Multi-pass calibration in fixed printhead array printers

A computer readable medium embodying programmed instructions which, when executed on a computing device of a printing system, perform a method of calibrating multiple fixed printheads operable in a multi-pass printing system to print a provided image on the printing system, the image comprising a plurality of pixels, each pixel associated with an input gray scale level, the method comprising:

• printing a plurality of printed patterns wherein each printed pattern is generated as a combination of each of the multiple fixed printheads (1 . . . j) operating in a multi-pass mode, wherein each of the multiple fixed printheads is using substantially the same ink, and wherein each of the multiple fixed printheads generates a gray scale pattern associated with a corresponding gray scale level for each of the plurality of printed patterns;
• measuring an intensity of each of the plurality printed patterns;
• determining a combined measurement function for the multiple fixed printheads operating in a multi-pass mode wherein the combined measurement function relates the measured intensities to the corresponding gray scale level of each printed pattern generated by each of the multiple printheads;
• determining a calibrated transfer function for each of the multiple fixed printheads based on the combined measurement function wherein each calibrated transfer function relates an input gray scale level of the image to a corresponding gray scale level used by a corresponding fixed printhead operating in multi-pass mode;
• and
• translating the input gray scale level of each pixel into a calibrated gray scale level for each of the multiple fixed printheads using the calibrated transfer function for each printhead;
• and
• printing the image on the printing system operating in the multi-pass mode using the calibrated gray scale level for each pixel of the image printed by each printhead.

A printing system adapted for multi-pass mode of operation using multiple printheads, the system comprising:

• multiple fixed printheads configured to sequentially apply ink to a printable substrate passing by the printheads;
• an intensity measurement device configured to measure an intensity of printed patterns generated by the multiple fixed printheads;
• and
• a multi-pass calibration controller coupled with the multiple fixed printheads and coupled with the intensity measurement device,
• the multi-pass calibration controller adapted to print a plurality of printed patterns wherein each printed pattern is generated as a combination of each of the multiple fixed printheads (1 . . . j) operating in a multi-pass mode, wherein each of the multiple fixed printheads is using substantially the same ink, and wherein each of the multiple fixed printheads generates a gray scale pattern associated with a corresponding gray scale level for each of the plurality of printed patterns, the calibration controller further adapted to measure the intensity of each of the plurality printed patterns, the calibration controller further adapted to determine a combined measurement function for the multiple fixed printheads operating in a multi-pass mode wherein the combined measurement function relates the measured intensities to the corresponding gray scale level of each printed pattern generated by each of the multiple printheads, the calibration controller further adapted to determine a calibrated transfer function for each of the multiple fixed printheads based on the combined measurement function wherein each calibrated transfer function relates an input gray scale level of the image to a corresponding gray scale level used by a corresponding fixed printhead operating in multi-pass mode,
• the printing system adapted to translate an input gray scale level of each pixel of a provided image into a calibrated gray scale level for each of the multiple fixed printheads using the calibrated transfer function for each printhead, and
• the printing system adapted to print the provided image on the printing system operating in the multi-pass mode using the calibrated gray scale level for each pixel of the image printed by each printhead.