Arbeitsabstand und Mindestobjektabstand für Objektive in der Bildverarbeitung und Robotik
The machine sets the working distance and the lens sets the minimum object distance. This guide covers both, and what happens to image quality at short range.
Working distance (WD) is the gap from the front of the lens housing to the object. Minimum object distance (MOD) is the closest that gap can get while the lens still focuses, and it is set by the lens. Early in a project there may be room to move WD. Once the mechanical design is committed it is fixed, and the lens must cover the required field of view at that distance.
C-mount and M12 lenses reach focus differently. Adjustable C-mount lenses focus by ring rotation, and the internals doing the moving differ by design. An M12 lens moves as a rigid body, threading in or out of its holder. Both work well at the distances they are designed for and behave differently at the edges of their range. This guide covers working distance selection, the optics behind minimum object distance, and how to hold sharpness across the full field.
Was bedeutet „Arbeitsabstand“?
Working distance (WD) is the distance from the front of the lens housing to the target surface. In machine vision it is set by conveyor height, fixture geometry, or the inspection station layout; in robotics it follows from arm reach, end-effector clearance, or bin depth. Early on, WD is a design variable, since brackets and gantry heights can move. Once the mechanical design is committed it is fixed, and the lens has to perform at whatever distance the system requires.
Wie der Arbeitsabstand die Wahl des Objektivs beeinflusst
WD sets the required focal length. A longer distance needs a longer EFL to cover the same field of view; a shorter distance needs a shorter one. The relationship comes from rectilinear projection geometry (Hecht, Optics, 5th ed., §5.2):
For wide-angle or fisheye lenses with significant distortion, use the Commonlands distortion-corrected field of view calculator instead of the thin-lens estimate.
Arbeitsabstand im Vergleich zur Schärfentiefe
A robot bin-picking at 150mm and the same camera inspecting at 600mm differ in depth of field only if the framing changes with them. Object-side depth of field follows magnification and working F-number (about 2Nwc / m²), so holding the field of view fixed from 150mm to 600mm takes roughly four times the focal length and returns about the same depth. Depth grows with distance only when the lens stays put and the field widens.
Was die minimale Objektentfernung bedeutet und warum sie je nach Montierungstyp variiert
Minimum object distance (MOD) is the closest distance at which a lens can focus in the center of the image, measured from the front of the lens to the object. Not every datasheet lists it, so you may need to verify it experimentally or request it from the manufacturer. How MOD behaves depends on whether the lens is C-mount or M12, because the two focus in different ways.
C-mount: ring-driven focus
Turning the focus ring of an adjustable C-mount lens moves optics along the axis; whether it carries the whole cell, the front group, or cam-guided internal groups depends on the design, so confirm the mechanism for the lens you are evaluating on its datasheet or with Commonlands engineering.
MOD is the hard limit set by the end of focus travel. When the ring hits its stop, the focus mechanism is at the end of its travel and the object cannot be focused any closer without an extension tube.
A shorter EFL needs less image-side travel to reach the same object distance, but MOD does not follow focal length on its own. It falls out of the prescription, the conjugate the design was corrected for, and how much travel the mechanics allow, so two lenses of the same EFL can list very different MODs (Kingslake, Lens Design Fundamentals, 2nd ed., §18.3).
M12: Starren Fokus durch Gewindeverstellung
An M12 lens has no internal moving groups. It is a rigid assembly that threads into a holder, and focus is set by screwing it in or out to change the lens-to-sensor distance. So M12 has no travel-stop MOD, though it does have real limits: with a tall enough holder the center can usually be brought into focus, but thread engagement, sensor and rear-element clearance, and the aberrations that grow as the conjugate moves off the design point all bound how close it goes.
Off-axis aberration is the usual limit at short range, but not always the first. Because the elements never move relative to each other, nothing rebalances as focus changes, so the corners often soften while the center holds, and on some designs spherical aberration at the new conjugate takes the center down first. Which one goes depends on the prescription, the pixel pitch, and how far the WD sits from the design distance, so measure center and corner.
Commonlands can confirm the MOD for any of its C-mount and M12 lenses on request.
