CW THz source and the pyroelectric array camera, and applied for the practical biological imaging, including the dynamic quantitative observation. With the results, we would establish the relationships between THz complex amplitude distribution (both amplitude and phase contrast images) and physiological parameters of biological samples, which are very useful for the biomedical science. The project will and shall provide a high-resolution non-destructive quantitative THz imaging method for visualized biomedical research.

太赫兹波具有独特的低能性、高穿透性、惧水性等成像特性，在生物医学检测等领域具有重要的应用。本项目研究连续太赫兹波段的数字全息成像方法，旨在针对生物样品，发展一种无损无标记的、实时全视场、高分辨率成像技术。 首先，基于太赫兹波的传输理论和相干特性，研究连续太赫兹波数字全息成像机理，分析成像空间分辨率、视场、焦深与景深的内在制约关系，结合生物样品的实验条件，优化成像系统设计。其次，基于亚像素微位移及滤波处理，获取高质量的太赫兹全息图。随后，在样品照明光路中引入二维光栅收集衍射高频分量，发展相位恢复的外推算法，获得突破探测器参数限制的高分辨率、高保真度的定量幅值和相位分布信息。最后，构建实际生物样品的成像装置，开展动态定量观测研究，建立太赫兹波振幅和相衬图像信息与样品生理学参数的联系。本项目的开展将为现代生物医学的无损可视化研究提供一种太赫兹波段的高分辨率、动态连续的定量检测方法。

太赫兹波具有独特的传播和成像特性，在生物医学领域具有重要研究价值。本项目对连续太赫兹波数字全息成像方法及其生物医学应用开展研究，发表SCI论文17篇，授权发明专利4项。研究进展如下：.首先，提出了基于高斯拟合与频谱滤波的太赫兹图像增强技术，提出了基于相位恢复的外推迭代算法、亚像素微位移方法与合成孔径方法等三种连续太赫兹波同轴数字全息分辨率提高方法，实验分辨率达到100微米。提出了基于稀疏采样的太赫兹全息图记录方法，提出了一种基于随机掩膜的太赫兹离轴数字全息的散斑噪声抑制技术，和一种基于反射式连续太赫兹波数字全息的隐藏物体形貌检测方法。开展了连续太赫兹波叠层成像方法研究，提出了一种基于衍射回传的叠层探针位置校正方法。实验方面，测量并分析了光泵太赫兹源的功率稳定性、相干长度和谱宽等物理参数，搭建了多套连续太赫兹波同轴数字全息成像装置，国际上首次将太赫兹数字全息应用于生物成像，在人体原发性肝癌组织切片的太赫兹相衬像中观察到纤维化组织，已应用于成都中医药大学人体肝癌组织成像分析和一系列肝脏疾病早期诊断。.其次，开展了一系列连续太赫兹波三维计算层析成像方法研究。提出了一种基于面阵式探测器的连续太赫兹波数字全息层析成像方法，提高了投影数据采集效率和再现图像保真度。将光场调控技术引入计算层析成像系统，将太赫兹贝塞尔光束和层析成像技术相结合，获得了大景深成像样品的二维横截面重建图。开展连续太赫兹波计算层析成像方法在生物样品内部结构检测的应用，通过层析重建算法获得了鸡尺骨不同位置的二维横截面图，分析鸡尺骨的内部结构成分。.此外，提出了一系列数字全息再现算法，提出了一种同轴-离轴复合数字全息成像方法，利用离轴全息再现像作为同轴全息相位复原迭代初始值，可以有效消除共轭像，并提高成像分辨率。提出了一种同时适合离轴和同轴光路的双平面记录的数字全息成像方法，并用于强相位畸变时的成像。