Shading Correction - Konica Minolta Bizhub 501 Service Manual

Theory of Operation Ver.2.0 Mar. 2009
22.1.1

Shading correction

This is the measure to obtain an even distribution from light of the CCD sensor. The following corrections are
made at the prescribed timing.
a. White correction
The output voltage of each pixel of the CCD sensor when the white reference plate is exposed to the exposure
lamp is stored as the maximum output of the pixel.
b. Black correction
The output voltage of each pixel of the CCD sensor when the exposure lamp is turned off is stored as the mini-
mum output of the pixel.
Conduct calculation to find out what step in this range falls on the image data read from the original based on
the difference between the black and white data for each pixel stored in the steps a. and b. above, and output
the results of the calculation in the 10 bits accuracy.
[1] AD conversion input
Voltage at which the read is made
[1]
+1.4
0V
Width in which the read is made
After shading correction
[2]
1024
0
Width in which the read is made
22. IMAGE PROCESSING
White
Black
White
Black
[2] Shading correction output
50gat2c091nb
91