Department of Computer Science, Norwegian University of Science and Technology, Gjøvik, Norway.
IRIMAS, EA7499, Université de Haute-Alsace, Mulhouse, France.
PLoS One. 2024 May 9;19(5):e0303018. doi: 10.1371/journal.pone.0303018. eCollection 2024.
We study the relationship between reflectance and the degree of linear polarization of radiation that bounces off the surface of an unvarnished oil painting. We design a VNIR-SWIR (400 nm to 2500 nm) polarimetric reflectance imaging spectroscopy setup that deploys unpolarized light and allows us to estimate the Stokes vector at the pixel level. We observe a strong negative correlation between the S0 component of the Stokes vector (which can be used to represent the reflectance) and the degree of linear polarization in the visible interval (average -0.81), while the correlation is weaker and varying in the infrared range (average -0.50 in the NIR range between 780 and 1500 nm, and average -0.87 in the SWIR range between 1500 and 2500 nm). By tackling the problem with multi-resolution image analysis, we observe a dependence of the correlation on the local complexity of the surface. Indeed, we observe a general trend that strengthens the negative correlation for the effect of artificial flattening provoked by low image resolutions.
我们研究了未上光油画表面反射光的反射率与线性偏振度之间的关系。我们设计了一个 VNIR-SWIR（400nm 至 2500nm）偏振反射成像光谱设置，该设置采用非偏振光，并允许我们在像素级别估计 Stokes 矢量。我们观察到 Stokes 矢量的 S0 分量（可用于表示反射率）与可见光范围内线性偏振度之间存在很强的负相关（平均 -0.81），而在红外范围内相关较弱且变化（在 NIR 780nm 至 1500nm 范围内平均 -0.50，在 SWIR 1500nm 至 2500nm 范围内平均 -0.87）。通过使用多分辨率图像分析来解决这个问题，我们观察到相关性与表面局部复杂性有关。实际上，我们观察到一种普遍趋势，即随着图像分辨率降低导致的人工平滑效果的增强，负相关性也随之增强。
