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Web & Continuous Material Inspection

Line Scan Lighting for Film Wrinkle Inspection

To detect longitudinal wrinkles in high-speed film webs, align a focused line-scan light perpendicular to the defect axis at a 15°-30° grazing angle. This cross-directional geometry produces shadow-relief contrast that isolates topographical changes. Combining high-intensity cylindrical focusing with microsecond exposure rates achieves reliable defect capture at transport speeds exceeding 1,000 m/min.

View Line-Scan Lights Request Sample Testing & Evaluation
Catalog photograph of an opaque film surface beside the side-lit result
Left is the film surface. Right is the side-lit result from a LuxMV application sheet.
Selection references

Visual references for selection

These photographs show the shop or the catalog comparison. Send the part to match a series.

High-uniformity line scan lighting visual
Reference 01High-uniformity line-scan light setup for continuous web and film wrinkle inspection.Send the part or the images with this condition.

Selection considerations

Open the matching series, then send the part or the images.

What wavelength and angle combinations work best for film wrinkle detection?

**Cross-directional grazing illumination maximizes topographical shadow contrast.** 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.

Which application inputs determine line-scan lighting selection?

**Web transport speed and optical beam width strictly define the required illuminance.** Film type, coating, transparency, gloss, web tension, defect direction, and representative good/bad material dictate the geometry.

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.

How do web flutter and thermal output impact image stability?

**Active thermal management is mandatory for stable high-output line-scan intensity.** Contrast drift from film lot variations, coating changes, web flutter, or tension fluctuations must be monitored.

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.

How do you maintain focus on a vibrating web?

Expand the illumination optical beam width to tolerate minor web flutter. While a tightly focused cylindrical line provides maximum intensity, a wider beam ensures the target remains illuminated even during vertical tension fluctuations.

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.

Which line-scan geometries isolate specific web defects?

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

Continuous film defect lighting selection matrix
Defect TypeRecommended Line-Scan TechniqueImaging Principle
Longitudinal Wrinkles & CreasesCross-directional grazing angle line light with focused beamEnhances shadow-relief contrast across the wrinkle profile perpendicular to the motion axis.
Pinholes, Voids & Bubbles in Clear FilmHigh-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 WebDarkfield grazing line light (15° - 30°)Direct specular reflections bypass the lens; micro-scratches scatter light directly into the aperture.
Coating Non-uniformity & Thickness StreaksPolarized / Multi-spectral UV or NIR Line ScanIsolates birefringence and coating absorption variations from substrate reflection.