Kelly Evan M, Egan Miles J, Colόn Arelis, Angel S Michael, Sharma Shiv K
Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, Hawaii, USA.
Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina, USA.
Appl Spectrosc. 2023 Dec;77(12):1411-1423. doi: 10.1177/00037028231204894. Epub 2023 Oct 6.
Spatial heterodyne Raman spectrometers (SHRSs) are modified forms of Michelson interferometers, except the mirrors in a Michelson interferometer are replaced with stationary diffraction gratings. This design removes the need for an entrance slit, as is the case in a dispersive spectrometer, and removes the need to scan the spectrum by using a moving mirror in a modern Michelson interferometer. In previous studies, various SHRS variants, such as free-standing two-grating SHRS, single-grating SHRS (1g-SHRS), monolithic SHRS (mSHRS), and single-grating mSHRS (1g-mSHRS), have been evaluated. However, the present study exclusively focuses on the 1g-mSHRS configuration. The 1g-mSHRS and 1g-SHRS increase the spectral range at fixed grating line density while trading off spectral resolution and resolving power. The mSHRS benefits from increased rigidity, lack of moving parts, and reduced footprint. In this study, we investigate how the choice of detector impacts the performance of the 1g-mSHRS system, with a specific focus on evaluating the performance of three types of cameras: charged-coupled device (CCD), intensified CCD (ICCD), and complementary metal-oxide-semiconductor (CMOS) cameras. These systems were evaluated using geological, organic, and inorganic samples using a 532 nm continuous wave laser for the CMOS and CCD cameras, and a 532 nm neodymium-doped yttrium aluminum garnet pulsed laser for the ICCD camera. The footprint of the 1g-mSHRS was 3.5 × 3.5 × 2.5 cm with a mass of 272 g or 80 g, depending on whether the monolith housing is included or not. We found that increasing the number of pixels utilized along the -axis of the camera increases fringe visibility (FV) and optimizes the resolution (by capturing the entirety of the grating and magnifying the fringes). The number of pixels utilized in the -axis, chip size, and dimensions, affect the signal-to-noise ratio of the systems. Additionally, we discuss the effect of pixel pitch on the recovery of Fizeau fringes, including the relationship between the Nyquist frequency, aliasing, and FV.
空间外差拉曼光谱仪（SHRS）是迈克尔逊干涉仪的改进形式，只是迈克尔逊干涉仪中的镜子被固定衍射光栅所取代。这种设计消除了对入射狭缝的需求，这在色散光谱仪中是必需的，并且消除了在现代迈克尔逊干涉仪中使用移动镜扫描光谱的需求。在先前的研究中，已经评估了各种SHRS变体，例如独立式双光栅SHRS、单光栅SHRS（1g-SHRS）、单片SHRS（mSHRS）和单光栅mSHRS（1g-mSHRS）。然而，本研究专门关注1g-mSHRS配置。1g-mSHRS和1g-SHRS在固定光栅线密度的情况下增加了光谱范围，同时牺牲了光谱分辨率和分辨能力。mSHRS受益于更高的刚性、没有移动部件以及更小的占地面积。在本研究中，我们研究了探测器的选择如何影响1g-mSHRS系统的性能，特别关注评估三种类型相机的性能：电荷耦合器件（CCD）、增强型CCD（ICCD）和互补金属氧化物半导体（CMOS）相机。使用532nm连续波激光对CMOS和CCD相机以及532nm掺钕钇铝石榴石脉冲激光对ICCD相机，对这些系统进行了地质、有机和无机样品的评估。1g-mSHRS的占地面积为3.5×3.5×2.5cm，质量为272g或80g，这取决于是否包括整体外壳。我们发现，增加沿相机y轴使用的像素数量会提高条纹可见度（FV）并优化分辨率（通过捕获整个光栅并放大条纹）。在y轴上使用的像素数量、芯片尺寸和尺寸会影响系统的信噪比。此外，我们讨论了像素间距对菲佐条纹恢复的影响，包括奈奎斯特频率、混叠和FV之间的关系。
