26 September 2007 LWIR QWIP focal plane array mounting with cryogenic optical system
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Abstract
We present progress on developing a mechanical and thermal isolation package for maintaining multi-stage temperature control for various parts of a dewar package. Our long-wave QWIP focal plane is maintained at 40K while our optics package, which is at close proximity (~2mm) to the FPA, is maintained at 80K. Radiative baffling is controlled at acceptable levels using high conductance heat sinks, while conductance loads are minimized using proper insulating materials (polyimide synthetics) in combination with materials to preserve high structural stiffness (titanium, invar). Furthermore, the optics package is held at low cryogenic temperatures only ~ 6mm from the ZnSe dewar window. An effort is made to keep the complete electro-optical system at these low temperatures independently using only a single 10W low EM-noise closed cycle cryocooler. Proper geometry is defined which takes into account thermal symmetries and mechanical structural stability, while maintaining the necessary external 300K heat sinks. Both conductance and radiative loading on the opto-mechanical structure are examined using finite element analysis and proper heat sinking is established to thermally isolate the optics within the dewar jacket while maintaining proper structural stability. A custom LCC is designed which maximizes the thermal expansion budget between the FPA and optics package, while necessary structural mounting of the electronics boards are coupled with the dewar coldfinger.
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William R. Johnson, Sarath Gunapala, Jason Mumolo, Dean Johnson, "LWIR QWIP focal plane array mounting with cryogenic optical system", Proc. SPIE 6660, Infrared Systems and Photoelectronic Technology II, 66600G (26 September 2007); doi: 10.1117/12.740034; https://doi.org/10.1117/12.740034
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