Process for making microlens arrays and masterforms

A process comprising

• (a) providing a photoreactive composition, said photoreactive composition comprising
• (1) at least one reactive species that is capable of undergoing an acid- or radical-initiated chemical reaction, and
• (2) at least one multiphoton photoinitiator system;
• and
• (b) imagewise exposing at least a portion of said composition to light sufficient to cause simultaneous absorption of at least two photons, thereby inducing at least one acid- or radical-initiated chemical reaction where said composition is exposed to the light, said imagewise exposing being carried out in a pattern that is effective to define at least the surface of a plurality of microlenses, each said microlens having a principal axis and a focal length, and at least one said microlens being aspherical;
• wherein at least a majority of said microlenses have a diameter of less than 1 millimeter, an f number of less than 10, and an average surface roughness of less than half the operating wavelength.