| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical element which achieves highly efficient condensation at low costs and with simple configuration and also which achieves compactification by reducing the diameter of the optical element for the size of a light emitting surface. <P>SOLUTION: The optical element that condenses light emitted from a light source has: an entrance surface where the light enters; an exit surface from which the light entering inside via the entrance surface is emitted; and a reflection surface that directs, to the exit surface by total reflection, part of the light entering the inside via the entrance surface, and the reflection surface has six or more axes of symmetry. Furthermore, the optical element satisfies a conditional expression; 0.3<a/b<1.4, wherein (a) presents the maximum length of the exit surface in a direction perpendicular to the axis of symmetry and (b) presents a surface gap on the axis of symmetry between the entrance surface and the exit surface. <P>COPYRIGHT: (C)2007,JPO&INPIT |
