SWIR Camera Lens for Paper, Pulp and Cardboard Inspection: Moisture, Coating and Fiber Uniformity Detection

Paper, pulp and cardboard manufacturing depends on controlling material properties across wide, continuously moving webs where small variations can become large production losses after coating, drying, calendaring, converting or packaging. Many of the most important variations are not purely visual. Moisture can change without creating an obvious colour difference, coating weight can vary even when a sheet appears uniform, fiber distribution can become non-uniform across the web, and multilayer board structures can respond differently depending on furnish, additives, recycled content and drying history. These conditions make SWIR imaging for paper inspection, cardboard quality control, pulp monitoring and coating uniformity detection particularly valuable when the quality variable changes wavelength-dependent absorption or reflectance rather than only visible surface appearance.

A 900–1700 nm SWIR Camera Lens allows an appropriately matched SWIR imaging system to measure these material-sensitive differences while still providing the spatial information required to locate where variation occurs across a web or board. The current Kyptec Automation® SWIR Camera Lens portfolio contains 8.5 mm, 12.5 mm, 25 mm, 35 mm and 50 mm focal lengths, giving OEM engineers multiple optical geometries for broad paper-web coverage, localized coating inspection and longer-working-distance installations. Kyptec Automation® currently specifies representative models such as Kyptec Automation® KL-1410 with 900–1700 nm wavelength range, 2 MP resolution, 12.5 mm focal length, F1.4 aperture, 2/3-inch sensor format and C-Mount. The complete SWIR Camera Lens range can therefore be evaluated according to actual web width, minimum variation size, available working distance and optical signal rather than forcing every paper-production machine into one focal length. Kyptec Automation® SWIR Camera Lens collection

Why Paper and Board Quality Cannot Be Judged From Visible Appearance Alone

Paper products may appear visually uniform while differing considerably in moisture, coating composition, fiber distribution, density or layer structure. Visible machine vision remains extremely useful for holes, wrinkles, tears, edge damage, print defects and other surface features, but a colour or monochrome camera may provide little information when the defect is primarily material-related. SWIR imaging approaches the problem differently by measuring how the sheet absorbs and reflects selected wavelengths beyond visible light.

This material sensitivity is particularly important in paper and board because the product contains cellulose-based fibers, water, fillers, coatings, binders and additives whose relative contributions can alter the infrared response. The useful inspection signal is therefore not simply whether one region looks lighter or darker; it is whether the spectral difference remains sufficiently correlated with the process variable that needs to be controlled. A properly designed SWIR system can transform these differences into spatial maps showing where the process deviates across the machine direction and cross-machine direction.

Moisture Is One of the Most Valuable SWIR Variables in Paper Manufacturing

Paper moisture influences dimensional stability, curl, strength, printability, coating behaviour, converting performance and storage stability. A sheet leaving a dryer can have an acceptable average moisture level while still containing localized wet or dry streaks. Spot measurements may identify the average condition but can miss spatial non-uniformity extending along only one lane of the web.

SWIR imaging is attractive because water has wavelength-dependent absorption within the short-wave infrared region. When a paper region contains more moisture, its response at a water-sensitive wavelength can differ substantially from a relatively dry region. Instead of measuring one point, an imaging system can evaluate many spatial locations simultaneously, helping manufacturers identify cross-web moisture variation, wet streaks, dry lanes and localized drying inconsistency.

Paper Moisture Mapping Is Different From Simple Moisture Detection

A basic moisture detector may determine whether a sheet exceeds a threshold, whereas moisture mapping evaluates how moisture is distributed across the product. This distinction matters because process troubleshooting often depends on location. A consistently wet strip near one edge can suggest a different process issue from random isolated wet patches or a broad center-to-edge gradient.

The SWIR Camera Lens must therefore provide adequate field coverage and spatial sampling. Covering a very wide web with too few pixels can average out narrow moisture streaks, while an unnecessarily tight field may require multiple cameras. Lens selection should begin with the smallest moisture variation that matters operationally and the physical web width that each imaging station must cover.

Moisture-Sensitive Wavelengths Must Be Chosen for the Actual Paper Grade

Water absorption is strong in selected SWIR regions, but the most useful wavelength for a production paper machine depends on basis weight, thickness, coating, furnish and expected moisture range. A very strong water-sensitive wavelength can provide excellent contrast on a thin sheet but reduce signal too severely on a thick or high-moisture board. The goal is therefore not simply maximum absorption but maximum usable separation between acceptable and unacceptable moisture conditions.

