Exposure controlled projection lithography for microlens fabrication

An Exposure Controlled Projection Lithography (ECPL) process with the ability to fabricate microlenses on transparent substrates is presented. This process (also referred to as maskless lithography) can be used to create polymer microlenses on flat or curved substrates without involving hard tooling. Incident radiation, patterned by a dynamic mask, passes through a transparent substrate to cure photopolymer resin that grows progressively from the substrate surface. A process planning algorithm which incorporates the effects of optical aberrations present in the ECPL system and photopolymer's response to irradiation is presented. An interferometric process monitoring system is also presented which can be used to control the process in real time. Samples of micro optical elements fabricated on flat and non-planar substrates using the ECPL system are also presented, which demonstrate the wide range of fabrication capability of our ECPL process.