Method of adjusting print uniformity

A method of adjusting print uniformity for a xerographic device having an LED printbar, the method comprising the following steps:

• a) printing a test pattern on a target media, wherein the test pattern includes a set of strips of multiple test pattern lines, wherein each test pattern line is in the process direction of the xerographic device, wherein each test pattern line is associated with an individual LED of the LED printbar, wherein each strip is in the cross-process direction of the xerographic device, and wherein each strip includes a repetitive sequence of a test pattern line and n blank lines;
• b) transferring the target media with the printed test pattern to a scanner;
• c) scanning the target media and detecting each printed test pattern line;
• d) communicating detected test pattern line information to a computer;
• e) determining a measured metric from the detected test pattern line information;
• f) calculating the difference between the measured metric and a target value;
• and
• g) if the absolute value of the difference exceeds a first predetermined threshold, adjusting the current supplied to the individual LED associated with the test pattern line to reduce the difference;
• wherein each of the strips of multiple test pattern lines in the test pattern printed in step a) include a set of random lines, wherein each random line is associated with an individual LED of the LED printbar, and wherein each random line is printed between and spaced from adjacent test pattern lines.

A method of adjusting print uniformity for a xerographic device having an LED printbar, the method comprising the following steps:

• a) printing a test pattern on a target media, wherein the test pattern includes a set of strips of multiple test pattern lines, wherein each test pattern line is in the process direction of the xerographic device, wherein each test pattern line is associated with an individual LED of the LED printbar, wherein each strip is in the cross-process direction of the xerographic device, and wherein each strip includes a repetitive sequence of a test pattern line and n blank lines;
• b) transferring the target media with the printed test pattern to a scanner;
• c) scanning the target media and detecting each printed test pattern line;
• d) communicating detected test pattern line information to a computer;
• e) determining a measured metric from the detected test pattern line information;
• ) calculating the difference between the measured metric and a target value;
• and
• g) if the absolute value of the difference exceeds a first predetermined threshold, adjusting the current supplied to the individual LED associated with the test pattern line to reduce the difference;
• wherein the measured metric is a line width metric.

A method of adjusting print uniformity for a xerographic device having an LED printbar, the method comprising the following steps:

• a) printing a first test pattern line, a second test pattern line, and a third test pattern line on a target media, wherein each test pattern line is in the process direction of the xerographic device, wherein the first test pattern line is associated with a first LED of the LED printbar and an adjacent second LED, wherein the second test pattern line is associated with the second LED and an adjacent third LED, wherein the third test pattern line is associated with the first, second, and third LEDs, and wherein each test pattern line is spaced from adjacent test pattern lines;
• b) transferring the target media with the printed first, second, and third test pattern lines to a scanner;
• c) scanning the target media and detecting the printed first, second, and third test pattern lines;
• d) communicating detected first test pattern line information, detected second test pattern line information, and detected third test pattern line information to a computer associated with control of current supplied to individual LEDs of the LED printbar,
• e) determining a first measured value for a measured metric from the detected first test pattern line information, a second measured value for the measured metric from the detected second test pattern line information, and a third measured value for the measured metric from the detected third test pattern line information;
• f) calculating the difference between the first measured value and a first target value;
• g) calculating the difference between the second measured value and a second target value;
• h) calculating the difference between the third measured value and a third target value;
• i) performing an algorithm to determine a fourth measured value, a fifth measured value, and a sixth measured value for the measured metric from the first measured value, second measured value, and third measured value, wherein the fourth measured value is associated with the first LED, the fifth measured value is associated with the second LED, and the sixth measured value is associated with the third LED;
• and
• j) comparing each of the fourth, fifth, and sixth measured values to a fourth target value and, if the absolute value of the difference in one or more of these comparisons exceeds a predetermined threshold, adjusting the current supplied to the one or more LEDs associated with the measured value exceeding the threshold to reduce the difference.

A xerographic device comprising:

• an LED printbar including a plurality of individual LEDs, wherein the LED printbar is associated with printing a test pattern on a target media to determine print uniformity for the xerographic device;
• a computer in communication with the LED printbar for controlling input currents to individual LEDs of the LED printbar;
• and
• a scanner device in communication with the computer for scanning the target media, detecting the printed test pattern on the target media, and communicating detected test pattern information to the computer;
• wherein the computer determines a measurements for lines associated with the test pattern, calculates the difference between the measurements and target values, and if the absolute value of the difference exceeds a predetermined threshold, adjusts the input current to the individual LED associated with the measurement by a fraction of the difference to partially reduce the difference.