三波段微光彩色夜视方法研究

为克服夜视设备产生单色图像的缺陷,得到更符合人眼视觉的彩色夜视图像。根据RGB理论模型以及滤光片的分谱作用原理,基于第二代像增强器设计出一种彩色夜视方案,通过测量滤光片的光谱透过率,得出滤光片对像增强器信噪比的影响;提出利用全波图像的四帧融合解决像增强器信噪比低的问题,并进行实验验证。实验结果显示室内和室外情况下四帧融合彩色图像熵和方差分别达到6.8、35.39及7.0、45.07,均优于三帧融合时对应值,说明提出的四帧融合方法能够克服信噪比降低的缺陷,得到清晰且信息量丰富的夜视图像。     

微光下SCMOS彩色成像处理系统设计

为了在微光条件下获取像白天一样兼具色彩和细节的图像,提出一种微光下的彩色成像处理方法:对彩色探测器图像进行降噪、增强和模糊处理,提取其中的色彩信息,对同时能接收可见光和近红外波段的高灵敏度黑白探测器图像进行降噪处理,获得微光场景的细节信息,在YCbCr色彩空间将色彩信息与微光场景的细节信息进行融合,生成微光场景下的彩色图像。根据这种方法,选择两款像元分辨率及像元尺寸相同的彩色和黑白SCMOS探测器,设计并搭建成像处理系统。实验结果表明,在0.01Lx的条件下,处理得到的彩色图像符合真实场景,适宜人眼观察。     

微光全景光学系统设计

根据微光像增强器成像特性,设计了微光全景光学系统,采用反射式前组与透射式后组结构。重点阐述反射式前组的设计方法,并据此设计优化得到了性能优良的成像系统。该系统有效焦距2.43 mm,工作波段0.4 m～0.9 m,有效工作F数1.5,水平视场360,垂直视场30～100。设计结果表明,系统全视场f 畸变小于6%,调制传递函数在24 lp/mm处大于0.3,系统指标满足成像要求。     

微光夜视鱼眼镜头的研究与设计

为了满足在夜晚低照度环境下对鱼眼镜头的需求,利用ZEMAX光学软件设计出了一款适用于2 inch微光夜视相机的微光夜视鱼眼镜头。该结构包含窗口透镜,共由7组10片透镜组成,其中除窗口外,其余全部为光学玻璃,而且选用的玻璃材料均为常用、性能良好、价格便宜的牌号。有效焦距为9.5 mm,相对孔径为1/1.8,视场角为170°,像高为21mm,光学系统总长为90 mm,最大口径为56 mm,后工作距离为10.4 mm。在分辨率46 lp/mm处,全视场范围内的MTF值均大于0.36,全视场f-θ畸变量的绝对值小于30%,场曲小于0.15 mm,镜头有较好的成像质量。     

微光夜视仪分辨能力的计算与分析

本文根据微光夜视仪分辨率经改进了的通用公式,通过对系统中诸参数内在联系的分析,找出一种根据目标在夜天光条件下(景物有不同的对比度和亮度),利用“人工眼”(由微光物镜和像增强器组成)的结构参数,求解系统中心分辨角(mrad)的新计算方法,作为视距估算的基础,同时对诸参数在其总体性能贡献方面作了初步的分析。列举国外某公司系列产品为例,计算结果表明,理论计算数据与实验结果基本上是吻合的,新的计算公式是切实可行的,具有一定的参考价值。     

一种双通道夜视图像彩色融合系统

提出了一种双通道夜视图像的彩色融合系统。利用Matrox Meteor-Ⅱ多通道图像采集卡获取双通道微光与红外视频图像．通过仿MIT,BIT．TNO．线性组合和混合结构等图像融合结构实现微光／微光和微光／红外图像的彩色融合处理。系统彩色图像融合处理是在VC++6．0环境下运用采集卡图像函数库实现的。建立的实验平台为彩色夜视融合算法的评价和进一步的研究奠定了基础。     

折/衍混合微光夜视头盔显示器光学系统设计

设计了穿透式双通道单目微光夜视头盔的光学系统。其中微光物镜视场角为± 14°,f数为 1.4 ,含有一个衍射面。设计结果可兼容输入面尺寸为18mm ,面型为平面的二代和三代微光像增强器 ;最大畸变小于 0 .5 % ,可用于夜间精确瞄准与测量。考虑黑暗环境使用的安全问题 ,显示系统采用穿透式双通道单目光学系统 ,实现内部图像和外部真实世界的同时观察。显示系统的特性参量为 :出瞳尺寸为 15mm (H)× 10mm (V)、视场为[± 14°(H) ]× [± 10° (V) ]、出瞳距离为 2 5mm。采用全息组合器大大提高能量利用率。设计结果系统角分辨力为0 .6mrad ,最大畸变为 3%。显示系统结构紧凑 ,可与输出面尺寸为18mm的图像源相连。     

