Machine Vision Lighting: Diffuse, Direct or Structured – When to Use Each

In machine vision, the right lighting is just as important as the right camera, lens or filter. Lighting determines how surfaces, textures and edges appear to the imaging system – and ultimately how well the application performs. Three of the most common lighting approaches are diffuse, direct and structured. Each has its strengths, and selecting the right now depends on your inspection goals.  

Diffuse Lighting: Uniform Illumination, Minimal Glare

Diffuse lighting spreads light evenly across the surface of an object, minimizing shadows and glare. This makes it ideal for shiny, reflective or curved surfaces, where direct lighting might cause hot spots or uneven highlights.

• Best For: Glossy packaging or bottles; curved parts (pharmaceutical vials, automotive components); surfaces where you need uniform contrast

Expert Tip: CCS dome lights and diffuse ring lights are popular tools here, ensuring that the camera “sees” the object, not distracting reflections.

Direct Lighting: High Contrast, Sharp Edges

Direct lighting uses LEDs aimed straight at the target, producing crisp shadows and strong contrast. It’s a great choice when you want to emphasize edges, textures or defects.

• Best For: Surface defect detection (scratches, cracks, dents); edge positioning and alignment tasks; applications requiring sharp, high-contrast images

Expert Tip: Direct lighting is often used in combination with line scan cameras or for high-speed inspection where every detail matters.

Structured Lighting: Revealing 3D Shape & Texture

Structured lighting projects patterns (such as stripes, grids or dots) onto an object. By analyzing how the pattern deforms, the system can capture 3D shape, surface topography or height variations.

• Best For: 3D measurement and profiling; detecting dents, embossing, or raised features; applications where shape, not just appearance, is critical

Expert Tip: Structured lighting is a staple in advanced applications like electronics inspection, automotive parts analysis and semiconductor production.

The choice between diffuse, direct or structured lighting comes down to one question: What features of the object matter most? If you need to minimize glare and reflections, go with diffuse. If you need sharp contrast and edge clarity, use direct. If you need to analyze shape or 3D structure, structured lighting is the way to go.