Changes in Barcode Verification
In the 35+ years that barcodes have been around in significant numbers, barcode verification has evolved and changed, right along with the barcodes themselves. In the earliest days, barcode verification was relatively unknown; some pioneers in the industry even believed that verification was unnecessary. Looking back, it is difficult to reconstruct their logic, but it probably had something to do with an overzealous belief in the inerrancy of technology.
Shortly after the appearance of barcodes on retail shelves, barcode problems also appeared, and the need for barcode verification was realized. Of course as barcodes appeared, so did scanners, so the whole environment familiar smell of something unfamiliar, like a new car but with a sense of urgency. The problem of barcodes that don’t work was not well anticipated, so the question of what to do about it wasn’t well considered. The answer was Traditional Verification: measure the width of the bars and spaces and, oh, incidentally the problem could also be low contrast, so measure reflectivity too.
Traditional barcode verification is based on bar and space width measurement
Traditional Verification provided the first “scientific” evaluation of barcode quality, and although it was not an utter failure, neither was it an utter success. Barcodes that passed the Traditional Verification tests were failing at retail point of sale; barcodes that failed the Traditional Verification tests worked fine.
Eventually it was understood that the failures of Traditional Verification were because bar and space measurement is not how barcode scanners work: scanners decode barcodes through reflectivity, or more accurately, through the reflective differences between bars and spaces. For barcode verification to accurately predict whether or not a barcode would work with a scanner, verification would have to “see” the barcode the way a scanner does, and from that realization came AIM X3.182-1990 verification which made its way through the development and qualification process to become the ISO 15416-2000 Barcode print quality test specification for linear barcodes.
ISO barcode verification is based on reflectivity
Interestingly and significantly, most barcode verification reports include grade reporting on both Traditional and ISO parameters, because both grading methods provide information which is relevant and useful for understanding how the barcode will (or will not) perform. For example, a modern linear verifier will report Average Bar Gain as a percentage of X dimension, which is not an ISO parameter. Knowing that a barcode has spread up to or beyond the Traditional Verification tolerance is very useful in understanding why the ISO parameter Modulation and Decodability have been impacted. It is also in knowing how to adjust the print process to improve those barcode verification parameters.
Quiet Zone is another Traditional Verification parameter which is not explicitly evaluated and graded in ISO 15416 barcode verification. An infringed quiet zone would be downgraded as a Decode error in ISO barcode verification and very difficult to interpret without referring to Traditional Verification results.
Barcode verification is more than print quality
One example of how barcode verification continues to evolve is in regards to industry applications, which specify not the print quality but rather the data structure within the barcode. For example the automotive industry has established the Automotive Industry Action Group to standardize how its trading partners must structure the barcode used to mark the components and materials used in building cars and trucks. The health and medical device industry currently has two standards, HIBCC used by some trading partners and GS1 Healthcare by others. Blood banks have yet another standard, and there are numerous others serving other industries.
It is possible that some of these standards will become so universally influential as to eventually be incorporated into the ISO specification. But one thing for sure: barcode verification standards and practices will continue to change as the use of barcodes continues to change.