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Shading Correction
The machine executes the shading correction for every scan made.
In this correction, the analog image process unit on CCD PCB digitalizes the LED light reflected by the standard white board. After the reflected light is digitalized, it is held in the shading correction circuit on main controller PCB as a shading coefficient.
Shading correction circuit compares the stored target value with the shading coefficient. The difference between the two will be held as the shading correction value for use in correcting variation among CCD pixels when scanning the original, thus evening out the density levels of the image.