TU Wien deploys in-line ellipsometer in R2R lines

Researchers at TU Wien University have deployed the first in-line imaging-ellipsometer for roll-to-roll production, using an Allied Vision EXO250ZU3 polarized camera to deliver real-time, full-area optical thickness measurement of functional coatings on moving foils at speeds exceeding 100m/min.

The system addresses a long-standing gap in roll-to-roll quality assurance, where process excursions such as viscosity shifts or temperature drift can propagate undetected across an entire roll before sampling-based inspection catches them. By measuring coating uniformity, thickness consistency and surface defects simultaneously and non-destructively across the full substrate width, it eliminates the blind spots inherent in conventional off-line metrology.

At its core is the EXO250ZU3, built on Sony's IMX250MZR CMOS sensor with 2448 x 2048 resolution, global shutter and a nanowire polarizer that captures all four polarization states in a single exposure at 75 frames per second. A fixed linear polarizer and user-selectable LED illumination across the 350-1100 nm spectral window allow the system to resolve spatially resolved thickness maps with minimal latency, frame by frame at line speed.

To overcome the challenge of collimating light across foil widths of several meters, TU Wien replaced conventional refractive optics with large-aperture Fresnel lenses, reducing cost and footprint while maintaining precise angle-of-incidence control. Measuring directly on a roll suppresses foil vibration, fixes the effective angle of incidence and redirects backside reflections away from the detector.

The system was validated on PEDOT layers on PET foil and battery electrolyte coatings on copper foil, delivering quantitative thickness maps in both cases. TU Wien plans further installations on roll-to-roll lines with foil widths of up to 2 m.