Patent ID: 6897466

Claim:
A liquid ejection apparatus comprising: a liquid ejection head, provided with a plurality of nozzle orifices each of which is communicated with a pressure chamber, and associated with an actuator which generates pressure fluctuations in liquid contained in the pressure chamber to eject a liquid droplet therefrom; a driver, which generates a drive signal to drive the actuator to eject a plurality of liquid droplets from each of the nozzle orifices; a carriages, which carries the liquid ejection head in a first direction; a first regions, at which the liquid ejection head ejects at least one of the liquid droplets with respect to a target member, a second region, adjacent to the first region in the first direction; a photo emitter, which emits a light beam so as to intersect a space through which at least another one of the liquid droplets passes, the photo emitter being disposed in the second region; a photo receiver, which receives the light beam which has been passed through the space, the photo receiver being disposed in the second region; and a calculator, which calculates an ejection velocity of the liquid droplet based on a timing at which the actuator is driven and a change in a photo-receiving state of the photo receiver, wherein: the nozzle orifices are arranged so as to form a plurality of nozzle arrays; the light beam diagonally intersects the space relative to the first direction, so as to oppose to plural of the nozzle orifices in plural of the nozzle arrays simultaneously; the nozzle orifices are divided into a plurality of groups so that nozzle orifices belonging to the same group are subjected to the ejection velocity calculation during a single scanning operation of the carriage in the first direction; and the nozzle orifices simultaneously opposing to the light beam include only one nozzle orifice for each of the groups.