Design Of Rain Sensor Based On Infrared Photodetector

With the rapid development of automotive industry and technology, more functions were demanded in automobiles for convenience. Some automatic control functions were required especially. Rain sensor was invited to satisfy this kind of needs of people. The Rain Sensor was a highly versatile device for automatic wiping when sensor area of the vehicle windscreen was wet due to moisture, raindrops or even mud. It became more easier for the drivers to get a clear field of vision without distraction.The operation principles and function of the rain sensor were studied. There were three components that make up the optical system of the rain sensor. The first component was a leading end which was made of an emitting LED with a central wavelength at 906nm and a collimating lens with a 3mm radius curvature; the second component was a LED adopter and a focus lens with a 4mm radius curvature; the third component was the windshield in which area the light from the LED pass ed through.The engineering compute software MATLAB was used to calculate the aspheric surfaces of the collimating lens and the focus lens. The optical design software ZEMAX was used to simulate the beam path of the light from LED which went through the whole optical structure of the rain sensor. The result from the simulation proved that the collimating lens and the focus lens were very effective in improving the sensitivity and reaction speed of the rain sensor.