Aspheric and freeform surfaces metrology with software configurable optical test system: A computerized reverse Hartmann test

Peng Su, Manal A.H. Khreishi, Tianquan Su, Run Huang, Margaret Z. Dominguez, Alejandro Maldonado, Guillaume Butel, Yuhao Wang, Robert E. Parks, James H. Burge

Research output: Contribution to journalArticle

46 Scopus citations


Abstract. A software configurable optical test system (SCOTS) based on deflectometry was developed at the University of Arizona for rapidly, robustly, and accurately measuring precision aspheric and freeform surfaces. SCOTS uses a camera with an external stop to realize a Hartmann test in reverse. With the external camera stop as the reference, a coordinate measuring machine can be used to calibrate the SCOTS test geometry to a high accuracy. Systematic errors from the camera are carefully investigated and controlled. Camera pupil imaging aberration is removed with the external aperture stop. Imaging aberration and other inherent errors are suppressed with an N-rotation test. The performance of the COTS test is demonstrated with the measurement results from a 5-mdiameter Large Synoptic Survey Telescope tertiary mirror and an 8.4-m diameter Giant Magellan Telescope primary mirror. The results show that SCOTS can be used as a large-dynamic-range, high-precision, and non-null test method for precision aspheric and freeform surfaces. The SCOTS test can achieve measurement accuracy comparable to traditional interferometric tests.

Original languageEnglish (US)
Article number031305
JournalOptical Engineering
Issue number3
StatePublished - Jan 1 2014



  • Aspherics
  • Deflectometry
  • Freeform surface
  • Fringe reflection
  • Hartmann test
  • Optical metrology
  • Optical testing

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Engineering(all)

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