Web & Continuous Material Inspection

Line Scan Lighting for Film Wrinkle Inspection

In continuous web, film, and roll-to-roll inspection, lighting geometry and optical synchronization determine defect visibility. Select a line-scan configuration by evaluating defect orientation, web speed, camera line rate, optical beam focus, working distance, and thermal heat dissipation on the production line.

View Line-Scan Lights Request Sample Testing & Evaluation

High-uniformity line scan lighting visual — High-uniformity line-scan light setup for continuous web and film wrinkle inspection.

Selection considerations

Selection follows the observable condition, the optical setup, and the production constraint.

Direct answer: match optical angle to defect direction

Wrinkles and scratches can disappear when their direction aligns with the illumination line; cross-directional grazing illumination reveals topography.

Technical considerations

Define scan width, exposure line rate, transport speed, working distance, camera sensitivity, and thermal limits together.
Use high-intensity focused line lights with cylindrical lenses when short exposure times (microseconds) are required at high web velocities.

Selection inputs for web inspection

Film type, coating, transparency, gloss, web tension, defect direction, and representative good/bad material.

Technical considerations

Camera line rate, sensor pixel size, transport speed, encoder trigger synchronization, and fixture envelope.
Illumination optical beam width: narrow focused line for high illuminance vs. wide line for vibration tolerance.

Production details and thermal management

Contrast drift from film lot variations, coating changes, web flutter, or tension fluctuations.

Technical considerations

Thermal dissipation: High-output line lights require adequate heatsinking or forced-air cooling in enclosed machine frames.
Strobe vs. continuous operation: continuous illumination with active thermal feedback provides stable line-scan intensity.

Questions for the engineering discussion.

Why can a wrinkle disappear in a line-scan image?

The illumination direction may align with the wrinkle axis, the grazing angle may be too steep to cast shadows, or web flutter may shift the focus plane. Compare cross-axis and multi-angle line illumination on moving material.

What information helps with a line-scan lighting discussion?

Provide film material, optical transmission/reflection characteristics, defect samples, scan width, camera line rate, web speed, exposure time, working distance, trigger method, and space or thermal limits.

Film & Web Defect vs. Line Scan Lighting Matrix

Optimize line-scan illumination geometry for distinct continuous roll defects:

Continuous film defect lighting selection matrix
Defect Type	Recommended Line-Scan Technique	Imaging Principle
Longitudinal Wrinkles & Creases	Cross-directional grazing angle line light with focused beam	Enhances shadow-relief contrast across the wrinkle profile perpendicular to the motion axis.
Pinholes, Voids & Bubbles in Clear Film	High-intensity collimated line backlight (transmission)	Defects scatter or block transmitted rays, creating sharp dark silhouettes on high-speed line cameras.
Surface Scratches & Streaks on Glossy Web	Darkfield grazing line light (15° - 30°)	Direct specular reflections bypass the lens; micro-scratches scatter light directly into the aperture.
Coating Non-uniformity & Thickness Streaks	Polarized / Multi-spectral UV or NIR Line Scan	Isolates birefringence and coating absorption variations from substrate reflection.