Ring illumination reflective elements on a generally planar surface

• US 5,828,449 A
• Filed: 07/25/1997
• Issued: 10/27/1998
• Est. Priority Date: 02/26/1997
• Status: Expired due to Term

• Current Assignee: Microscan Systems Inc (Omron Corporation)
• Original Assignee: Acuity Brands, Inc.
• Inventors: King, Steven Joseph, Schurr, George, Ludlow, Jonathan Edmund
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): VIERRA EISENBERG, JASON D
• Application Number:
  US08/898,844
• Time in Patent Office: 459 Days
• Field of Search: 356/327, 356/375, 250/559.05, 250/17, 250/108, 250/134, 250/14, 250/144, 250/146, 582/145-151, 348/126, 348/187, 348/131
• US Class Current: 356/237.1
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/95684 Patterns showing highly reflecting parts, e.g. metallic elements
• CPC Class Codes: H05K 13/0817 Monitoring of soldering processes inspection of solder joints or of printed solder paste G01N21/95684

Abstract

An inspection system and method uses a ring illumination apparatus to illuminate one or more reflective elements, such as solder balls on an electronic component or other protruding surfaces or objects. The ring illumination apparatus includes a substantially ring-shaped light source that provides a substantially even illumination across the one or more reflective elements. An illumination detection device detects light beams reflecting off of the illuminated reflective elements for forming a reflected image. A method of processing the reflected image includes locating one or more edges of each reflected image element representing an illuminated reflective element. The edges of the reflected image elements are located by determining the maximum intensity gradient in the pixels forming the reflected image element. The inspection system and method thereby determines various characteristics such as the absence/presence, location, pitch, size and shape of each reflective element.

Claims

1. A ring illumination apparatus, for illuminating a plurality of reflective elements disposed on a generally planar surface of an article to be inspected and disposed within in a field of view of an illumination detection device, said ring illumination apparatus comprising:

a substantially ring-shaped light source having a predefined diameter, said substantially ring-shaped light source including a plurality of light emitting elements, for generating a plurality of light beams, wherein each of said plurality of light emitting elements are mounted at a predefined angle with respect to a plane parallel to said generally planar surface of said article, such that a centerline of each of said plurality of light emitting elements is disposed at said predefined angle with respect to said generally planar surface of said article to be inspected;

a light reflecting surface disposed generally behind each of said plurality of light emitting elements, for reflecting at least some of said light beams generated by said light emitting elements;

a light diffusing surface disposed generally in front of each of said plurality of light emitting elements, for diffusing at least some of said plurality of light beams as said plurality of light beams are directed toward said article within said field of view; and

wherein said plurality of light beams are directed toward said article in said field of view in a range of angles of illumination with respect to said generally planar surface of said article such that said plurality of reflective elements on said article are illuminated simultaneously and any of said plurality of light beams striking said generally planar surface of said article to be inspected are not reflected to said illumination detection device.

2. The ring illumination apparatus of claim 1 wherein said plurality of reflective elements include an array of solder balls disposed on an electronic component.

3. The ring illumination apparatus of claim 1 wherein said predefined diameter and said predefined angle are defined such that a central light beam area of each of said plurality of light beams is directed across said field of view toward an opposite edge of said field of view on said article to be inspected.

4. The ring illumination apparatus of claim 1 wherein said light reflecting surface includes a white surface proximate to said light emitting elements.

5. The ring illumination apparatus of claim 1 further including a mounting member, said plurality of light emitting elements being mounted to said mounting member in a substantially ring shape.

6. The ring illumination apparatus of claim 5 wherein said mounting member includes an upper mounting portion and a side mounting portion, said plurality of light emitting elements being mounted to at least one of said upper mounting portion and said side mounting portion, at least one of said upper portion and said side portion having a light reflecting surface.

7. The ring illumination apparatus of claim 1 wherein said plurality of light emitting elements are light emitting diodes (LEDs).

8. The ring illumination apparatus of claim 7 wherein each of said plurality of LEDs generates a light beam which spreads in a range of about 20°

to 40°

.

9. The ring illumination apparatus of claim 7 wherein each of said plurality of LEDs emits light beams having a far red spectral wavelength.

10. The ring illumination apparatus of claim 1 wherein said predefined angle of said light emitting elements is about 4°

.

