DEVICE AND METHOD FOR OPTICALLY INSPECTING AND ANALYZING STENT-LIKE OBJECTS

Abstract

The device has an apparatus for rotatably holding and positioning at least one stent-like object and a unit for illuminating at least inner and outer surfaces thereof, including at least a wide field epi illumination device and a diffuse back illumination device for simultaneously illuminating the stent-like object. The illumination unit may further include diffuse side illumination device for inspecting side surfaces of the stent-like object. An apparatus for acquiring images of the stent-like object including at least one microscope objective lens and at least one camera is also provided.

Claims

1. A device for optically inspecting and analysing at least one portion of at least inner and outer surfaces of stent-like objects and determining at least their critical dimensions, edge roundness and surface defects, the device comprising: an apparatus for holding and positioning the at least one stent-like object and a unit for illuminating the at least inner and outer surfaces of the stent-like object, wherein the device further comprises an apparatus for acquiring images of the stent-like object, the image acquiring apparatus comprising at least one microscope objective lens and at least one camera, and wherein the unit for illuminating the stent-like object comprises at least a wide field epi illumination device coaxial with respect to an optical axis of the microscope objective lens, and a diffuse back illumination device, whereby the wide field epi coaxial illumination device and the diffuse back illumination device are adapted for illuminating the stent-like object simultaneously.

2. The device of claim 1, wherein the unit for illuminating the stent-like object further comprise a diffuse side illumination device suitable for inspecting the side surfaces of the stent-like object and analysing at least its critical dimensions, edge roundness and surface defects.

3. The device of claim 1, wherein the device further comprises an electronic image-processing system capable of analysing images acquired by the image acquiring apparatus.

4. The device of claim 1, wherein the device further includes an apparatus for projecting at least one structured illumination pattern onto a surface of the stent-like object suitable for determining at least one of the topography of the surface and the thickness of the coating in the surface.

5. The device of claim 1, wherein the microscope objective lens is an interferometric lens suitable for determining at least one of the topography of the surface of the stent-like object the roughness of the surface of the stent-like object and the thickness of the coating of the surface of the stent-like object.

6. The device of claim 4, wherein the device further includes a vertical scanning device for obtaining a series of images in different planes of the stent-like object.

7. The device of claim 1, wherein the apparatus for holding and positioning the stent-like object is suitable for rotatably holding and positioning the stent-like object.

8. The device of claim 7, wherein the apparatus for holding and positioning the stent-like object comprises first and second rollers arranged at least substantially parallel to each other and adapted to rotate in the same directions as each other, a third roller resting on the first and second rollers and rotatable with the first and second rollers, and a tube member protruding concentrically outward from the third roller and adapted for receiving the stent-like object by surrounding it, with the tube member being made from a material that allows light to pass through it.

9. The device of claim 1, wherein at least one of the wide field epi coaxial illumination device and the diffuse back illumination means device comprises at least one LED.

10. The device of claim 1, wherein the at least one camera of the image acquiring apparatus is adapted for operating as a line scan camera.

11. A method for optically inspecting and analysing a stent-like object, the method comprising the steps of: positioning the stent-like object relative to an illumination unit such that at least one portion of a surface of the stent-like object can be illuminated by the illumination unit and focused by an image acquiring apparatus; wherein the method further comprises the steps of: illuminating the stent-like object simultaneously by a wide field epi illumination device coaxial with respect to an optical axis of the image acquiring apparatus and a diffuse back illumination device; focusing at least one portion of the stent-like object using the image acquiring apparatus; and acquiring images of a surface of the stent-like object line by line while rotating the stent-like object around its longitudinal axis such that a focused unrolled section image of the stent-like object is obtained.

