| 摘要 |
<p>There is described an optical free space signalling system having an optical device comprising a lens and a plurality of optical elements. A beam deflector for deflecting light beams is provided in an optical path between the lens and the plurality of optical elements. The bean deflector has a plurality of beam deflecting elements with each beam deflecting element being associated with a respective optical element and being operable to deflect a principal light ray passing through the lens so that the principal light ray is substantially perpendicular to the associated optical element. The optical device has particular, but not exclusive, relevance to retro-reflecting systems.</p> |
