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Applied Optics

Applied Optics


  • Vol. 43, Iss. 23 — Aug. 10, 2004
  • pp: 4474–4481

Experimental verification of dispersed fringe sensing as a segment phasing technique using the Keck telescope

Fang Shi, Gary Chanan, Catherine Ohara, Mitchell Troy, and David C. Redding  »View Author Affiliations

Applied Optics, Vol. 43, Issue 23, pp. 4474-4481 (2004)

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Dispersed fringe sensing (DFS) is an efficient and robust method for coarse phasing of segmented primary mirrors (from one quarter of a wavelength to as much as the depth of focus of a single segment, typically several tens of microns). Unlike phasing techniques currently used for ground-based segmented telescopes, DFS does not require the use of edge sensors in order to sense changes in the relative heights of adjacent segments; this makes it particularly well suited for phasing of space-borne segmented telescopes, such as the James Webb Space Telescope. We validate DFS by using it to measure the piston errors of the segments of one of the Keck telescopes. The results agree with those of the Shack-Hartmann-based phasing scheme currently in use at Keck to within 2% over a range of initial piston errors of ±16 μm.

© 2004 Optical Society of America

OCIS Codes
(010.7350) Atmospheric and oceanic optics : Wave-front sensing
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(220.1140) Optical design and fabrication : Alignment

Original Manuscript: February 27, 2004
Revised Manuscript: May 10, 2004
Published: August 10, 2004

Fang Shi, Gary Chanan, Catherine Ohara, Mitchell Troy, and David C. Redding, "Experimental verification of dispersed fringe sensing as a segment phasing technique using the Keck telescope," Appl. Opt. 43, 4474-4481 (2004)

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  1. G. A. Chanan, M. Troy, F. G. Dekens, S. Michaels, J. Nelson, T. Mast, D. Kirkman, “Phasing the mirror segments of the Keck telescopes: the broadband phasing algorithm,” Appl. Opt. 37, 140–155 (1998). [CrossRef]
  2. G. A. 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]
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  5. F. Shi, D. C. Redding, A. E. Lowman, C. W. Bowers, L. A. Burns, P. Petrone, C. M. Ohara, S. A. Basinger, “Segmented mirror coarse phasing with a dispersed fringe sensor: experiments on NGST’s Wavefront Control Testbed,” in IR Space Telescopes and Instruments, J. C. Mather, ed., Proc. SPIE4850, 318–328 (2002). [CrossRef]
  6. 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]
  7. J. E. Nelson, T. S. Mast, S. M. Faber, “The design of the Keck Observatory and Telescope,” Keck Observatory Report 90 (W. M. Keck Observatory, Kamuela, Hawaii, 1985).

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