Ink jet printer

An ink jet printer that ejects ink to draw information on an object conveyed by a conveyor, the ink jet printer comprising:

• an ink tank that stores the ink;
• a nozzle configured to eject the ink supplied from the ink tank toward a drawing target object;
• a storage unit that stores drawing data specifying an ejection timing of the nozzle at each of a plurality of offset positions in a conveyance direction, the ejection timing corresponding to drawing information;
• an optical movement measurement sensor that receives light from the drawing target object and generates a measurement value related to movement of the drawing target object in the conveyance direction based on the received light;
• a drawing control unit that controls ink ejection from the nozzle based on a current offset position based on the measurement value generated by the optical movement measurement sensor, and the drawing data;
• an evaluation unit that evaluates, as reliability of measurement by the optical movement measurement sensor, at least one of contrast of the drawing target generated according to an amount of received light from the drawing target object and quality of a speckle pattern generated according to a characteristic of a surface shape of the drawing target object;
• and
• an abnormality processing unit that executes an abnormality process when the reliability evaluated by the evaluation unit does not satisfy a predetermined criterion.