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Scanning with the SD Scan Card 3E
The SD Scan Card 3E is based on miniature CMOS linear imaging
technology. This device is basically a camera that captures
rectangular digital images measuring about 1 degree high and
40 degrees wide. The imaging rate varies between about 20 and
40 images per second and automatically compensates for
ambient lighting conditions — the more ambient light, the more
images per second. It is inappropriate, however, to compare this
imaging rate to the rate of the sweeping beam of a laser scanner
because the CMOS image is affected by blurring, while the laser
technology is not. For this reason, it’s important to hold this
scanner still while scanning.
Adequate lighting of the target bar code is critical to scanning
with imaging technology. Unfortunately, providing auxiliary
lighting increases the size, energy consumption, control
complexity and cost of the scanning device. For these reasons,
the red light from the SDSC scanner is simply an aiming beam —
it does not add any auxiliary lighting to the target bar code. For
this reason, it’s important to provide adequate ambient lighting
to the target bar code while scanning with this scanner.
Like all cameras, the SD Scan Card 3E has a "focal length"
(minimum and maximum distance from the target) where the
image can be clearly captured. The focal length of the SDSC
scanner is rather small compared to that of laser scanners. For
best results while scanning “normal” sized bar codes such as the
UPC codes used on retail items, the SDSC scanner should be held
from about 4 to 7 inches (10 to 18 cm) from the target.
Tips for Maximizing SDSC 3E Scanner Performance:
1. Minimize movement during scanning — The SD Scan Card 3E
must be held reasonably steady on the target for a short
period of time while the camera focuses and captures a clear
image. The scanner typically requires only several milliseconds
to capture a clear image, no more than a quarter to a half of a
second.
2. Provide adequate ambient lighting
—The SDSC scanner, like
any camera, works much better when the target bar code is
well-lit.
3. Determine the optimum focal length
— The SDSC scanner has
a fairly small focal length, so it is helpful to experiment until
48 | APPENDIX E: SCANNING TIPS