Spectral properties of multilayered oak leaves and a camouflage net: experimental measurements and mathematical modelling

The development of state-of-the-art surveillance technology forces nations to develop camouflage with advanced capabilities. Owing to the abundance and wide distribution of leaves, their spectral properties are often mimicked by camouflage material to decrease the conspicuity of the user operating in woodland theaters. Before interacting with the covered object or soil, light usually interacts with several leaf layers, for example through tree canopies. Knowledge of the spectral characteristics of multi-layered leaves is therefore essential to utilize remote sensing applications and for the endeavor to develop undetectable camouflage materials mimicking nature. The literature is currently scarce on research investigating both the spectral characteristics of multi-layered leaves and camouflage material. In this work, we intend to reduce the knowledge gap with studies on the spectral properties of multiple layers of oak leaves and a generic camouflage net. We measured the reflectance and transmittance of samples with 1–8 layers between 250–2500 nm and found that wavelengths and samples differ in penetration depths. The penetration depth ranged from just a couple of layers for visible light to tree or six layers at infrared wavelengths for the camouflage net and leaf samples, respectively. Moreover, we fitted the reflectance data of the samples with an uncomplicated plate model, here named the extinction model, which we used at selected wavelengths to estimate the transmittance and absorptance values of the multi-layered samples. The model predicts the spectral values of the samples with high accuracy, especially those of the leaf samples, and proves to be a promising tool that may replace experiments due to time restrictions or limited resources.