Patent ID: 7206097

Claim:
A patch measurement device provided in a printing apparatus for measuring a color density of a patch in a control strip printed on paper by the printing apparatus, wherein, the control strip and a reference mark are printed on the paper, and printed-image data representing the control strip and the reference mark printed on the paper are generated through imaging by an imaging device provided in the printing apparatus, the patch measurement device comprising: an image data storage section for storing the printed-image data sent from the imaging device; a reference mark detection section for detecting the reference mark based on the printed-image data stored in the image data storage section, and generating position data of the reference mark; a position data storage section for storing the position data generated by the reference mark detection section; a reference mark position data comparison section for determining whether the current position data of the reference mark as detected by the reference mark detection section is valid or not by using the past position data stored in the position data storage section; and a color density measurement section for generating color density measurement data by measuring a color density of the patch based on the result of the determination by the reference mark position data comparison section.