中短波红外图像传感器读出电路研究进展

随着红外技术和探测器性能的进步,中波和短波红外技术在恶劣天气中具有更优秀的成像性能,在民用、军事和航空航天等领域中得到了越来越广泛的应用。读出电路作为连接探测器阵列与后级图像处理电路的关键模块,其性能对中短波红外相机系统性能具有重要影响,决定了最终的成像质量。文章综述了中短波红外图像传感器读出电路的发展现状,分析了读出电路中噪声、动态范围、帧频等问题,重点探讨了针对以上问题的解决方案。最后对读出电路未来设计的改进方向进行了讨论。     

Simultaneous Activation of Short‐Wave Infrared (SWIR) Light and Paramagnetism by a Functionalized Shell for High Penetration and Spatial Resolution Theranostics

Nanoparticle emitting short‐wave infrared (SWIR) light has received increased attention in the molecular imaging field due to its deeper tissue penetration, fast imaging, high sensitivity, and resolution. The simultaneously activated SWIR excited directly by an 808 nm laser and T₁‐weighted magnetic resonance imaging (MRI) signal are found in one single‐shell nanoparticle NaErF₄@NaGdF₄ (Er@Gd), which is used as a dual‐modality imaging contrast agent in vivo to accurately determine the position of tumors. The conjugated cypate is then aggregated on the surface of Er@Gd@SiO₂‐Cy/bovine serum albumin. With the guidance of dual modality imaging, photothermal therapy is effectively used to ablate tumors in a mouse model. The design of single‐shell nanomaterial activation of SWIR imaging and MRI signals is expected to provide a new strategy for high penetration and spatial resolution cancer theranostics.     

Inductively coupled plasma etching for large format HgCdTe focal plane array fabrication

Inductively coupled plasma (ICP) using hydrogen-based gas chemistry has been developed to meet requirements for deep HgCdTe mesa etching and shallow CdTe passivation etching in large format HgCdTe infrared focal plane array (FPA) fabrication. Large format 2048×2048, 20-μm unit-cell short wavelength infrared (SWIR) and 2560×512, 25-μm unit-cell midwavelength infrared (MWIR) double-layer heterojunction (DLHJ) p-on-n HgCdTe FPAs fabricated using ICP processing exhibit >99% pixel operability. The HgCdTe FPAs are grown by molecular beam epitaxy (MBE) on Si substrates with suitable buffer layers. Midwavelength infrared detectors fabricated from 4-in. MBE-grown HgCdTe/Si substrates using ICP for mesa delineation and CdTe passivation etching demonstrate measured spectral characteristics, RoA product, and quantum efficiency comparable to detectors fabricated using wet chemical processes. Mechanical samples prepared to examine physical characteristics of ICP reveal plasma with high energy and low ion angle distribution, which is necessary for fine definition, high-aspect ratio mesa etching with accurate replication of photolithographic mask dimensions.     

Non-destructive detection of blackspot in potatoes by Vis-NIR and SWIR hyperspectral imaging

Blackspot is a subsurface potato damage resulting from impacts during harvesting. This type of bruising represents substantial economic losses every year. As the tubers do not show external symptoms, bruise detection in potatoes is not straightforward. Therefore, a nondestructive and accurate method capable of identifying bruised tubers is needed. Hyperspectral imaging (HSI) has been shown to be able to detect other subsurface defects such as bruises in apples. This method is nondestructive, fast and can be fully automated. Therefore, its potential for non-destructive detection of blackspot in potatoes has been investigated in this study. Two HSI setups were used, one ranging from 400 to 1000 nm, named Visible-Near Infrared (Vis-NIR) and another covering the 1000–2500 nm range, called Short Wave Infrared (SWIR). 188 samples belonging to 3 different varieties were divided in two groups. Bruises were manually induced and samples were analyzed 1, 5, 9 and 24 h after bruising. PCA, SIMCA and PLS-DA were used to build classifiers. The PLS-DA model performed better than SIMCA, achieving an overall correct classification rate above 94% for both hyperspectral setups. Furthermore, more accurate results were obtained with the SWIR setup at the tuber level (98.56 vs. 95.46% CC), allowing the identification of early bruises within 5 h after bruising. Moreover, the pixel based PLS- DA model achieved better results in the SWIR setup in terms of correctly classified samples (93.71 vs. 90.82% CC) suggesting that it is possible to detect blackspot areas in each potato tuber with high accuracy.     

