Precision optical coatings as a challenge for medical technology

The performance of many medical devices depends on a layer that is a thousand times thinner than a human hair. Precision optical coatings determine the optical properties of endoscopes, surgical microscopes, and medical laser systems. Even the slightest variations in coating thickness or material composition can affect their performance. While the development of these coating systems has become well established over the years, their economical and reproducible high-volume manufacturing places far greater demands on production.

The individual layers have a thickness in the nanometer range and are applied with high precision. Even minimal deviations in layer thickness or material composition alter the reflection and transmission characteristics and, consequently, the function of the component. Today, specialized coating processes enable layer thickness accuracies of over 0.1%, making it possible to reproducibly manufacture even complex coating systems.

Medical technology places particularly demanding requirements on these coatings. Endoscopes require the highest possible light transmission, fluorescence systems rely on precisely defined wavelength ranges, and laser systems demand exceptional durability as well as specific reflective and filtering properties Modern coatings fulfill all of these functions, but their production requires precise process control. As optical components become more complex, the focus of innovation is shifting from individual materials to the manufacturing process as a whole.

One example is the Enhanced Optical Sputtering System (EOSS) developed by the Fraunhofer Institute for Surface Engineering and Thin Films (IST). The production system combines rotatable dual-tube cathodes (rotatable magnetrons) with novel metal/metal oxide composite targets, resulting in an exceptionally stable coating process. At the same time, the system enables both sides of an optical component to be coated simultaneously for the first time, significantly increasing productivity while maintaining high coating uniformity.

What makes the system noteworthy is not a single technological innovation, but rather the combination of several factors: high process stability, a low-particle system design, reproducible coating profiles, and a level of automation that enables the industrial production of complex optical coatings. According to Fraunhofer IST, coating uniformity is maintained over production periods that are up to ten times longer than with previous systems.

Quality management is evolving alongside manufacturing technology. Rather than inspecting only finished components, measurement technology is moving directly into the production process. Inline monitoring continuously captures process data, providing transparency into process conditions, equipment parameters, and overall process stability.

In the EOSS system, this task is handled by the software MOCCA+, which integrates process control, data acquisition, and analysis. Quality deviations can be detected early, and process parameters can be monitored precisely. This replaces downstream quality control with continuous process monitoring: production parameters are recorded and evaluated during the coating process, ensuring that stable process conditions are maintained throughout the entire production cycle. This principle reflects a broader trend in advanced manufacturing: rather than checking quality only on the finished component, it is ensured right in the process itself.

As data-driven models and AI-assisted process control continue to evolve, this approach is expected to become more widely adopted. Manufacturing equipment is consequently evolving from automated production systems into intelligent platforms capable of continuously monitoring and optimizing production processes.

The challenges associated with precision optical coatings are representative of many manufacturing processes in the medical device industry. As components become more complex and quality requirements continue to rise, automated process control, inline metrology, and data-driven control loops are becoming increasingly important. What is already being implemented today for optical components could become the benchmark for additional manufacturing processes across medical device production.