本文研究了热电型非制冷焦平面红外探测器在4 状态斩波调制下的信号响应,从理论上得到了响应信号的变化,数值模拟分析表明,响应信号的变化可以反映出景物入射辐射在双波段的差异,由此可望通过单一非制冷钛酸锶钡(BaxSr1-xTiO3 ,BST) 焦平面探测器,实现获取景物双波段信息的热成像系统.

建立了后向散射光在二维光敏面上能量分布的理论模型,结合典型水下激光成像系统,提出用像面表观衬比度来评价系统极限探测距离的方法,并推导了计算公式;通过选取水下激光成像系统的典型参量进行模拟计算,进一步讨论了系统主要组成部分的相对位置对像面表观衬比度分布的影响;得到像面表观衬比度与目标距离的关系曲线以及系统极限探测距离随海水衰减系数的变化曲线,从而估算出不同水质条件下系统的极限探测距离。模拟仿真数据与实际实验结果基本一致。

The improved scene-based adaptive nonuniformity correction (NUC) algorithms using a neural network (NNT) approach for infrared image sequences are presented and analyzed. The retina-like neural networks using steepest descent model was the first proposed infrared focal plane arrays (IRFPA) nonuniformity compensation method, which can perform parameter estimation of the sensors over time on a frame by frame basis. To increase the strength and the robustness of the NNT algorithm and to avoid the presence of ghosting artifacts, some optimization techniques, including momentum term, regularization factor and adaptive learning rate, were executed in the parameter learning process. In this paper , the local median filtering result of Xij (n) is proposed as an alternative value of desired network output of neuron Xij (n) , denoted as Tij (n) , which is the local spatial average of Xij (n) in traditional NNT methods. Noticeably, the NUC algorithm is inter-frame adaptive in nature and does not rely on any statistical assumptions on the scene data in the image sequence. Applications of this algorithm to the simulated video sequences and real infrared data taken with PV320 show that the correction results of image sequence are better than that of using original NNT approach , especially for the short-time image sequences (several hundred frames) subjected to the dense impulse noises with a number of dead or saturated pixels.

根据人眼视觉实验,对光电成像系统的性能评价方法进行了理论研究,证明了光电成像系统与人眼之间存在最佳匹配状态,分析了视场角、成像系统性能以及系统角放大率对匹配的影响,定量描述电视型成像系统的最佳观察距离和直视型最佳目镜焦距的客观现象,所得结果与实际基本一致。

对阿基米德螺旋线调制斩波器的曝光效率进行了理论分析和数值模拟,得到斩波器曝光效率对后续信号处理的影响. 曝光效率直接影响后续探测器单元的曝光时间及入射辐射信号,与探测器信号读出时刻共同影响探测器有效积累电荷的均匀性;同时应在斩波器中增加调制同步定位点,可使热像仪适宜不同曝光效率的斩波器. 在热成像系统设计以及电子处理系统设计时,必须综合考虑斩波器曝光效率的影响.

对阿基米德斩波器及其工作状态进行了模拟,分析了探测器像元的曝光时间、曝光顺序、信号读出及其对后续信号均匀性处理的影响. 结果表明:探测器曝光的非均匀性与信号读出模式直接影响后续信号的均匀性处理,阿基米德螺旋线的参数、探测器几何尺寸、斩波器与探测器的相对位置等均影响探测器的曝光顺序和电荷均匀性. 在热成像系统总体设计以及电子处理系统设计时,必须综合考虑斩波器各参数的影响.

提出夜视彩色融合图像质量评价的三个基本指标是“目标探测性”、“细节”和“色彩”,并且通过视觉评价实验,研究了“感知质量”与这三个指标的相关性. 对十个场景的微光与红外图像采用四种融合算法产生的40幅假彩色图像进行评价实验,实验结果得出:融合图像都有好目标探测性,感知质量与目标探测性的相关性很小;感知质量与细节的相关系数是0. 89, 感知质量与色彩的相关系数是0. 75. 说明在满足目标探测性要求条件下,细节是视觉感知融合图像质量的最主要评价指标,而且色彩成为夜视彩色图像质量的一个重要指标.

图像的超分辨力复原和信噪比的提高是图像复原追求的目标. Poisson-ML 图像复原方法(PML)具有很强的超分辨力复原能力,但在复原过程中会产生振荡条纹且对带噪较大的图像不能取得理想的复原效果. 在Poisson和Markov 分布假设的基础上,提出基于Poisson-Markov 场的超分辨力图像复原算法及其正则化参数的自适应选择方法(MPML). 实验表明,MPML 算法不但具有很好的超分辨力复原能力,而且能有效减少和去除复原图像中的振荡条纹,对于带噪较大的图像也能取得理想的复原效果,因此其图像复原质量明显好于PML 算法. 正则化参数能被自动优化地选择且与图像复原的迭代运算同步进行.

Image expansion plays a very important role in image analysis. Common methods of image expansion, such as the zero-order hold method, may generate a visual mosaic to the expanded image, linear and cubic spline interpolation may blur the image data at peripheral regions. Since infrared images have the characteristics of low contrast and low signal-to-noise ratio (SNR), the expanded images derived from common methods are not satisfactory. As shown in the analysis of the course from images with low resolution to those with high resolution, the expansion of image is found to be an ill-posed inverse problem. An image interpolation algorithm based on MAP estimation under Bayesian framework is proposed in this paper, which can effectively preserve the discontinuities in the original image. Experimental results demonstrate that the expanded images by this method are visually and quantitatively (analyzed by using the criteria of mean squared error (MSE) and mean absolute error (MAE)) superior to the images expanded by common methods of linear interpolation. Even in expansion of infrared images, this method can also give good results. An analysis about choosing regularization parameter α in this algorithm is given.