Inkjet head and ink jet printing apparatus using the head

1. An inkjet head which forms a first dot and a second dot each of which is formed through a plurality of ink droplets on a printing medium, comprising:

an ejection section configured to eject the plurality of ink droplets according to a plurality of times of operations of an actuator; and

a driving section configured to apply voltages to the actuator of the ejection section such that the ejection section ejects ink based on first printing data indicating a first number (M) of drop frames corresponding to the times that the ejection section ejects ink continuously and a first position flag designating a drop frame number (S 1 ) where ink starting to be ejected in the first printing data, wherein M and S 1 denote positive integers respectively and the first dot is formed within a drop frame range from S 1 to S 1 +M−1, and a second printing data indicating a second number of drop frames which is the same as the first number (M) of drop frames and corresponds to the times that the ejection section ejects ink continuously and a second position flag designating another drop frame number (S 2 ) different from the drop frame number (S 1 ) where ink starting to be ejected in the second printing data to form the second dot, total ink volume of which is different from total ink volume of the first dot,

wherein the another drop frame number (S 2 ) designated by the second position flag resides within the drop frame range.

2. The inkjet head according to claim 1 , wherein the driving section comprises:

a first storage section configured to store patterns of the voltages applied to the actuator;

a second storage section configured to store a plurality of timer sets;

a waveform generation section configured to select one of the plurality of timer sets that are stored in the second storage section and generate a waveform of a voltage applied to the actuator based on the selected timer set and the voltage pattern that is stored in the first storage section for the timing of each drop; and

a voltage applying section configured to apply a voltage to the actuator based on the waveform generated by the waveform generation section.

3. An ink jet printing apparatus which forms an image on a printing medium, comprising:

an inkjet head which forms a first dot and a second dot each of which is formed through a plurality of ink droplets on the printing medium including,

an ejection section configured to eject the plurality of ink droplets according to a plurality of times of operations of an actuator,

a driving section configured to apply voltages to the actuator of the ejection section such that the ejection section ejects ink based on first printing data indicating first number (M) of drop frames corresponding to the times that the ejection section ejects ink continuously and a first position flag designating a drop frame number (S 1 ) where ink starting to be ejected in the first printing data wherein M and S 1 denote positive integers respectively and a first dot is formed within a drop frame range from S 1 to S 1 +M−1, and second printing data indicating a second number of drop frames which is the same as the first number (M) of drop frames and corresponds to the times that the ejection section ejects ink continuously and a second position flag designating another drop frame number (S 2 ) different from the drop frame number (S 1 ) where ink starting to be ejected in the second printing data to form the second dot, total ink volume of which is different from total ink volume of the first dot,

wherein the another drop frame number (S 2 ) designated by the second position flag resides within the drop frame range; and

a conveyance section configured to convey a printing medium to positions where the inkjet head ejects ink.