How to Use One Line Scan Camera Lens Across Multiple Product Widths: FOV, Resolution and Machine Changeover Guide

Industrial inspection machines rarely process only one fixed product width throughout their service life. A flexible packaging line may run several film widths, a textile inspection machine may handle different fabric rolls, a printing machine may switch between narrow and wide substrates, and a metal strip inspection system may process multiple coil sizes. For OEMs, this creates an important optical design question: can one line scan camera lens be used across multiple product widths without changing the lens every time the machine changes format? In many systems the answer is yes, but only when the widest product, required field of view, smallest defect, sensor resolution, working distance and acceptable resolution loss on narrower products are considered together.

Using one line scan camera lens across several product widths can simplify machine design, reduce spare-part requirements and make production changeovers more repeatable. However, one fixed optical configuration cannot automatically provide the same pixels per millimetre on every width. If a lens is configured to cover the widest material and the camera remains in the same position, narrower products occupy fewer pixels across the sensor unless the optical geometry is changed. The OEM must therefore decide whether to keep the FOV fixed, reposition the camera or lens assembly, or define different inspection recipes while preserving one lens.

The current Kyptec Automation® Line Scan Camera Lens collection contains dedicated 25 mm, 35 mm and 50 mm focal-length options for high-resolution continuous inspection. The 25 mm product page specifies compatibility with 4K 7 μm and 8K 3.5 μm line-scan systems, an M42 mount and an F2.8–22 aperture range, while Kyptec Automation® describes its line scan lenses as engineered for uniform illumination, minimal distortion and consistent sharpness across the field of view. This focused range gives OEMs several practical geometries for standardizing inspection machines that must accommodate changing product widths.

Why Multiple Product Widths Create a Different Lens-Selection Problem

Selecting a line scan lens for one fixed web width is comparatively straightforward. The engineer defines required inspection width, sensor length, smallest defect and working distance, then selects an appropriate focal length. A multi-width machine introduces an additional requirement: the optical system must remain useful after the material width changes.

Imagine one machine that processes 400 mm, 600 mm and 800 mm products. If the camera and lens are permanently configured for an 850 mm FOV so the widest product plus lateral tolerance always fits, all three products can be inspected without moving the optical assembly. This is mechanically simple, but a 400 mm product occupies less than half of the available object field. The camera still has the same number of pixels, so much of the sensor is viewing unused space.

The central design question therefore becomes whether the resolution available on the narrowest product remains sufficient for its smallest required defect.

Fixed FOV Is the Simplest Changeover Strategy

The simplest way to use one line scan camera lens across multiple widths is to design the FOV around the largest product the machine will ever process. Once working distance, focus and lens position are established, the imaging assembly remains fixed.

When a narrower product enters production, software can restrict inspection to the region occupied by that product while the optical FOV remains unchanged. This approach avoids mechanical repositioning and preserves the same lens calibration.

For production machines with frequent format changes, fixed FOV can make changeover significantly easier because operators do not need to refocus or physically reposition the camera each time material width changes.

The trade-off is that the narrower product does not use all of the available sensor width efficiently.

Why Pixels per Millimetre Must Be Calculated for Every Product Width

A practical resolution relationship is:

Pixels per millimetre = active sensor pixels ÷ inspected object width

For an 8K camera with approximately 8,192 active pixels covering an 800 mm fixed FOV, the cross-web sampling is about:

8,192 ÷ 800 ≈ 10.24 pixels/mm

If a 400 mm product is inspected while the optical FOV remains 800 mm, the image scale remains 10.24 pixels/mm because the optics have not changed. The 400 mm product simply occupies about 4,096 sensor pixels.

This is an important distinction. Cropping the software region does not improve optical sampling density. It only tells the inspection system to ignore unused pixels.

If the narrow product needs substantially finer defect detection than the wide product, a fixed FOV may therefore be inadequate even though both products fit inside the image.

Software ROI Does Not Change Optical Magnification

Region of interest, or ROI, is useful during machine changeover because it allows the inspection software to process only the portion of the scan line containing the product. However, ROI cropping does not alter focal length, magnification, working distance or pixels per millimetre.

This is one of the most important concepts for OEM buyers evaluating a single line scan lens for multiple web widths.

If a narrow 300 mm product occupies only part of an 800 mm FOV, selecting that 300 mm portion in software does not give the sensor the resolution it would have had if the optical system itself were adjusted to make 300 mm fill the sensor.

The advantage of software ROI is operational simplicity, not increased optical resolution.

When One Fixed Lens Can Cover All Product Widths Successfully

One fixed lens configuration is most suitable when the smallest required defect remains comfortably detectable at the FOV needed for the widest product.

Suppose the widest product is 1,000 mm and an 8K system provides approximately 8.19 pixels/mm. If the inspection specification requires a 1 mm defect to span several pixels, the available sampling may provide sufficient margin. Narrower products can then run within the same fixed optical setup without losing the established pixels-per-millimetre value.

This is a strong architecture for web inspection machines, textile inspection equipment, printing inspection machines and flexible packaging lines where the product width changes frequently but the minimum defect specification does not become much more demanding for narrower formats.

Kyptec Automation® identifies line scan lenses as suitable for continuous materials such as sheets, films and textiles, while its current product range is positioned for high-speed inspection and stable imaging across large inspection areas.

When Changing Working Distance Can Improve Resolution on Narrow Products

A second strategy is to keep the same line scan camera lens but mechanically change the camera-to-product distance during format changeover.

Moving the lens closer to a narrower product can reduce the FOV and increase optical magnification, allowing more sensor pixels to be used across that product. The benefit is higher pixels per millimetre without replacing the lens.

However, this approach adds mechanical complexity. Each working-distance position must be repeatable, the lens may need refocusing, and calibration should be validated for every defined product width.

For machines that change width infrequently, this can be a reasonable compromise. For machines changing format several times per shift, a fixed optical position may be more practical.

Product Width Changeover Should Be Designed as a Repeatable Recipe

An OEM should avoid requiring operators to adjust a camera “until the image looks right.” Instead, each supported product width should have a documented optical and inspection recipe.

For a fixed-FOV machine, the recipe may contain product centre position, ROI boundaries and defect thresholds. For an adjustable optical system, it may also include camera position, working distance, focus reference and calibration values.

This approach turns variable-width inspection from a manual optical adjustment into a controlled production process.

The best machine architecture is usually the one that minimizes operator-dependent optical changes while still providing enough resolution for every product family.

Kyptec Automation® KL-1402 for Compact Multi-Width Inspection Machines

The Kyptec Automation® KL-1402 25 MM Line Scan Camera Lens is particularly relevant where an OEM must accommodate comparatively wide product coverage inside limited machine height. Its current product page lists a 25 mm focal length, M42 mount and support for 4K 7 μm and 8K 3.5 μm line-scan configurations.

In a compact label inspection machine, flexible-film inspection system or textile machine, the shorter focal length can provide a useful starting geometry where the widest product must fit inside a restricted stand-off.

The OEM should still calculate the effective pixels per millimetre at the maximum FOV before deciding that the same optical setup can support every narrower product.

Why Designing Around the Widest Product Is Usually the Safest Starting Point

A multi-width inspection system normally has to guarantee that the widest product fits inside the usable optical field with adequate lateral tolerance. If the FOV is designed only around a typical product width, the widest format may later require emergency changes to camera height or focal length.

Starting with the maximum material width establishes the worst-case coverage requirement.

The next question is then whether resolution at that width satisfies the minimum defect requirement. If it does, using one fixed lens across all smaller products becomes much easier.

If it does not, the OEM must consider variable working distance, a higher-resolution sensor, a different optical geometry or multiple imaging channels rather than assuming software cropping can solve the problem.

Different Product Widths May Also Have Different Defect Specifications

It is dangerous to assume that one pixels-per-millimetre target applies to every format merely because all widths are processed on the same machine.

A 1,000 mm industrial web may require detection of 1 mm defects, while a 300 mm premium printed product may require detection of 0.2 mm defects. The narrower material therefore has a more demanding optical requirement despite being easier to fit within the field.

This is where a multi-width inspection matrix becomes useful. For each product, the OEM should document width, smallest defect, required pixels per defect and whether dimensional measurement is also required.

The lens architecture should then be approved against the most demanding combination rather than the widest product alone.

Fixed Camera Position Versus Adjustable Camera Position

A fixed camera position offers stronger mechanical repeatability. Once alignment, focus and calibration are validated, production changeover can happen mainly through software.

An adjustable camera position offers better utilization of sensor resolution across widely different products because the optical FOV can be changed to fit each width more tightly.

Neither strategy is universally superior. Frequent-changeover production generally benefits from fixed geometry, while machines processing a few highly different product families may justify repeatable mechanical positions.

The buyer should therefore consider changeover frequency as part of lens selection, not only width range.

Kyptec Automation® KL-1404 for Balanced Width and Stand-Off Requirements

The 35 mm option in the Kyptec Automation® Line Scan Camera Lens collection provides an intermediate focal-length geometry between the 25 mm and 50 mm models. The collection confirms that Kyptec Automation® currently offers all three focal lengths as dedicated line-scan lenses suitable for 4K and 8K cameras.

Kyptec Automation® KL-1404 can therefore be evaluated in printing inspection machines, battery electrode inspection equipment or medium-width web systems where the OEM needs one standardized lens but has more available working distance than a highly compact 25 mm configuration.

Using one intermediate focal length across several machine recipes can also simplify OEM inventory when the entire supported width range remains inside a practical FOV window.

Why Lens Re-Focusing Should Be Avoided During Routine Changeover When Possible

Every manual focus adjustment introduces the possibility of operator variation. If a machine can support all required product widths while keeping the same lens position and focus setting, this usually provides the most repeatable production behaviour.

If mechanical movement is necessary, the system should use repeatable position references rather than subjective adjustment.

This becomes increasingly important with 8K 3.5 μm line-scan systems because small focus errors can affect the fine-detail contrast that the smaller pixels are intended to capture.

Kyptec Automation®'s 25 mm product is explicitly published for both 4K 7 μm and 8K 3.5 μm configurations, reinforcing the need to treat focus repeatability as part of high-resolution machine design.

Product Lateral Position Must Be Included in the Maximum FOV

A 600 mm product does not necessarily require exactly 600 mm of FOV. Real machines have web tracking tolerance, edge wander and mechanical alignment variation.

If the product can shift ±10 mm sideways, a minimum practical FOV may need to exceed the nominal width by at least the required tracking allowance.

This becomes even more important when several product widths share one fixed optical configuration because the widest product usually leaves the least remaining field margin.

The OEM should therefore distinguish nominal product width from required inspection FOV.

Resolution on Narrow Products Can Be Improved Without Changing the Lens Model

Using one lens across different widths does not necessarily mean the entire optical assembly must remain stationary. If the lens has sufficient usable focus range and the machine provides repeatable movement, an OEM can preserve the same lens model while changing working distance for different product families.

This can be attractive for a machine builder trying to standardize one optical component across several variants.

However, every alternative geometry must still be validated independently for FOV, edge sharpness, distortion, focus and minimum-defect detection.

Standardizing the lens should simplify the machine, not create an uncontrolled collection of field adjustments.

Kyptec Automation® KL-1406 for Larger Machine Frames

Where the machine provides greater stand-off, the Kyptec Automation® KL-1406 50 MM Line Scan Camera Lens can be considered as the longer focal-length geometry within the same Kyptec Automation® line scan portfolio. The current collection identifies the 50 mm model alongside the 25 mm and 35 mm options for 4K and 8K line-scan cameras.

