Double-sided lenslet array in an imaging multibeam integrator configuration for a diffuser application

Abstract

There are numerous laser applications that require the laser irradiance to possess a controlled shape and uniformity across a specific area at some distance from the source. Such applications include material processing (cutting, welding, drilling, heat-treating), scribing, marking, and microfabrication. One method of achieving this goal is to employ a double-sided micro lens array (MLA) in an imaging multi-aperture beam integrator configuration as discussed by Brown, Dickey, and Weichman. Such a configuration consists of two elements-the-double-sided MLA and a focusing lens. The micro lens array serves to segment the incoming beam at each subaperture into multiple beams, which are then overlapped at the image plane by the focusing lens. The resultant image will have the same shape as the subapertures of the micro lens array, which means that almost any shape can be generated. Lenslet subapertures having square, rectangular, or hexagonal shapes that can be stacked with 100% fill factor are typically used in order to reduce the amount of energy lost at the image plane. The operation of microlens arrays as diffusers are examined in the following paper from a ray optics and a physical optics point of view. Modeling examples/techniques are discussed for both approaches as well.