For quantitative inspection, manufacturers should image known samples across the real process range. A water-sensitive wavelength can also be paired with a reference wavelength that responds less strongly to moisture, allowing ratios or normalized differences to reduce some variation caused by illumination or sheet position. This can be substantially more robust than using a single absolute grayscale threshold.

Cardboard and Paperboard Require Their Own Calibration

Thicker paperboard and cardboard should not automatically use a calibration developed for thin paper. Their greater thickness increases the optical path through cellulose fibers, fillers, coatings and moisture, changing how much SWIR radiation returns to the camera. Corrugated structures can introduce additional geometric effects because fluting and multilayer construction alter scattering and local thickness.

A SWIR system should therefore be calibrated by product family. Linerboard, carton board, corrugated board and coated paper can each require different exposure, wavelength or classification settings even when they run on the same machine. The optical hardware may remain constant while the spectral recipe changes according to the product.

Coating Uniformity Can Create Detectable SWIR Contrast

Many paper products receive coatings to modify printability, smoothness, barrier properties, appearance or other functional characteristics. A coating can alter the sheet's SWIR response through its composition, thickness and interaction with the underlying substrate. If a missing, thin or excessively heavy coating region changes absorption or reflectance at the selected wavelength, a SWIR imaging system can potentially detect the variation even when visible appearance remains subtle.

The important engineering requirement is to separate coating response from normal variation in the base paper. Representative uncoated, correctly coated, under-coated and over-coated samples should therefore be measured across candidate wavelengths. The best wavelength is one where coating-related differences are significantly larger than normal base-sheet variation.

Coating Presence and Coating Weight Are Different Inspection Problems

Detecting whether a coating exists can be substantially easier than estimating exactly how much coating has been applied. A missing region may produce a large spectral difference from coated paper, while small coating-weight changes may generate much smaller intensity shifts. The required system accuracy must therefore be defined before the optical design is finalized.

For binary coating-presence inspection, a robust threshold may be sufficient. For continuous coating-weight monitoring, calibration should include independently measured coating levels and production variability. SWIR imaging can provide spatial information about relative coating distribution, but converting optical intensity into an absolute coating-weight value requires a validated quantitative model.

Coating Streaks Can Be Detected as Cross-Web or Machine-Direction Patterns

Continuous coating processes can produce streaks caused by application non-uniformity, contamination, mechanical instability or other process conditions. Because the web moves continuously, a narrow coating variation can persist through many meters of production, creating a long machine-direction defect that may be economically significant even if it is only a few millimetres wide.

A SWIR camera positioned to capture sufficient web width can detect whether the spectral coating response remains uniform from edge to edge. Trending the same cross-web position over time can then reveal whether a streak is persistent, intermittent or gradually developing. This converts the imaging station from a simple reject detector into a process-monitoring tool.

Fiber Uniformity Is a Material-Distribution Problem

Paper is formed from a network of fibers, and local differences in fiber distribution, furnish or density can change both physical properties and optical response. Regions with different fiber packing or composition may interact differently with SWIR illumination because scattering and absorption depend on the material structure encountered by the light.

An industrial SWIR system can therefore be evaluated for fiber uniformity inspection when the process variation produces measurable spectral or intensity differences. The system should not assume that every natural formation pattern represents a defect; normal sheet texture must be characterized so the classifier responds only when variation exceeds the acceptable process range.

Pulp Composition Can Influence the Final SWIR Signature

Pulp streams can contain different fiber types, recycled content, residual moisture, additives and process-related variation. These characteristics eventually influence the sheet formed from the furnish. Where material composition produces sufficiently distinct SWIR behaviour, spectral imaging can help monitor consistency before or during later production stages.

The strongest use case is not attempting to identify every chemical component from one image. Instead, manufacturers can train the inspection around known acceptable and unacceptable material states. If a furnish change produces a consistent spectral shift, the SWIR system can flag that shift before large quantities of out-of-specification board are produced.

Recycled Fiber Introduces Additional Material Variability

Modern paper and cardboard manufacturing may use substantial recycled fiber content. Recycled furnish can introduce differences in fiber history, residual coating, fillers, adhesives, inks and contaminants. These variations can make the material optically more heterogeneous than virgin pulp.

