Adaptive beam-combining mirror for the MMT

Laird M. Close, Guido Brusa, Donald G. Bruns, Michael Lloyd-Hart, Donald W. McCarthy

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


We present a novel, high performance, and economical design for tip-tilt mirrors. The two- dimensional tilt of each mirror is sensed through capacitive displacement sensors sensitive to approximately 1 nm rms out to 10 KHz. An analogue PID circuit utilizes this positional feedback to lock the mirrors to the commanded tilt via voice coil drivers. These mirrors achieve a 10 - 90% risetime of 3.0 ms and have a critically damped response at 100 - 150 Hz update rates. We have incorporated six of these tip-tilt mirrors to adaptively combine all six beams from the MMT. During first light of the instrument in April 1995, individual beams improved from 1.1 inch to 0.6 inch FWHM in 60 s exposures corrected with 60 Hz update rates.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsRobert K. Tyson, Robert Q. Fugate
Number of pages11
StatePublished - 1995
EventAdaptive Optical Systems and Applications - San Diego, CA, USA
Duration: Jul 10 1995Jul 11 1995

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherAdaptive Optical Systems and Applications
CitySan Diego, CA, USA

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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