Fresnel phasing of segmented mirror telescopes.


Shack-Hartmann (S-H) phasing of segmented telescopes is based upon a physical optics generalization of the geometrical optics Shack-Hartmann test, in which each S-H lenslet straddles an intersegment edge. For the extremely large segmented telescopes currently in the design stages, one is led naturally to very large pupil demagnifications for the S-H phasing cameras. This in turn implies rather small Fresnel numbers F for the lenslets; the nominal design for the Thirty Meter Telescope calls for F=0.6. For such small Fresnel numbers, it may be possible to eliminate the lenslets entirely, replacing them with a simple mask containing a sparse array of clear subapertures and thereby also eliminating a number of manufacturing problems and experimental complications associated with lenslets. We present laboratory results that demonstrate the validity of this approach.

DOI: 10.1364/AO.50.006283

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@article{Chanan2011FresnelPO, title={Fresnel phasing of segmented mirror telescopes.}, author={Gary A Chanan and Mitchell Troy and Isabelle Surdej and G. M. Gutt and Lewis C. Roberts}, journal={Applied optics}, year={2011}, volume={50 33}, pages={6283-93} }