Illumination Selector
Find the right machine vision light in under a minute
Lighting decides more vision projects than any other component. Answer six questions about your part and the selector recommends a lighting geometry, an LED colour and the accessories that make it repeatable, using the same rules our applications engineers apply at the bench.
Every recommendation links to lights we hold in the range. Or skip straight to all 285 illuminators from Advanced Illumination and ProPhotonix.
The selector
Describe the inspection
Answer what you can. Recommendations update live and sharpen with every answer. Nothing is stored or sent anywhere.
1.What do you need to see?
2.What is the surface like?
3.How is the part presented?
4.Is the part moving at capture?
5.Any mounting constraints?
6.What is the ambient light like?
Your recommendations appear here
Start with question 1. Each answer you add makes the ranking sharper.
Why it matters
Contrast is created at the moment of capture
A vision system can only measure what the image contains. If the feature you care about does not contrast with its background when the shutter fires, no amount of software will reliably put it back. Algorithms amplify what the light gives them.
That is why experienced vision engineers spend their effort at the front of the chain. The right light turns a hard application into an easy one, and the wrong light turns an easy application into a support contract. It is also the cheapest place to win: a well chosen LED light typically costs a fraction of the engineering time spent compensating for a poor one.
Three decisions do most of the work, and the selector above walks you through them: where the light sits relative to the part and camera, how diffuse or directional it is, and what wavelength it emits.
The framework
Three decisions that set your image quality
1. Geometry
Where does the light sit relative to the part and the camera? Front light at a high angle shows surface appearance. Low angle light skims the surface and reveals relief. Light from behind produces a silhouette. Light folded onto the lens axis makes flat shiny areas glow.
2. Diffusion
Direct light gives strong shadows and sharp specular reflections, which is useful for texture and relief. Diffuse light wraps around curves and kills glare, which is what print, foil and mixed materials usually need. Most lighting problems on shiny parts are diffusion problems.
3. Wavelength
Colour is a contrast tool, not a preference. A feature lit with a similar colour appears bright, and lit with the opposite colour appears dark. Shorter wavelengths resolve finer detail, infrared passes through some materials, ultraviolet makes inks and adhesives fluoresce.
Technique explorer
The ten lighting geometries worth knowing
Every diagram shows the camera at the top, the part at the bottom, and where the light goes. These ten cover the vast majority of industrial inspection tasks.
Ring light
Use it for: everyday presence checks and evenly lit matte parts. Mounts around the lens, so one bracket carries camera and light.
Watch out: on shiny surfaces it reflects straight back as a hotspot. Move to diffuse or dark field light when glare appears.
In the range: RL208-050, RL113 and more ring lights
Bar light
Use it for: flexible directional light. Raked at a low angle it emphasises texture and relief, and bars pair well in twos and fours for larger areas.
Watch out: contrast swings sharply with angle. Fix the geometry mechanically before you validate the application.
In the range: AL295-075, AL150048 and more bar lights
Dark field
Use it for: scratches, dents, engraved and embossed marks, edge chips on glass. Light skims the surface, so only features that disturb it send light to the camera. Defects glow against black.
Watch out: needs a short working distance and suits reasonably flat parts.
In the range: DF196-050, DF241-25 and more dark field lights
Dome light
Use it for: curved and shiny parts, foil, mixed materials, print on crinkled surfaces. Light arrives from every direction at once, like a cloudy day, so hotspots disappear.
Watch out: bulky, must sit close to the part, and the camera hole can leave a dark spot on mirror finishes.
In the range: DL194, DL097 both dome lights
Flat dome
Use it for: dome quality light from a slim panel the camera looks through. Ideal for codes and print on foil, blisters and pouches where headroom is tight.
Watch out: lower intensity than a true dome, so confirm exposure at production line speed.
In the range: FD2-0404, FD2-0808 and more diffuse panels
Coaxial (DOAL)
Use it for: flat polished metal, coated surfaces, solder joints and foil seals. A beam splitter folds the light onto the lens axis, so flat areas return light and tilted defects go dark.
Watch out: only flat specular surfaces benefit, and the splitter costs you light.
In the range: DL225-025, SL223S and more coaxial lights
Diffuse backlight
Use it for: silhouettes. Presence, orientation, fill level in translucent containers, and measurement where the outline is what matters.
Watch out: hides all surface detail. Add a front light on a second capture if you need the face as well.
In the range: BT100100, BL2-0404 and more backlights
Collimated backlight
Use it for: precision gauging and clear material inspection. Parallel rays give the sharpest possible edge, especially paired with a telecentric lens.
