PURPOSE: To detect condition of frozen road surface accurately without being affected by sprayed snow-melting agent and variation in meteorological conditions, ete., by detecting condition of freezing by determining difference in near infrared absorption between water and ice using a road surface condition determining circuit.
CONSTITUTION: A light-projecting passage 3 is attached to the top of a supporting column 5, and an infrared ray receiver 1 and a visible light receiver 2 are attached to a supporting arm 6. An infrared ray reflecting light signal put out from the light receiver 1 is amplified to an appropriate level by an amplifier 11 and sent over to a low region passing filter 12 to have the outside turbulence noise removed and then put into comparators 13 and 14. A visible light reflecting light signal put out from the light receiver 2 is also processed in the same manner. A discriminating level A1 is set between output level of a filter 12 in frozen condition and the same output level in snow-covered or wet condition, and an output 1 is generated when the output A1 is exceeded.
KOTAKE TAKATERU
MATSUOKA SEIYA
NAKANO MASAGASHI
HIRAO IICHI
YAMAZAKI TAROU
IBA KUNIO
REO GIKEN KK