At 11:50 04/12/2009, Michael Koch wrote:
Now let's move the mirror 0.1mm on the optical axis and take a
new interferogram. This interferogram must show some power. How
can this amount of power be calculated? I tried to derive a
formula and got this one:
Z3 = x / (8 N^2)
where x is the movement on the optical axis, and N is the ratio
R/D, with R = radius of curvature and D = mirror diameter.
Z3 is the Zernike coefficient for the reflected wavefront (not
for the surface error).
Taking Steve's hint I checked Suiter's derivation. He gets this
formula for Peak to Valley defocus. Peak to 0 -- the Zernike
coefficient -- would be half as large.