Abstract: Designs for constructing a surface with variable emittance are described. This is achieved by making a surface where the emissivity varies on a scale smaller than the resolution of a thermal imager viewing the surface. One design utilizes many cylindrical surfaces with their axis parallel and their surfaces nearly in contact. Individual cylinders have the property that when rotated to zero degrees they show a surface with an emissivity of one and when rotated to 180 degrees display a surface with an emissivity of zero. At intermediate angles of rotation a sensor that could resolve individual cylinders would see alternate lines with high and low emittance but a sensor unable to resolve individual cylinders sees a surface with an emittance that depends on the angle the cylinders are rotated. Variable emittance surfaces are expected to be useful for controlling target signature and for making spectral reflectivity measurements using a hyper-spectral radiometer.

Abstract: An in-camera supplemental exposure correction system for achieving an evenly exposed final photographic image in a situation wherein the photographic scene is non-uniformly illuminated by an artificial light source by pre-exposing the film to supplemental illumination having a non-uniform pattern which is the inverse of the artificial scene illumination.