Exposure-energy-density and dynamic effect based uniformity correction for LED printheads

A printer apparatus comprising:

• a printhead that includes a plurality of contiguous recording elements arranged in a series of arrays wherein the plurality of contiguous recording elements in each array are generally uniformly spaced apart in the array at a nominal pitch distance and each recording element has a nominal size and a generally uniform brightness;
• a logic and control unit for determining variations in pitch, pixel size and power density for each recording element from the nominal pitch, pixel size and generally uniform brightness and generating a plurality of adjustment factors that are combined to determine an adjusted brightness for each recording element;
• a memory for storing a plurality of correction factors assigned to each recording element to correct for the adjusted brightness of each recording element on an image plane;
• and
• a plurality of current drivers for providing current to each recording element for an exposure time that is based on the corresponding correction factors for each recording element stored in memory,
• wherein the memory stores a dynamic vector configured to address a dynamic current starvation effect dependent upon a recording element exposure time relative to a rise and fall time of a light-output pulse from the printhead.

A printer apparatus comprising:

• a printhead that includes a plurality of contiguous recording elements arranged in a series of arrays wherein the plurality of contiguous recording elements in each array are generally uniformly spaced apart in the array;
• a logic and control unit for determining a variation from a nominal value for each of a plurality of parameters for each recording element and generating a plurality of adjustment factors that are logically combined for each recording element;
• a memory for storing a plurality of correction factors assigned to each recording element to correct for an effect of the combined plurality of adjustment factors on an image plane;
• and
• a plurality of drivers for modulating each recording element based on the corresponding correction factors for each recording element stored in memory,
• wherein the memory stores a dynamic vector configured to address a dynamic current starvation effect dependent upon a recording element exposure time relative to a rise and fall time of a light-output pulse from the printhead.

A method for calibrating a printer including a light-emitting diode (LED) printhead for non-uniformity on an image plane, wherein the LED recording elements are arranged in a plurality of arrays, the method comprising the steps:

• measuring a plurality of characteristics associated with each recording element;
• determining from the measured characteristics a plurality of parameters associated with each recording element;
• combining an adjustment factor for each of the plurality of parameters to determine an adjusted brightness for each recording element;
• assigning correction factors to each recording element to correct for the adjusted brightness for each recording element on the image plane;
• and storing the correction factors in a memory associated with the LED printhead,
• wherein the adjustment factors for a pitch and pixel size, and an exposure time for each recording element are used to determine a dynamic effective pixel brightness for each recording element, and
• wherein the dynamic effective brightness is a function of a targeted mean brightness for each recording element.

A method for calibrating a printer including a light-emitting diode (LED) printhead for non-uniformity on an image plane, wherein the LED recording elements are arranged in a plurality of arrays, the method comprising the steps:

• measuring a plurality of characteristics associated with each recording element;
• determining from the measured characteristics a plurality of parameters associated with each recording element;
• combining an adjustment factor for each of the plurality of parameters to determine an adjusted brightness for each recording element;
• assigning correction factors to each recording element to correct for the adjusted brightness for each recording element on the image plane;
• and storing the correction factors in a memory associated with the LED printhead,
• wherein the adjusted brightness compensates for a steady state current starvation measurement for each recording element, and
• wherein the steady current starvation measurement is determined by measuring the brightness with all recording elements on and subtracting the brightness with all recording elements on except for the recording element whose steady state starvation measurement is being determined.