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高分辨率成像光纤传像束制备工艺的进步使得传统高性能光电成像仪器具备柔性,并且使仪器的体积和重量大幅减小。面阵光纤传像束和面阵CCD间的像元耦合离散采样效应,导致了传统成像质量评价模型的局限性。从光强度呈余弦分布的光信号在面阵光纤传像束和面阵CCD中的传递过程出发,建立了耦合离散采样系统的耦合调制传递函数(Coupled-MTF)模型,研究了Coupled-MTF的收敛特性及其随像元耦合误差的变化规律等。研究表明,若输入信号的空间频率与奈奎斯特频率的偏差为1%,当阵列中包含的像元总数超过1000时,Coupled-MTF振荡收敛为固定值。输入信号的空间频率与奈奎斯特频率的偏差越小,Coupled-MTF振荡收敛的速度越慢。Coupled-MTF的振荡幅值在弧失和子午方向不同,且与各自方向的像元耦合误差有关。Coupled-MTF随面阵光纤传像束与面阵CCD间的像元耦合误差周期振荡,理论上振荡周期为包层直径。在奈奎斯特频率及其分频附近的频域,Coupled-MTF在给定空间频率处不为固定值。上述特性有别于传统空不变成像系统的调制传递函数。
Advances in high-resolution imaging fiber bundle imaging technology have made conventional high-performance electro-optical imaging devices flexible and significantly reduced in size and weight. The image element coupling discrete sampling effect between the array fiber optic imaging beam and the area array CCD leads to the limitation of the traditional imaging quality evaluation model. Based on the transmission of optical signals with cosine distribution in the plane-array fiber imaging beam and the array CCD, a coupled modulation transfer function (Coupled-MTF) model of the coupled discrete sampling system is established. The effects of the Coupled-MTF Convergence characteristics and its variation with the pixel coupling error. Research shows that if the input signal spatial frequency and Nyquist frequency deviation of 1%, when the array contains more than 1000 pixels, the Coupled-MTF oscillation converges to a fixed value. The smaller the deviation of the input signal’s spatial frequency from the Nyquist frequency, the slower the Coupled-MTF oscillation converges. Coupled-MTF oscillation amplitude in the arc loss and the meridional direction, and the direction of the pixel coupling error. Coupled-MTF oscillates periodically with the coupling error between the image carrier and the area CCD, and in theory, the oscillation period is the cladding diameter. In the frequency domain near the Nyquist frequency and its frequency division, the Coupled-MTF is not fixed at a given spatial frequency. The above characteristics are different from the modulation transfer function of the traditional space invariant imaging system.