| 摘要 |
PROBLEM TO BE SOLVED: To provide a concave lens and an illumination device using the same with small energy consumption such as an LED and capable of having a display section of a great area irradiated at almost uniform distribution of illuminance over a wide range by effectively using light energy with high directivity.SOLUTION: The concave lens is characterized by having numerous triangular shaped protrusions 16a, 16b, 16c, 16d... with the same height h as a section in the radial direction going through the center formed in the radial direction on one surface of a transparent substrate 14 transmitting light. |
