| 摘要 |
PURPOSE:To prevent degradation of the precision of a lens surface due to unbalance of a rlease force by providing a collar part in the outside peripheral part of the lens surface and pushing up this collar part uniformly to improve the release property of the lens surface. CONSTITUTION:The radius, the maximum thickness, the minimum thickness, and the average thickness of the lens are denoted as R, Hmax, Hmin, and HL= (Hmax+Hmin)/2 respectively; and if a lens shape ratio L=R<4>HL<3> defined by these values exceeds 500, the collar part having a thickness HK is provided in the outside peripheral part of the lens. The quantity of deformation of the lens surface due to the release force of the plastic lens is within an allowable range of practical optical capacities if the value of the lens shape ratio L is <=500 as shown by the figure; but the quantity is displacement exceeds said range if the value of L is >500, and therefore, the collar part is provided to hold down the quantity of deformation. |
