Telecentric Lens Basics

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Telecentric Lens Basics

A telecentric lens keeps magnification more stable when object height changes. Use it for 2D measurement when perspective error is unacceptable; confirm 3 inputs first: FOV, sensor size and working distance.

Where this matters

Start with the inspection condition.

A telecentric lens keeps magnification more stable when object height changes. Use it for 2D measurement when perspective error is unacceptable; confirm 3 inputs first: FOV, sensor size and working distance.

Why projects fail

Confirm the limits that change hardware.

They should be selected with FOV, sensor size and working distance together.

RFQ preparation

Send enough context for a real review.

Regular lenses remain better for many low-precision presence or defect checks.

What engineering should check

What this page should help teams decide.

Telecentric lenses reduce perspective error in measurement tasks.
They should be selected with FOV, sensor size and working distance together.
Regular lenses remain better for many low-precision presence or defect checks.

Related Deyi routes

Product families commonly involved.

Practical note

Telecentric optics protect measurement repeatability.

When part height changes, regular lenses can change apparent size. Telecentric lenses reduce that perspective effect, which helps gauge-style inspection.

Practical note

Telecentric lenses are not needed for every inspection.

Presence checks, color checks and many defect tasks can use regular lenses. Telecentric cost and size are justified when measurement error from perspective becomes unacceptable.

Practical note

FOV, sensor and working distance must match.

Telecentric selection is constrained by object size, camera sensor size, required magnification and available space. These 3 inputs should be confirmed before RFQ.

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.

01

Measurement accuracy

Telecentric reduces perspective-driven size change.

02

Cost and size

Telecentric routes are larger and more specialized.

03

Best fit

Use for edges, holes, gauges and precision dimensions.

Decision table

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

Factor	Practical rule	RFQ impact
Measurement accuracy	Telecentric reduces perspective-driven size change.	Send tolerance and object height variation.
Cost and size	Telecentric routes are larger and more specialized.	Confirm budget and mounting envelope.
Best fit	Use for edges, holes, gauges and precision dimensions.	Send FOV, working distance and sensor target.

Application proof

Related delivery routes that make this selection decision concrete.

View all cases

Dimension measurement

Stamped Part Instant Measurement

Small parts need fast dimensional verification without slow manual measurement or inconsistent operator positioning.

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.

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 telecentric lens basics.

Ask engineering

What does a telecentric lens do?

A telecentric lens keeps magnification more stable across object height changes, reducing perspective error for machine vision measurement.

When should I use a telecentric lens?

Use it when dimensional accuracy, edge repeatability or object height variation makes regular lens perspective error too large.

What information is needed to choose a telecentric lens?

Provide object size, sensor size, working distance, tolerance, part height variation, lighting route and mounting space.