1. A system that maximizes information content in an image fusion process that blends co-registered low light level images in the visible region of the electromagnetic spectrum with thermal infrared images, said infrared and visible images constituting two different image types, the system comprising: a fusion module for detecting which of the two image types has a greater quantity of structural information and increasing a weight of the pixels in the image type detected to have the greater quantity of structural information; and a plurality of contrast detectors in the fusion module for detecting a contrast for the two image types, wherein the plurality of contrast detectors include modules for determining an average standard deviation of pixel values for pixels in an image.