JPH02133892A - Fingerprint image input device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a fingerprint image input device of a fingerprint collation device having a living body detection function, one common illumination light source illuminates the entire object to be examined and the light beam spot to the object to be examined. The purpose of this device is to provide a simple and lightweight fingerprint image input device that can create a fingerprint image, and a single grating lens is provided to receive the illumination light on the object to be examined. At least one of them is configured to be created using transmitted light or diffracted light from a grating lens.

[Industrial application field]

The present invention relates to a fingerprint verification device as a personal identification means, and more particularly to a fingerprint input device in a fingerprint verification device equipped with a living body detection function for determining whether a test object is a living body or a replica.

A fingerprint matching system is known as a personal identification method.

In this system, fingerprints are generally treated as images, and therefore an input device that converts fingerprints into image data is required.

[Conventional technology]

A fingerprint has a concavo-convex pattern, and the basic principle of conventional detection of concavo-convex patterns is shown in FIG.

When a finger IO is pressed against one surface 13 of the transparent flat plate (light guide plate) 11, the convex portions (ridges of a fingerprint) come into contact, but the concave portions do not.

As shown in FIG. 8A, when light TO is irradiated from below through the transparent body 11 to prevent total reflection from occurring on the flat surface 13 against which the finger 10 is pressed, the light TO is emitted from the transparent flat plate 11 and is emitted from the concave portion P. The incident light is scattered in all directions, but all of it passes through the flat plate again and disappears into the distance (ray TI). On the other hand, the light hitting the convex portion Q is scattered in all directions within the flat plate ll,
A part of it is emitted from the flat plate (ray γ2), but a part of it propagates inside the flat plate by total reflection (light ′!ar3). By imaging this total reflection component using an appropriate optical system, a pattern of convex portions (fingerprint image) can be obtained.

[Problem that the invention attempts to solve]

However, with this method, if a replica (for example, a rubber copy) is created that has exactly the same uneven pattern as the registered fingerprint, fingerprint matching can also be performed using that replica, and this cannot be ruled out. There was a problem.

Therefore, methods have been studied to detect that the uneven pattern that has come into contact with a fingerprint input device is not a replica but a living body. The applicant of the present application has already proposed a method as shown in FIG. 10 as a method for almost instantaneous living body detection. A light spot is irradiated onto the surface of the finger from light # (for example, D) 21 through a converging lens 23, an image of the light spot is obtained by the imaging system 25, and the size of the spot image is determined by the photodetector 27. ,
Alternatively, it is determined whether the object is a living body or a non-living object based on the position. When a light spot is irradiated onto a finger, the glowing part propagates not only to the light irradiated part but also to the inside (flesh) of the finger, and the peripheral part also emits light. However, in the case of a replica (for example, Si-based rubber), light is reflected and scattered only in the very vicinity of the light irradiation part. When an imaging system is configured in which the light irradiation part is an object point, the size and center position of the object point are different between a real finger (living body) and a replica (non-living finger), so the image size and position are different. Therefore, the size of the image,
Alternatively, living body detection can be performed by measuring the position. The way the light wraps around the inside when a light spot is irradiated is a phenomenon unique to human fingers, making counterfeiting extremely difficult.

That is, as shown in FIG. 8B, the plane 1 on which the finger 10 is pressed
When light γ0 is irradiated from inside the plane so that the total reflection condition is satisfied for 3, the concave portion P is not irradiated with light, and only the convex portion Q is selectively illuminated.

However, in the case of a human finger, light partially passes through it, so
As a result of the light irradiated on the convex portion Q being transmitted through the inside of the finger and wrapped around the concave portion P as shown by T4, the concave portion P also emits light. Therefore, in the case of FIG. 7B as well as in the case of FIG. 7A, riγ2
．． resulting in a γ3 configuration.

Therefore, by configuring an optical system that images only the T3 configuration, a convex pattern can be obtained.

In any of the above cases, both the concave portion P and the convex portion Q of the finger act as a light emitter. In this way, in order to obtain a fingerprint image (an uneven image), an illumination device that irradiates the finger with light is required.

Furthermore, in order to provide a living body detection function, a light source 21 (FIG. 10) for creating a beam spot is required, separate from the overall illumination light source for obtaining a fingerprint image.

The fingerprint image input system (Fig. 7) and living body detection system (Fig. 1) described above.
FIG. 9 shows a conventional example of a fingerprint sensor that combines and integrates the fingerprint sensor (FIG. 0). In this example, the illumination for fingerprint image input (example L
Since the ED) 28 and the living body detection illumination 21 are provided separately, there is a problem that the optical system has a large number of components and is complicated. It is preferable to use the two types of illumination in common, but the former requires illumination of a wide area of the finger, and the latter requires spot illumination of a part of the finger, so they are contradictory. . Therefore, it was difficult to simply share lighting.

