PURPOSE: To manufacture easily a lens metallic die for forming a lens having concave and convex surfaces, and also to mass-produce it by manufacturing a lens metallic die obtained by forming a lot of concave spherical surface whose dimensions are uniform, in a cavity, without requiring a grinding finish working.
CONSTITUTION: A lot of recessed parts 12a are formed on a cavity surface 11 of a metallic die member 1a by a suitable method. Subsequently, steel balls 2 whose shape and dimensions are uniform and whose hardness is larger than that of the metallic die member 1a are put into each recessed part 12a. In this state, the steel balls 2 are pressed by a pressure machine 3 having a plane-like pressing surface, a lens metallic die 1 having semi-spherical concave spherical surfaces 12 whose dimensions and shape are uniform is obtained on the cavity surface 11. Also, concave spherical surfaces 12b are formed on a master member 1b of the metallic die in the same way as the foregoing, also the concave spherical surface formed part is quenched and hardened, and a master die 1b is obtained. Subsequently, the steel balls 2 are put into the recessed spherical surfaces 12b of the master die 1b, the steel balls 2 are transferred to the cavity surface 11 by pressing the cavity surface 11 of the metallic die member 1a against these steel balls 2, and the lens metallic die 1 is obtained.
MIZUTANI MASAYOSHI
SHIMIZU TAKAE
FUJIMOTO TOORU