11. The ring illumination apparatus of claim 1 wherein said predefined diameter of said substantially ring-shaped light source is in a range of about 21/2 to 3 times a dimension of said field of view at said article to be inspected.

12. A ring illumination apparatus, for illuminating a plurality of reflective elements disposed on a generally planar surface of an article to be inspected and disposed within in a field of view of an illumination detection device, said ring illumination apparatus comprising:

a substantially ring-shaped light source having a predefined diameter, said substantially ring-shaped light source generating a plurality of light beams, said substantially ring-shaped light source including;

a plurality of light emitting elements, mounted at a predefined angle with respect to a plane parallel to said generally planar surface of said article, for directing said plurality of light beams generated by said substantially ring-shaped light source toward said article in said field of view, wherein said predefined diameter and said predefined angle are defined such that a central light beam area of each of said plurality of light beams is directed across said field of view toward an opposite edge of said field of view on said article to be inspected such that said plurality of light beams provide a substantially even illumination of each of said plurality of reflective elements in said field of view on said article to be inspected without being reflected from said generally planar surface to said illumination detection device.

13. The ring illumination apparatus of claim 12 wherein said predefined angle is about 4°

.

14. The ring illumination apparatus of claim 13 wherein said predefined diameter is about 21/2 to 3 times a dimension of said field of view on said article to be inspected.

15. The ring illumination apparatus of claim 12 further including a light reflecting surface disposed generally behind each of said plurality of light emitting elements, for reflecting at least some of said light beams generated by said light emitting elements.

16. The ring illumination apparatus of claim 15 further including a light diffusing surface disposed generally in front of each of said plurality of light emitting elements, for diffusing at least some of said plurality of light beams as said plurality of light beams are directed towards said article within said field of view.

17. The ring illumination apparatus of claim 16 wherein said light reflecting surface includes a white surface proximate said light emitting elements.

18. The ring illumination apparatus of claim 12 wherein said plurality of light emitting elements are light emitting diodes (LEDs).

19. The ring illumination apparatus of claim 18 wherein each of said plurality of LEDs generates a light beam which spreads in a range of about 20°

to 40°

.

20. The ring illumination apparatus of claim 19 wherein each of said plurality of LEDs emits light beams having a far red spectral wavelength.

21. A ring illumination apparatus, for illuminating at least one reflective element disposed on a generally planar surface of an article to be inspected and disposed within a field of view of an illumination detection device, said ring illumination apparatus comprising:

a substantially ring shaped light source including a plurality of light emitting diodes (LEDs), for generating a plurality of light beams each having a beam spread in a range of about 20°

to 40° and

having a far red spectral wavelength, wherein each of said plurality of LEDs are mounted at a predefined angle of about 4°

with respect to a plane parallel to said generally planar surface of said article and forming a ring having a predefined diameter of about 2.5 to 3 times a dimension of said field of view on said article to be inspected;

a light reflecting surface disposed generally behind each of said plurality of LEDs, for reflecting at least some of said light beams generated by said LEDs; and

a light diffusing surface disposed generally in front of each of said plurality of LEDs, for diffusing at least some of said plurality of light beams as said plurality of light beams are directed towards said article within said field of view.

22. A method of illuminating an article having a plurality of reflective elements disposed on a generally planar surface, said method comprising the steps of:

placing said article with said plurality of reflective elements within a field of view of an illumination detection device and beneath a ring illumination apparatus; and

directing a plurality of light beams at said article using said ring illumination apparatus such that a central light beam area of each of said plurality of light beams is directed across said field of view toward an opposite edge of said field of view on said article to be inspected, wherein said plurality of light beams are directed toward said article being inspected at an angle of illumination with respect to said article being inspected such that said light is reflected from each of said plurality of reflective elements toward said illumination detection device and said light is reflected from said generally planar surface away from said illumination detection device.

23. The method of claim 22 wherein said article includes a substrate having said generally planar surface and a plurality of rounded reflective elements disposed thereon.

24. The method of claim 22 wherein said angle of illumination is about 4°

.

25. The method of claim 24 wherein a diameter of said ring illumination apparatus is about 2.5 to 3 times a dimension of said field of view on said article to be inspected.

26. The method of claim 22 wherein each of said plurality of light beams have a beam spread of 20°

to 40°

.

27. The method of claim 22 wherein each of said plurality of light beams have a far red spectral wavelength.