In FIG. 9, 26 is a converging lens for creating a beam spot for living body detection, and 24 is C for reading fingerprint information.
It is OD.

The purpose of the present invention is to provide an illumination light source for a fingerprint image input system and a living body detection system.
The purpose of this invention is to simplify and reduce the weight of the fingerprint input device by using a common light source for the beam spot of the system.

[Means to solve the problem]

According to the present invention, in order to achieve the above object, a test object (
Fingerprints are detected by irradiating the entire object with light and optically identifying the scattered signal light from the uneven surface of the object, while irradiating the object with a light beam spot and irradiating the light beam spot. In a fingerprint image input device, a point image is formed by an imaging optical system and the size of the image point is used to identify whether the object to be examined is a biological body or a replica. One grating lens is provided, and the illumination light of the entire object to be measured and the light beam spot to the object to be measured are created by the transmitted light and diffracted light of the grating lens.

When the transmitted light (0th order light) of the grating lens is used as illumination light for the entire object to be measured, the diffracted light is used as a light beam spot to the object to be examined, and conversely, the transmitted light of the grating lens When the light is used as a light beam spot on the object to be inspected, the diffracted light is used as illumination light for the entire object to be inspected.

Separately, a single grating lens is provided to receive part of the illumination light to the test object, and either the illumination light to the test object or a beam spot is created by the diffracted light of the grating lens. However, the other light, that is, the beam spot or illumination light directed toward the object to be inspected may be formed by the illumination light that does not pass through the grating lens.

[Function] When the grating lens is irradiated with diffused light, the transmitted light is directly irradiated onto the finger as illumination light for the entire object to be examined (finger), and the diffracted light (preferably the first-order diffracted light) of the grating lens is irradiated onto the finger. converges to a predetermined point. In this case, the diffraction grating of the grating lens is designed so that its first-order diffracted light creates convergent light.

In addition, when the grating lens is irradiated with convergent light, the transmitted light is directly used as a beam spot (for biological examination) to a predetermined point on the object to be examined (finger).
The diffracted light (preferably the first-order diffracted light) of the grating lens is used as illumination light for the entire finger (for fingerprint detection).

In this case, the diffraction grating of the grating lens is designed so that its first-order diffracted light becomes diffused light.

In the invention in which the grating lens receives only part of the illumination light (claims 4, 5, and 6), when the incident light is diffused light, the illumination light that does not pass through the grating lens becomes the illumination light for the entire finger, On the other hand, the diffracted light (preferably the first-order diffracted light) of the grating lens becomes a beam spot for living body detection.

In addition, when the incident light is convergent light, the illumination light that does not pass through the grating lens and/or the transmitted light of the grating lens becomes a beam spot, and the diffracted light (preferably the first-order diffracted light) of the grating lens becomes the illumination light for overall irradiation. .

〔Example〕

According to the first basic concept of the present invention, a single illumination means generates a diverging wave for illuminating the finger metal body and a converging wave for spot-wise illuminating a part of the finger. , as shown in FIG. 1, a grating lens 30 is used. The grating lens 30 has a function of focusing the diverging waves from the light source (for example, a semiconductor laser LD) 31 with appropriate efficiency. Among the diverging lights that enter the grating lens 30, the O-order transmitted light L0 remains in the state of a divergent wave and illuminates the entire finger 10 widely, and the -order diffracted light becomes a convergent wave and illuminates a part of the finger as a spot. do. Thereby, only one light source 31 is required.

A specific example is shown in FIG. A semiconductor laser is used as the light source 31, a grating lens 30 is formed in a diagonally cut portion 11a of the transparent light guide plate 11, and the grating lens 30 focuses the laser beam Lt (L,), and the transmitted light L0 hits the finger metal body. to illuminate.

The means for forming a fingerprint image on the CCD 24 is achieved by extracting a component of the scattered light from the fingerprint contact area that propagates inside the light guide plate 1 due to total reflection from the obliquely cut end surface 11b and guiding it to the imaging system 22. be done.

Here again, to briefly explain the principle of living body detection, when a light spot is irradiated onto a replica such as silicone rubber,
As described above, since light scattering occurs only in the very vicinity of the spot, a spot image of a size determined by the size of the irradiated light spot and the magnification of the imaging system is formed on the photodetector 27 via the converging lens system 29. be able to. On the other hand, in the case of a living body, light penetrates into the inside of the finger, causing light scattering over a wide area. Therefore, the size of the spot formed on the photodetector 27 is larger than in the case of duplication.

Furthermore, when the light spot is irradiated obliquely to the surface of the finger, the center of the light scattering area is shifted from the center in the case of duplication.

