Theoretical Analysis And Experimental Research Of Microlens Array Homogenizer

The flat-top laser beam with uniform intensity distribution characteristics has become an essential source in many fields, including laser cladding, solar cell scribing, the semiconductor substrate annealing and laser lighting. Therefore, it has important application value to shape Gaussian beam to flat-top beam. Generalized laser beam homogenization techniques commonly use aspheric lenses, polygonal rods, diffractive optical element and microlens array. With the advantage of strong beam adaptability and high transmittance, the microlens array is used widely.This paper mainly analysis the homogenized characteristics of the microlens array from the perspective of ray-tracing theory and Fourier optics theory. The analysis model of raytracing and field-tracing are built, and the corresponding experiments are carried out. The main research work are as follow:(1) Based on the ray-tracing theory, the ray-tracing model of analysis homogenized characteristics of microlens array system is built, which can link the relationship between the intensity distribution of beams and the position distribution of rays. The model can analyze the uniformity of intensity distribution, while the original model cannot. The intensity distribution change of arbitrary incident beam through the system can be calculated precisely. And the analytical results show that the homogenized characteristics has close relationship with oblique incident angle, observation distance, the number of microlens, and the aberration of focal lens.(2) Based on the Fourier optics theory, the field-tracing model of analysis homogenized characteristics of microlens array system is built. By deducing the analysis formula of the focal spot, the reason of beam shaping is indicated clearly, which is determined by the diffraction of single micro-lens and the multiple-beam interference. At the same time, the influence of the amplitude and the phase of incident beam is discussed, which reveal the essence of the microlens array homogenization system for arbitrary incident beam.(3) Based on the theoretical basis of Fourier optics analysis model, the design method of diffraction-type microlens array is given, which can get the arbitrary intensity spatial distribution. By using G-S iterative algorithm for calculating the phase diffractive microlens element distribution function, then making the function be arrayed. And the design solution of such elements is given.(4) For versatility microlens array, the experimental platform is built to do the beam shaping experiment. The homogenized characteristics of the incident beam expander size, the distribution of incident beam, the observation distance, are verified respectively. Thus, it verifies that the ray-tracing model and the field-tracing model are suitable for microlens array system.