Design of the cryogenic wheel mechanisms for IRCS and NIRI

James Bell, Jeffrey W. Douglass, Klaus Werner Hodapp, Naoto Kobayashi, Louis Robertson, Alan T. Tokunaga, Tony T. Young

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

5 Scopus citations


The IR camera and spectrograph (IRCS) for SUBARU and Gemini near-IR imager (NIRI) instruments have a common design for all wheels, based on a modified geneva mechanisms with a locking cam actuated detent pin. The geneva design, in combination with the spring loaded detent mechanism, allows the stepper motor/spur gear drive to decouple from the wheel at each aperture position. The detent mechanism positions the wheel precisely. The need for precise motor control and wheel position encoding is reduced because of the detent mechanism. Six of these mechanism are filters wheels requiring repeatable aperture positing. The other seven mechanisms include of a slit wheel, grism wheel, pupil mask wheel, 2 beam steerers, a focal p;lane mask wheel, and a beamsplitter wheel. These mechanisms require repeatable, stable and accurate positioning. The number of aperture positions for the 13 wheels range from 2 to 16. The mechanisms are aligned and tested at room temperature and operated at 60 K, requiring an athermal design, for which the modified geneva mechanism is ideally suited. This paper will discuss the prototype development and final mechanical design of specific wheel mechanisms completed for the IRCS and NIRI instruments at the Institute for Astronomy.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
Number of pages8
StatePublished - 1998
Externally publishedYes
EventInfrared Astronomical Instrumentation - Kona, HI, United States
Duration: Mar 23 1998Mar 23 1998


OtherInfrared Astronomical Instrumentation
Country/TerritoryUnited States
CityKona, HI


  • Beam steerer
  • Beamsplitter
  • Filter
  • Grism
  • Mask
  • Pupil mask
  • Slit
  • Wheel, mechanism

ASJC Scopus subject areas

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


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