Opticon NFT 1125, NFT 2135 manual Field-of-View Maximum Readable Bar Code Width

Manual No. 25-NFT1121-01

Series NFT-1121/2135 Mini CCD Fixed Position Scanners

Depth-of-Field

Just as with a camera, the scanner has a depth-of-field. It can read bar codes that are not precisely at the focal distance - maybe a little closer, or a little farther away. However, if the bar code label is positioned too far from the focal distance, the scanner may not be able to successfully decode it.

The depth-of-field varies based on the density of the bar code, i.e., the thickness of the bars. High density bar codes (which have very narrow bars) are readable over a much shorter distance range than low density bar codes with larger bars.

The following table shows the “typical” depth-of-field (closest to farthest reading distances) for the NFT- 1125/2135 Series scanners. The actual performance may differ slightly from unit to unit. Also, it is important to note that this data was measured under ideal conditions using high quality bar code labels. In a “real world” environment the conditions will not be as ideal. Therefore, the best practice is to position the scanner at its focal distance rather than at the extremes of its depth-of-field.

Typical Reading Distance

from Window Depth-of-Field

	1127		1126		2127		2126
	Front View		Side View		Front View		Side View
Bar Code	Min.	Max.	Min.	Max.	Min.	Max.	Min.	Max.
Density
13.0 mil	0.0 in	1.5 in	0.0 in	1.4 in	0.0 in	2.4 in	0.5 in	2.6 in
10.0 mil	0.0 in	1.1 in	0.0 in	1.1 in	0.2 in	1.9 in	0.6 in	2.1 in
7.5 mil	0.0 in	0.9 in	0.0 in	1.0 in	0.4 in	1.7 in	0.7 in	1.9 in
6.0 mil	0.0 in	0.8 in	0.2 in	0.9 in	0.6 in	1.6 in	0.8 in	1.8 in
5.0 mil	0.0 in	0.7 in	0.3 in	0.7 in	1.0 in	1.5 in	0.9 in	1.6 in

Readable Bar Code Width (Field-of-View)

The following table shows the field-of-view at various distances from the window. The field-of-view is the maximum width that the scanner is capable of reading. A bar code label positioned anywhere within this field- of-view can be decoded. The field-of-view is also a measure of the widest bar code label that can be read. Remember: the width of a bar code label includes not only the bars and spaces but also the required white space (quiet zone) on each end.

		Field-of-View
	(Maximum Readable Bar Code Width)
Distance	1127	2127	1126	2126
from Window	Front View	Front View	Side View	Side View
0.5 in	2.6 in	2.6 in	2.5 in	2.5 in
1.0 in	2.9 in	3.0 in	2.7 in	3.1 in
1.5 in	3.3 in	3.4 in	3.0 in	3.5 in
2.0 in	3.7 in	3.9 in	3.2 in	3.8 in
2.5 in		4.3 in		4.1 in

Good design policy is to position the scanner at its focal distance and at the center of the field-of-view. Do not position it near the extremes of the reading range.

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