| 摘要 |
PURPOSE:To decrease a spreading angle of luminous flux and increase light utilization by installig 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 its curvature center is located in the center of the 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 circular arc 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 its curvature center 13 is located to arround the center of the transparent window. The light entered from the transparent window 8 consists of incident rays to the window 14 and those to the reflecting surface 12. The latter is returned to the transparent window and enters the fluorescent surface 10, and after repeating diffusion reflection, comes out from the transparent window 8. Therefore, a spreading angle of luminous flux is decreased and light utilization is increased. |
