In situ calibration of multiple printheads to reference ink targets

A method for calibrating ink ejectors in a plurality of printheads in an imaging device comprising:

• operating a plurality of printheads in the imaging device with a first plurality of electrical signals, each electrical signal in the first plurality of electrical signals operating only one printhead to eject ink drops onto an image receiving member to enable each printhead in the plurality of printheads to produce a portion of a first test pattern on the image receiving member;
• spreading the first test pattern on the image receiving member;
• identifying a first reflectance measurement of light for each printhead in the plurality of printheads with reference to the portion of the first test pattern produced by each printhead;
• identifying an average for the first reflectance measurements;
• identifying a difference between each first reflectance measurement and the average for the first reflectance measurements;
• and
• adjusting a first portion of each electrical signal in the first plurality of electrical signals used to operate each printhead in the plurality of printheads having an identified first reflectance measurement that is outside a predetermined range about the average of the first reflectance measurements;
• operating the plurality of printheads in the imaging device with a second plurality of electrical signals, each electrical signal in the second plurality of electrical signals operating only one printhead to eject ink drops onto the image receiving member to enable each printhead in the plurality of printheads to produce a portion of a second test pattern on the image receiving member;
• identifying a second reflectance measurement of light for each printhead in the plurality of printheads with reference to the portion of the second test pattern produced by each printhead;
• identifying an average for the second reflectance measurements made with reference to the second test pattern;
• identifying a difference between each second reflectance measurement and the average for the second reflectance measurements made with reference to the second test pattern;
• adjusting a second portion of each electrical signal in the second plurality of electrical signals used to operate each printhead in the plurality of printheads having an identified second reflectance measurement that is outside the predetermined range about the average of the second reflectance measurements;
• continuing to operate the plurality of printheads with the first plurality of electrical signals and the adjusted first portions of the electrical signals in the first plurality of electrical signals to generate the first test pattern, identifying first reflectance measurements for the printheads from the first test pattern, identifying the average for the first reflectance measurements identified with reference to the first test pattern, and adjusting the first portion of each electrical signal in the first plurality of electrical signals used to operate each printhead in the plurality of printheads having an identified first reflectance measurement that is outside the predetermined range about the average of the first reflectance measurements identified with reference to the first test pattern until the first reflectance measurement for each printhead in the plurality of printheads is within the predetermined range about the average of the first reflectance measurements identified with reference to the first test pattern;
• continuing to operate the plurality of printheads with the second plurality of electrical signals and the adjusted second portions of the electrical signals in the second plurality of electrical signals to generate the second test pattern, identifying second reflectance measurements for the printheads from the second test pattern, identifying the average for the second reflectance measurements identified with reference to the second test pattern, and adjusting the second portion of each electrical signal in the second plurality of electrical signals used to operate each printhead in the plurality of printheads having an identified second reflectance measurement that is outside the predetermined range about the average of the second reflectance measurements identified with reference to the second test pattern until the second reflectance measurement for each printhead in the plurality of printheads is within the predetermined range about the average of the second reflectance measurements identified with reference to the second test pattern;
• generating a firing signal for each printhead with reference to the adjusted first portion and the adjusted second portion for each respective printhead;
• storing the generated firing signals in a memory for operation of the plurality of printheads;
• identifying a third reflectance measurement for one printhead in the plurality of printheads used to produce the first test pattern, the third reflectance measurement corresponding to an optical density of the ink ejected by the one printhead to form a portion of the first test pattern;
• identifying a difference between the third reflectance measurement for the one printhead and a predetermined optical density for a predetermined area coverage percentage of a color of ink ejected by the one printhead for the first test pattern;
• adjusting the first portion and the second portion of the stored generated firing signals for the one printhead with reference to the identified difference in response to the identified difference exceeding a predetermined range about the predetermined optical density;
• adjusting the first portion and the second portion of the stored generated firing signals for the other printheads in the plurality of printheads with reference to adjusted first portion and the adjusted second portion of the firing signal for the one printhead;
• and
• storing the adjusted firing signal for the one printhead and the adjusted firing signals for the other printheads in the memory.