应用于作物荧光检测的改进型Offner光谱仪设计

Design of an improved Offner spectrometer for crop fluorescence detection

为了对作物进行更灵敏、更高效的生长监测,国内外相继设计了各类高光谱分辨率的光谱仪用来探测叶绿素荧光效率。本文对传统Offner光谱仪系统进行改进,得到了光谱分辨率更高的整体结构。光学系统选用双反望远系统,光谱仪部分采用高刻线密度反射型凸面光栅,实现更高的光谱分辨率。在此基础上,添加放大透镜以满足长狭缝需求,同时得到了一种狭缝-像面在光栅同一侧的Offner结构。利用codeV软件对望远系统和光谱仪部分的初始结构进行优化。结果表明,工作在670~780 nm波段时,光谱分辨率为0.3 nm,在17 lp/mm截止频率下整体调制传递函数MTF>0.75,各视场条件下弥散斑均方根半径RMS<15μm。由此可知,该方法可以满足作物生长叶绿素监测领域的高精度、实时性要求。

To monitor crop growth more efficiently,various kinds of hyperspectral spectrometers have been designed to detect chlorophyll fluorescence.In this paper,the traditional Offner spectrometer system is im-proved,and a structure with a higher spectral resolution is obtained.The double-reflection telescope system is selected,and the spectrometer adopts a highly dense linear reflective convex grating to achieve higher spec-tral resolution.On this basis,an amplifying lens is added to meet the need for a long slit.An Offner structure is obtained with a slit and image plane on the same side of the grating.The initial structure of the telescope system and the spectrometer are optimized by codeV software.The results show that the spectral resolution is 0.3 nm in the range of 670~780 nm,the overall Modulation Transfer Function(MTF)is greater than 0.75 at the cut-off frequency of 17 lp/mm,and the Root Mean Square radius(RMS)of the speckle is less than 15μm.The proposed system can meet the requirements of highly precise real-time monitoring in crop growth chlorophyll detection.