Visual based process control apparatus which is based on a near uniform human visual response space
First Claim
1. In an image reproduction device, apparatus for automatically adjusting process control parameters to achieve reproductions in terms of human visual response;
- said apparatus comprising;
means for producing reproductions;
means for making a plurality of density measurements across a range of densities;
means for converting the density measurements to a near uniform human visual space;
means for calculating a set of error signals for the converted density measurements in accordance with human visual sensitivities of said near uniform human visual space;
means responsive to said set of error signals for calculating a set of process control parameter adjustment signals to minimize a performance index which is a function of said error signals; and
means responsive to said set of parameter adjustment signals for adjusting process control parameters to influence reproduction.
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Abstract
While the human eye does not respond linearly to density and luminance changes, it does respond linearly to lightness L*. Equal increments on the L* scale do represent approximately equal steps in the perceived lightness of related colors. Near uniform color scales are available wherein equal differences in the color co-ordinates correspond to roughly equal visual differences. Accordingly, the disclosure relates to a visual-based process control method for copiers and printers which is based on a near uniform human visual response space rather than a density space. This gives a better control on the average for minimizing error in the human visual space than if the density space is used.
27 Citations
21 Claims
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1. In an image reproduction device, apparatus for automatically adjusting process control parameters to achieve reproductions in terms of human visual response;
- said apparatus comprising;
means for producing reproductions; means for making a plurality of density measurements across a range of densities; means for converting the density measurements to a near uniform human visual space; means for calculating a set of error signals for the converted density measurements in accordance with human visual sensitivities of said near uniform human visual space; means responsive to said set of error signals for calculating a set of process control parameter adjustment signals to minimize a performance index which is a function of said error signals; and means responsive to said set of parameter adjustment signals for adjusting process control parameters to influence reproduction. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- said apparatus comprising;
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8. In a color image reproduction device, apparatus for automatically adjusting process control parameters for a plurality of color separations to achieve reproductions in terms of human visual response;
- said apparatus comprising;
means for producing reproductions; means for making a plurality of density measurements across a range of densities for each color separation; means for converting the density measurements to a near uniform color space; means for calculating a set of error signals for the converted density measurements in accordance with human visual sensitivities of said near uniform color space; means responsive to said set of error signals for calculating a set of process control parameter adjustment signals to minimize a performance index which is a function of said error signals; and means responsive to said set of parameter adjustment signals for adjusting process control parameters to influence reproduction. - View Dependent Claims (9, 10, 11, 12, 13)
- said apparatus comprising;
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14. A system for adjusting process control parameter in an electrostatographic machine, said system comprising:
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means for producing a plurality of different density test patches; means for making density measurements of said test patches; means for converting the measured densities to a visual based system; means for determining the error between the converted density signals and a set of desired values; and means for adjusting the electrostatographic process in accordance with the determined error. - View Dependent Claims (15, 16)
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17. A system for adjusting process control parameter in a color electrostatographic machine, said system comprising:
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means for producing a plurality of different density test patches for each color; means for making density measurements of said test patches; means for converting the measured densities to a near uniform color space wherein equal differences in the color co-ordinates correspond to roughly equal visual differences; means for determining the error between the converted density color co-ordinates and a set of desired co-ordinates; and means for adjusting the electrostatographic process in accordance with the determined error. - View Dependent Claims (18, 19, 20, 21)
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Specification