Selection Guides

Machine Vision Lighting Types

Compare ring, bar, dome, coaxial, backlight and line lighting types by surface behavior, defect contrast and installation constraints.

Direct answer

Machine Vision Lighting Types

Machine vision lighting types should be selected by the signal you need to create: silhouette, surface texture, scratch shadow, printed contrast, reflective highlight control or line-scan uniformity. The right light is the one that makes the defect measurable before software tuning.

Where this matters

Start with the inspection condition.

Start with defect and surface behavior. Backlight handles edges, coaxial and dome handle reflection, bar or dark-field lights reveal directional defects, and line lights support line-scan systems.

Why projects fail

Confirm the limits that change hardware.

Backlight works for silhouette and edge checks.

RFQ preparation

Send enough context for a real review.

Dome and coaxial lighting help reflective parts.

What engineering should check

What this page should help teams decide.

Lighting type should follow the defect and surface.
Backlight works for silhouette and edge checks.
Dome and coaxial lighting help reflective parts.

Related Deyi routes

Product families commonly involved.

Practical note

Lighting creates the inspection signal.

Software thresholds only work when the image already separates good and bad parts. The first lighting question is not brightness, but which geometry makes the target feature visible and repeatable.

Practical note

Use backlight for silhouette evidence.

Backlights are strong for edge, hole, gap, diameter and missing-part checks because they remove surface texture. They are weak for top-surface print, stains, shallow scratches or texture defects.

Practical note

Use reflection control for glossy surfaces.

Flat reflective parts may need coaxial lighting, curved shiny parts may need dome diffusion, and burrs or scratches may need low-angle bar or dark-field light. More power can make glare worse if geometry is wrong.

Practical note

Validate the light at production exposure.

A light that works with long exposure on a bench can fail at line speed. Test intensity, strobe controller, heat, mounting angle and fixture repeatability before acceptance.

How to test before buying

Use this guide as a pre-RFQ decision filter, not as a part-number shortcut.

Machine vision selection is usually stable when the project starts from the inspection condition instead of a catalog model. Before requesting a quote, define what must be detected or measured, how the part moves, what surface behavior affects contrast and which factory constraint cannot change.

Use this guide to translate the requirement into testable inputs: sample images, target tolerance, line speed, field of view, working distance, mounting envelope and the current failure mode. That gives the factory enough evidence to map the request to camera, lighting, optics, reader or 3D routes.

Decision checks

Three checks before locking the route.

Ring light

Use for compact general inspection, labels, presence and non-glossy features.

Bar or dark-field light

Use directional low-angle lighting for scratches, burrs, raised edges and texture.

Backlight

Use for silhouette, hole, gap, edge and outline measurement.

Decision table

Use these data points to turn the concept into an RFQ-ready decision.

Factor	Practical rule	RFQ impact
Ring light	Use for compact general inspection, labels, presence and non-glossy features.	Send working distance, lens size and glare examples.
Bar or dark-field light	Use directional low-angle lighting for scratches, burrs, raised edges and texture.	Send defect direction, part movement direction and sample images.
Backlight	Use for silhouette, hole, gap, edge and outline measurement.	Send edge tolerance and whether top-surface detail matters.
Coaxial light	Use for flat reflective surfaces, printed marks and features needing camera-axis reflection.	Send current glare images and camera angle constraints.
Dome or diffuse light	Use for curved glossy surfaces where harsh highlights hide defects.	Confirm part size, dome clearance and maintenance access.
Line light	Use for line scan and continuous web inspection where uniform scan-line intensity matters.	Send web width, speed and defect size.

Application proof

Related delivery routes that make this selection decision concrete.

View all cases

Electronics inspection

PCB Connector Pin Presence Inspection

Small connector features require stable contrast, low distortion and repeatable part positioning before a pass/fail threshold can be trusted.

Automotive parts inspection

Automotive Metal Surface Defect Inspection

Reflective metal surfaces can hide scratches and burrs unless the lighting geometry is matched to the defect direction and part movement.

Textile and web inspection

Roll-to-Roll Web Defect Inspection

Wide moving material needs even illumination, encoder synchronization and enough line rate to avoid missing small defects.

Common mistakes

Problems that slow down selection.

Selecting by model number before the inspection target is measurable.
Treating lighting as an accessory instead of the main contrast-control tool.
Ignoring fixture stability, part variation and operator maintenance workflow.

Factory handoff

What Deyi Vision reviews after receiving the project details.

The factory route review starts by checking whether the image can be made stable with lighting and fixture control. Then the camera, lens, reader or 3D sensor route is sized against speed, resolution, interface and installation constraints.

If you already have a Keyence, Cognex, Basler, OPT, LMI, Hikrobot or barcode-reader reference, include it as a reference model. Deyi Vision uses it to understand the application class; final selection still depends on real samples and production limits.

Guide to RFQ

Have a real part, sample image or production constraint?

Use the guide to frame the question, then send the details so engineering can recommend a route.

Request engineering RFQ

Guide FAQ

Questions related to machine vision lighting types.

Ask engineering

What are the main types of machine vision lighting?

Common types include ring, bar, dome, coaxial, backlight, dark-field and line lighting. The best choice depends on part surface and target defect.

Which light should I try first for measurement?

For outer edges, holes, gaps and silhouettes, start with backlight. For surface measurement or printed features, the route depends on material and reflection.

Why does adding more light not always improve machine vision?

If the light angle is wrong, more intensity can increase glare, wash out texture or hide scratches. Geometry usually matters more than raw brightness.