What is 2D code verification?
2D code verification checks the image quality of 2D codes such as DataMatrix and QR code symbols.
Because use of 2D codes has spread to various industries, there are an increasing number of situations where codes are read in multiple places: automotive parts suppliers and car body manufacturers, pharmaceutical manufacturers and dispensing pharmacies, smartphone module manufacturers and assembly manufacturers.
Part and module manufacturers print 2D codes on key parts. Assembly manufacturers then read these 2D codes to acquire information such as product characteristics and serial numbers during manufacturing processes and quality assurance.
This means that unreadable 2D codes can seriously affect productivity.
Various image verification standards have been established as quantitative guides to address these situations.
Changes in 2D code verification
The history of 2D code image verification started in 2000 and the standards have been revised in response to changes.
* The following diagram shows the transition of image verification standards since 2000.
With the shift of printing targets from labels (paper) to materials such as metal and resin, new standards are being established.
Types of 2D code verification standards
This section introduces typical code quality verification standards.
A 2D code quality evaluation standard established by the International Organisation for Standardisation
This standard is mainly used for evaluation of 2D codes printed on labels.
ISO/IEC TR 29158 (AIM DPM-1-2006)
A 2D code quality evaluation standard for direct part marking (DPM) established by the Automatic Identification Manufacturers.
This standard was established based on ISO/IEC15415 and also standardised by International Organisation for Standardisation in 2011.
A code quality evaluation standard for DataMatrix codes used in the aerospace industry. This standard was established by the SAE (Society of Automotive Engineers).
A code quality evaluation standard for DataMatrix codes printed on semiconductor-related materials. This standard was established by SEMI (Semiconductor Equipment and Materials International).
Verification based on ISO/IEC TR 29158 (AIM DPM-1-2006)
ISO/IEC TR 29158 (AIM DPM-1-2006) is a 2D code quality verification standard designed for verifying the image quality of QR code symbols and DataMatrix symbols printed directly on products using direct part marking techniques (also known as DPM).
Direct part marking has drawn attention in industries such as aviation, automotive, electronic devices, and medical equipment to allow for product traceability. This has resulted in automatic identification codes being printed directly on products such as metal parts, metal molds, PCBs, plastic, and glass.
Among automatic identification codes, 2D codes are most often used to add a large amount of information in a limited space. Because they can contain more information than traditional 1D codes, 2D codes are used for maintaining product traceability as well as managing manufacturing processes by providing instructions or identifying parts.
As mentioned above, DPM 2D codes have grown in popularity, and are therefore more often read and used in various situations.
Because unreadable symbols have begun affecting manufacturing, some automotive manufacturers have started to control the image quality of 2D codes directly marked on parts they receive.
ISO/IEC TR 29158 (AIM DPM-1-2006), a DPM 2D code quality verification standard is used for this purpose. Employing this standard allows image specification management items to be shared comprehensively without spending time and effort reaching agreement on individual specifications.
Major differences in verification between ISO/IEC 15415 and ISO/IEC TR 29158 (AIM DPM-1-2006)
This section explains major differences in verification between ISO/IEC 15415 and ISO/IEC TR 29158 (AIM DPM-1-2006).
How the binary threshold is defined
Different methods are employed to define the threshold used to judge whether a cell is black or white.
Specifically, the following points are different.
ISO/IEC 15415 takes an intermediate value between the highest and lowest intensities in the symbol as the threshold value.
ISO/IEC TR29158 (AIM DPM-1-2006)
ISO/IEC TR 29158 (AIM DPM-1-2006) takes the intensity with the minimum total of dispersed intensities of black cells and white cells in the symbol as the threshold value.
The average intensity of black cells and that of white cells in the graph above are derived with a set threshold value and used for evaluation of cell contrast and the like.
|ISO/IEC 15415||Verification standard for 2D codes printed on labels|
|ISO/IEC TR 29158 (AIM DPM-1-2006)||Verification standard for 2D codes directly marked on products|