Ultraviolet and visible spectral imaging of hydrogen flames using an organic photoconductive film CMOS imager
Ultraviolet and visible spectral imaging of hydrogen flames using an organic photoconductive film CMOS imager
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使用有机光电导薄膜 CMOS 成像仪对氢火焰进行紫外和可见光谱成像
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
T. Tanaka
中科院分区：
文献类型：
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作者：
T. Okino;S. Yamahira;S. Yamada;Y. Hirose;A. Odagawa;Y. Kato;T. Tanaka
我们研制了一套真实的实时紫外成像系统，该系统可以在室外环境中将不可见的氢气火焰与可见光（维斯）背景场景一起显示出来。作为UV/维斯图像传感器，采用有机光电导膜（OPF）成像器。OPF在UV波长区域中具有比传统消费者CMOS图像传感器（CIS）或电荷耦合器件（CCD）更高的固有灵敏度。氢火焰的成像是通过从叠加在背景上的紫外氢火焰图像中减去高水平背景维斯图像来实现的。该系统能够成像比维斯背景弱4个数量级的氢火焰信号。它不仅适用于未来的氢气供应站，也适用于其他需要日盲成像的UV/维斯监测系统。引言使用氢的燃料电池被认为是下一代电源的主要候选人，不会对环境造成任何负荷。沿着这一路线图，几个国家已经开始建设氢气供应站[1]。这些系统中安全问题的主要关注点在于，当与空气混合时，氢在10%至60%的相对含量范围内[2]，由于点火能量降低，氢变得极其易燃。此外，由于氢火焰的发射带头位于紫外（UV）区域（~310 nm），因此人眼不可见。一个最坏的和实际报告的情况是，人类通过无形的氢火焰所造成的意外泄漏氢从高压罐附近点燃泄漏点[1]。因此，在这些站中，重要的是立即和准确地检测普通背景场景内的氢火焰。为此，需要使UV和可见（维斯）光场景可视化的成像系统。此外，相对于背景维斯光（在白天阳光的情况下，约为105勒克斯），氢火焰的光强度极小（通常为1~10 nW/cm 2）。为了使氢火焰可视化，成像系统应该不仅能够检测氢UV（~310 nm）信号，而且能够将它们从高背景维斯信号中分离出来。在这方面，普通Si CMOS图像传感器（CIS）在UV区域中的灵敏度不够高，除了特别制造的CIS，其中UV光的量子效率被增强[3]。尽管已经报道了在UV范围内具有高灵敏度的基于UV感测材料（即AlGaN）的传感器，但是它们不能对维斯光成像[4]。在这项工作中，我们开发了一个紫外和可见光（UV+维斯）成像系统的有机光导薄膜（OPF）成像器的基础上。OPF在所需的整个波长区域（即从UV到维斯区域）内具有固有的高灵敏度。氢火焰的成像是通过从叠加在背景上的紫外氢火焰图像中减去高水平背景维斯图像来实现的。该图像处理在每一帧中执行，导致真实的时间监控。结果表明，该系统能够从高4个数量级的维斯背景信号中成像出微弱的氢火焰信号。OPF成像仪的优点OPF成像仪作为氢成像仪的主要优点有两个方面。首先，如图1所示，与普通CIS或报道的UV传感材料相比，OPF成像器在维斯和UV区域都具有高量子效率。图1：OPF CMOS成像器（红色）、Si CIS（黑色）和AlGaN光电二极管（蓝色）的量子效率光谱[4]。
We have developed a real time ultra-violet (UV) imaging system that can visualize invisible hydrogen flame together with a visible (VIS) background scene in outdoor environment. As a UV/VIS image sensor, an organic photoconductive film (OPF) imager is employed. The OPF has intrinsically higher sensitivity in the UV wavelength region than those of conventional consumer CMOS image sensors (CIS) or Charge Coupled Devices (CCD). Imaging of hydrogen flame is realized by subtracting a high level background VIS image from a UV hydrogen flame image overlapped on the background. The system is capable of imaging a weaker hydrogen flame signals by 4 orders of magnitude than that of VIS background. It is applicable not only to future hydrogen supply stations but also to other UV/VIS monitor systems requiring solar blind imaging. INTRODUCTION Fuel cells using hydrogen are considered to be a primary candidate for next generation power sources causing no load of environment. Along this roadmap, construction of the hydrogen supply stations has been started in several countries [1]. A major concern in safety issues in these systems lies in the fact that hydrogen becomes extremely flammable due to lowering of the ignition energy when mixed with air in a relative contents range of 10% to 60% [2]. Furthermore, because the emission band head of the hydrogen flame lies in a ultra-violet (UV) region (~310 nm), it is invisible to human eyes. A worst and actually reported scenario is that human beings pass through the invisible hydrogen flame caused by accidentally leaking hydrogen from a high pressure tank ignited near the leaking point [1]. Therefore, in these stations, it is important to immediately and accurately detect hydrogen flames within an ordinary background scene. To this end, an imaging system that visualizes both UV and visible (VIS) light scenes are required. In addition, the light intensity of hydrogen flame is extremely small (typically 1~10 nW/cm2) against background VIS light (in the case of daytime sunlight, it is about 105 lux). In order to visualize hydrogen flame, the imaging system should be able not only to detect hydrogen UV (~310 nm) signals, but also to separate them from high background VIS signals. In this regard, the sensitivity of ordinary Si CMOS image sensor (CIS) in UV region is not sufficiently high except for a specially made CIS in which the quantum efficiency of UV light is enhanced [3]. Although UV sensing material, i.e. AlGaN, based sensors with high sensitivity in a UV range have been reported, they are incapable of imaging VIS light [4]. In this work, we have developed an ultra-violet and visible (UV+VIS) imaging system based on an organic photoconductive film (OPF) imager. The OPF has intrinsically high sensitivity in the entire wavelength region desired, i.e. from UV to VIS regions. Imaging of hydrogen flame is realized by subtracting a high level background VIS image from a UV hydrogen flame image overlapped on the background. This image process is carried out in each frame resulting in a real time monitoring. It is shown that the system is capable of imaging a weak hydrogen flame signals from a 4 orders of magnitude higher VIS background signals. ADVANTAGE OF OPF IMAGER Major advantages of the OPF imager as the hydrogen imager are two folds. Firstly, as shown in Fig. 1, the OPF imager has high quantum efficiency both in the VIS and the UV regions as compared with those of ordinary CIS or reported UV sensing materials. Fig.1: Quantum efficiency spectra of our OPF CMOS imager (red), a Si CIS (black) and an AlGaN photodiode (blue) [4].
影响因子：
1.8
作者：
R. Ono;M. Nifuku;S. Fujiwara;Sadashige Horiguchi;T. Oda
通讯作者：
R. Ono;M. Nifuku;S. Fujiwara;Sadashige Horiguchi;T. Oda