Vehicle sensor to detect rain drop on and above waveguide utilizing light deflection and scattering was realized, keeping wide\nsensing coverage and sensitivity to detect mist accumulation. Proposed sensor structure under stacked light wave guide consisted\nof light blocking fixture surrounding photodetector and adjacent light source. Tilted air gap between stacked light waveguide and\nlight blocking fixture played major role to increase sensitivity and to enhance linearity. This sensor structure eliminated complex\ncollimating optics, while keeping wide sensing coverage using simple geometry. Detection algorithm based on time-to-intensity\ntransformation process was used to convert raining intensity into countable raining process. Experimental result inside simulated\nrain chamber showed distinct different response between light rain and normal rain. Application as automobile rain sensor is\nexpected.
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