| 摘要 |
PURPOSE:To achieve homogeneous luminous intensity distribution by coating the inner surface of the emission tube with a light-diffusing film and making at least one of areas of the inner surface located near the fusing sections to be either uncoated or coated with the thin portion of the light-diffusing film. CONSTITUTION:A part of the light reaching the main section 15 of an emission tube 1 is multiply reflected by a light-diffusing film 13 before reaching areas 14 located near fusing sections 5 and 5. Since the areas 14 are either uncoated or coated with parts of the ligh-diffusing film 13 thinner than its part located on the main section 15, most of the multiply reflected light and the light directly reaching from the arc to the areas 14 is discharged outside the emission tube 1 through its wall. Therefore, as compared to an emission tube having an uncoated inner surface or an emission tube the entire inner surface of which is coated with a light-diffusing film, the amount of light directed toward the fusing sections 5 and 5 can be increased in this emission tube 1. Accordingly, when the emission tube 1 is ignited in vertical position, increased luminous intensity is achieved right under the tube 1 thereby improving its luminous intensity distribution. |
