| 摘要 |
PURPOSE:To continuously change the refractive index of a glass rod having a specified composition from the central axis to the periphery by immersing the rod in a molten ion exchange medium to ion-exchange specified components in the glass for a component in the medium and by heat treating the rod. CONSTITUTION:Glass contg., by mole, 57-63% SiO2, 17-23% B2O3, 5-17% Na2O and 3-15% Tl2O as principal components or further contg. ZnO, As2O3, Sb2O3, etc. is melted to form a glass rod. This glass rod is immersed in a molten salt bath of an ion exchange medium such as KNO3 to exchange Tl and Na ions in the rod for K ions, and by keeping the rod at the glass transition temp. in air or an oil bath causing practically no ion exchange for >=20hr, the remaining Tl ions and the peripheral K ions are moved toward the periphery of the rod and the interior, respectively to continuously increase the refractive index of the peripheral part of the rod from the central part. The rod is then cut and finished by polishing. Thus, a refractive index distribution type lens is manufactured. |
