Verification and legibility of 3D fonts

In times of artificial intelligence, AI-based image recognition and ChatGPT, reading fonts on products is no longer a challenge. At the end of a production chain, there is often an automated final inspection to check whether the product in question is correctly labeled. As the labels often contain safety-relevant information, the inspection requirements now go beyond mere reading, i.e. verifying the correct content: it must be ensured that the information is also clearly legible for a human. But when is a text legible? In other words: What are suitable criteria for verifying the legibility of a text?

The VeRe (Verification and Readbility) software developed by Fraunhofer IIS is a prototype software for the inspection of 3D lettering that verifies whether the correct 3D lettering is displayed on a product and whether it can be read by a person. Various 3D sensors, such as the TireChecker sensor system, can be used to record the 3D lettering.

Application examples include the reading of so-called DOT or TIN codes (Tire Identification Number) on tires (see video), the reading of embossed lettering on metal parts or the identification of nest numbers on injection-molded components.

The lettering to be checked is automatically detected and segmented in the 3D data by the VeRe software. The lettering can also lie on complex curved surfaces or in indentations, which are automatically detected and pre-processed by the software. The actual verification of the lettering then takes place. This involves checking whether a specified character string is present on the object to be checked and whether all characters are in the correct order.   

The VeRe software can also be used to evaluate the legibility of 3D text. It is evaluated using various key figures such as the 3-dimensional shape of the characters or the steepness of the character edges. Hard-to-recognize, "washed-out" 3D characters usually have flattened edges, which are recognized and characterized by the VeRe software. 

The TIN code is located on the sidewall of a tire and codes the manufacturer, tire size and date of manufacture, among other things. The marking has been prescribed by the US Department of Transportation (DOT) for the US market since 1980 and has become the global standard. The VeRe software can not only use the TIN code to ensure that the correct tire is fitted, but also evaluates its legibility for humans. This is of great importance for necessary recall actions or for evaluating the lifetime of a tire.