可见近红外波段无人机载成像光谱仪设计

Design of Visible Near Infrared Imaging Spectrometer on Unmanned Aerial Vehicle

为了满足地物成像光谱分析的需要,设计了同轴安装、体积小、重量轻的适用于无人机载的棱镜-光栅-棱镜型可见近红外成像光谱仪.通过角放大率选择、光焦度分配、相对孔径计算设计了视场较大的前置物镜;通过光栅方程求解、体相位全息光栅布拉格条件约束、棱镜折射定律设计了光谱系统的初始结构;通过工作光谱上下限出射角与探测器光谱维宽度的关系确定了成像物镜的焦距;通过出射光角度明确了出射光谱的非线性.设计的无人机载成像光谱仪工作光谱范围为400~1 000nm,视场角为40°,全工作波段在空间截止频率20.8lp/mm处的传递函数值均大于0.67,光谱分辨率小于3nm.装调了无人机载成像光谱仪对室外绿化树木进行光谱推扫成像实验,实现了树叶的多光谱成像.该成像光谱仪能够有效实现光谱成像,性能良好.

A visible near infrared imaging spectrometer,which is mounted on the unmanned aerial vehicle,was designed for ground objects spectral analysis.The prism-grating-prism structure used in the spectrometer has the advantages of coaxial installation,small size and light weight.Objective lens with large field of view was designed through angular magnification selection,optical focal length distribution and relative aperture calculation.Initial spectral system structure was designed based on grating equation solution,volume phase holographic grating Bragg condition constraint and prism refraction law.The focal length of the objective lens was determined by the relationship between the emission angle and the detector width.The nonlinearity of the emission spectrum was shown by the exit light angle.The designed unmanned airborne imaging spectrometer has the spectral range of 400～1 000 nm and the filed angle of 40°.The transfer function value is greater than 0.67 in the whole spectral range at the cut-off frequency of 20.8lp/mm,and the spectral resolution is less than 3nm.An unmanned airborne imaging spectrometer was assembled for spectral push broom imaging experiments on trees outdoors,and the multi-spectral image of leaves was obtained.The imaging spectrometer can effectively realize spectral imaging,and has good performances.