AOH :: 2200.TXT|
Logitech document 2200: "Recognition Hints and Tips for Catchword"
Document Number 2200
Recognition Hints and Tips for Catchword
1. Always scan in line-art or black and white mode.
2. Selecting The Right Resolution:
Most magazines and textbooks should be scanned at 300 dpi. Use 400 dpi if
the text you are scanning is smaller than standard magazine size. For
normal sized text (8 to 15 points), 300 dpi is the best resolution. Use 200
dpi if you are scanning large blocks of headline-style type.
Text Size Scanner Resolution (DPI)
6 to 8 Points 400 DPI gives best results
9 to 15 Points 300 DPI gives best results
16 to 20 Points 200 DPI gives best results
3. Adjusting Contrast:
Contrast control (the relative amounts of black and white) is critical
in obtaining a good scan. If the text to be scanned is too faint and the
scanned image shows excessive broken characters, then recognition will
be poor due to the unrecognized characters. If the contrast is too dark,
the letters will run together, also creating poor recognition. In any
initial scanning of a new image, you will need to adjust the contrast. We
recommend beginning with the middle setting and then adjusting either way.
4. Scanning Straight:
When the actual scan is slanted, skewed, or jagged, the text will not
be recognized fully. Use a hard edge ruler or the edge of a book to help
scan straight. Or press the left index finger on the left edge of the
scanner window casing as your right hand is holding the scanner to scan.
This will balance the weight of pressure in scanning and help align the scan
direction straight down the material.
5. Scanning Speed:
For the best image quality, experiment with the scanning speed to
determine the best rate for your computer. You should be scanning at an
acceptable rate so the speed indicator light on the scanner head does
not flash. When you scan too fast the characters may look compressed, which
causes character size inconsistencies. Try to scan a bit slower than the
normal rate recommended by the scanner software, perhaps at about 1/2 to
1 inch per second. This way the system can receive and process all of the
incoming scanned data in time.
Make sure your scanning does not get too far ahead of the real-time
display. On slower machines the disk access speed cannot keep up the with
the rate of incoming data passed from the scanner to the machine channel.
Before you hit RETURN to activate Recognition, view the entire image to check
that all the data is captured to screen. When you have scanned too fast for
the system, you may notice the final image displayed will have loss of data,
i.e., certain chunks of paragraphs are missing. In this case, you will have
to rescan slower. Scanning too slowly will not affect the quality of the
As you become more and more familiar with the way Catchword works -
what it recognizes and what it doesn't - you will find your results increase
7. Full Page Scanning:
When attempting to scan a full page, scan the page in two strips with an
overlap of 3/4 to 1 inch. Scan both sides straight, at the same speed, and
make sure both strips begin and end at the same height on the page.
You also have the option of scanning horizontally and the appending the
strips together in a file.
Following are the most common reasons why an OCR program may misread text:
Unrecognizable fonts or characters. Omnifont technology recognizes standard
fonts by comparing text characters to features programmed into the software.
The software will not read characters which don't match programmed features.
It may also misread similar characters, for example 1 and l.
Original document quality directly affects accuracy. Letters which are faint,
touching or otherwise illegible may be read inaccurately. Newspapers, copies
and faxes are often poor originals.
Uneven or fast scanning, or pausing in mid-scan may result in skewed,
stretched or compressed text. Follow the tips above to avoid these causes
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