Multi-objective optimization method for light-field multi-spectral pyrometer
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摘要: 多光谱测温是一种应用广泛的非接触式测温方法。针对多光谱高温计分光系统复杂的问题,本文设计了基于光场相机的光场多光谱高温计,用简洁的光学系统即可实现二维高温测量。光场相机可同时记录入射光线的方向和强度,通过在相机主镜头前放置滤波片阵列,光线的方向信息被替换为光谱信息,使得图像传感器可同时获取光线的光谱和强度。在光谱发射率未知的情况下获得被测对象温度,是多光谱数据处理中亟待解决的难题。常用的发射率假设模型法无法广泛应用于各种材料的温度测量。本文提出了一种基于多目标优化的多光谱温度反演方法,无需发射率先验知识即可精确求解被测对象真实温度和光谱发射率。该方法根据辐射方程建立多目标函数,设置发射率约束条件,并采用惩罚函数法求解约束优化问题。黑体炉标定实验结果表明:该方法的测量误差小于1%,表明了所提出的光场多光谱测温硬件设计及温度反演方法的可行性和可靠性。Abstract: A light-field multi-spectral pyrometer is designed for two-dimensional, high-temperature measurements. The proposed method is based on an unfocused light-field camera, which can simultaneously record directions and intensities of incident rays. The direction information of rays is substituted by radiation spectrums via placing an array of filters in front of the camera’s main lens, such that the image sensor can simultaneously acquire spectra and intensities of rays. For multi-spectral data processing, how to obtain the accurate target temperature under unknown spectral emissivity is a difficult problem to be solved. A multi-objective optimization method is proposed to obtain the inverse true temperature and spectral emissivity without assuming the emissivity model. In this method, the multi-objective function is established according to the radiation equations. The emissivity constraint conditions are set for the objective function, and the penalty function method is used to solve the optimization problem. The calibration experiment results of the black-body furnace show that the relative error of the light-field multi-spectral pyrometer method is less than 1%, which proves the feasibility and reliability of the proposed design and temperature inversion method.
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表 1 光场多光谱高温计参数
Table 1. Parameters of the light-field multi-spectral pyrometer
参数 值 滤波片波长(λi ± 10 nm) 470, 500, 530, 575, 620, 670 微透镜阵列像素 800像素 × 600像素 微透镜阵列尺寸 25 mm × 18 mm 单个微透镜尺寸/µm 28 微透镜焦距/µm 510 传感器像素 7915像素 × 5436像素 传感器尺寸 22 mm × 15 mm 像元尺寸/µm 2.8 -
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