1. A method for producing an image of an electrical characteristic of an object, the steps comprising: a) applying a voltage to the surface of the object with an array of sensor elements; b) measuring the surface charge at each sensor element that results from the applied voltage; c) transforming the surface charge measurements; d) calculating the distribution of charges inside the object by multiplying the transformed surface charge measurements by a stored charge correlation matrix; and e) producing an image of an electrical property of the object from the internal charge distribution data calculated in step d).