| 摘要 |
PURPOSE:To obtain a thin plane light source improved at the light projecting efficiency of a back light source of a liquid crystal display cell by guiding light radiated from a light source arranged in a light guiding part as reflected light having directivity through a light converging part connecting a photoconductive plane to the light guiding part and thinned in the direction to the light guiding part. CONSTITUTION:The size of the plane optical source can be approximately equal to that of a CRT and a light projecting panel can be thinned independently of the size of a light size such as a fluorescent lamp. Namely, the light source A is included in the photoconductive part 2, light converting part 10 connects the photoconductive part 2 to the light guiding part 4 and is thinned in the direction to the light guiding part 4 and a light reflecting plane 8 is formed so that light converged by the light converging part 10 is led into the light guiding part 4 as reflected light 5 and reflected at an angle directed to a light projecting plane 3. Even if the thickness of the light guiding part 4 is set up thinner than the diameter of the fluorescent lamp A, light led into the light projecting panel B reaches the light projecting plane 3 without reducing its photoconductive efficiency.
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