LED printbar aging compensation using I-V slope characteristics

A printer, comprising:

• a photoconductor;
• a plurality of individual LEDs adjacent said photoconductor, said individual LEDs for illuminating said photoconductor;
• a first current driver having a control input, said first current driver for applying a first drive current to a first LED of said plurality of individual LEDs, wherein said first drive current is controlled by said first control input;
• a second current driver for applying a second drive current to a second LED of said plurality of individual LEDs such that said second LED emits light with a resulting intensity;
• a correction memory for storing a correction value and an initial slope value, said correction memory for applying said correction value to said control input;
• a slope determining network for determining a subsequent slope of the forward voltage drop verses forward current characteristic of said first LED;
• and
• a correction algorithm network operatively connected to said slope determining network and to said correction memory, said correction algorithm network for updating said correction value stored in said memory network as a function of a difference between the initial slope value and the subsequent slope value;
• wherein said updated correction value causes said first LED to emit light at an intensity substantially equal to the intensity of the light emitted from said second LED.