An exact expression for the image error in a catadioptric sensor
  A catadioptric sensor induces a projection between a given object surface and an image plane. The prescribed projection problem is the problem of finding a catadioptric sensor that realizes a given projection. Here we present a functional that describes the image error induced by a given mirror when compared with a given projection. This expression can be minimized to find solutions to the prescribed projection problem. We present an example of this approach, by finding the optimum spherical mirror that serves as a passenger side mirror on a motor vehicle. 
R. Andrew Hicks