Ring illumination reflective elements on a generally planar surface

United States Patent

King et al.

[19]

US005828449A [ii] Patent Number: [45] Date of Patent:

5,828,449 Oct. 27, 1998

[54] RING ILLUMINATION REFLECTIVE

ELEMENTS ON A GENERALLY PLANAR
SURFACE

[75] Inventors: Steven Joseph King, Merrimack, N.H.;

Jonathan Edmund Ludlow, Lexington,
Mass.; George Schurr, Fort Thomas,
Ky.

[73] Assignee: Acuity Imaging, LLC, Nashua, N.H.

[21] Appl. No.: 898,844
[22] Filed: Jul. 25, 1997

Related U.S. Application Data

[62] Division of Ser. No. 807,397, Feb. 26, 1997.

[51] Int. CI.6 G01N 21/00; G06K 9/00;

H04N 7/18; H04N 9/47

[52] U.S. CI 356/237; 356/375; 250/559.34;

250/559.4; 250/559.56; 382/146; 348/87;

348/126; 348/131

[58] Field of Search 356/327, 375;

250/559.05, 17, 108, 134, 14, 144, 146; 582/145-151; 348/126, 187, 131

[56] References Cited

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Primary Examiner—Frank G. Font

Assistant Examiner—-Jason D. Vierra-Esienberg

Attorney, Agent, or Firm—Daniel J. Bourque Esq.; Kevin J.

Carroll Esq.

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.

27 Claims, 8 Drawing Sheets