Patent ID: 7561304

Claim:
A method of judging whether or not darkness of a foreign matter on a test pattern printed on a medium with predetermined darkness has been read, the method comprising: reading the darkness of the test pattern using a reading section; detecting a section in the test pattern for which an amount of deviation, from a predetermined reference value, of a readout value on the darkness of that section exceeds a predetermined darkness-deviation threshold which is a threshold adopted for the deviation in darkness; and judging whether or not the darkness of the foreign matter has been read based on a size of said section that has been detected, wherein the test pattern is divided up into row regions, each of the row regions being made up of a plurality of the unit regions that are arranged adjacent to one another in the movement direction of a nozzle, and the detection of said section is performed row-region-by-row-region, wherein the size of said section is obtained as an occupancy rate indicating a ratio of the size of said section with respect to a size of a row region that is targeted for the detection, and if the obtained occupancy rate is equal to or larger then a predetermined first occupancy-rate threshold which is a threshold adopted for the occupancy rate, then a judgment is made that the darkness of the foreign matter has been read, wherein when a total number of unit regions for which the readout values have been obtained in the row region that is targeted for the detection is defined as Fs, a number of the unit region in the targeted row region for which the amount of deviation, from the reference value, of the readout value of that unit region exceeds the darkness-deviation threshold is defined as Ft, and the occupancy rate is defined as R, the occupancy rate R is calculated according to the following equation: R=Ft/Fs.