| 摘要 |
PURPOSE:To obtain a glass article having effective refractive index distribution and useful for light-transmission, etc., by heating a specific deposited article in an atmosphere containing a fluorine compound while varying the partial pressure of the fluorine compound, thereby controlling the distribution of fluorine concentration in the article. CONSTITUTION:A deposited article of glass soot 25 having columnar or cylindrical shape is placed in a muffle 22 made of a high-purity carbon and the muffle is put into an annealing furnace, etc. The article is heated with a heater 24 in an atmosphere containing a fluorine compound (e.g. SiF4) setting the partial SiF4 pressure to <=100 Pa at the start of the heat-treatment and to >=100 Pa at the completion of the conversion of the glass soot to transparent glass while varying the partial SiF4 pressure according to the increase of the temperature of the muffle 22 and the contraction of the deposited article 25. Therefore, the radial distribution of the fluorine concentration is controlled so as to decrease the concentration at the core and gradually increase toward the outer circumference. The objective columnar or cylindrical glass article can be produced by this process. |
