Method and apparatus for providing improved color correction in a subtrative color printing system

Claim 1

A method of creating a corrected color control table for use in a subtractive color printing system comprising the steps of: (1) providing a first toner of a first pigment, a second toner of a second pigment, and a third toner of a third pigment; (2) printing a first set of N pigment bars of said first toner on a first predetermined segment of an image receptor, each of said first set of bars having a predetermined density value and N being an integer greater than one; (3) printing a second set of N pigment bars of said second toner on a second predetermined segment of an image receptor, each of said second set of bars having a predetermined density value; (4) printing a third set of N pigment bars of said third toner on a third predetermined segment of an image receptor, each of said third set of bars having a predetermined density value; (5) scanning each of said first, second and third sets of bars through a filter of a first color, a filter of a second color, and a filter of a third color to obtain a plurality of color/pigment values, each of said color/pigment values representing a density value for a particular one of said first, second and third colors from a particular bar of a particular one of said three pigments; (6) creating a value table having at least N 3 entries of a plurality of input triplets, each of said input triplets being of a form: first color, second color, third color, into which a corresponding plurality of pigment triplets is mapped, each of said pigment triplets being of a form: first pigment, second pigment, third pigment; (7) for each of said plurality of input triplets; (a) calculating an output triplet by calculating color contributions for each of said three colors from each of said three pigments using a corresponding pigment triplet mapped by said input triplet and said color/pigment values; (b) calculating an error value for said input triplet, said error value representing a mathematical difference between said input triplet and said output triplet; (c) modifying said corresponding pigment triplet and repeating steps (a) and (b) until either said error value is less than a predetermined error value or said steps (a) and (b) have been repeated a predetermined number of times; (8) storing said value table for use in said subtractive color printing system.

Claim 2

A method of creating a corrected color control table for use in a subtractive color printing system comprising the steps of: (1) providing a first toner of a first pigment, a second toner of a second pigment, and a third toner of a third pigment; (2) printing a first set of N pigment bars of said first toner on a first predetermined segment of an image receptor, each of said first set of bars having a predetermined density value and N being an integer greater than one; (3) printing a second set of N pigment bars of said second toner on a second predetermined segment of an image receptor, each of said second set of bars having a predetermined density value; (4) printing a third set of N pigment bars of said third toner on a third predetermined segment of an image receptor, each of said third set of bars having a predetermined density value; (5) scanning each of said first, second and third sets of bars through a filter of a first color, a filter of a second color, and a filter of a third color to obtain a plurality of color/pigment values, each of said color/pigment values representing a density value for a particular one of said first, second and third colors from a particular bar of a particular one of said three pigments; (6) creating a value table having at least N 3 entries of a plurality of input triplets, each of said input triplets being of a form: first color, second color, third color, into which a corresponding plurality of pigment triplets is mapped, each of said pigment triplets being of a form: first pigment, second pigment, third pigment; (7) for each of said plurality of input triplets; (a) calculating an output triplet by calculating color contributions for each of said three colors from each of said three pigments using a corresponding pigment triplet mapped by said input triplet and said color/pigment values; (b) calculating an error value for said input triplet, said error value representing a mathematical difference between said input triplet and said output triplet; (c) modifying said corresponding pigment triplet and repeating steps (a) and (b) until either said error value is less than a predetermined error value or said steps (a) and (b) have been repeated a predetermined number of times; (8) storing said value table for use in said subtractive color printing system.

