Method of calibrating print alignment error

A method of calibrating a print alignment error between a first printhead of a first ink cartridge and a second printhead of a second ink cartridge installed in an inkjet printer, the method comprising:

• printing a first preset test pattern using the first printhead and a second preset test pattern using the second printhead, on a paper according to an input correction signal, the first and second test patterns having first and second starting points and first and second end points, respectively;
• scanning the printed first and second test patterns;
• measuring positions of the first and second starting points and the first and second end points of the scanned first and second test patterns;
• calculating a horizontal print alignment error between the first and second printheads from the positions of the first and second starting points of the scanned first and second test patterns;
• calculating a vertical print alignment error between the first and second printheads from a first distance between the positions of the first starting and end points of the first test pattern and a second distance between the positions of the second starting and end points of the second test pattern;
• and
• calibrating the calculated horizontal and vertical print alignment errors,
• wherein the first and second test patterns each comprise a shape of a right triangle,
• wherein the first and second test patterns comprises a first triangle and a second triangle, respectively, and the operation of calculating the vertical print alignment error comprises:
• calculating a width W2_tri of the second triangle formed by the starting point and the end point by subtracting the starting point from the end point of the second test pattern by the second ink cartridge;
• calculating a height H2 of the second triangle using Equation 1 from the width W2_tri and a preset angle θ facing the width W2-tri of the second triangle
• H2=W2_tri/tan θ [Equation 1];
• calculating a width W1_tri of the first triangle formed by the starting point and the end point by subtracting the starting point from the end point of the first test pattern by the first ink cartridge;
• calculating a height H1 of the first triangle using Equation 2 from the width W1_tri and the preset angle θ facing the width W1-tri of the first triangle
• H1=W1_tri/tan θ [Equation 2];
• and
• calculating the vertical print alignment error by subtracting the height H1 of the first triangle from the height H2 of the second triangle.

A method of calibrating a print alignment error between a first printhead of a first ink cartridge and a second printhead of a second ink cartridge installed in an inkjet printer, the method comprising:

• printing a first preset test pattern using the first printhead and a second preset test pattern using the second printhead, on a paper according to an input correction signal, the first and second test patterns having first and second starting points and first and second end points, respectively;
• scanning the printed first and second test patterns;
• measuring positions of the first and second starting points and the first and second end points of the scanned first and second test patterns;
• calculating a horizontal print alignment error between the first and second printheads from the positions of the first and second starting points of the scanned first and second test patterns;
• calculating a vertical print alignment error between the first and second printheads from a first distance between the positions of the first starting and end points of the first test pattern and a second distance between the positions of the second starting and end points of the second test pattern;
• and
• calibrating the calculated horizontal and vertical print alignment errors,
• wherein the first and second test patterns each comprise a rectangle and a right triangle having the same height as the rectangle, and one side of the triangle having the same height as a vertical side of the rectangle is connected to the vertical side of the rectangle,
• wherein the operation of calculating the vertical print alignment error comprises:
• calculating a width W2_tri of a second triangle by subtracting the starting point and a preset width of the rectangle from the end point of the first test pattern by the second ink cartridge;
• calculating a height H2 of the second triangle using Equation 3 from the width W2_tri and a preset angle θ facing the width W2-tri of the second triangle
• H2=W2_tri/tan θ [Equation 3];
• calculating a width W1_tri of a first triangle by subtracting the starting point and a preset width of the rectangle from the end point of the first test pattern by the first ink cartridge;
• calculating a height H1 of the first triangle using Equation 4 from the width W1_tri and a preset angle θ facing the width W1-tri of the first triangle
• H1=W1_tri/tan θ [Equation 4];
• and
• calculating a vertical print alignment error by subtracting the height H1 of the first triangle from the height H2 of the second triangle.