| 摘要 |
Method and apparatus for manufacturing glass progressive power lenses. The lenses are manufactured by a vacuum forming technique in which a glass lens is placed upon a forming block, heated to its softening point, and then forced to sag against and assume the shape of the forming block surface by the creation of a vacuum between the lens blank and the block surface. The forming block is provided with a plurality of apertures through which the vacuum is drawn and these apertures are positioned so as to ensure the maintenance of an adequate pressure differential between the two surfaces of the lens blank as it sags in a wave-like manner from its center towards its periphery. This will ensure that the blank will sag evenly and smoothly against the forming block and in general, enables glass progressive lenses to be manufactured by the vacuum forming technique notwithstanding the fact that the shape of such lenses would normally not permit creation of the necessary vacuum force between the forming block and the lens blank to effect proper sagging. |
