Patent ID: 7980654
Filing Date: 2011-07-19
Classification: B41J

Abstract:
1. A method for calibrating print heads to account for signature error of an image reading sensor, the method comprising: providing a first test pattern having a series of bars, the bars having known centroid locations; reading each bar of the first test pattern using the image reading sensor; computing the centroid location of each bar pattern using the sensor; calculating the signature error for each pixel in the image reading sensor by comparing the sensor read centroid location to the corresponding known centroid location; creating a signature error look-up table containing the signature error for each pixel of the individual sensor at N pixel intervals; printing a second test pattern having a series of dashes, each dash extending over a plurality of pixels; determining a position of each dash in the test pattern using the image reading sensor to find a believed position of the print head; accessing the signature error look-up table to find the signature error of the image reading sensor for the pixels located within each dash; and correcting the position of the print head by subtracting the signature error of the sensor at each pixel location from the believed position of the print head.