JPS62154075A - Irregularity detector - Google Patents

Abstract

PURPOSE:To improve contrast in an image picking up by opposing a hologram to a light source and providing it without opposing to an abutting surface of a sample. CONSTITUTION:A light conducting plate of a fingerprint sensor 21 has an optical bonding layer 26 padded in a space between glass plates 24, 25 of optical glasses and a glass plate 24, and glass plate 25. The hologram 22 is opposed to the light source and is not opposed to an abutting area of fingers 7. An image pickup device is disposed at a lower part of the finger abutting area 27, the light source is lighted, when the fingers abut in the area 27, a pattern consisting of a bright part corresponding to a protruding part 7b of the fingerprint and a dark part corresponding to a recessed part 7a of the fingerprint is detected by the image pickup device, reflected light 8a is reflected on the lower surface of the glass plate 25, thereafter diffracted by the hologram 22, light 8c transmitted upward of the glass plate 24 is transmitted upward of the hologram 22, so that the fingerprint of the fingers to be detected is not illuminated.

Description

[Detailed Description of the Invention] [Summary] This is a detector that transmits pattern information based on unevenness such as fingerprints, and obtains clear information by preventing the hologram that produces total internal reflection light from facing the non-test sample. This is how it was done.

[Industrial application field]

The present invention relates to an unevenness detector, particularly to improving the performance of a fingerprint sensor used in a personal verification system for detecting fingerprints.

BACKGROUND OF THE INVENTION As the information society progresses, various technologies related to maintaining the confidentiality of information processing systems are being developed. For example, when controlling access to a computer room, conventional I
In place of the D-card, personal verification systems are beginning to be introduced in which each individual's fingerprints are registered in advance and verified upon entering the room, but since they are targeted at particularly important equipment, further improvements in performance are desired. Personal identification systems that detect fingerprints are now attracting attention as an extremely powerful method.

[Conventional technology]

Figure 3 is a diagram showing the main configuration of a personal verification device, Figure 4 is a principle diagram of a conventional fingerprint sensor using a prism,
FIG. 5 is a principle diagram of a conventional fingerprint sensor using a total internal reflection hologram.

In Figure 3, the conventional personal verification device that detects fingerprints as personal information is 0, and the fingerprint detector (unevenness detector) is 1.
, a dictionary 2 for checking detected information, and a checking circuit 3 for checking detected information, and the dictionary 2 for checking information such as cards, etc.
Fingerprints registered in advance via the fingerprint detector 1 are stored.

In the personal verification device configured as described above, when a fingerprint is input from the fingerprint detector l, the input fingerprint is compared and verified by the information verification circuit 3 with a registered fingerprint, and it is determined that the verification person is the registered person. It is determined whether or not.

In FIG. 4, a fingerprint sensor 4 corresponding to the fingerprint sensor 1
is a prism made of optical glass, and one slope 4a
A light source 5 faces the other slope 4b, and an imaging device (camera) 6 faces the other slope 4b. Therefore, when the finger 7 touches the flat surface 4c, the illumination light 8 perpendicular to the slope 4a illuminates the finger 7 which is in contact with the flat surface 4c, but the illumination light 8 irradiated to the part opposite to the recess 7a due to the fingerprint illuminates the lower surface. On the other hand, the illumination light 8 irradiated onto the part where the fingerprint protrusion 7b comes in contact is diffusely reflected at the interface, and a portion 9 of it is input into the imaging device 6.

As a result, the fingerprint pattern of the finger 7 can be detected by the imaging device 6.

In FIG. 5, in which the same reference numerals are used for parts common to those in FIG. 4, a fingerprint sensor 11 corresponding to the fingerprint sensor 1 consists of an optical glass plate 12 and a hologram 13 attached to its lower surface, forming a diffraction grating. The hologram 13 attached to the lower surface of the glass plate 12 diffracts the illumination light 8 that is incident almost perpendicularly from below to produce total reflected light.
Propagate within 2.

When the finger 7 touches the top surface of the glass plate 12, the illumination light 8 irradiated to the area facing the recess 7a formed by the fingerprint is totally reflected and propagates within the glass plate 12, while the projection 7b formed by the fingerprint comes into contact with it. The illumination light 8 irradiated onto the portion is diffusely reflected at the interface, and a portion 9 of the illumination light 8 is transmitted below the fingerprint sensor 11 and input into the imaging device 6 .

As a result, the fingerprint of the finger 7 can be detected by the imaging device 6.

[Problem that the invention seeks to solve]

However, since the fingerprint sensor 4 uses a prism, it has a disadvantage that it is thick, and the imaged pattern is distorted due to the effect of the shape of the prism.

Therefore, a fingerprint sensor 11 has been developed that eliminates this drawback, but the fingerprint sensor 11 has a drawback in that the contrast of imaging is not good.

FIG. 6 is a side view for explaining that the contrast of the fingerprint sensor 11 is not good.

In FIG. 6, the fingerprint sensor 11 is constructed by sandwiching a hologram 13 between optical glass plates 12 and 14.
Illumination light 8 that enters almost perpendicularly from the bottom surface of fingerprint sensor 4 is diffracted by hologram 13 and propagated within fingerprint sensor 11 .

However, the reflected light totally reflected on the top surface of the glass plate 12 is
When the reflected light 8a is totally reflected by the lower surface of the glass plate 14 and 8b is the reflected light 8b, the reflected light 8a passes through the diffraction grating of the hologram 13; The light beam 8b is diffracted by the diffraction grating and emitted from the upper surface of the glass plate 12 almost perpendicularly, and its propagation is terminated.

