Thermal printer and method for correcting printing positions

A thermal printer, comprising:

• a conveyance unit configured to convey paper along a conveyance direction;
• a thermal head configured to perform printing on the paper at positions along a width direction of the paper intersecting the conveyance direction of the paper, the positions along the width direction being based on a print reference position;
• a sensor positioned at a sensor position in the width direction and configured to detect marks on the paper being conveyed by the conveyance unit;
• and
• a controller configured to:
• control the conveyance unit to convey a confirmation sheet along the conveyance direction;
• detect a position of a mark in a predetermined pattern on the confirmation sheet with the sensor, the detected position of the mark corresponding to the sensor position with respect to the print reference position;
• control the conveyance unit to convey a sheet, and control the thermal head to print a line on the sheet along the conveyance direction at the sensor position in the width direction;
• receive a corrected sensor position based on a measured distance of the line on the sheet to an edge of the sheet;
• and
• update the print reference position based on the received corrected sensor position.