12. The method of claim 11, wherein the method includes the steps of: positioning the stent-like object relative to the illumination unit and the image acquiring apparatus such that the optical axis of the wide field epi coaxial illumination device and the image acquiring apparatus is displaced laterally by a distance to the longitudinal axis of the stent-like object and a side surface of the stent-like object is displaced vertically by a distance; focusing a central point of the side surface of the stent-like object; simultaneously illuminating the side surface of the stent-like object by a diffuse side illumination device and a diffuse back illumination device; and rotating the stent-like object around its longitudinal axis in order to acquire images of the side surface of the stent-like object line by line such that an unrolled side surface image of the stent-like object is obtained.

13. The method of claim 12, wherein the displacement of the optical axis relative to the longitudinal axis of the stent-like object corresponds to the value of a distance from the longitudinal axis of the stent-like object to a central point multiplied by the sine of an angle between the optical axis and a line passing through the longitudinal axis of the stent-like object and the central point, and wherein the displacement of a vertical focus position corresponds to the value of the distance multiplied by one minus the cosine of the angle.

14. The method of claim 13, wherein the angle between the optical axis and a line passing through the longitudinal axis of the stent-like object and the central point is in the range of about 30 to about 50.

15. The method of claim 11, wherein the method further includes obtaining information about at least one of critical dimensions of the surface of the stent-like object, edge roundness of the surface of the stent-like object, and surface defects of the surface of the stent-like object from the acquired images of the stent-like object.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Particular examples of the present device and method for optically inspecting and analysing stent-like objects will be described in the following by way of non-limiting examples. The description is given with reference to the appended drawings.

[0067] In said drawings:

[0068] FIG. 1 is a diagrammatic general view of one example of the present device for optically inspecting and analysing stent-like objects;

[0069] FIG. 2 is a diagrammatical view of one example of the present device for optically inspecting and analysing stent-like objects showing how the present method is carried out when an epi illumination device and back illumination device are acting simultaneously;

[0070] FIG. 3 is a diagrammatical view of one example of the present device for optically inspecting and analysing stent-like objects showing how the present method is carried out when an epi illumination device, back illumination device and side illumination device are used;

[0071] FIG. 4 is a diagrammatical top view of one preferred example of the holding and positioning apparatus of the stent; and

[0072] FIG. 5 is a diagrammatical elevational view of the preferred example of the holding and positioning device of the stent shown in FIG. 4.

DETAILED DESCRIPTION OF EXAMPLES

[0073] According to the non-limiting examples shown in FIGS. 1-5 of the drawings, a device for optically inspecting and analysing stent-like objects will be described hereinbelow. The device and method described according to the specific examples shown are for inspecting and analysing stents 400. A stent 400 is therefore used herein as a non-limiting example of a stent-like object.

[0074] FIG. 1 shows a diagrammatic general example of the device 100. In this example, the present device 100 comprises a sensor head 110 that is capable of providing both 2D and 3D imaging capabilities.

[0075] The sensor head 110 includes an illumination unit that is described in detail below. The illumination unit in the sensor head 110 is adapted to project light into portions of the outer surfaces O and portions of the inner surfaces I of the stent 400.

[0076] The sensor head 110 further includes an apparatus for acquiring images of portions of the surfaces O, I of the stent 400. In the particular example shown, the image acquiring apparatus includes a microscope objective lens 610.

[0077] The sensor head 110 is capable of providing 3D imaging capabilities through two different examples.

[0078] In a first example the sensor head 110 is provided with a vertical scanning stage device 235 for moving the sensor head 110 vertically in order to obtain images of the stent 400 in different planes. The sensor head 110 is thus capable of obtaining high-speed focused color images of the outer surface O, the inner surface I and the side surface S of the stent 400. In this example, the sensor head 110 is also provided with standard microscope objective lens 610 and an arrangement 30E for projecting a structured illumination pattern 660 onto a surface I, O of the stent 400. Such structured illumination pattern 600 is suitable for determining the topography of the outer surface O, the inner surface I and the side surfaces of the stent 400 and/or the thickness of the coating in said surfaces I, O, S of the stent 400. The structured illumination arrangement 30E comprises a light source, which in the example shown includes a LED 630, a first lens, which in the example shown is a collimator 640 for concentrating the light from the LED 630, a second lens 650, a structured illumination pattern 660, and a beam splitter cube 702.

