JPS576339A - Discriminating device for state of road surface - Google Patents

Abstract

PURPOSE:To accurately know the dry, wet, snow cover and frozen states of road surfaces by discriminating the states of the road surface based on the photodetection signals of the specular and irregular reflected light of visible light from the surface and the irregular reflected light of infrared light. CONSTITUTION:A light projector 24 of a mercury arc lamp contg. not only visible light but also near infrared light in emission spectral, an irregular reflected light detector 25 including photodetectors 31, 32 for infrared light and visible light, a specular reflected light detector 26 including a photodetector 33 for visible light, and a thermometer 28 are mounted to a stanchion erected on one side of a road. The outputs from the photodetectors 25, 26 are removed of noise components by passing through a band-pass filter 35, after which they are rectified and are sent to comparators 41, 42, 43. The reference levels corresponding to the dry, wet and snow cover states of road surfaces have beforehand been set in these comparators, and the signals from the photodetectors are compared with these reference levels. The compared output signals thereof are sent to a logical circuit 44, and an arithmetic processing part 45, by which the above-mentioned states of the road surface are decided. The freezing state of the road surface is decided by the signal of the thermometer 28.