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How Do Barcode Scanners Work?
Even though barcodes have bars and spaces of different widths, barcode scanners do not decode the data based on measuring those different widths
How Do Barcode Scanners Work?
Scanners work on the basis of reflectivity—more precisely on reflective differences in the barcode
How Do Barcode Scanners Work?
Linear or 1D scanners find the edges* of the elements (bars and spaces) and determine wide and narrow differences through electronic timing.
*The “edges” are actually the transitions from light to dark and back to
light reflectance values
Reflective Differences
Reflective Difference is determined by bar color, background color, opacity, edge definition, reflectance or refractance properties and other factors.
Refractance is why the bare aluminum on a pop can works well as the dark reflectance or bar color in the barcode.
Reflective Differences
Linear or 1D barcodes must achieve at least a minimum amount of reflective difference between bars and spaces in order to be legible to a scanner.
Reflectance must be considered in 660nm red light—not white light. This is because early scanners used lasers that produce light in this part of the spectrum, and it has become the de facto industry standard.
Press Gain Degrades Reflectivity
Excessive press or bar gain steals space from bars—especially narrow bars. When this occurs, minimum reflective differences are degraded and symbol decoding is threatened.
Different scanners are notoriously varied in their sensitivity to reflective differences, and therefore cannot be used to reliably predict barcode performance.
Scanners are Not Verifiers
When a scanner fails to decode a barcode, it doesn’t tell you why.
When a scanner successfully decodes a barcode, it doesn’t tell you if or how close it was to failing.
We can help…
Barcode-Test LLC
•Independent ISO compliance testing services
•Barcode quality seminars and webinars
•Verification equipment sales and support
•Plain English assistance with verification reports
Barcode-Test LLC – www.barcode-test.com – 630-235-6077 – [email protected]