This can suit metal strip inspection machines, large sheet inspection systems and other rigid wide-material platforms where the camera can remain farther from the production surface.

If several strip widths are processed on the same machine, one 50 mm lens may remain fixed when maximum FOV already provides sufficient resolution, or the camera assembly can use predefined positions if narrower widths require higher magnification.

Example: Flexible Packaging Machine With 400 mm, 600 mm and 800 mm Webs

Consider an 8K flexible packaging inspection machine that must run three common web widths. If the system is designed around an 840 mm FOV to accommodate the 800 mm web plus lateral tolerance, optical sampling is approximately:

8,192 ÷ 840 ≈ 9.75 pixels/mm

A 0.5 mm defect therefore spans approximately 4.9 pixels in the cross-web direction.

If this sampling is sufficient for every product family, the strongest operational design may be to leave the camera and lens fixed and change only the inspection ROI for 400 mm and 600 mm products.

The narrower webs will not gain additional optical magnification, but changeover becomes fast and repeatable.

Example: Printing Machine With Different Resolution Requirements

Now consider a printing inspection machine that processes an 800 mm general-printing product and a 300 mm premium label product. The wide product requires detection of 1 mm defects, while the narrow product requires registration evaluation at approximately 0.2 mm.

A fixed 850 mm FOV may comfortably inspect the wide product but provide insufficient sampling for the narrow high-precision requirement.

In this case, using the same line scan camera lens may still be possible, but the narrow-product recipe could require a controlled change in working distance so the 300 mm product occupies more of the sensor.

This is a good example of why product width alone should never determine the changeover strategy.

Example: Metal Strip Inspection With Several Coil Widths

A metal processing machine may inspect 300 mm, 600 mm and 1,000 mm strip widths while maintaining a similar minimum scratch specification.

If the 1,000 mm configuration provides enough pixels per millimetre for the specified defect, the narrower materials can often remain within the same optical geometry.

In this situation, a fixed lens and fixed camera position may provide better production stability than repeatedly moving the imaging system.

For larger mechanical frames, the 50 mm Kyptec Automation® option can be evaluated where the required FOV and stand-off suit that geometry. The brand's line scan portfolio is designed around continuous high-precision inspection, making this type of repeatable OEM deployment a natural use case.

Frequently Asked Questions About Using One Line Scan Lens Across Multiple Product Widths

1. Can one line scan camera lens inspect different product widths?

Yes, provided the lens and camera geometry can cover the widest product while still delivering enough resolution for the smallest defect required across every product family. Narrower products can usually be handled with software ROI or, where necessary, a repeatable change in working distance.

2. Do I need to change the lens every time the web width changes?

Not necessarily. A well-designed machine can often use one fixed focal-length lens across multiple widths. Lens replacement should generally be considered only when the required FOV and resolution ranges are too different for one practical optical geometry.

3. Does cropping the image improve resolution on a narrower product?

No. Software cropping removes unused image regions but does not increase optical magnification or pixels per millimetre. To gain more object-side sampling, the optical FOV itself must become narrower.

4. Should I size the lens FOV for the widest product?

Usually yes. The maximum product width plus realistic lateral movement tolerance provides a safe starting point. The engineer should then verify that this maximum FOV still provides adequate pixels per millimetre for all required defects.

5. What happens to unused camera pixels on a narrow web?

They simply image regions outside the product. Software can ignore those pixels using ROI settings, but their presence does not increase the resolution of the product region.

6. Can changing working distance let me use the same lens on a narrower product?

Yes. Repositioning the camera closer can reduce FOV and increase magnification, allowing more sensor pixels to cover the narrower product. The new position should be repeatable and fully recalibrated rather than adjusted manually by eye.

7. Is fixed FOV better for frequent production changeovers?

Often yes. A fixed optical setup minimizes operator adjustment and preserves focus and calibration. If the maximum-width configuration already provides adequate resolution for every product, fixed FOV is usually a highly practical OEM strategy.

