Patent ID: 7271593
Filing Date: 2007-09-18
Classification: G03G

Abstract:
1. A contactless system for detecting charge defect spots (CDSs) on a chargeable surface comprising: first circuitry for charging the chargeable surface to receive and hold a first voltage charge; a scanner probe having a probe surface, the probe surface being displaced a distance from the chargeable surface, and having a diameter; second circuitry for 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 surface and the chargeable surface, wherein the scanner probe reads 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; third circuitry for applying a reference charge to at least one of the scanner probe and the chargeable surface; a processor; and a charge determination module including programmable instructions executable by the processor for determining the potential of a CDS on the chargeable surface based on the scanner probe readings and at least one of the applied charges, including correcting for a non-uniform charge distribution caused by a point-like nature of the CDS on the chargeable surface; wherein the correcting comprises adjusting the determined potential of the CDS based on the diameter of the scanner probe and the distance from the scanner probe surface to the chargeable surface at a location where the chargeable surface is being scanned.