| 摘要 |
PURPOSE:To facilitate designing of a lens and to improve the performance of the lens by combining >=2 kinds of glassy materials contg. quartz or fluorine controlled in refractive index on specific wavelengths. CONSTITUTION:The dependency of the refractive index of synthetic quartz on wavelength gives a refractive index curve (a). The refractive index is 1.508 when the wavelength used for the projection lens is determined at KrF excimer light, i.e., 248nm at this time. On the other hand, the refractive index curve with the glassy material incorporated with 4.5% fluorine impurity (impurity- contg. quartz) is (b) and the refractive index at 248nm is 1.47. Namely, the above-mentioned fact reveals that two kinds of the refractive indices, 1.508 and 1.47, can be used even with the glassy material of the same quartz base if the material is used with 248nm light. The production of the desired lens is permitted if the lens is designed by utilizing the glassy materials having the different refractive indices at need.
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