Three-Dimensional Imaging and Reconstructions of Objects Under Rainy Conditions Using the Generation and Propagation of Coherent Structured Signal

This investigation is aiming at the development of a method for in-situ 3D imaging and reconstructions of objects in the rain. The proposed method is based on the use of monochromatic sinusoidal fringe pattern generated by the designed optical system, the polarization technique, and the Fourier-transform-based algorithm of reconstruction. Based on the theoretical analyses and experimental results, it shows that the generated laser-beam-based signal keeps being coherent until reaching the observed object. The coherence of the projected sinusoidal signal is the key feature of the proposed method and ensures the accuracy of measurement and reconstruction of objects under rainy conditions. Moreover, the effects resulted from the spectral absorption and multiple scattering on the propagation of the projected sinusoidal fringe pattern in the rain can be removed using the polarization technique. The developed method is capable of obtaining accurate 3D reconstructions of the objects under rainy conditions together with background illumination, the multiply-scattered light, the vibration from environmental influences including the wind, and the inhomogeneous medium of rain. The application of this method does not suffer the limitation of focusing, precise synchronization, and the speed of measurement that might be a problem for the time-of-flight technique and digital-light-processing-based profilometry.