Method for setting up drive signal

A method for setting up a condition for a drive signal in a liquid ejection head that includes a plurality of linearly-arranged nozzles and driving elements provided for each of the nozzles, a liquid being ejected from the nozzles to a receiving medium when the drive signal is supplied to the driving elements, the method comprising:

• ejecting liquids from the nozzles by applying a first drive voltage, measuring ejection rates of the liquids, and obtaining a first average ejection rate of the liquid ejected from the nozzles;
• ejecting liquids from the nozzles by applying a second drive voltage different from the first drive voltage, measuring ejection rates of the liquids, and obtaining a second average ejection rate of the liquid ejected from the nozzles;
• calculating a reference drive voltage used for obtaining an average ejection rate at a reference ejection rate by using a relationship between the first drive voltage and the first average ejection rate and by using a relationship between the second drive voltage and the second average ejection rate, calculating a rate of change of the average ejection rate with respect to drive voltage as a correlation coefficient for a correction of the ejection rate using the drive voltage;
• supplying a first drive signal to the driving elements, ejecting the liquid from each nozzle, measuring a droplet formed by the ejected liquid, analyzing the measured data, and obtaining a first ejection rate of each nozzle;
• supplying a second drive signal to the driving elements, the second drive signal being different from the first drive signal, ejecting the liquid from each nozzle, measuring the droplet formed by the ejected liquid, analyzing the measured data, and obtaining a second ejection rate of each nozzle;
• calculating an average value or a median value of ejection rates of each nozzle using the first ejection rate and the second ejection rate;
• classifying the nozzles into a plurality of groups in accordance with the order of the average value or the median value of the ejection rates of each nozzle;
• calculating proper drive voltages that cause a statistical value of the ejection rates of one of the groups to correspond to the reference ejection rate on a group basis using the average value or the median value of the ejection rates of each nozzle, the correlation coefficient, and the reference drive voltage;
• and
• setting up one of the proper drive voltages corresponding to a group as a drive voltage to drive one of the nozzles.