| 摘要 |
A sensor (20, 100, 200, 300) for detecting the approach and exit of a vehicle (42) to a tunnel (46). In one embodiment there is a sensor (20, 100, 200, 300) with a photodiode (22a) that receives light through an inclined channel (30, 30') or aperture (32, 332, 432). The channel provides a field of view (44, 344, 31) ahead and above the vehicle. The photosensor (22a) is thus sensitive to the change in light from this field of view (44, 344, 31) as a vehicle enters (46a) and exits (46b) a tunnel (46). Some embodiments of the present invention include a second photosensor (22b) with a wider field of view (112, 112'', 111) for detecting ambient light. |
