| 摘要 |
<p>The invention provides a lantern for an area light, particularly one having a cut-off light distribution. A central area of a transparent or transluscent bowl of the lantern has in alternation externally facing reflecting prisms and flats. There are sufficient flats to transmit at least one third of the vertical light and sufficient proportion of prisms to provide a completely flashed prism bank at the direction of peak intensity which is preferably 60.degree.- 65.degree. from the vertical. The prism bank controls the vertical light, so that the intensity in a vertical 60.degree. cone does not exceed 80% of peak intensity, more efficiently than internal prisms. The flats have the additional advantage of facilitating ease of cleaning.</p> |
