含光纤传像束耦合离散采样成像系统调制传递函数评价方法与测试技术研究

Joining fiber-optic image bundles can improve the synthetically performance of the electro-optical imaging system significantly. However, for the reason that multiple discrete sampling optical-electro components with determined coupled relationship in the system，there are suitable problem to derivation and evaluation the Modulation transfer function (MTF) by classical algorithm such as Forier transform or cascade multiplication. For this reason, the characteristics and evaluation standard haven’t unified, which has become a key technology and theory restricting the development of new concept optical-electro imaging technology.Therefore, the topic will deduce the intensity distributed function of output signal transferred by multiple coupled discrete sampling optical-electro components from intensity cosine distribution as object function. The derivation based on the statistic average route to define the coupled Modulation transfer function. The study hope to establish analytical expression of MTF for coupled discrete system, which help to explore imaging principle of the system, and reveal the relationship of the coupling accuracy, frequency domain , components manufacturing error with the coupled MTF of coupled discrete imaging system. The topic expects to resolve the key technology such as the generation method of high precision cosine optical signal, and modulation contrast calibrated at real time. The whole research will provide the theoretical basis and experimental guidance for design, manufacturing, alignment and testing in subsequent application of new conception optical-electro imaging system.

光电成像系统中加入光纤传像束可大幅改善仪器综合性能，由于存在具有多级耦合关系的离散采样光电元件，基于空间不变假设的傅里叶变换、级联相乘等经典算法推导与评价其调制传递函数存在适用性问题，造成耦合离散成像系统调制传递函数的评价与测试标准尚不统一，多级耦合离散系统传递函数计算与测试方法已经成为发展新概念光电成像技术急待解决的关键理论与技术问题。课题通过推导光强余弦分布光学信号经多级耦合离散采样光电元件传递后输出信号的光强分布函数，采用统计平均思想基于传递函数调制度定义建立系统调制传递函数解析表达式，揭示耦合离散成像系统调制传递函数与像元匹配精度、频域特性、元件制造误差等参数间的作用规律，探索耦合离散系统成像机理。希望获得高精度余弦光学信号发生、调制度实时测定等耦合离散系统传递函数测试的关键技术，为包含光纤传像束的新概念光电成像系统设计、制造、装调、成像质量评价提供理论与试验基础。

光纤传像束与光电探测器集成，使成像系统具备耦合离散采样特性，导致传统像质评价和分析方法存在理论困难，课题针对上述问题开展研究并进行初步实验验证。针对两种光纤束排丝方式，分别推导阵列中任意像元输出光强度表达式，基于光强调制度定义和统计平均思想，建立了耦合离散采样系统耦合调制传递函数模型。基于此对耦合调制传递函数随阵列像元数增加振荡收敛、随耦合偏差周期振荡等特性进行系统分析。提出并建立了平均耦合调制传递函数数理模型，针对续排光纤束研究了包层、芯层半径与函数间作用关系。此外，课题搭建了实验装置，验证并观测到耦合调制传递函数随像元耦合偏差周期振荡的现象，并验证了利用共光路干涉生成光强余弦分布目标进行耦合离散系统传函测试的可行性。.目前研究进展表明，若存在像元耦合偏差，以及输入信号空间频率与Nyquist频率间的微小偏差时，耦合调制传递函数随像元数增加振荡收敛为固定值，收敛速度与频率偏差大小逆相关。收敛特性在弧失和子午方向同时显现，但最终收敛值与对应方向的像元耦合偏差大小有关。仿真和实验均表明耦合调制传递函数随像元耦合偏差周期振荡，其空间频率等于包层直径，周期振荡幅值与空间频率偏差大小正相关。平均耦合调制传递函数可避免初位置、像元耦合误差引发的函数不确定性，可用于解释耦合离散成像系统像质与其本征参数间的作用关系。仿真分析发现，芯层半径对像质影响较小，而包层半径越小，成像系统在整个Nyquist频域内的调制传递函数值越高。此外，课题还对实验中涉及的光纤窗口、光学目标、耦合成像系统、CCD感光面间对准方法，面阵CCD调制传递函数测试方法、低亮度目标探测和坐标提取等关键技术进行了深入研究和实验验证。.项目相关研究成果和关键技术有望应用于空间高分辨超光谱成像、非推扫超光谱摄影、高性能柔性光学探针与内窥镜等新概念成像技术领域。