傅里叶变换光谱仪多次反射杂光对调制度的影响分析

Analysis of Stray Light Influence to Modulation on Fourier Transform Spectrometer

为满足遥感探测领域对高光谱干涉探测仪的高信噪比和高光谱分辨率的要求,针对我国目前在研高光谱分辨率傅里叶变换光谱仪,详细分析了采用分束器及补偿器分光方案的迈克尔逊干涉仪中,增透面上多次反射杂光对光谱仪调制度的影响。分析表明增透面透过率越低,光谱仪调制度越低。理论分析发现,引入分束器和补偿器的楔角和倾斜角可以实现正常光斑与多次反射光斑分离,从而减弱甚至消除多次反射杂光的影响。通过理论计算给出了二次反射杂光与正常光路夹角与楔角和倾斜角的关系式,并依据光斑分离要求确定了楔角和倾斜角优化方法。由于干涉仪结构参数的相互关联特性,在优化楔角和倾斜角后,需要对入射角进行调整,使得反射光路与透射光路关于分束面对称,以消除其对光谱分辨率的影响;需要对补偿器厚度进行调整匹配,消除由于角度调整引入的正常光路光程差改变导致的调制度下降。按此步骤进行设计优化,在保持原有高精度设计指标的前提下,可消除干涉仪多次反射杂光的影响,该干涉仪优化设计步骤及结构参数调整方法适用于采用分束器补偿器分光方案的傅里叶变换光谱仪。

In the remote sensing application,the interferometer,especially Fourier Transform Spectrometer,is required to be of high spectral resolution and high signal to noise(SNR).Therefore,the modulation reduction caused by stray light,which is introduced by multiple reflections of beam splitter and compensator,has been analyzed in detail in this paper.Based on theoretical analysis,the wedge angle and inclination angle are respectively introduced in beam splitter and compensator,which can reduce or even eliminate the influence of stray light by spot separation.The relationships among spot separation angle,wedge angle and inclination angle are given by theoretical formula,which can be used to optimize wedge angle and inclination angle.For the connection of structural parameters,the angle of incidence need to be adjusted with thewedge angle and inclination angle to keep the symmetry of reflected light and transmission light about splitting surface and eliminate the effect on spectral resolution.And then,the thickness of compensator also need to be adjusted,for eliminating the effect of optical path difference changing of regular optical light.The influence of the multiple reflections stray light can be eliminated by following these steps.Therefore,an optimization design method is obtained,which is suitable for the Fourier transform spectrometer using the beam splitter andcompensator scheme.