LED Illumination
Eight product families covering every illumination geometry used in machine vision from ring and bar lights to coaxial, dark-field, dome, line, backlight and spot. Advanced Illumination, supplied and supported by Exaktera.
The right illumination geometry changes what the camera can see.
LED illumination is not a commodity item in machine vision. The geometry — the angle, direction and pattern of the light — determines whether a defect appears as a bright feature on a dark background or disappears entirely. A ring light reveals surface contamination. A coaxial light reveals scratches and surface flatness. A dark-field light reveals edges and texture. The same camera, the same lens and the same defect will produce a different inspection result depending on the illumination geometry chosen.
Advanced Illumination’s product range is built around this principle. Eight product families cover every geometry used in industrial machine vision, from high-angle on-axis illumination to low-angle dark-field and diffuse dome configurations. Wavelength selection adds a further variable — UV fluorescence for contamination, near-IR for penetrating surface coatings, visible for standard contrast applications.
Illumination selection guide
How do I choose between ring light and bar light illumination?
Ring lights provide even, on-axis illumination and are the default choice for inspecting objects with rotational symmetry — round parts, bottle caps, connectors, round components. The even illumination around the optical axis minimises directional shadows. Bar lights are better where the feature of interest has a preferred orientation — a weld seam, a printed label, an edge — because a single directional source creates stronger shadow contrast along that axis. For features that require illumination from a specific angle, two opposing bar lights at a controlled angle give more control than a ring light can.
When is coaxial illumination the right choice?
Coaxial illumination sends light directly down the optical axis using a beam splitter, so the light and the camera share exactly the same line of sight. This makes it the correct choice for inspecting highly specular (mirror-like) surfaces — polished metal, glass, wafers, mirror-finish plastics — where angled illumination would produce specular glare that masks the surface detail. Scratches, flatness variation and surface defects on a mirror surface appear as dark features against a bright background under coaxial illumination. It is also used for reading laser-marked codes on reflective substrates where ring light or bar light would wash out the contrast.
What applications require dark-field illumination?
Dark-field illumination uses a very low angle of incidence — the light strikes the surface at a grazing angle. Features that protrude from or break the surface (raised edges, scratches, particles, embossed text, surface texture) scatter light back toward the camera and appear bright against a dark background. Flat surface areas return the light away from the camera and appear dark. This makes dark-field the right choice for inspecting surface texture, embossed markings, edge detection and particle contamination on otherwise smooth surfaces. It is the illumination used where a defect is topological rather than a colour or reflectance difference.
Is UV illumination appropriate for my inspection requirement?
UV illumination (typically 365nm or 395nm) excites fluorescence in materials that are invisible under visible wavelengths — adhesives, certain lubricants, biological contamination, UV-reactive marking inks and some sealants. If your inspection needs to detect a substance rather than a surface feature, UV fluorescence should be considered. UV LEDs also provide strong contrast for inspecting certain polymers, resins and coatings that absorb UV differently from their substrate. Note that UV illumination requires a UV-transmitting lens and a camera sensitive at 365–400nm — standard machine vision lenses and sensors are often not optimised at UV wavelengths.
Our application engineers work through illumination geometry and wavelength selection with you — describe the inspection task and we will identify the right approach.