Machine Vision Lenses for Quality Inspection: How to Choose Optics by Task
Machine vision lens selection for label, seal, liquid level, and print inspection, matched to defect size, resolution, working distance, and depth of field.
The lens decides whether a quality inspection system sees the defects that matter. Start with the defect, not the camera: minimum feature size sets required resolution, working distance sets focal length, and surface geometry decides whether you need a fixed-aperture Commonlands M12 lens or a C-mount lens with an adjustable iris.
Label, seal, liquid level, and print inspection each push on a different constraint: curved-surface depth of field, contrast and presentation, backlighting, and registration-grade distortion. This guide sets the shared specification order once, then takes each application on its own terms.
Start with the Defect: What Are You Trying to See?
Every inspection spec starts with the defect, not the focal length and not the sensor. Surface scratches and cracks need strong MTF (the contrast a lens holds at a given spatial frequency). Go/no-go dimensional measurement needs low distortion, since geometric error in the lens becomes measurement error directly.
The output of this step is one number: minimum detectable feature size. A 50 µm scratch and a 500 µm dimensional deviation drive completely different specs downstream. When the defect type is unclear, design to the smallest feature you expect to care about. You can open the aperture or reduce magnification later, but you cannot recover detail the optics never captured.
This Commonlands hub covers four recurring applications: label, seal, liquid level, and print inspection. Each section names its sub-tasks and the constraint that dominates.
Calculate the Required Resolution
Once you have a minimum feature size, set sensor resolution at 3 to 5 pixels per smallest feature. Three pixels gives marginal detection; five gives reliable detection with margin for thresholding. Use five unless you have a reason not to.
Worked example: detecting 50 µm defects across a 100mm field at 5 pixels each needs 100 px/mm, or 10,000 pixels on the critical axis, a 100MP-class sensor at 1:1. Most real stations relax to 3 pixels, shrink the field, or split it across cameras. A 12MP 1.1" sensor gives only about 2 pixels per 50 µm defect across that field.
Orientation only changes which axis carries the requirement, not the total. Lens resolution must also meet the sensor's pixel pitch: a 12MP-rated lens resolves 3.45 µm pixels, and a lower-rated lens on a finer sensor means optical blur, not the sensor, sets your resolution. See the spatial resolution guide for the full relationship.
Set the Working Distance First, Then Compute the Focal Length
Working distance is set early by conveyor height, robot reach, enclosure size, and part-loading clearance. It is not something you choose after browsing a catalog. Once mechanical design is committed, it is effectively fixed. With working distance and field of view in hand, focal length follows for rectilinear projection:
At a 300mm working distance, a 100mm required field of view, and a 14.1mm sensor width (1.1" sensor): EFL = 300 × 14.1 / 100 = 42.3mm. Round the focal length down to the nearest stock value, not up: a 35mm lens frames 121mm and covers the field, while a 50mm lens frames only 85mm and clips it. Verify your numbers with the Commonlands field of view calculator or EFL calculator. The focal length selection guide has more worked examples.
Choose the Right Aperture
Aperture trades depth of field against diffraction. For flat parts at a fixed working distance, open up for maximum light and resolution, typically F/2.8 to F/5.6, MTF permitting. For parts with height variation, stop down using the depth of field calculator to cover the height range.
Diffraction sets the ceiling: above F# ≈ 2 × pixel_pitch_µm, diffraction softening usually exceeds the depth-of-field gain from stopping down further. For 3.45 µm pixels that ceiling is roughly F/7; for 25MP sensors with 2.74 µm pixels it is closer to F/5.5. See the f-number guide for the full tradeoff.
Aperture and illumination are coupled across all four applications. Stopping down for depth of field costs light, and in machine vision you recover it with brighter or strobed illumination. Commonlands M12 lenses ship with a fixed aperture, which removes this lever, leaving working distance and lighting geometry as the only variables.
What Machine Vision Lens Should I Use for Label Inspection?
Label inspection is a resolution and glare problem on curved, reflective surfaces. It splits into distinct tasks: barcode and Data Matrix reading, OCR and lot code reading, placement verification, and print-defect inspection. Barcode and 2D decoders read bar-to-space ratios, so distortion that compresses modules near the periphery hurts decode confidence before resolution does. Target 5 or more pixels across the narrowest element.
A few millimeters of height excursion on a curved container pressures depth of field, the adjustable-iris case from the aperture section, so a C-mount lens is the usual choice once labels sit on bottles or formed packs. A lens under 0.3% TV distortion removes distortion from the variable list. See what is a low distortion lens for how the specs relate.
