Electricity: measuring and testing – A material property using electrostatic phenomenon – For flaw detection
Patent
1997-10-30
1999-12-28
Regan, Maura
Electricity: measuring and testing
A material property using electrostatic phenomenon
For flaw detection
324457, 324458, G01N 2760
Patent
active
06008653&
ABSTRACT:
A contactless process for detecting surface potential charge patterns in an electrophotographic imaging member including at least one photoconductive imaging layer having an imaging surface, providing a scanner including a capacitive probe having an outer shield electrode, maintaining the probe adjacent to and spaced from the imaging surface to form a parallel plate capacitor with a gas between the probe and the imaging surface, providing a probe amplifier optically coupled to the probe, establishing relative movement between the probe and the imaging surface, maintaining a substantially constant distance between the probe and the imaging surface, applying a constant voltage charge to the imaging surface prior to relative movement of the probe and the imaging surface past each other, synchronously biasing the probe to within about .+-.300 volts of the average surface potential of the imaging surface, measuring variations in surface potential with the probe, compensating the surface potential variations for variations in distance between the probe and the imaging surface, and comparing the compensated voltage values to a baseline voltage value to detect charge patterns in the electrophotographic imaging member. This process may be conducted with a contactless scanning system comprising a high resolution capacitive probe, a low spatial resolution electrostatic voltmeter coupled to a bias voltage amplifier, and an imaging member having an imaging surface capacitively coupled to and spaced from the probe and the voltmeter, the probe comprising an inner electrode surrounded by and insulated from a coaxial outer Faraday shield electrode, the inner electrode connected to an optocoupled amplifier, and the Faraday shield connected to the bias voltage amplifier.
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Dejak Steven I.
Mishra Satchidanand
Popovic Zoran D.
Regan Maura
Solis Jose M.
Xerox Corporation
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