[0079] In a second example, the 3D imaging capabilities can be obtained with a sensor head 110 provided with the vertical scanning stage device 235 for moving the sensor head 110 vertically. In contrast to the previous example, the sensor head 110 now employs an interferometric microscope objective lens. The interferometric microscope objective lens is suitable for determining the topography and/or the roughness of surfaces I, O S of the stent 400, and/or the thickness of the coating of the surfaces I, O S of the stent 400. No structured illumination pattern projecting arrangement 30E is required in this specific example.

[0080] In all cases, a high-resolution line scan camera 620 is provided in the sensor head 110. Adjacent to the line scan camera 620 is a field lens 625 for changing the size of the image.

[0081] The illumination unit comprises a wide field epi illumination device 30E. The wide field epi illumination device 30E is adapted for directing light substantially vertically from the top of the device 100 and coaxially with respect to the optical axis L of the microscope objective lens 610.

[0082] For this purpose, the wide field epi illumination device 30E comprises a light source, which in the particular example shown includes a LED 630, a first lens, which in the example shown is a collimator 640 for concentrating the light from the LED 630, a second lens 650 and a beam splitter cube 701.

[0083] The beam splitter cubes 701, 702 are adapted for coupling the illumination device 30E, 30E with the image acquiring device.

[0084] The structured illumination device 30E allows the topography of the inner surface I and the outer surface O of the stent 400 and/or thickness of the coating in said inner and outer surfaces I, O of the stent 400 to be determined. It is to be noted that the wide field epi illumination device 30E and the structured illumination device 30E are operated alternatively, that is, in use, when the wide field epi illumination device 30E is activated, the arrangement 30E for projecting a structured illumination pattern 660 is not activated and vice versa.

[0085] According to the above, two illumination branches L1, L2 and an imaging branch L3 are defined in the sensor head 110.

[0086] The illumination unit of the device 100 further comprises a diffuse back illumination device 30B as shown in FIGS. 1, 2, 3 and 5 of the drawings. Said back illumination device 30B is adapted for directing light substantially vertically from the bottom of the device 100. The diffuse back illumination device 30B in the present implementation comprises a high intensity linear diffuse LED illuminator having a 10 cm long green LED bar 30BL and a diffusor arranged on a front portion. The diffusor is adapted to cause every point of the light emitting surface in the LED 30BL to emit light in all directions to the stent 400.

[0087] The device 100 further comprises a high precision electromechanical module or rolling stage. It includes an apparatus 200 for rotatably holding and positioning a stent 400 to be inspected.

[0088] The holding and positioning apparatus 200, in one preferred example, of which has been shown in FIGS. 4 and 5 of the drawings, comprises a first roller 210 and a second roller 220. The first and second rollers 210, 220 are cylindrical bodies made of a metal core with a high precision outer surface coating.

[0089] The rollers 210, 220 are mounted on a horizontal support table 230. The horizontal support table 230 can be moved on a horizontal plane. The rollers 210, 220 are mounted on the support table 230 with their respective longitudinal axis 211, 221 arranged substantially parallel to each other. The rollers 210, 220 are arranged separated from each other by a distance suitable for receiving the stent 400 to be inspected between them, with the stent 400 resting freely on the high precision surfaces of the rollers 210, 220. The rollers 210, 220 are mounted on the support table 230 such that they can be rotated in the same direction to each other through a suitable drive, not shown, around their respective longitudinal axis 211, 221. Rotation of the rollers 210, 220 around their respective longitudinal axis 211, 221 by said drive causes the stent 400 to be rotated around its longitudinal axis E.

