I guess the main confusion of defining this lens is probably the setting of depth/frequency. j{)~Q D ?
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The main fresnel lens types are: ENq"mwV|
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* Constant groove depth. LJWTSf"f?
* Contant groove pitch types. g2=}G <*0
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So if your depth is fixed you will define +ve value in the cell and to specify the "height" or "depth" of each groove feature. If the frequency of the groove is fixed then you use -ve value. Say putting down - 5 this implies that there are 5 grooves with a unit length. q!&B6]
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Hope this helps!!
