21 September 2011 Cryogenic lens design case study: Gemini Planet Imager spectrograph
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Making a lens design working at cryogenic temperature is a real challenge. Both optical and mechanical designer must work together to prevent problems during operation. The Gemini Planet Imager (GPI), currently under construction will be a facility instrument for the 8-m Gemini South telescope. The science instrument is a cryogenic integral field spectrograph based on a lenslet array. The integral field nature of the instrument allows for a full mapping of the focal plane at coarse spectral resolution. With such a data cube, artifacts within the PSF such as residual speckles can be suppressed. Additionally, the initial detection of any candidate planet will include spectral information that can be used to distinguish it from a background object: candidates can be followed up with detailed spectroscopic observations. The optics between the lenslet array and the detector are essentially a standard spectrograph with a collimating set of lenses, a dispersive prism and a camera set of lenses in a folded assembly. This paper describes the process from the first preliminary design to the final cryogenic system for both optical and mechanical design to achieve cryogenic working solution. We also discussed the assembly procedure (room temperature vs cryogenic compensation), the test support equipments and finally the laboratory optical performances over the field of view.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
S. Thibault, S. Thibault, } "Cryogenic lens design case study: Gemini Planet Imager spectrograph", Proc. SPIE 8128, Current Developments in Lens Design and Optical Engineering XII; and Advances in Thin Film Coatings VII, 812802 (21 September 2011); doi: 10.1117/12.894944; https://doi.org/10.1117/12.894944

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