2D Data Matrix TM codes are made up of two parts: the finder pattern that tells the reader the code orientation and array size, and the actual encoded data. If you’re getting no read or a marginal read, you may have an issue with one these read factors. It’s also worth noting that the quality (and price) of the reader can have a significant effect – particularly on small codes, and codes marked on shiny surfaces.
Here are the four important factors to consider for good code readability.
- Level of contrast – Difference in reflectance between marked and unmarked code cells.
- Print growth – Dimension ratio of unmarked cell to marked cell.
- Axial non-uniformity– Measure of how much the sampling point spacing differs from one axis to another.
- Quiet zone – Blank margin around the code.
If the code is unreadable, start by inspecting it under an optical microscope and assess these factors. A code verifier or a reader that can capture images to be loaded into verification software provides a very good method of mark correction.
If you’re interested in 2D codes, be sure to stay tuned for our next post, “Optimizing a Data Matrix™ code for Readability.” In the meantime, if you want to know more about the details of the verification standards, check out two white papers that Microscan, Inc. has prepared: