红外窗口材料的热辐射特性测量方法

飞行器在大气层内高超声速飞行时,高温窗口迅速成为气动热辐射效应的主要因素,气动热辐射效应会降低甚至破坏红外(IR)探测系统的性能.通过分析红外探测窗口热辐射传输特性,提出一种红外窗口材料的热辐射特性测量方法,并测量了应用于中波红外(MWIR)探测系统的某蓝宝石红外窗口材料在高温状态下的透过率和自身辐射等热辐射数据.结果表明:在100~350℃范围内,0.1 mm厚蓝宝石材料薄层在中波红外3.7~4.8μm波段的热辐射特性与温度近似呈3次方关系,温度越高,蓝宝石透过率越小,自身辐射越大.强烈的自身辐射极易导致红外探测器局部饱和现象,对探测系统造成的影响比透过率引起的信噪比(SNR)下降要大得多.

Measurement method for thermal radiation characteristics of IR window materials

When a hypersonic vehicle is flying in the atmosphere, serious aero-thermo-radiation effects can reduce or even destroy the performance of infrared (IR) detection, and high-temperature IR window becomes the main factor of the effects due to the aerodynamic heating. Based on thermal radiation transfer model for IR window, a method was proposed to measure thermal radiation characteristics of IR window materials. And thermal radiation characteristics of a sapphire IR window material applied to mid-wave infrared (MWIR) detection system were measured. The results indicate that thermal radiation characteristics of the sapphire IR window material with thickness of 0.1mm, in the wavelength region 3.7-4.8μm, have an approximate cubic relationship with temperature, changing from 100℃ to 350℃. With the rise of temperature, the transmittance decreases, while the self-radiation increases. The intensive self-radiation can make detector into saturation state easily, of which the influence on the MWIR detection system is bigger than that of transmittance which decreases detecting signal to noise ratio (SNR).