Fast method for calculating infrared spectral transmittances in the wings of absorption lines

When performing line-by-line simulations of atmospheric high-resolution infrared spectra, a large portion of the computation time is spent in the calculation of the absorptions by the far wings of the absorption lines. For applications in which one is interested mainly in evaluating the effective absorption in a microwindow, a computationally less expensive method has been developed. The method is faster than the explicit line-by-line calculation by a factor proportional to the number of line wings that contribute to the absorption in the simulated microwindow. This paper presents the method and demonstrates its performances in the 700- infrared band. Typically one obtains a gain in computation time of order 25.     

红外系统作用距离实时计算系统

鉴于复杂大气条件下的红外系统作用距离难以精确、实时地计算,提出一种建立红外系统作用距离实时计算系统的方法。通过将MODTRAN软件与基于光谱等分法建立的红外系统作用距离模型有机地结合起来,实现对于MODTRAN软件自动写入配置及调用计算,简化了大气模型的配置方法,并能够自动读取MODTRAN生成的结果输出文件。对某探测目标在不同海拔高度（1 km~6 km）及不同降雨强度(0 mm/h~4 mm/h)下红外系统作用距离进行计算,结果表明:探测高度的变化对于红外系统作用距离有比较明显的影响,其中在1 km~3 km探测高度范围内,探测距离变化尤为明显。降雨对于红外系统作用距离影响巨大。降雨强度为1 mm/h时,红外系统作用距离衰减为无降雨时的50%。当降雨强度大于3 mm/h时,作用距离趋于稳定。     

扫描近场红外显微镜近场距离控制系统的改进

针尖 样品的距离控制系统是扫描近场红外显微镜的重要组成部分。切变力探测作为一种重要的近场距离控制手段而得到了广泛的应用。介绍了一种对切变力探测系统的改进方法 ,它可以有效地提高石英晶振音叉的品质因数 ,进而提高探测系统对切变力感应的灵敏度。给出了理论分析和实验验证结果     

Design of midwave infrared athermalization optical system with a large focal plane array

Based on the most advanced staring focal plane array which had a format of 640 × 480 and the pixel pitch of 15 μm, a set of all-sphere midwave infrared ahermalization optical system was designed. The working wavelength was in 3–5 μm, the full field of view was 8.58°, the relative aperture was 1/2, the efficient focal length (EFL) was 80 m. The opticalsystem consisted of four lenses with three kinds of material – Ge, ZnSe and Si. All surfaces were sphere, which was easier to process test, making the cost inexpensive, and it could avoid using diffractive surface and aspheric surface. The image quality of the system approaches the diffraction limit in the temperature range −60 °C-180 °C. The design results proved that, the high resolution midwave infrared optical system had compact structure, small volume, high resolution and excellent image quality, meeting the design requirements, so that it could be used for photoelectric detection and tracking system.     

紫外告警系统探测距离的估算

介绍了紫外告警原理及紫外告警系统的结构组成。基于典型目标(导弹)的紫外辐射特征和紫外辐射的大气传输特性,结合紫外告警系统探测器件的性能参数,根据像平面照度公式,提出了紫外告警系统探测距离的估算方法及模型,实例计算并验证了紫外告警系统在不同观察方位角对固体推进剂导弹的探测距离。分析研究表明,改变CCD最小照度值,像管的增益,光学系统的透过率和相对孔径等探测传感器的性能参数,可以提高紫外告警系统的探测距离。     

Aberration athermal design for infrared search and trace optical system

To satisfy environment requirement of infrared search and trace optical system, an infrared diffractive/refractive hybrid optical system in 3.7–4.8 μm with 11.42° of field of view for passive athermalization is presented. The system is consisted of three lenses, including two aspheric surfaces and a diffraction surface, which has only two materials Ge and Si. The optical system has compact structure, small volume and light weight. The image quality of the system approaches the diffraction limit in the temperature range −80 °C to 160 °C. It is compatible with staring focal plane array which has a format of 320 × 240 and the pixel pitch of 30 μm. The system need not move the compensated lens repeatedly to obtain the best images from −80 °C to 160 °C and enhances the performance of target tracking and recognition.     

