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 natural...

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Bibliographic Details
Published in:Applied optics (2004) 2011-11, Vol.50 (33), p.6283-6293
Main Authors: Chanan, Gary, Troy, Mitchell, Surdej, Isabelle, Gutt, Gary, Roberts, Jr, Lewis C
Format: Article
Language:English
Subjects:
Arrays
Cameras
Geometrical optics
Measuring instruments
Phasing
Physical optics
Segmented mirrors
Telescopes
Online Access:Get full text
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Summary: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.
ISSN:1559-128X
2155-3165
DOI:10.1364/AO.50.006283