The Commonlands CIL522 12mm C-mount fits curved-container labels, and the CIL052 5.2mm M12 suits compact reads on flat labels. Both appear with full specs in the table below. Telecentric optics are rarely right for decode or pass/fail tasks, and Commonlands does not sell them.
What Machine Vision Lens Should I Use for Seal Inspection?
Seal inspection is a contrast and presentation problem, and it splits into tasks that do not share one lens. Contamination detection reads contrast between residue and seal material, where lighting geometry does more than lens choice. Seal-width verification is where distortion bites: barrel distortion makes an identical seal look narrower at the edges, so a pass/fail width threshold holds reliably only at sub-0.5% distortion.
Packaging is rarely flat. Pouches swell, blister packs raise cavities, and sachets sag between guides. That height variation pressures depth of field, the same iris case again. Confirm the lens publishes MTF at the sensor corner: low distortion does not guarantee sharp edges, since field curvature and astigmatism degrade corners independently.
The Commonlands CIL522 12mm C-mount handles general seal work where depth of field is the pressure, the CIL544 25mm C-mount suits contamination detection or wider seal lanes at longer standoff, and the CIL052 5.2mm M12 fits narrow pouch seals where the head must stay compact.
What Machine Vision Lens Should I Use for Liquid Level Inspection?
Liquid level and fill inspection depends on transparent-container backlighting more than on lens choice. Diffused backlighting silhouettes the container and liquid column, so the meniscus reads as a sharp edge for most liquids. Container positioning matters as much: if the container shifts between frames, the meniscus's apparent position moves even when the fill level has not.
The first optical decision is whether the station passes a threshold or measures fill height. For threshold pass/fail, moderate distortion of 0.5% TV or less is enough, since the reference mark and meniscus share the frame and error largely cancels. This is where compact M12 lenses win: the Commonlands CIL083 8mm M12 at $19, F/2.8, and -0.5% TV distortion covers 1/1.8" sensors and keeps cost per lane low, where the $100 gap against a $119 C-mount lens is $800 across an eight-lane system.
For measurement-grade fill, where a pixel row maps to a physical height, distortion becomes systematic bias rather than noise that averages out. Target under 0.2% distortion: the CIL533 16mm C-mount at -0.1% or the CIL553 16mm C-mount at -0.09%. For 360-degree bottle inspection in a single pass or continuous-web line scan, Commonlands does not sell pericentric, liquid-lens, or line-scan optics. That is a specialist-vendor architecture.
What Machine Vision Lens Should I Use for Print Inspection?
Print inspection is a registration and fine-feature contrast problem that splits by task. Date and lot code reading is the least demanding, since fixed-format decoders know the character set. OCR and character verification is tighter: the algorithm must distinguish stroke geometry with no prior knowledge, so contrast uniformity and resolution per stroke matter.
Print-position and registration is the strictest distortion case in this hub. Distortion displacement scales with radial distance from the field center, so on a 200mm zone the edge sits 100mm out, and a lens with 2% barrel distortion produces roughly 2mm of apparent position error there. Against registration tolerances often ±0.5mm or tighter, that makes the measurement meaningless, so low distortion is a prerequisite, not an optimization.
C-mount is the practical default for fixed-station print inspection, for the iris, larger sensor coverage, and higher-resolution designs. The Commonlands CIL522 12mm C-mount covers general work, the CIL544 25mm C-mount handles high-resolution defect and small-character inspection at longer standoff, and the CIL052 5.2mm M12 suits flat-surface date code heads.
Match the Sensor Format to the Lens
The lens image circle must fully cover the sensor diagonal. A 2/3" lens has about an 11mm image circle, while a 1.1" sensor has a 17.6mm diagonal, so a 2/3" lens on a 1.1" sensor vignettes badly: dark corners and edge MTF that collapses before the sensor edge. Oversizing is the safe direction; undersizing produces vignetting no software recovers.
Oversizing is not automatically safe on resolution, though: a lens rated for a coarser pixel pitch can under-resolve a finer sensor, so confirm the resolution rating matches the sensor's pixel pitch. Commonlands lists a target sensor format and pixel pitch for each lens for exactly this reason. Full format-matching and vignetting mechanics are in the sensor size and lens compatibility guide.
Top Machine Vision Lenses for Quality Inspection
Commonlands covers six quality-inspection tasks with C-mount and M12 lenses priced from $19 to $349. The table pairs each task with a specific SKU, mount, focal length, and published distortion.
