Patent ID: 7600844
Filing Date: 2009-10-13
Classification: B41J

Abstract:
1. An ink jet printer, comprising: a printing unit having a carriage and a print head in which a plurality of ink jet nozzles are arranged in plural columns, the printing unit printing on a printing medium while reciprocating the print head by the carriage for go-printing and return-printing; a sensor disposed on the carriage and having a light-emitting portion for emitting light toward the printing medium and a light-receiving portion for receiving reflected light from the printing medium; a test pattern printing control unit that causes the printing unit to print a test pattern in which vertical ruled lines are arranged with a prescribed pitch; a plural patterns printing instructing unit that causes the printing unit to print a plurality of test patterns while changing a test pattern printing interval of the return-printing with respect to the go-printing in plural stages; a best pattern detecting unit for scanning-in the printed test patterns with the sensor and for automatically selecting a best test pattern from the scanned-in test patterns; and a best pattern printing instructing unit that causes the printing unit to print information indicating an image of the selected best test pattern on the printing medium, wherein the best pattern printing instructing unit causes the printing unit to reprint the selected best test pattern from the scanned-in test patterns on the printing medium at the test pattern printing interval that produces the selected best test pattern as information indicating the image of the selected best test pattern, wherein the best pattern detecting unit comprises: a sum-of-deviations calculating unit for calculating, for each of the test patterns, a sum of density deviations of a number of vertical ruled lines with respect to a density center value of the vertical ruled lines; and a pattern selecting unit for selecting the best test pattern from the scanned-in test patterns, the best test pattern having the minimum sum of density deviations calculated by the sum-of-deviations calculating unit.