Spectral imaging and high-speed sorting
The optical demands become even greater when systems move beyond simple pass / fail inspection and must identify materials at production-line speeds.
In recycling facilities, hyperspectral imaging( HSI) systems monitor conveyor belts moving at speeds of up to 3 m / s, distinguishing polymers such as PET, HDPE, PVC, polypropylene, polystyrene, and ABS through their unique spectral signatures. These signatures are measured within the near-infrared( NIR) and shortwave infrared( SWIR) regions, requiring optics that can deliver clean, consistent spectral data in difficult industrial environments.
Research published by UCL in 2025 demonstrated that HSI could identify contaminated plastic packaging with accuracy rates of up to 99 %, highlighting both the capability of the technology and the importance of optical quality in achieving those results.
At such operating speeds, optical components must provide high transmission to ensure sufficient light reaches the detector during short integration periods. Mixed-material surfaces and glossy finishes can introduce flare and unwanted reflections. Bandpass filters designed to isolate the required NIR and SWIR wavebands suppress this interference and improve measurement reliability. The same principles used to stabilise AOI systems are therefore equally important in advanced sorting applications, albeit under more demanding operating conditions.
Durability in continuous operation
AOI systems are expected to operate continuously while being exposed to vibration, thermal cycling, UV radiation, and aggressive cleaning processes. Any deterioration in optical performance directly affects the quality of the inspection data being produced.
Diamond-like carbon( DLC) coatings improve resistance to abrasion in applications requiring regular cleaning or physical contact. Dielectric coatings provide stability when temperatures fluctuate, while protective windows, commonly manufactured from sapphire because of its hardness and optical transmission characteristics, help shield internal optics from dust, debris, and impact damage while preserving optical alignment.
Optical specification as an operational advantage
A properly specified optical system delivers higherquality image data, more dependable inspection outcomes, reduced false reject rates, and reliable performance throughout the working life of the equipment.
Knight Optical supplies precision optical components for machine vision and automated inspection systems used across manufacturing, food and beverage, pharmaceutical, and recycling applications.
Its range includes interference bandpass filters, protective windows, and custom optical solutions designed for demanding environments, supported by technical guidance to help ensure components are matched to real-world operating conditions.
Knight Optical Windows & Diffusers www. knightoptical. com
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