Construction and testing of the wavefront sensor camera for the new MMT adaptive optics system

P. C. McGuire, T. A. Rhoadarmer, M. Lloyd-Hart, J. C. Shelton, M. P. Lesser, J. R.P. Angel, G. Z. Angeli, J. M. Hughes, B. C. Fitz-Patrick, M. L. Rademacher, P. Schaller, M. A. Kenworthy, F. P. Wildi, J. G. Capara, D. B. Ouellete

Research output: Contribution to journalConference articlepeer-review

3 Scopus citations


This paper describes the construction and testing of the Shack-Hartmann wavefront sensor (WFS) camera for the new MMT adaptive optics system. Construction and use of the sensor is greatly simplified by having the 12 × 12 lenslet array permanently glued to the detector array, obviating the need for any further realignment. The detector is a frame transfer CCD made by EEV with 80 × 80 pixels, each 24 microns square, and 4 output amplifiers operated simultaneously. 3 × 3 pixel binning is used to create in effect an array of quad-cells, each centered on a spot formed by a lenslet. Centration of the lenslet images is measured to have an accuracy of 1 μm (0.02 arcsec) rms. The maximum frame rate in the binned mode is 625 Hz, when the rms noise is 4.5 - 5 electrons. In use at the telescope, the guide star entering the wavefront sensor passes through a 2.4 arcsec square field stop matched to the quad-cell size, and each lenslet samples a 54 cm square segment of the atmospherically aberrated wavefront to form a guide star image at a plate scale of 60 μm/arcsec. Charge diffusion between adjacent detector pixels is small: the signal modulation in 0.7 arcsec seeing is reduced by only 10% compared to an ideal quad-cell with perfectly sharp boundaries.

Original languageEnglish (US)
Pages (from-to)269-282
Number of pages14
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 1999
EventProceedings of the 1999 Adaptive Optics Systems and Technology - Denver, CO, USA
Duration: Jul 21 1999Jul 22 1999

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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