US RE42,673 E1Granted

State-space based modeling of pixel elements of a dynamically varying color marking device

AssigneeXerox Corporation

InventorLalit K. Mestha

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Abstract

The color management system comprises a state-space based model for a pixel element in a dynamically varying color marking device. A sensor measures the color of the printed output for construction of a selected set of sensitivity functions representative of color output relating to inputs. The gradients of the sensitivity functions are extracted and used to develop the corresponding discrete multivariable state-space model of the pixel element. More particularly, the model is constructed from the Jacobian matrix characterizing a change in measured color output for a change in input color values of the pixel. Extension of modeling methodology for a single pixel is applied to multiple pixel elements.

Claims11

Dependent claims

A method for modeling the pixel elements of a dynamically varying color reproduction device from output image pixels generated in response to a test target, including steps of:

producing an output image with the device in response to an input signal from the test target wherein the test target comprises a plurality of pixels;
measuring with a sensor an output signal representative of the output image corresponding to a target preselected color;
and
constructing a linear state-space model of color producing behavior for a single pixel including a matrix characterization of the color reproduction device, wherein the matrix characterization represents a gradient of change of a plurality of color sensitivity function iss represented as a Jacobian matrix, the gradient is with respect to the input signal for the measured output signal at a nominal set of measured output values, and the gradient is predetermined as linear about the nominal values,
wherein the state-space model represents the color reproduction device operation in terms of a derivative function between device input and output as:
y(k+1) x(k+1)=BV(K)(k)+X0
where k is an iteration number, X0 are L*, a*, b* values for a nominal CMY values, and,
χ
=
[
L
*
a
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b
*
]
,
V
=
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∂
C
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M
∂
Y
]
,
B
=
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∂
a
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⁢
⁢
χ
o
=
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L
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a
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b
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]
.
values for nominal CMY.

90 more elements

A color marking device including a control system for calibration of the device based upon dynamic color balance control of an output image, the system comprising:

a front end converter for converting an input signal representative of a target image comprising a preselected color into a device-dependent control signal in accordance with a linear state-space model;
a color marking device for outputting an output image in response to the control signal;
a sensor for measuring a parameter from the output image representative of a color of the output image;
an open loop system for comparing the parameter with a corresponding parameter from the target image and constructing a sensitivity function of output color about a selected set of nominal device color input values;
and,
a closed loop system controller for constructing the linear state-space model from a gradient of the sensitivity function at the selected set of nominal device input color values, at a nominal set of respective measured output values wherein the gradient is predetermined as linear about the nominal values,
whereby subsequently generated output images are output with the closed loop system controller and more accurately represent target input images, and
the open loop system comprises a representation of the state-space model of color marking device operation between device input and output as:
X(k+1)=BV(K)(k)+Xo
where k is an iteration number, Xo are L*, a*, b* values for a nominal CMY values, and,
χ
=
[
L
*
a
*
b
*
]
,
V
=
[
∂
C
∂
M
∂
Y
]
,
B
=
[
∂
L
*
∂
C
∂
L
*
∂
M
∂
L
*
∂
Y
∂
a
*
∂
C
∂
a
*
∂
M
∂
a
*
∂
Y
∂
b
*
∂
C
∂
b
*
∂
M
∂
b
*
∂
Y
]
⁢
χ
o
=
[
L
*
a
*
b
*
]
values for nominal CMY.

91 more elements

Dependencies are inferred from the claim text.

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Abstract