Image analysis – Applications – Personnel identification
Reexamination Certificate
2000-03-23
2001-05-08
Mehta, Bhavesh (Department: 2721)
Image analysis
Applications
Personnel identification
Reexamination Certificate
active
06229907
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for identifying individuals based upon iris textures extracted from images of individuals's eyes.
2. Description of the Prior Art
Individual identification technology is known which extracts iris textures from images of eyes including pupils and irises and identifies individuals based upon the extracted irises textures. For example, U.S. Pat. No. 5,291,560 has disclosed a typical individual identification system. Such an individual identification system converts the irises textures laid in eye images into irises codes, thus carrying out individual identification by comparing such irises codes. Accordingly, the individual identification system must acquire the positions of the irises or the outlines thereof.
In general, shapes of pupils and irises of human beings are circular. Therefore, the individual identification system prepares an imaginary circle circumscribed or inscribed with respect to the pupil of an individual. Likewise, the system prepares another circle with respect to the iris of the individual. Such a preparation of circles serves to establish a polar coordinate system on the eye image of the individual, wherein information on the position of the iris is given based upon the polar coordinate system.
Herein, the circle representative of an iris of a human being is defined by a center (Xc, Yc) and a radius R that maximize a value which is given by integrating values of pixels (X, Y) in the eye image along the circumference of the circle and differentiating the result of the integration by the radius R. Establishment of a polar coordinate system using the center (Xc, Yc) and the radius R, enables the individual identification to be immune to the influence of noise. In the polar coordinate system, the iris texture is divided into a plurality of areas, wherein the areas are converted into iris codes. The individual identification is carried out by comparing the iris code of an individual with the iris codes of other individuals. Therefore, in the individual identification system, preparing a circle for a human being's iris is essential to obtain an iris code representative of the iris.
Incidentally, pupils and irises of animals, e.g., horses are elliptical, in general. Accordingly, the conventional individual identification system cannot acquire an iris texture of a horse using a circle. For example, as shown in FIG.
12
(
a
), a pupil
100
of a human being is approximately circular, and remains circular regardless of change thereof in opening. Similarly, the iris
200
is roughly circular and its shaped does not depends upon opening. These make it possible to provide optimum circles representative of the iris
200
, or the boundary between the pupil
100
and the iris
200
and the boundary between the iris
200
and the sclera
300
. In contrast, as shown in FIG.
12
(
b
), a pupil
400
of a horse is elliptical, and also the ratio of the line of apsides and the minor axis thereof depends upon change in opening. Consequently, no optimum circles representative of the pupil
400
or the iris
500
can be given. In other word, neither the boundary between the pupil
400
and the iris
500
nor the boundary between the iris
500
and the sclera
600
are obtained. This makes it impossible to carry out individual identification of a horse.
In addition, there exists an irial granule
700
along the boundary between the pupil
400
and the iris
500
, in particular along the upper part thereof, which is common to the ruminants such as cattle, goats, and sheep. Further, the shape of the irial granule
700
depends upon individuals. Accordingly, accurate detection of the pupil
400
or the iris
500
is required to be immune to the presence of the irial granule
700
.
Even shapes of human beings's eyes in eye images change according to photographic conditions, and more exactly, the shapes of human beings's pupils and irises sometimes become elliptical. Therefore, assuming that the pupil and the iris change into an elliptical shape use of circles to approximate the outlines of the pupil
100
and the iris
200
deteriorates the accuracy with which individuals can be identified.
As shown in FIGS.
13
(
a
)-(
c
), there might be several circles
900
a
~
900
c
similar to one elliptical pupil
800
. This is because the state of the outline of the pupil
800
, e.g., brightness and contrast thereof, allows such different circles
900
a
~
900
c
to arise. In FIGS.
13
(
a
)-(
c
), the pupil
800
is in contact with the circles
900
a
~
900
c
by the sides, top, and bottom thereof, respectively. In addition to these circles
900
a
~
900
c
, there appear to exist other circles. Similarly, an iris might have a plurality of circles.
As discussed above, the conventional individual identification system acquires a position, or an outline representative of an elliptical pupil and an elliptical iris by preparing respective circles which are approximate thereto. Accordingly, it is difficult to acquire an accurate outlines or an accurate positions of an elliptical pupil and an elliptical iris, which deteriorates the performance of individual identification systems.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and an apparatus which are capable of acquiring the position of an iris for each individual precisely.
According to one aspect of the present invention, there is provided, in an individual identification system which identifies individuals by comparing irises thereof, an iris detection system which detects a position of an iris laid in an eye image of an individual, the iris position detecting system comprising: an ellipse preparation circuit preparing a plurality of ellipses related to the iris by changing a plurality of parameters of the ellipses; a pixel value addition circuit adding values of pixels corresponding to the circumference of each ellipse to produce a pixel sum for each ellipse; an ellipse selection circuit selecting among the plurality of ellipses an ellipse that is representative of the outline of the iris based upon pixel sums of the plurality of ellipses; and an outline decision circuit deciding that the parameters of the selected ellipse are representative of the position of the iris.
According to another aspect of the present invention, there is provided, In an individual identification system which identifies individuals by comparing irises thereof, an iris detection system which detects a position of an iris laid in an eye image of an individual, the iris position detecting system comprising: a first closed curved-line preparation circuit preparing a first closed curved-line similar to the iris; a first similarity calculation circuit calculating a first similarity between the iris and the first closed curved-line; a first judgment circuit judging whether or not the first similarity satisfies a first given similarity; a first decision circuit that the first closed curved-line is representative of the outline of the iris upon judgment that the first similarity satisfies the first given similarity; a second closed curved-line preparation circuit preparing a second closed curved-line similar to the iris upon judgment that the first similarity does not satisfy the first given similarity; a second similarity calculation circuit calculating a second similarity between the iris and the second closed curved-line; a second judgment circuit judging whether or not the second similarity satisfies a second given similarity; a second decision circuit decides that the second closed curved-line is representative of the outline of the iris upon judgment that the second similarity satisfies the second given similarity.
REFERENCES:
patent: 4641349 (1987-02-01), Flom et al.
patent: 5291560 (1994-03-01), Daugman
patent: 6081607 (2000-06-01), Mori et al.
Kuno Yuji
Okano Kenji
Frank Robert J.
Mehta Bhavesh
OKI Electric Industry Co., Ltd.
Venable
Wood Allen
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