一例典型红外光学系统的计算分析

计算分析美国探测金星水手Ⅱ号宇宙飞船上安置的红外辐射计光学系统,说明了光学系统的光学特征、像差校正原理及其结构和应用特点．     

结霜工况下重力供液与直接膨胀供液制冷系统运行特性

以R404A为工质,用热平衡法测试结霜工况下直接膨胀供液制冷系统以及重力供液制冷系统在不同蒸发器供液高度时的系统的运行特性,并进行比较。研究表明:在重力供液制冷系统中,蒸发温度和压力高于直接膨胀供液制冷系统,且受供液高度和环境温度影响;在不同供液高度时,重力供液制冷系统压缩机吸气压力高于直接膨胀供液制冷系统压缩机吸气压力,供液高度的增加,吸气压力升高,压缩机的排气压力的变化趋势与蒸发压力相似;重力供液制冷系统制冷量高于直接膨胀供液制冷系统制冷量,且随蒸发温度升高而增大,但制冷量的增加幅度却有着相反的变化趋势。供液高度为1200mm时,制冷量最大增幅达到35.59%;重力供液制冷系统COP大于直接膨胀供液制冷系统COP,重力供液制冷系统存在最佳供液高度。     

可见光液晶光谱成像系统研究

利用向列相液晶材料的电控双折射效应,研制了用于可见光波段光谱调谐的大口径液晶可调滤光片,透过光谱测试表明,该滤光片在可见光波段(420~700 nm)以20 nm光谱分辨率可实现连续调谐和任意波长选择。利用该滤光片搭建了一种小型光谱成像系统,并在实验室内对若干样品进行了测试,结果表明,该系统可同时实现高图像分辨率和高光谱分辨率光谱成像,具备高、超光谱分辨率光谱成像的应用潜力,在生物医学、环境保护和资源探测等领域具有较好的应用前景。     

压力作用下石英砂岩的热红外光谱变化与敏感响应波段

在实验室对石英砂岩进行单轴压缩加载,利用红外光谱辐射计(观测波段8～14μm)对加载过程中试样的红外光谱辐射变化特征进行观测,研究岩石红外辐射对应力响应的敏感波段。实验结果显示,当岩石被加载时,红外光谱随之发生变化,但不同波段变化特征不同,在8.0～11.5μm范围(尤其在8.6～9.1μm)石英砂岩的红外光谱辐射强度随载荷增加而增加,二者间近似呈两次曲线关系,且光谱辐射强度的"信噪比"较高;在其它波段光谱辐射强度与载荷的相关性差且"信噪比"较低。由此表明,8.0～11.5μm是石英砂岩红外辐射对应力响应的敏感波段,也是岩石应力与灾变红外遥感监测的优势波段,而最佳监测波段是8.6～9.1μm。     

Fusion method for infrared and visible images by using non-negative sparse representation

In this paper, an interesting fusion method, named as NNSP, is developed for infrared and visible image fusion, where non-negative sparse representation is used to extract the features of source images. The characteristics of non-negative sparse representation coefficients are described according to their activity levels and sparseness levels. Multiple methods are developed to detect the salient features of the source images, which include the target and contour features in the infrared images and the texture features in the visible images. The regional consistency rule is proposed to obtain the fusion guide vector for determining the fused image automatically, where the features of the source images are seamlessly integrated into the fused image. Compared with the classical and state-of-the-art methods, our experimental results have indicated that our NNSP method has better fusion performance in both noiseless and noisy situations.     

