10
Section 3 - Positioning the Scanner
V520-LHA7127
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. Very 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
V520-LHA7127 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 scan-
ner at its focal distance rather than at the extremes of its depth-of-field.
Typical Reading Distance from Window
(Depth of Field)
Readable Bar Code Width
(Field-of-View)
The table above 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 postioned 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 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.
Density of Bar Code
Near Distance
Far Distance
15 mil
0.6 in.
2.3 in.
10 mil
0.8 in.
2.2 in.
6 mil
1.1 in.
1.8 in.
4 mil
1.3 in.
1.65 in.
Distance from Window
Max. Width
0.5 in.
2.0 in.
1.0 in.
2.7 in.
1.5 in.
3.4 in.
2.0 in.
3.9 in.
2.5 in.
4.5 in.
Summary of Contents for V520-LHA7127
Page 1: ...MANUAL USER Cat No Q07BAZ1 V520 LHA7127 Miniature High Speed CCD Fixed Position Scanner...
Page 2: ...V520 LHA7127 Miniature High Speed CCD Fixed Position Scanner User Manual...
Page 3: ...iv...
Page 9: ...x Application Precautions 3...
Page 25: ...16 Section 4 Configuring the Scanner V520 LHA7127...
Page 27: ...18 Section 5 Application Engineering Support V500 LPN5627 V500 LPR5627...
Page 29: ...20 Section 6 Scanner Servicing and Maintenance V520 LHA7127...
Page 69: ...60 Appendix B Dimensional Drawings V520 LHA7127...
Page 71: ...62 Appendix C Optical Performance Charts V520 LHA7127...
Page 75: ...66 Appendix D PLC Touchscreen Connection Examples V520 LHA7127...