Claim 5

A method of correcting color in a subtractive color printing system comprising the steps of: (1) providing a first toner of a first pigment, a second toner of a second pigment, and a third toner of a third pigment; (2) printing a first set of N pigment bars of said first toner on a first predetermined segment of an image receptor, each of said first set of bars having a predetermined density value and N being an integer greater than one; (3) printing a second set of N pigment bars of said second toner on a second predetermined segment of an image receptor, each of said second set of bars having a predetermined density value; (4) printing a third set of N pigment bars of said third toner on a third predetermined segment of an image receptor, each of said set of bars having a predetermined density value; (5) scanning each of said first, second and third sets of bars through a filter of a first color, a filter of a second color, and a filter of a third color to obtain a plurality of color/pigment values, each of said color/pigment values representing a density value for a particular one of said first, second and third colors from a particular bar of a particular one of said three pigments; (6) creating a value table having at least N 3 entries of a plurality of input triplets, each of said input triplets being of a form: first color, second color, third color, into which a corresponding plurality of pigment triplets is mapped, each of said pigment triplets being of a form: first pigment, second pigment, third pigment; (7) for each of said plurality of input triplets; (a) calculating an output triplet by calculating color contributions for each of said three colors from each of said three pigments using a corresponding pigment triplet mapped by said input triplet and said color/pigment values; (b) calculating an error value for said input triplet, said error value representing a mathematical difference between said input triplet and said output triplet; (c) modifying said corresponding pigment triplet and repeating steps (a) and (b) until either said error value is less than a predetermined error value or said steps (a) and (b) have been repeated a predetermined number of times; (8) storing said value table in said subtractive color printing system; (9) providing first, second, and third image color signals from an image source; and (10) applying said first, second, and third image color signals as said input triplet to said value table and using said pigment triplet mapped thereby to control deposition of said first pigment, said second pigment, and said third pigment on output image receptors.

Claim 6

A method of correcting color in a subtractive color printing system comprising the steps of: (1) providing a first toner of a first pigment, a second toner of a second pigment, and a third toner of a third pigment; (2) printing a first set of N pigment bars of said first toner on a first predetermined segment of an image receptor, each of said first set of bars having a predetermined density value and N being an integer greater than one; (3) printing a second set of N pigment bars of said second toner on a second predetermined segment of an image receptor, each of said second set of bars having a predetermined density value; (4) printing a third set of N pigment bars of said third toner on a third predetermined segment of an image receptor, each of said set of bars having a predetermined density value; (5) scanning each of said first, second and third sets of bars through a filter of a first color, a filter of a second color, and a filter of a third color to obtain a plurality of color/pigment values, each of said color/pigment values representing a density value for a particular one of said first, second and third colors from a particular bar of a particular one of said three pigments; (6) creating a value table having at least N 3 entries of a plurality of input triplets, each of said input triplets being of a form: first color, second color, third color, into which a corresponding plurality of pigment triplets is mapped, each of said pigment triplets being of a form: first pigment, second pigment, third pigment; (7) for each of said plurality of input triplets; (a) calculating an output triplet by calculating color contributions for each of said three colors from each of said three pigments using a corresponding pigment triplet mapped by said input triplet and said color/pigment values; (b) calculating an error value for said input triplet, said error value representing a mathematical difference between said input triplet and said output triplet; (c) modifying said corresponding pigment triplet and repeating steps (a) and (b) until either said error value is less than a predetermined error value or said steps (a) and (b) have been repeated a predetermined number of times; (8) storing said value table in said subtractive color printing system; (9) providing first, second, and third image color signals from an image source; and (10) applying said first, second, and third image color signals as said input triplet to said value table and using said pigment triplet mapped thereby to control deposition of said first pigment, said second pigment, and said third pigment on output image receptors.

