LED Illumination for Machine Vision

On this page, you will find a comprehensive product guide on LED lighting for machine vision, as well as a wide range of manufacturer-independent products. This allows you to benefit from one of the most comprehensive lighting portfolios in Europe and directly compare and select suitable solutions.

 

LED illuminations have become the universal standard for imaging applications. They offer an excellent price/performance ratio, unbeatable reliability and almost maintenance-free operation. They can be assembled in almost any shape and are available in many different colours (red, white, blue, green, IR, UV).

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When is LED lighting the optimal solution for your image processing needs?

LED lighting is now the most widely used light source in industrial image processing because it produces stable, targeted and reproducible lighting conditions, which are a basic requirement for achieving reliable results. It is particularly suitable for applications where specific features need to be made visible, such as edges, colours, surface textures or fine defects. Selecting the appropriate lighting techniques, such as incident light, transmitted light or dark-field lighting, enables even challenging materials or complex geometries to be clearly captured.
 

Unlike other types of lighting, LEDs offer a high degree of flexibility, with different designs for tight or large installation spaces, various wavelengths for optimised contrast and the ability to control light direction, intensity and colour precisely. This makes them the first choice for inspections, quality control, measurement tasks and high-speed processes, wherever reproducible image data and controlled light guidance are crucial.

Questions about LED lighting? We’d be happy to advise you!

Not sure which lighting is best suited to your needs? We can help with selection and integration, providing a quick, independent and practical service.

 

More than just LED lighting - we support your entire machine vision project.

 

From selecting the lighting and conducting tests to system integration, we support you through every phase of the project, ensuring that your image processing is reliable, stable and precisely tailored to your requirements.

 

Red ring light Machine Vision Illumination Red ring light Machine Vision Illumination

Selecting LED lighting by application (product guide) 

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.

1. Which LED lighting technique provides the right contrast? (incident light, transmitted light, dark field)

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 

2. Which LED design is best for your application?

The design determines how LEDs project their light onto the object – diffusely, focused, segmented or over a wide area.
Criteria such as beam angle, homogeneity, space requirements and light guidance, which can be combined in many configurations, help with the selection.

LED ring lights

Ring lights use several LED segments that emit light all round.
They provide uniform, low-shadow illumination, particularly with diffuse covers or segmented control.


Typical features:

  • variable light direction thanks to individually switchable LED sectors 
  • Good control of reflections on metal and plastic 
  • Available in a range of diameters – to suit camera distance and field of view

LED bar and line lights

Linear LED arrays produce a focused or diffuse line of light, often used for line-scan, web inspection, edge illumination, or linear backlighting.

Typical features: 

  • High intensity thanks to tightly focused optics 
  • perfect for web materials, edges or microstructural defects 
  • Available in various lengths and power ratings

LED panel lights

Panels consist of numerous LEDs behind diffusers and produce an extremely homogeneous illuminated surface.


Typical features:

  • ideal for transmitted light (sharp-edged silhouettes) 
  • Absolutely uniform illumination of large test areas 
  • Optionally available with various diffuser and intensity levels

LED spotlights

Spots concentrate LED light using lenses or collimators.


Typical features:

  • Very intense light spot with high contrast 
  • suitable for oblique lighting, narrowly defined areas or robotic applications 
  • flexibly adjustable beam angle (optical variants)

LED dome lighting

Dome lights create a diffuse light chamber, powered by LEDs arranged in a ring.


Typical features:

  • Low-reflection rendering of glossy surfaces 
  • Stable performance with uneven, curved or textured parts 
  • Uniform 360° ambient light

Coaxial LED lights

LEDs are introduced into the optical path via beam splitters, creating a flat, shadow-free bright-field effect.


Typical features:

  • Ideal for reflective, flat surfaces 
  • no lateral shadows or stray reflections 
  • very stable with fine structures and markings


Practical tip:

The best design is achieved by considering three factors:

  • How big is the object? → determines light size & geometry 
  • What effect should the light have? → diffuse, focused, segmented, flat 
  • How much space is available? → determines whether to use a panel, ring light or spot

3. Which LED wavelength produces the best image contrast? (UV, VIS, IR, SWIR)

The wavelength influences which material properties become visible and how strongly structures, colours or defects stand out. Different spectra produce different image effects – important for stable, reproducible inspection.


