| 摘要 |
PURPOSE:To prevent the detection of excessive quantity of light in a tunnel by totally reflecting incident light missing a range necessary for detecting quantity of light from a lower surface part, by providing a plurality of notches to an upper surface part at a predetermined angle and using the lower surface part as a flat surface filter. CONSTITUTION:A diamond cut filter 2 is held to a case through a dust preventing filter 1 and a light sensor 4 comprising a photodiode for detecting light from the upper part of a vehicle is mounted under the filter 2. The diamond cut filter 2 has a plurality of notches provided to the upper surface part thereof at a predetermined angle and has a lower surface part made flat and incident light missing a predetermined range is totally reflected from the lower surface part. By this constitution, illuminated light in a tunnel missing the predetermined range is not detected. Therefore, if this apparatus is adapted to a head lamp automatic lighting and extincting apparatus, a head lamp can be certainly lighted at the time of running in a tunnel. |
