DEFECT INSPECTION SYSTEM AND METHOD

• US 20160266046A1
• Filed: 10/13/2014
• Published: 09/15/2016
• Est. Priority Date: 10/24/2013
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: ZHOU, WEIXI, KUAI, SHUGUANG, JAEGER, MARK CHRISTOPH
• Granted Patent: US 10,036,712 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01N 2021/8809 Adjustment for highlighting flaws
• CPC Class Codes: G01N 21/8803 Visual inspection measuring projectors G01B9/08
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 2201/0633 Directed, collimated illumination
• CPC Class Codes: G01N 2201/12 Circuits of general importance; Signal processing
• CPC Class Codes: H04N 23/00 Cameras or camera modules comprising electronic image sensors; Control thereof

Abstract

A defect inspection system is provided for inspection of defects in the surface of a sample. An array of light sources is used, with different light sources providing light to the sample from different directions. A main direction of illumination is defined with highest intensity, and this direction evolves over time. By providing varying directional illumination instead of blanket illumination, it becomes easier to detect defects.

Claims

1. A defect inspection system for manual visual inspection of surface defects in a sample, comprising:

a lighting system for illuminating the sample surface, comprising an array of light sources formed within a plane, wherein the array of light sources defines a range of illumination directions towards the sample within the plane, which range covers at least 90 degrees; and

a controller for controlling the light sources in the array to gradually vary the intensity of the output of the light sources, wherein at respective points in time within a sequence each light source has a greater intensity than the others such that each point of the sample is illuminated, at the respective points in time within the sequence, with a light distribution having a maximum light source intensity in a single incident direction, and over time the direction in which the maximum light source intensity is provided changes to cover said range.

3. A system as claimed in claim 1, wherein range covers at least 135 degrees, more preferably at least 180 degrees.

6. A system as claimed in claim 1, wherein the controller is adapted to control the light source array to vary the intensity of the light sources with sinusoidal intensity profiles, all with the same period but different phases.

7. A system as claimed in claim 1, wherein the array of light sources comprises a plurality of sub-arrays of light sources, each sub-array formed within a respective plane, the normal direction to the planes for different sub-arrays being arranged in a line.

8. A system as claimed in claim 1, wherein the sample platform is movable relative to the lighting system in a direction along the line perpendicular to the respective planes.

9. A system as claimed in claim 1, comprising a car body panel paintwork inspection system.

16. A system as claimed in claim 1, further comprising a sample platform, wherein the sample platform is movable relative to the lighting system in a direction perpendicular to the plane.

17. A system as claimed in claim 7, wherein the controller is adapted to gradually vary the intensity of the output of the light sources from the sub-array of light sources formed within each respective plane in accordance with a respective sequence, wherein at respective points in time within the respective sequence, each light source from the sub-array has a greater intensity than the other light sources from the sub-array, and

wherein a single incident direction of maximum light source intensity in a light distribution from each sub-array of light sources within each respective plane is different for different respective planes.

2. A defect inspection system for automated inspection of surface defects in a sample, comprising:

a lighting system for illuminating the sample surface, comprising an array of light sources formed within a plane, wherein the array of light sources defines a range of illumination directions towards the sample within the plane, which range covers at least 90 degrees; and

a controller for controlling the light sources in the array to gradually vary the intensity of the output of the light sources, wherein at respective points in time within a sequence each light source has a greater intensity than the others such that each point of the sample is illuminated, at the respective points in time within the sequence, with a light distribution having a maximum light source intensity in a single incident direction, and over time the direction in which the maximum light source intensity is provided changes to cover said range;

at least one camera;

a controller for controlling the camera to take successive images during the light source operation sequence; and

a processor for processing the images to derive at least one difference image, wherein the difference image highlights changes in shadow position caused by randomly located surface defects on an otherwise smooth surface, and to provide defect detection based on the difference image.

4. (canceled)

5. (canceled)

10. A method of providing lighting to a surface of a sample to enable manual visual inspection of defects in the sample, the method comprising:

illuminating the sample surface using an array of light sources formed within a plane, wherein the array of light sources defines a range of illumination directions towards the sample within the plane, which range covers at least 90 degrees; and

controlling the light sources in the array to gradually vary the intensity of the output of the light sources, wherein at respective points in time within a sequence each light source has a greater intensity than the others such that each point of the sample is illuminated, at the respective points in time within the sequence, with a light distribution having a maximum light source intensity in a single incident direction, and over time the direction in which the maximum light source intensity is provided changes to cover said range.

11. A method of providing lighting to a surface of a sample to enable automated inspection of defects in the sample, the method comprising:

illuminating the sample surface using an array of light sources formed within a plane, wherein the array of light sources defines a range of illumination directions towards the sample within the plane, which range covers at least 90 degrees; and

controlling the light sources in the array to gradually vary the intensity of the output of the light sources, wherein at respective points in time within a sequence each light source has a greater intensity than the others such that each point of the sample is illuminated, at the respective points in time within the sequence, with a light distribution having a maximum light source intensity in a single incident direction, and over time the direction in which the maximum light source intensity is provided changes to cover said range;

taking successive camera images during light source operation sequence;

processing the images to derive at least one difference image wherein the difference image highlights changes in shadow position caused by randomly located surface defects on an otherwise smooth surface; and

providing defect detection based on the difference image.

13. A method as claimed in claim 11, comprising controlling the light source array to vary the intensity of the light sources with sinusoidal intensity profiles, all with the same period but different phases.

14. A method as claimed in claim 11, comprising illuminating the sample using an array of light sources comprising a plurality of sub-arrays of light sources, each sub-array formed within a respective plane, the planes for different sub-arrays being parallel.

15. A method as claimed in claim 11, comprising controlling the light sources of the sub-arrays of light sources to illuminate the sample such that a single incident direction of maximum light source intensity in a light distribution from each sub-array of light sources within each respective plane is different for different respective planes.

18. A method as claimed in claim 11, comprising moving the sample relative to the array of light sources in a direction perpendicular to the plane.

12. (canceled)