Patent ID: 7510256

Claim:
An image formation apparatus, comprising: a rotatable drum; at least a first print head and a second print head, each disposed over a surface of the drum at different angular positions, so as to eject ink onto the surface of the drum from different angles; an encoder disk connected to an axial end of the drum that rotates with the drum; an encoder sensor positioned to detect a position of the encoder disk as the encoder disk rotates with the drum; a ink sensor positioned over the surface of the drum that detects a relative position of ink ejected on to the surface of the drum, as a function of a circumference of the drum, during a complete revolution of the drum; and an encoder corrector operably connected to the first print head, the second print head, the encoder disk, the encoder sensor and the ink sensor, wherein the encoder corrector receives signals from the ink sensor and the encoder sensor, respectively, and reduces stitch error by controlling a timing of ink ejection from the first and second print heads based on the received signals, and the stitch error is a sinusoidal error that varies over the circumference of the drum.