Method and apparatus for searching for fiducial marks, and method of detecting positions of the fiducial marks

• US 7,181,089 B2
• Filed: 09/06/2002
• Issued: 02/20/2007
• Est. Priority Date: 09/14/2001
• Status: Active Grant

• Current Assignee: Fuji Company Limited
• Original Assignee: Fuji Machine Manufacturing Company Limited
• Inventors: Chi, Baksa, Esaki, Hirotake
• Primary Examiner(s): Alavi; Amir
• Application Number:
  US10/235,932
• Publication Number:
  US 20030053714A1
• Time in Patent Office: 1,628 Days
• Field of Search: 382/287, 382/288, 382/291, 382/145, 382/151
• US Class Current: 382/287
• CPC Class Codes: G06V 10/44 Local feature extraction by analysis of parts of the pattern, e.g. by detecting edges, contours, loops, corners, strokes or intersections; Connectivity analysis, e.g. of connected components
• CPC Class Codes: H05K 1/0269 for visual or optical inspection

Abstract

Method and apparatus for searching for a fiducial mark, by processing image data indicative of images of the fiducial mark and an area surrounding the fiducial mark, which images are taken by an imaging device, wherein the image data are processed by an image-data processing device, which includes: a reference-line data storing portion operable perform a step of storing at least one reference line each of which corresponds to at least one portion of a profile of the fiducial mark and the number of which is sufficient to specify the fiducial mark; a profile-data obtaining portion operable to perform a step of obtaining profile data indicative of profiles of the images taken by the imaging device, each of the profiles of the images consisting of a group of points at which an optical characteristic of the corresponding image abruptly changes; and a searching portion operable to perform a step of searching for the fiducial mark, on the basis of the profiles represented by the obtained profile data and the stored at least one reference line.

Claims

1. A method of searching for a fiducial mark, by processing image data indicative of images of said fiducial mark and an area surrounding said fiducial mark, said images being taken by an imaging device, said method comprising:

a reference-line setting step of setting, by a person practicing the method, at least one two-dimensional reference line each of which corresponds to at least one portion of a profile of said fiducial mark and the number of which is sufficient to specify said fiducial mark, said reference-line setting step comprising selecting said at least one two-dimensional reference line from among a plurality of stored and predetermined two-dimensional candidate reference lines;

a profile-data obtaining step of obtaining profile data indicative of profiles of said images taken by said imaging device, each of said profiles of said images consisting of a group of points at which an optical characteristic of the corresponding image abruptly changes; and

a searching step of searching for said fiducial mark, on the basis of said profiles represented by the obtained profile data and said at least one two-dimensional reference line.

2. The method according to claim 1, wherein said reference-line setting step comprises setting a plurality of two-dimensional reference lines corresponding to respective portions of said profile of said fiducial mark.

3. The method according to claim 2, wherein said reference-line setting step comprises specifying positions of said plurality of two-dimensional reference lines relative to each other.

4. The method according to claim 1, wherein said plurality of stored and predetermined two-dimensional candidate reference lines are selected from a group consisting of:

a circle;

a circular arc;

a polygon;

a segment; and

a bent line.

5. The method according to claim 1, wherein said reference-line setting step comprises specifying at least one dimension of each of said at least one two-dimensional reference line.

6. The method according to claim 1, wherein said searching step comprises determining one of said profiles represented by said profile data obtained in said profile-data obtaining step, to be a profile of said fiducial mark, if more than a predetermined percentage of said one profile matches said at least one two-dimensional reference line.

7. The method according to claim 1, wherein said fiducial mark is provided on a circuit substrate.

8. A method of detecting a fiducial mark, comprising:

a fiducial-mark searching method according to claim 1; and

a fiducial-mark-position obtaining step of obtaining a position of said fiducial mark which has been searched for by said fiducial-mark searching method.

9. A method of searching for a fiducial mark, by processing image data indicative of images of said fiducial mark and an area surrounding said fiducial mark, said images being taken by an imaging device, said method comprising:

a reference-line setting step of setting, by a person practicing the method, at least one reference line each of which corresponds to at least one portion of a profile of said fiducial mark and the number of which is sufficient to specify said fiducial mark, said reference-line setting step comprising selecting said at least one reference line from among a plurality of stored and predetermined candidate reference lines;

a profile-data obtaining step of obtaining profile data indicative of profiles of said images taken by said imaging device, each of said profiles of said images consisting of a group of points at which an optical characteristic of the corresponding image abruptly changes; and

a searching step of searching for said fiducial mark, on the basis of said profiles represented by the obtained profile data and said at least one reference line, wherein said searching step comprises searching for said fiducial mark, on the basis of said profiles represented by said profile data obtained in said profile-data obtaining step, and said at least one reference line as displaced so as to effect at least one of predetermined permissible ratios of enlargement and contraction of a profile defined by said at least one reference line before displacement thereof.

10. An apparatus for searching for a fiducial mark, comprising an imaging device operable to take images of said fiducial mark and an area surrounding said fiducial mark, and an image-data processing device operable to process image data indicative of said images, said image-data processing device comprising:

a candidate-reference-line data storing portion operable to store a plurality of predetermined two-dimensional candidate reference lines which are used to search for said fiducial mark and from which at least one two-dimensional reference line the number of which is sufficient to specify said fiducial mark is selected, each of said at least one two-dimensional reference line corresponding to at least one portion of a profile of said fiducial mark and the number of which is sufficient to specify said fiducial mark;

a reference-line-data selecting portion operable by an operator of the apparatus to select said at least one two-dimensional reference line from said plurality of predetermined two-dimensional candidate reference lines;

a profile-data obtaining portion operable to obtain profile data indicative of profiles of said images taken by said imaging device, each of said profiles of said images consisting of a group of points at which an optical characteristic of the corresponding image abruptly changes; and

a searching portion operable to search for said fiducial mark, on the basis of said profiles represented by said profile data obtained by said profile-data obtaining portion and said at least one two-dimensional reference line stored in said reference-data storing portion.

11. A method of searching for a fiducial mark, by processing image data indicative of images of said fiducial mark and an area surrounding said fiducial mark, said images being taken by an imaging device, said method comprising:

a reference-line setting step of setting at least one reference line each of which corresponds to at least one portion of a profile of said fiducial mark and the number of which is sufficient to specify said fiducial mark;

a profile-data obtaining step of obtaining profile data indicative of profiles of said images taken by said imaging device, each of said profiles of said images consisting of a group of points at which an optical characteristic of the corresponding image abruptly changes; and

a searching step of searching for said fiducial mark, on the basis of said profiles represented by the obtained profile data and said at least one reference line,

and wherein said searching step comprises searching for said fiducial mark, on the basis of said profiles represented by said profile data obtained in said profile data obtaining step, and said at least one reference line as displaced so as to effect at least one of predetermined permissible ratios of enlargement and contraction of a profile defined by said at least one reference line before displacement thereof.