| 摘要 |
PURPOSE:To improve axial aberration while holding end faces flat by forming a specific refractive index distribution over the entire length of a transparent cylindrical body having both end faces which are formed as parallel planes. CONSTITUTION:A refractive index distribution n(r) wherein the refractive index is largest on a central axis 4 within the section perpendicular to the axis 4 and decreases gradually in a radial direction toward the outside circumference is formed in the central lens part 5 entering the inside by a specified distance (l) or above from both end faces 2, 3 of a transparent glass or synthetic resin cylindrical body 1 having both end faces 2, 3 which are formed as the parallel planes perpendicular to the axis (optical axis) 4. A refractive index distribution wherein the refractive index on the axis 4 is largest and decreases gradually in a radial direction toward the outside circumferential surface within the section perpendicular to the axis 4 is applied in both end parts 6, 7 from the faces 2, 3 inward up to the distance (l); at the same time, a refractive index gradient wherein the refractive index at the end faces 2, 3 is smallest and increases gradually toward the inside is applied in the direction parallel with the axis 4 as well in conjunction with said distribution. |
