Patent ID: 8147060

Claim:
An ink jet printing apparatus comprising: a conveyance system for conveying a print medium along a first direction; a first printing head in which a plurality of printing elements are arranged in a second direction different from the first direction; a second printing head in which a plurality of printing elements are arranged in the second direction, and provided at a downstream side with respect to the first printing head in the first direction; a third printing head in which a plurality of printing elements are arranged in the second direction, and provided at a downstream side with respect to the second printing head in the first direction; a first Doppler speedometer that acquires a moving speed of the print medium in a vicinity of the first printing head; a second Doppler speedometer that acquires a moving speed of the print medium in a vicinity of the second printing head; a third Doppler speedometer that acquires a moving speed of the print medium in a vicinity of the third printing head; and a control unit that controls driving timings of the first, the second, and the third printing heads, wherein the driving timing of the second printing head is adjusted based on a first signal generated by a difference in the moving speeds acquired by the first and the second Doppler speedometers, and the driving timing of the third printing head is adjusted based on a second signal generated by a difference in the moving speeds acquired by the second and the third Doppler speedometers, as well as the first signal.