JP2602082B2 - Fingerprint image input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a device for inputting a fingerprint image for registering a fingerprint or collating with a fingerprint that has already been registered. The purpose of the device is to realize a device in which the light guide and the imaging lens can be easily integrated with each other and the cost can be reduced. A total reflection surface for reflecting light arriving from the fingerprint image input unit toward the imaging lens in an optical path between the fingerprint image input unit and the imaging lens unit; Is arranged at the center of curvature of the curved surface of the imaging lens.

[Industrial applications]

The present invention relates to an apparatus for inputting a fingerprint image in order to register a fingerprint or collate with a fingerprint already registered.

[Conventional technology]

2. Description of the Related Art In recent years, with the spread of electronic computers throughout society, public attention has been focused on how to ensure safety (security). For example, ID cards and personal identification numbers have been used as means for personal identification when entering a computer room or using a terminal, but many questions have been raised in terms of ensuring security. On the other hand, fingerprints are considered to be the most powerful means of identity verification because they have two major characteristics: "everyone is unidentified" and "lifelong invariant". In connection with a simple personal verification system using fingerprints, Much research and development is underway.

As described above, in a system for collating a fingerprint as a method for identifying an individual, a fingerprint is usually handled as an image, and an input device for converting the fingerprint into image data is required. The fingerprint is an uneven pattern, and the detection and recognition of the uneven pattern are performed according to the principle shown in FIG. 1
Is a light guide made of a transparent flat plate. When the fingerprint portion of the fingertip 2 is pressed against the fingerprint image input section 9 of the light guide 1, the convex portion (ridge portion) of the fingerprint comes into contact with the concave portion (valley line). ) Does not touch. When light enters the light guide 1 by the light source 3 and irradiates the flat surface against which the fingerprint is pressed, the light is transmitted to the surface of the finger.
It is reflected and scattered inside. Since the scattered light from the concave portion of the finger once passes through the air and enters the light guide 1, there is no component that is totally reflected and propagated in the light guide 1. However, the reflected / scattered light from the convex portion is directly incident on the light guide 1 as a spherical wave from the finger, and a part of the light satisfies the condition of total reflection in the light guide 1, and Is repeatedly propagated through total reflection. When this total reflection component is imaged by an appropriate optical system 4 and detected by the image sensor 5, an image of a convex (ridge) pattern can be obtained.

In this device, since each optical element is separated, the size of the optical system becomes large, and there are many surfaces having different refractive indexes such as an interface between air and glass in an optical path, and the aberration is large.

FIG. 5 shows a structure in which the light guide 1 and a single spherical lens 6 are attached to the end portions in order to reduce the size and simplification of the configuration of the fingerprint image input device and reduce aberrations.

[Problems to be solved by the invention]

Since the reflected and scattered light from the convex part of the fingerprint is a spherical wave,
In order to form an image with less aberration using a single spherical lens, it is effective to dispose an aperture stop 7 at the center of curvature of the convex lens 6 as shown in FIG. It has been proposed as Japanese Patent Application No. 63-155670. Reference numeral 8 denotes a mirror that guides light coming from the fingerprint image input unit 9 to the single spherical lens 6 side.

However, in this optical system, since the aperture stop 7 is provided inside the light guide 1, the aperture stop 7,
It must be manufactured by laminating the single spherical lens 6 in this order, and it is difficult to integrally mold the light guide 1 and the single spherical lens 6, and the manufacturing cost is increased.

The technical problem of the present invention is to provide a fingerprint image input device in which the imaging lens is integrated with the light guide, in which the light guide and the imaging lens can be easily molded integrally and the cost can be reduced. Is to make it happen.

[Means for solving the problem]

FIG. 1 is a diagram for explaining the basic principle of a fingerprint image input device according to the present invention. Reference numeral 1 denotes a light guide having a fingerprint image input unit 9 and an imaging lens 10 integrally formed at an end.

In the optical path between the fingerprint image input unit 9 and the imaging lens unit 10, light coming from the fingerprint image input unit 9 is
It has a total reflection surface 11 that reflects light to the side. This total reflection surface
Numeral 11 is provided at the center of curvature of the curved surface of the imaging lens 10.

[Action]

The light reflected from the convex portion of the fingerprint in the fingerprint image input unit 9 repeats total reflection, reaches the total reflection surface 11, and forms an image on a detection surface such as the image sensor 5 by the imaging lens 10.

Since the total reflection surface 11 is disposed at the center of curvature of the curved surface of the imaging lens 10, it comes from the fingerprint image input unit 9, is totally reflected by the total reflection surface 11 toward the imaging lens 10, and is detected. Light arriving at the surface has less aberration during imaging.

