Introduction
Wolfgang Beltracchi was one of the world’s most successful art forgers. It is believed that he earned more than Euro 50 million by making forged art works attributed to great European artists, sold through top auction houses. Traditional art experts could not detect his fraud; the breakthrough came during the analysis of a painting using:
- Infrared reflectography NIR imaging (Nearly Infrared)
- Spectral analysis of pigments (using multispectral imaging)
The purpose of mentioning this incident is to highlight that time has come to introduce multispectral imaging for viewing and inspection for packaging printing to identify defects “Beyond visual spectrum”.
The Gap in Current Print Inspection
Current web viewing and inspection systems on rotogravure and flexo presses predominantly work in the visible RGB spectrum. They catch geometric defects, registration errors, and missing print — but they are blind to:
- Ink layer composition differences that appear visually identical but differ spectrally. As a result, the print may appear correct before lamination, while colour variations become visible afterwards.
- Substrate contamination hidden under printed layers
- Fluorescent or UV-reactive inks used in security and brand-protection printing
- Moisture variation due to insufficient drying in the substrate affecting ink adhesion
- Metamerism — two colours that match under one light source but differ under another
How multispectral works
Unlike a regular camera that uses red, green, and blue (RGB) channels, multispectral imaging typically uses more than three channels which are often narrower and spectrally non-overlapping, providing more detailed spectral information about an object.
Multispectral cameras measure image data in specific wavelength ranges of the electromagnetic spectrum, far beyond what the human eye can see (380–780 nanometers).
What Multispectral Would Add to Packaging Print Inspection
1. Sub-Surface & Hidden Layer Detection
True multispectral (NIR, SWIR) would go much deeper, seeing through opaque substrates and overprints.
2. Brand Protection & Anti-Counterfeiting
Packaging increasingly carries covert security inks — fluorescent, IR-absorbing, or UV-visible — that authenticate brand ownership. Only a multispectral camera can verify these features inline at press speeds without stopping the job.
3. Food-Safe Ink Verification
Regulators increasingly require that food-contact packaging use only approved inks. Multispectral imaging is an advanced imaging technology that enhances industrial inspection by capturing image data across selected wavelength bands beyond the visible spectrum, allowing manufacturers to improve material detection and identify defects that are not visible with conventional RGB imaging. Ink composition anomalies — wrong ink applied, contaminated batch — could be flagged in real time.
4. Substrate Quality Detection
SWIR image sensors are useful for container content inspections as SWIR light penetrates packages, allowing inspections to be carried out without destroying them, detecting substrate defects, moisture pockets, or adhesive failures beneath printed surfaces.
5. Colour Consistency Beyond Human Vision
Some applications demand unconventional RGB wavelength bands while others demand a combination of visible and non-visible wavelengths. Complex metrology and imaging applications are beginning to demand higher numbers of spectral channels or possibilities to select application-specific spectral filtering at high inspection throughputs. Packaging brand owners have extremely tight colour tolerances — multispectral measurement would catch metamerism failures before they reach the customer.
Conclusion
Current packaging print inspection systems are fundamentally limited by their reliance on the visible RGB spectrum, leaving an entire class of defects — spectral ink differences, hidden substrate flaws, security inks, moisture variation, and metamerism — completely undetectable at press side. Multispectral imaging, which captures data across carefully selected narrow wavelength bands spanning NIR, SWIR, and UV in addition to visible light, offers a way to see what RGB cameras cannot.
While printing and converting companies recognise the value of advanced defect detection systems, wider adoption will depend on demand from packaging development teams and brand owners in the FMCG and pharmaceutical sectors.
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