Gasser Christoph, González-Cabrera María, Ayora-Cañada María José, Domínguez-Vidal Ana, Lendl Bernhard
Institute of Chemical Technologies and Analytics TU Wien Vienna Austria.
Department of Physical and Analytical Chemistry Universidad de Jaén Jaén Spain.
J Raman Spectrosc. 2019 Jul;50(7):1034-1043. doi: 10.1002/jrs.5607. Epub 2019 Apr 30.
Stand-off Raman spectroscopy offers a highly selective technique to probe unknown substances from a safe distance. Often, it is necessary to scan large areas of interest. This can be done by pointwise imaging (PI), that is, spectra are sequentially acquired from an array of points over the region of interest (point-by-point mapping). Alternatively, in this paper a direct hyperspectral Raman imager is presented, where a defocused laser beam illuminates a wide area of the sample and the Raman scattered light is collected from the whole field of view (FOV) at once as a spectral snapshot filtered by a liquid crystal tunable filter to select a specific Raman shift. Both techniques are compared in terms of achievable FOV, spectral resolution, signal-to-noise performance, and time consumption during a measurement at stand-off distance of 15 m. The HSRI showed superior spectral resolution and signal-to-noise ratio, while more than doubling the FOV of the PI at laser power densities reduced by a factor of 277 at the target. Further, the output hyperspectral image data cube can be processed with state of the art chemometric algorithms like vertex component analysis in order to get a simple deterministic false color image showing the chemical composition of the target. This is shown for an artificial polymer sample, measured at a distance of 15 m.
远程拉曼光谱提供了一种从安全距离探测未知物质的高选择性技术。通常,有必要扫描大面积的感兴趣区域。这可以通过逐点成像(PI)来完成,即从感兴趣区域的一系列点依次获取光谱(逐点映射)。或者,本文介绍了一种直接高光谱拉曼成像仪,其中散焦的激光束照亮样品的大面积区域,拉曼散射光作为由液晶可调谐滤波器滤波以选择特定拉曼位移的光谱快照,一次从整个视场(FOV)收集。在15米的远程距离测量中,对这两种技术在可实现的视场、光谱分辨率、信噪比性能和时间消耗方面进行了比较。高光谱拉曼成像仪显示出卓越的光谱分辨率和信噪比,同时在目标处激光功率密度降低277倍的情况下,视场比逐点成像增加了一倍多。此外,输出的高光谱图像数据立方体可以用诸如顶点成分分析等先进的化学计量算法进行处理,以获得显示目标化学成分的简单确定性伪彩色图像。这在距离为15米处测量的人工聚合物样品上得到了展示。