White light (VIS, 400–700 nm)

Suitable for applications where multiple colours or different materials are assessed simultaneously.

Contrast behaviour:

  • natural representation of coloured surfaces
  • good overall differentiation with mixed materials
  • suitable for colour camera sensors 

When is it useful? 

When colour information is required or the scene needs to be assessed without strong spectral emphasis.

 

Monochromatic colours (red, blue, green)

Narrow-band light specifically enhances certain contrasts, as only one spectral range is used.

Contrast behaviour:

  • can improve contrast and apparent sharpness by reducing chromatic aberration effects
  • emphasize wavelength-dependent reflectance
  • clear colour contrasts (e.g. blue brings out yellow tones particularly well)

When is this useful?
When markings, edges, printed images or laser engravings need to be emphasised

 

UV (365–400 nm)

UV light activates fluorescence and makes fine details visible that are barely discernible in the visible spectrum.

Effects:

  • Revealing adhesive residues, coatings, micro-cracks 
  • Highlighting of fluorescent materials 
  • High level of detail in fine structures 

When is this useful?
When surfaces are required to react or fluoresce, or when very fine defects need to be detected.


IR / NIR (700–1000 nm)

Infrared reduces visible colours and minimises the influence of colour information.

Contrast behaviour:

  • reflection behaviour can differ from the visible range, but still depends strongly on material, surface roughness, angle of incidence and polarisation 
  • Penetration of certain materials (e.g. labels, thin films) 
  • Stable in changing ambient light

When is it useful?
When colour or print information is undesirable or reflections interfere with evaluation.

 

SWIR (1000–1700 nm)

Reveals material properties that remain hidden in visible light.

Effects:

  • Detection of moisture, fill levels, differences in density and layers 
  • Analysis of internal structures
  • Can be combined with suitable sensors and filters to reduce the influence of visible ambient light 

When is it useful?
For demanding inspections in food, pharmaceutical, electronics or packaging applications.


Tip:

The most reliable way to determine the correct wavelength is to ask three questions:

  • Which feature needs to be visible? (Colour, structure, coating, defects)
  • Do reflections play a role? ((IR may reduce the influence of visible colour, while UV can reveal fluorescent responses)
  • What type of camera is being used? (Monochrome cameras are often preferred for maximum sensitivity and contrast, including with narrow-band light, while colour cameras are used when true colour information matters)

4. Continuous light or LED strobe? – The right operating mode for your speed

The choice of operating mode affects how stable moving or static scenes are captured. While continuous lighting provides constant illumination, strobe lighting enables extremely short, bright flashes – ideal for fast-moving action or short exposure times.


Continuous Lighting

The lighting remains on continuously at an adjustable intensity.
Suitable for applications without extreme movement or where continuous evaluation is required.


Contrast behaviour and effects:

  • Constant brightness for stationary or slowly moving objects 
  • Ideal for setups with a fixed exposure window 
  • Stable when used with line scan cameras or continuous inspection stations

When is it appropriate?
When the speed is moderate or the system requires continuous illumination (e.g. for ongoing process monitoring).

 

Strobe / Flash mode

In flash mode, short, very bright light pulses are generated that are perfectly synchronised with the camera exposure.

Effects:

  • High light output in an extremely short time 
  • ‘Freezing’ of fast movements due to reduced motion blur
  • significant intensity reserves at very short exposure times

When is this useful?

For fast conveyor belts, rotating parts, pick-and-place movements, or when high contrast is required despite short exposure times.


Synchronisation & control

Flash operation requires precise synchronisation between the lighting and the camera.

Modern lighting modules are often equipped with integrated electronics that:

  • Precisely controls pulse duration 
  • In some cases support short overdrive or peak-mode pulses within specified duty-cycle limits
  • Can process trigger signals directly from the camera

These functions help you to identify lighting systems that can be synchronised cleanly during the selection process.

 

Practical tip:

The operating mode is usually determined by three factors:

  • Subject movement: fast → strobe; slow/static → continuous light 
  • Exposure time required: very short → strobe
  • Available intensity: high reserves required? → Strobe with peak capability

Strobe is particularly worthwhile when movement and short exposures would produce insufficient contrast.