微光像增强器常用荧光粉性能研究

荧光粉是微光像增强器荧光屏的关键材料,可将电子图像转换为可见光学图像,其性能对像增强器的分辨力、发光光谱、调制传递函数、余辉等性能有重要影响。针对国内外目前像增强器的发展情况,就国内外像增强器荧光屏常用的P20((Zn,Cd)S∶Ag)、P22(ZnS∶Cu,Al)、P31(ZnS∶Cu)、P43(Gd₂O₂S∶Tb)和P45(Y₂O₂S∶Tb)开展相应的性能对比研究,分别对这5种荧光粉的物相结构、光谱特性、发光效率及分辨力等性能进行了表征,分析了不同种类荧光粉的适用条件。结果表明:这5类常用荧光粉对于像增强器的不同性能提升各有贡献,其中分辨力较高的为P43荧光粉,发光效率较高的为P22荧光粉,而人眼观测舒适度最好的则为P45荧光粉。鉴于对微光像增强器高性能的要求,在选用微光像增强器用荧光粉时可选用综合性能较为优越的P22和P43荧光粉,也可根据像增强器的具体性能要求及实际使用需求选用合适的荧光粉种类。     

微光像增强器用核心材料的发展现状与展望

微光像增强器是微光夜视技术的核心器件,决定了整机的视距、清晰度、使用寿命等关键性能。详细分析了光纤面板、倒像器、纤维光锥、微通道板等微光像增强器核心材料的原理、特性及发展趋势,展望了微光夜视技术的发展方向。     

基于微光像增强器的偏振成像系统设计与实验

为验证用微光像增强器实现偏振成像的可行性,根据偏振成像原理,设计了基于分时型偏振成像技术的微光偏振检偏器。选用三代像增强器和高动态范围数字CCD,设计了相应大口径成像物镜和中继光学耦合透镜,获得了高透过率、高调制函数（MTF）的图像耦合性能。采用数字CCD、数字图像采集卡,编写了相应图像处理软件,实现了实验室和野外微光条件下的人造目标和自然景物的偏振探测成像。结果表明,原始图像中目标与背景对比度之比为1.35,基于微光像增强器的偏振成像系统的目标与背景对比度之比为2.35,微光偏振成像能够提高夜间环境下人造目标和自然背景的对比度。     

折反式微光夜视物镜的光学设计

介绍一种长焦距、大相对孔径微光夜视物镜的光学设计。设计参数为焦距100 mm,相对孔径1/1.4,视场10。为增大视距,减小物镜尺寸和质量,并且满足在宽光谱范围消色差的要求,选择均为球面的折反式物镜结构,在相同焦距和相对孔径的条件下折反式系统比折射系统尺寸更小,质量更轻。在设计过程中引入曼金反射镜,增加设计自由度。经优化设计达到较好的成像质量,空间频率在50 lp/mm时,轴上传递函数大于0.4,轴外传递函数大于0.2,与像增强器极限分辨率相匹配,全视场畸变小于2 %,物镜总长达到67 mm。     

微光夜视器件划代方法初探

随着微光夜视技术不断发展,微光夜视器件呈现出了品种多、性能差异大、应用领域广的特点,如何从众多的微光夜视器件中梳理出其发展主线,已成为微光夜视器件从业者的研究热点。回顾了零代、一代、二代、三代、超二代微光夜视器件的发展历程,总结归纳了行业公认的零代、一代、二代、超二代、三代微光夜视器件的划代方法,并提出了“四代”微光夜视器件的概念,同时对非典型的几种微光夜视器件在微光夜视器件技术领域中所处的位置进行了说明,绘制了“树状图”,以便读者能够直观、准确、全面地了解每种微光夜视器件的技术特点以及它们在微光夜视器件技术领域所处的位置,对从事微光夜视器件技术研究者具有一定参考作用。     

Fast color contrast enhancement method for color night vision

The increasing availability and deployment of imaging sensors operating in multiple spectral bands has led to a large research effort in color image fusion, resulting in a plethora of pixel-level image fusion algorithms. In this study a simple and fast fusion approach for color night vision is presented. The contrast of infrared and visible images is adjusted by local histogram equalization. Then the two enhanced images are fused into the three components of a Lab image in terms of a simple linear fusion strategy. To obtain false color images possessing a natural day-time color appearance, this paper adopts an approach which transfers color from the reference to the fused images in a simplified Lab space. To enhance the contrast between the target and the background, a stretch factor is introduced into the transferring equation in the b channel. Experimental results based on three different data sets show that the hot targets are popped out with intense colors while the background details present natural color appearance. Target detection experiments also show that the presented method has a better performance than the former methods, owing to the target recognition area, detection rate, color distance and running time.     

