Multi-Camera Blister Pack Verification for Nutritional Supplements

This page describes our approach to a technically demanding pharmaceutical inspection application: verifying the presence, identity, integrity, and correct placement of tablets in blister packs across a wide range of product types — including fully transparent, semi-transparent, and opaque tablets with a glossy, oily finish.

The Challenge

A leading manufacturer of vitamins and nutritional supplements required a vision system to be retrofitted onto an existing blister packing machine. The system needed to perform four distinct inspection tasks on every blister pack, across a large number of SKUs, at a rate of one pack every two seconds.
The inspection requirements were:

1. Presence verification — confirm that every blister cavity contains a tablet

2. Product verification — confirm that the correct tablet type is loaded for the current product run

3. Integrity verification — confirm that every tablet is full size and undamaged, by measuring length, width, and area

4. Contamination check — confirm that no additional tablets are sitting on the blister pack plastic outside of a cavity

The application presented several significant technical challenges:

1. Product variety — tablets ranged from fully opaque to fully transparent, with many variants in between. Almost all had a glossy, oily surface finish, creating challenging reflections under standard lighting conditions

2. Field of view — the 64-cavity blister pack required a large field of view, making uniform illumination difficult. Standard single-camera setups resulted in correctly exposed tablets at the edges but saturated, overexposed images at the centre

3. Transparent tablet edges — for transparent tablets, presence and size measurement depend on clearly resolving the tablet edge. Non-collimated lighting causes the edges of transparent tablets to effectively disappear, making reliable inspection impossible

4. SKU flexibility — with many product variants, the system needed to be straightforward for operators to set up when changing products, without requiring specialist vision knowledge

The Solution

Imaging architecture

To overcome the field of view and illumination challenge, we designed a system using an array of four board-mount cameras rather than a single large-format camera. Each camera covers a defined quadrant of the blister pack. A flat field correction (FFC) routine calibrates each camera individually, ensuring consistent, uniform illumination across its zone. High-precision image stitching then combines the four images into a single, seamlessly unified image of the entire blister pack.

From the operator's perspective, the system produces a single image of the 64-cavity pack. The underlying four-camera architecture is entirely transparent to the user.

Lighting

Collimated backlighting was selected as the primary illumination strategy. By directing light in parallel rays through the tablet from below, the edges of even fully transparent tablets are rendered clearly and consistently — making reliable presence detection and dimensional measurement possible across the full product range. Non-collimated backlighting was evaluated and rejected, as it caused the edges of transparent tablets to become indistinct, undermining the integrity of the inspection.

Inspection logic
The system operates with knowledge of the current product — the tablet layout, expected dimensions, and optical characteristics for each SKU are configured in advance. When a blister pack is indexed into position, the system:

• Analyses each of the 64 cavities against the known blister layout to verify occupancy

• Measures the light transmitted through each tablet to verify product identity — different tablet compositions transmit light differently, providing a reliable distinguishing signal

• Measures the length, width, and area of each tablet to confirm it is full size and undamaged

• Scans the blister pack plastic outside of the cavities to detect any rogue tablets that may have become lodged on the surface

Operator interface

With a large number of SKUs, ease of product changeover was critical. A step-by-step setup process was developed within the machine interface, allowing operators to configure a new product quickly and intuitively without specialist vision knowledge. Once configured, the product parameters are stored and recalled automatically on subsequent runs.

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Outcome

The system was commissioned successfully and deployed in production. It delivers robust, automated inspection of every blister pack at full machine throughput — one pack every two seconds — across the full range of product variants. Operators are able to set up new products independently using the guided interface, and the system reliably detects missing, incorrect, broken, and misplaced tablets regardless of tablet transparency or surface finish.