Patent ID: 7505173

Claim:
A method for gray balance calibration of a color output device, comprising: producing first output image with the device in response to an input signal from a test image, wherein the first test image includes at least one preselected color; measuring with a first sensor the image corresponding to the preselected color, said first sensor producing a first output indicating spectral color information for at least the preselected color; producing gray balance tone reproduction curves using measurements from at least one preselected color; producing a second output image with the device in response to a request, wherein the second test image includes at least one preselected color located at a plurality of spatial locations in the second test image; measuring with a second sensor the image at preselected spatial locations corresponding to the preselected color of the second output image, said second sensor producing a second output indicating reflectance information for at least the preselected color at the plurality of spatial locations; determining an error between the measured color of the one preselected color at a preselected pixel location and using the color information and the reflectance information at other pixel locations; adjusting the gray balance tone reproduction curves of the device to minimize the spatial uniformity errors at all pixel locations, thus calibrating the device color output spatially whereby the device expeditiously produces pleasing uniform color.