| 摘要 |
PURPOSE:To miniaturize the above LED array by a method wherein a condenser lens is made of transparent resin in aspheric shape by injection molding method. CONSTITUTION:Both of incidence side surface 14 and emission side surface 15 of a condenser lens 15 are aspherical, and the radius of curvature is bigger on the incidence side surface 14 than the emission side surface 15. The emission side surface of this condenser lens 13 is formed in such that the lens surfaces 16 and 16 on both ends in the longitudinal direction are smaller in radius of curvature than the lens surface 17 at the center. As the radius of curvature is bigger on the incidence side surface 14 than that on the emission side surface 15, the total reflection on the incidence side surface 14 can be prevented, not only making the condensing efficiency for the light emitted from an LED chip 12 increased, but also making the focal distance to a copy on the emission side shortened. As the radius of curvature on the lens surfaces 16 and 16 on both the ends in the longitudinal direction is smaller than that on the lens surface 17 at the center, the opposite side ends of a linear light applied to the copy are brought close each other, making compensation for the decline of illuminance in this part possible. Therefore, the condenser lens 13 can be made compact and thin without sacrificing condensing efficiency of the lens. |
