Livada Časlav, Glavaš Hrvoje, Baumgartner Alfonzo, Jukić Dina
Faculty of Electrical Engineering, Computer Science and Information Technology Osijek, Josip Juraj Strossmayer University in Osijek, Kneza Trpimira 2B, 31000 Osijek, Croatia.
J Imaging. 2023 Jul 12;9(7):143. doi: 10.3390/jimaging9070143.
Thermography is probably the most used method of measuring surface temperature by analyzing radiation in the infrared part of the spectrum which accuracy depends on factors such as emissivity and reflected radiation. Contrary to popular belief that thermographic images represent temperature maps, they are actually thermal radiation converted into an image, and if not properly calibrated, they show incorrect temperatures. The objective of this study is to analyze commonly used image processing techniques and their impact on radiometric data in thermography. In particular, the extent to which a thermograph can be considered as an image and how image processing affects radiometric data. Three analyzes are presented in the paper. The first one examines how image processing techniques, such as contrast and brightness, affect physical reality and its representation in thermographic imaging. The second analysis examines the effects of JPEG compression on radiometric data and how degradation of the data varies with the compression parameters. The third analysis aims to determine the optimal resolution increase required to minimize the effects of compression on the radiometric data. The output from an IR camera in CSV format was used for these analyses, and compared to images from the manufacturer's software. The IR camera providing data in JPEG format was used, and the data included thermographic images, visible images, and a matrix of thermal radiation data. The study was verified with a reference blackbody radiation set at 60 °C. The results highlight the dangers of interpreting thermographic images as temperature maps without considering the underlying radiometric data which can be affected by image processing and compression. The paper concludes with the importance of accurate and precise thermographic analysis for reliable temperature measurement.
热成像可能是通过分析光谱红外部分的辐射来测量表面温度最常用的方法，其精度取决于发射率和反射辐射等因素。与普遍认为热成像图像代表温度图的观点相反，它们实际上是转换为图像的热辐射，如果没有进行适当校准，就会显示不正确的温度。本研究的目的是分析常用的图像处理技术及其对热成像中辐射数据的影响。特别是，热成像仪在多大程度上可被视为一幅图像以及图像处理如何影响辐射数据。本文提出了三项分析。第一项分析研究了对比度和亮度等图像处理技术如何影响物理现实及其在热成像中的呈现。第二项分析研究了JPEG压缩对辐射数据的影响以及数据退化如何随压缩参数而变化。第三项分析旨在确定将压缩对辐射数据的影响降至最低所需的最佳分辨率提升。这些分析使用了CSV格式的红外相机输出，并与制造商软件中的图像进行比较。使用了提供JPEG格式数据的红外相机，数据包括热成像图像、可见图像以及热辐射数据矩阵。该研究使用设置为60°C的参考黑体辐射进行了验证。结果凸显了在不考虑可能受图像处理和压缩影响的基础辐射数据的情况下将热成像图像解释为温度图的危险性。本文最后强调了准确精确的热成像分析对于可靠温度测量的重要性。
