In industrial machine vision, the right lighting systems are crucial for achieving optimal contrast, process stability and, ultimately, image quality. However, given the wide variety of lighting techniques, designs and wavelengths, the following question quickly arises: Which LED lighting is best suited to my machine vision application?
This product guide will help you find the right solution, from choosing the lighting technology (incident light, transmitted light or dark field) and the optimal design, to selecting the appropriate spectrum. It also shows you how to use the STEMMER IMAGING Product Finder to narrow down your selection in just a few steps, even without prior knowledge.
The illumination technique you choose determines the level of contrast you can achieve. This is why it is the most important step when selecting LED lighting. Each technique produces a different image of the scene and thus offers different possibilities for analysis.
Incident light – the standard solution for structures, colours & markings
With incident light, the object is illuminated from the front. This clearly highlights surface features, printed images, colours and codes. Depending on the light distribution (diffuse, coaxial, focused), reflections can be suppressed or utilised in a targeted manner.
Ideal for: print inspection, colour inspection, barcode and data matrix recognition, structure inspection.
The appropriate illumination geometry, such as ring, spot or flood lighting, can easily be adapted to the size and surface of your component during the selection process.
Backlight – maximum contrast for edges & silhouettes
Backlighting produces a high-contrast light-dark image because the object appears as a dark silhouette against a homogeneous background. Perfect for tasks where the external shape is crucial.
Ideal for: contour analysis, measurement, presence detection, transparent or semi-transparent materials.
Backlights provide very uniform illumination for silhouette and edge-based tasks. Linear backlights can also be used for moving web inspection with line-scan cameras – important for precise measurement tasks.
Dark-field – visible micro-defects on glossy surfaces
With dark-field illumination, light strikes the object at a shallow angle. As a result, scratches, burrs, grooves, dust particles or engravings appear as bright lines or dots, whilst the rest of the surface remains dark.
Ideal for: metal, glass, films, polished or reflective surfaces.
Segmented designs or ring-shaped dark-field lights also enable highly targeted defect detection.
Typical decision criteria:
• Inspecting surfaces, colours or markings? →Incident light
• Evaluating edges, shapes or silhouettes? → Transmitted light
• Detect the finest defects on shiny materials? → Dark-field
• Not sure where to start? → Compare reflected light & transmitted light, supplement with dark field if necessary
