Picture Element (Dot Position) Correction - Gestetner B147 Service Manual

IMAGE PROCESSING

Picture Element (Dot Position) Correction

Picture element correction does two things.
1. Completion of the scan line correction process.
2. Correction if the CCD is not perpendicular to the light.
• The green CCD line is taken as a standard.
• Both ends of the red and blue lines are adjusted to match.
• Use SP 4-932-1 to 4-932-4 to change the vertical line correction level
( "3. Replacement and Adjustment – Image Adjustments").
Scan Line Correction
R, G, and B CCD lines are spaced 4 lines apart (8 lines total) when full size
magnification is used.
• Scan line correction synchronizes these signals by storing each line in memory.
• The difference between the R, G and B signals depends on the magnification
ratio.
• If this calculation does not result in an integer, the corrected data is set to the
closest integer, but further correction is needed (
Correction").
Image Separation
The machine separates the original image into text and photo (dot screen) areas.
Edge Separation
• Used to locate text and line diagrams
• Locates areas of strong contrast.
• Looks for continuity of black or colored pixels.
• Looks for continuity of white pixels around black or colored pixels.
• Only uses data from the green CCD.
Dot Screen Separation
• If white pixels are not detected around non-white pixels, it is a dot screen area.
Colored Text Separation
• Identifies whether the text area's pixels are black or color.
• Based on:
1) Differences among the RGB maximum signal levels.
2) Output levels of the RGB video signals.
B147/B149/B190
"Picture Element
6-28 SM