System and method to illuminate and image the inside diameter of a stent
View Patent ↗An optical system is effective to illuminate and scan an interior wall of an object having an interior bore, such as a stent. The system includes a light source, an object support having a light conducting portion, an image taking lens, and a line scan camera. The interior bore and the light conducting portion of the object support are in axial alignment with a center optical axis of the image taking lens. A drive mechanism engages the object without impacting the axial alignment. Various aspect of this optical system include a rotating wheel or transparent plate as the drive mechanism. The object support may be an opaque rod having a light conducting portion or a transparent rod. Electronics associated with this optical system include a rotary encoder engaging the drive system to drive an electric circuit capable of triggering the line scan camera in response to rotation of the object, thereby building a line by line image of the interior bore and the line scan camera connected to a computer-based imaging system effective to identify cosmetic and functional manufacturing defects.
1. An optical system effective to illuminate and scan an interior wall of a mesh object having an interior bore, comprising:
a light source effective to illuminate said interior wall;
a rigid support rod having a diameter effective to prevent collapse of said mesh object;
wherein said support rod has a cross section having an optically clear viewing section that is flanked on a first and a second side by a non-transparent section;
a source of linear motion, having a compliant surface to transfer motion to said mesh object, that rotates said mesh object around said support rod;
an image taking lens disposed externally to said mesh object and configured to view said interior wall through said optically clear viewing section of said support rod and having a numerical aperture greater than 0.1 so that when said interior wall is in focus, an exterior wall on an opposing side of said mesh object is out of focus; and
a camera optically aligned with said image taking lens and effective to scan said interior wall.
2. The optical system of claim 1 wherein said light source is out of optical alignment with said camera and said between said mesh object and said image taking lens.
3. The optical system of claim 1 wherein said support rod includes a beam splitter effective to reflect light from said light source onto said interior wall.
4. The optical system of claim 1 wherein said support rod and said source of linear motion are effective to hold said mesh object with sufficient precision to maintain said interior wall in focus.
5. The optical system of claim 4 wherein said source of linear motion is a flat plate.
6. The optical system of claim 5 wherein said flat plate is clear.
7. The optical system of claim 5 wherein said flat plate is translucent.
8. The optical system of claim 1 wherein said mesh object is a stent.
9. The optical system of claim 1 wherein said source of linear motion is coupled to an encoder driving an electronics circuit capable of triggering said camera in response to rotation of said mesh object about said support rod.
10. The optical system of claim 1 wherein said camera is a line scan camera effective to build a line by line image of said interior bore.
11. The optical system of claim 1 wherein said taking lens has an optical design that compensates for any optical distortion caused by the support rod.