成像狭缝对热红外高光谱成像仪接收能量的影响

Effect of Slit on Energy Received by Pixel of Thermal Infrared Hyperspectral Imager

摘要:

由于热红外高光谱成像仪的狭缝宽度与成像波长在同一量级,光在其内部传播时能量发生损失而不能全部被探测器像元接收,因此基于几何光学的计算像元能量的方法已不再适用。为了探究能量损失情况,采用时域有限差分方法计算了热红外高光谱成像仪中光聚焦入射狭缝前表面时狭缝后光强的分布,并利用瑞利-索末菲矢量衍射理论得到了远场光强分布,从而分析了不同狭缝宽度、狭缝厚度时能量的损失情况,并搭建了实验装置进行验证。结果表明,随着狭缝宽度增加,能量损失逐步减小,且能量主要是由于狭缝后方光波衍射导致能量不能全部进入后级成像镜头而损失,在狭缝内部损失的能量很少。当狭缝宽度为几十微米量级时,狭缝厚度对能量损失影响不大。

Abstract:

Since the slit width of the thermal infrared hyperspectral imager is in the same order of magnitude as the imaging wavelength, the light energy is lost and cannot be fully received by the detector pixel during its internal propagation, so the method of calculating pixel energy based on geometrical optics is no longer applicable. In order to investigate the energy loss, the finite difference time domain method was used to calculate the distribution of light intensity behind the slit when the light was focused on the front surface of the slit in the thermal infrared hyperspectral imager. The far field intensity distribution was obtained by using Rayleigh-sommerfeld vector diffraction theory. The energy loss in different slit widths and thickness was analyzed, and an experimental device was built to verify it. The results show that with the increase of slit width, the energy loss decreases gradually, and the energy loss is mainly due to the light wave diffraction behind the slit, which results in the energy loss that not all energy can enter the post-imaging lens, and the energy loss inside the slit is very small. When the slit width is tens of microns, the slit thickness has little effect on energy loss.