Principles and Applications of Difference Imaging
  The principles of difference imaging outlined and the technique of Alard and Lupton (1997) is generalised to generate the best possible difference images to within the limits of measurement error. It is shown how for a large database of images we can approach diffraction-limited spatial resolution to within measurement error of a combined image. This is achieved through an iterative procedure of difference imaging and deconvolution. The design of the ideal imager to approach this limit is discussed. 
Austin B. Tomaney