Auto Density Adjustment (Ae); Outline; Abc Circuit - Canon Image Reader-A1 iR5000i Service Manual

3.3 Auto Density Adjustment (AE)

3.3.1 Outline

As in the case of a newspaper, some originals have a dark background. Auto density cor-
rection is executed to reproduce the information (text, graphics) of such originals by remov-
ing the background.
This adjustment is enabled in density auto mode or when text mode is selected and data is
processed by the ABC circuit.

3.3.2 ABC Circuit

A colored background is identified as being white by changing the height of the dynamic
range according to the chromatic level of the background as shown in the following figure
for the CCD output level (8bit) of digital image signals (A/D converted).
Surface of original
FFh (white)
Output level
00h (black)
COPYRIGHT © 2001 CANON INC.
White Background Original
A : dynamic range of white-background original.
B : dynamic range of colored-background original.
F03-303-01
2000 2000 2000 2000 CANON iR5000i/iR6000i REV.0 JUNE 2001
CHAPTER 3 IMAGE PROCESSING SYSTEM
Colored Original
A
B
FFh (white)
00h (black)
3-7 R