Abstract: A non-coplanar calibration system exists when the calibration reference plane is offset from a document plane. Due to size, shape, or other factors attributable to a scanning system, it may not be feasible to place the calibration reference plane on the document plane, i.e., the platen glass. Lamp-fall off represents an effect that occurs as you get closer to the ends of the lamp and light energy is diminished. The profile difference between the calibration plane and the document plane in a non-coplanar system can be corrected for on a pixel by pixel basis. Illumination fall off due to the change in the distance from calibration plane to the document plane represents the main effect that must be corrected for. Also, the platen glass must be taken into account. A single calibration correction factor can be applied to each CCD element in a scanning system to account for the shift from calibration plane to document plane.