Methods of providing diffusing risers on a fresnel lens die having a plurality of optical facets, wherein adjacent optical facets are separated by a riser, the method including the steps of depositing a difflusing layer on the plurality of optical facets and the risers, and selectively removing the diffusing layer from the plurality of optical facets, wherein the diffusing layer remains substantially intact on the risers. The diffusing layer can be deposited in an electrolyte bath substantially free of grain refiners.
A method for the manufacture of a Fresnel lens sheet is disclosed. The Fresnel lens sheet have arranged thereon a multiplicity of sawtooth-like Fresnel lenses composed of a Fresnel lens surface demonstrating a convex lens function and a rise surface located between the adjacent Fresnel lens surfaces. This sheet has a layer containing a light-diffusing material or a light-absorbing material on the rise surfaces. The method comprises the steps of, coating a photoresist on the Fresnel lens surfaces and rise surfaces, and forming the layer containing a light-diffusing material or a light-absorbing material on the rise surfaces by exposing the photoresist at mutually different light exposure doses per unit surface area on the Fresnel lens surfaces and rise surfaces.
