| 摘要 |
PURPOSE:To judge a snowy road by receiving light modulated through a strobe and reflected from a pavement by means of a blue single color sensor, then transmitting the light through a filter and a peak hold circuit to a comparator, and comparing with a predetermined value, and when it is higher than the predetermined value and the temperature is lower than 0 deg.C, eliminating influence of external light such as solar rays. CONSTITUTION:When a contactless temperature sensor 17 such as a radiation thermometer detects temperature lower than 0 deg.C, a comparator 18 outputs a high level signal H to a strobe driving section 19. The strobe driving section 19 resets a peak hold circuit 21 to actuate a strobe 22, and modulated strobe light reflected from a pavement is received by means of a blue single color sensor 23 then transmitted through a high-pass filter 25 and the peak hold circuit 21 to a comparator 26 where it is compared with a predetermined value, and if it is higher than the predetermined value and the temperature is lower than 0 deg.C, the pavement is judged to be snowy. Consequently, judgement of snowy road can be made accurately without influence of external light such as solar rays.
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