Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-11-29
2003-12-02
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S227280, C250S556000, C340S005830, C356S071000, C382S127000
Reexamination Certificate
active
06657185
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an irregular pattern detector, which captures, as images, irregular patterns, such as fingerprints.
2. Description of the Prior Art
A fingerprint ID apparatus is known as one of means of identifying persons. The fingerprint ID apparatus is constituted substantially by a pattern detection part capturing an irregular pattern of a fingerprint as an image, and a processing part for processing the images captured by the pattern detection part. Improvements in irregular pattern detectors such as the fingerprint ID apparatus have resulted in improved performance of the fingerprint ID apparatus.
FIG. 1
is a partially sectioned view of constitution of a conventional irregular pattern detector disclosed in Japanese Patent Application Laid-open No. 6-83944. In this drawing, the conventional irregular pattern detector has a light guide body
102
made of transparent materials such as glass or acrylic resin. A plane
103
is touched by subjects
101
such as a finger, the finger having irregular patterns thereon. A plane
104
intersects the plane
103
at a suitable angle and receives an illuminating light L
100
therein. A plane
105
reflects a reflection light L
101
, which is reflected by the irregular patterns of the subject
101
placed on the plane
103
, and controls the reflection light L
101
approximately parallel to the plane
103
. An imaging lens
108
focuses the reflection light L
101
onto a camera device
109
. A reflection mirror
110
reflects light from the imaging lens
108
at an angle to guide the reflection light to the camera device
109
.
The plane
104
is flush with the plane
105
. Therefore, an angle &bgr; of the plane
104
or the plane
105
with respect to the plane
107
facing the plane
106
is set to 20°, for example. An interface between the subject
101
and the plane
103
is further irradiated with the reflection light L
101
from outside of the plane
104
. The reflection light L
101
reflected by the irregular patterns of the subject
101
is further reflected by the plane
105
, focused by the imaging lens
108
, and reflected by the reflection mirror
110
. Consequently, images of the irregular patterns of the subject
101
are taken by the camera device
109
such as a CCD, for example.
FIG. 2
is a partially sectioned view of a simplified optical system, which is similar to the conventional irregular pattern apparatus as shown in FIG.
1
. In
FIG. 2
, as compared with
FIG. 1
, the plane
103
corresponds to a plane
111
, the plane
105
corresponds to a mirror
112
, the imaging lens
108
corresponds to a lens
113
, and the camera device
109
corresponds to a plane
114
. A plane
115
and the plane
111
are related with respect to the mirror
112
as mirror images. The plane
115
is not perpendicular to an optical axis of the lens
113
, and accordingly variations in the distance from points A, B and C on the plane
115
to the lens
113
occur, and variations of optical magnification at points A′, B′ and C′ occur.
FIGS. 3A and 3B
are plan views of images, respectively, in the optical system as shown in FIG.
2
. In
FIG. 3A
, a rectangular image of the subject
101
placed on the plane
111
is illustrated. In
FIG. 3B
, an image formed on the plane
114
is illustrated. As illustrated in
FIG. 3A
, when the image of the subject placed on the plane
111
has a rectangular shape, the image formed on the plane
114
has a trapezoidal shape owing to the lens
113
as illustrated in FIG.
3
B.
When distance BB′ is reduced in order to scale down the irregular pattern detector, angles of line BB′ with respect to line AA′ or line BB′ are enlarged, respectively. In this case, the aforementioned deformation of the image is conspicuous.
As illustrated in
FIG. 2
, line DE crosses the optical axis of the lens
113
at a right angle, and line AC tilts toward the optical axis. Therefore, as illustrated in
FIGS. 3A and 3B
, the length in a direction of line AC is shortened as compared with the length in a direction of line DE. The ratio of a longitudinal direction to a lateral direction of the subject
101
placed on the plane
111
as a detection face is different from the ratio of a longitudinal direction to a lateral direction of the image formed on the plane
114
as a light-detecting face, and accordingly precise images are not obtained.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a compact irregular pattern detector, which obtains precise images without any deformation.
In order to achieve the object of the present invention, an irregular pattern detector comprises an irregular pattern detector, including a first optical system having a light source; a transparent light guide body having an incident face receiving incident light from the light source of the first optical system, a detection face provided to face the incident face and for placing a subject thereon, a curved surface reflecting scattering light from the detection face, an optical absorbing face provided to face the curved surface and having an opening part outputting the reflection light from the curved surface; and a second optical system for guiding the light from the opening part of the optical absorbing face of the transparent light guide body to a camera device.
Here, the transparent light guide body may be provided on the first optical system.
The scattering light may be directly reflected with the curved surface to guide through the opening part to outside.
The curved surface of the transparent light guide body may be a spherical mirror, and a spherical radius of the spherical mirror may be twice as long as distance between a central point of the spherical mirror and an intersection point intersecting the spherical radius passing the central point of the spherical mirror with a perpendicular extending from a center of the opening part to the spherical radius.
The spherical mirror may form a telecentric system at a side of the subject, and the second optical system may form a telecentric system at an imaging side.
The curved surface of the transparent light guide body may be a spherical mirror, and a spherical radius of the spherical mirror may be within the range of 1.7 to 1.9 times as long as distance between a central point of the spherical mirror and an intersection point intersecting the spherical radius passing the central point of the spherical mirror with a perpendicular extending from a center of the opening part to the spherical radius.
The second optical system may correct longitudinal and lateral magnification of the light from the opening part to guide the corrected light to the camera device.
The detection face of the transparent light guide body may be a cylindrical shaped side face.
The second optical system may bend the light from the opening part to guide the light to the camera device.
The light source of the first optical system may be a light-emitting diode array provided on a substrate, and the camera device may be provided on the substrate.
The light source of the first optical system may be a light-emitting diode array provided on a substrate, and the incident face of the transparent light guide body may be constituted by a plurality of curved surfaces.
REFERENCES:
patent: 4537484 (1985-08-01), Fowler et al.
patent: 5426296 (1995-06-01), Shikai et al.
patent: 5621516 (1997-04-01), Shinzaki et al.
patent: 5900993 (1999-05-01), Betensky
patent: 6122394 (2000-09-01), Neukermans et al.
patent: 6-83944 (1994-03-01), None
Nakajima Hajime
Shikai Masahiro
Shiratsuki Akihide
Allen Stephone B.
Mitsubishi Denki & Kabushiki Kaisha
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