PURPOSE: To obtain a detecting method that can easily be equipped and detect a road-surface state, especially a snow state with accuracy, by deciding the state of the road surface on the basis of difference in direct reflection factor and diffused reflection factor of infrared rays on the road surface according to the road-surface state and a road-surface temperature.
CONSTITUTION: Of light projected from projector 1 and reflected on road surface 4, light of direct reflection and that of diffused reflection are photodetected by photodetectors 11 and 12 for direct reflection and diffused reflection respectively and then converted into electric signals. By making use of characteristics that the reflection factor of the surface of snow decreases according to a shift from the visual light range to the infrared-ray range, filters 14 and 24 supply comparators 15, 16 and 25 with output signals containing information regarding the state of the road surface. On the basis of the decision result of the road-surface state from comparators and a temperature detection signal from radiation thermometer 31, microprocessor 40 makes the final decision to classify the road-surface state by four kinds of dry, wet, frozen and snow states. Thus, the road-surface state, especially the snow state can be detected with accuracy.
FUKAMIZU HIROSHI
NAKANO MASASHI
MATSUOKA SEIYA
HIRAO IICHI
IBA KUNIO
YAMAZAKI TAROU
REO GIKEN KK