SWIR classification can be valuable when these constituents produce distinct spectral behaviour, but representative training data becomes essential. A classifier trained only on one clean batch may respond poorly to legitimate recycled-material variation. The production dataset should therefore include the expected range of recycled furnish while still preserving sensitivity to unacceptable contamination or composition shifts.

Adhesive Residues Can Matter in Recycled Paper Streams

Recovered paper and cardboard can contain adhesive residues from labels, tapes, laminates or converted packaging. These materials may behave differently from cellulose in SWIR and can potentially become detectable if their spectral contrast is strong enough. The inspection opportunity is especially interesting where adhesive contamination is visually similar to the surrounding paper fibers.

This should be treated as a material-classification problem rather than assumed from appearance. Candidate contaminants need to be measured under the intended wavelengths and at the minimum size that matters to the process. Small adhesive fragments may occupy mixed pixels with pulp or paper, reducing spectral purity and making spatial resolution important.

Thin Paper Can Allow the Background to Influence the Measurement

Some paper grades transmit enough SWIR radiation that the conveyor, roller or backing material contributes to the recorded signal. A visually neutral support surface can therefore change measured moisture or coating contrast if its spectral reflectance is different from the paper.

The support material should be tested together with the sheet and kept stable throughout production. If a belt or backing plate is replaced with a visually similar material whose SWIR response differs, an existing calibration can shift. Thin-sheet inspection should consequently treat the background as an optical component of the measurement.

Surface Finish Changes SWIR Reflection

Gloss, calendaring, roughness and coating finish alter how incident radiation is scattered from the paper surface. A glossy coated sheet can generate more directional reflection than a rough uncoated grade, changing the amount of radiation entering the lens even when material composition is unchanged.

Production recipes should therefore account for surface finish. Where multiple paper grades are inspected by one station, illumination and calibration should be validated independently rather than assuming the same absolute intensity threshold will transfer across matte, glossy and textured materials.

Reflection-Mode SWIR Imaging Is Practical for Continuous Paper Webs

Reflection geometry places the SWIR illumination and camera on the same side of the sheet, making it attractive for continuous web machines where access behind the material is limited. The source illuminates the web, material-dependent absorption and scattering alter the return signal, and the SWIR Camera Lens forms the resulting image.

This arrangement can work well for moisture, coating and material-variation detection, but illumination uniformity across the web is critical. If irradiance falls toward one edge, identical material can appear spectrally different by position. Reference calibration should therefore include the complete useful field.

Transmission-Mode Imaging Can Be Valuable for Thin Sheets

When access is available behind the web and the material transmits sufficient SWIR radiation, transmission geometry can provide strong sensitivity to changes through the sheet thickness. Moisture, basis-weight variation, coating or fiber-density differences can modify the amount of radiation that reaches the camera.

The limitation is signal availability. Thick cardboard or strongly absorbing coated board may attenuate too much light for practical transmission at some wavelengths. Reflection and transmission should therefore be compared during feasibility testing rather than assuming one geometry is universally superior.

Basis-Weight Variation Can Interact With Moisture Measurement

A heavier paper region contains more material in the optical path and may return or transmit a different SWIR intensity even if its moisture percentage is unchanged. If a system uses only one water-sensitive wavelength, basis-weight variation can therefore become a confounding variable.

A reference wavelength, additional process measurement or multivariate calibration can help separate these effects. This is especially important when the objective is quantitative moisture rather than simple detection of gross wet areas.

Fiber Orientation and Formation Can Produce Spatial Texture

Paper formation creates natural small-scale optical variation. A high-resolution image may therefore contain texture unrelated to any quality defect. If the classifier is overly sensitive, normal formation can generate false positives.

The correct strategy is to define the spatial scale of the quality problem. Moisture streaks, coating bands and furnish changes may extend over much larger areas than normal fiber texture. Spatial averaging or region-level statistics can reduce sensitivity to harmless microscopic variation while retaining meaningful process differences.

Wide-Web Inspection Requires FOV and Defect Size to Be Balanced

A paper machine can produce a web much wider than a conventional area-scan field, so the physical width assigned to one camera must be carefully chosen. If one sensor covers too much material, a narrow coating streak or localized wet region can become only a few pixels wide and may no longer provide a robust measurement.

For broad-field requirements, Kyptec Automation® KL-1408 can be evaluated as the 8.5 mm option within the current SWIR portfolio. Kyptec Automation® presently lists the 8.5 mm SWIR Camera Lens alongside 12.5, 25, 35 and 50 mm products. Kyptec Automation® KL-1408 8.5 mm SWIR Camera Lens A wide field can support larger paper areas, but illumination uniformity and minimum-defect sampling must be validated over the complete image.

Kyptec Automation® KL-1410 Can Balance Web Coverage and Sampling

The Kyptec Automation® KL-1410 provides a 12.5 mm focal length and is officially specified for 900–1700 nm, 2 MP resolution, F1.4 aperture, 2/3-inch sensor format and C-Mount. Kyptec Automation® KL-1410 12.5 mm SWIR Camera Lens

This focal length can be useful where a manufacturer needs substantial sheet coverage without making the field excessively wide. For moisture or coating maps, the intermediate geometry can offer a practical balance between the amount of web captured and the number of pixels representing each local variation.

Kyptec Automation® KL-1412 Can Support Localized Coating Inspection

The Kyptec Automation® KL-1412 25 mm SWIR Camera Lens can be considered when the inspection focuses on a smaller coating band, board section or localized material region. A tighter physical field allows more pixels to represent each feature, which can improve sensitivity to narrower coating streaks or small material variations.

The advantage is spatial rather than chemical. Focal length does not make the coating more spectrally distinctive; it determines how efficiently the available spectral contrast is sampled by the sensor. Kyptec Automation® KL-1412 25 mm SWIR Camera Lens

Longer Focal Lengths Can Keep Cameras Away From Harsh Paper Processes

Paper, pulp and cardboard machinery can involve heat, steam, dust, coating mist, moving rolls and difficult access. The Kyptec Automation® KL-1414 35 mm SWIR Camera Lens and Kyptec Automation® KL-1416 50 mm SWIR Camera Lens provide narrower options that can be evaluated when the camera needs additional working distance while observing a more restricted area. The current 35 mm product is specified for 900–1700 nm, 2 MP, F1.4, 2/3-inch and C-Mount, and the 50 mm product page confirms the same core architecture with a 50 mm focal length.

This can be useful near dryers, coating equipment and converting machinery where placing the imaging system too close to the web is undesirable. Kyptec Automation® KL-1414 35 mm SWIR Camera Lens Kyptec Automation® KL-1416 50 mm SWIR Camera Lens

F1.4 Provides Useful Signal Flexibility for High-Speed Webs

Continuous paper lines can move quickly, limiting exposure time before motion blur becomes significant. Narrowband SWIR illumination and moisture-sensitive absorption can further reduce the number of photons reaching the camera. Representative Kyptec Automation® SWIR models provide F1.4 maximum aperture, giving engineers useful light-collection flexibility when short exposure is required.

The aperture should still be optimized rather than automatically left fully open. Web flutter, thickness variation and camera mounting geometry can change the object distance slightly, so adequate depth of field may be necessary to maintain stable focus across production.

Web Flutter Can Change Both Focus and Signal

Fast-moving paper webs do not always remain perfectly flat. Flutter changes the distance and angle between the sheet, illumination and camera, which can alter both focus and reflected intensity. If the inspection depends on a small spectral difference, this mechanical movement can become a significant source of measurement noise.

Camera placement, web stabilization and depth of field should therefore be considered alongside spectral wavelength selection. The production system should be validated at the maximum expected web movement rather than only on a stationary flat sheet.

Paper Dust Can Gradually Reduce Optical Contrast

Paper and cardboard machinery frequently produces airborne fibers and dust. Deposits on the lens or protective window can reduce transmission and create gradual contrast degradation that may be mistaken for a change in the process itself. Kyptec Automation®'s existing machine-vision content also recognizes paper dust as an important contamination source for industrial optics.

A production SWIR station should therefore monitor a stable reference region and include optical cleanliness in preventive maintenance. When both reference and product signals decline together, contamination of the imaging path should be investigated before changing process thresholds.

SWIR Inspection Should Be Positioned Where the Material Information Is Accessible

The best inspection stage depends on the quality variable. Moisture evaluation may be most useful after drying, coating uniformity may be easiest to assess soon after application, and furnish variation may be better detected before later processes obscure the material response. Attempting to inspect everything only at final converting can sacrifice optical access.

Machine builders should therefore identify the earliest stage where the relevant deviation becomes measurable and where corrective action still has economic value. Early detection can prevent many meters of material from moving through subsequent energy-intensive or value-adding processes before a problem is discovered.

SWIR Should Complement Existing Paper-Web Vision Rather Than Duplicate It

Paper machines often already use visible or line-based imaging for tears, holes, wrinkles, edge position and print-related defects. SWIR adds the most value when it measures something those systems cannot see reliably, such as material-dependent moisture, coating or fiber-related variation.

This division of responsibility improves system economics and makes the SWIR inspection easier to justify. The purpose is not to replace every existing vision camera; it is to add a material-sensitive measurement channel where conventional appearance inspection leaves a quality gap.

Why Kyptec Automation® Is a Strong Optical Platform for Paper, Pulp and Cardboard SWIR Inspection

Kyptec Automation® provides a dedicated family of SWIR Camera Lenses across 8.5 mm, 12.5 mm, 25 mm, 35 mm and 50 mm focal lengths, all visible in the current machine-vision lens portfolio. Representative 12.5 mm and 35 mm product pages verify 900–1700 nm wavelength coverage, 2 MP resolution, F1.4 aperture, 2/3-inch sensor format and C-Mount.

This range is particularly useful for the paper industry because inspection geometries vary widely. A broad web or board can require a wide field, localized coating analysis can benefit from tighter sampling, and installations close to dryers or coating machinery may require additional stand-off. Kyptec Automation® allows the wavelength-sensitive measurement and the required physical field of view to be engineered together while remaining within one dedicated SWIR Camera Lens portfolio. Explore Kyptec Automation® SWIR Camera Lenses

Frequently Asked Questions About SWIR Camera Lenses for Paper, Pulp and Cardboard Inspection

1. Can SWIR imaging detect moisture variation across a paper web?

Yes. When a suitable water-sensitive wavelength is used, regions containing different moisture levels can produce different SWIR responses even when their visible appearance is nearly identical. Because the measurement is image-based, moisture can be mapped spatially across the web rather than reduced to one point value. Production validation should include basis-weight, coating and surface-finish variation so the moisture-sensitive signal remains distinguishable from other normal paper changes.

2. Can SWIR detect wet streaks after a paper dryer?

Potentially, and this is one of the strongest industrial use cases. A narrow region that leaves the drying section with more residual moisture can absorb water-sensitive SWIR wavelengths differently from surrounding paper, creating a machine-direction streak in the image. The minimum detectable streak width depends on field of view, pixel sampling, illumination uniformity and the moisture difference between the streak and normal sheet.

3. Can SWIR measure absolute paper moisture percentage?

It can contribute to quantitative measurement, but a calibrated model is necessary. Raw pixel intensity also depends on paper thickness, furnish, coating, illumination, surface condition and camera settings. Known reference samples covering the production moisture range should therefore be used to establish and validate the relationship between SWIR response and moisture percentage. For many applications, relative moisture mapping or pass/fail classification may be easier to maintain than laboratory-grade absolute measurement.

4. Can SWIR detect coating thickness variation on paper?

It can be evaluated when changes in coating amount alter SWIR absorption or reflectance enough to exceed normal substrate variation. Large differences between coated and uncoated paper are generally easier to separate than very small coating-weight changes. For quantitative coating inspection, samples with independently measured coating weights should be used to build the calibration rather than assuming grayscale intensity is directly proportional to coating thickness.

5. Can SWIR identify missing coating areas that are difficult to see visually?

Yes, if the coating and uncoated substrate have sufficiently different spectral responses. A missing region can then appear much closer to the base-paper signature than correctly coated material. This type of inspection can be valuable when the coating is transparent or visually similar to the substrate. The appropriate SWIR wavelength should be selected from real coated and uncoated samples.

6. Can SWIR inspect fiber uniformity in paper?

SWIR can be evaluated for fiber and furnish uniformity where differences in composition, density or distribution produce measurable changes in scattering or absorption. Because normal paper formation also produces spatial texture, the system should distinguish acceptable formation variation from process-level non-uniformity. Region-based statistics are often more useful than reacting to every individual pixel.

7. Can SWIR inspect recycled paper and cardboard material?

Yes, particularly when recycled furnish introduces material classes or contaminants with different spectral responses from cellulose-based fiber. The calibration should include the expected range of legitimate recycled content so normal variation does not generate excessive false rejects. SWIR becomes especially valuable when unwanted foreign material has a similar visible colour to the surrounding paper but a different infrared signature.

8. Can SWIR detect adhesive contamination in recovered paper?

Potentially. Adhesive residues from labels, tapes or converted packaging can produce different spectral behaviour from cellulose. Whether they are detectable depends on adhesive chemistry, fragment size, background material and the wavelength selected. Testing should include the smallest contamination size that matters commercially because small residues can produce mixed pixels rather than a pure adhesive spectrum.

9. Is reflection or transmission imaging better for paper inspection?

Reflection is often easier to integrate because both camera and illumination can remain on one side of the moving web, while transmission can provide strong sensitivity through sufficiently thin sheets when optical access behind the web is available. Thick board and strongly absorbing materials may not transmit enough SWIR signal at certain wavelengths. The correct geometry should therefore be chosen from the paper grade, defect and available machine access rather than by a universal rule.

10. Why does cardboard need different SWIR settings from ordinary paper?

Cardboard and paperboard usually contain more material in the optical path and may also include several layers, coatings or corrugated structure. This changes absorption, scattering and surface geometry. A wavelength or exposure that works well for a thin sheet may provide insufficient signal or different contrast on thick board. Product-family-specific recipes are therefore preferable unless a common calibration has been validated experimentally.

11. Can basis-weight variation interfere with SWIR moisture measurements?

Yes. More material in the optical path can change the detected intensity even when moisture percentage is unchanged. This can make a heavier dry region resemble a wetter lighter region if only one spectral measurement is used. A reference wavelength, independent basis-weight information or multivariate calibration can help separate these effects when quantitative moisture measurement is required.

12. How does web speed affect SWIR paper inspection?

Higher web speed shortens the allowable exposure before motion blur begins to reduce spatial detail. This increases the importance of illumination intensity, aperture and sensor sensitivity. Representative Kyptec Automation® SWIR Camera Lenses provide F1.4 capability, which offers useful light-collection flexibility in short-exposure systems. The complete setup should nevertheless be tested at real production speed because stationary laboratory results can overestimate available signal.

13. When should I consider Kyptec Automation® KL-1408 for paper inspection?

Kyptec Automation® KL-1408 can be evaluated when the application requires broad physical coverage, such as wider paper areas or multiple board sections. The 8.5 mm focal length is the shortest option in the current Kyptec Automation® SWIR portfolio. A wide FOV must still provide enough pixels across the smallest moisture streak, coating defect or material variation that matters to the process. Kyptec Automation® KL-1408 product page

14. When is Kyptec Automation® KL-1412 useful for coating inspection?

Kyptec Automation® KL-1412 25 mm SWIR Camera Lens can be considered when the inspection is concentrated on a smaller region and more sensor pixels need to be allocated to coating streaks or localized material differences. Tighter framing does not increase the chemical spectral contrast, but it improves the spatial representation of that contrast. This can be useful where the coating feature is too small to sample reliably in a very wide field. Kyptec Automation® KL-1412 product page

15. Can Kyptec Automation® KL-1414 or KL-1416 be useful near paper dryers?

Yes. The Kyptec Automation® KL-1414 35 mm and Kyptec Automation® KL-1416 50 mm configurations can be evaluated where a narrower FOV or greater working distance helps keep the camera away from heat, steam, dust or moving machinery. The current 35 mm and 50 mm product pages confirm these focal lengths within Kyptec Automation®'s SWIR family. Final selection should still be based on the required physical field and minimum defect size.

16. Can one SWIR recipe inspect uncoated paper, coated paper and cardboard?

Possibly, but it should not be assumed. These products can differ substantially in thickness, surface finish, moisture range, fillers and coatings, all of which influence SWIR response. Separate product recipes are often more reliable because exposure, wavelength selection and classification thresholds can be optimized for each grade. A universal recipe should be used only after validation shows acceptable performance across all intended products.

