Absolute, In-Process Coating Thickness Measurement via Non-Nuclear and Non-Contact Ruggedized Optical Interference technology for Enhanced Process Control

Presented by Dominic Gallelli, Industrial Physics

In modern continuous coating operations, real-time knowledge of applied layer thickness is crucial for maintaining product quality, minimizing waste, and preventing downstream defects. This talk introduces a non-contact, non-destructive and non-destructive optical interference approach—often called Ruggedized Optical Interference (ROI)—for absolute thickness measurement of coatings and adhesives immediately after application. The measurement principle is straightforward: a beam of light is directed at the coated substrate and reflections from both the coating surface, and the underlying material interfere. By interpreting that interference signal, the method yields a direct thickness value that does not depend on assumptions about coating chemistry, density, or calibration to external standards. The presented technology is also non-nuclear – the industry faces growing challenges regarding the procurement of nuclear, high regulatory costs, and the administrative burden of nuclear gauges. This advanced technology offers a viable solution that directly addresses these obstacles. From an operator’s perspective, the key impacts are: o Immediate feedback: Thickness data is available right after coating, enabling adjustments (e.g., flow, speed, application settings) before large volumes are produced off-target. o Reduced defects and scrap: Early detection of thickness deviations helps prevent issues that might otherwise be discovered only after drying or in downstream inspection. o Consistency over run time: As process variables drift (e.g., temperature, viscosity, substrate variation), continuous measurement helps maintain uniformity beyond periodic spot checks. o Faster troubleshooting: When anomalies occur (e.g., coating starvation, finger-bar effects, flow surges), the thickness trace helps pinpoint the time and location of deviation. o Foundation for advanced control: Reliable in-line thickness data supports consideration of feedback or closed-loop control schemes to increase process stability. Representative data from industrial coating lines will be shown to illustrate repeatability, response to process changes, and correlations between in-process data and final product outcomes. The discussion emphasizes how operators and process engineers can incorporate thickness measurement into workflows to prevent common coating and optimize coating application processes.