Method of producing an optical member
AssigneesHeraeus Quarzglas GmbH & Co. KG, Shin-Etsu Quartz Products Co., Ltd.
InventorsTetsuji Ueda, Akira Fujinoki, Hiroyuki Nishimura, Martin Trommer, Stefan Ochs
Life of this patent
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Abstract
An object of the present invention is to provide an improved blank such that an optical member of a high homogeneity can be obtained therefrom, and to provide a vessel and a heat treatment method for heat-treating a highly uniform synthetic quartz blank. In a first aspect of the invention a special designed blank is provided showing a concave shaped outer surface. In a second aspect of the invention a special designed vessel for heat-treating blanks is provided, whereby the degree of heat emission at the center is set higher than that of the surroundings.
Claims23
A method for producing an optical member of quartz glass, said method comprising:
- providing a blank which includes a contour portion for the contour of the optical member to be produced and an overdimension portion that has a surface which is defined by a lower side, an upper side opposite said lower side and spaced apart therefrom, and an outer edge extending around a center axis, and
- subjecting said blank to a thermal treatment;
- and
- subsequently cooling the blank, wherein measures are provided which, during cooling, keep heat conduction in an area adjacent said outer edge lower than in an area adjacent said center axis;
- removing the overdimension portion so as to expose the optical member;
- and
- wherein the measures comprise use of a preform as said blank wherein said overdimension portion includes a thickened portion which extends from said outer edge towards said center axis, said thickened portion varying in thickness so that the distance between the lower side and the upper side in an area adjacent the outer edge is greater than the distance between the lower side and the upper side in an area of said center axis.
A method for producing an optical member of quartz glass, said method comprising:
- providing a blank comprising a contour portion for the contour of the optical member to be produced and an overdimension portion surrounding the contour portion, said overdimension portion having a center axis, a lower portion, an upper portion opposite said lower portion and spaced apart therefrom, and an outer edge extending around the center axis,
- subjecting said blank to a thermal treatment;
- subsequently cooling the blank;
- and
- removing the overdimension portion so as to expose the optical member;
- said overdimension portion being configured such that, during cooling, heat conduction from the contour portion adjacent said outer edge is limited more than adjacent said center axis;
- and
- wherein at least one of the upper and lower portions of the overdimension portion have different thicknesses adjacent the center axis and adjacent the outer edge, the thickness thereof adjacent the center axis being less than the thickness adjacent the outer edge.
A method for producing an optical member of quartz glass, said method comprising:
- providing a blank which includes a contour portion for the contour of the optical member to be produced and an overdimension portion that has a surface which is defined by a lower side, an upper side opposite said lower side and spaced apart therefrom, and an outer edge extending around a center axis, and
- subjecting said blank to a thermal treatment;
- and
- subsequently cooling the blank, wherein measures are provided which, during cooling, keep heat conduction in an area adjacent said outer edge lower than in an area adjacent said center axis;
- removing the overdimension portion so as to expose the optical member;
- and
- wherein the measures comprise
- introducing said blank into a vessel having a removable upper side and a lower side opposite said upper side and spaced apart therefrom, and an outer edge connecting upper side and lower side and extending around a center axis, said upper side, said lower side and said outer edge defining an interior of the vessel receiving therein said blank, said upper side and said lower side have a higher thermal conduction in an area of said center axis than in an area adjacent said outer edge,
- filling intermediate spaces between said blank and said vessel with SiO2 powder, and
- subjecting said blank surrounded by said SiO2 powder in said vessel to a thermal treatment by introducing said vessel into a furnace and heating and subsequently cooling the vessel.
Dependencies are inferred from the claim text.