| 摘要 |
PURPOSE:To enhance both of the uniformity ratio of luminance and the luminance by a simple constitution by forming a recessed part on one surface of a diffusion plate and inserting a diffusion sheet in the recessed part in an illumination device provided with a light source and the diffusion plate diffusing light from the light source. CONSTITUTION:A lamp case 12 is obtained by forming the rectangular recessed part 14a on the upper surface of the diffusion plate 14 placed and fixed on the aperture end part thereof. Then, the rectangular diffusion sheet 15 thinner than the plate 14 is not stuck but merely inserted in the recessed part 14 with play. Therefore, since the light from a fluorescent lamp 13 is doubly diffused by the plate 14 and the sheet 15, the diffusivity thereof is enhanced and the uniformity ratio of the luminance on the upper surface of the sheet 15 is enhanced in comparison with the case that the light is diffused only by the plate 14. Simultaneously, the luminance is enhanced by about 10%, for example. Besides, even when the sheet 15 and the plate 14 are heated by the heat generation of the lamp 13, the uniformity ratio of the luminance and the luminance are prevented from being lowered caused by such deformation that the sheet 15 is curled or the outside edge thereof waves. |
