Method for heat treating synthetic quartz glass for optical use, heat treatment apparatus for the same, and synthetic quartz glass for optical use

Abstract

An object of the present invention is to overcome the problems of the prior art technique, and to provide a heat treatment method as well as a heat treatment apparatus capable of heat treating, with higher efficiency, a synthetic quartz glass for optical use having higher homogeneity and higher purity. Another object of the present invention is to provide and a synthetic quartz glass for optical use. The problems above are solved by, in a method for heat treating a flat cylindrical synthetic quartz glass body provided as the object to be heat treated in a heating furnace, a method for heat treating a synthetic quartz glass for optical use comprising preparing a vessel made of quartz glass and having a flat cylindrical space for setting therein the object synthetic quartz glass body, placing two or more object synthetic quartz glass bodies into the vessel in parallel with each other, filling the space with SiO2 powder, setting the vessel inside the heating furnace with its lid closed, and applying the heat treatment to the vessel.

Dependencies are inferred from the claim text.