| 摘要 |
PURPOSE:To obtain correct information on distance between vehicles and the speed of a preceding vehicle by detecting the Doppler beat of light with an optical fiber. CONSTITUTION:Light 2 from a light source 1 goes out into the outside air passing through a beam splitter 3 and matching lens 4, returns to the matching lens 4 reflected from a corner cube reflector 5 mounted at the rear of a preceding vehicle 16 and enters light detectors 7 and 9 reflected with beam splitters 3, 6 and 8. On the other hand, the light-reflected with the beam splitter 3 is divided into transmission light and reflected light with a beam splitter 10 and enters optical fibers 12 and 13 focused with a matching lens 11. The light leaving the optical fibers transmits the beam splitters 6 and 8 matched with the matching lens 14, enters the light detectors 7 and 9 and is mixed with the reflected light. As the distance from the preceding vehicle 16 grows less, the difference in the optical path length reduces between the light in the optical fiber system 12 and the reflected light with the reflector 5, where a Doppler beat is detected with the light detector 9 to indicate that the preceding vehicle comes within a fixed range of distance. In addition, the beat frequency here is proportional to the relative speed to provide information the speed. |
