A Caltech Library Service

Phasing the Mirror Segments of the Keck Telescopes: The Broadband Phasing Algorithm

Chanan, Gary and Troy, Mitchell and Dekens, Frank and Michaels, Scott and Nelson, Jerry and Mast, Terry and Kirkman, David (1998) Phasing the Mirror Segments of the Keck Telescopes: The Broadband Phasing Algorithm. Applied Optics, 37 (1). pp. 140-155. ISSN 0003-6935.

See Usage Policy.


Use this Persistent URL to link to this item:


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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Additional Information:© 1998 Optical Society of America Received 11 January 1997; revised manuscript received 29 July 1997.
Issue or Number:1
Record Number:CaltechAUTHORS:CHAao98
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2924
Deposited By: Archive Administrator
Deposited On:06 May 2006
Last Modified:02 Oct 2019 22:58

Repository Staff Only: item control page