One-pass filtering and infrared-visible light decorrelation to reduce noise and distortions

Abstract

A scanning device includes a scanning mechanism and a processing mechanism. The scanning mechanism scans an image fixed on a medium to generate a digital infrared representation of the image and a digital visible light representation of the image. The processing mechanism substantially reduces effects of noise and distortions within the digital visible light representation of the image in one pass. The processing mechanism at least decorrelates visible light aspects from the infrared representation of the image and employs a one-pass filter that uses both the infrared and the visible light representations of the image.

1 . A scanning device comprising:
 a scanning mechanism to scan an image fixed on a medium to generate a digital infrared representation of the image and a digital visible light representation of the image;   a processing mechanism to substantially reduce effects of noise and distortions within the digital visible light representation of the image in one pass,   the processing mechanism at least decorrelating visible light aspects from the infrared representation of the image and employing a one-pass filter that uses both the infrared and the visible light representations of the image.   
     
     
         2 . The scanning device of  claim 1  wherein the one pass filter is a credibility-weighted bilateral filter that uses both the infrared and the visible light representations of the image. 
     
     
         3 . The scanning device of  claim 1 , wherein the processing mechanism is to decorrelate the visible light aspects from the infrared representation of the image by:
 determining one or more parameters of a model mapping a color channel of the visible light representation to the infrared representation;   for each of a plurality of pixels of infrared representation of the scanned image,
 determining a value corresponding to crosstalk between the pixel within the infrared representation and a corresponding pixel within the visible light representation, based on the model; and, 
 subtracting the value determined from an original value of the pixel to decorrelate the visible light aspects from the infrared representation as to the pixel. 
   
     
     
         4 . The scanning device of  claim 1 , wherein the processing mechanism is to employ the credibility-weighted bilateral filter that uses both the infrared and the visible light representations of the image by:
 for each of a plurality of pixels of the visible light representation,
 determining a credibility value corresponding to a likelihood that a value of the pixel is valid in relation to the image and that the value does not correspond to distortions within the visible light representation of the image; 
 determining a new value for the pixel by using the bilateral filter, taking into account the credibility values determined for the pixels within the visible light representation. 
   
     
     
         5 . A method for decorrelating a digital visible light representation of an image from a digital infrared representation of the image, comprising:
 determining one or more parameters of a model mapping a color channel of the visible light representation to the infrared representation;   decorrelating the digital visible light representation from the digital infrared representation based on the model; and,   outputting the infrared representation of the image from which the visible light representation has been decorrelated.   
     
     
         6 . The method of  claim 5 , wherein decorrelating the digital visible light representation from the digital infrared representation based on the model comprises, for each of a plurality of pixels of infrared representation of the image,
 determining a value corresponding to crosstalk between the pixel within the infrared representation and a corresponding pixel within the visible light representation, based on the model; and,   subtracting the value determined from an original value of the pixel to decorrelate the visible light representation from the infrared representation as to the pixel.   
     
     
         7 . The method of  claim 5 , wherein the method is for decorrelating infrared light absorbed by cyan colorant within the image fixed on the medium from the digital infrared representation of the image, and
 wherein determining the parameters of the model mapping the color channel of the visible light representation to the infrared representation comprises determining the parameters of the model mapping a red color channel of the visible light representation to the infrared representation.   
     
     
         8 . The method of  claim 5 , further comprising:
 prior to determining the parameters of the model,
 converting the infrared representation to a logarithmic domain; 
 converting the visible light representation as to the color channel to the logarithmic domain; and, 
   subsequent to decorrelating the digital visible light representation from the digital infrared representation based on the model,
 converting the infrared representation from which the visible light representation has been decorrelated back from the logarithmic domain.