[0090] FIGS. 4 and 5 show a preferred example of the holding and positioning apparatus 200. In this case, the holding and positioning apparatus 200 further comprises a third roller 300 in addition to the above mentioned rollers 210, 220. The third roller 300 of the holding and positioning apparatus 200 is supported on the first and second rollers 210, 220 such that it can be freely rotated. The third roller 300 can be rotated by the first and second rollers 210, 220 around its longitudinal axis 301.

[0091] A tube member 500 is provided protruding concentrically outward from the third roller 300. Such tube member 500 is a thin walled glass capillary tube 500 that is suitably designed such as the light is allowed to pass through. For this purpose, in this case, the tube member 500 is made of a transparent material. The capillary tube member 500 is suitably sized for receiving the stent 400 in a way that the stent 400 can be inserted around it surrounding the outer surface of the tube member 500.

[0092] As the first and second rollers 210, 220 are rotated by the drive, the third roller 300 placed thereon is caused to be rotated. Consequently, the tube member 500 together with the stent 400 are also caused to be rotated. An accurate rotation of the stent 400 is allowed to be performed irrespective of any imperfections on the struts of the stent 400 that is being inspected.

[0093] The above example of the holding and positioning apparatus 200 allows the stent 400 to be loaded and unloaded easily by the operator as well as to be placed in a suitable given longitudinal, radial and angular positions with an extremely high overall accuracy, which may be of the order of 1 micron or even less.

[0094] Finally, in the present implementation of the device 100, the illumination unit further comprises a side illumination device 30S. Such side illumination device 30S is adapted for directing light to at least portions of the side surfaces or side walls S of the stent 400.

[0095] As defined above, the side surfaces or side walls S are surfaces of the stent 400 substantially parallel to the optical axis L of the wide field epi coaxial illumination device 30E and the image acquiring apparatus when said optical axis L crosses the longitudinal axis E of the stent E.

[0096] As with the outer surfaces O and the inner surfaces I of the stent 400, the side illumination device 30S allows at least portions of the side surfaces S of the stent 400 to be inspected, and critical dimensions CD of the strut to be analysed. In addition, information about edge roundness and surface defects in such portions of the side surfaces S of the stent 400 is also provided.

[0097] At least the wide field epi coaxial illumination device 30E and the diffuse back illumination device 30B are combined with each other such that, in use, they are activated simultaneously for illuminating portions of the outer surfaces O and the inner surfaces I of the stent 400. The dual combined simultaneous illumination of the surfaces or walls I, O of struts of the stent allows said inspection information to be accurately obtained.

[0098] In the specific example shown, an electronic image-processing system is provided. This electronic image-processing system is capable of analysing the images that are acquired by the image acquiring apparatus. The operator can carry out measurements on the stent 400 that is being inspected so that subsequent analysis of collected data can be carried out in order to take final decisions about the acceptance or the rejection of the inspected stent 400.

[0099] The inspection process performed by the device 100 is controlled by a software application. This software application, through a corresponding graphic user interface, provides data analysis to the operator.

[0100] For inspecting and analysing a stent 400 through the present method using the above described device 100, the operator loads a stent 400 on the holding and positioning device 200 of the device 100. When using the preferred example of the holding and positioning device 200, this is carried out by carefully fitting the stent 400 around the tube member 500 of the third roller 300 and placing the third roller 300 onto the first and second rollers 210, 220. The stent 400 is appropriately positioned by the horizontal support table 230, the vertical scanning stage device 235 and the rollers 210, 220, 300 such that one portion of the inner surface I or the outer surface O of the stent 400 is illuminated by the wide field epi illumination device 30E and the diffuse back illumination device 30B and such that said portion of the inner surface I or the outer surface O of the stent 400 is suitably focused by the image acquiring apparatus. This is diagrammatically shown in FIG. 2.

