You say "I cannot compare that output string with a string constant". Why not? What happens? I notice that the image you posted looks like it contains the string "ABCDEFGHIJKLMNOPQRSTUVWXYZ<nl>1234567890<sp>/<sp>-<sp>;<sp>:<sp>." (where <nl> means "New Line", or a blank space, which can be represented in various ways, depending on the OS, and <sp> is a space), whereas the string in your code is "ABCDEFGHIJKLMNOPQRSTUVWXYZ<nl>1234567890/-;:.", with no spaces.
I'm not an expert on OCR (I defer to Hatef here), but if the OCR routines add in the spaces, these strings are definitely different, and the equality comparison will be "False". You might think about comparing character-by-character, or displaying the two strings in indicators (if they are in two lines, I'd split them into "Line1" and "Line 2", as you'll find it easier to put a single line from one over a single line from the other and easily spot the difference "by eye".
Are you very experienced with Image Processing and the tools in the LabVIEW Vision toolkit? They are not particularly well-documented, and not for the Faint of Heart or Beginner of LabVIEW (in my humble opinion).
Bob Schor
