| 摘要 |
A diffusion sheet which has a flat incident surface and an output surface parallel to the incident surface, and which comprises a sheet body and a plurality of wedge-shaped portions embedded on the output surface side in the sheet body and spreading toward the output surface side. The wedge-shaped portions are lower in refractive index than the sheet body. The side surfaces of the wedge- shaped portions are formed by bent surfaces, and angles formed by respective bent surface on side surfaces and a perpendicular to the incident surface gradually increase toward the output surface side. The tip ends on the incident surface side of wedge-shaped portions have flat surfaces parallel to the incident surface.
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