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In this paper, we propose a method for single-pixel 2D/3D imaging to be applied in hyperspectral cameras operating in outdoor applications in unmanned aerial vehicles (UAVs). In rain rich environments, if camera systems operating in the visible range are used, alongside the atmospheric absorption that inevitably takes place, additional interactions occur between the light to be detected and the raindrops that produce Rayleigh and other scattering effects, thus limiting the visibility of the imagers mainly due to induced limitations in what radiation propagation is concerned. To solve this problem, we follow the approach that consists in using InGaAs based single photodetectors or line sensors that operate in the near-infrared (NIR) part of the spectra, in the wavelength range between 905 nm and 1600 nm. Due to the high costs of the few commercially available InGaAs based image sensors, we propose implementing a vision system based on the principle of single-pixel imaging (SPI) using active NIR illumination as a low-cost solution for image sensors in low-light scattering media. The SPI approach allows for the reconstruction of images from the electrical response signals of single InGaAs photodetectors to impinging active NIR illumination patterns created by an array of NIR LEDs. The latter is enabled by applying compression sensing (CS) algorithms. In this work, we aim at improving the quality of the reconstructed 2D images, defining the SSIM > 0.6 and RMSE<0.3 in rain rich scenarios as goal specifications. This SPI approach is additionally used to generate 3D images by applying Shape-From-Shading (SPS) and improving mesh 3D algorithms. By projecting Hadamard active illumination patterns analyzed in different regions of the reconstructed image, we enable scanning Spiral and Hilbert traces for image reconstruction to improve the SSIM level and reduce RMSE level of the reconstructed 2D/3D image obtained in the presence of rain. For testing purposes, we developed a controlled characterization system that enables rain simulation to evaluate the quality of the reconstructed 2D/3D single-pixel images.
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