This text file begins with some data about the size of the window and the number of points in the X axis (NX) and the number in Y (NY). The optical data follows one mesh point at a time as
Z1 complex number z data point with coordinates (xmin, ymin)
Z2 complex number z data point with coordinates (xmin+dx, ymin)
Z3 complex number z data point with coordinates (xmin+2dx, ymin)
ZNX complex number z data point with coordinates (xmax, ymin)
ZNX+1 complex number z data point with coordinates (xmin, ymin+dy)
… …
ZN last complex number z data point with coordinates (xmax, ymax),
N=NXxNY