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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Vol. 37, Iss. 1 — Jan. 1, 1998
  • pp: 140–155

Phasing the mirror segments of the Keck telescopes: the broadband phasing algorithm

Gary Chanan, Mitchell Troy, Frank Dekens, Scott Michaels, Jerry Nelson, Terry Mast, and David Kirkman  »View Author Affiliations


Applied Optics, Vol. 37, Issue 1, pp. 140-155 (1998)
http://dx.doi.org/10.1364/AO.37.000140


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Abstract

To achieve its full diffraction limit in the infrared, the primary mirror of the Keck telescope (now telescopes) must be properly phased: The steps or piston errors between the individual mirror segments must be reduced to less than 100 nm. We accomplish this with a wave optics variation of the Shack–Hartmann test, in which the signal is not the centroid but rather the degree of coherence of the individual subimages. Using filters with a variety of coherence lengths, we can capture segments with initial piston errors as large as ±30 μm and reduce these to 30 nm—a dynamic range of 3 orders of magnitude. Segment aberrations contribute substantially to the residual errors of ∼75 nm.

© 1998 Optical Society of America

OCIS Codes
(010.7350) Atmospheric and oceanic optics : Wave-front sensing
(040.1240) Detectors : Arrays
(120.5050) Instrumentation, measurement, and metrology : Phase measurement

History
Original Manuscript: January 11, 1997
Revised Manuscript: July 29, 1997
Published: January 1, 1998

Citation
Gary Chanan, Mitchell Troy, Frank Dekens, Scott Michaels, Jerry Nelson, Terry Mast, and David Kirkman, "Phasing the mirror segments of the Keck telescopes: the broadband phasing algorithm," Appl. Opt. 37, 140-155 (1998)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-37-1-140


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References

  1. G. A. Chanan, J. E. Nelson, T. Mast, “Segment alignment for the Keck telescope primary mirror,” in Advanced Technology Optical Telescopes III, L. D. Barr, ed., Proc. SPIE628, 466–470 (1986). [CrossRef]
  2. G. Chanan, J. Nelson, T. Mast, P. Wizinowich, B. Schaefer, “The W. M. Keck telescope phasing camera system,” in Instrumentation in Astronomy VIII, D. L. Crawford, E. R. Craine, eds., Proc. SPIE2198, 1139–1150 (1994). [CrossRef]
  3. G Chanan, M Troy, F Dekens, E Sirko, E Leffert, “Residual misalignments of the Keck telescope primary mirror segments,” submitted to SPIE Symposium on Astronomical Telescopes and Instrumentation (1998).
  4. J. E. Nelson, P. R. Gillingham, “Overview of the performance of the W. M. Keck Observatory,” in Advanced Technology Optical Telescopes V, L. M. Stepp, ed., Proc. SPIE2199, 82–93 (1994). [CrossRef]
  5. D. L. Fried, “Optical resolution through a randomly inhomogeneous medium for very long and very short exposures,” J. Opt. Soc. Am. 56, 1372–1379 (1966). [CrossRef]
  6. G Chanan, G Djorgovski, A Gleckler, S Kulkarni, T Mast, C Max, J Nelson, P Wizinowicheds., “Adaptive optics for Keck Observatory,” Keck Observatory Report 208 (W. M. Keck Library, Kamuela Hawaii, 1996), pp. 3-26 to 3-36.
  7. J Nelson, “Segment mechanical phasing,” Keck Observatory Tech. Note 389 (W. M. Keck Library, Kamuela Hawaii, July1993).
  8. J. E. Nelson, T. S. Mast, S. M. Faber, “The design of the Keck Observatory and telescope,” Keck Observatory Report 90 (W. M. Keck Library, Kamuela Hawaii, 1985), pp. 5-1 to 5-44.
  9. R. W. Cohen, T. S. Mast, J. E. Nelson, “Performance of the W. M. Keck telescope active mirror control system,” in Advanced Technology Optical Telescopes V, L. M. Stepp, ed., Proc. SPIE2199, 105–116 (1994). [CrossRef]
  10. G. Chanan, T. Mast, J. Nelson, “Keck telescope primary mirror segments: initial alignment and active control,” in Proceedings of the European Southern Observatory Conference on Very Large Telescopes and their Instrumentation, M.-H. Ulrich, ed. (Garching, Germany, 1988), pp. 421–428.
  11. G. A. Chanan, “Design of the Keck Observatory alignment camera,” in Precision Instrument Design, T. C. Bristow, A. E. Hatheway, eds., Proc. SPIE1036, 59–70 (1988). [CrossRef]
  12. G. A. Chanan, “Mask/pupil registration for the Keck telescope,” Keck Observatory Tech. Note 253 (W. M. Keck Library, Kamuela Hawaii, 1988).
  13. M. Born, E. Wolf, Principles of Optics, 6th ed. (Pergamon, New York, 1969), pp. 395–398.
  14. W. H. Press, B. P. Flannery, S. A. Teukolsky, W. T. Vetterling, Numerical Recipes: the Art of Scientific Computing (Cambridge U. Press, New York, 1989), pp. 484–487.
  15. T Mast, J Nelson, G Chanan, “Sampling segment phases: minimal spanning sets of zero-sum triplets,” Keck Observatory Tech. Note 208 (W. M. Keck Library, Kamuela Hawaii, 1986).
  16. See Ref. 14, pp. 502–515.
  17. T Mast, “Systematic errors in the alignment camera phase measurement,” Keck Observatory Tech. Note 299 (W. M. Keck Library, Kamuela Hawaii, 1990).
  18. See Ref. 14, pp. 52–64, 515–520.
  19. P. L. Wizinowich, T. S. Mast, J. E. Nelson, M. DiVittorio, G. A. Chanan, “Optical quality of the W. M. Keck telescope,” in Advanced Technology Optical Telescopes V, L. M. Stepp, ed., Proc. SPIE2199, 94–104 (1994). [CrossRef]

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