Adjusting light distribution for generating microlens arrays with a controllable profile and fill factor

This paper presents a simple but effective process to fabricate high quality aspheric microlens arrays (MLA) and bifocal microlens arrays (BMLA) by predicting and adjusting the UV light distribution. The profile-controllable BMLA has two different focal lengths simultaneous along the optical axis, measured at f(1) = 26 +/- 1 mu m (the top lens) and f(2) = 35 +/- 1 mu m (the base lens), respectively. The fill-factor and curvature of the obtained profiles have been well optimized by controlling the air gap and exposure time, for instance, the fill factor is topped up to 99.7% from an initial 25.8% (the corresponding aperture diameter is enlarged to 15 mu m from an initial 10 mu m) and the micro lens height ranges from 2.66 mu m to 9.03 mu m. Optical tests indicate that MLAs and BMLAs have a uniform shape and a good consistency of the focal length. By adjusting the light distribution, this proposed strategy possesses the ability and flexibility to fabricate profile-controllable MLAs and BMLAs.