摘要 |
PROBLEM TO BE SOLVED: To prevent reflection of a laser beam due to an adhering water drop and reflection and refraction of a reflected wave from an obstacle received by a sensor by providing a surface layer containing photocatalyst titanium oxide particles where a laser beam can be transmitted on the surface of a transparent cover and/or an image formation lens. SOLUTION: An inter-vehicle distance detecting device comprises a laser light transmitting part, a receiving part for a reflected wave from an obstacle and a transparent cover. A layer containing a photocatalyst such as a crystalline titanium oxide or the like is formed on the surface of a transparent cover or an image formation lens. As the surface is thus constructed, the surface of the transparent cover or the image formation lens is made phydrophilic to a high degree according to the photo excitation of the photocatalyst. Accordingly, even if moisture in the atmosphere condenses to adhere to the above surface, it will not grow into a water drop, but it is uniformly formed into a water film, so that reflection of a pulse laser beam due to an adhering water drop and reflection and refraction of a reflected wave can be prevented effectively. |