基于双光栅和柱透镜的高分辨率近红外微型光谱仪

High-Resolution Near-Infrared Micro-Spectrometer With Dual Gratings and a Cylindrical Lens

因为便携、低成本、集成化等优势,微型光谱仪已经成为光谱仪技术发展的重要趋势,其中工作波段在近红外的微型光谱仪,在光纤传感和解调、光纤通信等领域有着非常广泛的应用。但目前的近红外微型光谱仪普遍存在分辨率低、成本高、体积大不便于携带等问题,为此,提出了一种独特的基于双光栅和柱透镜的微型光谱仪结构,开展了理论和实验研究。相对于传统的微型光谱仪结构,新的设计主要有三个特征:使用光纤代替入射狭缝,以减少光能损失;采用双光栅将光束进行二次衍射;使用柱透镜以改变线阵CCD阵列表面的成像尺寸。首先,利用Zemax软件进行了光学设计和仿真分析,光谱范围为1525~1570 nm,光学系统结构在66 mm×40 mm×24 mm的体积范围内,光谱分辨率理论上达到0.2 nm,比未加柱透镜的结构提升了2.5倍。然后,根据理论分析,选购了合适的光电器件进行了系统封装,与匹配的电路模块结合,实现了微型光谱仪的光谱检测功能。光谱仪的光学系统安装在66 mm×40 mm×30 mm的体积范围内,实际测量的光谱分辨率为0.215 nm,与理论结果较为吻合。进一步地,搭建了一套基于该微型光谱仪的光纤光栅温度传感测量系统,该微型光谱仪作为信号解调仪,选择了四个中心波长分别为1534、1538、1542和1545 nm的光纤光栅作为传感器,温度在0~50℃范围内以1℃为间隔连续变化,最终实现了温度实时测量和信号解调,系统温度灵敏度分别达到9.58、9.68、9.69和9.6 pm·℃^(-1),验证了该微型光谱仪的高分辨率和高可靠性。研制的微型光谱仪的子组件可以固定在外壳上,系统内部无可移动元器件,体积小、分辨率高、稳定性好,可应用于其他诸如物质浓度分析、传感信号测量等需要高分辨光谱分析的场合。

Micro-spectrometers have become a significant trend in the development of spectrometer technology because of the advantages of portability,low cost,and integration.The NIR micro-spectrometer is a class of micro-spectrometers operating in the near-infrared band,which has an extensive range of applications in the field of optical fiber sensing and demodulation,fiber-optic communication,etc.However,contemporary NIR micro-spectrometers typically are low resolution,expensive,bulky,and impractical for portability.A unique micro-spectrometer structure with dual gratings and a cylindrical lens is proposed and carriedout theoretically and experimentally.Three major alterations are adopted in the new design compared to the traditional micro-spectrometer structure:optical fibers are used to reduce light energy loss,dual gratings are used to split the beam by secondary diffraction,and the cylindrical lens is used to change the imaging size on the surface of the line-array CCD.The optical path is decreased to a volume of 66 mm×40 mm×24 mm with a spectral resolution of 0.2 nm in the wavelength range from 1525 to 1570 nm according to the simulation analysis with Zemax,which is 2.5 times better than that of spectrometers without a cylindrical lens.Based on the theoretical analysis,suitable optoelectronic devices are selected for system packaging and combined with the irmatching circuit module to realize the spectral detection function of the micro-spectrometer.The optical system of the micro-spectrometer can be installed in a volume of 66 mm×40 mm×30 mm,and the spectral resolution is measured to 0.215 nm,which is in agreement with the theoretical results.Furthermore,a Fiber Bragg Grating(FBG)temperature sensing system based on the micro-spectrometer used as a demodulator is built.Four FBG with central wavelengths of 1534,1538,1542,and 1545 nm were selected as sensors.The temperature varies continuously at 1℃intervals in the 0~50℃,resulting in real-time temperature measurement and signal demodulation with a system temperature sensitivity of 9.58,9.68,9.69 and 9.6 pm·℃^(-1) respectively.So,the micro-spectrometer with-high resolution and reliability is verified.The subcomponents of the micro-spectrometer can be fixed to the shell,which is small in size,high in resolution and good instability.It is expected to be applied to other occasions requiring high-resolution spectral analysis,such as substance concentration analysis,sensing signal measurement,etc.