Repetitive inspection system with intelligent tools
a technology of intelligent tools and inspection systems, applied in the direction of instruments, blood vessels, prostheses, etc., can solve the problems of prone to life-threatening situations, damage to blood cells or the blood vessel in which they are inserted, and sometimes defective parts, and achieve the effect of faster and more accurate inspection
Inactive Publication Date: 2005-11-24
FREIFELD DANIEL
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Benefits of technology
[0013] The present invention provides a faster and more accurate inspection tool to determine the quality of stents and other precision cut tubes. Specifically, this invention provides a means to scan a stent in a continuous manner so as to create a flattened image of a small, cylindrically shaped, precision cut tube, very quickly by utilizing the inventive optimal lighting system to create these images. The present invention is comprised of an electronic camera, a rotary stage which receives a mandrel, an illumination source to illuminate the tube under inspection, and a computer based imaging system. The camera comprises a lens and at least one photodetector. The camera's lens is configured and dimensioned for focusing an image of a precision cut tube on the photodetector(s).
[0017] To obtain measurement data about cut features and cosmetic attribute information for a cut tube, this invention coupled with a software pattern recognition system that can simplify the programming for an individual cut tube by means of finding repetitive patterns. The image is analyzed by an operator selecting a recurring pattern set in the image of the tube. Then the user selects one pattern within the pattern set as an anchor pattern. He then sets virtual vision tools at specific locations within the image. The computer software then finds the anchoring pattern on the image, and from there iteratively examines areas adjacent to the anchor pattern until all areas of the image are examined.
Problems solved by technology
If the stent contains any rough or sharp edges, it will damage blood cells or the blood vessel in which it is inserted.
This can lead to further atherosclerotic plaquing, emboli or thrombi, and result in potentially life threatening situations.
This process, while highly precise, can occasionally produce defective parts.
Accordingly, small changes in manufacturing process parameters such as laser power, tubing diameter, or mechanical jitter can cause defects.
Such defects may include an out of tolerance feature size or a malformed feature.
Since stents are used in the heart and other critical areas of blood flow, a failure in the function of the stent could be life threatening.
The problems associated with either the manual or automatic approaches to inspection are numerous.
First, human error makes visual inspection of products less than completely effective.
Also, such manual inspection is relatively slow and thus a relatively costly aspect of the manufacturing process.
Furthermore, the pass / fail criteria of the profile projector using overlays, as is typically employed in manual inspection, does not generally provide any numeric dimensional data that would otherwise be useful for process control.
While the possibility exists to employ automated systems, automated vision systems also have similar and other problems.
First, the use of automated vision systems, like human inspection, tends to be slow.
Also, since stents tend to be long and thin, a camera can only view a small section of the stent at sufficient magnification to effectively perform inspection.
This can result in inspection cycle times of ten minutes or more.
In addition to problems in speed, these vision systems also have difficulty with accuracy.
Since the stents are highly reflective, intense hot spots and glare on the image can cause false or inaccurate measurements.
While, overall, the sapphire rod approach probably results in an improvement over the results obtainable with a ring light, sapphire rod illuminators have their own set of problems.
One problem that frequently occurs due to the highly polished surface and curved profile of the stent, or if the stent has slanting side walls, is that the walls themselves can be illuminated and appear as bright as the background sapphire which in turn makes the stent appear smaller than it actually is.
Current manual and automatic systems can be used to measure wall thickness, but problems arise in the accuracy and repeatability of the current methods.
Again glare and uneven illumination from a fiber optic ring light make it difficult to properly image a stent.
On densely cut stents it can be hard to find an area on the stent that is open enough to view the sidewall while looking down on stent along its length.
Contact methods utilizing a micrometer are also generally problematic for measuring wall thickness.
Again this is a time consuming manual method and would benefit from automation.
Method used
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[0030] Referring to FIG. 1, the inventive inspection system 10 allows one to more accurately and more quickly inspect stents 12, other precision cut metal tubes, and similar objects for dimensional conformance to a manufacturing specification and verify the overall quality of stent 12.
[0031] Most specifically, FIG. 1 shows a stent inspection system 10. First, stent 12 to be inspected, is mounted on a translucent sapphire rod or mandrel 14. This rod is best made of sapphire due to the structural rigidity of sapphire and the suitability of sapphire to being machined, although other translucent materials can be utilized with varying results. The sapphire rod is then fine ground to an even frosted finish. The sapphire rod is then mounted in a highly concentric bushing. The bushing should be concentric to the rod within 0.0002 of an inch. The assembly of the rod and bushing is referred to herein as mandrel 14. For the system to work properly, mandrel 14 must be assembled quite precisely...
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An automatic system for illuminating, inspecting and measuring stents and other precision cut tubes and components made of a: a linear array electronic camera with a lens, a light source to provide necessary illumination to create an image on said linear array camera, mandrel onto which the tube is mounted during inspection, a rotary stage for rotating the mandrel, and a computer based electronic imaging system that creates a line-by-line image of stent as it rotates under said camera.
Description
TECHNICAL FIELD [0001] This invention relates to an automatic system for illuminating, inspecting and measuring objects, such as cardiovascular stents and other precision cut tubes and components, for the purpose of maintaining quality control. BACKGROUND [0002] Stents are small, intricately cut tubes, generally made of materials such as stainless steel. Cardiovascular stents, are permanently placed in a blood vessel to act as scaffolding to keep an occluded artery open. In use, cardiovascular stents are inserted into the artery on a catheter and are typically deployed by expanding a very small balloon at the end of the catheter upon which the stent is mounted. [0003] Cardiovascular stents must meet stringent requirements to work properly. If the stent contains any rough or sharp edges, it will damage blood cells or the blood vessel in which it is inserted. This can lead to further atherosclerotic plaquing, emboli or thrombi, and result in potentially life threatening situations. Th...
Claims
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Login to View More IPC IPC(8): A61F2/06A61F2/90G01B11/02G01B11/08G01N21/952
CPCA61F2/91A61F2/915A61F2002/91533G01N21/952A61F2240/008G01B11/024G01B11/08A61F2002/9155
InventorFREIFELD, DANIEL
OwnerFREIFELD DANIEL