Development of a Miniature Static Imaging Fourier Transform Spectrometer (SIFTS)

该项目的目标是开发一种小型化的傅里叶变换光谱仪，称为静态成像傅里叶变换光谱仪(SIFTS)。该仪器利用一种简单的光学装置将光分开，然后重新组合，形成复杂的调制干涉图案(称为干涉图)。通过对记录的干涉图应用傅里叶变换来获得源辐射的频谱。静态光学配置被布置为使得干涉图沿着可以定位检测器的焦平面在空间上分散。在该配置中，干涉图位于由探测器阵列内的像素元件的体系结构确定的离散位置。与传统的迈克尔逊FTIR光谱仪不同，SIFTS的设计紧凑(50 Mm X 50 Mm X 30 Mm)，重量轻(约0.4千克)。由于光学结构是静态的，不需要使用扫描镜来获得干涉图，采集时间仅受探测器阵列的帧速率(~1×10~(-4)S~(-1))的限制，这使得SIFT比传统的傅里叶变换红外光谱仪具有显著的时间采样优势。雷尔已经建造了筛板版本，成功地展示了这项技术背后的原理。面包板仪器使用市面上可买到的电荷耦合器件(CCD)探测器阵列，在紫外线和可见光谱区域工作。通过光纤将卤化钨光源耦合到SIFTS仪器的输入端，可以记录光谱区域400到1100 nm内各种目标的透射谱和反射谱。然而，与气体分子相关的基本旋转振动吸收带位于光谱的近红外和中红外部分。因此，它打算开发一种红外版本的SIFT仪器，以最大限度地提高痕量气体测量的灵敏度。该项目将使这项经过验证的技术用于近红外，使该仪器在关键气体活跃的区域具有光谱敏感性。这将涉及优化现有的红外设计，通过加入对较长波长敏感的光学元件和探测器阵列。

This aim of this project is to develop a miniaturised Fourier transform spectrometer, known as a Static Imaging Fourier Transform Spectrometer (SIFTS). This instrument utilises a simple optical arrangement to split and then recombine light to form a complex modulated interference pattern (known as an interferogram). The frequency spectrum of the source radiation is obtained by applying a Fourier transform to the recorded interferogram. The static optical configuration is arranged such that the interferogram is dispersed spatially along a focal plane, where a detector can be positioned. In this configuration the interferogram is at discrete locations determined by the architecture of the pixel elements within the detector array. Unlike conventional Michelson FTIR spectrometers, the SIFTS design is compact (50 mm by 50 mm by 30 mm) and lightweight (~0.4 kg). As the optical configuration is static and there is no need to use a scanning mirror to obtain an interferogram, the acquisition time is limited only by the frame rate of the detector array (~1 x 10-4 s-1), which gives the SIFTS a significant temporal sampling advantage over traditional FTIR spectrometers. A breadboard version of the SIFTS has been built at RAL, which has successfully demonstrated the principles behind the technology. The breadboard instrument operates in the ultra-violet and visible spectral region, using a commercially available charged coupled device (CCD) detector array. By coupling a tungsten halogen light source to the input of the SIFTS instrument via fibre optics, it has been possible to record transmission and reflectance spectra from various targets in the spectral region 400 to 1100 nm. The fundamental rotation-vibration absorption bands associated with gas molecules are, however, located in the near and mid infrared part of the spectrum. Therefore it is intended to develop an infrared version of the SIFTS instrument to maximise the sensitivity of trace gas measurements. This project will adapt this proven technique for use in the near infrared, so that the instrument is spectrally sensitive in the region where key gases are active. This will involve optimising the existing design for use in the infrared, by incorporating optical elements and a detector array that are sensitive at longer wavelengths.