Exposure mask for fabricating microlenses

An exposure mask constructed to produce in a photoresist material a replica of a microlens having a single valued asymmetric surface, using a single exposure mask, said exposure mask comprising,

• a layer of mask material which blocks transmission of light through the material,
• a plurality of precisely located and sized light transmitting openings in the mask material and formed with sufficiently small specific opening sizes and located at a sufficiently large number of specific locations, correlated to related locations on the single valued asymmetric surface of the microlens to be produced in a photoresist material so that, after exposure of the photoresist material to light transmitted through the openings and after processing the exposed photoresist material, photoresist material replica having the single valued asymmetric surface can be obtained and wherein the light transmitting openings are located to produce a step function discontinuity in the surface of the microlens photoresist material replica.