Method for manufacturing a gradient index optical element

Abstract

In accordance with the present invention, the dopant within one gradient index optical element has two independent concentration distributions. Particularly to use the present invention to obtain a gradient index optical element having an excellent chromatic aberration correction ability, it is only needed to make such dopant distributions as shown in the previously stated Japanese Patent Application No. 280897/1989. However, as to the doping of a dopant into a porous body, there is a limit in the amount which can be doped. This is a disadvantage of the molecular stuffing method, but the reason for this is that the dopant must be supplied into the holes as a solution and it is largely restricted by the solubility of the dopant in the solvent. In addition, since the intra-hole fixing of the dopant depends on the solubility difference by temperature or that by solvent exchange, it is further restricted. For this, the latter process which is an application of the molecular stuffing method preferably takes the distribution that has less doping amount. Accordingly, a large concentration distribution must be provided to the dopant in the preceding process. For that, the preceding process is desirably a gel which has sufficiently large concentration gradient by the sol-gel method. However, the sol-gel method also has a defect, in which the distribution provision relies on the elution of the dopant metal, and thus a convex distribution is easier to produce in principle. In view of the foregoing, it is the most effective that the concentration gradient of the first dopant is formed in a convex shape by the sol-gel method using alcoxide as the raw material for retreiving the first dopant, and that the concentration gradient of the second dopant is formed in a concave shape by an application of the molecular stuffing method.

Dependencies are inferred from the claim text.