Dental shade mapping

Abstract

A method and apparatus for obtaining a color mapping of a dental object. Illumination is directed toward the object over at least a first and second wavelength band, one band at a time. An image of the dental object is captured at each wavelength band to form a set of images of the dental object. For pixels in the captured set of images, an image data value for the pixel corresponds to each of the wavelength bands and calculates interpolated image data values proportional to the spectral reflectance of the dental object, according to the obtained image data values and according to image data values obtained from a reference object at the wavelength bands. Spectral distribution data for a viewing illuminant is obtained and the visual color of the dental object reconstructed according to the calculated interpolated image data values and the obtained spectral distribution of the viewing illuminant.

1 . A method for obtaining a color mapping for a dental object, the method, comprising:
 directing illumination toward the dental object over at least two wavelength bands, one wavelength band at a time;   capturing, on an imaging array, an image of the dental object at each of the at least two wavelength bands to form a set of images of the dental object;   for each of a plurality of pixels in the captured set of images:
 (i) obtaining an image data value for the pixel corresponding to each of the at least two wavelength bands; and 
 (ii) calculating a plurality of interpolated image data values proportional to the spectral reflectance of the dental object, according to the obtained image data values and according to image data values obtained from a reference object at the at least two wavelength bands; 
   obtaining spectral distribution data for a viewing illuminant;   reconstructing the visual color of the dental object according to the calculated interpolated image data values and the obtained spectral distribution of the viewing illuminant; and   storing, transmitting, or displaying at least the reconstructed visual color of the dental object.   
     
     
         2 . The method of  claim 1  wherein directing illumination comprises energizing one or more LEDs. 
     
     
         3 . The method of  claim 1  wherein calculating the plurality of interpolated image data values comprises determining a set of interpolation coefficients for the obtained image data values. 
     
     
         4 . The method of  claim 3  wherein calculating the plurality of interpolated image data values further comprises generating a reflectance curve as a function of wavelength from the set of interpolation coefficients. 
     
     
         5 . The method of  claim 3  further comprising calculating visual color values from the set of interpolation coefficients. 
     
     
         6 . The method of  claim 3  wherein calculating visual color values comprises computing a product of the set of interpolation coefficients and the obtained image data values. 
     
     
         7 . The method of  claim 4  further comprising calculating visual color values from the reflectance curve. 
     
     
         8 . The method of  claim 1  further comprising capturing, on the imaging array, an image of the reference at each of the at least two wavelength bands. 
     
     
         9 . The method of  claim 8  wherein the reference object is captured within the same image as that of the dental object. 
     
     
         10 . The method of  claim 8  wherein the reference object is captured as a separate image from that of the dental object. 
     
     
         11 . The method of  claim 8  wherein the reference object is a test patch associated with an intra-oral imaging device. 
     
     
         12 . The method of  claim 8  wherein the reference object is a test patch that is a standalone target. 
     
     
         13 . The method of  claim 8  wherein the image of the reference object is used to correct the set of image data values of the dental object. 
     
     
         14 . The method of  claim 1  wherein the imaging array is a color sensor array. 
     
     
         15 . The method of  claim 1  wherein the dental object is taken from the group consisting of a tooth, a color matching guide, a dental prosthesis, and a dental material. 
     
     
         16 . The method of  claim 1  wherein the visual color values are tristimulus values, CIELAB values, HSV values, or other equivalent values in a standard color space. 
     
     
         17 . The method of  claim 4  wherein the dental object is a first dental object and further comprising obtaining the reflectance curve for a second dental object and comparing the reflectance curve for the first and second dental objects in order to calculate a color match. 
     
     
         18 . The method of  claim 1  wherein the dental object is a first dental object and further comprising comparing reconstructed visual color with a second dental object to calculate a color match.