Lighting for visual inspection and quality control
Scratches, colour differences and shape defects become visible under different lighting conditions.
The defect being sought determines the useful light. Directional illumination can reveal small protrusions or scratches. Other tasks benefit more from diffuse components, uniform illumination or dependable colour rendering. One standard luminaire therefore cannot solve every inspection task.
Glossy and transparent materials need particular care. Reflections can hide defects or resemble a defect themselves. Viewing direction, distance, background and part position should form a repeatable procedure.
Trials with representative acceptable and defective parts are more informative than selection by lux or wattage alone. Involve the people doing the work and assess fatigue, shadows and distracting reflections during a typical task. If machine-vision cameras are involved, coordinate their optical requirements separately with the imaging specialist. Human inspection and camera inspection need not use the same arrangement.
What to clarify for your project
- Provide representative acceptable and defective parts.
- Define repeatable viewing and part positions.
- Coordinate human and camera inspection separately.
Remember: Test lighting against the actual features being inspected.