The Automated Optical Inspection (AOI) is a well-established method of automated visual quality control, particularly in Good Manufacturing Practice (GMP)-regulated production environments within the pharmaceutical industry. In the pharmaceutical context, the process is commonly referred to as Automated Visual Inspection (AVI); regulatory texts generally use the term “visual inspection”.
AOI is based on automated image processing, supported by optical sensors and machine evaluation algorithms. The goal is to automate quality assurance, accelerate processes, and detect errors with the highest accuracy. With the help of modern imaging and processing technologies, AOI systems can identify even the most minor visually detectable defects – such as particles, fill level deviations, or surface defects.
As a result, Automated Optical Inspection is superior to manual inspection in many areas. Common fields of application for automatic optical inspection, besides the production of pharmaceutical products and packaging, include the semiconductor industry, food technology, electrical engineering, and the automotive and aerospace industries.
AOI in the Pharmaceutical Industry
In the pharmaceutical industry, AOI systems are frequently used to inspect the quality and flawlessness of surfaces. A central task is quality assurance: With the help of automatic visual inspection, packaging defects, contamination, foreign particles, fill level deviations, and other errors can be detected.
The method is particularly relevant in the industry because sterile products are subject to stringent quality standards, particularly in aseptic filling, where AOI systems help to ensure the highest purity and safety standards in accordance with GMP.
For parenteral products, EU-GMP Annex 1 (8.30) requires an individual visual inspection of every filled container (100% inspection). Automated methods may be used, but they must be validated and demonstrated to be equivalent to or superior to manual inspection (Annex 1, 8.32).
Equipped with the appropriate technology, AOI systems can detect significantly smaller defects than the human eye, enabling an objective and reproducible inspection. Additionally, they are often used in conjunction with sample-based manual inspections. The technology is also more efficient than the comparatively time-consuming quality control under a microscope. As a result, Automated Optical Inspection in the pharmaceutical sector often leads not only to higher product quality but also to lower production costs. Furthermore, it meets industry-specific requirements for patient safety and compliance, among others, through high reproducibility and objectivity of results.
Functionality of Automated Optical Inspection
AOI systems can be complex or simple in design, depending on the level of sophistication of the production operation. In general, AOI is based on a multi-stage process that runs fully automatically.
- Image capture: This process occurs in the first step, utilizing high-performance optical and digital methods. If necessary, additional tools such as lighting and magnifying lenses are used.
- Image recognition and processing: In the next step, image processing takes place. Simple models perform an actual-target comparison, while more complex AOI systems use AI functions and machine learning to detect defects or contamination.
- Decision: AOI systems generally not only perform inspection but also make automated decisions. For example, the technology identifies and classifies defective products according to their quality.
- Documentation: Finally, the system creates inspection reports. These can be used to identify irregularities in production or to improve the process further. If required, Automated Optical Inspection can be integrated into larger quality systems.
Areas of Application for AOI Systems
In the pharmaceutical industry, automatic visual inspection is widely used, particularly for inspecting pharmaceuticals, packaging, and labels. This is often carried out as a final inspection after production has been completed. However, intermediate products are sometimes also inspected using AOI systems.
Examples of AOI Applications in the Pharmaceutical Industry
A key application area for AOI inspections in the pharmaceutical industry is the visual inspection of primary packaging such as BFS containers, vials, and crimp caps.
Injection preparations, for example, can be easily inspected automatically using optical methods to ensure that they are free of foreign particles. Typical defects, such as broken glass and incorrect fill levels, can also be detected. Such inspections are usually completed within fractions of a second.
Advantages of Automated Optical Inspection
AOI systems offer four main advantages – precision, speed, complete GMP-compliant documentation, and efficiency in quality assurance.
- Precision: AOI systems are considered far more accurate and reliable than human visual inspections.
- Speed: Modern AOI systems, with powerful optics and algorithms, are capable of inspecting thousands of units per hour.
- Documentation: The system creates a complete audit trail, providing benefits for compliance and traceability.
- Efficiency: AOI reduces ongoing personnel costs, increases product quality, and lowers the error rate when insights from analytics are utilized for optimization.
Disadvantages of AOI
The use of AOI can also involve some disadvantages. In addition to high investment costs, its use requires careful system validation (IQ/OQ/PQ) and continuous calibration to minimize misclassifications. However, the latter can be reduced through optimization of the technology.