Patent ID: 7007510

Claim:
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.