Analysis of a thermal imaging method for landmine detection, using infrared heating of the sand surface

The detection of a buried surrogate land mine is investigated by use of a pulsed thermographic method driven by a high powered infrared heater. In this experimental and analytical investigation, the surface of the sand is initially heated by infrared lamps and is then cooled by natural convection, and during this second phase a dry layer of sand develops on the surface. The temperature distribution of the dry sand surface is influenced by the presence of the buried mine.

The experimental investigation was performed in a laboratory where a surrogate mine was buried at depths between 1 cm and 4 cm in dry sand, and sand which had initial water contents of 2.5%, 5% and 10%. The results show that an observable ‘hot spot’ develops on the sand surface above the mine, during the cooling phase of most tests. The water content of the sand was found to have a strong influence on the development of the hot spot. The surface temperature variation for dry sand tends to be less than that found for sands that contain water and the only test where the hot spot was not detected was in dry sand where the mine was buried at 4 cm. A one-dimensional finite difference model was used to describe the heat and mass transfer mechanisms and interpret the experimental results.     

Radiative properties of cirrus clouds in the infrared (8–13 μm) spectral region

Atmospheric radiation in the infrared (IR) 8–13 μm spectral region contains a wealth of information that is very useful for the retrieval of ice cloud properties from aircraft or space-borne measurements. To provide the scattering and absorption properties of nonspherical ice crystals that are fundamental to the IR retrieval implementation, we use the finite-difference time-domain (FDTD) method to solve for the extinction efficiency, single-scattering albedo, and the asymmetry parameter of the phase function for ice crystals smaller than 40 μm. For particles larger than this size, the improved geometric optics method (IGOM) can be employed to calculate the asymmetry parameter with an acceptable accuracy, provided that we properly account for the inhomogeneity of the refracted wave due to strong absorption inside the ice particle. A combination of the results computed from the two methods provides the asymmetry parameter for the entire practical range of particle sizes between 1 and 10,000 μm over the wavelengths ranging from 8 to 13 μm. For the extinction and absorption efficiency calculations, several methods including the IGOM, Mie solution for equivalent spheres (MSFES), and the anomalous diffraction theory (ADT) can lead to a substantial discontinuity in comparison with the FDTD solutions for particle sizes on the order of 40 μm. To overcome this difficulty, we have developed a novel approach called the stretched scattering potential method (SSPM). For the IR 8–13 μm spectral region, we show that SSPM is a more accurate approximation than ADT, MSFES, and IGOM. The SSPM solution can be further refined numerically. Through a combination of the FDTD and SSPM, the extinction and absorption efficiencies are computed for hexagonal ice crystals with sizes ranging from 1 to 10,000 μm at 12 wavelengths between 8 and 13 μm.

Calculations of the cirrus bulk scattering and absorption properties are performed for 30 size distributions obtained from various field campaigns for midlatitude and tropical cirrus cloud systems. Ice crystals are assumed to be hexagonal columns randomly oriented in space. The bulk scattering properties are parameterized through the use of second-order polynomial functions for the extinction efficiency and the single-scattering albedo and a power-law expression for the asymmetry parameter. We note that the volume-normalized extinction coefficient can be separated into two parts: one is inversely proportional to effective size and is independent of wavelength, and the other is the wavelength-dependent effective extinction efficiency. Unlike conventional parameterization efforts, the present parameterization scheme is more accurate because only the latter part of the volume-normalized extinction coefficient is approximated in terms of an analytical expression. After averaging over size distribution, the single-scattering albedo is shown to decrease with an increase in effective size for wavelengths shorter than 10.0 μm whereas the opposite behavior is observed for longer wavelengths. The variation of the asymmetry parameter as a function of effective size is substantial when the effective size is smaller than 50 μm. For effective sizes larger than 100 μm, the asymmetry parameter approaches its asymptotic value. The results derived in this study can be useful to remote sensing studies of ice clouds involving IR window bands.     