Arbeitsabstand vs. Mindestobjektabstand
These two numbers show up in many lens specs, though not every manufacturer publishes MOD. They are not the same thing, and confusing them is one of the most common reasons a vision system fails to focus after integration. Commonlands confirms working distance guidance and MOD for its machine vision lenses on request.
| Begriff | Gemessen ab | Gemessen bis | Wer legt das fest? | Anmerkungen |
|---|---|---|---|---|
| Arbeitsabstand (WD) | Vorderseite des Objektivgehäuses | Objektoberfläche | Maschinenkonstrukteur | Wird durch den mechanischen Aufbau bestimmt. Keine Eigenschaft des Objektivs. |
| Mindestobjektabstand (MOD) | Vorderseite des Objektivs | Objektoberfläche | Objektivhersteller | C-mount: hard limit (end of focus travel). M12: practical limit (thread engagement or field quality). Not always published. |
When a datasheet lists MOD, check whether it refers to center focus or full-field performance. The physics behind it is the thin lens equation, 1/f = 1/do + 1/di (Hecht, Optics, 5th ed., §5.2). As the object moves closer, the image distance di grows, and the C-mount focus travel or the M12 thread depth supplies that extra distance. Note that do is referenced to the object-side principal plane, not the housing, so it differs from a housing-measured MOD by whatever offset the design puts between them.
What happens at short working distance
Center focus is rarely the problem at short working distance; corner sharpness is. The reason is the design conjugate. Every lens is aberration-corrected for a target object distance. Many M12 lenses are corrected for longer distances, so field curvature and astigmatism are balanced there. As the object moves off that conjugate, the best-focus surface for the corners no longer sits on the flat sensor and they degrade. How much depends on the prescription, so two M12 lenses with similar headline specs can behave differently at the same short WD.
Smaller pixels make this more visible, since the same blur spot spans more pixels on a fine-pitch sensor, so re-verify lens performance whenever a sensor upgrade reduces pixel pitch.
At short range, bench-test 2-3 candidate M12 lenses at the actual distance on the actual sensor and check the corners, not just the center. If one passes and another does not at the same distance, that is the prescription difference at work. Commonlands can confirm the finite conjugate correction for any of its lenses on request.
Auswahl der Halterung nach Arbeitsabstand
These bands group working distances by packaging, not by optical thresholds. The point where corners degrade shifts with prescription, F#, pixel pitch, and sensor size.
The 50mm-500mm figures below are each SKU's correction range, not a promise of uniform performance across a decade of object distance. A range that wide still needs measured through-focus and field data at the exact working distance, sensor, and resolution target before it is designed in.
| Arbeitsabstand | M12-Standardobjektiv | M12 finite conjugate (CIL064, CIL142, CIL121) | C-Mount |
|---|---|---|---|
| Größere Arbeitsabstände | Eine größere Auswahl an Standardobjektiven könnte sinnvoll sein; überprüfen Sie die Leistung über das gesamte Bildfeld für den jeweiligen Sensor und die angestrebte Auflösung. | Corrected for the 50mm-500mm range; verify performance beyond it | Eine größere Auswahl an Objektiven könnte sinnvoll sein; überprüfen Sie die Leistung im gesamten Bildfeld |
| Kurze Reichweite (unter einigen hundert Millimetern) | Risikobereich: Überprüfen Sie die Kantenschärfe bei der tatsächlichen Arbeitsentfernung, dem Sensor und dem Pixelabstand | Good across the corrected 50mm-500mm range | Often more forgiving due to iris control and finite conjugate correction |
| Very close range (<100mm) | Hohes Risiko. Ohne Laborversuche nicht zu empfehlen. | Supported from 50mm; bench-verify corners at the exact WD | Also strong; verify conjugate match. |
Objektive nach Arbeitsabstandsbereich
Representative Commonlands lenses for short and medium working distances in machine vision and robotics applications.
Die besten Objektive nach Arbeitsabstand
The right pick depends on the focal length the distance requires and on whether the job needs iris control for depth of field. The table pairs each working distance range with a Commonlands lens whose focus range covers it, split by mount. Detailed cards follow below.
| Arbeitsabstandsbereich | Empfohlenes Objektiv | Montage | Fokusbereich / Blende | Warum diese Wahl? |
|---|---|---|---|---|
| Short (50mm-500mm) wide field, 2/3" sensors |
CIL064 6mm | M12 | Finite conjugate, F/2.9, 11.0mm image circle | Finite conjugate correction reduces field curvature at close range; widest field of the three. |
| Short (50mm-500mm) narrower field |
CIL142 14.4mm | M12 | Finite conjugate, F/2.6-F/5.2 variants, 9.3mm image circle | Mid-telephoto framing with the same reduced field curvature across the 50mm-500mm range. |
| Short (50mm-500mm) 500mm design point |
CIL121 21,8 mm | M12 | Finite conjugate, corrected at 500mm | Die Aberrationskorrektur ist auf eine kürzere Konjugateinstellung ausgelegt, sodass die Bildecken scharf bleiben, während das M12 mit langer Konjugateinstellung hier eine Unschärfe aufweist. |
| Mittlere, mehrere hundert mm -Blende und Schärfentiefesteuerung |
CIL532 12 mm | C-Mount | Endliche Konjugation ab 100 mm, F/2,0–F/16 | Ring-adjustable focus across the range, with an iris to tune depth of field. |
| Mittlere Brennweite, mehrere hundert mm , großes Sichtfeld, geringe Verzeichnung |
CIL062 6 mm | M12 | Build-dependent; confirm per assembly | Verzerrungsarmes Weitwinkelobjektiv für Messungen bei Standard-Prüfabständen in einem kompakten M12-Gehäuse. |
Each range starts from the focal length the working distance requires (confirm it with the EFL calculator), then the mount follows from whether depth of field needs iris tuning. Iris values are each SKU's published figures; focus ranges are Commonlands catalog guidance, confirmed for your sensor and holder on request. Bench-test full-field sharpness on your own sensor before ordering. The focal length selection guide covers the full method.
