Color management method for color representation with self-luminous color primaries
The present invention relates to a unique color management method for calibrating and characterizing a light mixing system comprising a set of primary light modules emitting self-luminous color primaries, which may be intimately mixed to produce a batch color that matches a standard color. The radiant output of each self-luminous color primary, or channel, is modulated by a setting a light controller to a Digital-to-Analog-Conversion (“DAC”) value. In the event that the radiant output of the color primary channels is non-linearly proportioned to the DAC input values, it is useful to employ an innovative “iterative best-fit” method of simultaneously calculating admixtures of light from all color primaries that match a standard color. Otherwise, a matrix method based on matrix algebra may also be used to create a batch color that matches a standard color. A best fit tristimulus value method or best fit minimum RMSD can be used in conjunction with these spectral color matching methods. In addition, an optical feedback method may be used to correct systematic drift of the individual color primary channels.
1. A method of operating a color mixing apparatus comprising the steps of
a. providing a plurality of primary color channels of the color mixing apparatus, wherein the radiant light output of each channel is modulated by a digital-to-analog (DAC) value;
b. selecting a plurality of linear values (LIN) from a black point to a WHITE parameter, wherein the WHITE parameter is the DAC value of each primary channel where a combination of WHITE values for all the primary channel produces a standard white color;
c. selecting a first linear mathematical expression that relates the DAC values to the LIN values;
d. setting the DAC values of each primary color channel of the color mixing apparatus so that the combined outputs of the primary color channels are achromatic for each LIN value; and
e. solving the linear equations using a matrix method.
2. The method of claim 1 , wherein step (e) comprises the steps of
e.1 establishing matrix A to include spectral radiance of each primary color channel,
e.2. establishing matrix b to include spectral radiance of a standard color,
e.3. establishing matrix x to include the gains for the primary color channels,
wherein Ax=b,
wherein x=(A′A) −1 A′b, and
wherein A is a matrix of (m×n), where m and n are integers greater than 0, x is a matrix of (n×1), A′is the transpose of A, b is a matrix of (m×1) and (A′A) −1 A′ is the pseudoinverse of A.
3. The method of claim 2 , wherein n is the number of color primary channels.
4. The method of claim 2 , wherein m is the number of wavelength intervals within the visible electromagnetic spectrum.
5. The method of claim 2 wherein m is the number of wavelength intervals between 360 nm and 780 nm.
6. The method of claim 2 further comprising the step of using the gains in matrix x to calibrate the color mixing apparatus.
7. The method of claim 1 , wherein the plurality of primary color channels comprise light emitting diodes.
8. The method of claim 1 , wherein the plurality of primary color channels comprise at least one of a fluorescent, incandescent and halogen light source.
9. The method of claim 1 , wherein the radiant outputs of the plurality of primary color channels are managed by a controller.