ISO/IEC 29158: DPM Standard Updates
Late in 2020, an updated version of the ISO 29158:2020 standard for DPM barcodes was published to replace the previous version released in 2011. Since a designated committee must meet to discuss, debate, and agree on all changes before a new version is released, changes do not happen very often. When they do, it is important to note and understand the changes in the latest revision.
The following is a summary of the key changes that will affect how your DPM verification results are read.
Moving to a continuous grading scale for most quality parameters requires a shift from 1.0 steps between grades to 0.1 steps. This allows codes that were previously toggling between two grades to produce a more stable result.
Below are examples of the previous 1.0 step grading scale (A) and the new 0.1 step grading scale (B).
New Grade Scale for Minimum Reflectance (MR)
An important aspect of the DPM grading method involves automatically brightening an image before conducting the verification process. However, the original brightness is important, and it is measured for a minimum value. In the previous version, Minimum Reflectance could only result in an “A” (4.0) or “F” (0) grade. If the symbol had lower than 5% brightness before the adjustment, it would fail. Now, MR can receive a grade between “A” and “F”. The new standard has expanded upon the grading scale, so that if a code has 5% brightness before the adjustment it will be a “C” (1.5) grade. If the brightness is higher, the grade will be as well; if the brightness is lower, the grade will reflect it.
• In the previous standard:
• MR Grade is A (4.0) if MR value > 5%
• MR Grade is F (0) if MR value is < 5%
• No continuous grading of MR
• In the new standard:
• A (4.0) grade whenever MR > 15%
• MR of 5% is the start of a C grade range (1.5)
Dot Connecting Algorithm for Dot Peen Codes
With the previous standard, grading is done two times (with 50% and 80% apertures)with or without the stick algorithm, reporting the higher of the two grades. The new standard now requires grading four times and reporting the highest grade. The four verifications are without the stick algorithm at 50% and 80% aperture and with the stick algorithm at 50 and 80% aperture.