Method of manufacturing optical glass element, and optical glass element manufactured using the method

Abstract

There are provided a method of manufacturing an optical glass element, for which flatness and smoothness of the surfaces of the optical glass element can be improved while securing the similarity of the cross-sectional shape of the optical glass element to that of the mother glass, and for which continuous production involving few steps can be carried out, and an optical glass element manufactured using the method. A mother glass is prepared, which has a cross-sectional shape substantially similar to a desired cross-sectional shape of the optical glass element, and the mother glass is drawn while heating to a predetermined temperature such that the mother glass has a viscosity of 10 5 to 10 9 poise.

What is claimed is:  
     
         1 . A method of manufacturing an optical glass element, comprising the steps of: 
 preparing a mother glass having a cross-sectional shape substantially similar to a desired cross-sectional shape of said optical glass element; and    drawing said mother glass while heating to a predetermined temperature such that said mother glass has a viscosity of 10 5  to 10 9  poise.    
     
     
         2 . A method of manufacturing an optical glass element as claimed in  claim 1 , wherein said mother glass is drawn while heating to a predetermined temperature such that said mother glass has a viscosity of 10 8  to 10 9  poise.  
     
     
         3 . A method of manufacturing an optical glass element as claimed in  claim 1 , wherein said optical glass element is made of BK7, and said predetermined temperature is 660 to 860° C.  
     
     
         4 . A method of manufacturing an optical glass element as claimed in  claim 1 , wherein said optical glass element is made of BK7, and said predetermined temperature is 660 to 690° C.  
     
     
         5 . A method of manufacturing an optical glass element as claimed in  claim 1 , wherein said mother glass has a cross-sectional area 5 to 150 times that of the optical glass element to be obtained.  
     
     
         6 . A method of manufacturing an optical glass element as claimed in  claim 5 , wherein the cross-sectional area of said mother glass is 10 to 100 times that of said optical glass element to be obtained.  
     
     
         7 . A method of manufacturing an optical glass element as claimed in  claim 1 , wherein said desired cross-sectional shape is polygonal.  
     
     
         8 . A method of manufacturing an optical glass element as claimed in  claim 7 , wherein said optical glass element comprises a prism.  
     
     
         9 . A method of manufacturing an optical glass element as claimed in  claim 1 , wherein said desired cross-sectional shape is circular.  
     
     
         10 . A method of manufacturing an optical glass element as claimed in  claim 1 , wherein said mother glass is drawn by introducing a lower end part thereof into a heating furnace at a feed speed V 0  and pulling said lower end part heated to said predetermined temperature downwards at a drawing speed V 1 , and wherein said drawing speed V 1  are set relative to said feed speed V 0  so as to obtain a drawing speed ratio V 1 /V 0  of 25 to 22,500.  
     
     
         11 . A method of manufacturing an optical glass element as claimed in  claim 10 , wherein said drawing speed ratio V 1 /V 0  of said drawing speed V 1  to said feed speed V 0  is in a range of 100 to 10,000.  
     
     
         12 . A method of manufacturing an optical glass element as claimed in  claim 1 , wherein said mother glass is made of a glass selected from the group consisting of BK7, Ultran, FK, PK, PSK, BaLK, ZK, BaK, SK, KF, BaLF, SSK, LaK, LLF, BaF, LF, F, BaSF, LaF, LaSF, SF, TiF, KZF and KZFS.  
     
     
         13 . An optical glass element manufactured by a method of manufacturing an optical glass element comprising the steps of: 
 preparing a mother glass having a cross-sectional shape substantially similar to a desired cross-sectional shape of said optical glass element; and    drawing said mother glass while heating to a predetermined temperature such that said mother glass has a viscosity of 10 5  to 10 9  poise.