Selection Guides

How to Choose Machine Vision Lighting

Choose machine vision lighting by surface finish, defect direction, camera angle, working distance and acceptance evidence instead of choosing by light shape alone.

Engineering bench with industrial camera and multiple machine vision lighting routes for reflective metal inspection

Direct answer

How to Choose Machine Vision Lighting

Choose machine vision lighting by proving contrast on the real defect first. For most RFQs, compare 4 routes: backlight for silhouette edges, coaxial for flat reflective marks, dome for curved glare control and low-angle bar or dark-field light for scratches and burrs.

Where this matters

Start with the inspection condition.

Do not choose the light by catalog shape. Start with the defect evidence: edge, surface scratch, printed mark, DPM code or height-related shadow, then test the light geometry on good, bad and borderline samples.

Why projects fail

Confirm the limits that change hardware.

Reflective surfaces need controlled reflection, diffusion or dark-field geometry.

RFQ preparation

Send enough context for a real review.

Backlight is often best for edge, hole and silhouette checks.

What engineering should check

What this page should help teams decide.

Start from defect contrast, not light shape.
Reflective surfaces need controlled reflection, diffusion or dark-field geometry.
Backlight is often best for edge, hole and silhouette checks.

Related Deyi routes

Product families commonly involved.

Practical note

Define the optical evidence before selecting the light body.

A scratch, printed code, missing edge and burr are different optical problems. The first review should state what must become brighter, darker or sharper in the image, then choose the light geometry that creates that separation.

Practical note

Separate silhouette tasks from surface-detail tasks.

Backlight is usually the safest first route for outer diameter, hole, gap and edge checks because it removes most surface texture. It is the wrong route if the defect is printed ink, shallow engraving or a top-surface stain.

Practical note

Reflective metal needs controlled reflection, not more brightness.

Increasing light power often increases glare. Flat reflective surfaces may need coaxial lighting, curved parts may need dome diffusion, and directional scratches often need low-angle bar or dark-field lighting matched to the defect direction.

Practical note

Lock exposure, aperture and trigger timing with the light test.

Lighting selection is not finished until the image stays stable at production speed. Exposure time, lens aperture, strobe controller, camera angle and fixture repeatability should be checked with the same samples used for 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.

Backlight

Use when the pass/fail rule depends on silhouette, edge, hole, gap or outline.

Coaxial light

Use for flat reflective surfaces, printed marks, scratches or features that need camera-axis reflection control.

Dome light

Use when curved or shiny surfaces create harsh highlights that hide defects.

Decision table

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

Factor	Practical rule	RFQ impact
Backlight	Use when the pass/fail rule depends on silhouette, edge, hole, gap or outline.	Send target edge tolerance, part thickness and whether top-surface detail matters.
Coaxial light	Use for flat reflective surfaces, printed marks, scratches or features that need camera-axis reflection control.	Send images showing glare and the target mark under current lighting.
Dome light	Use when curved or shiny surfaces create harsh highlights that hide defects.	Confirm dome size, working distance and available mounting envelope.
Bar or dark-field light	Use low angles to reveal scratches, burrs, raised edges or directional surface defects.	Send defect direction, part movement direction and line-speed constraints.

Application proof

Related delivery routes that make this selection decision concrete.

View all cases

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.

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.

Packaging inspection

Packaging Label and Barcode Traceability

Labels and codes move quickly, vary in position and must be verified without slowing the packaging line.

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 how to choose machine vision lighting.

Ask engineering

What is the best machine vision lighting for reflective metal?

There is no single best light. Flat reflective metal often starts with coaxial lighting, curved reflective metal often starts with dome diffusion, and scratches or burrs often need low-angle bar or dark-field lighting.

When should I use a backlight in machine vision?

Use backlight when the inspection target is an edge, hole, gap, outside diameter or silhouette. Avoid it when the decision depends on top-surface printing, shallow engraving or texture.

What should I send for a machine vision lighting recommendation?

Send good, bad and borderline part photos, material finish, defect size, defect direction, FOV, working distance, camera angle, line speed and current lighting failure examples.