Integrated Ray Tracing (IRT) simulation of SCOTS surface measurement of GMT Fast Steering Mirror Prototype

Ji Nyeong Choi, Dongok Ryu, Sug Whan Kim, Logan Graves, Peng Su, Run Huang, Dae Wook Kim

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

1 Scopus citations


The Software Configurable Optical Testing System (SCOTS) is one of the newest testing methods for large mirror surfaces. The Integrated Ray Tracing (IRT) technique can be applicable to the SCOTS simulation by performing non-sequential ray tracing from the screen to the camera detector in the real scale. Therefore, the radiometry of distorted pattern images are numerically estimated by the IRT simulation module. In this study, we construct an IRT SCOTS simulation model for the Fast Steering Mirror Prototype (FSMP) surface of the Giant Magellan Telescope (GMT). GMT FSMP is an off-axis ellipsoidal concave mirror that is 1064 mm in diameter and has PV 3.1 mm in aspheric departure. The surface error requirement is less than 20 nm rms. The screen is modeled as an array of 1366 by 768 screen pixels of 0.227 mm in pitch size. The screen is considered as a Lambertian scattering surface. The screen and the camera are positioned around 4390 mm away from the mirror and separated by around 132 mm from each other. The light source are scanning lines and sinusoidal patterns generated by 616,050 rays per one screen pixel. Of the initially generated rays, 0.22 % are received by the camera's detector and contribute to form distorted pattern images. These images are converted to the slope and height maps of the mirror surface. The final result for the height difference between input surface and reconstructed surface was 14.14 nm rms. Additionally, the simulated mirror pattern image was compared with the real SCOTS test for the GMT FSMP. This study shows applicability of using the IRT model to SCOTS simulation with nanometer level numerical accuracy.

Original languageEnglish (US)
Title of host publicationOptical Manufacturing and Testing XI
EditorsRay Williamson, Oliver W. Fahnle, Dae Wook Kim
ISBN (Electronic)9781628417418
StatePublished - 2015
EventOptical Manufacturing and Testing XI - San Diego, United States
Duration: Aug 9 2015Aug 11 2015

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


OtherOptical Manufacturing and Testing XI
Country/TerritoryUnited States
CitySan Diego


  • Deflectometry
  • Integrated Ray Tracing
  • Optical Testing

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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