红外滤光片截止波段等效发射率反演方法

Equivalent Emissivity Inversion Method for Infrared Filters in Cutoff Band

为了实现对红外滤光片辐射特性的量化分析,研究了一种红外滤光片截止波段等效发射率反演方法,并建立了反演方法的基本数学模型。在有、无红外滤光片的情况下,分别对红外成像系统进行辐射定标,并基于定标结果计算红外滤光片截止波段的自身辐射;基于极坐标系下的有限面源至微面源辐射模型,反演红外滤光片截止波段的等效发射率。根据基本数学模型开展了反演实验,在积分时间为0.8ms与4.0ms两种实验条件下对中波红外滤光片进行反演,取两次实验结果的算术平均值(0.420)为等效发射率反演结果,则其等效反射率约为0.580;两次实验结果的相对差异较小,约为1.9%。开展了中波红外滤光片的反射成像实验,证明了其在截止波段具备较强的反射辐射特性,定性地验证了反演实验的结果。

In order to achieve the quantitative analysis of infrared filters＇ radiation characteristics,we propose an equivalent emissivity inversion method for infrared filters in the cutoff band and establish the basic mathematical model of the inversion method.Firstly,in two cases,whether placing the infrared filter in the light path or not,we conduct the radiometric calibration for infrared imaging system and then calculate the self-radiation which is caused by infrared filter in the cutoff band based on the calibration results.Secondly,based on the mathematical model of radiation from the limited surface source to the micro surface source in polar coordinates,we inverse the equivalent emissivity of the infrared filter in the cutoff band.According to the basic mathematical model,we carry out an inversion experiment of a mid-wave infrared（MWIR）filter,in two cases that the integration times are set to 0.8 ms and 4.0 ms.The result of the equivalent emissivity,arithmetic average of inversion values obtained in the two cases,is approximately equal to 0.420,so that the equivalent reflectance is approximately equal to 0.580.The relative difference value of the two experiment cases is small,approximately equal to 1.9%.We conduct the reflection imaging experiment of the MWIR filter.It is proved that the MWIR filter has strong reflective ability of radiation in the cutoff band.What＇s more,the conclusion of the inversion experiment is verified qualitatively by the phenomena of the reflection imaging experiment.