红外光谱响应度测试系统研究

红外光谱响应度是红外探测领域的重要技术指标。介绍了红外光谱响应度的测试技术及其测试系统。该系统选用以无光谱选择的腔体热释电探测器为标准,用双单色仪进行分光同时,采用国际上最新的测试方法完成了红外波段光谱响应度的测量,获得了高的测量不确定度,分析了测试结果及其影响因素。     

红外图像的疲劳状态识别方法

目的：为了解决光照变化对疲劳检测系统造成的准确性不高的问题,提出了一种近红外环境下判断人眼状态的方法,即针对红外光补图像的人眼状态判断。方法：首先,利用Adaboost算法对人眼区域进行定位,在网格法标记人眼瞳孔部分的基础上,进行Retinex红外图像增强。接着,对二值化与边缘检测后的红外图像分别进行网格法闭合度计算,得到人眼闭合度。最后,根据闭合度计算结果设定双阈值并结合PERCLOS来判断眼睛状态。结果：在DM642硬件平台上进行疲劳检测试验,实验结果表明,人眼状态识别率达到了90%以上,且平均每秒能处理21帧图片。结论：证明了该方法不仅能有效解决光照变化带来的问题,而且满足疲劳状态检测系统的快速性、可靠性和有效性等要求。     

基于近红外光谱技术的人体血糖浓度无创检测系统的研制

开发了一种小型化人体血糖浓度无创检测系统,该系统可实现人体血糖浓度的快速、实时、无创检测,主要由嵌入式系统、夹具、光源系统和微型光栅光谱仪四部分组成。提出了一种光源稳压驱动电路方案,可满足多种光谱采集条件对光源的要求。同时提出了一种一体化夹具设计方案,不仅简化了系统的光学结构,而且提高了测量条件的可重复性。分别用小波去噪和核偏最小二乘法对采集的光谱数据进行预处理和数学建模,并对系统进行性能评价,血糖浓度预测值与标准值的相关系数为0.95,预测均方根误差为0.6mmol.L-1,系统的重复性较好。     

一种基于电光调制光频梳光谱干涉的绝对测距方法

提出了一种基于电光调制光学频率梳的光谱干涉测距方法.理论分析了电光调制光学频率梳的数学模型和光谱扩展原理,并分析得出了光谱干涉测距方法的非模糊范围和分辨力的影响因素.在实验中,使用三只级联的电光相位调制器调制单频连续波激光生成了40多阶高功率梳齿状边带,并通过单模光纤和高非线性光纤对电光调制器输出的激光进行光谱扩展,得到重复频率为10 GHz,光谱宽度达30 nm的光学频率梳.将该光频梳作为光谱干涉测距装置的光源,可以实现无"死区"的绝对距离测量.另外,使用等频率间隔重采样和二次方程脉冲峰值拟合算法对测量结果进行数据处理,可以修正系统误差,提升测距精度.实验结果表明,在1 m的测量范围内,使用该装置可以在任意位置达到±15μm以内的绝对测距精度.     

红外成像光谱测量中Dyson光学系统的研究进展

传统的红外成像光谱仪难以同时实现弱遥感信号下的高信噪比和仪器小型化的要求,基于Dyson同心光学结构的新型遥感红外成像光谱仪具有数值孔径大、信噪比高、结构简单、体积小、重量轻的优点,用于强背景信号下的微弱红外成像光谱信号测量时,可实现传统的红外成像光谱仪难以实现的高信噪比测量。本文概述了Dyson同心光学结构的产生、发展及最新研究动态,重点介绍了Dyson同心光谱仪的原理、研制过程中的难点以及在高性能遥感红外成像光谱测量中的应用,为高性能红外成像光谱仪的研究提供了参考。     

一种评价假目标红外示假效果的新方法

提出了一种新的评价假目标红外示假效果的方法。该方法首先采用Harris算子提取军事目标及其相应假目标的红外图像的特征点,然后采用Hausdorff距离计算所提取的特征点集之间的Hausdorff距离。该距离越大,说明假目标与真目标相差越大;该距离越小说明真、假目标越相似,也就是说假目标的红外示假效果越好。