Arc illumination apparatus and method

• US 6,118,524 A
• Filed: 04/07/1999
• Issued: 09/12/2000
• 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, Ludlow, Jonathan Edmund
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): MERLINO, AMANDA H
• Application Number:
  US09/287,466
• Time in Patent Office: 524 Days
• Field of Search: 356/237.1-237.6, 356/375, 250/559.05, 250/559.07, 250/559.08, 250/559.34, 250/559.4, 250/559.44, 250/559.46, 382/145-151, 348/87, 348/126, 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 13/0813 Controlling of single components prior to mounting, e.g. orientation, component geometry H05K13/0812 takes precedence

Abstract

An illumination apparatus and method illuminates one or more reflective elements, such as solder balls on an electronic component or other protruding surfaces or objects. The illumination apparatus includes one or more arc shaped or arc shape arranged light sources 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 points on each reflected image element representing an illuminated reflective element. The points on the reflected image elements are used to located the pattern of the reflected image elements and/or to fit an outline around each image element corresponding to a known percentage of the true dimensions of each solder ball or other reflective 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. An 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 illumination apparatus comprising:

at least one arc shaped light source, for generating a plurality of light beams, said at least one arc shaped light source defining at least one open region, for allowing said article to pass into said field of view within an illumination area of said at least one arc shaped light source;

means for directing said plurality of light beams generated by said at least one arc shaped light source 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, wherein said light beams directed in said range of angles of illumination provide a substantially even illumination of said plurality of reflective elements on said article to be inspected across said field of view such that 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 illumination apparatus of claim 1 wherein said at least one arc shaped light source includes first and second arc shaped light sources defining first and second open regions, for allowing said article to pass into said field of view within said illumination area between said first and second arc-shaped light sources.

3. The illumination apparatus of claim 1 wherein said at least one arc shaped light source includes a plurality of light emitting elements, and wherein said means for directing said plurality of light beams in said range of angles of illumination includes said plurality of light emitting elements 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 directed across said field of view toward an opposite edge of said article.

4. The illumination apparatus of claim 3 further including a light reflecting surface proximate to said plurality of light emitting elements, for reflecting at least some of said light beams generated by said light emitting elements.

5. The illumination apparatus of claim 4 further including a light diffusing surface proximate to said plurality of light emitting elements.

6. The illumination apparatus of claim 3 wherein a predefined diameter of said at least one of arc shaped light source is in a range of about 2 1/2 to 3 times a dimension of said field of view on said article to be inspected.

7. The illumination apparatus of claim 3 wherein said plurality of light emitting elements are light emitting diodes (LEDs).

8. The 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 illumination apparatus of claim 8 wherein each of said plurality of LEDs emits light beams having a far red spectral wavelength.

10. The illumination apparatus of claim 1 wherein said means for directing said plurality of light beams in said range of angles of illumination includes a high transmissivity, high diffusion diffuser, disposed proximate to said at least one arc shaped light source, for angularly scattering said plurality of light beams generated by said at least one arc shaped light source.

11. The illumination apparatus of claim 10 wherein said at least one arc shaped light source includes a plurality of light emitting elements, and wherein a centerline of each of said light emitting elements is substantially parallel to said generally planar surface of said article to be inspected.

12. The illumination apparatus of claim 11 wherein said high transmissivity, high diffusion diffuser includes a diffusing film having a diffuse transmission of at least 85%.

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

14. The illumination apparatus of claim 1 wherein said at least one arc shaped light source includes a plurality of generally straight light sources arranged generally in the shape of first and second arcs, said first and second arcs defining first and second open regions, for allowing said article to pass into said field of view within said illumination area between said first and second arc-shaped light sources.

