PURPOSE: To anneal a lense without lowering lense quality and to reduce its forming cycle remarkably, by following process in which a plastic lense made by injection molding is precooled for short time in the forming metal-mold, and then is slowly cooled by dipping into warm water at the outside of the mold.
CONSTITUTION: For instance, an injection molded lense 1 at 230°C of resin temperature is left in the forming mold of 0W80°C and precooled for 3W5min. Consequently, the solidified layer 2 of the lense is formed. next, the lense, taken out from the metal mold is slowly cooled by warm water (preferably above 70°C) at the outside of the mold, thereby solidifying the lense 1. Further, in the case of cooling a thick lense with large diameter, a pair of plastic holding members 5 connected by fin like hinge 4 and composed of a portion covering periphery, cover the periphery portion 6 of the lense by folding it. Then the lense 1 is desirable to be dipped into the warm water.
INOUE HAJIME
TAKAGI MASAO
