Patent ID: 7329372

Claim:
A method of producing an aspherical lens molding tool by forming a concave aspherical recess of a given depth in a substrate, comprising the steps of: forming a homogeneous layer on a surface of the substrate, said homogeneous layer being higher in etching rate than said substrate; forming a mask on said homogeneous layer, said mask having an opening of a shape; etching through said homogeneous layer to form a pit in said substrate, through said opening of said mask, said pit depth being less than said given depth; removing said mask; and etching said homogeneous layer and said pit in said substrate, said etching performed until said pit is further etched to said given depth to form said concave aspherical recess in said substrate layer, and said homogenous layer is removed from an area of said substrate surrounding said concave aspherical recess.