METHOD AND APPARATUS FOR ILLUMINATING MATERIAL FOR AUTOMATED INSPECTION

• US 20080198602A1
• Filed: 01/21/2008
• Published: 08/21/2008
• Est. Priority Date: 02/16/2007
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Floeder, Steven P., BRITTAIN, Kenneth G.
• Granted Patent: US 8,072,593 B2
• Time in Patent Office: Days
• US Class Current: 362/253
• CPC Class Codes: G01N 2021/8822 Dark field detection
• CPC Class Codes: G01N 2021/8832 Structured background, e.g. for transparent objects
• CPC Class Codes: G01N 2021/8841 Illumination and detection on two sides of object
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/896 Optical defects in or on transparent materials, e.g. distortion, surface flaws in conveyed flat sheet or rod for other objects G01N21/958

Abstract

A lighting configuration that is a combination of far dark field lighting and a modified dark stripe lighting is disclosed. The novel combination provides a more robust detection of flaws on, e.g. a moving web of transparent film, than either would provide alone or through a summation of their individual parts.

Claims

1. A system for illuminating a transparent, or semi-transparent, or a combination thereof, sheet material for inspection by an optical receiving device, comprising:

a direct source for providing light on the transparent material in the direction of the camera;

a dark stripe positioned between the direct source and the camera;

at least a first dark field source for providing light on the transparent material at an angle to the camera.

2. The illumination system according to claim 1 further comprising a second dark field source for providing light on the transparent material at a different angle from the camera than provided by the first dark field source.

3. The illumination system according to claim 2 wherein the direction of illumination of the direct source is normal to the plane of the transparent sheet material.

4. The illumination system according to claim 3 wherein the angle between the direction of illumination of the first dark field source is at an angle of between about 10 to 50 degrees from normal to the plane of the transparent sheet material

5. The illumination system according to claim 4 wherein the angle between the direction of illumination of the second dark field source is at an angle of between about 10 to 50 degrees from normal to the plane of the transparent sheet material

6. The illumination system according to claim 5 further comprising a lens positioned between the first and the second dark field sources and the transparent sheet material.

7. The illumination system according to claim 6 wherein the first and the second dark field sources are fiber light lines, and further wherein the lenses are cylindrical lenses.

8. The illumination system according to claim 1 wherein the width of the dark stripe is approximately as wide as the imaging width of the camera.

9. The illumination system according to claim 1 wherein the direct source is a fluorescent source, an LED source, or a source coupled to a fiber-optic device.

12. The illumination system according to claim 1 further comprising a third or more dark field sources for providing light on the transparent material at a different angles from the camera than provided by the first or second dark field sources.

13. The system of claim 8, wherein the width of the dark stripe is approximately 1-25 times as wide as the imaging width of the camera.

10. A method of making an illumination system for illuminating a transparent sheet material for inspection by a camera, comprising:

providing a direct source for providing light on the transparent material in the direction of the camera;

providing a dark stripe positioned between the direct source and the camera;

wherein at least a first dark field source for providing light on the transparent material at an angle to the camera.

11. A method of illuminating a sheet material to inspect it for anomalies, comprising:

directing a light source on a transparent material in the direction of an optical receiving device;

positioning a dark stripe between the light source and the optical receiving device;

directing a dark field source on the transparent material at an angle to the camera.