Machine Vision Optics Selection Guides

POMEAS optical applications team · Reviewed by Tiger Xie · Published 2026-10-16

Choosing optics for an inspection system means resolving several questions in a fixed order: what lens class fits the measurement, what magnification and field of view the part needs, whether the sensor and image circle match, how the illumination interacts with the surface, and how much depth of field the workpiece variation demands. This index collects every POMEAS selection guide on those questions and groups them by the decision they support.

Each entry below is a standalone guide with its own worked figures. Start from the group that matches your open question, or read the full list if you are specifying a system from scratch.

1. The guides in this index

A. Lens class and focal length

• FA Industrial Lens Selection Guide | Sensor Size, FOV, WD and Accuracy — FA industrial lens selection guide: how sensor size, FOV, working distance and required accuracy interact, with formulas, worked examples and the errors that limit...
• How to Choose a Telecentric Lens: FOV, WD, DOF & Accuracy — Learn how to select a telecentric lens based on sensor size, magnification, FOV, working distance, depth of field, resolution, distortion and measurement accuracy.
• Built-in Coaxial Telecentric Lens Selection Guide 0.3X–2.0X — Choose a telecentric lens with built-in coaxial illumination: 0.3X–2.0X model matrix, FOV and DOF formulas, and how to check pixel matching.
• When Is a Telecentric Lens the Wrong Choice? FAQ — Telecentric lenses are specified far more often than they are needed.
• How to Choose a Zoom Lens + APO Objective: 5-Step Checklist — Select a zoom lens APO objective in 5 steps: set NA from feature size, size FOV, match the TV tube, check low-mag vignetting, request verified data.
• 1.1-inch Camera and Telecentric Lens Matching Guide — How to match a 1.1-inch (Φ18.4 mm) camera to a telecentric lens: image-circle check, C/F-mount back focus, magnification–FOV math, corner shading test.
• Matching Camera Sensor to Zoom Lens Image Circle: 1/3–1 Inch — Camera sensor to zoom lens image circle matching: 1x, 1.5x, 2x tube rules, why 1/3-inch sensors never flag vignetting, and the 72.5% field limit.

B. Selection driven by the inspection task

• PCB AOI Optical Selection: Pixel Size, Lens Type, Working Distance and Lighting — A four-step optical selection for PCB AOI: pixel size from the smallest feature, lens type against height variation, working distance as machine budget, and lighting...
• Zoom Lens for 10–4 mm FOV, 80–100 mm WD & 5 μm Defects — Calculate the zoom lens magnification for a 2/3 5 MP camera, 10–4 mm FOV and 80–100 mm WD, and see whether 5–10 μm chip defects are detectable.
• 6.5X vs 12.5X Industrial Zoom Lenses: Selection and Integration Guide — 6.5X vs 12.5X industrial zoom lenses compared on published data: magnification range, field of view, working distance, depth of field, control options and integration...
• IMAGE3 Selection Guide: Choose the Right Image Measuring Machine — How to select an image measuring machine: accuracy, optical configuration and IMAGE3 model choice, plus a quick selection chart and checklist.
• From Microscope to Machine Vision: How to Select a Camera, Zoom Lens and Magnification — Replacing a microscope with an industrial camera and zoom lens?

C. Illumination selection

• Machine Vision Light Source Selection: Point, Ring, Telecentric Parallel and Coaxial — How to choose a machine vision light source: reflected vs transmitted light, and point, ring, telecentric parallel and coaxial types, with published POMEAS specifications...
• Machine Vision Light Source Colour: Wavelength Selection and Photolithography Yellow Light — How to choose machine vision light source colour and wavelength: same-colour vs complementary light, monochrome and colour camera pairing, and how to turn a...
• Coaxial Illumination for Reflective Metal: 3 Types, 7 Steps — Mirror, brushed and coated metal return light differently.

D. Depth of field and workpiece variation

• Parts With Different Heights: Depth of Field FAQ — Why a stepped part looks soft on one level, why a step wall hides part of the lower surface, and how to verify depth of field, occlusion and scale before production.

2. How to use this index

Read in the order the decisions are made: lens class first, then sensor and image circle, then illumination, then depth of field against the part tolerance. If the system already exists and you are replacing one component, go straight to the group that covers that component.

3. Frequently asked questions

How do I choose between a telecentric lens and a standard FA lens?

Decide from the measurement, not from the budget line. A telecentric lens holds magnification across the working distance, so a part that moves toward or away from the camera still measures the same. A standard FA lens changes magnification with distance, which is acceptable when you only need presence or position, and cheaper when the field of view is large. If the tolerance is tighter than roughly one tenth of the pixel size on the object side, start with telecentric.

What is the first number I should calculate when selecting a lens?

Start with object-side pixel size: sensor pixel pitch divided by magnification. Every other selection decision, from lens class to illumination, follows from whether that number is smaller than the defect you must see. Field of view follows from sensor size divided by magnification, and working distance comes from the mechanical envelope you actually have.

Can one lens cover several product variants with different fields of view?

Yes, and it is the usual reason to accept the extra cost of a zoom lens. A continuous or detented zoom lens changes magnification without swapping hardware, so one camera position can serve several part sizes. The trade-offs are that magnification must be set to a repeatable position, and that depth of field and image brightness change with magnification. Both are covered in the technical and comparison indexes.

How do I choose the illumination for a shiny metal part?

Match the geometry, not the surface name. Specular surfaces return light along the reflection angle, so a coaxial or dome arrangement that puts the source on the optical axis is usually needed to get contrast on machined faces. Diffuse dark-field arrangements work when you want scratches or edges rather than flat surfaces. The lighting selection guides below cover point, ring, coaxial and telecentric parallel options with the surface each one suits.

Does a larger sensor always mean a better measurement?

No. A larger sensor only helps if the lens projects a usable image circle across it and the resulting object-side pixel size still resolves the feature. Mounting a large sensor behind a lens with a smaller image circle produces corner shading and wasted pixels. Check image circle, mount and back focus before comparing sensor specifications.

Where do I record the selection once it is made?

As a written specification: object-side pixel size, field of view, working distance range, depth of field required by the part tolerance, illumination geometry and wavelength, and the magnification repeatability the process needs. The calibration and repeatability guides in the technical index describe how to verify each one after installation.

4. Related POMEAS resources

• Machine Vision Inspection Application Cases: Complete Index
• Machine Vision Optics Technical Guides: Complete Index
• Machine Vision Optics Calculators and Formulas: Complete Index
• Machine Vision Optics Comparisons: Complete Index
• Machine Vision Optics Troubleshooting: Symptom Index
• All POMEAS machine vision knowledge articles
• POMEAS zoom lenses
• POMEAS telecentric lenses
• POMEAS FA lenses
• POMEAS machine vision lighting
• POMEAS Technical Reference Series — full-length notes on optical imaging performance testing and measurement method

Talk to a POMEAS Engineer About Lens Selection

If you have a part drawing, a tolerance and a field of view, send those three things and we can work from the measurement requirement rather than from a product list. Tell us the smallest feature you must judge, the space available for the lens, and whether the part is stationary at the imaging position.

Email: [email protected] | WhatsApp: +86 185 9810 2007

Reviewed by Tiger Xie.