Sorry, my PC cannot type chinese now, crazy. P.^*K:5@
^0I"
I saw some Japanese engineers use "primary differential and second differential" to define the extended freeform optical surface tolerance. 7MKZ*f@x;
I guess it define some vatied range for each coefficients but I don't know Japanese words. _tQM<~Y]u\
Still cannot know how to do that.