Printer calibration

Claim 1

A method for improving a color transform for a printer comprising the steps of: transforming predetermined data, representing a color test pattern, into a digital image in a device-dependent color space associated with the printer by use of a test pattern transform, said test pattern transform comprising a portion of the color transform pertaining to the printer coupled with any solution set formed by a previous instantiation of said method, wherein said color test pattern data includes a set of color patches in a device-independent color space with one of said color patches representing a preferred mid-gray hue and other patches representing colors that are close to said preferred mid-gray hue in said device-independent color space; printing said digital image to create a printed color test pattern; providing a reference gray surface having a spectral reflectance characteristic that is flat or nearly flat and a gray level that is the same as said preferred mid-gray hue; comparing said reference gray surface to said set of colored patches of the printed test pattern to find a closest matching one of said patches, if the closest matching one of said patches is the patch representing the preferred mid-gray hue, then ending the method; otherwise storing a data set of values indicative of the closest matching one of said colored patches; determining, for each color channel of the printer, a solution set of correction values as a function of believed values versus actual values, said solution set derived from and including a point {0,0}, a point {1.0,1.0}, whereby the maximum printer device value is normalized to 1.0, and a point mapped at {G b , G a } where G b is the believed value of the closest matching one of said patches and G a is the actual value of the closest matching one of said patches; adding to the color transform the corresponding solution set for each color channel of the printer; and repeating this method using the color transform having the corresponding solution set added thereto.

Claim 2

A method for improving a color transform for a printer comprising the steps of: transforming predetermined data, representing a color test pattern, into a digital image in a device-dependent color space associated with the printer by use of a test pattern transform, said test pattern transform comprising a portion of the color transform pertaining to the printer coupled with any solution set formed by a previous instantiation of said method, wherein said color test pattern data includes a set of color patches in a device-independent color space with one of said color patches representing a preferred mid-gray hue and other patches representing colors that are close to said preferred mid-gray hue in said device-independent color space; printing said digital image to create a printed color test pattern; providing a reference gray surface having a spectral reflectance characteristic that is flat or nearly flat and a gray level that is the same as said preferred mid-gray hue; comparing said reference gray surface to said set of colored patches of the printed test pattern to find a closest matching one of said patches, if the closest matching one of said patches is the patch representing the preferred mid-gray hue, then ending the method; otherwise storing a data set of values indicative of the closest matching one of said colored patches; determining, for each color channel of the printer, a solution set of correction values as a function of believed values versus actual values, said solution set derived from and including a point {0,0}, a point {1.0,1.0}, whereby the maximum printer device value is normalized to 1.0, and a point mapped at {G b , G a } where G b is the believed value of the closest matching one of said patches and G a is the actual value of the closest matching one of said patches; adding to the color transform the corresponding solution set for each color channel of the printer; and repeating this method using the color transform having the corresponding solution set added thereto.

Claim 5

A system for improving a color transform for a printer comprising: means for transforming predetermined data, representing a color test pattern, into a digital image in a device-dependent color space associated with the printer by use of a test pattern transform, said test pattern transform comprising a portion of the color transform pertaining to the printer coupled with any solution set formed by a previous instantiation of said method, wherein said color test pattern data includes a set of color patches in a device-independent color space with one of said color patches representing a preferred mid-gray hue and other patches representing colors that are close to said preferred mid-say hue in said device-independent color space; means for printing said digital image to create a printed color test pattern: means for comparing a reference gray surface, having a spectral reflectance characteristic that is flat or nearly flat and a gray level that is the same as said preferred mid-gray hue, to said set of colored patches of the test pattern rendered by the printer to find a closest matching one of said patches, ceasing operation if the closest matching one of said patches is the patch representing the preferred mid-gray hue; means for storing a data set of values indicative of the closest matching one of said colored patches; means for determining, for each color channel of the printer, a solution set of correction values as a function of believed values versus actual values, said solution set derived from and including a point {0,0}, a point {1.0, 1.0}, whereby the maximum printer device value is normalized to 1.0, and a point mapped at {G b , G a } where G b is the believed value of the closest matching one of said patches and G a is the actual value of the closest matching one of said patches; means for adding to the color transform the corresponding solution set for each color channel of the printer; and means for restarting the system using the color transform having the corresponding solution set added thereto.

Claim 6

A system for improving a color transform for a printer comprising: means for transforming predetermined data, representing a color test pattern, into a digital image in a device-dependent color space associated with the printer by use of a test pattern transform, said test pattern transform comprising a portion of the color transform pertaining to the printer coupled with any solution set formed by a previous instantiation of said method, wherein said color test pattern data includes a set of color patches in a device-independent color space with one of said color patches representing a preferred mid-gray hue and other patches representing colors that are close to said preferred mid-say hue in said device-independent color space; means for printing said digital image to create a printed color test pattern: means for comparing a reference gray surface, having a spectral reflectance characteristic that is flat or nearly flat and a gray level that is the same as said preferred mid-gray hue, to said set of colored patches of the test pattern rendered by the printer to find a closest matching one of said patches, ceasing operation if the closest matching one of said patches is the patch representing the preferred mid-gray hue; means for storing a data set of values indicative of the closest matching one of said colored patches; means for determining, for each color channel of the printer, a solution set of correction values as a function of believed values versus actual values, said solution set derived from and including a point {0,0}, a point {1.0, 1.0}, whereby the maximum printer device value is normalized to 1.0, and a point mapped at {G b , G a } where G b is the believed value of the closest matching one of said patches and G a is the actual value of the closest matching one of said patches; means for adding to the color transform the corresponding solution set for each color channel of the printer; and means for restarting the system using the color transform having the corresponding solution set added thereto.