Camera, Infrared, Dewar
Wednesday, August 30, 2006
An Infrared Camera has been designed and developed utilizing an arsenic-doped extrinsic silicon photodetector as part of a ground-based telescope.
The Camera is designed so that background radiation generated by the telescope tube, warm optics, and the atmosphere does not saturate the photodetector array. A liquid helium-cooled Lyot stop is located at the real image of the secondary mirror using a reimaging optical system. There is no direct radiation light path to the photodetector array.
To reduce thermal radiation, a 10°K cryogenic environment is maintained by a liquid nitrogen and liquid helium Dewar. The Dewar can be tilted up to 80 degrees from the vertical without spilling cryogen. The Dewar has a hold time of about 30 hours.
Misalignment of the optical system is prevented during cryogenic cool down by using a two-lens optical design. The two-lens germanium imaging system brings the image to a focus at the photodetector array inside the Dewar. Primary focus is located near the field lens, reducing image aberration in the relay optics. The image of the secondary mirror is reimaged at the Lyot stop.
Source: None Available Reference: 1) Infrared Laboratories, Inc., Tucson, AZ; 2) G. Williams and J. Fraser, Photon Research Associates, La Jolla, CA
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posted by JD52 @ 9:45 PM,
