Canon iR2020 Series Service Manual page 109

Contents
4.1 Construction ....................................................................................................................................................... 4-1
4.1.1 Specifications, Control Methods, and Functions......................................................................................... 4-1
4.1.2 Major Components ...................................................................................................................................... 4-1
4.1.3 Control System Configuration..................................................................................................................... 4-2
4.1.4 Reader Controller PCB................................................................................................................................ 4-2
4.2 Basic Sequence................................................................................................................................................... 4-3
4.2.1 Basic Sequence at Power-on ....................................................................................................................... 4-3
4.2.2 Basic Sequence after Depression of Start Key (Book mode, One Sheet of original) ................................. 4-4
4.2.3 Basic Sequence after Depression of Start Key (ADF Mode, One Sheet of Original)................................. 4-4
4.3 Various Control .................................................................................................................................................. 4-5
4.3.1 Controlling the Scanner Drive System ........................................................................................................ 4-5
4.3.1.1 Outline .................................................................................................................................................. 4-5
4.3.1.2 Reader Motor Control........................................................................................................................... 4-6
4.3.2 Contact Image Sensor (CIS)........................................................................................................................ 4-6
4.3.2.1 Outline .................................................................................................................................................. 4-6
4.3.2.2 Analog Control Performed by the CIS ................................................................................................. 4-7
4.3.3 Enlargement/Reduction ............................................................................................................................... 4-8
4.3.3.1 Magnification Change in Vertical Scan Direction ............................................................................... 4-8
4.3.3.2 Magnification Change in Horizontal Scan Direction ........................................................................... 4-8
4.3.4 Detecting the Size of Originals ................................................................................................................... 4-8
4.3.4.1 Outline .................................................................................................................................................. 4-8
4.3.4.2 Outline of Original Size Detection ....................................................................................................... 4-9
4.3.5 Dirt Sensor Control ................................................................................................................................... 4-10
4.3.5.1 Outline ................................................................................................................................................ 4-10
4.3.6 Image Processing....................................................................................................................................... 4-11
4.3.6.1 Outline ................................................................................................................................................ 4-11
4.3.6.2 CMOS Sensor Drive........................................................................................................................... 4-12
4.3.6.3 CMOS Sensor Output Gain Correction and Offset Correction .......................................................... 4-13
4.3.6.4 CMOS Sensor Output A/D Conversion ............................................................................................. 4-13
4.3.6.5 Shading Correction (Outline) ............................................................................................................ 4-13
4.3.6.6 Shading Adjustment ........................................................................................................................... 4-13
4.3.6.7 Shading Correction............................................................................................................................. 4-13
4.4 Parts Replacement Procedure........................................................................................................................... 4-14
4.4.1 Copyboard glass ........................................................................................................................................ 4-14
4.4.1.1 Removing the Copyboard glass.......................................................................................................... 4-14
4.4.1.2 Removing the ADF Reading Glass .................................................................................................... 4-14
4.4.2 Reader Controller PCB.............................................................................................................................. 4-14
4.4.2.1 Removing the Rear Cover .................................................................................................................. 4-14
4.4.2.2 Removing the Right Cover (Lower)................................................................................................... 4-14
4.4.2.3 Removing the Right Cover (Upper) ................................................................................................... 4-15
4.4.2.4 Removing the Left Cover (Rear)........................................................................................................ 4-15
4.4.2.5 Removing the Reader Rear Cover...................................................................................................... 4-15
4.4.2.6 Removing the Copyboard glass.......................................................................................................... 4-15
4.4.2.7 Removing the Reader Controller PCB ............................................................................................... 4-16
Contents