| 摘要 |
<p>PURPOSE:To decrease a spreading angle of luminous flux and increase light utilization by installing a reflecting mirror having a circular arc cross section in the position facing a transparent window of a fluorescent tube and arranging the mirror so that two focuses of an ellipse coincide with both ends of a transparent window. CONSTITUTION:A fluorescent tube 6 is constructed in such a way that a reflecting mirror 9 is installed on the inner surface of a glass tube with a belt zone left which serves as a transparent window 8 and coated with a fluorescent material thereon. A reflecting mirror 11 having a elliptic cross section reflecting surface 12 and a narrow window 14 in its center is arranged in the position facing the transparent window 8 and adjusted so that two focuses 13 and 14 of an ellipse coincide with both sides 15 and 16 of the transparent window 8. Incident rays entered from the transparent window 8 to the reflecting surface 12 are returned to the transparent window by reflection and enters the fluorescent surface 10, and after repeating diffusion reflection, come out from the transparent window 8. Therefore, a spreading angle of luminous flux is decreased and light utilization is increased.</p> |
