Inspection apparatus with improved detection of surface defects over large and curved surfaces

• US 5,237,404 A
• Filed: 06/28/1991
• Issued: 08/17/1993
• Est. Priority Date: 06/28/1990
• Status: Expired due to Fees

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Makimae, Tatsumi, Ishiide, Hidenori, Sugihara, Tsuyoshi, Utsunomiya, Akinori, Tanaka, Kazumoto
• Primary Examiner(s): Kostak, Victor R.
• Application Number:
  US07/723,174
• Time in Patent Office: 781 Days
• Field of Search: 358/106, 358/101, 358/107, 356/387, 356/349, 356/237, 356/372, 356/376, 250/572, 901/46, 901/47
• US Class Current: 348/128
• CPC Class Codes: G01B 11/303 using photoelectric detection means
• CPC Class Codes: G01N 2021/8845 Multiple wavelengths of illumination or detection
• CPC Class Codes: G01N 2021/8887 based on image processing techniques
• CPC Class Codes: G01N 2021/9518 using a surface follower, e.g. robot
• CPC Class Codes: G01N 21/9515 Objects of complex shape, e.g. examined with use of a surface follower device measuring contours and curvatures G01B11/24

Abstract

A surface defect inspection apparatus includes a light radiation source, arranged to oppose a surface to be inspected serving as a mirror surface, for radiating light having a predetermined change pattern toward the surface to be inspected, a camera mechanism for receiving an image of the light radiation source, reflected by the surface to be inspected and forming a received-light image corresponding to the change pattern of the light radiation source, and a discriminator for discriminating a surface defect portion on the surface to be inspected by discriminating a portion whose change pattern is different from the change pattern on the basis of the received-light image formed by the camera mechanism.

Claims

1. A surface defect inspection apparatus, which comprises:

light radiation means, arranged to oppose a surface to be inspected serving as a mirror surface, for radiating light having a predetermined change pattern toward said surface to be inspected;

imaging means for imaging an image of said light radiation means reflected by said surface to be inspected and forming a received-light image corresponding to the change pattern of said light radiation means;

discriminating means for discriminating a surface defect portion at which a variation amount of said change pattern in the received-light image is different from that at a surrounding portion of the surface defect.

2. The apparatus according to claim 1, wherein said light radiation means radiates light having a luminous intensity distribution including high-level and low-level portions toward said surface to be inspected.

3. The apparatus according to claim 2, wherein

said light radiation means radiates, toward said surface to be inspected, light having a luminous intensity distribution which is set so that a luminous intensity is gradually changed from high level to low level along a predetermined direction.

4. The apparatus according to claim 3, wherein

said imaging means images the image of said light radiation means reflected by said surface to be inspected, and forms the received-light image corresponding to the luminous intensity distribution of said light radiation means.

5. The apparatus according to claim 4, wherein said discriminating means discriminates a portion whose change state of the luminous intensity distribution is different from a change state of a surrounding portion on the basis of the received-light image formed by said imaging means so as to detect the discriminated portion as the surface defect portion on said surface to be inspected.

6. The apparatus according to claim 1, wherein

said imaging means comprises a camera having a view field which is set to image the image of said light radiation means reflected by said surface to be inspected over an entire formation range of the received-light image.

7. The apparatus according to claim 6, wherein

said imaging means comprises video signal generation means for converting the received-light image into a video signal.

8. The apparatus according to claim 2, wherein

said light radiation means radiates light to have a luminous intensity distribution which is set such that high-level and low-level portions alternately appear.

9. The apparatus according to claim 8, wherein

said imaging means images the image of said light radiation means reflected by said surface to be inspected, and forms the received-light image having bright and dark portions corresponding to the luminous intensity distribution of said light radiation means.

10. The apparatus according to claim 9, wherein

said discriminating means discriminates a portion whose brightness is considerably different from a surrounding portion in each of the bright and dark portions on the basis of the received-light image formed by said imaging means so as to detect the discriminated portion as the surface defect portion of said surface to be inspected.

11. The apparatus according to claim 1, wherein

said light radiation means radiates, toward said surface to be inspected, light having a wavelength distribution which is set such that a wavelength is gradually changed from a long wavelength to a short wavelength in a predetermined direction.

12. The apparatus according to claim 11, wherein

said imaging means images the image of said light radiation means reflected by said surface to be inspected, and forms the received-light image having a wavelength distribution corresponding to the wavelength distribution of said light radiation means.

13. The apparatus according to claim 12, wherein said discriminating means discriminates a portion whose change state of the wavelength distribution is different from a change state of a surrounding portion on the basis of the received-light image formed by said imaging means so as to detect the discriminated portion as the surface defect portion on said surface to be inspected.

14. The apparatus according to claim 11, wherein

a wavelength of light radiated by said light radiation means is set in a visible light region.

15. The apparatus according to claim 1, wherein

said light radiation means radiates, toward said surface to be inspected, light having a color pattern in which colors are sequentially changed in a predetermined order along a predetermined direction.

16. The apparatus according to claim 15, wherein

said imaging means images the image of said light radiation means reflected by said surface to be inspected, and forms the received-light image having a color pattern corresponding to the color pattern of said light radiation means.

17. The apparatus according to claim 16, wherein said discriminating means discriminates a portion whose change state of the color pattern is different from a change state of a surrounding portion on the basis of the received-light image formed by said imaging means so as to detect the discriminated portion as the surface defect portion on said surface to be inspected.

