Continuously variable aperture cold stop

We propose to build a continuously variable size cold stop that is mounted in a dewar and operates at LN2 temperatures. A fully functional dewar system will be demonstrated during phase I, using manual micrometer via a feedthrough. Under the proposedoption the variable cold stop will be motorized.A simple scheme, that monitors signal level in selected FPA regions, can be used then in a manner equivalent to auto exposure control to control the cold stop aperture for optimal camera dynamic range. A variable cold stop can optimize operations of allcooled (as well as uncooled) IR cameras. The technology can be made a standard feature in most commercial camera types to improve performance by adjusting the f/# to match the incoming radiance just like conventional lenses are used in common photography.