In shading adjustment, the machine measures the density of a white sheet of paper and the standard white plate, and stores the measurements in memory. The ma-

chine then computes these measurements for use as the target value for shading correction. Shading adjustment is executed at time of machine installation or scan-

ning lamp replacement, or when a change has occurred in the intensity of light over time.

Service Mode:

COPIER>FUNCTION>CCD>CCD-ADJ

5.3.6.7 Shading Correction

iR5065 / iR 5055 / iR5075 / / /

The machine executes shading correction for every scan of an original.

The machine shines the light of the scanning lamp against the standard white plate, and measures the light reflected by the plate; it then uses the analog image

processing block of the CCD/AP PCB to turn the measurements into digital data, which will be sent to the shading correction circuit of the reader controller PCB

in the form of a shading coefficient.

In the shading correction circuit, the shading coefficient is compared against the target value stored in memory, and the machine uses the differences as the shading

correction value.

The shading correction value is used to make up for the variation among individual pixels of the CCD occurring at each scan, thus evening out the image density

level.

CCD output

Target value

Measurement

Standard white plate

Characteristics after

correction

Characteristics before

correction

White

Original density

F-5-34