Glass body with distribution composition

Abstract

The present invention provides a glass body with distributed composition which contains, for example, a rare-earth element having a concentration distribution, which can be produced in high yield while inhibiting cracking at the time of vitrification and which has optical properties advantageous in correcting chromatic aberration in image pickup systems. For example, in a four-component glass composed of SiO.sub.2, Al.sub.2 O.sub.3, Y.sub.2 O.sub.3 and ZrO.sub.2 in which Y.sub.2 O.sub.3 has a recessed parabolic concentration distribution profile being high at the periphery of the glass and low at the center of the glass and in which each of ZrO.sub.2 and Al.sub.2 O.sub.3 has a protrudent parabolic concentration distribution profile lowering from the center of the glass toward the periphery of the glass, there is the relationship: (.DELTA.C.sub.Al /.DELTA.C.sub.Ml)/C.sub.Si =0.0334 wherein .DELTA.C.sub.Ml is a concentration distribution difference of Y.sub.2 O.sub.3, .DELTA.C.sub.Al a concentration distribution difference of Al.sub.2 O.sub.3 and C.sub.Si a constant concentration of SiO.sub.2. This glass can be obtained in high yield.

Dependencies are inferred from the claim text.