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

该项目的目的是开发一种静态傅里叶变换光谱仪，称为静态成像傅里叶变换光谱仪（SIFTS）。这种仪器利用一个简单的光学装置来分裂，然后重新组合光，形成一个复杂的调制干涉图案（称为干涉图）。通过对记录的干涉图进行傅立叶变换，获得源辐射的频谱。静态光学配置被布置成使得干涉图在空间上沿着焦平面分散，检测器可以定位在焦平面处。在该配置中，干涉图位于由检测器阵列内的像素元件的架构确定的离散位置处。与传统的迈克尔逊FTIR光谱仪不同，SIFTS设计紧凑（50 mm × 50 mm × 30 mm），重量轻（约0.4 kg）。由于光学配置是静态的，并且不需要使用扫描镜来获得干涉图，因此采集时间仅受检测器阵列的帧速率（~1 x 10 - 4 s-1）的限制，这使得SIFTS相对于传统FTIR光谱仪具有显著的时间采样优势。RAL已经建立了SIFTS的试验板版本，它成功地展示了该技术背后的原理。试验板仪器在紫外线和可见光谱区工作，使用市售的电荷耦合器件（CCD）检测器阵列。通过光纤将卤钨光源耦合到SIFTS仪器的输入端，可以记录光谱区域为400至1100 nm的各种目标的透射和反射光谱。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，它的目的是开发一个红外版本的SIFTS仪器，以最大限度地提高微量气体测量的灵敏度。该项目将调整这一经过验证的技术，用于近红外，使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设计，用于红外线，通过纳入光学元件和探测器阵列，在较长的波长敏感。

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.