OSA's Digital Library

Applied Optics

Applied Optics


  • Vol. 41, Iss. 7 — Mar. 1, 2002
  • pp: 1297–1307

Phasing segmented mirrors: a modification of the Keck narrow-band technique and its application to extremely large telescopes

Achim Schumacher, Nicholas Devaney, and Luzma Montoya  »View Author Affiliations

Applied Optics, Vol. 41, Issue 7, pp. 1297-1307 (2002)

View Full Text Article

Enhanced HTML    Acrobat PDF (278 KB)

Browse Journals / Lookup Meetings

Browse by Journal and Year


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools



Future telescopes with diameters greater than 10 m, usually referred to as extremely large telescopes (ELTs), will employ segmented mirrors made up of hundreds or even thousands of segments, with tight constraints on the piston errors between individual segments. The 10-m Keck telescopes are routinely phased with the narrow-band phasing technique. This is a variation of the Shack-Hartmann wave-front sensor in which the signal is the correlation between individual subimages and simulated images. We have investigated the applicability of this technique to ELTs, and in the process we have developed what to our knowledge is a new algorithm in which each subimage provides on its own a piston-dependent value. We also discuss an alternative algorithm to resolve the λ ambiguity that allows detection of problematic cases, and a modification of the singular-value-decomposition procedure used to phase the whole mirror, using weightings on individual measurement errors. By means of simulations we show that the modified technique shows improved performance and that it can work with sufficient precision on telescopes as large as 100 m.

© 2002 Optical Society of America

OCIS Codes
(010.7350) Atmospheric and oceanic optics : Wave-front sensing
(040.1240) Detectors : Arrays
(110.6770) Imaging systems : Telescopes
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(220.1140) Optical design and fabrication : Alignment

Original Manuscript: June 27, 2001
Revised Manuscript: October 19, 2001
Published: March 1, 2002

Achim Schumacher, Nicholas Devaney, and Luzma Montoya, "Phasing segmented mirrors: a modification of the Keck narrow-band technique and its application to extremely large telescopes," Appl. Opt. 41, 1297-1307 (2002)

Sort:  Author  |  Year  |  Journal  |  Reset  


  1. C. D. Bello, N. Devaney, J. Castro, “The effect of piston errors on the image quality of ground-based segmented mirror telescopes,” Rev. Mex. Astron. Astrofis. 36, 57–66 (2000).
  2. G. W. Zeiders, E. E. Montgomery, “Diffraction effects with segmented apertures,” in Space Telescopes and Instruments V, P. Y. Bely, J. B. Breckinridge, eds., Proc. SPIE3356, 799–809 (1998). [CrossRef]
  3. N. Yaitskova, K. Dohlen, “Simulation of imaging performance for extremely large segmented telescopes,” in Optical Design, Materials, Fabrication, and Maintenance, P. Dierickx, ed., Proc. SPIE4003, 279–290 (2000). [CrossRef]
  4. N. Yaitskova, K. Dohlen (both of Observatoire de Marseille, 2 Place Le Verrier, 13248 Marseille cedex 4, France) are preparing a manuscript to be called “Theoretical and computational study of the image quality in extremely large segmented telescopes.”
  5. D. Gavel, “The effect of the Keck telescope’s segmented primary on the performance of the Keck adaptive optics system,” in Adaptive Optics and Applications, R. K. Tyson, R. Q. Fugate, eds., Proc. SPIE3126, 144–150 (1997). [CrossRef]
  6. C. D. Bello Figueroa, “Improving the image quality of large segmented mirror telescopes,” Ph.D. dissertation (Instituto de Astrofı́sica de Canarias, La Laguna, Tenerife, Spain, 2000).
  7. N. Devaney, L. Cavaller, L. Jochum, C. D. Bello, J. Castro, “Guacamole: the GTC guiding, acquisition and calibration module,” in Optical Design, Materials, Fabrication, and Maintenance, P. Dierickx, ed., Proc. SPIE4003, 146–153 (2000). [CrossRef]
  8. G. Chanan, M. Troy, F. Dekens, S. Michaels, J. Mast, D. Kirkman, “Phasing the mirror segments of the Keck telescopes: the broadband phasing algorithm,” Appl. Opt. 37, 140–155 (1998). [CrossRef]
  9. G. Chanan, C. Ohara, M. Troy, “Phasing the mirror segments of the Keck telescopes II: the narrow-band phasing algorithm,” Appl. Opt. 39, 4706–4714 (2000). [CrossRef]
  10. M. Löfdahl, H. Eriksson, “An algorithm for resolving 2π ambiguities in interferometric measurements by use of multiple wavelengths,” Opt. Eng. 40, 2019–2058 (2001).
  11. B. Lasker, C. Sturch, B. McLean, J. Russel, H. Jenker, M. Shara, “The Guide Star Catalog. I. Astronomical foundations and image processing,” Astron. J. 99, 2019–2058 (1990). [CrossRef]
  12. W. H. Press, B. P. Flannery, S. A. Teukolsky, W. T. Vetterling, Numerical Recipes in C: the Art of Scientific Computing (Cambridge University, New York, 1992), Chap. 2.
  13. G. Chanan, M. Troy, C. Ohara, “Phasing the primary mirror segments of the Keck telescopes: a comparison of different techniques,” in Optical Design, Materials, Fabrication, and Maintenance, P. Dierickx, ed., Proc. SPIE4003, 188–201 (2000). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited