ILLUMINATING DEVICE FOR CYLINDRICAL OBJECTS, SURFACE INSPECTION METHOD IMPLEMENTED THEREWITH AND COMPUTER PROGRAM PRODUCT

• US 20090290781A1
• Filed: 02/22/2007
• Published: 11/26/2009
• Est. Priority Date: 02/25/2006
• Status: Abandoned Application

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Klaus, Spinnler, Robert, Couronne, Yannick, Caulier
• Application Number:
  US12/280,524
• Publication Number:
  US 20090290781A1
• Time in Patent Office: Days
• US Class Current: 382/141
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/952 Inspecting the exterior surface of cylindrical bodies or wires G01N21/956 takes precedence
• CPC Class Codes: G01N 2201/061 Sources

Abstract

An illuminating device is provided that includes, but is not limited to a cylindrical lighting unit with a cylindrical slit diaphragm arranged in the interior thereof. The lighting unit includes, but is not limited to a cylindrical light source with a cylindrical diffusor arranged therein, and the slit diaphragm has a cylinder with axially extending slits that are arranged in such a way that incident beams coupled in perpendicular to the slit diaphragm axis (O) converge in a point (M) that is spaced apart from the cylinder axis in the interior of the slit diaphragm through the slits.

Claims

1. An illuminating device, comprising:

a cylindrical lighting unit;

a cylindrical slit diaphragm arranged in the interior of the cylindrical lighting unit, the cylindrical lighting unit comprising a cylindrical light source with a cylindrical diffusor arranged therein; and

a cylinder with axially extending slits that are arranged in such a way that incident beams coupled in perpendicular to a slit diaphragm axis (O) converge in a point (M) that is spaced apart from a cylinder axis in an interior of the cylindrical slit diaphragm through the axially extending slits.

2. The illuminating device according to claim 1, wherein the cylindrical lighting unit comprises at least three cylindrical light sources that are arranged within one another.

3. The illuminating device according to claim 1, wherein the cylindrical diffusor comprises at least three opaque bodies that are arranged within one another.

4. The illuminating device according to claim 1, wherein the cylindrical lighting unit and the cylindrical slit diaphragm are arranged coaxially to one another.

5. The illuminating device according to claim 1, wherein the cylindrical slit diaphragm has a wall thickness of at least about 3 mm.

6. A lighting unit, comprising;

a cylindrical light source with a luminous intensity of at least about 230.000 lux, and a cylindrical diffusor coaxially arranged within the cylindrical light source.

7. The lighting unit according to claim 6, wherein at least three cylindrical light sources are provided and arranged within one another.

8. The lighting unit according to claim 6, further comprising a diffusor comprising at least 3 opaque plastic bodies that are arranged coaxially to one another.

9. A slit diaphragm of cylindrical design comprising

axially extending slits arranged in such a way that incident beams coupled in perpendicular to a slit diaphragm axis (O) converge in a point (M) that is spaced apart from a cylinder axis in an interior of the slit diaphragm through the axially extending slits.

10. A method for detecting defects on the surface of a cylindrical object, wherein said method comprises the following steps:

subjecting the cylindrical object to radiation that is able to produce a pattern of mutually adjacent bright and dark strips on a projection screen;

detecting the radiation reflected by the surface of the cylindrical object in a spatially resolved fashion and acquiring measured values in the form of an image;

calculating a multitude of characteristics for at least a portion of each pixel of the image;

identifying pixels, at which the value of a characteristic lies at least one of above an below a predetermined threshold value;

identifying image areas in which identified pixels of each pixel of the image exceed a predetermined density; and

identifying a defect in areas of the image belonging to at least two different characteristics adjoin sufficiently close.

11. The method according to claim 10, wherein characteristics are only calculated for pixels that were subjected to radiation with a minimum intensity.

12. The method according to claim 10, wherein

at least the distance of the pixel from a selected point of the image is chosen as characteristic.

13. The method according to claim 10, wherein the defect is identified as at least one of a contamination and as a deformation of the object in dependence on at least one selected characteristic.

14. The method according to claim 13, wherein it is deduced that the surface of the object contains a deformation if one of the corresponding characteristics in the areas of the image that adjoin sufficiently close is the deviation of position between the pixel and a predetermined reference point within a mask placed over the image.

15. A computer program product on a computer-readable medium, comprising computer-readable program means that lead a computer to carry out the following steps:

calculating a multitude of characteristics for each pixel of an image or a portion of the pixels of an image consisting of a pattern of mutually adjacent bright and dark strips;

identifying pixels, at which the value of one characteristic lies at least one of above and below a predetermined threshold value,

identifying image areas, in which the identified pixels exceed a predetermined density; and

d) identifying a defect in an area of the image belonging to at least two different characteristics adjoin sufficiently close.

16. The computer program product according to claim 15, wherein characteristics are only calculated for the pixels that were subjected to radiation with a minimum intensity.

17. The computer program product according to claim 15, wherein the defect is identified as at least one of a contamination and a deformation of the object in dependence on the characteristics.