A wavefront measured over a clear circular pupil at nm
PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Geometrical optics and imaging · Geometrical optics and imaging
What an Instrument Can See, Ch Aberrations: the phase written on the pupil
Problem
A wavefront measured over a clear circular pupil at λ=550 nm, after a best-focus adjustment has removed piston, tip, tilt and defocus, has Noll Zernike coefficients a5=30 nm, a6=20 nm (astigmatism), a7=24 nm, a8=18 nm (coma), and a11=12 nm (primary spherical aberration). All other coefficients are zero.
((a)) Compute the rms wavefront error σW, in nanometres and in waves at 550 nm.
((b)) State whether the Maréchal approximation is expected to hold for this wavefront, giving the reason.
((c)) Estimate the Strehl ratio using the Maréchal formula.