Standardized color calibration of electronic imagery

A system for recording a standardized color image of an object, comprising:

• means for providing electrical signals representing a colored image of the object;
• means for resolving an output of a light-source illuminating the object into a spectrum;
• means for providing a gray-scale representation of said light source;
• and means for calibrating said electrical signals using said spectrum and said gray scale representation of said light source.

A system for recording a standardized color image of an object, comprising:

• means for forming an image of the object on a plurality of red (r), green (g), and blue (b) detectors, said detectors producing r, g, and b signals characterizing said image as a plurality of r, g, and b pixels;
• means for recording said r, g, and b signals;
• means for providing a gray-scale representation of a light-source illuminating the object;
• means for recording responses of said r, g, and b detectors for a plurality of different values in said gray scale;
• means for converting said r, g, and b detector responses into CIE X, Y and Z values;
• means for resolving an output of the light-source illuminating the object into a spectrum;
• means for recording said light-source spectrum using said r, g, and b detectors to produce r, g and b spectra of said light source;
• means for comparing said r, g and b spectra of said light-source with CIE X, Y, and Z matching curves and generating from said comparison a transformation matrix for converting said r, g and b signals into said CIE X, Y, and Z values;
• and
• means for converting, using said transformation matrix, said recorded r, g, and b signals into equivalent CIE X, Y, and Z values for the object as illuminated by the light source using said transformation matrix.

A method of prod a calibrated color image of an object, comprising the steps of

• forming an image of the object on a plurality of red (r), green (g) and blue (b) detectors, said detectors producing r, g, and b signals characterizing said image as a plurality of r, g and b pixels;
• recording said r, g, and b signals;
• providing a gray-scale representation of a light-source illuminating the object;
• recording a responses of said r, g, and b detectors for a plurality of different values in said gray scale;
• converting said r, g, and b detector responses into CIE X, Y, and Z values;
• resolving an output of the light-source illuminating the object into a spectrum;
• recording said light-source spectrum using said r, g, and b detectors to produce r, g, and b spectra of said light source;
• comparing said r, g, and b spectra of said light-source with CIE X, Y, and Z matching curves and generating from said comparison a transformation matrix for converting said r, q, and b signals into said CIE X, Y, and Z values:
• and
• converting said r, g, and b signals into CIE X, Y and Z values for the object as illuminated by the light source.

A method of prod a calibrated color image of an/object, comprising the steps of:

• forming an image of the object on a plurality of red (r), green (g), and blue (b) detectors, said detectors producing r, g, and b signals characterizing said image as a plurality of r, g, and b pixels;
• recording said r, g, and b signals;
• providing a gray-scale representation of a light-source illuminating the object;
• recording responses of said r, g, and b detectors for a plurality of different values in said gray scale;
• linearizing the responses of said r, g, and b detectors for a plurality of different values in said gray scale;
• resolving an output of the light-source illuminating the object into a spectrum;
• recording said light-source spectrum using said r, g, and b detectors to produce r, g and b spectra of said light source;
• linearizing said r, g, and b spectra;
• comparing said linear r, g, and b spectra of said light-source with CIE X, Y, and Z matching curves and generating from said comparison a transformation matrix for converting said r, g, and b signals into CIE X, Y, and Z values;
• converting said r, g, and b signals into equivalent CIE X, Y, and Z values for the object as illuminated by the light source;
• and
• converting said linearized r, g, and b detector responses into CIE X, Y, and Z values parameterized by luminance.

A method of calibrating a color printer, comprising the steps of:

• creating a table of driving values for driving a printer mechanism;
• producing a color strip on a test sheet for each table entry;
• illuminating each color strip with a light source;
• imaging reflected light from each color strip sequentially through a spectral plate into a detector to generate color strip spectra;
• imaging sampled light from the light source through the spectral plate into a detector to form a light source spectrum;
• dividing said color strip spectra by said light source spectrum to provide normalized color strip spectra;
• convolving said normalized color strip spectra with a CIE X, Y, and Z matching curves to generate the CIE X, Y, and Z values of said color strips;
• creating a mathematical map correlating said driving values with said CIE X, Y, and Z values;
• and
• creating an inverse of said mathematical map for correlating any CIE X, Y, and Z color values with said driving values.