Patent ID: 7318636

Claim:
A correction-pattern forming method for forming a correction pattern on a medium, comprising: a step of moving a nozzle row in which a plurality of nozzles for ejecting a liquid to form dots on a medium are arranged in a row; and a step of forming a correction pattern that has a difference in darkness in a moving direction of said nozzle row and that is for correcting a discrepancy between dot formation positions in said moving direction by causing at least two nozzles, among the plurality of nozzles, in said nozzle row to eject the liquid at a different timing for each nozzle, wherein said correction pattern has a checkered pattern that includes a plurality of black cells each having a plurality of dots; wherein a diameter of an incident spotlight of a sensor is larger than a length of said black cell and shorter than twice the length of said black cell in said moving direction; and wherein said diameter of said incident spotlight of said sensor is larger than twice the length of said black cell in a direction perpendicular to said moving direction.