Method and apparatus for controlling multiple light sources in a digital printer

Apparatus responsive to a digital file representative of a source image for producing variable density pixel images to form a composite image on a target surface, said apparatus comprising:

• an imaging head including an array of pixel generators each energizable to produce a variable density pixel image on a said target surface;
• a normalizing signal source for respectively supplying normalizing signal components to said plurality of pixel generators for normalizing the pixel images produced by said pixel generators on said target surface, each such normalizing signal component having a value related to the density of the pixel image to be produced;
• and
• an image signal source for supplying imaging signal components to said plurality of pixel generators for producing a pixel image pattern on said target surface representative of said source image.

A method of controlling an array of light sources each capable of producing a variable density pixel image on a target surface, said method including the steps of:

• selectively energizing said light sources to form a first test pattern image on said target surface;
• scanning said first test pattern image to determine the density of each pixel image in said first test pattern image;
• calculating first correction factors to normalize the pixel images in said first test pattern image;
• and
• applying said first correction factors to said light sources to produce a second test pattern image.