Method for making a glass-based soft-edged aperture filters
AssigneeHoya Glass Works, Ltd.
InventorsYoshijuki Asahara, Tetsuro Izumitani
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Abstract
Glass-based soft-edged aperture filters having good thermal stability are produced by diffusing a coloring element such as Ag into a glass, thus providing a transmittance gradient in the colored portion thereof. A glass composition comprising a basic glass, such as a silicate, borosilicate or phosphate glass, and 1 to 10% by weight of As.sub.2 O.sub.3 and/or Sb.sub.2 O.sub.3 is especially suitable for producing such soft-edged aperture filters.
Claims9
A method for producing a soft edged aperture filter to prevent Fresnel diffraction at the edge of a glass rod which comprises diffusing a coloring element into a glass plate which has on a first surface thereof a glass projection portion which does not extend to any side of the glass plate, wherein said diffusion is into the projection and into said first surface and bottom surface of the plate, and subsequently removing said glass projection portion down to said first surface having said diffused coloring element without disturbing said first surface and removing the diffused bottom surface to thereby provide a light transmittance gradient arranged in a circle on the glass plate, the gradient being a lowering of the light transmittance between the first and second surfaces of the glass plate in the radial direction from the inner to the outer portion of the circle.
Dependencies are inferred from the claim text.