PURPOSE: To absorb tightening force of screws to be dispersed in slotted parts and obtain a high accurate lens, by arranging in the peripheral part of a lens- material a plurality of through holes and slotted parts concentrically with an external shape of the lens and tightening the screw to the through holes so as to fix the lens-material to a fixing jig.
CONSTITUTION: A lens-material 6 of plastic disc provides on a predetermined concentric circle a plurality of through holes 7 at an equal space while between the through hole 7 and the required external diameter of a lens a plurality of slotted parts 9 which absorb strain. Then the lens-material 6 is fixed to a fixing jig 5 for turning by tightening a screw 8 to the through holes 7. While a chuck 2 on a lathe main spindle holds said fixing jig 5. And then a machining tool 4 driven by numerical control forms the lens-material 6 in a predetermined surface shape of the lens. In this way, a desired end can be attained because tightening force of the screw 8 can be dispersedly absorbed by the periphery of the slotted part 9 when the lens-material 6 is tightened to said fixing jig 5 by the screw 8.
INOUE YOSHIO
AOYAMA TAKAO
