Automated inspection of injectable vials, vaccine vials, biologic vials and many other high value sterile products is now necessary to ensure that every single vial inspected before being dispensed to a patient contains the correct fill level, does not contain particulate contamination, does not have cracks in the glass, does not have problems with the stoppers, or does not contain obvious cosmetic defects. Although manual inspection was once the norm, there are significant drawbacks to using manual inspection. These include: operator fatigue, subjective interpretation of inspection results, inconsistent results, and low throughput. Automatic vial inspection machines overcame all of the drawbacks of manual inspection by providing a fast and accurate way to inspect vials at a high rate of throughput (with minimal variability) and provide standardized inspection results.
In this blog, we will describe the five primary stages of how an automatic vial inspection system operates. They are: Mechanical Handling System, Kinetic Excitation Systems, Optical Architecture, Software Intelligence, and Rejection/Decision Systems. We hope to describe each stage simply and clearly to assist in understanding how current inspection technology provides the highest possible standards of product quality.
Stage 1 – Mechanical Handling & Singulation
Without reliable and consistent mechanical Vial Movement, no matter how sophisticated your Vision System is, you will not be able to achieve accurate inspections.
1. Singulation and Input
Bulk vials are fed into a machine via input trays or conveyor lines, or other integrated in-feed mechanisms. The vials are then singulated (evenly spaced) by starwheels, timing screws or custom-designed feed worms.
Singulating allows for individual inspection of each vial. Consistent spacing between the vials is also important as it provides clear images of the vials to the cameras and prevents motion artefacts or overlapping images of adjacent vials.
2. Vibration Damping
After being segmented, the vials are in a damping area for vibrations. The micro-vibrations can make the liquids inside the vial move back and forth randomly and produce reflections or motion signatures from the movements of the liquid, which could be misinterpreted as particulate contaminants.
Stage 1 – Mechanical Handling & Singulation
To avoid false positives, the machine uses:
- Mechanical buffers
- Soft holding pockets
- Controlled deceleration systems
These stabilize the vial before image capture begins.
Stage 2 – Kinetic Excitation (“Spin & Stop” Method)
Kinetic Excitation is how the machine detects particulate matter inside a Vial. The machine creates turbulence in the liquid of the vial when it rotates quickly about its axis. This turbulence lifts all particulates (fibres, etc.) into suspension, creating an environment where they can be easily seen by the camera.
The “Spin & Stop” method is the way this process works:
- Quickly spin the vial
- Suddenly stop spinning the vial, so the particulates will begin to move on their own from the liquid.
These movements create High Contrast Frames, which help to improve accuracy with the detection of particulates.
Other techniques also exist, such as:
- Swirl Method: A softer agitation than Spin & Stop.
- Inversion Methods: For use with highly viscous liquids or liquids/suspensions.
Including mention of these methods helps to show the machine’s ability to work effectively with a variety of product types.
Stage 3 – Optical Architecture (Lighting & Cameras)
The optical configuration is the core of the inspection system; without an appropriate illumination method and camera angle, inspection for defects can be unreliable.
Lighting Systems
Different Lighting Methods are required to inspect Different Defects:
Backlit Lighting
Utilized for:
- Fill Level Inspection
- Stopper Presence/Tilt
- Detect Gross Glass Defects
Backlit Lighting creates a clean silhouette so that accurate measurements may be made.
Strobe Lighting
Used for:
- Particle detection during spin & stop
- Capturing fast-moving particles with frozen motion
The strobe fires in micro-intervals synchronized with vial orientation.
Dome / Diffuse Lighting
Used for:
- Cosmetic inspection
- Surface scratches
- Hairline cracks
- Sediment visibility
Lighting which is not focused will eliminate those harsh reflection types to create a surface which has no areas where imperfections are hidden.
Why lighting angles matter:
Different angles of light create different shadows, as well as show you other possible planes of defects and also help identify clear or transparent types of defects.
