空间调制傅里叶变换光谱仪光谱探测中的大气扰动分析

Analysis of Atmospheric Disturbance on Spectrum Detection by Spatial Modulation Fourier Transform Spectrometer

在利用空间调制傅里叶变换光谱仪对远距离目标进行光谱遥测时,大气湍流扰动引起的入射光场的波前畸变会影响干涉图像和复原光谱的质量。根据大气湍流扰动对光场的相位调制作用,建立了大气湍流的随机相位模型与光场在大气中的分步传输模型,并对大气湍流扰动作用下的干涉图像与复原光谱进行了数值计算,结果显示:大气湍流会导致干涉图像的背景产生低频的强度起伏,并致使复原光谱在低频区域出现伴频噪声。采用统计实验的方法对归一化光谱误差与望远系统入瞳放大率、大气相干长度之间的关系进行统计分析。结果表明:归一化光谱误差的统计均值与望远系统入瞳放大率为准线性正相关,与大气相干长度为非线性负相关。依据归一化光谱误差的统计分析结果便可以根据外场环境的大气相干长度,合理地设计望远系统的入瞳放大率,从而实现对目标光谱的有效探测。

When spatial modulation Fourier transform spectrometer is used to detect the spectrum of remote target, the interferogram and recovered spectrum are influenced by wavefront distortion resulting from atmospheric turbulence disturbance. According to the phase modulation of atmospheric turbulence disturbance on optical field, we build the model of atmospheric turbulence random phase screen and optical field split-step propagation in atmosphere. The interferogram and recovered spectrum affected by atmospheric turbulence disturbance are calculated numerically. The results show that the atmospheric turbulence disturbance causes low-frequency background intensity fluctuation in interferogram, and the concomitant frequency noise appears at the low-frequency region of the recovered spectrum. The relationship between normalized spectrum error and telescope entrance pupil magnification along with atmospheric coherence length is analyzed by statistical experiment method. The results indicate that the statistical mean of normalized spectrum error is linear positive correlated to telescope entrance pupil magnification, and it is nonlinear negative correlated to atmospheric coherence length. According to the statistical result of the normalized spectrum error, in order to realize the effective detection on target spectrum, the telescope entrance pupil magnification can be designed reasonably on the basis of the atmospheric coherence length in outfield environment.