The optical path between the fingerprint image input unit 9 and the imaging lens 10 is integrated by the light guide 1 and there is no space. Decrease.

A fingerprint image input unit 9 and an imaging lens 10 are provided on the outer surface of the light guide 1.
In addition, since the total reflection surface 11 is provided, all of them can be integrally molded.

〔Example〕

Next, how the fingerprint image input device according to the present invention is actually embodied will be described with reference to embodiments. FIG. 2 is a side view showing the first embodiment of the present invention. On the outer surface of the light guide 1,
It has a fingerprint image input unit 9 and an imaging lens 10, and has a total reflection surface 11 in the optical path from the fingerprint image input unit 9 to the imaging lens 10.

The total reflection surface 11 is disposed at the center of curvature of the curved surface of the imaging lens 10, and the area 12 around the total reflection surface 11 is roughened by roughening the light guide surface. Therefore, of the light arriving from the fingerprint image input unit 9, the light arriving at the rough surface unit 12 is scattered and does not enter the imaging lens 10. Therefore, only light that reaches the center of curvature of the curved surface of the imaging lens 10 is reflected by the total reflection surface 11, passes through the imaging lens 10, and forms an image on the detection surface.

FIG. 3 is a side view showing a second embodiment of the present invention. In the light guide 1 in this embodiment, the optical path is bent 90 ° at two places. The fingerprint image input unit 9, the total reflection mirror 13, the total reflection surface 11, and the imaging lens 10 are arranged in this order between the fingerprint image input unit 9 and the imaging lens 10. The part from the fingerprint image input unit 9 to the imaging lens 10 is integrally molded, and the total reflection surface 11
Is formed as a rough surface portion 12. The total reflection surface 11
Is formed by forming an opening without providing a rough surface only in the center of curvature of the curved surface of the imaging lens 10 in the rough surface portion 12.

In this device, when the fingertip 2 is pressed against the fingerprint image input unit 9, the convex portion of the fingerprint contacts the light guide 1 but the concave portion does not.

Therefore, when light is irradiated through the light guide 1 to the fingerprint image input unit 9 against which the fingertip 2 is pressed, the light is reflected and scattered on the surface and inside of the finger. Since the scattered light from the concave portion of the finger once passes through the air and enters the light guide 1, there is no component that is totally reflected in the light guide 1 and propagates. However, the reflected / scattered light from the convex portion is directly incident on the light guide 1 as a spherical wave from the finger, and a part of the light satisfies the condition of total reflection in the light guide 1, and Is repeatedly propagated through total reflection.

When the light reaches the total reflection surface 11 formed at the center of the rough surface portion 12, only light rays passing through the center of curvature of the curved surface of the convex lens 10 are totally reflected, and the remaining light is scattered due to the presence of the rough surface 12. .

In order to form the total reflection surface 11 only at the center of curvature of the imaging lens 10, in addition to roughening the surrounding area 12,
A paint or the like which is rich in light absorbency may be applied.

〔The invention's effect〕

As described above, according to the present invention, a total reflection surface 11 is provided at the center of curvature as means for guiding only light arriving at the center of curvature of the imaging lens to the imaging lens side, in order to eliminate aberrations, Further, it is disposed on the outer surface of the light guide 1. Therefore, everything from the fingerprint image input unit 9 to the imaging lens 10 can be integrally formed with the light guide 1, and as a result, the manufacturing is easy and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a view for explaining the basic principle of a fingerprint image input device according to the present invention, FIG. 2 is a side view showing a first embodiment of the present invention, and FIG. 3 is a side view showing a second embodiment of the present invention. FIG. 4 is a side view showing a conventional fingerprint image input device, and FIG. 5 is a sectional view showing a conventional integrated fingerprint image input device. In the figure, 1 is a light guide, 2 is a fingertip, 6 is a single spherical lens, 7 is an aperture stop, 9 is a fingerprint image input unit, 10 is an imaging lens, R is a radius of curvature of the imaging lens, and 11 is a whole. A reflecting surface, 12 indicates a rough surface portion, and 13 indicates a mirror surface.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroyuki Ikeda 1015 Kamikodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-1-321576 (JP, A)

Claims (1)

(57) [Claims] 1. A light guide (1) having a fingerprint image input section (9).
The imaging lens (10) is integrally formed at the end of the lens, and comes from the fingerprint image input section (9) in the optical path between the fingerprint image input section (9) and the imaging lens section (10). A total reflection surface (11) for reflecting light toward the imaging lens (10); the total reflection surface (11) is disposed at a center of curvature of a curved surface of the imaging lens (10); A fingerprint image input device.