Patent ID: 6974517

Claim:
A method for providing a hermetic seal between a window and a frame of an apparatus, comprising the steps of: providing a window which is transmissive to radiation having a predetermined wavelength; providing a frame which has an opening therethrough; providing an annular sealing section between and in contact with each of said window and said frame, said sealing section extending completely around said opening; heating said window, said frame and said sealing section to a selected temperature at which said sealing section has melted, said selected temperature being lower than melting temperatures of said frame and said window; and thereafter cooling said window, said frame and said sealing section until said sealing section has solidified and formed between said window and said frame a hermetic seal which extends completely around said opening; selecting for use in said sealing section a first glass material and a second glass material made from a material different from a material of the first glass material, said first glass material being an annular portion of said sealing section which extends around said opening of said frame in contact with said window and spaced from said frame, said second glass material being an annular portion of said sealing section which extends around said opening of said frame in contact with said frame and spaced from said window, and said first and second glass materials being in contact with each other between said window and frame; selecting for use in said sealing section a third glass material made from a material different from each of said first and second glass materials, and which is an annular portion of said sealing section that extends around said opening of said frame in contact with each of said frame and said window, said third glass material being disposed on a side of said first and second glass materials nearest said opening in said frame.