Method and apparatus for measuring color

Abstract

The invention relates to apparatus for measuring color, the apparatus comprising: an acquisition system including a video camera and processing means organized to respond to the signals delivered by the camera to determine the tristimulus values of the color of the object in a reference calorimetric system by using a transfer matrix to transform the calorimetric system associated with said acquisition system into the reference calorimetric system, and to determine a correction function Γ to correct the non-linearities of said acquisition system.

What is claimed is:  
     
         1 . A method of correcting the response of a display device having rasters of pixels, wherein, at a transition in the control level for pixels in the same raster line that gives rise to a variation of luminance at least between a pixel of said raster line and the pixel immediately following it, in the raster scanning direction, the control level of said immediately following pixel is selected as a function of the rate at which the luminance of pixels situated on the same raster line varies when the control level of said pixels varies.  
     
     
         2 . A method according to  claim 1 , wherein a correction function is determined for correcting the non-linearities of said display device by: displaying two zones having the same color but luminances that may be different, the color of one of said zones being obtained by juxtaposing pixels having different control levels, while the color of the other zone is obtained by a set of pixels all having the same control level; making the luminances of the two zones equal for an observer by acting on the pixel control levels of one of the zones; and from the values of the pixel control levels of each of said zones, deducing information for calculating said correction function for correcting the non-linearities of the display device.  
     
     
         3 . A method according to  claim 2 , wherein said zone made up of pixels having different control levels is rasterized.  
     
     
         4 . A method according to  claim 3 , wherein said rasterized zone includes raster lines in which every other raster line is black.  
     
     
         5 . A method according to  claim 3 , wherein said zone made up of pixels having different control levels includes alternating pixels in each raster line having a control level that is different from the control level of the preceding pixel in said raster line.