That is, a part of the illumination light 8 does not propagate within the fingerprint sensor 11 and is emitted outside the fingerprint sensor 11 at the same angle as the illumination light 8 and does not contribute to illumination of the finger. When the surface 7a is irradiated and scattered, a part of the scattered light enters the fingerprint sensor 11 again and enters the imaging device 6, resulting in a problem in that the contrast of imaging is reduced.

Means for Solving Problem C] FIG. 1 is a diagram showing the principle of the unevenness detector according to the present invention. In Figure 1, where the same reference numerals are used for parts common to the previous figure, 2
1 is an unevenness detector (fingerprint sensor), 22 is a hologram, 2
3 is a light guide plate.

The above problem, according to FIG. 1, includes a hologram 22 that takes in illumination light 8 from a light source and produces totally reflected light, and a light guide plate 23 through which the totally reflected light propagates. The sample 7 in contact with the surface of the light guide plate 23 is irradiated.
The unevenness detector (fingerprint sensor) is characterized in that the hologram 22 is provided facing at least the light source and not facing the contact surface of the sample 7. ) is resolved by

[Effect]

According to the above means, even if the light guide comes into contact with a sample, the sample will not be illuminated by the light transmitted through the upper surface of the light guide plate. Therefore, in the concavo-convex pattern of the sample photographed by the imaging device, the contrast between the bright parts corresponding to the convex parts of the sample and the dark parts corresponding to the concave parts of the sample becomes clearer than that of the conventional pattern.

〔Example〕

EMBODIMENT OF THE INVENTION Below, the unevenness|corrugation detector (fingerprint sensor) which becomes an Example of this invention is demonstrated using drawing.

FIG. 2 is a side view of a fingerprint sensor according to an embodiment of the present invention.

In FIG. 2, in which the same reference numerals are used for parts common to those in FIG. An optical adhesive layer 26 fills the area. A hologram 22 formed with a diffraction grating that takes in the illumination light 8 from the light source below and produces total reflection transmission light faces the light source and does not face the contact area 27 of the finger 7. .

The fingerprint sensor 21 configured in this way has a finger contact area 2.
When an imaging device (camera) is placed below 7 and a light source is turned on, and a finger is brought into contact with the region 27, a pattern of convexes and convexes formed by the fingerprint of the finger, that is, brightness corresponding to the convex portions (7b) of the fingerprint, is displayed. The imaging device detects a pattern consisting of the dark area and the dark area corresponding to the recess (7a) of the fingerprint. The reflected light 8a is reflected on the lower surface of the glass plate 25, is diffracted by the hologram 22, and is transmitted above the glass + JliE 24.The light 8c is transmitted above the hologram 22, and thus illuminates the fingerprint of the subject's finger. There is no.

The fingerprint sensor 21 is manufactured by coating a hologram material on the top surface of a glass plate 25 to create a hologram 22 with a diffraction grating formed in a predetermined portion thereof, and then removing unnecessary hologram material to reduce the thickness of the hologram 22. The glass plate 24 is manufactured by bonding the glass plate 24 onto the glass plate 25 via an adhesive layer 26 that fills a gap corresponding to a gap of about 3 μm (for example, about 3 μm).

Further, in the embodiment described above, the present invention is applied to a fingerprint sensor, and the hologram 22 is formed in the middle part of the fingerprint sensor 21 in the thickness direction. However, the present invention is not limited to such a fingerprint sensor 21, but is applicable to a detector that detects pattern information of various types of unevenness, and the hologram 22 can be formed and configured at other positions (for example, on the lower surface of the glass plate 25). Add a note.

〔Effect of the invention〕

As explained above, according to the present invention, in a concavo-convex detector that uses a hologram to generate total reflection light, the clarity of the imaged pattern is improved and the performance is improved without sacrificing the thinness of the detector. , the effect of improving the utilization efficiency of illumination light and making it possible to use low-output light sources (for example, LEDs) is remarkable.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of an unevenness detector according to the present invention, FIG. 2 is a side view of a fingerprint sensor according to an embodiment of the present invention, FIG. 3 is a block diagram showing the main configuration of a personal verification device, and FIG. The figure shows the principle of a conventional fingerprint sensor that uses a prism. Figure 5 shows the principle of a conventional fingerprint sensor that uses a total internal reflection hologram. Figure 6 explains the problems of the fingerprint sensor shown in Figure 5. A side view of . In the figure, 1.4.11.21 is the unevenness detection 3 (fingerprint sensor), 5 is the light source, 6 is the imager (camera), 7 is the finger (sample), 8 is the illumination light, 8a and 8b are the illumination lights. Totally reflected light, 13 and 22 are holograms, 12.14, 23, 24.25 are glass plates (light guide plates),
26 represents an optical adhesive layer. Akira Tsumefuji 1c r; Ru uneven detector F principle diagram 1 Figure 21''
figure

Claims (1)

[Scope of Claims] A hologram (22) that takes in illumination light (8) from a light source and produces totally reflected light, and a light guide plate (23) through which the totally reflected light propagates, and the totally reflected light that propagates. is the light guide plate (2
3) is irradiated to the sample (7) in contact with the surface of the sample (7).
In the unevenness detector that transmits pattern information based on the unevenness of the hologram (22), the hologram (22) is provided facing at least the light source and not facing the contact surface of the sample (7). Unevenness detector.