| 摘要 |
Light emitted from an LED lamp (1) substantially vertically enters a surf ace of a first light diffusion structure (2) to be diffused within a prescri bed flat surface (P) orthogonally intersecting with the longitudinal directi on of a protrusion of the light diffusion structure (2), and enters a surfac e of a second light diffusion structure (3) as a luminous flux which is flat and has a prescribed expansion angle. Though the entry angle to the second light diffusion structure (3) varies corresponding to the angle of light pas sed through the first light diffusion structure (2), light expansion in the width direction (W) is suppressed by the second light diffusion structure (3 ) to be within a range of suitable diffusion angles, and a flat luminous flu x (B) having high directivity is formed.
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