Rockwell Automation 5370-OCR2 PAK - Manual (Page 61)

Chapter 5
Creating and Editing Fonts
5–26
If a printed character correlates with two or more taught patterns:
When a printed character correlates with two or more taught patterns, it is
because the printed character is similar to other characters in the font. If this
occurs, the following procedure should be followed:
1. Obtain a frozen image containing the character that is confused. If the
system is in run mode, exit run mode and enter setup mode.
2. Open the Toolset Edit panel and edit the OCR Tool.
3. Use the Threshold/Filter option to verify that the threshold is acceptable
for the image. If not, adjust the threshold so that the characters are well
separated from the background. If minor threshold adjustments are not
sufficient, it may be necessary to reduce the brightness variation of the
image.
4. Select the Character Size option, and verify that the character size is set
correctly for the characters. If not, adjust the character size (Refer to page
4–12 for a description of character size adjustment).
5. Select the Edit Font option and use the Test All option to determine
which taught characters correlate with the printed character. If there are
too many correlations displayed in the same location, you must Test each
potential confusion character individually.
6. Edit the taught character that is confused with the printed character.
7. Place the character teach box around the printed character in the image.
Use the arrow buttons to finely adjust the position so that the character is
aligned as well as possible with the taught pattern.
8. Observe the regions of the taught character pattern that are the same as
the printed character. Place more don’t-care pixels in these regions
because they do not contribute information to help distinguish the
characters. This will increase the relative significance of the areas that
are different.
9. Observe the regions of the taught character pattern that contain don’t-care
pixels, where the shapes of the original characters are different. Add
additional green or yellow pixels in these regions to reduce the percentage
that will match the confusion character.
10.Again use the Test option to determine the effect of the changes you have
made to the taught character pattern. The correlation percentage should
be reduced. Repeat steps 8 and 9 to reduce the correlation as much as
possible.