Achieving Japan quality through machine vision - High-resolution colour image processing for immaculate pharmaceutical products
Scanware Electronic inspects tablets in blister packs after sealing with the aid of powerful machine vision systems. One of these, the Lynx Spectra HR, developed in close cooperation with STEMMER IMAGING and utilising up to six watercooled 3CCD colour cameras from JAI, is an ideal system structure for use in a tight space.
Japan quality ...
... is the magic phrase for manufacturers of pharmaceutical products.
The visual appearance of products is extremely critical on the Japanese market, because Japanese consumers, even more so than in other cultures, lose confidence in the correctness of the manufacturing process and the overall quality of a product at even the slightest optical flaw. Medicaments thus become virtually unsaleable on account of just the tiniest of optical flaws. For pharmaceutical manufacturers, the appearance of the products thus becomes just as decisive a criterion as their effectiveness and harmlessness.
Scanware Electronic from Bickenbach in southern Hessen, Germany, has been facing up to the challenge of these high quality standards in the inspection of products and packaging for years. "As an internationally operative mid-size company we have been developing and producing inspection systems for packaging machines in the pharmaceutical industry since 1989", says Scanware's managing director Harald Mätzig.
"We brought the first colour system onto the market as early as 1993 and in the years that followed we developed various inspection and checking systems for all relevant process steps along the packaging line. The Lynx-Spectra, a functioning colour system from this series introduced in 2003, is in use at numerous pharmaceutical manufacturers."
Increasingly complex systems
The requirements for systems for the inspection of tablets and blisters have been increasing steadily for years. Mätzig says that the reason for this, apart from increasing speeds of production, is also the fact that the marketing departments of the pharmaceutical manufacturers are constantly dreaming up new ideas for the blister design in order to set themselves apart from competitors. The resulting quality control requirements has led Scanware to the continual development of even more powerful inspection systems and the optimisation of the vision systems used in them.
The experts at Scanware view the attainment of Japan quality as a separate task. "In order to develop a suitable inspection system we first of all narrowed down the criteria that would allow an objective grasp of this quality demand", says Scanware's head of development Dirk Schneider, outlining the approach. Reasons for the rejection of the product itself are accordingly coating defects or particles on the tablets or on the coating. Beyond that, contamination with hair or particles extraneous to production represent critical quality defects.
For the imaging components used, this means that particles with a size of a few tenths of a millimetre must be detected with extremely high colour differentiation. Not only that, this performance must be available in the line at speeds of up to 300 cycles per minute, which is equivalent to an inspection performance of up to 900 blisters per minute with the frequently used three-row blister packs.
So as not to slow down the machine, therefore, the goal of the revised vision system was to achieve an optimum combination of resolution and speed. "We had to achieve the maximum possible resolution at the demanded frame rate", says Schneider, emphasising the size of the task. "Reliable detection was thereby naturally at the forefront."
3CCD colour cameras – the ideal solution
He says that a single-chip colour camera was never in the running for this task. "In order to achieve the necessary colour separation, a very high resolution is required with this camera type. The data quantity would have been too large and the processing speed too slow for that", explains the Scanware development manager.
The mechanical and electrical environmental conditions in and around packaging machines are not conducive to the use of a single high-resolution camera with alarge working distance. The use of several cameras each with a smaller working distance was the technical alternative. "The use of 3CCD cameras in a cascade arrangement was ultimately proved to be our ideal solution to the task" , says Schneider.
The next step involved finding suitable cameras and the associated lenses for the multi-camera concept that Scanware had come up with for ensuring Japan quality. At this point Scanware fell back on the expertise of its long-standing technology partner for imaging and machine vision: "STEMMER IMAGING has been an important supplier of our imaging components for many years and their expertise has been of invaluable help to us in the past with many other systems" , says Schneider, justifying his decision.
"We have been using 3CCD cameras for many years now in order to achieve a high colour resolution in applications that require it", adds managing director Mätzig. "Since we have to combine several cameras via our own multiplexer in the new system in order to achieve the demanded resolution, we had to re-evaluate. Due to the combination of the camera images, the camera-specific deviations within the tolerances and their differences from camera to camera become visible."
According to Mätzig, Scanware benefitted in this phase of the development from STEMMER IMAGING's valuable assistance: "After the initial preliminary discussions, our sales contact Jürgen Finner already had a very good idea which of the numerous camera alternatives might be suitable for this task. On the basis of loans we were then able to test possible camera options and make a decision."
Not least due to its very high colour separation and low image noise, the choice finally fell on the CameraLink version of the CV-M9 CL camera model from the Danish manufacturer JAI, whose products are distributed through STEMMER IMAGING. This 3CCD camera works with three 1/3" progressive scan CCD sensors, which offer a resolution of 1024 x 768 pixels with a pixel size of 4.65 µm for each RGB colour, and supplies 30 images/s at full resolution. In this camera type the light entering is broken by a lens into the red, green and blue components of the light and guided to the respective CCD sensor. It therefore offers outstanding colour separation with low image noise.
"There was a calibration procedure for this camera in order to compensate for specific peculiarities", says Schneider, outlining a further advantage of the JAI CV-M9 CL. "Together with STEMMER IMAGING we developed a calibration jig for this, which we first tested at our facility. The cameras are now calibrated in Puchheim and delivered to us for installation in the Lynx Spectra HR systems."
Conceived for the long term
Pharmaceutical products can have a lifecycle of decades. That means that the Scanware systems must be reliable for over ten years and work with a constant quality. "Long-term deliverability was a second decisive criterion in addition to the high camera quality" , says Schneider. Statements by JAI on the planned product development were therefore also one of the criteria in the selection of the camera.