[0101] Once the stent 400 has been properly positioned relative to the illumination unit 30E, 30B and the image acquiring apparatus, the stent 400 is illuminated simultaneously by the wide field epi coaxial illumination device 30E and by the diffuse back illumination device 30B and focused by the image acquiring apparatus. Then, the drive causes the rollers 210, 220, and consequently the third roller 300 with the tube member 500, to be rotated so that the stent 400 that is fitted around the tube member 500 is also rotated around its longitudinal axis E. As shown in FIGS. 4 and 5, the longitudinal axis E of the stent 400 coincides with the longitudinal axis 301 of the third roller 300. As the stent 400 is rotated around its longitudinal axis E, images of the inner surfaces I and the outer surfaces O of the stent 400 are acquired line by line by the high resolution line scan camera 620. Inner and outer focused unrolled section images of the stent 400 are thus obtained which can be displayed to the operator through a display monitor.

[0102] For inspecting at least one portion of the side surfaces S or side walls of the stent 400, the stent 400 is loaded on the holding and positioning apparatus 200 by the operator as stated above such that the stent 400 is positioned in a way that the optical axis L of the wide field epi coaxial illumination device 30E and the image acquiring apparatus is displaced by a determined lateral distance or displacement y. Said lateral displacement y is defined by a horizontal distance of the optical axis L to the longitudinal axis E of the stent 400 as shown in FIG. 3. It may be determined through the formula: y=A.Math.Sin . A relative vertical displacement z of the stent 400 is carried out until the focus position is reached. Said vertical displacement z is defined by a vertical distance travelled by a position of the side surface S of the stent 400 as shown in FIG. 3. It may be determined through the formula: z=A (1cos ).

[0103] In both cases a is the angle between the optical axis L and a line passing through the longitudinal axis E of the stent 400 and a central point M of the side surface S of the stent 400. In a preferred example the angle lies in the range of about 30 to about 50 and most preferably the angle is of about 40. A is the distance from the longitudinal axis E of stent 400 to the central point M of the side surface S of the stent 400, as shown in FIG. 3 of the drawings. The distance A may be of course defined through the outer radius R of the stent 400 or through the inner radius R.sub.1 of the stent 400. In the first case, the distance A can be determined through the formula:

[00001]$A=R-\frac{\mathrm{CD}}{2}$

while in the second case, the distance A can be determined through the formula

[00002]$A=R_i+\frac{\mathrm{CD}}{2}$

wherein, CD is the critical dimension of the side surfaces or side walls S of the stent 400 that in the present example corresponds to its lateral dimension, i.e. its thickness, and R.sub.1 is the inner diameter of the stent 400 as stated above.

[0104] The central point M of the side surface S of the stent 400 is then focused by the image acquiring apparatus. The side surface S of the stent 400 is simultaneously illuminated by the diffuse side illumination device 30S and the diffuse back illumination device 30B. Then, the drive causes the rollers 210, 220, 300 to rotate so that the stent 400 fitted around the tube member 500 is rotated around its longitudinal axis E. As the stent 400 is rotated, images of its side surface S are acquired line by line by the high resolution line scan camera 620. This results in that side unrolled section images of the stent 400 are obtained which can be also displayed to the operator through the display monitor.

[0105] From the acquired images of the stent 400 information is provided, e.g. displayed, to the operator about the critical dimension CD of the inner, outer and side surfaces I, O, S of the stent 400, the edge roundness of the struts of the stent 400, surface defects in surfaces I, O, S of the stent 400, etc. Ultimately, the operator can make the decision on the acceptance or rejection of the stent 400 from said information.

[0106] Although only a number of particular examples of the present device and method have been disclosed herein, it will be understood by those skilled in the art that other alternative examples and/or uses as well as obvious modifications and equivalents are possible. The present disclosure covers all possible combinations of the particular examples described herein.

[0107] The scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow.

[0108] Reference signs related to drawings and placed in parentheses in a claim are solely for attempting to increase the intelligibility of that claim. Such reference signs therefore shall not be construed as limiting the scope of the claim.