Opticon NFT 2100 User Manual page 12

Manual No. 25-ULNFT2100-01; Mar, 2005
Scanner
(Field-of-View Specification Based Upon 69º Degree Sweep)
Distance from Front
of Case
Field of View
3) Avoiding Specular Reflection
Do not position the scanner at an angle that causes the LED light to be reflected directly back into the
scanner. This is called specular reflection. Too much reflected light can "blind" the scanner preventing a
good decode. For optimal performance we recommended pitching the scanner ±13º off the
perpendicular to the barcode label surface.
If the bar code label is located on a flat surface, specular reflectivity occurs in the region between ±10
degrees off perpendicular (See diagram). If the bar code label is located on a cylindrical surface, such as
a test tube, the angle of specular reflection is measured tangent to the curve. If the curved surface is
also moving, specular reflection may occur at some point along the movement. This is OK, as long as
there is sufficient regions on the test tube label where the label is out of the specular angle. The
following diagram indicates the region to avoid:
4) Quality Bar Code Labels
The quality of the bar code label can affect the scanning performance. Poor quality labels are more
difficult to decode and may result in non-reads or potential misreads. The bar code label should be
printed to specifications. This means that the bars are printed within spec, with the correct widths, no
ink spread, crisps edges and no voids. There should be a sufficient quiet zone on both end of the bar
code label. For best results, the paper or label stock should have a matte finish to diffuse light. The
print contrast signal (which is a comparison of the reflectance of the bars and the background stock)
should be as high as practical.
Readable Width or Field of View for the NFT 2100
Focal
1.0" Distance
1.4"
25.4mm 35.4mm
2.6 3.1"
66mm 80mm
α
Aviod this region
±30º
NFT 2100 CCD Fixed Mount Barcode
1.5 2.0"
38.1mm 50.8mm
3.3 4.0
83mm 101mm
α
±10º
2.5"
63.5mm
4.7
118mm
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