18. A surface defect inspection apparatus comprising:

light radiation means, arranged to oppose a surface to be inspected serving as a mirror surface, for radiating light having a predetermined change pattern toward said surface to be inspected;

imaging means for imaging an image of said light radiation means reflected by said surface to be inspected and forming a received-light image corresponding to the change pattern of said light radiation means; and

image processing means for detecting a surface defect portion on said surface to be inspected by discriminating a portion whose change pattern is different from the change pattern on the basis of the received-light image formed by said imaging means,

wherein said light radiation means radiates light having a luminous intensity distribution including high-level and low-level portions toward said surface to be inspected,

wherein said light radiation means radiates, toward said surface to be inspected, light having the luminous intensity distribution which is set so that a luminous intensity is gradually changed from high level to low-level along a predetermined direction,

wherein said imaging means images the image of said light radiation means reflected by said surface to be inspected, and forms the received-light image corresponding to the luminous intensity distribution of said light radiation means, and

wherein when the change state of the luminous intensity distribution of the portion detected as the surface defect portion is the same as the change state of the luminous intensity distribution of the surrounding portion, said image processing means discriminates that the surface defect portion is formed in a convex shape, and when the change state of the luminous intensity distribution of the portion detected as the surface defect portion is opposite to the change state of the luminous intensity distribution of the surrounding portion, said image processing means discriminates that the surface defect portion is formed in a concave shape.

19. A surface defect inspection apparatus comprising:

light radiation means, arranged to oppose a surface to be inspected serving as a mirror surface, for radiating light having a predetermined change pattern toward said surface to be inspected;

imaging means for imaging an image of said light radiation means reflected by said surface to be inspected and forming a received-light image corresponding to the change pattern of said light radiation means; and

image processing means for detecting a surface defect portion on said surface to be inspected by discriminating a portion whose change pattern is different from the change pattern on the basis of the received-light image formed by said imaging means,

wherein said imaging means comprises a camera having a view field which is set to image the image of said light radiating means reflected by said surface to be inspected over an entire formation range of the received-light image,

wherein said imaging means comprises video signal generation means for converting the received-light image into a video signal, and

wherein said image processing means processes the video signal output from said video signal generation means, and discriminates a position and a three-dimensional pattern of the surface defect portion on the basis of a timing at which the processed value exceeds a predetermined value, and a change state of the processed value.

20. A surface defect inspection apparatus comprising:

light radiation means, arranged to oppose a surface to be inspected serving as a mirror surface, for radiating light having a predetermined change pattern toward said surface to be inspected;

imaging means for imaging an image of said light radiation means reflected by said surface to be inspected and forming a received-light image corresponding to the change pattern of said light radiation means;

image processing means for detecting a surface defect portion on said surface to be inspected by discriminating a portion whose change pattern is different from the change pattern on the basis of the received-light image formed by said imaging means,

wherein said light radiation means radiates, toward said surface to be inspected, light having a wavelength distribution which is set such that a wavelength is gradually changed from a long wavelength to a short wavelength in a predetermined direction,

wherein said imaging means images the image of said light radiation means reflected by said surface to be inspected, and forms the received-light image having a wavelength distribution corresponding to the wavelength distribution of said light radiation means,

wherein said image processing means discriminates a portion whose change state of the wavelength distribution is considerably different from a change state of a surrounding portion on the basis of the received-light image formed by said imaging means so as to detect the discriminated portion as the surface defect portion on said surface to be inspected, and

wherein when the change state of the wavelength distribution of the portion detected as the surface defect portion is the same as the change state of the wavelength distribution of the surrounding portion, said image processing means discriminates that the surface defect portion is formed in a convex shape, and when the change state of the wavelength distribution of the portion detected as the surface defect portion is opposite to the change state of the wavelength distribution of the surrounding portion, said image processing means discriminates that the surface defect portion is formed in a concave shape.

21. A surface defect inspection apparatus comprising:

light radiation means, arranged to opposite a surface to be inspected serving as a mirror surface, for radiating light having a predetermined change pattern toward said surface to be inspected;

imaging means for imaging an image of said light radiation means reflected by said surface to be inspected and forming a received-light image corresponding to the change pattern of said light radiation means;

image processing means for detecting a surface defect portion on said surface to be inspected by discriminating a portion whose change pattern is different from the change pattern on the basis of the received-light image formed by said imaging means,

wherein said light radiation means radiates, toward said surface to be inspected, light having a color pattern in which colors are sequentially changed in a predetermined order along a predetermined direction,

wherein said imaging means images the image of said light radiation means reflected by said surface to be inspected, and forms the received-light image having a color pattern corresponding to the color pattern of said light radiation means,

wherein said image processing means discriminates a portion whose change state of the color pattern is different from a change state of a surrounding portion on the basis of the received-light image formed by said imaging means so as to detect the discriminated portion as the surface defect portion on said surface to be inspected, and

wherein when the change state of the color pattern of the portion detected as the surface defect portion is the same as the change state of the color pattern of the surrounding portion, said image processing means discriminates that the surface defect portion is formed in a convex shape, and when the change state of the color pattern of the portion detected as the surface defect portion is opposite to the change state of the color pattern of the surrounding portion, said image processing means discriminates that the surface defect portion is formed in a concave shape.