Omron V440-F User Manual page 209

8 Advanced Settings
Grading ISO 15416
 Overview
This section outlines the grading implementation for ISO 15416 available in the reader firmware. Please
refer to the free AIM guide titled The Layman's Guide to ANSI, CEN, and ISO/IEC Linear Bar Code
Print Quality Documents or to the relevant ISO specification documents for additional detail related to
print quality.
 Supported Symbologies
• Code 128 / GS1-128
• UPC-A / UPC-E / EAN-13 / EAN-8
• Interleaved 2 of 5 / ITF-14
• Code 39
• Code 93
• Codabar
 Minimum Resolution
• 4.0 Pixels Per Element Element = Nominal X Dimension
Usage / Notes
 Illumination and ISO 15416 Grading
The accuracy and consistency of ISO 15416 grading depends greatly upon the illumination in the field
of view. ISO 15416 grading is evaluated by analyzing individual scan lines applied across the imaged
symbol. These scan lines generate a signal called the scan reflectance profile which is the basis of the
scan line grading methodology. This scan line grading methodology uses a fixed intensity threshold to
determine whether the signal state represents a bar or space. In addition, this threshold is used as a
reference for measuring the value for contrast, modulation, and defects. Simply reading a symbol with
the X-Mode decoder can be achieved over a wide range of illumination profiles, but accurately grading
a defect requires much tighter control of the environment. The level of accuracy required is not easily
perceived by the human eye. To illustrate how variation that appears subtle to the eye can have a large
impact on grading performance, consider the following image from a standard reader using internal
illumination. The scan reflectance profile for the two line scans shown in the image is displayed to the
right of the imaged symbols. The large symbol spanning the entire field of view shows dramatic
differences in intensity. The spaces in the center of the symbol are providing 50% higher signal
response then the quiet zones at either edge of the field of view. Similarly, the smaller symbol lower in
the field of view provides a much lower overall response throughout its region. Scenarios like this will
create low modulation scores and differences in defect scores depending on the physical location of the
defect. If the symbol is moved within the field of view, it will receive a different score. It is recommended
that external illumination is used and evaluated closely for response characteristics when performing
ISO 15416 grading.
Figure 1: Uneven Illumination
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V440-F C-Mount Code Reader User Manual