I guess the main confusion of defining this lens is probably the setting of depth/frequency. Zuwd(q
I9B B<~4o The main fresnel lens types are: vw3%u+Z& )07M8o!^l * Constant groove depth. df}B:?Ew. * Contant groove pitch types. -0lpsF uPb9j;Q? 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. ;9d(GP}eE %$Mvq&ZZ Hope this helps!!