Short working distance: finite conjugate M12 lenses
Mittlerer Arbeitsabstand (mehrere hundert mm)
Häufig gestellte Fragen
Common questions on working distance and MOD for Commonlands machine vision and robotics lenses.
Was versteht man unter „Arbeitsabstand“ in der Bildverarbeitung und Robotik?
Der Arbeitsabstand ist der Abstand zwischen der Vorderseite des Objektivgehäuses und der Zielfläche. In der industriellen Bildverarbeitung wird er in der Regel durch die Geometrie des Maschinenrahmens oder des Förderbands bestimmt. In der Robotik ergibt er sich aus der Reichweite des Arms, der Bauweise des Endeffektors oder der Tiefe des Behälterns. Der Arbeitsabstand ist ein Konstruktionsaspekt auf Systemebene. Zu Beginn eines Projekts besteht möglicherweise noch Spielraum für Anpassungen, doch sobald die mechanische Konstruktion feststeht, muss das Objektiv bei diesem Abstand die geforderte Leistung erbringen.
Was ist die minimale Objektentfernung und wie unterscheidet sie sich vom Arbeitsabstand?
Minimum object distance (MOD) is the closest distance at which a lens can focus in the center of the image, measured from the front of the lens to the object. WD is also measured from the front of the lens. The key difference: WD is a system-level design choice, while MOD is a lens characteristic.
On an adjustable C-mount lens, MOD is a hard limit set by the end of focus travel; fixed-focus designs fix it at manufacture. M12 lenses have no such stop, but thread engagement, rear-element and sensor clearance, and the aberrations that grow off the design conjugate still set a limit, and the center can fail before the corners do. Not all lens datasheets publish MOD, so you may need to verify it experimentally.
Warum sind die Bildecken bei geringem Arbeitsabstand unscharf?
This is usually an off-axis aberration issue, most commonly field curvature and/or astigmatism when the lens is used far from its design conjugate. Many standard M12 lenses are infinite conjugate designs, optimized for longer working distances, and because they focus as a rigid body (no internal focusing mechanism), there is no aberration rebalancing as you thread them closer.
How badly corners degrade depends on the individual lens design. Two lenses with similar specs can perform differently at the same distance. At short working distances, bench-test multiple candidates. If none pass, try a finite conjugate M12 (CIL121) or a C-mount lens; short-range behavior differs per design, so test the one you pick.
Sollte ich bei kurzen Arbeitsabständen M12 oder C-Mount verwenden?
Both can work. The question is which one best fits your mechanical and optical constraints. Commonlands C-mount lenses offer a focus ring and an adjustable iris for depth-of-field control; the moving elements and near-limit behavior vary by design, so confirm them with Commonlands engineering. M12 lenses are simpler, lighter, and smaller, which matters for embedded robotics and space-constrained applications. If you need M12 at short WD, test 2-3 candidates because field quality varies between designs. The CIL121 is an M12 lens specifically optimized for a 500mm working distance.
Kann der Fokusbereich durch Zwischenringe oder eine Anpassung der Halterung erweitert werden?
Yes. C-mount extension tubes increase the lens-to-sensor distance and shift the focus range closer. For M12, threading the lens farther out of the holder does the same. A taller holder just maintains thread engagement. Tradeoffs: the far focus limit moves in and FOV changes. For C-mount, extension tubes work the lens outside its designed focus range; image quality there is product-specific, so test it. For M12, extension can recover center focus within clearance limits, but it corrects no aberration. If corners are soft, a different lens design is needed.
Finden Sie das richtige Objektiv für Ihren Arbeitsabstand
Commonlands can confirm working distance, MOD, or finite conjugate correction for any of its machine vision lenses on request. If nothing in the standard range fits your inspection station or robot cell, our San Diego engineering team can review application-specific configurations. Same-day shipping on orders placed before 12 PM PT.