15. A 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 illumination apparatus comprising:

at least one arc shaped light source, for generating a plurality of light beams; and

a high transmissivity, high diffusion diffuser, disposed proximate to said at least one arc shaped light source, for angularly scattering said plurality of light beams generated by said at least one arc shaped light source, and for directing said plurality of light beams generated by said at least one arc shaped light source 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, wherein said light beams directed in said range of angles of illumination provide a substantially even illumination of said plurality of reflective elements on said article to be inspected across said field of view such that 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.

16. An inspection system for inspecting a plurality of reflective elements disposed on a generally planar surface of an article to be inspected, said inspection system comprising:

an illumination apparatus defining an aperture, said illumination apparatus including at least one arc shaped light source, for generating a plurality of light beams, wherein said plurality of light beams provide a substantially even illumination of said plurality of reflective elements on said article to be inspected and are reflected from each of said plurality of reflective elements as at least one arc shaped reflected image element, said at least one arc shaped light source defining at least one open region, for allowing said article to pass into an illumination area within said aperture of said illumination apparatus;

an article support surface, disposed beneath said illumination apparatus, for supporting said article such that said plurality of reflective elements on said article are in said illumination area within said aperture of said illumination apparatus; and

an illumination detection device disposed proximate to said aperture of said illumination apparatus and having a field of view, said illumination detection device detecting light beams reflected from each illuminated reflective element in said field of view, and forming said arc shaped reflected image elements corresponding to each of said plurality of reflective elements, such that light beams reflecting off said each illuminated reflective element toward said illumination detection device are detected by said illumination detection device and light beams striking said generally planar surface of said article to be inspected are not detected by said illumination detection device.

17. The inspection system of claim 16 wherein said at least one arc shaped light source includes first and second arc shaped light sources defining first and second open regions between said first and second arc shaped light sources.

18. The inspection system of claim 17 wherein said article support surface sequentially moves a plurality of said articles through said first and second open regions between said first and second arc shaped light sources.

19. A 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 illumination apparatus comprising:

at least one arc shaped light source including a plurality of light emitting elements arranged to form an arc, for generating a plurality of light beams, each of said plurality of light emitting elements being mounted at a predefined angle with respect to said generally planar surface of said article such that said plurality of light beams are directed in a range of angles of illumination;

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 said 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.

20. The illumination apparatus of claim 19 wherein said light reflecting surface includes a white surface proximate to said light emitting elements.

21. The illumination apparatus of claim 19 wherein said plurality of light emitting elements are light emitting diodes (LEDs).

22. The illumination apparatus of claim 21 wherein each of said plurality of LEDs generates a light beam which spreads in a range of about 20°

to 40 .

23. The illumination apparatus of claim 21 wherein each of said plurality of LEDs emits light beams having a far red spectral wavelength.

24. The illumination apparatus of claim 19 wherein said predefined angle of said light emitting elements is about 4°

.

25. The illumination apparatus of claim 19 wherein a diameter of said at least one arc shaped light source is in a range of about 2 1/2 to 3 times a dimension of said field of view on said article to be inspected.

26. The illumination apparatus of claim 19 wherein said plurality of reflective elements include an array of solder balls disposed on an electronic component.

27. The illumination apparatus of claim 19 wherein 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.

28. A 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 illumination apparatus comprising:

at least one arc shaped light source having a predefined diameter, said at least one arc 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 generating and directing a plurality of light beams 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.

29. The illumination apparatus of claim 28 wherein said predefined angle is about 40°

.

30. The illumination apparatus of claim 29 wherein said predefined diameter is about 2 1/2 to 3 times a dimension of said field of view on said article to be inspected.

31. The illumination apparatus of claim 28 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.

32. The illumination apparatus of claim 31 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.

33. The illumination apparatus of claim 28 wherein said plurality of light emitting elements are light emitting diodes (LEDs).

34. The illumination apparatus of claim 33 wherein each of said plurality of LEDs generates a light beam which spreads in a range of about 20°

to 40°

.

35. The illumination apparatus of claim 34 wherein each of said plurality of LEDs emits light beams having a far red spectral wavelength.