| 摘要 |
PURPOSE:To make it possible to detect the wetting condition of a road surface by using a polarizing plate, and measuring the intensity of the polarized component of the light reflected on the road surface. CONSTITUTION:Natural light R reflected on a pavement is transmitted through a polarizing plate F and received with a photoelectric conversion element N. A voltage E is outputted in response to the intensity of the polarized component from the photoelectric conversion element N. A measuring means H measures the change in output voltage from the photoelectric conversion element N. When the road surface is wet, the road surface becomes smooth surface because of the water surface. The amount of light reflected on a pavement is increased as compared with the case where the pavement U is dry. Therefore, the output voltage from the photoelectric conversion element N is increased. At the same time, of two kinds of the polarized lights contained in the light reflected on the pavement, the reflectance of the polarized component of the P polarized light, which is in parallel with the incident surface, is attenuated. However, the reflectance of the polarized component of the S polarized light, which is orthogonal to the incident surface, becomes higher than that of the P polarized light. Therefore, the change in output voltage can be excellently detected by receiving the S polarized light among the polarized components with the polarizing plate F. Thus, the wetting condition of pavement can be excellently detected. |