Claim 7

A method of creating a corrected color control table for use in a subtractive color printing system comprising the steps of: (1) providing a first toner of a cyan pigment, a second toner of a magenta pigment, and a third toner of a yellow pigment; (2) printing a first set of 16 pigment bars of said first toner on a first predetermined segment of an image receptor, each of said first set of bars having a predetermined density value, each of said predetermined density values differing from a respective one of said predetermined density values for an adjacent one of said pigment bars by a predetermined density difference; (3) printing a second set of 16 pigment bars of said second toner on a second predetermined segment of an image receptor, each of said second set of bars having a predetermined density value, each of said predetermined density values differing from a respective one of said predetermined density values for an adjacent one of said pigment bars by said predetermined density difference; (4) printing a third set of 16 pigment bars of said third toner on a third predetermined segment of an image receptor, each of said third set of bars having a predetermined density value, each of said predetermined density values differing from a respective one of said predetermined density values for an adjacent one of said pigment bars by said predetermined density difference; (5) scanning each of said first, second and third sets of bars through a red filter, a green filter, and a blue filter to obtain a plurality of color/pigment values, each of said color/pigment values representing a density value for a particular one of said red, green, and blue colors from a particular bar of a particular one of said cyan, magenta, and yellow pigments; (6) creating a value table having at least 4096 entries of a plurality of input triplets, each of said input triplets being of a form: red value, green value, blue value, into which a corresponding plurality of pigment triplets is mapped, each of said pigment triplets being of a form: cyan value, magenta value, yellow value; (7) for each of said plurality of input triplets; (a) calculating an output triplet in a form: red output value, green output value, blue output value by calculating color contributions for each of said three colors from each of said three pigments using a corresponding pigment triplet mapped by said input triplet of said color/pigment values; (b) calculating an error value for said input triplet, said error value representing a mathematical difference between respective red, green, and blue values of said input triplet and said output triplet; (c) modifying said cyan pigment value in said corresponding pigment triplet by multiplying same by 1+(red value-red output value)/(2×red value); (d) modifying said magenta pigment value in said corresponding pigment triplet by multiplying same by 1+(green value-green output value)/(2×green value); (e) modifying said yellow pigment value in said corresponding pigment triplet by multiplying same by 1+(blue value-blue output value)/(2×blue value); (f) and repeating steps (a) through (e) until either said error value is less than a predetermined error value or said steps (a) through (e) have been repeated a predetermined number of times; (8) storing said value table for use in said subtractive color printing system.

Claim 8

A method of creating a corrected color control table for use in a subtractive color printing system comprising the steps of: (1) providing a first toner of a cyan pigment, a second toner of a magenta pigment, and a third toner of a yellow pigment; (2) printing a first set of 16 pigment bars of said first toner on a first predetermined segment of an image receptor, each of said first set of bars having a predetermined density value, each of said predetermined density values differing from a respective one of said predetermined density values for an adjacent one of said pigment bars by a predetermined density difference; (3) printing a second set of 16 pigment bars of said second toner on a second predetermined segment of an image receptor, each of said second set of bars having a predetermined density value, each of said predetermined density values differing from a respective one of said predetermined density values for an adjacent one of said pigment bars by said predetermined density difference; (4) printing a third set of 16 pigment bars of said third toner on a third predetermined segment of an image receptor, each of said third set of bars having a predetermined density value, each of said predetermined density values differing from a respective one of said predetermined density values for an adjacent one of said pigment bars by said predetermined density difference; (5) scanning each of said first, second and third sets of bars through a red filter, a green filter, and a blue filter to obtain a plurality of color/pigment values, each of said color/pigment values representing a density value for a particular one of said red, green, and blue colors from a particular bar of a particular one of said cyan, magenta, and yellow pigments; (6) creating a value table having at least 4096 entries of a plurality of input triplets, each of said input triplets being of a form: red value, green value, blue value, into which a corresponding plurality of pigment triplets is mapped, each of said pigment triplets being of a form: cyan value, magenta value, yellow value; (7) for each of said plurality of input triplets; (a) calculating an output triplet in a form: red output value, green output value, blue output value by calculating color contributions for each of said three colors from each of said three pigments using a corresponding pigment triplet mapped by said input triplet of said color/pigment values; (b) calculating an error value for said input triplet, said error value representing a mathematical difference between respective red, green, and blue values of said input triplet and said output triplet; (c) modifying said cyan pigment value in said corresponding pigment triplet by multiplying same by 1+(red value-red output value)/(2×red value); (d) modifying said magenta pigment value in said corresponding pigment triplet by multiplying same by 1+(green value-green output value)/(2×green value); (e) modifying said yellow pigment value in said corresponding pigment triplet by multiplying same by 1+(blue value-blue output value)/(2×blue value); (f) and repeating steps (a) through (e) until either said error value is less than a predetermined error value or said steps (a) through (e) have been repeated a predetermined number of times; (8) storing said value table for use in said subtractive color printing system.