lens - lens, or say it the quadratic phase corrector.
filters the field through a len.
We have to be very careful, propagating the field to the distance which is close to the focal distance of a positive lens- the near-focal intensity and phase distributions are localized in the central region of the grid occupying only few sampling intervals. This leads to the major loss of information about the field distribution. The problem is solved by applying the coordinate system which is tied to the divergent or convergent light beam. Some functions in SAO are created to do this: convert , lens_fresnel , lens_forvard .
The lens may be decentered, lens (f,8,0.01,0.01) produces a lens with a focal distance of 8= 1/0.125( with an optical power of 0.125D), shifted by 0.01 in X and Y directions. When the lens is shifted, only the phase mask correspondent to the lens is shifted, not the aperture of the lens or light beam itself.
f1=begin(0.04,1e-6); f2=circ_ap(f1,0.02); f3=lens(f2,8); field_plot(f3);
Chen jingyuan, Gan guangyong (IAPCM, Beijing,China.)
tilt , zernike , convert , tor_lens , lens_forvard , lens_fresnel , Lens ,