基于 AOTF 成像光谱精密测量技术的研究

摘要

Acousto-Optic Tunable Filter as a new beam splitting elements of spectral imaging.We often regard the diffraction center wavelength which is corresponded with the incident light perpendicular to the incident plane of AOTF as the wavelength of CCD spectral measurement.However,the different positions of target have different incident angles when the incident light en-ter into the AOTF,which will cause error when the CCD actual spectral measurement is compared with the spectral measure-ment of vertical incidence.The characteristics of this system we have used is that the target light imaging on the focal plane of CCD by passing the pre optical system,AOTF and the imaging lens,which have achieved the goal that the target light imaging on the whole system only once.Compared with the system of secondary imaging,the system of first imaging can improve the quality of image and the light energy utilization ratio.Because of the field angle of AOTF is ±3°,we analyzed the regular pattern of the diffraction wavelength changing with angle of incidence and obtained the revised spectrum measurement equation by pro-cessing the real measured value of diffraction wavelength changing with angle of incidence.The experimental results show that its relative error can be reduced an order of magnitude by using the revised equation to measure the spectrum.This method can lay the foundation for improving the measurement accuracy of AOTF imaging spectral in the future.%声光可调滤波器(AOTF)作为光谱成像的一种新型分光元件,在运用其进行成像光谱时,一般选择入射光垂直于 AOTF 入射面时所对应的衍射中心波长为 CCD 的光谱测量波长。但在实际测量中,空间目标不同位置的光线总是以不同的角度进入到 AOTF,这样就导致了 CCD 实际测量的光谱和以光垂直入射时所对应的光谱为测量光谱相比出现误差,影响了光谱的测量精度。采用的成像光谱系统的特点是目标光线经前置光学系统、AOTF 和成像透镜后,聚焦成像于透镜的焦平面上,实现了目标光在整个系统的一次成像。此一次成像与传统的二次成像相比,能够有效的提高光能利用率和成像质量。由于 AOTF 的视场角为±3°,所以通过对 AOTF 视场角范围内衍射中心波长随入射角度变化的实际规律进行了分析研究,并对衍射波长随入射角度变化的实际测量值进行了拟合修正,得到了修正方程。实验结果表明用修正后的方程进行光谱测量,其相对误差值可以减小一个数量级。此方法可为今后提高 AOTF 成像光谱测量精度奠定基础。