本发明涉及一种用于通过玻璃化制造合成石英玻璃的光学预型件，并形成多孔的纵向轴线（L），其具有筒状的SiO 2烟灰体（1）在一个融合模具（23）与底板（24），其具有加热区（21 ），包括以下步骤：（a）玻璃化SiO 2的烟灰体（1）在加热区（21）（在玻璃窗温度以形成一个完全釉面，透明石英玻璃体（6），然后（b）形成该玻璃化的石英玻璃体6） 通过在软化温度软化熔融成型（23）以形成粘性石英玻璃料块（7），其完全或部分地填充所述熔融模塑（23）的容积，以及（c）冷却所述石英玻璃料块（7）并除去从融合模具（23 ）以形成光学预制件。 为了获得质量可重现好，高纯度，均匀的，旋转对称的特性分布的全合成石英玻璃的圆柱形毛坯，本发明提出的是，根据方法步骤玻璃化过程中（a）是实心圆柱形石英玻璃体（6）形成，并且在熔体形式形成期间 根据由控制供给固体圆柱形石英玻璃体（6）的处理步骤（b）与底板（24）的定心（23）接触。

The invention relates to a method for manufacturing an optical preform of synthetic quartz glass by vitrification and forming a porous, a longitudinal axis (L) having cylindrical SiO ₂ soot body (1) in a a fusion mold (23) with base plate (24) having heating zone (21 ), comprising the following steps:
(A) vitrifying the SiO 2 soot body (1) in the heating zone (21) at a glazing temperature to form a completely glazed, transparent silica glass body (6), and then
(B) forming the vitrified quartz glass body (6) by softening the melt-molding (23) at a softening temperature to form a viscous quartz glass mass (7) which fills the volume of the melt molding (23) fully or partially, and
(C) cooling the quartz glass mass (7) and removal from the fusion mold (23) to form the optical preform.
In order to obtain with reproducibly good quality, high purity and homogeneous, rotationally symmetrical property profiles fully cylindrical blanks of synthetic quartz glass, the invention proposes that during vitrification according to method step (a) is a solid cylindrical quartz glass body (6) is formed, and that during the forming in the melt form (23) according to process step (b) of the solid cylindrical quartz glass body (6) by controlled feeding with a centering of the bottom plate (24) is brought into contact.