Reforming manner of synthetic quartz glass optical body for ultraviolet light and synthetic quartz glass optical body null for ultraviolet light

摘要

PURPOSE: To provide a synthetic quartz glass optical article improved in optical homogeneity and transmittance, prevented from the generation of structural defects, and improved in the transmittance to a level enabling to use for precision optical equipment. ;CONSTITUTION: Highly pure synthetic quartz glass free from strain and stria and having a refractive index homogeneity of ≤1×10^-6 is stationarily placed in an oven, subjected to the closure of the oven, to the evacuation of the oven with a vacuum pump, and to the charging of e.g. the 1000:1 ratio mixture of N2 gas with O₂ gas into the oven, thermally treated in an atmosphere comprising an atmospheric pressure of ≤5kgG (e.g. 1atm), a temperature-rising condition of approximately 200C°/hr up to a temperature of ≥200°C (e.g. 1400°C) and a logarithmic oxygen fractional pressure (log PO₂) of -0.4 to -0.5 for approximately 60hrs, cooled to 500°C at a temperature-lowering rate of approximately 10°C/hr, and subsequently gradually cooled to room temperature to provide the optical article eliminated in the absorption of light in a vacuum UV light region of 170-200nm, having a 10mm inner part transmittance of ≥99.9% for light having a wavelength of 93nm, and not deteriorated in other optical properties (strain, stria, homogeneity).;COPYRIGHT: (C)1995,JPO