| 摘要 |
PURPOSE:To obtain an optical element without forming a crack, etc., by forming a surplus portion not used for the optical element to concentrate a stress into the surplus portion, in a press forming of a heated glass raw material. CONSTITUTION:In surfaces of a dies 21a and 22a of the upper die 21 and the lower die 22 respectively in the die 20, effective diameter forming parts 21aE and 22aE, and flange forming parts 21aF and 22aF together with surplus forming parts 21aB and 21aB located at the outside of the flange forming parts 21aF and 22aF, are continuously constructed, and protrusions 25 comprising stress concentrating parts are formed in the surplus forming parts 21aB and 22aB. With the above construction, a surplus area 24c is formed in addition to a effective diameter are 24a and a flange area 24b in a lens forming body 24 formed by the die 20, and in the surplus area 24c concave parts 26 with a shape corresponding to the protrusions 25 are formed. In a cooling process after the forming, a residual stress concentrates most at the concave parts 26 in the surplus area 24c, which have larger shape change than that of a shape changing portion from effective are 24a to the flange area 24b. The surplus area 24c is cut off to produce a lens 30. |