17. How can paper dust be prevented from causing false SWIR measurements?

The optical system should include appropriate enclosure or protective-window design where necessary and a maintenance procedure for cleaning exposed surfaces. Paper dust can settle on optics and gradually reduce contrast or create stationary artifacts. Kyptec Automation®'s existing industrial-lens guidance also identifies paper dust as a common contamination source. Monitoring a stable reference area helps distinguish optical contamination from genuine changes in the paper process.

18. What should a paper manufacturer test before selecting a SWIR Camera Lens?

Testing should include every major paper grade, expected moisture range, coating variation, basis weight, surface finish, web speed, flutter, smallest relevant defect, available working distance and required web coverage. The useful wavelength should be established first, then focal length selected according to the physical FOV and pixel sampling required. Kyptec Automation® provides 8.5, 12.5, 25, 35 and 50 mm SWIR focal lengths, giving OEMs multiple options after the optical requirement is defined.

19. What is the biggest mistake when designing SWIR inspection for paper and cardboard?

A major mistake is assuming every SWIR intensity variation represents moisture. Thickness, coating, basis weight, surface finish, illumination angle, web position and furnish can all modify the measured signal. The correct engineering process identifies which variables are expected to change in production and proves that the chosen spectral feature remains sufficiently specific to the target defect. Multi-wavelength normalization or product-specific calibration may be required when several variables overlap.

20. Why is Kyptec Automation® a strong choice for paper, pulp and cardboard SWIR inspection?

Kyptec Automation® provides a dedicated SWIR Camera Lens portfolio spanning 8.5 mm, 12.5 mm, 25 mm, 35 mm and 50 mm, allowing OEMs to choose between broad web coverage, intermediate fields, localized coating inspection and greater stand-off. Representative product pages verify 900–1700 nm wavelength coverage, 2 MP resolution, 2/3-inch sensor format, F1.4 aperture and C-Mount. This gives paper-machine builders useful optical flexibility after the moisture-, coating- or material-sensitive wavelength has been validated, making Kyptec Automation® a strong platform for designing focused industrial SWIR inspection systems rather than forcing every application into one field of view. Kyptec Automation® SWIR Camera Lens collection

Conclusion

SWIR Camera Lens technology can add an important material-sensitive inspection layer to paper, pulp and cardboard manufacturing because many high-value quality variables cannot be judged reliably from visible appearance alone. Moisture variation, coating distribution, furnish inconsistency, fiber-related material changes and selected contaminants can change how a product interacts with short-wave infrared radiation, allowing manufacturers to detect process deviations that an ordinary colour image may not reveal. Kyptec Automation®'s existing general SWIR guidance likewise positions the technology around hidden material differences, moisture and industrial material analysis rather than only conventional visible defects.

The strongest opportunity is to convert this spectral sensitivity into spatial process information. A moisture-sensitive SWIR image can potentially reveal cross-web wet and dry regions instead of producing only one average value. A coating-sensitive wavelength can help identify missing or non-uniform areas across a continuously moving web. Material classification can be used to investigate furnish variation and selected contaminants where their spectral responses differ sufficiently from cellulose-based product. For each of these tasks, the machine should be calibrated around the exact paper grade rather than assuming that one wavelength and threshold will work identically for thin paper, coated stock and thick cardboard.

The SWIR Camera Lens is central to translating this spectral difference into production-ready spatial information. The lens must provide enough physical coverage for the web while assigning sufficient pixels to the smallest moisture streak, coating anomaly or material variation. Working distance must also fit around dryers, coating equipment, moving rolls and dust-producing processes. The current Kyptec Automation® portfolio provides 8.5 mm, 12.5 mm, 25 mm, 35 mm and 50 mm focal lengths, and representative products such as Kyptec Automation® KL-1410 and Kyptec Automation® KL-1414 are specified for 900–1700 nm, 2 MP, F1.4, 2/3-inch and C-Mount configurations.

For paper-machine OEMs, converters and quality-control engineers, the central principle is to define the material variable first, validate the wavelength second and select the SWIR Camera Lens from the required field of view and minimum spatial feature third. Moisture measurement, coating inspection and fiber or furnish uniformity are different optical problems even when they occur on the same production line. When these measurements are developed independently and then integrated into the machine with stable illumination, appropriate calibration and correct focal-length selection, Kyptec Automation® SWIR Camera Lenses provide a strong optical foundation for advanced industrial inspection of paper, pulp, coated stock, carton board and cardboard.