Lenslet Arrays
Here is the electromagnetic field amplitude formed from diffractive
propagation of a plane wave through three different types of
apertures, and through a 16x16 square lenslet array. The
electromagnetic frequency was 1 micron, and the lenslets were chosen
to have a 100 micron pitch, with a 2.5 millimeter focal length.
(These are the approximate parameters chosen for the wavefront sensors
in the Palomar MGSU experiment.) The size of the pupil was chosen to
be 1.5 millimeters, so as to slightly underfill the pixel
array.
These images are shown on a linear stretch, but are stretched quite a
bit to show the fine detail. The first sidelobe of the diffraction
pattern is visible in the amplitude of each lenslet. Also visible are
the edge effects arising from partially illuminated lenslet
subapertures at the edges of the apertures. The spidered annulus on
the far right was rotated two degrees with respect to the lenslet
array, so that the distortions arising from the spiders in the image
are slightly asymmetric.
Here is an image showing the intensity measured by a detector in the
focal plane of the lenslet array arising from a turbulence-corrupted
wavefront.