Kernel based color estimation for night vision imagery

Displaying night vision (NV) imagery with colors can largely improve observer's performance of scene recognition and situational awareness comparing to the conventional monochrome representation. However, estimating colors for single-band NV imagery has two challenges: deriving an appropriate color mapping model and extracting sufficient image features required by the model. To address these, a kernel based regression model and a set of multi-scale image features are used here. The proposed method can automatically render single-band NV imagery with natural colors, even when it has abnormal luminance distribution and lacks identifiable details.     

Objective evaluation of target detectability in night vision color fusion images

An evaluation for objectively assessing the target detectability in night vision color fusion images is proposed.On the assumption that target detectability could be modeled as the perceptual color variation between the target and its optimal sensitive background region,we propose an objective target detectability metric in CIELAB color space defined by four color information features:target luminance,region perceptual luminance variation in human vision system,region hue difference,and region chroma difference.Experimental results show that this proposed metric is perceptually meaningful because it corresponds well with subjective evaluation.     

Transfer color to night vision images

Natural color appearance is the key problem of color night vision field. In this paper, the color mood of daytime color image is transferred to the monochromic night vision image. This method gives the night image a natural color appearance. For each pixel in the night vision image, the best matching pixel in the color image is found based on texture similarity measure. Entropy, energy, contrast, homogeneity, and correlation features based on co-occurrence matrix are combined as texture similarity measure to find the corresponding pixels between the two images. We use a genetic algorithm (GA) to find the optimistic weighting factors assigned to the five different features. GA is also employed in searching the matching pixels to make the color transfer algorithm faster. When the best matching pixel in the color image is found, the chromaticity values are transferred to the corresponding pixel of the night vision image. The experiment results demonstrate the efficiency of this natural color transfer technique.     

Effective contrast enhancement method for color night vision

Image fusion refers to the techniques that integrate complementary information from multiple image sensors’ data in a way that makes the new images more suitable for human visual perception. The paper focuses on the low color contrast problem of linear fusion algorithms with color transfer method. Firstly, the contrast of infrared and visible images is enhanced using local histogram equalization and median filter. Then the two enhanced images are fused into the three components of a Lab image in terms of a simple linear fusion strategy. To enhance the color contrast between the target and the background, the scaling factor is introduced into the transferring equation in the b channel. Experimental results based on three different data sets show that the hot and cold targets are all popped out with intense colors while the background details present natural color appearance. Target detection experiments through target recognition area, detection rate, target-background discrimination also show that the presented method has a better performance than the former methods.     

Natural color low-level-light EBAPS imaging system based on three-color LCTF北大核心CSCD

The high-sensitivity electron bombarded active pixel sensor (EBAPS) not only has the characteristics of high gain and high sensitivity of vacuum imaging devices, but also has the digital characteristics of solid-state imaging devices, which greatly improves the level of night vision imaging. A natural color low-level-light EBAPS imaging system was built based on three-color liquid crystal tunable filter (LCTF). According to the characteristics of low-level-light images, the color enhancement processing such as grayscale stretching, white balance, and color correction was performed on the color images obtained by the system. The experimental results show that the system can realize the natural low-illumination color imaging that reflects the color characteristics of the scene itself, which can effectively improve the observation effect of the characteristics of the target scene at night, and can realize the color imaging under 5×10−4 lx illumination. © 2022 Editorial office of Journal of Applied Optics. All rights reserved.     

可变焦距机器视觉镜头光学系统设计

在机器视觉系统中,镜头的主要作用是将目标成像在图像传感器的光敏面上。针对生产过程中机器视觉系统在保持工作距离不变的情况下需获得不同的放大倍数,采用机械补偿形式,利用Zemax软件设计了一款可用于机器视觉的可见光多焦点变焦物镜系统。该系统工作距离可以在290 mm～340 mm范围内变化,实现了焦距从10 mm～100 mm的10倍多焦点变焦。设计结果表明:该变焦物镜最大畸变小于1%,最大兼容0.84 cm(1/3英寸)CCD图像传感器。用调制传递函数对系统的成像性能进行评估,该系统在空间频率100 lp/mm处调制传递函数大于0.3,满足成像要求。