| 摘要 |
PURPOSE:To improve characteristics (convergence, focal length, aberration, etc.) of a manufactured Fresnel lens by forming Fresnel lens zone patterns so that front and rear patterns are inverted alternately. CONSTITUTION:The lens 6 consists of plural zones 61 which decrease in width outward about an optical axis N. THe pattern of a center zone m0 is in the shape and direction with the zone pattern of the center zone 31 of the lens 3, and the pattern in a 1st zone m1 outside it is in the front-rear inverted direction as compared with the pattern of the zone of the lens 3 at the same position; and the pattern of a 2nd zone m2 is in the forward direction and the pattern in a 3rd zone m3 is in the opposite direction. Thus, the respective zones 61 of the Fresnel lens 6 are arranged repeatedly in alternately forward and backward directions to obtain an ideal pattern. |