How we picked: each row starts from the constraint that governs the task, then names the lowest-cost Commonlands lens that meets it with sensor-format margin. Resolution and contrast govern defect work, low distortion governs measurement and registration, and depth-of-field control governs curved surfaces. Distortion values come from each product page.
| # | 점검 업무 | 렌즈 | 마운트 | EFL | 왜곡 | 이 선수를 선택한 이유 |
|---|---|---|---|---|---|---|
| 1 | Surface defect detection | CIL512 | C-마운트 | 12mm | Not the deciding spec | 12MP across a 1.1" sensor and a 17.6mm image circle give the wide-field resolution scratch and blemish scans need. Pass/fail defect work tolerates moderate distortion. |
| 2 | 라벨 검사 | CIL522 | C-마운트 | 12mm | 0.4% | F/1.4 adjustable iris recovers depth of field on curved containers. The CIL052 5.2mm M12 at -0.1% is the flat-label, compact-head alternative. |
| 3 | 인쇄 및 등록 검사 | CIL533 | C-마운트 | 16mm | -0.1% | Low distortion holds registration-mark geometry across the field, where a 2% barrel figure would exceed ±0.5mm tolerances. F/2.0, 2/3" up to 12MP. |
| 4 | Seal and contamination inspection | CIL544 | C-마운트 | 25mm | Not the deciding spec | 20MP-plus resolution and a 17.6mm image circle cover contamination detection and wider seal lanes at longer standoff, with an adjustable iris for uneven packaging. |
| 5 | 액체 수위 및 충전량 검사 | CIL083 | M12 | 8mm | -0.5% TV | At $19 it keeps cost per lane low on multi-lane threshold pass/fail fill checks up to a 1/1.8" sensor. Measurement-grade fill moves to CIL533 or CIL553. |
| 6 | Dimensional gauging and measurement | CIL553 | C-마운트 | 16mm | -0.09% | Lowest published distortion in this set with 25MP-class resolution, so geometric error stays under tight measurement tolerances. |
Dimensional gauging at the tightest tolerances calls for a telecentric lens, which holds apparent object size constant across working distance. That is a third-party, metrology-only class, not a Commonlands product. The lenses above cover the tiers beneath it.
Product detail for the lenses named above. Confirm sensor-format coverage before ordering.
자주 묻는 질문
머신 비전 품질 검사를 위한 렌즈는 어떻게 선택해야 할까요?
Start with your smallest defect size and work backward. The pixels needed to detect it reliably, 3 to 5 per defect, set your sensor resolution. Working distance is usually fixed by your setup, and it determines focal length through the rectilinear equation. Aperture then sets depth of field. Work in this order: defect size, sensor resolution, working distance, focal length, aperture, sensor format.
라벨 검사에 어떤 머신 비전 렌즈를 사용해야 할까요?
Name the task first: barcode/Data Matrix reading, OCR/lot code reading, placement verification, or print-defect inspection. Barcode reading needs low distortion and enough pixels per module. OCR needs tighter resolution and contrast uniformity. Most stations choose a compact M12 lens for flat surfaces or a C-mount lens with an adjustable iris for curved containers. Telecentric optics are rarely the right answer for label inspection.
밀봉 검사에 어떤 머신 비전 렌즈를 사용해야 할까요?
Start with the task. Contamination detection needs contrast and spatial resolution, with lighting geometry doing more than lens choice. Seal-width verification needs low distortion (sub-0.5%) to keep apparent width consistent across the field. Seal-position and continuity checks need field coverage and resolution along the seal length. Choose a C-mount lens with an adjustable iris when packaging presentation is variable, and a compact M12 lens when the head must stay small.
액체 수위 검사에 어떤 머신 비전 렌즈를 사용해야 할까요?
For threshold pass/fail fill checks, moderate distortion around 0.5% TV is enough and cost per lane matters. The CIL083 8mm M12 at $19 and -0.5% TV distortion handles these on multi-lane systems. For measurement-grade fill where image height maps to physical volume, target under 0.2% distortion, such as the CIL533 16mm C-mount at -0.1% or the CIL553 16mm C-mount at -0.09%.
인쇄 검사에 어떤 머신 비전 렌즈를 사용해야 할까요?
Date and lot code reading needs enough pixels per character and low distortion to keep character geometry consistent. OCR and character verification is more demanding, since the algorithm must distinguish individual strokes. Print-position and registration checks need low distortion across the full field. A lens with 2% barrel distortion introduces position errors that exceed registration tolerances. C-mount with an adjustable iris is the practical default for fixed-station area-scan work. M12 fits a compact head on a flat surface.
Need Help Sizing a Lens for an Inspection Application?
Commonlands engineering can work through defect size, resolution, working distance, and sensor format with you before you commit to hardware.