Notes On Four-Point Detection - Hitachi HT-4139-28 Troubleshooting Manual

Troubleshooting
A-2 N
otes on Four-point detection
This TWAIN driver detect four points from the scan image.
The area to distinguish the background and the sheet because the background becomes black in
our scanner is necessary.
To detect four points of the sheet, this TWAIN driver usually detects it from the black and white
image.( If it is a multilevel image, it makes it to binary.)
Therefore, the clear area (area that becomes white) is 3mm or more necessary for surroundings
of the sheet.
When the clear area can be secured around the sheet, this method is recommended.
Clear area
3mm
3mm
3mm 3mm
A-2