Opticon LMD 1135 user manual Avoiding Specular Reflection, Distance Max From Window Width

Manual No. 25-ULPNR102-01; Mar, 2005 LMD 1135 Laser Fixed Mount Scanner

Readable Bar Code Width LMD 1135

(Field-of-View Specification Based Upon 40 Degree Sweep)

Distance Max.

from Window Width

2.0”2.8”

4.0”4.2”

8.0”7.2”

12.0”10”

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. It is the distance from the left edge of the view to the right edge. 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 barcode at the midpoint of the scanner’s depth-of-field and at the center of the field-of-view. Do not position it near the extremes of the reading range.

2) Avoiding Specular Reflection

Do not position the scanner at an angle that causes the laser 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. The recommended location is + 13 degrees off the perpendicular for optimal performance.

If the bar code label is located on a flat surface, specular reflectivity occurs between 0 to 8 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, there may be more than one position causing specular reflection. The following diagram indicates the area to avoid:

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