| 摘要 |
PURPOSE:To control direction property of a light beams from the internal displaying apparatus side and preventing the beams from diverging into a saw teeth part of the prism. CONSTITUTION:In front of a transparent plate 15, a saw-teeth shape prism 25 is formed in such a way that its ridge lines of the top 23 are oriented horizontally running as minute parallel lines. Here, when a power source lamp is turned on, these internal light beams are reflected on the inside wall of the housing 11 to light up the front surface of the displaying plate 13 and they pass a pularized plate 14. At this moment, the internal light beams are incident on the inside wall or other structures and dispersed, trying to pass the plate 14 in all directions, however, a screen 18 interrupts a part of beams emergying, obliquely from the top and bottom directions and only horizontally oriented beam element or staight propagating beams pass through the slits 19 and the transparent plate 15. Consequently, convergent tendency of the beams to the top side of the prism 25 can be prevented and as a result, indications on the inside displaying apparatus can be clearly read through the transparent plate 15.
|
