| 摘要 |
PURPOSE:To form a large-sized preform at a low cost without being limited in the kind of glass by applying fire polishing to glass in the temperature range of flow point and deformation point and forming the preform for a molded lens of a sphere or an ellipse. CONSTITUTION:Glass 8 (roughness is about 400Angstrom ) which has been cut into dice or a sphere and ground is put on traylike mount plate 6 not fused together with glass 8 and heated at a temperature between deformation point and flow point of glass 8 for >=10 minutes. Thereby, glass 8 is applied to fire polishing. Evennesses on the surface of glass 8 are reduced by fluidization of glass through heating and surface roughness is regulated to <=100Angstrom . Weight is previously regulated to <=0.5% in the case of cutting or coarse grinding. Further heating temperature is necessarily set up at the temperature between deformation point and flow point of glass 8 and desirably at a temperature close to softening point. Glass 8 is fluidized at <=10<5> poise and it is difficult that the sphere is held. |
