| 摘要 |
<p>To provide a method for preparing a highly homogeneous silica glass formed article for optical use, a high purity massive formed article of synthetic silica glass having end faces at both sides thereof, a side face positioned between the end faces, at least a part of which is externally projected beyond the outlines of the end faces and an optical homogeneity in the direction perpendicular to the line connecting the end faces lower than that of the article observed in the direction along the line connecting the end faces is used as an intermediate. A highly homogeneous formed article of synthetic silica glass for optical use which is homogeneous and free of cord in the foregoing three directions is produced by fitting support members to opposite portions on the side face of the foregoing intermediate, i.e., the high purity massive formed article of synthetic silica glass; heating the massive formed article which is rotated through the rotation of the support members to form a molten zone in the massive formed article; drawing the molten zone of the massive formed article by outwardly pulling at least one of the support members towards the direction along the rotation axis thereof to form a rod-like synthetic silica glass; heating the rod-like synthetic silica glass thus formed while rotating the silica glass by rotating the support members to partially form a molten zone in the rod-like silica glass; applying an external force to the molten zone through the support members to form a boundary area within the molten zone; moving the boundary area of the molten zone along the rotation axis of the rod-like silica glass to form a highly homogeneous rod-like formed article of synthetic silica glass which is homogeneous in the three directions perpendicular to one another; molding, with heating, the highly homogeneous rod-like formed article of synthetic silica glass for optical use thus produced in a mold; and then heating and gradually cooling the resulting molded article.</p> |
