| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical element that has a first and second transparent layers laminated and that can emit incident light from an end face in a direction vertical to the light-emitting surface with high efficiency, and also to provide a surface light source device that, using such optical element, can illuminate with sufficient luminance in the vertical direction to the light-emitting surface of the optical element and that can reduce the manufacturing cost. SOLUTION: The optical element is provided with the first and second transparent layers 1, 2 having a refractive index different by 0.1 or more and laminated. The boundary 3 of the first and second transparent layers 1, 2 is made to have a minute rugged shape for the purpose of controlling the travelling direction of the incident light to this boundary 3. In addition, the thickness of the first transparent layer having a larger refractive index of the two transparent layers 1, 2 is designed to be 0.1-300μm. COPYRIGHT: (C)2006,JPO&NCIPI
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