Optical fabrication of the MMT adaptive secondary mirror

H. M. Martin, J. H. Burge, C. Del Vecchio, L. R. Dettmann, S. M. Miller, B. Smith, F. Wildi

Research output: Contribution to journalConference articlepeer-review

24 Scopus citations


We describe the optical fabrication of the adaptive secondary mirror for the MMT. The 640 mm f/15 secondary consists of a flexible glass shell, 1.8 mm thick, whose shape is controlled by 336 electromagnetic actuators. It is designed to give diffraction-limited images at a wavelength of 1 micron. For generating and polishing, the shell was supported by attaching it to a rigid glass blocking body with a thin layer of pitch. It could then be figured and measured using techniques developed for rigid secondaries. The highly aspheric surface was polished with a 30 cm stressed lap and small passive tools, and measured using a swing-arm profilometer and a holographic test plate. The goal for fabrication was to produce diffraction-limited images in the visible, after simulated adaptive correction using only a small fraction of the typical actuator forces. This translates into a surface accuracy of less than 19 nm rms with correction forces of less than 0.05 N rms. We achieved a surface accuracy of 8 nm rms after simulated correction with forces of 0.02 N rms.

Original languageEnglish (US)
Pages (from-to)I/-
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 2000
EventAdaptive Optical Systems Technology - Munich, Ger
Duration: Mar 29 2000Mar 31 2000

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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