| 摘要 |
<p>The warning light fixed to the top of power transmission pylons has a luminescent tube (8) enclosed by a transparent cylindrical tube (7). A transparent plexiglass or lexan refractor (9) enclosing the cylinder and tube is shaped so the light output is concentrated in an angle of about 30 degrees which is the vertical visibility angle required by aviation authorities. The refractor (9) has a section essentially comprising two opposed circular arcs centred along the axis of the luminescent tube, a distance 'd' from the centre of the tube (CO). The distance 'd' depends on the index of refraction of the refractor and the required angle of view. For a given light output over the required viewing angle a lower power input is requied, or higher visibility is obtained from a given power input.</p> |
