Electrophotography – Control of electrophotography process – Of plural processes
Reexamination Certificate
2003-02-13
2004-08-03
Tran, Hoan (Department: 2852)
Electrophotography
Control of electrophotography process
Of plural processes
C399S048000, C399S049000, C399S051000, C399S053000
Reexamination Certificate
active
06771912
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention concerns creation of a photo-induced discharge curve (PIDC) for the process controls, xerographic setup and diagnostics of a print engine.
2. Description of Related Art
Electrophotographic process characteristics affect images made using a xerographic photoreceptor. The xerographic process includes several steps. The contrast output range characteristics arise mainly from characteristic responses called transfer functions. One of the process steps is charging a photoreceptor and another is exposing a photoreceptor. One important transfer function is that of the photoreceptor.
The transfer characteristic of the photoreceptor system is known as the photo-induced discharge curve (PIDC) and is a plot of the surface potential of the photoreceptor as a function of incident light exposure. The shape of this discharge curve for a given photoreceptor depends on a number of factors, such as, for example, the field dependence, if any, of the photogeneration processes in the photoreceptor pigment, the field dependence of the efficiency of charge injection from the photoreceptor pigment into the photoreceptor transport layer, and the range, i.e., distance per unit field, of the charge carriers in the transport layer. In many practical photoreceptors, the photo-induced discharge curve is approximately linear with light exposure except at low voltages, which corresponds with exposure to high light intensities, where field dependent mechanisms decrease the rate of discharge.
Determining the photo-induced discharge curve for a xerographic system is needed if the system is to operate around the optimum contrast potentials.
U.S. Pat. No. 4,647,184, incorporated herein by reference in its entirety, is one of a number of patents which monitor xerographic system operating parameters and maintain a photo-induced discharge curve (PIDC) for a particular xerographic system once the photo-induced discharge curve (PIDC) for that system has been determined and established. The 184 patent discloses automatic setup systems and methods for establishing basic xerographic system operating parameters. As disclosed in the 184 patent, each xerographic machine is associated with the same development potentials (V
I
-V
D
) by adjusting the shape of the photo-induced discharge curve, which was previously determined to ensure uniform output copy quality across a plurality of such xerographic machines.
The photo-induced discharge curve is a fundamental characteristic of a photoreceptor that has been charged to a specific dark potential V
O
in combination with the reflective density of the input document and the document illumination intensity. However, any given population of photoreceptors will have a distribution of shapes. Digital values representing the slope of the photo-induced discharge curve are contained within memory of each machine. The setup mode and associated apparatus are designed to measure the basic parameters of the particular machine and plot the photo-induced discharge curve based on these measured values. To the extent that the actual shape of the photo-induced discharge curve varies from a standard shape of the photo-induced discharge curve, the basic parameters of charge voltage I
C
, developer bias V
BIAS
and system exposure E
O
are adjusted in an iterative process, until the measured values converge on the preset values.
U.S. Pat. No. 5,471,313, incorporated herein in its entirety by reference, discloses a xerographic device whose laser power controller includes a setup routine that determines the relationship between the initial charge on the photoreceptor V
hi
and exposed voltage V
ex
as a function of laser power setting and stores these relationships as curves on a graph. These curves provide an initial estimate of the required laser power. A feedback laser power controller takes the initial charge level V
hi
and a discharge ratio DR and determines an appropriate discharge level from the setup data, measures the exposed value V
low
on the photoreceptor, and adjusts laser power for changing photoreceptor properties. The discharge ratio DR=(V
low
−V
res
)/(V
hi
−V
res
), where V
res
equals a baseline voltage, measured by exercising laser power exposure until the exposed voltage does not discharge further with increasing exposure power. The discharge ratio indicates how the development potential V
dev
and cleaning field V
clean
are positioned on the photo-induced discharge curve, where V
clean
is a cleaning field equal to the difference between a housing bias voltage and the voltage of areas discharged by exposure.
U.S. Pat. No. 5,797,064 discloses a pseudo photo-induced discharge curve setup procedure for a xerographic system which does not use an electrostatic voltmeter (ESV). The 064 patent determines the knee of the photo-induced discharge curve whenever a photoreceptor or raster output scanner (ROS) is changed. The method of generating the pseudo photo-induced discharge curve is set forth in the 064 patent.
SUMMARY OF THE INVENTION
It has been appreciated that current PIDC generators either take a long time, such as, for example, a number of weeks, to achieve a fine-tuned photo-induced discharge curve or use a number of polynomial curve-fitting techniques that typically are not very accurate.
An accurate real-time PIDC generator makes it possible to achieve better performance for xerographic process control and xerographic system setup and possibly reduced total service hours (TSH) for a xerographic system.
This invention provides systems and methods for generating a photo-induced discharge curve.
This invention separately provides systems and methods for generating the photo-induced discharge curve in real time.
This invention separately provides systems and methods for determining the parameters for a photo-induced discharge curve generator.
This invention separately provides systems and methods that control xerographic processes using a photo-induced discharge curve generator.
This invention separately provides systems and methods that setup a xerographic system using a photo-induced discharge curve generator.
In various exemplary embodiments, the systems and method according to this invention use photoreceptor physics to obtain a nonlinear model structure for a photo-induced discharge curve. In various exemplary embodiments, the systems and methods according to this invention use a nonlinear optimization approach to estimate the parameters utilized by a photo-induced discharge curve generator based on empirical test data for each individual photoreceptor belt at a specific photoreceptor lifetime. In various exemplary embodiments, the systems and methods according to this invention use a nonlinear model structure based on the physics of a photoreceptor, e.g., a photoreceptor belt and/or a photoreceptor drum, and estimate the parameters of an individual photo-induced discharge curve model for applications used by xerographic process controls, xerographic diagnostics, and/or xerographic system setup in real-time. In various exemplary embodiments, the photo-induced discharge curve is obtained sufficiently fast to permit use of the photo-induced discharge curve to affect the operation of the xerographic system for which the photo-induced discharge curve was generated as that system operates.
Various exemplary embodiments of the systems and methods according to this invention create a photo-induced discharge curve generator in real-time.
Various exemplary embodiments of the systems and methods according to this invention use a nonlinear model structure based on the physics of the photoreceptor to generate a photo-induced discharge curve in real-time.
Various exemplary embodiments of the systems and methods according to this invention use a nonlinear parameter estimation approach to estimate the parameters of the PIDC generator for an individual photo-induced discharge curve.
Various exemplary embodiments of the systems and methods according to this invention estimate a number of parameters, such
Apton Wendy K.
Drawe Jeffrey W.
Mo Song-feng
Randall Stephen F.
Oliff & Berridg,e PLC
Tran Hoan
Xerox Corporation
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