We present details of optical design, opto-mechanical design and testing of a visible-NIR imaging optical system for a Fourier transform spectrometer dedicated to astronomical application at the Mont Mégantic Observatory (Observatoire du Mont Mégantic, OMM, located south Québec city, Canada). Design considerations as well as testing and experimental results are presented.
An uncooled bolometric FLIR UGS camera is proposed that provides a full 360° FOV. This camera makes use of a 160x120 pixel bolometric FPA which is operated in random access readout mode and a ground-breaking optics forming image in all directions without moving parts, allowing such imaging with no increase in power consumption with respect to a camera with a unidirectional FOV. This novel IR imaging optics can be further equipped with a supplementary objective to provide passive observation of the sky or another fixed direction. The 360° FOV objective is expected to have f/1, to show an MTF value greater than 50% at the FPA Nyquist frequency, and to yield a thermal resolution better than 100 mK.
We present three designs and tolerances of wide-field imagers (30×30 arc-minutes or larger) for astronomical surveying. Two infrared cameras (CPAPIR and PANORAMIX II) were designed for the 0.8-2.4 µm band and a third one (WIRCAM) for the visible and near-infrared band extending from 410 nm to 950 nm. The cameras are installed on the telescopes of the Canada-France-Hawaii (Hawaii, USA) and Mont Mégantic Observatories (Québec, Canada). The three cameras are compact, use only spherical refractive components and have an internal pupil accessible for insertion of filtering components. A Lyot stop must be used in the infrared camera for background rejection. For PANORAMIX II, a set of filters is used at the internal pupil. Correction of the large off-axis aberrations generated by the telescopes, wide spectral coverage, material choices, cryogenic temperature and alignment were the main design challenges. Also, tolerancing was particularly critical for the infrared cameras because they are cryogenically cooled, thus forbidding adjustment of internal components.The cameras' theoretical performances are presented in terms of point-spread function, encircled energy and distortion.
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