Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
1998-08-14
2001-05-29
Boudreau, Leo (Department: 2621)
Image analysis
Applications
Manufacturing or product inspection
C382S203000, C382S289000, C382S151000
Reexamination Certificate
active
06240202
ABSTRACT:
DESCRIPTION
RELATED APPLICATION
This application claims priority pursuant to 35 U.S.C. §371 from PCT/JP97/00540, with an International Filing Date of Feb. 26, 1997 and a priority date of Feb. 27, 1996, from Japanese Application No. 8-39764.
1. Technical Field
The present invention relates to an external appearance inspection method for electronic components for detecting unevenness in the outline of electronic components.
2. Background Art
Inspection of electronic components such as capacitors and the like includes inspection for detecting unevenness of various types in external surfaces, especially unevenness known as bumps, flash, or the like (hereafter, simply called “bumps” in the present description). Bumps can occur in any position, but by using a plurality of cameras, or by taking images in a plurality of directions using a single camera, all bumps can be detected as unevenness in the outline of the component. In particular, it is possible to detect unevenness in the component outline by positioning a camera such that its optical axis lies in a direction wherein a portion having a high incidence of bumps can be detected as an outline.
A conventional external appearance inspection method for detecting bumps in electronic components as unevenness in the component outline is now described with reference to FIG.
8
-FIG.
10
.
FIG. 8
shows an image of a capacitor which is the subject of inspection. The reference numeral
1
denotes the outline of the capacitor,
2
indicates a bump region, and &thgr; is the angle of the bump.
FIG. 9
shows the construction of an external appearance inspection apparatus. The reference numeral
3
is a video camera, and
4
is a data processing unit, which comprises an A/D converter
5
for analogue image signals transmitted from the video camera
3
, an image memory
6
for digital image signals, a general-purpose memory
7
, and a CPU
8
(data processing unit). The general-purpose memory
7
stores outlines, outline differential values, outline angles, and the like, extracted from the image signal.
Next, the data processing implemented by the CPU
8
in order to inspect bumps is described with reference to FIG.
10
. An image of a capacitor, which is the component under inspection, is previously taken by the video camera
3
, and this image signal is A/D converted and stored in the image memory
6
. Thereupon, the image is scanned successively in one direction and the points at which the density change is greatest are extracted as outline points (step #
11
). The series of edge points are then corrected into a function to obtain an outline (step #
12
). Thereupon, the gradient of the function of the edge point series is determined. Here, if there is a bump, the gradient will increase (gradient with respect to horizontal axis; angle &thgr;), so a uniform gradient is previously determined as a reference value, and if there is an absolute value greater than this reference value, it is determined that there is a bump (step #
13
). Bumps are detected on the lower edge, right-hand edge and left-hand edge by means of the same approach. In the case of the right-hand and left-hand edges, a gradient angle with respect to the vertical axis is used.
However, in the conventional method described above, if the capacitor is in an inclined position, there is a risk that the gradient will rise and a bump will be detected even in regions where there is no bump, thereby yielding inaccurate inspection results and leading to poor reliability.
In view of the aforementioned problems of the prior art, it is an object of the present invention to provide a highly reliable external appearance inspection method for electronic components, whereby the presence of unevenness in a component outline can always be detected accurately.
DISCLOSURE OF INVENTION
The external appearance inspection method according to the present invention comprises the steps of: extracting an approximately square-shaped outline of an electronic component under inspection; differentiating the outline; extracting a median from series of differential values; detecting maximum and minimum values in the differential values; and determining unevenness in the outline according to an absolute value of the difference between the maximum and minimum values of the differential values and the median thereof; and it enables unevenness in the outline to be detected in a stable manner, without detrimental effects due to inclination of the object under inspection.
REFERENCES:
patent: 4695884 (1987-09-01), Anastassiou et al.
patent: 4974261 (1990-11-01), Nakahara et al.
patent: 5185812 (1993-02-01), Yamashita et al.
patent: 5434802 (1995-07-01), Matsumoto
patent: 5627912 (1997-05-01), Matsumoto
patent: 412209 (1992-01-01), None
patent: 450713 (1992-02-01), None
patent: 5166904 (1993-07-01), None
Nakamura Masatoshi
Yokoyama Haruhiko
Boudreau Leo
Matsushita Electric - Industrial Co., Ltd.
Price and Gess
Werner Brian P.
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