Challenge:
Develop a stent inspection system that features advanced imaging and illumination technology. The system needed to provide superb image clarity and contrast.
Requirements:
A cardiovascular stent has hundreds of critical features with tight tolerances. Some drug coated stents require 100% inspection over all surfaces.
Difficulties:
Stent inspections mostly involve multiple operators viewing individual stents using optical tools and stereomicroscopes. The process is labor-intensive and, from a practical standpoint, open to human error. Stent inspection has been traditionally accomplished by manually operated stereomicroscopy. The typical drawbacks of inspecting cylindrical surfaces with this method are non-referenced field of view and focal depth of a stereomicroscope increasing operator fatigue and error. Often parts are being rotated under the microscope while the operator is looking from point to point. This presents a challenge not just for stent manufacturers, but also for other device companies that must perform such optical inspections.
Solution:
An NI PCI express camera link frame grabber together with an NI motion controller is utilized to scan images of the inner and outer surface of a drug eluted stent. As the stent rotates on a custom fixture with encoder, a high-resolution line scan camera captures the drug-coated surface of the stent with 4-micron resolution. Our solution provides the operator with the ability to capture the entire inner and outer surface of a stent within a two second scan at four-micron resolution. The image captured by the line scan camera effectively transforms the 3D surface into a two dimensional representation of the stent. In contrast to the limited field of view of the stereomicroscope the operator now has a single image of the entire stent surface at hand. Not only is the entire surface completely in focus, the image can also be archived for future reference. This automated inspection system provides 100% traceability, decreased operator error and increased throughput for inspection.
Result:
At moviMED, we developed a user-friendly state-of-the-art stent inspection system. We can produce high quality images when inspecting unpolished, polished, parylene coated and drug coated stents. Our inspection system is a self-contained tabletop system platform that allows for easy operator access to all system controls.
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