 

5. Homogeneity, light distribution & beam angle: What sets LED products apart

The quality of an image depends not only on technology, design and wavelength, but above all on how the light is distributed in the room. Homogeneity, beam angle and light distribution determine how stable and repeatable contrasts are.


Homogeneity – uniform light for reliable image data

Homogeneous illumination ensures that the entire field of view is uniformly bright – without hotspots, shadows or gradients in brightness.

Effects:

  • stable grey-scale gradients → improved interpretability
  • less sensitivity to object position 
  • reliable results in measurement and inspection processes 

When is this useful?

For large surfaces, backlit silhouettes, packaging, labels, blister packs or anywhere where uniform illumination is crucial.
Light distribution – diffuse, directional or segmented?
The way light is scattered or concentrated has a direct influence on contrast.


Diffuse 

  • Light is softly diffused. 
  • Fewer reflections and harsh shadows 
  • Ideal for glossy surfaces or irregular shapes 

Directional 

  • Light hits the object in a focused beam. 
  • High contrast for edges, engravings or micro-defects 
  • Perfect for oblique lighting setups and moving processes 

Segmented 

  • Individual lighting areas can be controlled separately.
  • Variable light direction without repositioning 
  • Ideal for objects with varying surfaces or shapes


Beam angle – focused or wide-angle?

The beam angle determines how widely the light spreads across the surface.

Narrow angles (focused)

  • Higher intensity over a small area 
  • Good for details, oblique lighting, short working distances
  • Advantageous for short exposure times

Wide angles (wide-angle)

  • Wide coverage, soft, even 
  • Good for even front-lit and backlit scenes 
  • Stable with changing object positions 

 

Contrast arises from the interplay of light characteristics and material behaviour.

Decision logic:

  • How strongly should the surface be emphasised?
    → directional light
  • How distracting are reflections?
    → diffuse light distribution
  • How large is the test area?
    → Wide beam angle or floodlight
  • How fine is the target feature?
    → narrow beam angle or focused geometry

6. How much space is available? LED designs for confined installation spaces

In many applications, it is not the type of lighting but the available installation space that determines which solutions are even viable. Particularly in retrofit projects, complex machine layouts or confined robotic cells, lighting must fit precisely into existing structures.

 

Compact spotlights – maximum intensity with minimum space requirements

Spots are ideal when only a few centimetres of space are available. Thanks to optics or collimators, they can generate high luminous intensity despite their small form factor.


Effects:

  • pinpoint lighting even at close working distances
  • a good choice for robotics applications, pick-and-place and gripper zones
  • Flexible mounting thanks to compact design

 

Narrow beam and line modules – ideal for edge lighting in confined machine areas

Linear modules are ideal when light needs to be incident from the side but there is little space for large area lights.

Effects:

  • High intensity along a narrow axis 
  • ideal for components that move or are only accessible from one direction
  • very well suited to edge-lit setups in confined spaces

 

Slim Panels – flat, homogeneous and easy to integrate

Ultra-flat surface modules enable homogeneous illumination without significantly altering the machine room.

Effects:

  • Large illuminated surface with low installation depth 
  • Perfect for backlighting scenarios in confined frame structures 
  • commonly used in packaging, electronics and pharmaceutical facilities

 

Compact ring light variants – circular light at close range


For applications with central camera alignment, small ring light diameters provide effective illumination directly along the optical axis.

Effects:

  • Uniform incident light from a short distance 
  • ideal for short working distances in inspection stations 
  • Space-saving for front mounting

 

Segmented designs for difficult installation angles

If the installation space is not only small but also irregular, modular or segmented units can adapt the light distribution without having to redesign the entire layout.


Effects:

  • Flexible arrangement of individual elements
  • Light guidance possible in tight angles or through small openings
  • Enables lighting even in the presence of mechanical obstacles


Practical tip: 

If installation space is limited, three questions can help with the initial selection:

  • How close can the lighting be placed to the object?
    → determines installation height and appearance
  • Which direction is actually accessible?
    → from the side, front, through openings, from above/below
  • How large is the required illuminated area?
    → influences panel size, beam angle or line length

7.  Smart LED functions: Do you require variable colours, sequences or controllers?

Modern lighting modules can do far more than just switch on and off. Colour changes, sequences, modular control or rapid triggering open up additional possibilities for precisely controlling contrast or solving various inspection tasks with a single lighting system.

