Printhead having non-uniformity correction based on spatial energy profile data, a method for non-uniformity correction of a printhead, and an apparatus for measuring spatial energy profile data in a printhead

An apparatus for obtaining a spatial profile of exposure output power from an exposure element in a printhead comprising a plurality of exposure elements, the apparatus comprising:

• a sensor configured to obtain a positional output power measurement for said exposure elements corresponding to a portion of the exposure output power of the corresponding exposure element emitted at each one of a plurality of predefined positions;
• a translation apparatus for moving said sensor to each one of said plurality of predefined positions for said exposure element to thereby permit said sensor to obtain a sequence of said positional output power measurements for a corresponding one of said exposure elements;
• control logic programmed to accept said sequence of positional output power measurements from said sensor and to generate, for said exposure element, spatial profile characteristic information using said sequence of positional output power measurements;
• a memory operatively coupled to said control logic and storing the spatial profile characteristic information for said exposure elements;
• and
• wherein said memory is a read-only memory device.

A method for compensating for non-uniformity of exposure elements in a printhead comprising a plurality of exposure elements, wherein each said exposure element emits exposure energy over an exposure area, the method comprising:

• obtaining a sequence of output power measurements for said each of exposure elements, each said output power measurement in said sequence corresponding to a predetermined position within said exposure area;
• deriving a correction value based on said sequence of output power measurements;
• storing the correction value for each of said exposure elements;
• applying the correction values to control of said exposure elements;
• wherein said deriving step comprises determining a spot size value for said exposure element;
• and
• wherein said determining step comprises determining a maximum of the positional output power measurement for a corresponding exposure element and calculating a distance between two of the predefined spaced-apart positions at which positional output power measurements have approximately a predefined relationship to the maximum of the positional output power measurement for the exposure element.

A printhead assembly for imaging onto a medium, the printhead assembly comprising:

• a printhead having a plurality of exposure elements, each exposure element emitting exposure energy over an exposure area;
• a memory coupled to the printhead and containing a compensation value for each of at least some of said exposure elements, said compensation values being determined by obtaining a plurality of positional output power measurements corresponding to a set of predefined spaced-apart positions within said exposure area to determine a spatial characteristic of exposure energy emitted by the corresponding exposure element;
• wherein the spatial characteristic is a beam spot diameter of the energy calculated by determining a maximum of the positional output power measurement for a corresponding exposure element and calculating a distance between two of the predefined spaced-apart positions at which positional output power measurements have approximately a predefined relationship to the maximum of the positional output power measurement for the exposure element;
• and
• wherein said predefined relationship is where positional output power measurements are approximately one half of the maximum of the positional output power measurement for the exposure element.

A method for compensating for non-uniformity of exposure elements in a printhead comprising a plurality of exposure elements, wherein each said exposure element emits exposure energy over an exposure area, the method comprising:

• obtaining a sequence of output power measurements for said each of exposure elements, each said output power measurement in said sequence corresponding to a predetermined position within said exposure area;
• deriving a correction value based on said sequence of output power measurements;
• storing the correction value for each of said exposure elements;
• applying the correction values to control of said exposure elements;
• wherein said deriving step comprises determining a spot size value for said exposure element;
• and
• wherein said determining step comprises determining a maximum of the positional output power measurement for a corresponding exposure element and calculating a distance between two of the predefined spaced-apart positions at which positional output power measurements have approximately a predefined relationship to the maximum of the positional output power measurement for the exposure element.

A method for compensating for non-uniformity of exposure elements in a printhead comprising a plurality of exposure elements, wherein each said exposure element emits exposure energy over an exposure area, the method comprising:

• obtaining a sequence of output power measurements for said each of exposure elements, each said output power measurement in said sequence corresponding to a predetermined position within said exposure area;
• deriving a correction value based on said sequence of output power measurements;
• storing the correction value for each of said exposure elements;
• applying the correction values to control of said exposure elements;
• identifying a maximum output power measurement in said sequence of output power measurements;
• dividing said maximum output power measurement by two to obtain a half maximum output power measurement value;
• identifying, from said sequence of output power measurements, a rising-edge full-width reference value as the output power measurement, in that portion of said sequence of output power measurements that precedes said maximum output power measurement, nearest to said half maximum output power measurement value, and identifying a first full-width position as said predetermined position within said predefined pixel area that corresponds with said rising-edge full-width reference value;
• identifying, from said sequence of output power measurements, a falling-edge full-width reference value as the output power measurement, in that portion of said sequence of output power measurements that follows said maximum output power measurement, nearest to said half maximum output power measurement value, and identifying a second full-width position as said predetermined position within said predefined pixel area that corresponds with said falling-edge full-width reference value;
• and
• computing a linear distance between said second full-width position and said first full-width position.