Advanced Imaging

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Advanced Imaging Magazine

Updated: January 12th, 2011 09:49 AM CDT

Standing Up to Harsh Environments

Electronic imaging in the real world must survive heat, contamination, shock and radiation
Thick-walled cast-steel or aluminum housings protect cameras from extreme external shock and isolate flammable volatiles from camera sparks.
APG
Thick-walled cast-steel or aluminum housings protect cameras from extreme external shock and isolate flammable volatiles from camera sparks.
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By Kristin Lewotsky

For higher temperatures, liquid cooling via a cold plate may provide a more economical, compact, robust solution. A cold plate consists of an aluminum sheet backed by steel tubes through which chilled water runs. Another approach, says McGeary, is to put a bare aluminum reflector plate between the camera and the heat source. Uncoated aluminum is a good re-radiator that can dramatically reduce the amount of heat reaching the imager.

Vision system designers for space systems face not only extreme temperatures but thermal swings of several hundred degrees Kelvin. Although the surface of Mars has a thin atmosphere, the surface of the Moon is in vacuum, which eliminates convective cooling. Meanwhile, temperatures on the dark side of the moon far exceed the standard military temperature minimum of -55° C.

To minimize the effect of thermal expansion, MSSS builds its telescopes out of graphite epoxy, which is both lightweight and dimensionally stable. The team also uses specialty circuit boards incorporating materials with coefficients of thermal expansion (CTEs) that better match the components mounted on them. For their cameras on the Mars Science Laboratory rover they built qualification units and thermal cycled them 2,000 times from room temperature to below -100° C.

DIRTY BUSINESS

Whether it’s dust kicked up on the surface of Mars or cough syrup splattered by a broken bottle on a packaging line, contamination is a perennial problem in a large number of vision applications. Here again, enclosures can help.

Many food applications, for example, involve daily washdown with water or corrosive chemicals. Enclosures can protect imaging hardware, but they have to be the right type. “Customers and the FDA don’t want anything over the line that you wouldn’t want to find in the food,” says McGeary. That means no nickel or chrome plating, no glass, and few paints. Food-rated enclosures also cannot feature any hollows or depressions that can retain water or other materials and potentially form bacteria.



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