| wt-sowboon | 2011-06-18 21:04 |
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One of the main reason of not getting homogenous illumination is due to CROSSTALK! which is the over-filling of rays from adjacent lens in the arrray. To overcome this kind of problem, a properly written merit function or ZPL is needed if u wanna run the optimization automatically by setting all the array's radius, lens separation, thickness, fourier lens radius as varaibles. This is definitely not an easy task and most probably will get into a mess. For me I break the design into a few parts. By understanding the function of the components (microlens and the fourier lens) is important. Microlens is used to break the beam into many bundle of beamlets. Each microlens in the array is identical. In fact, the configuration of two microlens arrays is just like designing a collimating system just that now the input beam is smaller. the separation of arrays must less than 2 times of the total FL of the lens pitch to avoid crosstalk. Normally i just use slightly bigger than 1FL. Then the fourier lens is just like a normal focusing lens, it also determine the size of the flat-top dimension at image plane. The operand i used is POPD (data 30-32). This way of design is faster and easier, so i no need to bother to write a complicated MF or ZPL. A piece of advice is look for off-the-shelf microlens array is always the cheapest and faster solution than making a new mask for array. New mask accuracy and tolerance is sometimes hard to guarantee the performance. http://www.suss-microoptics.com/downloads/SMO_TechInfo_Sheet_10.pdf http://www.suss-microoptics.com/downloads/SMO_TechInfo_Sheet_10_Examples.pdf Refer the their technical documentation and sample design file in zemax. You will find that the excel file is a handy calculator for this design. wish this help! 
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Gotta re-type all overagain. 