Reduction of aliasing in staring infrared imagers utilizing subpixel techniques

In this paper, we will introduce and analyze techniques for the reduction of aliased power in a staring infrared imaging system. A standard staring system uses a fixed two dimensional detector array which implies a fixed spatial sampling frequency corresponding to the detector to detector spacing. Aliasing will occur when sampling a scene containing spatial frequencies exceeding half of this sampling frequency. Most natural scenes are not band limited and aliasing can significantly degrade the quality and utility of the resulting image. The alias reduction schemes presented here are based upon microscanning, which is an optical technique utilizing subpixel shifts between multiple time frames in an image sequence. These multiple images are used to reconstruct a single frame with reduced aliasing, The microscanning techniques presented here are divided into the categories of controlled and uncontrolled techniques. If the microscanning is controlled, using a microscan mirror or beam steerer for example, one can obtain a uniformly sampled microscanned image. The reconstruction in this case is a relatively simple task. In an uncontrolled case, the sampling may be nonuniform and the reconstruction becomes more complicated. Experimental results are presented which illustrate that the quality of a microscanned image can be dramatically improved over a non-microscanned image as well as demonstrate the utility of the applied algorithms