| 摘要 |
A system for producing a beam of light with a small vertical angular spread and a wide horizontal angular spread comprises an annular prism 1 adjacent to a ring of light emitting diodes 2. Light from the LEDs is collimated by a lower toric surface 3, totally reflected by an inverted-conical inner surface 4 and then refracted through a conical outer surface 5. The LEDs may produce white or coloured light and are conventionally mounted on a printed circuit board. The prism and diodes may form only a partial ring so that the light beam is restricted in horizontal angular spread. The toric refracting surface may be replaced by a ring of abutting axially-symmetric refracting surfaces (11,fig.4) each having an LED at its axis. A stackable and sealable assembly may be formed with one prism unit being placed on another (fig.5). |
