| 摘要 |
PURPOSE:To prevent the occurrence of a shrink mark, etc., in addition to distortion caused by internal stress produced due to a difference in cooling speed in such a lens by providing a lens thickness correcting section where the thickness of the lens in the direction perpendicular to the length direction and optical axis of the lens is gradually reduced toward the central part of the lens from both end sections of the effective section of the lens in the length direction. CONSTITUTION:In a long-size molded lens 1 formed to have a long size in one direction (x) perpendicular to the optical axis (r) of the lens, a correcting section where the thickness of the lens in the direction perpendicular to the optical axis (r) and length direction (x) is gradually reduced toward the central part of the lens from both end sections of the effective section 2 of the lens in the length direction (x) is provided. Since no much difference exists in volume between the central part and end sections of the lens 1 in the length direction (x), the relation between the volume and surface area can be balanced almost equally at each part of the lens 1 and the cooling speed of the molded body of the lens at the time of molding becomes almost equal at each part. Therefore, occurrence of distortion caused by internal strain due to a difference in cooling speed between each part and remaining of the distortion can be prevented. In addition, the deterioration of shape transferring accuracy, occurrence of shrink marks, etc., at the surface caused by a difference in cooling speed between each section can also be prevented. |
