Hallo alle
Ich möchte Euch schließlich die Aussage über den Astigmatismus infolge Parallaxe der Messanordnung von Bruce Griffiths (Interferometry Group) nicht vorenthalten:
"I rederived it from a more general equation given in Welford's "Aberrations of Optical Systems"
The formula gives the amplitude of the classical field astigmatism wavefront error term for a mirror tested at its CoC.
This is equal to the ptv of the astigmatism wavefront.
The formula (1/16)*(d^2)*(D^2)/R^3 gives the value of this amplitude in the same units used for D, d, R.
If you want to measure it in waves just divide by the wavelength of interest.
C4, the corresponding amplitude of Z4 is 1/2 that value or
C4 = - (1/32)*(d^2)*(D^2)/R^3 (divide by the wavelength to measure it in waves).
This assumes that the y coordinates of the pair of test beam foci are zero.
The result is independent of the conic constant."
Gruss, Beat