Detection of non-firing printhead nozzles by optical scanning of a test pattern

A method of determining nozzle-out functionality in an inkjet printer having a plurality of different nozzle groups, each group firing a different color ink said method comprising:

• printing on a print medium a multipass test pattern from different nozzle groups, predetermined spaced apart portions of the test pattern being printed on generally adjacent pixels by different individual nozzles respectively;
• shielding the test pattern from ambient light;
• illuminating the test pattern with artificial light;
• and
• optically scanning across the portions of the test pattern during said shielding and illuminating steps to sense which portions have been printed satisfactorily by each of said different nozzles respectively in order to identify and locate any of said individual nozzles which are non-firing.

A printer for forming images on a printing medium;

• said printer comprising:
• multiple nozzles for forming images by firing inkdrops in a pixel grid on such printing medium;
• means in the printer for operating the nozzles to form on such printing medium a multipass test pattern comprising:
• a multiplicity spaced apart of test-pattern modules in an array,
• each module corresponding to and formed substantially exclusively by a single respective one of the multiple nozzles, and
• each module occupying a respective multiplicity of generally adjacent pixels in the pixel grid.

Apparatus for assessing nozzle ink ejection capability in an inkjet printer that has multiple nozzles and that prints in a pixel grid on a printing medium;

• said apparatus comprising:
• a printer carriage for passing the multiple nozzles across the printing medium;
• a test pattern formed on such printing medium by such printer carriage, said test pattern comprising:
• a multiplicity of test-pattern modules in an array,
• each module corresponding to and formed substantially exclusively by a single respective one of the multiple nozzles, and
• each module occupying a respective multiplicity of generally adjacent pixels in the pixel grid;
• and
• a system for assessing the test pattern.