Color measurement and calibration

Abstract

Embodiments described herein disclose a color measurement device and method for use with cameras or other imaging devices. The color measurement device may be configured to determine many different colors via a commonly owned device. Embodiments utilize sinusoidal grayscale rings to determine an exact color match of an unknown color, even if there is perspective distortion of an obtained image.

What I claim is: 
     
         1 . A system for determining a true color of an unknown color sample, the system comprising:
 a template including a cut-out and a plurality of concentric rings around the cut-out, each of the concentric rings having offset gray scales modulated as a function of an angle of a polar coordinate, wherein there is a trigonometric relationship between the gray scales of the plurality of concentric rings;   a RGB color module configured to determine, in an image of the template over the unknown color sample, a first radial cross-section of one of the concentric rings having an intensity that matches a determined average red color value of the image of the unknown color sample and to determine a true average red color value of the unknown color sample based on an intensity profile of the one of the concentric rings and a polar angle of the first radial cross-section; and   an angular module configured to determine the polar angle of the first radial cross-section.   
     
     
         2 . The system of  claim 1 , wherein the angular module is configured to determine the polar angle of the first radial cross-section by comparing the intensity in the image of the first radial cross-section with an intensity in the image of a radial cross-section of another of the concentric rings along the same radial segment and utilizing the trigonometric relationship between the gray scales of the concentric rings. 
     
     
         3 . The system of  claim 1 , wherein the RGB color module is further configured to determine, in the image of the template over the unknown color sample, a second radial cross-section of a second one of the concentric rings having an intensity that matches a determined average green color value of the image of the unknown color sample and to determine a true average green color value of the unknown color sample based on a ring intensity profile of the second one of the concentric rings and a polar angle of the second radial cross-section, and to determine, in the image of the template over the unknown color sample, a third radial cross-section of a third one of the concentric rings having an intensity that matches a determined average blue color value of the image of the unknown color sample and to determine a true average blue color value of the unknown color sample based on a ring intensity profile of the third one of the concentric rings and a polar angle of the third radial cross-section, and wherein the angular module is configured to determine the polar angle of the second and third radial cross-sections. 
     
     
         4 . The system of  claim 3 , further comprising an exact color module configured to determine the true color of the unknown color sample based on the true average red color value, the true average green color value, and the true average blue color value. 
     
     
         5 . The system of  claim 1 , wherein each concentric ring is phase shifted a given angle from each other concentric ring. 
     
     
         6 . The system of  claim 5 , wherein the plurality of concentric rings comprise three concentric rings, the second concentric ring being phase shifted a first given angle from the first concentric ring and the third concentric ring being phase shifted a second given angle from the second concentric ring. 
     
     
         7 . The system of  claim 1 , further comprising an image capturing device configured to obtain an image of the template over the unknown color sample. 
     
     
         8 . The system of  claim 1 , wherein the template further comprises distinctive markings at known locations and wherein the center of the concentric rings can be determined from an image of the template using geometric relationships between the distinctive markings and the center. 
     
     
         9 . The system of  claim 8 , wherein the template is rectangular, the distinctive markings comprise corner markings, and the center of the concentric rings is at the center of the template, wherein the center of the concentric rings in the image can be determined based on an intersection of a first line from a first of the corner markings diagonally to a third of the corner markings and a second line from a second of the corner markings diagonally to a fourth of the corner markings, wherein the center of the concentric rings is then used to determine the radial segment on which a radial cross-section lies. 
     
     
         10 . The system of  claim 1 , wherein the RGB module is further configured to determine, in the image of the template over the unknown color sample, another radial cross-section of another of the concentric rings having an intensity that matches the determined average red color value of the image of the unknown color sample and to determine a second true average red color value of the unknown color sample based on an intensity profile of the another of the concentric rings and a different polar angle of the another radial cross-section, and to determine a final true average red color value of the unknown color sample by calculating a weighted average of the true average red color value and the second true average red color value. 
     
     
         11 . A method for determining a color of an unknown color sample, the method comprising:
 positioning a cut-out of a template over the unknown color sample, the template comprising the cut-out and one or more concentric rings around the cut-out, each of the concentric rings comprising a gray scale continuum that varies in intensity as a function of polar angle;   obtaining an image of the unknown color sample via the cut-out and the template;   determining a first radial cross-section of one of the concentric rings that matches a measured average red color value of the unknown color sample in the image;   determining a polar angle of the first radial cross-section; and   determining a corrected average red color value of the unknown color sample using the polar angle of the first radial cross-section.   
     
     
         12 . The method of  claim 11 , wherein obtaining the image comprises actuating an image-capturing device. 
     
     
         13 . The method of  claim 11 , wherein the polar angle of the first radial cross-section is determined by comparing the intensity in the image of the first radial cross-section with an intensity in the image of a radial cross-section of another of the concentric rings along the same radial segment as the first radial cross-section and utilizing a trigonometric relationship between the gray scale continuums of the concentric rings. 
     
     
         14 . The method of  claim 11 , further comprising determining, from the image, a second radial cross-section of a second one of the concentric rings having an intensity that matches a measured average green color value of the image of the unknown color sample and determining a corrected average green color value of the unknown color sample using a polar angle of the second radial cross-section, and determining, from the image, a third radial cross-section of a third one of the concentric rings having an intensity that matches a measured average blue color value of the image of the unknown color sample and determining a corrected average blue color value of the unknown color sample using a polar angle of the third radial cross-section, and determining the polar angle of the second and third radial cross-sections. 
     
     
         15 . The method of  claim 13 , further comprising determining the color of the unknown color sample based on the corrected average red color value, the corrected average green color value, and the corrected average blue color value. 
     
     
         16 . The method of  claim 11 , wherein the template further comprises distinctive markings at known locations and further comprising determining the center of the concentric rings from the image using geometric relationships between the distinctive markings and the center, and using the center of the concentric rings to determine the radial segment on which a radial cross-section lies. 
     
     
         17 . The method of  claim 11 , further comprising determining, from the image, another radial cross-section of another of the concentric rings having an intensity that matches the determined average red color value of the image of the unknown color sample and determining a second corrected average red color value of the unknown color sample using the polar angle of the another radial cross-section, and determining a final average red color value of the unknown color sample by calculating a weighted average of the corrected average red color value and the second corrected average red color value. 
     
     
         18 . A color identification system, comprising:
 a template comprising one or more gray scale continuums, wherein intensity along each continuum is a function of geometric position on the template;   an image obtaining device configured to obtain an image of an unknown color sample and the template; and   color identification modules configured to determine, for each of a red, a green, and a blue color value of the image of the unknown color sample, a corresponding geometric position on one or more of the gray scale continuums in the image where intensity of the gray scale continuum matches the color value, and to use the three determined geometric positions to determine the color of the unknown color sample.   
     
     
         19 . The method of  claim 15 , further comprising matching the determined color of the unknown color sample to one or more of a plurality of paint colors stored in a database.