A question about SampleMTF in opliand docs : what's the meaning of fx >0 and fy >0

[wuxujiong]

I want a help about explaining the meaning of fx and fy , when calculating the sampleMTF of a lens , does it mean fx >0 and fy=0 for sagittal and fx=0, fy>0 for tangential, am I right? but what's the mtf meaning of fx > 0 and fy >0 for a field like in the picture?

more import , the speed of calculating MTF of Sampled MTF is quicker than the macro (MTF_1fld()) in codev ?

[HarrisonKramer]

does it mean fx >0 and fy=0 for sagittal and fx=0, fy>0 for tangential

yes, this is generally correct. The tangential plane is the plane formed by the optical axis and the chief ray, so for a field in +Y (the usual assumption), you are correct.

fx and fy refer to the spatial frequency in x and y, respectively, in units of cycles/mm. If both fx and fy are non-zero, it is equivalent to asking about the resolution of a tilted feature, e.g., when fx=fy, you'd have a 45 degree tilt.

I cannot speak on the speed on CodeV and how it compares to Optiland. However, the Optiland implementation is performant because of the algorithm used, which runs a raytrace only once during initialization, then caches the result. It uses fast, vectorized numpy operations to compute the MTF as the chosen frequencies. Check the actual implementation in the code to see specifically what it is doing and what assumptions are made, if you like.