PURPOSE: To carrying out working to a target shape before a glass body and to perform mass-production with high precision by charging a sol solution in a mold which has a convex part corresponding to a lens curved surface and drying it, and thus forming a gel body having the concave part.
CONSTITUTION: The sol solution 8 in which alkyl silicate, metal alkoxide, etc., as glass raw materials are prepared is charged in the space 7 of the mold 6 consisting of a bottom mold 6A and a top mold 6 having the convex part similar to the geodesic lens curved surface and then dried as specified to form the plane gel body 12 which has the lens concave part. Then the gel body 12 is baked into the glass body and an optical waveguide 4 whose refractive index is higher at constant depth the surface than at any other part is formed by an ion exchanging method. Consequently, the body is worked in the target shape before the glass body is obtained, so lenses are mass-produced with high precision at low cost.
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