Variations in windshield glass form, lamination, layer thickness, and wedge angle may result in visible defects that appear as dimensional distortion or ghosting (duplication) of HUD virtual images when viewed through the glass. Requirements for HUD testing are based on industry-standard test parameters and formulas in addition to automaker-specified requirements that must be met by suppliers throughout the HUD ecosystem, from glass makers to projection system manufacturers.
Radiant Vision Systems, based in Redmond, Washington, produces their TrueTest™ automated visual inspection systems for measurement and control, ProMetric® imaging colorimeters and photometers, Source Imaging Goniometer® systems, lenses for view angle performance measurement, and a machine vision software tool library for production-level measurement and control. Their solutions incorporate test criteria per SAE J1757-2, as well as features developed around unique customer application requirements. Radiant’s systems are applied to test photometric qualities like luminance, chromaticity, and contrast, as well as dimensional checks for distortion.
Additionally, data from the ProMetric system is analyzed using Radiant’s TT-HUD™ software platform, a test suite and user interface developed specifically for automated visual inspection of automotive HUDs. TT-HUD provides all data-capture and analysis functions, including built-in calculations to measure the qualities of HUD projections based on standard formula. For example, a complete distortion evaluation for HUD glass inspection may require 10-20 calculations to evaluate all visual qualities to account for the range of potential deviations within the projected test image. The windshield acts as an optical component of the HUD system, so visual performance of HUDs is impacted by the characteristics of the glass itself beyond the performance of the image projection technology. Cameras, software, and efficient data management are key to optimize efficiency in terms of development time and complexity.