 

Variable colours – one light for multiple tasks

Lighting with switchable colours (e.g. red/blue/green or white and infrared) can create a variety of contrasting effects.


Effects:

  • Highlighting different material characteristics without reconfiguration 
  • Colour or texture inspection in a single setup good choice for robotics applications, pick-and-place and gripper zones 
  • Quick switching for changing components 

When is this useful?
When testing multiple variants or material colours, or when switching between neutral and narrow-band lighting is required.

 

Sequences & multiple lighting – automatically control changing light conditions

Sequence controls allow multiple lighting conditions to be called up in a defined order and synchronised with the camera.


Effects:

  • Multiple image variants per part (e.g. incident light + oblique light) 
  • Reproducible inspection sequences
  • Advanced defect detection without mechanical movement

When is this useful?
When the same station needs to detect different defect patterns or components have complex geometries.

 

Controller & trigger logic – precise control for fast processes

External controllers or integrated controllers manage the regulation of intensity, pulse duration, sequences and multi-channel operation.

Results:

  • Exact synchronisation with camera trigger 
  • Control of multiple light channels from a single system 
  • Reproducible pulse intensities and exposure times 
  • Stable results even at high refresh rates

 

When is this useful?

When capturing high-speed lines, robotic processes, strobe applications or complex multi-channel setups.

 

Intensity control & dimming curves – fine-tuning for image quality

Many lighting systems allow you to adjust the brightness and light characteristics with precision.

Effects:

  • Fine-tuning of contrast for critical surfaces 
  • Adaptation to changing material batches
  • Reduction of overexposure or saturation

When is this useful?

When switching between different object states or when stable exposure is required despite changing materials. 

 

 

Practical Tip:

Smart functions are particularly worthwhile when:

  • multiple inspection tasks need to be covered in a single station
  • there are material variants or colour changes
  • multiple lighting conditions per part offer advantages
  • the system requires very high speed or precise trigger times

Next step: selecting the right products

 

Based on the above criteria, the range of lighting options can be narrowed down very specifically, according to factors such as light type, design, spectrum, beam angle and required functions.


Using the STEMMER IMAGING Product Finder, you can combine these parameters to quickly arrive at a selection that is precisely tailored to your application. If you would like an assessment or wish to compare several options, our experts will be happy to help you find the optimal solution.

 

Do you need help selecting the right LED lighting? Our experts are here to help! They will help you select LED lighting tailored to your camera, optics, installation space and specific inspection task.

Frequently asked questions about our LED lighting

What is the typical lifespan of LED lighting in machine vision applications?

As a rough guide, industrial LED lighting typically offers around 20,000 to 50,000 operating hours. The actual lifetime depends strongly on product design, thermal management and operating conditions, so the vendor’s rated lifetime should always be checked for the specific product and application. In strobe mode, thermal load can be lower in some setups, but lifetime still depends on pulse current, duty cycle and heat management.

Can I easily retrofit existing systems with LED lighting?

In many cases, yes. Compact spotlights, narrow line lights and slim panels are particularly well suited to retrofitting in situations with limited installation space. It is important to check the installation dimensions, the power supply/control, and the desired lighting effect. Our experts can assist you in replacing existing luminaires with suitable solutions.

How can I tell if a lighting solution is really suitable for my application?

Ideally, the lighting should be tested using the original components and the planned camera/optics combination. This can be achieved using laboratory set-ups, demo units or application support. This allows you to determine at an early stage whether the contrast, uniformity and speed are sufficient for the subsequent process.

Does ambient light play a role with LED lighting?

Yes. Strong extraneous light can reduce usable contrast or distort measurements. In such cases, higher intensities, strobe operation, suitable wavelengths (e.g. infrared) or shielding measures can help. If in doubt, consider the actual lighting conditions in the plant.

Which IP ratings are appropriate for LED lighting in industrial environments?

In clean laboratory environments, IP20 is often sufficient. However, in production lines involving dust, moisture or cleaning processes, higher protection ratings such as IP65 or IP67 should be selected. The decisive factor is whether the lighting is exposed to direct media (coolants/lubricants, water jets, cleaning chemicals). For harsh production environments, a splash-proof housing is recommended as a minimum.

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