"We know that the product managers at STEMMER IMAGING are in close contact with the manufacturers of the products that they offer. They are informed at an early stage about developments or discontinuations", says Harald Mätzig. "STEMMER IMAGING is often the most important buyer of such high-quality products worldwide, which also has a favourable effect on the availability period. That gives us as the customer the necessary planning security."
Water-cooled for constant performance
Once the camera type had been defined, the solution for the most sensitive part of the system had been found. The design of the complete system with all its components was now defined. The heart of the inspection system is formed by two, three, four or six cameras in a cascade arrangement. Their image information is combined by a multiplexer developed by Scanware and prepared for evaluation. The user only sees a combined image for the evaluation, although the image analysis takes place on the basis of the image information of each individual camera.
A further highlight of the system is the white light LED module – similarly a Scanware proprietary development. The adjustability and controllability of the illumination as well as the large number of LEDs used was important to the developers. It brings crucial benefits with regard to stability and lifetime. Dirk Schneider even considers this to be a unique selling point: "The WLED module operates in flash mode with a frequency of about one millisecond. The short flashes of light protect against overheating, ensuring a long lifetime and constant brightness. The illumination is also controllable, which enables the light to be reduced with bright products and increased with dark products."
The cameras are installed next to each other under a closed stainless steel hood. In such a small space, each camera gives off its own heat to the other cameras. The complete area around the cameras would heat up. Since many products manufactured in the pharmaceutical environment produce dust, ventilation of any kind is undesirable. Scanware solved this problem with a water cooling system for the cameras.
Increased or changing ambient temperatures result in a less than ideal environment for cameras and lead to colour scattering. "The advantage of the multi-camera system with regard to resolution would be rendered null and void again by the temperature-related colour drift", Schneider explains.
One of the last development steps was the integration of all the imaging components – i.e. the cameras, the appropriate lenses and the LED lighting – which had to be housed together with the water cooling for the cameras in a relatively small space. The Scanware developers did a great job here in achieving an ideal system structure.
Fine adjustment by software
In addition to the pre-calibration of the cameras and the optimisation of the camera temperature through the water cooling, the software ultimately offers various functions for the fine adjustment of the colour recognition. As an interface to the user, it encompasses many statistical evaluation tools for product inspection. Webs can be checked, consequential errors detected and post-filling information offered that shows the user where it might be possible to subsequently fill missing tablets. In addition, error clusters can be identified and localised in order to be able to eliminate error causes. Customer requirements are thereby incorporated in order to implement the demanded statistical evaluation options.
Product-related tolerances, e.g. variations of product, colour and shape, can be programmed for the same blister. This can be necessary for preparations and combinations of preparations that need to be taken over a certain fixed period.
Second machine vision system for the underside
In the packaging process, the image processing is usually positioned before the sealing. Before this process an endless film is formed by deep drawing in such a way that recesses – blisters – are formed, which are then filled with tablets. After that, production control takes place with the vision system before the packaging is sealed with a cover foil. The filled and sealed packaging subsequently advances to further processing, where it is inspected again in some cases before being perforated and printed as necessary. The marking is often checked here by Scanware systems of the Lynx-Signum type. Finally, after a certain number of cycles, the packaging reaches the ejection station. In accordance with the result of the inspection before sealing, this is where packaging with faulty products is ejected.
"In the case of Japan applications we additionally have to inspect the product from underneath with a second camera module to ensure that there really have been no errors in the section between the camera station and the sealing station" , adds managing director Harald Mätzig. "This also allows us to inspect the underside of the product itself for possible errors."
Minimisation of risks
In conjunction with their packaging solutions, pharmaceutical companies usually consider and evaluate two large risk areas: The pharmaceutical risk and the economic risk. Both risks can be reduced with automatic quality checking procedures. The pharmaceutical risk is that the patient doesn't receive the stated quantity of active ingredient because errors occurred during the packaging process, e.g. because tablets broke and there are only parts of tablets or additional fragments of tablets in the packaging. Colours also play a part: when hormonal products are taken over a lengthy period, the products are colour-coded according to the foreseen interval at which they are to be taken. It is important here to take the tablets with the correct colour in the specified period.
The financial risk arising directly from the packaging process lies in the quantity of good product that is separated out during the process. If one blister is not filled or is incorrectly filled and then sealed, the entire blister pack must be ejected. Economy suffers if good products end up in the waste in this way.
In formulating the requirements for the inspection systems, therefore, the maximum ejection rate of good product is always specified. For blister machines this value is usually less than 1 % and may even be less than 0.1 %. Not only that, the quantity of good product ejected should minimize towards the end of the process chain, since the product is getting increasingly close to the final delivery state and is thus becoming increasingly expensive.
Japan quality attained
Scanware's managing director Harald Mätzig sums up: "Such demanding projects would be much more difficult to achieve without the productive and uncomplicated partnership between STEMMER IMAGING and Scanware and the resulting unbureaucratic processes in the development phase. With this system, which has now been manufactured, we are able to ensure that patients – whether Japanese or not – can press their 100 %-inspected tablets out of the blister pack with confidence, even if the medicament has travelled half way around the world."
Scanware Electronic GmbH is an internationally operative, mid-size, privately-owned company. As an independent manufacturer it develops and produces systems for the inspection of products and packaging in packaging machines in the pharmaceutical industry. Scanware products have been tailored for over 25 years to individual practical needs. They are specialised to a high degree and fully compliant with the strict GMP requirements. Over 2000 installations worldwide have resulted in Scanware gaining a reputation as a supplier of top technology to all renowned manufacturers.