Allow me to repost here for depth/frequency setting NlXHOUw)u
The main fresnel lens types are: 8`XpcK-0
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* Constant groove depth. P9;
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* Contant groove pitch types. -1d2Qed
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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. /*!K4)$-*2
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For radius, this is the curvature of the base surface. If you define one such lens and chaneg the radius and you shall see what it means. A graphic tells lounder than words. %$|=_K)Ks
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For conic: check conic section using Wikipedia and you should see what conic constant means. Q!(16
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