波长积分双色法及其测温精度分析

Two-color Method by Wavelength Integration and Its Temperature Measurement Precision Analysis

现代彩色高速高分辨率相机内部配置了广谱的红、绿、蓝拜尔滤镜,既可获得丰富的火焰图像信息,也可以根据所得彩色火焰图片,基于火焰中碳烟的辐射,利用双色法计算火焰的温度。本文比较系统地阐述了波长积分双色法的基本原理,介绍了图片像素值插值方法,成像系统光学响应系数测定、黑体表征温度标定,以及火焰温度和碳烟KL因子分布的计算过程。本文利用彩色CMOS高速相机和波长积分双色法测量了蜡烛火焰温度,以热电偶测温结果为基准,发现高速相机内部的散粒噪声会使测温结果产生约3%的误差,采用基于原始单色灰度值的线性插值算法可使最大相对误差率绝对值降低约1.5%。与厂商通用的光学响应系数相比,采用本文自测的光学响应系数来计算,能够使最大相对误差率绝对值降低约3.3%。与定波长双色法相比,波长积分双色法的最大相对误差率绝对值降低约5.1%.最终本文波长积分双色法在所研究范围内的最大相对误差率绝对值约为3.1%。除蜡烛火焰外,本文方法适用于其他含碳烟火焰。

Modern high-speed and high-resolution color cameras are equipped with red,green and blue broad band spectrum Bayer filters,which makes them easy to obtain abundant flame images and to calculate flame temperatures by two-color method based on radiations of soot in the flames.This paper systematically introduced the two-color method by wavelength integration,including the development of color interpolation algorithm,measurement of the optical system response coefficient,calibration of blackbody apparent temperature,and the solving process of the flame temperature and soot KL factor distribution.The candle flame temperature was measured using high-speed CMOS color camera and wavelength integration two-color method.Regarding radiation-corrected thermocouple temperature as the criterion,the results showed that the shoot noise in the camera brought about 3% error,the absolute value of the relative error rate decreased about 1.5% when using the in-house linear interpolation algorithm to synthetize colorful images based on the raw gray image pixel values.Using the optical system response coefficient calibrated by this paper,instead of the manufacturer’s general camera response coefficient,the absolute relative error rate reduced about3.3%.The maximum absolute relative error rate of the wavelength integration two-color method in this paper was finally reduced to be about 3.1%.The wavelength integration two-color method and its precision analysis of this paper is thought to be applicable for other sooty flames.