Sorry, my PC cannot type chinese now, crazy. N)F&c!anh
JnC$}amr
I saw some Japanese engineers use "primary differential and second differential" to define the extended freeform optical surface tolerance. r>!$eqX_
I guess it define some vatied range for each coefficients but I don't know Japanese words. 1iS]n;xcl/
Still cannot know how to do that.