Abstract: A contactless process for detecting electrical patterns on the outer surface of a member comprising providing a member having a charge pattern on an outer surface, repetitively measuring the charge pattern on the outer surface of the member with an electrostatic voltmeter probe maintained at a substantially constant distance from the surface, the distance between the probe and the imaging member being slightly greater than the minimum distance at which Paschen breakdown will occur to form a parallel plate capacitor with a gas between the probe and the surface, the frequency of repetition being selected to cause all time dependent signals to fall out of phase by a predetermined amount, and averaging the out of phase time dependent signals over a sufficient number of measuring repetitions to eliminate the time dependent signals. In one embodiment, the contactless process detects surface potential charge patterns in an electrostatographic imaging member.

Abstract: The present invention is an apparatus for tuning or altering the charge potential limiting effect that a scorotron grid has upon an adjacent charge receiving surface. The scorotron charging apparatus utilizes corona producing means, spaced above the charge retentive surface, for emitting corona ions in response to a high voltage potential applied thereto, and a flexible grid, suspended between said corona producing means and the charge retentive surface in a nonplanar fashion, such that the spacing between said grid and the charge retentive surface is variable along at least one region of said grid.

Abstract: The present invention is a charging apparatus capable of electrically tuning or altering, on a relatively local scale, the corona ion current passing between a corona producing device and a charge retentive surface. The charging apparatus, which may be either a corotron or a scorotron, is specifically adapted to apply a uniform charge to a charge retentive surface which characteristically exhibits non-uniform charging behavior. More specifically, the charging apparatus comprises corona producing devices, spaced apart from the charge retentive surface, for emitting a corona ion current, and device, responsive to a bias voltage, for locally altering the corona ion current passing between said corona producing device and the charge retentive surface.