8. When is an adjustable camera position better?

Adjustable geometry becomes useful when product widths differ substantially and narrower products require much finer defect detection. The camera can then move to predefined positions while retaining the same line scan camera lens.

9. Can the same 8K line scan lens be used for 300 mm and 1,000 mm products?

Potentially, but the real issue is not simply width. The smallest defect required on each product determines whether the same fixed FOV is acceptable. A 300 mm product with extremely fine defects may require a narrower optical FOV even though it physically fits easily.

10. Should focus be changed every time product width changes?

Not if the camera and lens remain in the same physical position. If working distance changes during changeover, focus may need to be reset and validated. Wherever possible, OEMs should use predefined and repeatable settings rather than subjective manual focusing.

11. How much extra FOV should I allow beyond the maximum product width?

The required margin depends on web tracking, product positioning and mechanical tolerances. The FOV should include enough allowance so the product cannot move outside the inspected field during normal production.

12. Can one focal length be standardized across an entire machine family?

Yes, when the machine variants have compatible sensor lengths, FOV requirements and working-distance ranges. Kyptec Automation® offers 25 mm, 35 mm and 50 mm dedicated line scan camera lens options, allowing OEMs to select the focal-length family that best fits their machine platform rather than changing optics unnecessarily.

13. Which Kyptec Automation® line scan lens is suitable when machine height is limited?

Kyptec Automation® KL-1402 25 MM is the shorter focal-length option in the current range and can be evaluated where relatively wide coverage is required within a compact machine layout. Its product page specifies M42 mounting and 4K 7 μm / 8K 3.5 μm compatibility.

14. Is a 35 mm line scan lens a good compromise for changing web widths?

It can be when the required FOV and available stand-off fall between compact 25 mm and longer 50 mm geometries. The correct choice should still be determined from maximum width, sensor size and smallest defect rather than treating 35 mm as a universal compromise.

15. When should I use a 50 mm line scan lens for multiple product widths?

A 50 mm focal length is worth evaluating when the machine provides greater stand-off and the required FOV can be achieved within that geometry. Large sheet, strip and rigid-material inspection machines are common examples where longer working distance may be useful.

16. What should an OEM specify before choosing one lens for several product widths?

Provide every supported product width, maximum lateral position tolerance, camera pixel count, pixel pitch, sensor length, available working-distance range and smallest required defect for each product family. These parameters allow the Kyptec Automation® Line Scan Camera Lens collection to be evaluated as a multi-format machine solution instead of selecting a lens only for one nominal width.

Conclusion

Using one line scan camera lens across multiple product widths is entirely practical when the optical system is designed around more than the widest material alone. The OEM must consider the relationship between maximum FOV, sensor resolution, pixels per millimetre, smallest required defect, working distance and changeover frequency. A fixed lens and fixed FOV provide the simplest and most repeatable production architecture when the widest-field configuration already delivers sufficient defect resolution. Narrower products can then be handled through software ROI without disturbing focus or calibration.

When narrower products demand substantially finer inspection, the same lens may still be retained while the camera moves to a predefined working-distance position that reduces FOV and increases optical magnification. This approach can preserve lens standardization while improving utilization of the sensor, but each optical position must be repeatable and independently validated.

The Kyptec Automation® Line Scan Camera Lens portfolio provides 25 mm, 35 mm and 50 mm focal-length choices for 4K and 8K line-scan camera applications, giving OEMs practical flexibility when designing machines for different product widths and mechanical envelopes. For flexible packaging machines, printing inspection systems, textile inspection equipment, battery electrode machines and metal strip inspection lines, selecting one well-matched Kyptec Automation® line scan camera lens and engineering the changeover strategy around real FOV and resolution requirements can create a simpler, more repeatable and easier-to-maintain inspection platform without sacrificing the defect-detection capability required across the complete product range.