Opticon LH2 Manuale Utente

Chapter 3

much shorter distance range than low density bar codes with larger bars.

The following chart in figure 3.1 shows the “typical” depth-of-field (closest to farthest

reading distances ) for the LH2 imagers. 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 imager at its focal distance rather

than at the extremes of its depth-of-field.

The chart also shows the field-of-view at various distances from the window. The field-

of-view is the maximum width that the imager 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.

Good design policy is to position the imager at its focal distance and at the center of the

field-of-view. Do not position it near the extremes of the reading range.