Camera Systems
Advanced Vial Inspection Machines have several features to increase their capabilities:
- Superior Industrial Camera Resolution, which captures multiple frames every millisecond
- Sensors utilizing Global Shutter for the fastest moving objects, such as vials
- Multiple camera Architecture provides a complete 360-degree visual inspection
- Optional 3D Vision to detect the Stopper or advanced glass inspection
- Infrared Sensors can be used on certain Opaque or Tinted Glass vial applications
The use of Servo Motion Control in conjunction with camera Synchronization will provide the most accurate results possible by ensuring that each frame is taken exactly when the vial is at the correct position.
Stage 4 – The “Brain”: Software & Algorithms
This is where next-generation vial inspection machines truly outperform manual inspection and older systems.
Algorithm 1 – Frame Subtraction
The frame subtraction algorithm compares successive frames:
- Moving objects are displaced between frames
- The background (the glass and the liquid) remains consistent between frames
When two consecutive frames are subtracted, the system isolates movement and removes background noise, greatly enhancing particulate detection.
Algorithm 2 – Edge Detection
Edge detection detects sudden transitions in pixel intensity.
Edge detection is best suited to detecting:
- Cracks
- Snags (chips)
- Scratches
- Issues with the stopper
- Cosmetic flaws
Without edge-based analysis on a transparent substance such as glass, even slight imperfections may go unnoticed.
Algorithm 3 – Deep Learning / AI Vision
AI-based systems are transforming vial inspection:
- Thousands of defective vial images help them to Learn
- False Rejection Rate is one of the most important KPIs for Pharmaceutical Companies, as these machine learning systems can reduce
- Complex Defects can be classified by AI-based systems, including:
- Collapse of Lyophilized Cake
- Frosting
- Hole
- Uneven Cake Formation
The model will continue to evolve, allowing the system to remain Future-Proof.
Additional Algorithms (Competitive Advantage)
Modern Inspection Machines have additional capabilities to surpass other systems as follows:
- Pattern Recognition (Label/ Cap /Seal)
- Three-Dimensional Re-Construction (Stopper Tilt / Depth Assessment)
These two technologies work together to produce an inspection decision matrix.
Stage 5 – The Decision-Making & Rejection System
How the System Decides “Pass” or “Reject”
Based upon a set of criteria that include:
- A defined level for defects (customer specifications/pharmaceutical standards)
- The confidence score provided by an algorithm
- Validation of multi-parameters to confirm the vial meets all applicable regulations
The inspection system rejects the vial if it is confident that the defect exceeds established acceptable levels.
Rejection Mechanisms
Each of the various vial inspection machines uses one or more of the following reject mechanisms:
- Pneumatic air jet
- Mechanical diverter arm
- Servo gate
All reject mechanisms are designed to prevent contaminated vials from being included in the acceptable product batch.
Data & Traceability
All decision data is stored in:
- 21 CFR Part 11–compliant logs
- Batch images
- Alarm and parameter records
Integration with MES and SCADA enables complete production visibility.
Common Defects Detected
Automatic vial inspection machines can detect:
- Visible and sub visible particulate matter
- Cracks, chips, and glass scratches
- Incorrect fill levels
- Stopper tilt, displacement, or presence issues
- Cosmetic issues (fogging, stain marks, streaks)
- Lyophilized cake defects such as:
- Collapse
- Holes
- Frosting
- Channel formation
Applications Across Pharma & Biotech
These systems are widely used for:
- Injectable drugs
- Vaccines
- Biologics
- Monoclonal antibodies
- Diagnostic reagents
- Veterinary injectables
Conclusion
Advanced Automatic Vial Inspection Machines use Mechanical Precision, Optics, Powerful Algorithms and Reliable Rejection Systems to Deliver Consistent Product Quality in Compliance with Regulations and to Protect Patient Safety.
Each Stage of the Five-Stage Process (Singulation, Kinetic Excitation, Optical Imaging, Artificial Intelligence Driven Analysis, Rejection) is designed so that all products meet patient safety requirements.
The need for Pharmaceutical Companies to be accurate, compliant and productive has moved from a “nice-to-have” to a “must-have” through automation.
