单光纤内窥无透镜成像技术及器件研究

Endoscopic imaging technique shows very important applications in biomedicine. Traditional endoscopies based on both fiber bundles and Gradient-Index lens cascade are facing their technique limitations in the aspects of spatial resolution, diameter and length of fiber probe, etc. As a result, they cannot satisfy with higher requirements, such as minimal invasive and/or noninvasive diagnosis, operation and treatment. To overcome this obstacle, based on the mechanism of the mode-guiding analogous to the fiber-bundle guiding for optical propagation and that of the optical transmission matrix for image reconstruction, in this proposal we creatively propose a solution scheme of single-fiber lensless endoscopic imaging by use of a single-core multimode optical fiber. The main research contents include: To reveal the imaging principle of single-core multimode optical fiber and to establish the theoretical modal; To study the construction scheme, the scaling and self-calibration techniques of the optical transmission matrix of single fiber for endoscopic imaging; To investigate the efficient demodulation algorithm of the wave-front of the off-axis digital holography and its programmable realization technique; To establish the experimental and performance testing platform of single fiber imaging; To study some other related techniques of single fiber imaging such as manufacturing the key devices and/or components, developing the image treatment and reconstruction software, and integrating the single endoscopic imaging system. This project might yield important significances in science and have guiding values in endoscopic technology.

内窥成像技术在生物医学领域具有极其重要的应用价值。传统的光纤束型和梯度折射率透镜级联型内窥镜在空间分辨率、探头直径和长度等方面均接近技术极限，已不能满足现代医学对内窥镜在微创或无创检查、手术和治疗中的更高需求。为此，本项目基于模式导光可类比光纤束导光的光传输机理和基于光传输矩阵的图像重构思想，创新性地提出了基于单芯多模光纤的单光纤无透镜内窥成像的解决方案。主要研究内容包括：揭示单芯多模光纤成像机理及建立理论描述模型；研究单光纤内窥成像光传输矩阵的构建、定标及自校准技术；研究离轴数字全息光场波前高效解调算法和程控实现技术；建立单光纤成像的实验研究和性能综合测试平台；开展单光纤成像关键器件研制、图像处理和重建软件开发及单光纤内窥成像系统集成等相关技术研究。本项目的开展对医用或其它超细内窥成像技术发展具有重要的科学意义和引领价值。

内窥成像技术经过几十年的发展，在功能和性能指标方面都取得了很大的进步，在医学、工业和国防等领域得到了广泛应用。传统的光纤传像束型和棒透镜级联型内窥镜在空间分辨率、探头直径和长度等方面均接近技术极限，已不能满足现代医学对超细内窥镜在微创或无创检查、手术和治疗中的更高需求。本项目是针对目前内窥镜高像素数和细探头直径之间的矛盾，研究基于单根光纤成像技术，实现超细成像内窥镜。本项目深入研究了单光纤成像技术中光传输矩阵的测定、成像系统的定标和图像重建算法；研究了光场波前解调和相位模板构建，实现了光场点聚焦和光学点扫描，从而实现点扫描成像；利用深度学习算法，通过神经网络中自编码器和自校正网络，实现光纤成像，实验中对英文大写字母和数字手写体字符进行重建，重建准确率分别达到92.18%和91.26%。建立了一套完整的光纤成像系统，可实现不同条件下的光纤成像实验。采用单根多模光纤（芯径105 μm）可实现100×100像素图像的成像，光纤长度可达到5 m。项目执行期间发表论文28篇，申请专利6项，培养研究生13名。