Canon IR2800, IR3300, IR2200 manual Shading Correction, F03-301-01

CHAPTER 3 IMAGE PROCESSING SYSTEM

3 Digital Image Processing

3.1 Outline

Digital image processing is performed by the reader controller PCB, which has the fol- lowing major functions:

[1]Shading correction

[2]Auto density adjustment (AE)

Reader controller PCB
			Target	EEP-ROM
		CPU
			value
Gain/offset
				SRAM
correction data
				J409
		·Shading correction		Even-number
Analog	digital image			pixel
		·Auto density		digital image 8
image	signal
		correction (AE)
processing	8			signal
		·Serial/parallel
block				Odd-number 8
		conversion
				pixel
		F03-301-01

3.2 Shading Correction

3.2.1 Outline

The output of the CCD will not necessarily be uniform because of the following factors even if the density of the original in question is perfectly uniform:

1)The level of sensitivity of a CCD pixel differs from that of another.

2)The level of penetration of light differs between the center and the periphery of a lens.

3)The intensity of the scanning lamp differs between the middle and the ends of the lamp.

4)The scanning lamp is subject to deterioration.

Shading correction is executed to correct discrepancies in the output of the CCD, and it may be of either of the following two: shading adjustment used to determine a target level in service mode and shading correction executed when scanning each original.

To make up for the fluctuations in the intensity of light occurring at short intervals, edge area gain correction is also executed.

3-4 R COPYRIGHT © 2001 CANON INC. CANON iR2200/iR2800/iR3300 REV.0 MAR. 2001