Ejection head, image forming apparatus and image forming method

An image forming apparatus, comprising:

• an ejection head having n (where n is an integer not less than 2) ejection aperture groups arranged in a sub-scanning direction, each of the groups including ejection aperture rows arranged at prescribed intervals in a main scanning direction, each of the ejection aperture rows including a plurality of ejection apertures aligned in an oblique direction with a prescribed angle θ (where 0°<θ<90°) with respect to the main scanning direction, wherein ejection apertures for a row in a first ejection aperture group are phase offset in the main scanning direction relative to ejection apertures in said row for a second ejection aperture group, such that along said main scanning direction, ejection apertures of the first ejection aperture group alternate with ejection apertures of the second ejection aperture group;
• and
• an ejection controller which controls the image forming apparatus to form a dot row in the main scanning direction on an ejection receiving medium in such a manner that, droplets are ejected from the ejection head so that when a droplet ejected from one of the ejection apertures lands on the ejection receiving medium, droplets that are, with the exception of on ends of the dot row, adjacent to the droplet ejected from the one of the ejection apertures have already been present on both sides of the droplet or have not been present on both sides of the droplet.