Contactless system and method for detecting defective points on a chargeable surface

Abstract

A method for detecting charge defect spots (CDSs) on a chargeable surface is provided, including charging the chargeable surface to receive and hold a first voltage charge, spacing a surface of a scanner probe a distance from the chargeable surface, the scanner probe having a diameter, and biasing the scanner probe to a second voltage charge within a predetermined voltage threshold of the first voltage charge, wherein a parallel plate capacitor is established with the chargeable surface and a dielectric substance between the scanner probe and the chargeable surface. The method further includes reading with the scanner probe potentials associated with charges induced from the applied charges and any CDSs on the chargeable surface, including sensing the potentials and generating a signal corresponding to the sensing, applying a reference charge to the chargeable surface, and determining the potential of a CDS on the chargeable surface based on the scanner probe readings and at least one of the applied charges, which includes correcting for non-uniform charge distribution caused by a point-like nature of the CDS on the chargeable surface.