Microlens Arrays Shape LED Beam

LEDs are not well-adapted for applications requiring uniform illumination, unless supplementary optics help to shape the beam. As a possible solution, researchers at Fraunhofer Institute for Applied Optics and Precision Engineering in Jena, Germany, explored refractive beam-shaping systems based on microlens arrays by applying scalar diffraction theory. In an initial setup, described in the October issue of Optical Engineering, the group found that a collimating lens, a single microlens array and a Fourier transform lens could not provide the desired homogeneous intensity distribution. However, the group reported that it minimized diffraction effects and observed a nearly perfect flat-top intensity distribution by incorporating two -- not one -- cylindrical microlens arrays in the optical setup, separated by one focal length of the first array's lenslets.