Printer and method of printing

A printer that prints an image on a printing medium while carrying out a main scan that moves a print head relative to the printing medium, said printer comprising:

• said print head that has a plurality of nozzles and a plurality of pressure generating elements, which respectively correspond to the plurality of nozzles, each of the pressure generating elements being driven in response to a driving signal, so as to cause an ink droplet to be ejected from the corresponding nozzle against the printing medium;
• a head driving control unit that generates the driving signal that selectively includes a first driving pulse and a second driving pulse in one printing period corresponding to one pixel in printing, a first driving pulse causing a first ink droplet to be ejected from each of the nozzles, a second driving pulse following the first driving pulse and causing a second ink droplet to be ejected from each of the nozzles, and outputs the driving signal to said print head, thereby causing said print head to print an image on the printing medium;
• and
• a platen gap specification unit that specifies a distance from a nozzle of interest to the printing medium, in order to cause three factors, that is, an ejecting speed of the first ink droplet towards the printing medium, an ejecting speed of the second ink droplet towards the printing medium, and a variation in time difference between the first driving pulse and the second driving pulse when the first driving pulse and the second driving pulse are respectively output to adjoining pixels in this sequence and in an inverted sequence, to satisfy a predetermined relationship, which depends upon the distance from the nozzle of interest to the printing medium, thereby causing a variation in distance between a hitting position of the first ink droplet and a hitting position of the second ink droplet when the first driving pulse and the second driving pulse are respectively output to the adjoining pixels in this sequence and in the inverted sequence to be within a preset value.

A method of printing an image on a printing medium while carrying out a main scan that moves a print head relative to the printing medium, wherein said print head has a plurality of nozzles and a plurality of pressure generating elements, which respectively correspond to the plurality of nozzles, each of the pressure generating elements being driven in response to a driving signal, so as to cause an ink droplet to be ejected from the corresponding nozzle against the printing medium, said method comprising the step of:

• (a) controlling the driving signal output to said print head and thereby causing said print head to print an image on the printing medium,
• wherein said step (a) comprises the steps of:
• (al) generating the driving signal that selectively includes a first driving pulse and a second driving pulse in one printing period corresponding to one pixel in printing, a first driving pulse causing a first ink droplet to be ejected from each of the nozzles, a second driving pulse following the first driving pulse and causing a second ink droplet to be ejected from each of the nozzles;
• and
• (a2) specifying the first driving pulse and the second driving pulse, in order to cause three factors, that is, an ejecting speed of the first ink droplet towards the printing medium, an ejecting speed of the second ink droplet towards the printing medium, and a variation in time difference between the first driving pulse and the second driving pulse when the first driving pulse and the second driving pulse are respectively output to adjoining pixels in this sequence and in an inverted sequence, to satisfy a predetermined relationship, which depends upon a distance from a nozzle of interest to the printing medium, thereby causing a variation in distance between a hitting position of the first ink droplet and a hitting position of the second ink droplet when the first driving pulse and the second driving pulse are respectively output to the adjoining pixels in this sequence and in the inverted sequence to be within a preset value.

A method of printing an image on a printing medium while carrying out a main scan that moves a print head relative to the printing medium, wherein said print head has a plurality of nozzles and a plurality of pressure generating elements, which respectively correspond to the plurality of nozzles, each of the pressure generating elements being driven in response to a driving signal, so as to cause an ink droplet to be ejected from the corresponding nozzle against the printing medium, said method comprising the steps of:

• (a) generating the driving signal that selectively includes a first driving pulse and a second driving pulse in one printing period corresponding to one pixel in printing, a first driving pulse causing a first ink droplet to be ejected from each of the nozzles, a second driving pulse following the first driving pulse and causing a second ink droplet to be ejected from each of the nozzles, and outputting the driving signal to said print head, thereby causing said print head to print an image on the printing medium;
• and
• (b) specifying a distance from a nozzle of interest to the printing medium, in order to cause three factors, that is, an ejecting speed of the first ink droplet towards the printing medium, an ejecting speed of the second ink droplet towards the printing medium, and a variation in time difference between the first driving pulse and the second driving pulse when the first driving pulse and the second driving pulse are respectively output to adjoining pixels in this sequence and in an inverted sequence, to satisfy a predetermined relationship, which depends upon the distance from the nozzle of interest to the printing medium, thereby causing a variation in distance between a hitting position of the first ink droplet and a hitting position of the second ink droplet when the first driving pulse and the second driving pulse are respectively output to the adjoining pixels in this sequence and in the inverted sequence to be within a preset value.