Real-time linefeed measurement of inkjet printer

An image forming apparatus to print an image on a print medium, the image forming apparatus comprising:

• a print head having a head sensor configured to sense information from the image printed on the print medium;
• one or more processors;
• and
• memory storing instructions that, when executed by the one or more processors, causes the image forming apparatus to perform operations including:
• printing a first swath of the image on the print medium by the print head,
• capturing, by the head sensor, a first target image from the printed first swath,
• comparing the first target image to a reference image for the first swath based upon the image,
• determining a head sensor position deviation based on a relative shift between the first target image and the reference image, wherein the head sensor position deviation shows a vertical shift between a position of the head sensor and a position of a predetermined section of the print head,
• repositioning the print head relative to the print medium on which the first swath is printed by at least one line feed distance in a feed direction which intersects the scan direction,
• capturing, by the head sensor, a second target image from the printed first swath,
• determining a line feed error based upon the second target image while compensating the head sensor position deviation, and
• printing a second swath of the image on the print medium while compensating the line feed error.

A printer to print an image on a print medium, the image forming apparatus comprising:

• a print head having a head sensor configured to sense information from the image printed on the print medium;
• one or more processors;
• and
• memory storing instructions that, when executed by the one or more processors, causes the printer to perform operations including:
• printing a first swath of the image on the print medium by the print head,
• capturing, by the head sensor, a first target image from the printed first swath,
• comparing the first target image to a reference image for the first swath based upon the image,
• determining a head sensor position deviation based on a relative shift between the first target image and the reference image, wherein the head sensor position deviation shows a vertical shift between a position of the head sensor and a position of a predetermined section of the print head,
• repositioning the print head relative to the print medium on which the first swath is printed by at least one line feed distance in a feed direction which intersects the scan direction,
• capturing, by the head sensor, a second target image from the printed first swath,
• determining a line feed error based upon the second target image while compensating the head sensor position deviation, and
• printing a second swath of the image on the print medium while compensating the line feed error.