Living body detection is possible by detecting the size and center position of a sport/spot image obtained by imaging such scattered light. As the photodetector 27, it is preferable to use a known divided detector having a plurality of light-receiving areas, or to use a plurality of small photodetectors arranged in an array.

3 and 4 show two ways of using the grating lens 30. Figure 3 uses a divergent beam,
0th order transmitted light. This figure shows the case where the finger metal body is illuminated with 1st-order diffraction light, and the finger contact surface is spot-illuminated with 1st-order diffraction light. Figure 4 shows zero-order transmitted light using a focused beam. This is a case where the finger contact surface is spot-illuminated and the finger metal body is illuminated with the first-order diffracted light L1. When using a diverging light source, such as a semiconductor laser, the light shown in FIG. 3 is preferable, but it can be easily converted into convergent light using a convergent lens system 35.

Figure 5.6 shows yet another embodiment of the invention. A grating lens 30 is formed in a part of the obliquely cut portion 11a of the light guide plate 11, and a part of the illumination light (first-order diffracted light) is used to spot illuminate the finger contact surface.

On the other hand, the finger metal body is illuminated by light that enters the light guide plate 11 from the portion where the grating lens 30 is not formed (the shaded portion).

In Fig. 6, contrary to Fig. 5, convergent incident light is used,
Diffuse illumination light is created by the first-order diffracted light, and spot light is created by the direct incident light L0 that does not pass through the grating lens 30. Note that a part of the spot light is also the zero-order light transmitted through the grating lens 30.

Although the grating lens in the above explanation was described as a means for forming a circular minute spot, it is also possible to improve the living body detection sensitivity by changing the checkered pattern of the grating lens to form a deformed spot such as an ellipse. It is possible.

Further, the grating lens may be formed directly as a light guiding element, or may be formed as a separate element and bonded.

〔Effect of the invention〕

As described above, according to the present invention, in a fingerprint image input device equipped with a living body detection function, a fingerprint image is transferred to an image sensor (COD) by using a single grating lens.
By using one light source, illumination of the entire finger contact area for formation on the finger contact surface and spot illumination on the finger contact surface for performing living body detection can be performed. That is, regarding the illumination system, it is highly effective in that a living body detection illumination system can be constructed without increasing the volume or weight of a fingerprint image input device that does not have a living body detection function.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the fingerprint input device according to the present invention, FIG. 2 is a diagram showing a specific embodiment of the device in FIG. 1, and FIG.
4 and 4 are diagrams explaining two ways of using the grating lens, and FIG. 5 is a diagram showing a different embodiment from that in FIG. 2.
6 is a diagram showing a modification of FIG. 5, FIG. 7 is a diagram showing the principle of a fingerprint input device, FIGS. 8A and 8B are diagrams showing conventional illumination light for separating unevenness information, and FIG. FIG. 9 is a diagram showing an example of a conventional fingerprint sensor with a living body detection function, and FIG. 10 is a diagram showing an example of a conventional living body detection method. 10...Finger, 30...Grating lens, 31...Light source.

Claims (1)

[Claims] 1. Fingerprints are detected by irradiating light onto the entire object to be inspected and optically identifying scattered signal light from unevenness on the surface of the object, while at the same time directing a light beam spot onto the object to be inspected. In a fingerprint image input device, an image of the irradiated point of the light beam spot is formed by an imaging optical system, and it is determined whether the object to be examined is a living body or a replica based on the size and position of the image point. , has a single grating lens (30) that receives the illumination light on the test object (10), and converts the illumination light of the entire test object and the light beam spot to the test object by the transmitted light of the grating lens ( A fingerprint image input device characterized in that it is created using a fingerprint image (L_0) and a diffracted light (L_1). 2. The light transmitted through the grating lens forms illumination light for the entire object to be examined, while the diffracted light from the grating lens forms a light beam spot to the object to be examined. Fingerprint image input device. 3. The light transmitted through the grating lens forms a light beam spot on the object to be examined, while the diffracted light from the grating lens forms illumination light for the entire object to be examined. Fingerprint image input device. 4. Fingerprints are detected by irradiating the entire object with light and optically identifying the scattered signal light from the irregularities on the surface of the object, while irradiating the object with a light beam spot and In a fingerprint image input device, an image of the irradiation point of a spot is formed by an imaging optical system, and the size and position of the image point are used to identify whether the object to be examined is a living body or a replica. It is characterized by having a single grating lens (30) that receives a part of the illumination light, and using the diffracted light of the grating lens, either the illumination light or the light beam spot to be applied to the object to be examined is created. Fingerprint image input device. 5. The fingerprint image input device according to claim 4, wherein the diffracted light of the grating lens forms illumination light for the object to be examined. 6. The fingerprint image input device according to claim 4, wherein the diffracted light of the grating lens forms a light beam spot on the object to be examined.