In numerous applications, including current body temperature monitoring in viral pandemic management, thermal imaging cameras are used for quantitative measurements. These require determination of the measurement accuracy (error) and its traceability (measurement uncertainty). Within error estimation, the size-of-source effect (SSE) is an important error source. The SSE is the relation between the physical size of a target and the instrument’s nominal target size. This study presents a direct evaluation of the error due to the SSE. A stable and uniform temperature, generated by blackbodies, was measured by a high-quality thermal imager. To limit the generated radiation, custom-made blocking tiles with different apertures were used. Effects of aperture shapes and positions, camera-target distances and temperature levels on the error were investigated. The study findings suggest that due to the SSE the measured temperatures are too low, especially at longer camera-target distances. The SSE error depends on the number of pixels available and included into the region of interest, for which the accurate measurement is about to be performed. For an accurate temperature measurement, an array of at least 10 × 10 pixels should be exposed to the observed target radiation, while 3 × 3 central pixel area should be included in the temperature calculation.

中文翻译：

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红外热像仪中源尺寸效应的评估

在许多应用中，包括病毒大流行管理中的当前体温监测，热像仪都用于定量测量。这些要求确定测量精度（误差）及其可追溯性（测量不确定性）。在误差估计中，源大小效应（SSE）是重要的误差源。SSE是目标物的物理尺寸与仪器标称目标物尺寸之间的关系。这项研究提出了由SSE引起的错误的直接评估。由黑体产生的稳定且均匀的温度由高质量的热成像仪测量。为了限制产生的辐射，使用了具有不同孔径的定制阻隔砖。光圈形状和位置的影响，研究了相机目标距离和温度水平对误差的影响。研究结果表明，由于SSE的影响，测得的温度太低，尤其是在更长的相机目标距离下。SSE误差取决于将要进行精确测量的感兴趣区域中可用像素的数量。为了进行精确的温度测量，应将至少10×10像素的阵列暴露在观察到的目标辐射下，而温度计算应包括3×3中心像素区域。为此，将要执行准确的测量。为了进行精确的温度测量，应将至少10×10像素的阵列暴露在观察到的目标辐射下，而温度计算应包括3×3中心像素区域。为此，将要执行准确的测量。为了进行精确的温度测量，应将至少10×10像素的阵列暴露在观察到的目标辐射下，而温度计算应包括3×3中心像素区域。