Analysis and modeling of radiometric error caused by imaging blur in optical remote sensing systems

Imaging blur changes the digital output values of imaging systems. It leads to radiometric errors when the system is used for measurement. In this paper, we focus on the radiometric error due to imaging blur in remote sensing imaging systems. First, in accordance with the radiometric response calibration of imaging systems, we provide a theoretical analysis on the evaluation standard of radiometric errors caused by imaging blur. Then, we build a radiometric error model for imaging blur based on the natural stochastic fractal characteristics of remote sensing images. Finally, we verify the model by simulations and physical defocus experiments. The simulation results show that the modeling estimation result approaches to the simulation computation. The maximum difference of relative MSE (Mean Squared Error) between simulation computation and modeling estimation can achieve 1.6%. The physical experimental results show that the maximum difference of relative MSE between experimental results and modeling estimation is only 1.29% under experimental conditions. Simulations and experiments demonstrate that the proposed model is correct, which can be used to estimate the radiometric error caused by imaging blur in remote sensing images. This research is of great importance for radiometric measurement system evaluation and application.     

采用低温面源黑体实现红外系统宽动态范围定标

针对大口径地基红外辐射测量系统在辐射定标时存在定标时间长、成本高和设备机动性差等缺点,提出一种仅采用低温面源黑体实现红外系统宽动态范围定标的方法.首先对红外系统中的衰减片进行标校,测量其实际透过率并计算其辐射量;然后采用低温面源黑体在两个积分时间下分别进行辐射定标,根据定标结果解算系统响应率、杂散辐射和探测器自身偏置;结合标校获得的衰减片特性对低温定标结果进行外推,即可获得宽动态范围定标结果.为验证该定标方法有效性,分别采用该方法和通用的高温黑体加大口径平行光管定标法,对Φ600mm红外系统进行宽动态范围辐射定标实验.实验结果表明:本文方法的宽动态范围定标误差小于10.25%,能够满足该系统的辐射定标精度要求.该方法只需要一个低温黑体即可实现红外系统的外场宽动态范围辐射定标,操作简单、实时性强,具有一定的应用价值.     

三波段成像光学系统的辐射定标

系统的成像波段分别为近紫外（300 nm~380 nm）波段,可见光（380 nm~760 nm）波段和近红外（760 nm~1 100 nm）波段。通过搭建与该光学系统相对应的辐射定标装置,建立辐射定标数学模型,对已研制的三波段成像光学系统进行绝对辐射定标的研究。针对系统成像波段光谱范围较宽的特点,以分波段辐射定标方法对于测量得到的定标数据,采用最小二乘线性拟合法进行处理,对算法进行修正,再对定标数据进行处理。通过实验验证了2种方法的定标精度,结果表明:修正后的算法可得到精度更高的定标曲线,测量相对误差不超过5%,定标结果满足实际工程需求。     

机载合成孔径雷达海面风场探测辐射定标精度要求研究

复杂的机载合成孔径雷达系统使得探测精度要求研究难以系统有效. 依据辐射定标精度在机载合成孔径雷达海面风场探测信息流程中的作用, 提出通过辐射定标精度要求整体考察系统探测精度要求的研究方法, 仿真研究了CMOD4地球物理模型函数的参数关系,系统地确定出不同入射角和风向条件下机载合成孔径雷达海面风场探测的辐射定标精度要求.研究结果表明, 辐射定标精度要求随着入射角的增加而降低,且随着风向变化呈周期性变化, 这一规律与CMOD4地球物理模型函数中由风速变化引起的后向散射截面变化值的变化规律一致. 依据这一规律,研究发现通过采用有源定标器定标、设计载机做侧风飞行以及选择大入射角的探测图像作为反演图像区这三种手段,能够提高风速反演精度.     

卫星多光谱扫描仪模拟空间环境辐射定标技术

模拟空间环境辐射定标技术主要用于卫星发射前对其所携带的多光谱扫描仪的响应特性进行辐射定标,为用户提供定标曲线。介绍了利用多个光源、多套定标光学系统的多光谱扫描仪辐射定标技术。多谱段光源系统由太阳辐照积分球和黑体组成,积分球用于可见光、近红外谱段的辐射定标,黑体用于远红外谱段的辐射定标。多谱段定标光学系统通过在真空低温环境下的精密传动机构切换反射镜位置,以离轴抛物面反射镜为中心形成两套光学系统,分别将积分球、黑体的辐射反射到扫描仪的入口,从而一次试验即可完成卫星多光谱扫描仪全谱段的辐射定标。     

Experimental Research on Optimal Millimeter Wave Radiometric Images

Widely used in remote sensing and guidance, radiometer is a typical passive detection system. However, it is an important problem to improve the millimeter wave radiometric imaging resolution. On basis of discussing imaging theory of radiometer, this paper presents the way to get optimal radiometric images by experimental research. The experimental result shows the satisfying images can be obtained by the matching of the parameters.     

Painlevé analysis and exact solutions of the resonant Davey-Stewartson system

It is shown that the resonant Davey-Stewartson (RDS) system can pass the Painlev test. By truncating the Laurent series to a constant level term, a dependent variable transformation is naturally derived, which leads to the bilinear forms of the RDS system. From the bilinear equations, through making suitable assumptions, some new soliton solutions are obtained. Some representative profiles of the solitary waves are graphically displayed including the two-line soliton solution, “Y” soliton solution, “V” soliton solution, solitoff, etc. The solutions might be useful to describe the nonlinear phenomena in Madelung fluids, capillarity fluids, and so on.     

Research on radiometric calibration for super wide-angle staring infrared imaging system

To perform radiometric calibration on super wide-angle staring infrared imaging system, the calibration experiment is carried out by using a standard blackbody source with a plate shape in laboratory, and the error analysis and data inversion are made based on the calibration results. Firstly, through analyzing the influencing factors including optical system, detector and signal processing circuit, the optical response model is established. Then, the radiometric calibration experiment is developed in the darkroom environment, and the error analysis is done from six aspects, which are the temperature and radiation instability of the black body, goniometer accuracy, angular resolution, the instability of detector output, data fitting error. Finally, according to the calibration results and the imaging characteristics of short-range airplane in the system, the infrared radiation intensity of aircraft target is calculated. The radiometric calibration and data inversion will benefit obtaining the target radiation characteristic during the system application, and can provide data reference for target detection, recognition, classification, so on.     

8MM Radiometric Simulation Detection Based on Optical Image

Widely applied in the fields of guidance and remote sensing, millimeter wave radiometer is a typical passive detection system. Radiometric simulation detection based on optical image is presented as a new approach of target detection. In this paper, we mainly discuss the design proposal of software structure and the output results of simulation system. We have developed 8mm radiometric target detection simulation system, which exactly simulated radiometric target detection by the working procedure, simulation environment and technical parameters. All adoptive data is measured and collected by our lab for many years. So the result is acceptable. It is greatly helpful to detect specific target and improve radiometric hardware design.     

成像光谱仪绝对辐射定标技术研究

为了实现成像光谱仪绝对辐射定标,以高稳定均匀光源为基础,结合单色仪、大口径平行光管和标准辐射计,建立了一套绝对辐射定标系统。在绝对辐射定标系统上采用替代法标准辐射计标定出被测成像光谱仪入瞳面上的光谱辐射照度,通过获得被测成像光谱仪各像元的输出信号,计算得到各像元的光谱辐射照度响应度,从而实现成像光谱仪可见到远红外波段范围内的绝对辐射定标。实验验证成像光谱仪绝对辐射定标的不确定度优于5%。