Research On Laser Beam Shaping Based On Microlens Array

In a lot of laser applications such as material processing, surgery, semiconductor manufacturing, laser fusion and holography, the property non-uniform intensity distribution of the laser beam limits its application. So we must transform the Gaussian beam to the flat-top beam has uniform intensity distribution. At present Chinese researchers mostly use aspheric lens group, the diffraction optical elements or spatial modular to obtain beam homogenizers. There is little one use microlens array (MLA) as the key element of homogenizers. Microlens array homogenizer has advantages of simple structure, low manufacture cost and no sensitive to changes in the incoming beam. Hence that I study on the homogenizer based on microlens array has great significant and application value.This paper mainly study the two structure of homogenizers based on microlens array, which are called diffracting one and imaging another. At first, I derived the mathematical expression of two structure homogenizer’s intensity distribution of target surface based on the theory of scalar diffraction. According to the geometrical optical formula, we obtained the relationship of beam size of target surface to system parameter. And then to simulate the effect of Fresnel number on homogenized spot by MATLAB software on the basis of diffraction effect. After that, we got equivalent models of two structure microlens array homogenizer by used operator optical method. Finally, we analyzed interference effect on last surface when use collimated laser as source, for high coherent laser high contrast point arrays inevitably appear on homogenization.We calculated the measured results and compared with the theoretical results derived form the formula after building diffracting and imaging microlens array homogenizers test system. Results proved that the microlens array homogenizers model built in paper are correct and effective. We illustrated that using microlens array as the main components of a laser beam homogenizer is feasibility and efficiency.