短波红外传感器的信噪比计算

在焦平面层,信噪比是设计中一项重要的指标．本文介绍了用等效电子数计算信噪比的方法,分析了其理论基础,并对其进行了讨论．     

短波红外超光谱成像仪前置物镜的设计

设计了一个短波红外透射式物镜用于超光谱成像仪.用色散公式计算了短波红外常用材料的阿贝数和部分色散数,并按照二级光谱的定义,计算了一些可用于双胶合的材料对.物镜采用Petzval结构,改进了可见光常用的PW设计方法,用于短波红外物镜设计的材料选择和初始结构计算.Petzval结构的物镜不能消除物镜的场曲,在焦面前加入一片平场透镜,用于扩展该物镜的有效视场.最后利用Zemax对系统的高级像差进行校正,获得像质良好的短波红外超光谱成像仪前置物镜.     

从短波红外与红光波段反演华北地区气溶胶

针对MODIS数据监测华北地区陆地气溶胶存在的植被稀少和仪器老化的问题,开展了基于短波红外波段和红光波段地表反射率比值反演气溶胶。讨论了华北地区MODIS传感器红波段和短波红外波段地表反射率的时间变化特征,发现二者之间的比值较为稳定,据此去除地表反射贡献,建立了陆地气溶胶反演算法。利用2016年9月—2017年8月过境华北地区的MODIS数据进行了算法测试和验证,该算法能够同时在植被稠密和稀疏的地区获得反演结果,较好地反映了气溶胶的空间分布。与AERONET北京Radi站和香河站气溶胶产品对比表明,该算法对于城市和乡村区域的应用效果较好,与地面观测结果的相关系数高于0.9,但算法出现了整体低估;分季节验证结果表明,季节之间的差异较小。     

A comparative study and performance characteristics of ion-implanted and heterojunction short-wave infrared HgCdTe focal-plane arrays

Short-wave infrared (SWIR) HgCdTe focal-plane arrays (FPAs) with a cutoff wavelength of 2.5 μm have been produced using both planar ion-implanted and heterojunction-mesa device structures. The two-dimesnional FPAs are comprised of a 320×256 format with 30-μm pixel pitch and are cooled by a multistage thermo-electric (TE) cooler. Measured R₀A values of the two types of device structures show similar results below about 130 K because of the performance-limiting effect of the surface passivation of the heterojunction. However, a substantial difference is seen above 130 K and up to 300 K between the two structures types, with the heterojunction-mesa p-on-n device having an order of magnitude higher R₀A value than the planar ion-implanted n-on-p configuration. The difference in the R₀A values is reflected in the FPA images of the two different device types, where at 200 K, both FPAs display a clear picture with the n-on-p implanted device having a somewhat lesser resolution. However, no image can be seen from the planar-implanted FPA at 300 K, whereas the heterojunction-mesa FPA still exhibits a notable image at this temperature. These differences are examined and are attributed largely to higher diffusion and generation-recombination (g-r) currents that are thought to be prevalent in the ion-implanted n-on-p device structure. Yet, baking studies carried out show the ion-implanted diodes to be slightly more robust, as experiments reveal that they tend to survive a 120°C heat treatment longer than the mesa devices, which tend to degrade after a certain period of time. The nature of n-type donors in ion-implanted diodes is discussed, and a new theory based on Te antisites is proposed to explain recent experimental findings.     

Real-time pixel based early apple bruise detection using short wave infrared hyperspectral imaging in combination with calibration and glare correction techniques

High speed data processing for online food quality inspection using hyperspectral imaging (HSI) is challenging as over hundred spectral images have to be analyzed simultaneously. In this study, a real-time pixel based early apple bruise detection system based on HSI in the shortwave infrared (SWIR) range has been developed. This systems consists of a novel, homogeneous SWIR illumination unit and a line scan camera. The system performance was tested on Jonagold apples bruised less than two hours before scanning. Partial least squares-discriminant analysis was used to discriminate bruised pixel spectra from sound pixel spectra. As the glossiness of many fruit and vegetables limits the accuracy in the detection of defects, several reflectance calibrations and pre-processing techniques were compared for glare correction and maximizing the signal to noise ratio. With the best combination of first derivative and mean centering, followed by image post-processing, this system was able to detect fresh bruises in thirty apples with 98% accuracy at the pixel level with a processing time per apple below 200 ms.     

星用短波红外成像仪的设计与实现

针对低轨卫星激光通信和大气层短波红外光谱分析的应用需求,设计并研制了一种星用短波红外成像仪。由于低轨卫星系统的抗总剂量辐射能力要求为20kRad(Si)以上,因此,该成像仪选用抗总剂量辐射能力达到20kRad(Si)的InGaAs焦平面探测器;采用宇航级元器件设计相应的时序驱动、温度控制、模数转换、图像传输、遥控遥测等硬件电路模块,组成成像仪硬件部分;应用PID温控算法实现成像仪精准控温,采用非均匀性校正算法和图像增强算法提升成像仪图像质量。经试验验证,研制的短波红外成像仪抗总剂量辐射能力达到25kRad(Si),动态范围大于等于61dB,非均匀性小于等于1.9%,满足低轨卫星短波红外光谱探测的要求。