Watch out: alignment is critical and panels cost more than diffuse equivalents.
Collimated panels are built to order. Start from the backlight range and we will spec the collimation with you.
Line light
Use it for: continuous webs of paper, film, textile, glass and print, imaged with a line scan camera one row at a time as the material moves.
Watch out: needs encoder synchronised acquisition and very high, very uniform intensity along its length.
In the range: Cobra MultiSpec, LL163-018 and more line lights
Structured light and 3D
Use it for: height, flatness, volume and shape. Projected laser lines or patterns deform over the part, and triangulation turns that deformation into 3D data.
Watch out: a system decision, not a lamp swap. Laser triangulation and Photoneo structured light both live here. Other 3D technologies such as Time of Flight and Stereo Vision may also be more suitable.
In the range: SL256 pattern projector, plus laser modules and 3D cameras.
Interactive
Pick the LED colour with the contrast simulator
Monochrome cameras see brightness, not colour, so the LED colour decides how bright each material appears. Choose the colour of the feature you need to see and the colour of its background, and see how each common LED separates them.
Feature colour (the thing you must see)
Background colour (what it sits on)
Two rules of thumb fall out of this. Light a feature with a similar colour to brighten it, and with a colour from the opposite side of the colour wheel to darken it. And if two materials look identical under every visible colour, try infrared or ultraviolet, where inks, dyes and coatings often behave completely differently.
Wavelength guide
Which LED colour should you specify?
| Wavelength | Best for | Notes |
|---|---|---|
| Red 625 nm | The default for monochrome inspection | Monochrome sensors respond strongly at 625 nm, LEDs are efficient and inexpensive, and red is comfortable for operators near the line. |
| Blue 470 nm | Fine detail, metal surfaces, engraved marks | Shorter wavelengths penetrate less and scatter strongly at the surface, which picks out fine texture and shallow marks. Often the better choice on machined and brushed metal. |
| Green 525 nm | A middle ground, red features on light backgrounds | Useful where red washes out a red feature. Also matches the peak sensitivity of many colour sensors. |
| White | Colour cameras and colour verification | Mandatory when colour itself is the measurement. Specify a consistent colour temperature and keep ambient light out. |
| Infrared 850 to 940 nm | Seeing through some plastics, suppressing print | Many inks and dyes vanish under IR, which cleans up busy packaging. Also useful where visible light would disturb operators. |
| UV 365 to 395 nm | Fluorescing inks, adhesives and coatings | Security marks, glues and optical brighteners glow under UV. Pair with a filter that blocks the UV itself and passes the fluorescence. |
| SWIR | Fill levels through opaque plastic, moisture, sorting | Short wave infrared needs a SWIR camera and suitable illumination, and sees contrast no silicon sensor can. Ask us if visible light has failed. |
One check before committing: sensor response varies between cameras, so when the choice is marginal, glance at the quantum efficiency curve on your camera's datasheet.
Make it repeatable
The accessories that keep it working on a Friday afternoon
A light that produces one good image at the bench is not the job. The job is producing the same image every cycle, for years. Three accessories carry most of that burden.
Cross polarisation
A polariser on the light and a second on the lens, rotated against each other, removes the specular glare that survives diffuse lighting. The go to fix for print under shrink wrap, blister packs and glossy plastics.
Bandpass filters
A filter on the lens matched to the LED wavelength passes your light and rejects everything else. With a strobed light this makes the system close to immune to factory ambient light. We supply MidOpt filters for exactly this.
Strobe controllers
A lighting controller fires the LED only during exposure, freezing motion and allowing safe overdrive well beyond continuous ratings. It also regulates current, so brightness does not drift as the light warms up or ages.
Once the light is right, size the optics to match. Our lens calculator works out focal length, field of view and depth of field, and recommends lenses from stock.
Field notes
Six lighting mistakes we see most often
- Lighting last. The camera and lens get chosen first and the light gets whatever budget is left. Choose the lighting technique with the camera, not after it.
- Fighting glare with brightness. Turning up a ring light on a shiny part makes the hotspot brighter, not the feature. Glare is a geometry and diffusion problem.
- Ignoring ambient light. The demo works in the lab, then sunlight or a roller door changes everything. Strobe the light and fit a matched bandpass filter from day one.
- Running LEDs on a raw supply. Without regulated current, intensity drifts with temperature and age, and your carefully set thresholds drift with it.
