Selecting machine vision lighting starts by matching illumination geometry to the target surface behavior: specular, diffuse, or transparent. Identify the surface reflection response first, compare candidate geometries against the defect or feature that must be revealed, and verify exposure timing, working distance, and mounting clearance on real samples.
These photographs show the shop or the catalog comparison. Send the part to match a series.
Open the matching series, then send the part or the images.
The order is geometry, pattern, wavelength, then filters. For a scratch on metal, the geometry page states the failure of each setup: coaxial, dome, and low-angle. The method page is how to select machine vision lighting.
**First, establish the reflection property of the material to dictate lighting geometry.** To select machine vision lighting: (1) Identify surface reflection behavior—specular, diffuse, or transparent; (2) Match lighting geometry—low-angle bar for scratches, coaxial for planar mirrors; (3) Choose wavelength—monochrome red/blue for resolution, UV for fluorescent coatings; (4) Validate timing with strobe controllers.
**Selecting geometry based on physical material yields the highest optical contrast.** Polished Flat Metal (Aluminum/Steel): Use Coaxial or Polarized Bar Light. Curved Glossy Surfaces: Test dome or diffuse lighting to reduce hotspot glare. Subsurface / Silicon Wafers: Consider IR or SWIR. Moving Web / Continuous Film: Use High-Uniformity Line Scan Light.
| Material Type | Defect Type | Recommended Lighting | Expected Contrast Result |
|---|---|---|---|
| Flat Polished Metal | Scratches, Dents | Coaxial or Low-Angle Bar | High contrast on planar defects |
| Curved Glossy | Surface Flaws | Dome or Diffuse | Even illumination, no hotspots |
| Transparent/Glass | Edges, Profiling | Telecentric Backlight | Sharp silhouette, low diffraction |
| Continuous Web | Print Defects | Line Scan Light | Uniform high-lux exposure |
**Name the material and the feature before choosing a light.** Record the feature, such as a scratch, dent, edge, or hole, plus curvature, transparency, reflectivity, and finish. Set the field of view, working distance, and speed limits from that condition.
**Geometric alignment between light, target, and lens is the strongest determinant of feature visibility.** Ring lights suit general presence, bar lights give directional contrast for texture, coaxial lights emphasize planar reflections, and dome lights manage glossy glare. Backlights highlight silhouettes, while line-scan lights are optimized for web speed.
**Wavelength filtering isolates defects that have identical structural geometry but differing material absorption.** Visible color changes separate defect and background. UV/IR are useful when visible light cannot reveal contrast. Filters and polarizers can change the result as much as the light itself.
**Final checks use the actual trigger speed, working distance, camera, lens, exposure, and mounting geometry.** Record the images and the settings that were tested. Those records do not by themselves confirm every production defect.
Start with the inspection target, not the catalog category. Define the feature to reveal, the background to suppress, and the camera, lens, field of view, working distance, exposure, and speed constraints.
Match geometry to contrast: ring lights suit general front illumination, bar and low-angle lights emphasize directional texture, coaxial lights suit flat reflective targets, dome lights reduce glare, and line-scan lights support moving webs.
Test them when geometry alone cannot separate defect and background. Material absorption, reflection, coatings, oil, transparency, and glare can make wavelength and optical accessories decisive.
Curved glossy surfaces create intense specular reflections. Dome or diffuse lighting is necessary to eliminate these hotspots, whereas flat surfaces typically require coaxial lighting.
