Correcting in-track errors in a linear printhead

A method for correcting in-track position errors in a digital printing system having a linear printhead, the linear printhead extending in a cross-track direction and including an array of light sources for exposing a photosensitive medium, comprising:

• a) providing digital image data for a test target including a plurality of alignment marks positioned at predefined cross-track positions;
• b) printing the test target using the digital printing system to provide a printed test target;
• c) using a digital image capture system to capture an image of the printed test target;
• d) using a data processing system to automatically analyze the captured image to determine a measured in-track position for each of the alignment marks;
• e) comparing the measured in-track positions for the alignment marks to reference in-track positions to determine measured in-track position errors;
• f) determining an in-track position correction function responsive to the measured in-track position errors, wherein the in-track position correction function specifies in-track position corrections to be applied as a function of cross-track position;
• g) storing a representation of the in-track position correction function in a digital memory;
• h) receiving digital image data for a digital image to be printed by the digital imaging system, wherein the digital image includes a plurality of image lines extending in the cross-track direction;
• and
• i) determining corrected image lines by resampling the digital image data responsive to the stored representation of the in-track position correction function;
• wherein the in-track position correction function is non-linear.

A method for correcting in-track position errors in a digital printing system having a linear printhead, the linear printhead extending in a cross-track direction and including an array of light sources for exposing a photosensitive medium, comprising:

• a) providing digital image data for a test target including a plurality of alignment marks positioned at predefined cross-track positions;
• b) printing the test target using the digital printing system to provide a printed test target;
• c) using a digital image capture system to capture an image of the printed test target;
• d) using a data processing system to automatically analyze the captured image to determine a measured in-track position for each of the alignment marks;
• e) comparing the measured in-track positions for the alignment marks to reference in-track positions to determine measured in-track position errors;
• f) determining an in-track position correction function responsive to the measured in-track position errors, wherein the in-track position correction function specifies in-track position corrections to be applied as a function of cross-track position;
• g) storing a representation of the in-track position correction function in a digital memory;
• h) receiving digital image data for a digital image to be printed by the digital imaging system, wherein the digital image includes a plurality of image lines extending in the cross-track direction;
• and
• i) determining corrected image lines by resampling the digital image data responsive to the stored representation of the in-track position correction function;
• wherein the in-track position correction function is quantized to integer in-track position corrections.