- Validating on one golden sample. A light that flatters the perfect part may hide variation. Prove the setup on worst case parts, including the ugly ones.
- Treating white as neutral. White light is a compromise of wavelengths. If a monochrome camera is doing the work, a single colour chosen for contrast almost always beats white.
Questions
Machine vision lighting FAQ
How do I choose the right machine vision light?
Work through three decisions in order: geometry, diffusion, wavelength.
First decide where the light must sit to create contrast, in front, behind, at a low angle or on the lens axis. Then decide how diffuse it must be, based on how shiny and how curved the part is. Finally pick the wavelength that separates the feature from its background. The selector at the top of this page applies those rules for you.
What is the difference between bright field and dark field lighting?
Bright field light reflects from the surface into the camera, so the surface appears bright. Dark field light skims across the surface and misses the camera, so the surface appears dark and only disturbances light up.
Use bright field to see general appearance, print and assembly. Use dark field to make scratches, dents, dust and engraved marks glow against a black background.
When should I use a dome light?
Use a dome when the part is shiny, curved, foil wrapped or made of mixed materials, and glare is destroying the image.
A dome delivers diffuse light from every direction at once, like a cloudy day, so specular hotspots disappear and print becomes readable. Where a full dome will not physically fit, a flat dome gives similar light from a slim panel the camera looks through.
What does a coaxial (DOAL) light do?
A coaxial light uses a beam splitter to send light straight down the lens axis, so flat mirror like surfaces reflect it back and appear bright, while anything tilted, scratched or dented reflects it away and appears dark.
It is the standard choice for flat polished metal, coatings, solder and foil seals. It only works on flat specular surfaces.
When should I use a backlight, and should it be diffuse or collimated?
Use a backlight when the outline of the part carries the information: presence, orientation, dimensions, or flaws inside transparent material.
A diffuse backlight suits general silhouette work and translucent containers. A collimated backlight produces parallel rays for the sharpest possible edge, and paired with a telecentric lens it is the basis of precision optical gauging.
What colour LED should I choose for a monochrome camera?
Red 625 nm is the sensible default, and you move away from it for a reason: blue for fine detail on metal, a colour chosen for contrast when the feature and background are coloured, infrared or ultraviolet when visible light cannot separate them.
The rule for coloured features is simple. Similar colours lighten, opposite colours darken. The contrast simulator on this page lets you test combinations in seconds.
When are infrared or ultraviolet lights used?
Infrared is used to see through some plastics, to suppress printed graphics that confuse an inspection, and to light scenes without visible flicker for operators. Ultraviolet is used to make inks, adhesives, coatings and security features fluoresce.
Both need matching filters on the lens, and UV fluorescence work needs a filter that blocks the excitation light while passing the visible glow.
Do I need a lighting controller or strobe?
If the part moves during exposure, or ambient light varies, or you need more intensity than a continuous rating allows, then yes.
A controller fires the LED in a short, current regulated pulse synchronised with the camera. That freezes motion, permits overdriving the LED far beyond its continuous brightness, and keeps output stable over temperature and time.
How do I stop factory ambient light affecting my vision system?
Combine a strobed, overdriven light with a short exposure and a bandpass filter on the lens matched to the LED wavelength.
The strobe makes your light momentarily far brighter than the room, the short exposure limits how much ambient light is collected, and the filter rejects wavelengths outside your LED band. Physical shrouding helps, but the strobe and filter combination is what makes systems robust.
Can I fix poor lighting in software instead?
Rarely, and never reliably. Software can stretch and filter the contrast that exists in the image, but it cannot recover information the light never put there.
Deep Learning tools are more tolerant of imperfect images than classical algorithms, but they still perform better and need less training data when the lighting does the heavy lifting. Fixing light in hardware is almost always cheaper than compensating in software.
Which machine vision lighting brands does Clearview supply?
Clearview supplies machine vision lighting from Advanced Illumination and ProPhotonix, alongside MidOpt filters and polarisers, and lighting controllers to drive them.
Advanced Illumination covers ring, bar, dome, backlight, line and structured lighting for general inspection, while ProPhotonix specialises in LED line lights and custom illumination. Browse the full illumination collection or ask our engineers to specify a light against your samples.
Insights Test Lab
Not sure yet? Light it in our lab.
Send us sample parts, including the worst ones, and our applications engineers will test them under different camera, lens and lighting combinations in the Insights Test Lab in Thame. You get images, a recommended setup and an honest read on feasibility before you commit to hardware, with loan equipment available to prove it on your own line.