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Dynamic Dichroic Mirrors and Single-Shot Spectroscopy

动态二向色镜和单次光谱

基本信息

批准号：
EP/S016538/1
负责人：
Christopher Rowlands
金额：
$ 25.84万
依托单位：
Imperial College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2019
资助国家：
英国
起止时间：
2019 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FS016538%2F1
关键词：
Dynamic Dichroic Mirrors Single Shot

项目摘要

Optical spectroscopy involves splitting light up into its component wavelengths, exactly like how a glass prism splits sunlight up into a rainbow (or 'spectrum') of colours. While this may, at first, just appear to be aesthetically pleasing, the rainbow of colours does include some very useful information about the light it came from. For example, if one were to look very carefully at the orange part of the spectrum of the sun (roughly around the colour corresponding to old orange street lights), one would find a pair of dark lines where the light appears to be missing. This corresponds to absorption due to sodium, which tells us that there is sodium in the upper atmosphere (or 'chromosphere') of the sun; we have, in effect, learned part of what the sun is made of, from 93 million miles away, using nothing more than a glass prism. This is the power of optical spectroscopy.Optical spectroscopy has many other uses; it can investigate the chemical composition of forensic samples, help locate a tumour, identify chemical weapons from a distance, monitor deforestation from orbit, authenticate artwork, and many more besides. Nevertheless, if we try to take pictures like we would do with a camera, there's a problem; a camera can only capture 2D information, and if we have a spectrum at each pixel, we either need to illuminate one line at a time (and use the other axis of the camera to measure the spectrum) or use a sequence of filters to get the data one wavelength at a time. In fact, if we know what spectrum we're looking for, the filter approach is much faster, but that requires carrying a stack of filters for each thing you might want to measure. That might be OK for a few things, but for portable or space-based applications, or if there are a lot of potential analytes, that can become infeasible. The alternative is to make a new filter each time, using a photorefractive polymer.This new system can create any filter that the user might want, writing it into a material similar to that used to make holograms. This is unlike normal tunable filters, which are typically only capable of tuning a single transmission band's width and center wavelength. This new approach can create any filter profile the user might want, including multiple independent bands and different band shapes. It works by recording an interference pattern in a holographic plate, using two laser beams. The angle between the laser beams is changed, and another interference pattern is recorded. After doing this many times, the filter profile is recorded in the hologram; this entire process takes less than a second. Once the filter isn't needed any more, it can be rewritten, and a new pattern created; any number of analytes can be searched for, including those which the system has never seen before; they need only be programmed in by the control computer.The holographic material is a new type known as a photorefractive polymer. Unlike normal holograms, this material is rewritable; it can be erased, and a new pattern written into it. While this has been used to create rewritable holographic displays before, this is the first example where the material will be used to create a holographic filter. Nevertheless, synthesizing it is not difficult; it requires just two components to be made from scratch, and these are both easy synthetic procedures with high yields.Overall, this project offers to create a kind of 'Instagram for spectroscopy'; rather than being limited to a small selection of physical camera filters, a user can digitally apply any one that might be needed, including programming a new one from scratch if necessary. This makes the spectroscopic imaging process faster, and more efficient, allowing the user to gather data over larger areas, and with more precision, than ever before.

光谱学涉及将光分解成其组成波长，就像玻璃棱镜将阳光分解成彩虹（或“光谱”）的颜色一样。虽然这可能，起初，只是看起来很美观，但彩虹的颜色确实包含了一些关于它来自的光的非常有用的信息。例如，如果仔细观察太阳光谱中的橙子部分（大致与旧的橙子路灯的颜色相对应），人们会发现一对暗线，那里似乎缺少光线。这对应于钠的吸收，这告诉我们太阳的高层大气（或“色球层”）中有钠;我们已经，实际上，从9300万英里之外，仅仅使用一个玻璃棱镜就了解了太阳的部分组成。这就是光谱学的力量。光谱学还有许多其他用途;它可以调查法医样本的化学成分，帮助定位肿瘤，从远处识别化学武器，从轨道上监测森林砍伐，鉴定艺术品，等等。然而，如果我们试图像用相机一样拍照，就会出现问题;相机只能捕获2D信息，如果我们在每个像素上都有光谱，我们要么一次照射一条线（并使用相机的另一个轴来测量光谱），要么使用一系列滤波器来一次获取一个波长的数据。事实上，如果我们知道我们正在寻找的光谱，滤波器方法要快得多，但这需要为您可能想要测量的每个东西携带一堆滤波器。这可能对一些事情是好的，但对于便携式或基于空间的应用，或者如果有很多潜在的分析物，这可能是不可行的。另一种方法是每次使用一种光折变聚合物制作一个新的滤光片，这个新系统可以创建用户可能想要的任何滤光片，将其写入类似于制作全息图的材料中。这与通常的可调谐滤波器不同，可调谐滤波器通常仅能够调谐单个传输带的宽度和中心波长。这种新方法可以创建用户可能想要的任何过滤器配置文件，包括多个独立的波段和不同的波段形状。它的工作原理是用两束激光在全息底片上记录干涉图样。改变激光束之间的角度，并记录另一个干涉图案。在这样做多次之后，滤光片的轮廓被记录在全息图中;整个过程不到一秒。一旦不再需要滤光片，它就可以被重写，并产生一个新的图案;可以搜索任何数量的分析物，包括那些系统以前从未见过的分析物;它们只需要由控制计算机编程。全息材料是一种新型的光折射聚合物。与普通的全息图不同，这种材料是可擦除的;它可以擦除，并写入新的图案。虽然这已经被用于创建可擦除全息显示器之前，这是第一个例子，该材料将被用于创建全息滤波器。然而，合成它并不困难，它只需要从零开始制造两种成分，这两种成分都是简单的合成过程，产量很高。总的来说，这个项目提供了一种“光谱学的Instagram”;而不是局限于一小部分物理相机滤镜，用户可以数字化地应用任何可能需要的滤镜，包括在必要时从头开始编程一个新的滤镜。这使得光谱成像过程更快，更有效，允许用户在更大的区域内收集数据，并且比以往任何时候都更精确。