Patent ID: 6256111
Filing Date: 2001-07-03
Classification: G06K,H04N

Abstract:
A method of updating a calibration of a printer using a first calibration function l(i) and a second calibration function f(i), comprising the steps of:applying l(i) to printer grayscale commands i to generate modified printer grayscale commands, each printer grayscale command associated with a reference grayscale value;printing grayscale patches with the modified printer grayscale commands, each grayscale patch manifesting a grayscale value;measuring the grayscale values of the grayscale patches;deriving a first updated printer calibration function t(i) from the printer grayscale commands and the measured grayscale values, the function t(i) converting the printer grayscale commands to updated printer grayscale commands such that the measured grayscale value of the printed grayscale patches substantially matches the reference grayscale values of the associated grayscale value print command;deriving a second updated printer calibration function g(i) from the functions t(i), f(i), and l(i); andwherein N represents a number of possible grayscale values, and the step of deriving g(i) comprises the step of determining g(i) according to the relation:g(i)=t(j) such that j=arg[min(.vertline.f(i)-l(j).vertline. for j=0, 1, 2, N-1)].