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Browse Prior Art Database

Device for Measuring Surface Conductivity

IP.com Disclosure Number: IPCOM000110035D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 85K

Publishing Venue

IBM

Related People

Keefe, GE: AUTHOR [+2]

Abstract

Disclosed is a device for measuring the surface conductivity of the photoconductor in electrophotographic printers as a means of detecting the impending onset of print "washout". Print "washout" occurs when high resolution features such as isolated pels appear faint or disappear. The lateral motion of charge during the time between image formation and development leads to a resolution loss that depends directly on the surface conductivity of the photoconductor (1). Chemical degradation of the photoconductor by corona gases is a primary cause of increased conductivity. Some of these effects and attempts to mitigate them by reducing chemical contamination sources are described in (2). This effect is vey dependent on the pattern of usage and is not simply related to the total number of pages printed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Device for Measuring Surface Conductivity

       Disclosed is a device for measuring the surface
conductivity of the photoconductor in electrophotographic printers as
a means of detecting the impending onset of print "washout".  Print
"washout" occurs when high resolution features such as isolated pels
appear faint or disappear.  The lateral motion of charge during the
time between image formation and development leads to a resolution
loss that depends directly on the surface conductivity of the
photoconductor (1).  Chemical degradation of the photoconductor by
corona gases is a primary cause of increased conductivity.  Some of
these effects and attempts to mitigate them by reducing chemical
contamination sources are described in (2).  This effect is vey
dependent on the pattern of usage and is not simply related to the
total number of pages printed.

      The mechanism of charge transport on the surface of
photoconductor is not well understood, but the charge motion has been
found to be well characterized by a 2-D version of Ohm's law (3).  As
a consequence, a charge pattern that is uniform along one direction
but sinusoidally varying along the other will decay exponentially in
time.  For wavelengths much longer than the thickness of the
photoconductor, the time constant is proportional to the square of
the pattern wavelength and inversely proportional to the surface
conductivity.  Basically, this technique consists of measuring the
rate of decay of a test pattern to determine the surface
conductivity.

      More specifically, a series of horizontal lines are written as
the test pattern.  Such a pattern consists of a superposition of
different wavelength components.  Electronic filtering is used to
extract the amplitudes of the individual wavelength components from
the raw charge signal.  Each decays at a different rate due to
surface conduction.  There is an overall decay of the pattern due to
dark decay, but it occurs equally for all wavelengths.  By taking the
ratio of two different wavelength components, dark decay is
eliminated.

      The amplitude of the surface c...