JP2579375B2 - Fingerprint input device - Google Patents

Description

The present invention relates to a fingerprint input device used for fingerprint collation or fingerprint identification.

[Prior Art] As a conventional apparatus for performing fingerprint input, there is an apparatus that directly captures a fingerprint image by using a prism as shown in FIG.

In FIG. 1, reference numeral 10 denotes a prism having a cross section of a right-angled isosceles triangle, and a finger 11 for inputting a fingerprint pattern is pressed against a bottom surface 10a facing the right-angled top side. Light is emitted from the light source 12 at an incident angle of 45 degrees with respect to the bottom surface 10a, and a reflection image due to the unevenness of the fingerprint of the finger 11 is captured by an imaging device 13 provided at an angle of 45 degrees with respect to the bottom surface 10a. It is configured to convert to.

FIG. 14 shows another conventional fingerprint input device that directly captures a fingerprint image using a prism.

In the figure, reference numeral 20 denotes a prism having a right-angled isosceles triangular cross section, and a finger 21 for inputting a fingerprint pattern is pressed against a bottom surface 20a facing the right-angled top side. Light is radiated from the light source 22 to the bottom surface 20a so that the incident angle is larger than the critical angle of total reflection. As a result, irregular reflection occurs at a portion where the irregularities of the fingerprint and the prism 20 are in contact with each other, and the light is captured by an imaging device 23 provided at a position closer to the bottom surface 20a on the same side as the light source 22, and is converted into an electric signal. . Further, in a portion where the irregularities of the fingerprint and the prism 20 are not in contact, the light is not totally reflected but totally reflected and exits from the surface 20b to the outside.

FIG. 15 shows another conventional fingerprint input device.

In the figure, reference numeral 30 denotes a light guide plate made of, for example, a glass plate, and a finger 31 for inputting a fingerprint pattern is pressed against a part of one surface 30a. A portion where the finger 31 is pressed is irradiated with a coherent laser beam from the laser light source 32. As a result, irregular reflection occurs at a portion where the unevenness of the fingerprint and the light guide plate 30 are in contact, and light due to the irregular reflection is generated by the light guide plate 30.
The light propagates through the inside and is applied to the hologram 33 attached at a position away from the light guide plate 30. As a result, light due to irregular reflection is extracted from the light guide plate 30 by the action of the hologram 33, is incident on the imaging device 34, and is converted into an electric signal. In a portion where the unevenness of the fingerprint and the light guide plate 30 are not in contact, the laser light is emitted to the outside of the light guide plate 30, reflected by the concave portion of the fingerprint, and again enters the light guide plate 30. However, this light 35 is again emitted to the outside from the surface 30b on the opposite side of the light guide plate 30, and does not reach the hologram 33.

[Problem to be Solved by the Invention] The conventional fingerprint input device shown in FIG. 13 has a simple structure, but the incident angle of the irradiation light with respect to the bottom surface 10a is as small as 45 degrees. There is a problem that the S / N is very low.

According to the conventional fingerprint input device of FIG. 14, light is not diffusely reflected but totally reflected at the portion where the unevenness of the fingerprint and the prism 20 are not in contact, and exits from the surface 20b. Therefore, no light enters the image pickup device 23 from this portion. Therefore, the S / N is improved by that much as compared with the apparatus shown in FIG. 13, but it is difficult to greatly improve the S / N because only a part of the diffusely reflected light enters the imaging device 23.

Furthermore, according to the conventional fingerprint input device of FIG.
Light incident on a portion where the unevenness of the fingerprint and the light guide plate 30 are not in contact is emitted from the light guide plate 30 to the outside, and does not reach the hologram 33, so that a considerably excellent S /
Although N can be obtained, there is a problem that a special laser light source and an optical device such as a hologram are required, and the manufacturing cost is considerably increased.

Therefore, an object of the present invention is to provide an inexpensive fingerprint input device having excellent S / N.

[Means for Solving the Problems] A feature of the invention of the present application that achieves the above object is that a light guide plate having a through hole for placing a finger to input a fingerprint pattern, a light source, and a light from the light source At least one of the light guide plates
Means for allowing light to enter at an incident angle at which light is totally reflected in the light guide plate from one surface, and imaging means provided at a position facing the finger through the through hole of the light guide plate, and the light guide plate is incident. Light is incident on the end face of the through-hole and irradiated to the finger, and the imaging means is configured to receive light reflected by the fingerprint pattern of the finger.

Preferably, the light guide plate has a reflective film on all surfaces except the surface on which light from the light source is incident, the end surface of the through hole, and two surfaces orthogonal to the axis of the through hole.

[Operation] In the invention of the present application, light from the light source is made to enter the light guide plate at an incident angle at which the light is totally reflected in the light guide plate. Thus, the incident light propagates in the light guide plate while repeating total reflection. A through hole is provided in the light guide plate at the position where the finger to which the fingerprint pattern is to be input is placed, and the light propagating in the light guide plate is emitted from the end face of the through hole and irradiated to the finger. As a result, light is reflected in accordance with the unevenness of the fingerprint pattern, and the reflected light is received by the imaging means provided at a position facing the finger through the through-hole, whereby the fingerprint pattern is input as an electric signal.

When the light guide plate has a reflective film on all surfaces except a surface on which light from a light source enters, an end surface of the through hole, and two surfaces orthogonal to the axis of the through hole, the light is reflected by the reflective film. Is reflected without reaching the outside and reaches the fingerprint collecting portion again, so that the amount of light applied to the imaging means is greatly increased, and at least the shading of the fingerprint pattern image can be performed, and the S / N can be greatly increased. Can be improved.

[Examples] Hereinafter, the configuration of a reference example of the present application and an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a side view schematically showing the configuration of one reference example of the present application.

In the figure, reference numeral 40 denotes a transparent light guide plate installed horizontally, which is formed of, for example, a strip-shaped glass plate. On the upper surface of one end side (right end side in the figure) of the light guide plate 40, a fingerprint sampling portion to which a finger 41 to input a fingerprint pattern is brought into contact is provided.
40a is provided.

The dimensions of the light guide plate 40 are such that the length in the light propagation direction (left-right direction in the figure) is about 100 mm and the width is about 30 to 40 mm. The length in the light propagation direction is the length of the fingerprint collection portion 40a (10 to 20 m
m) It is set to be sufficiently longer.

The lower surface (or the upper surface) of the light guide plate 40 on the opposite end side (left end side in the figure) with respect to the fingerprint collection portion 40a faces the right-angled top of the prism 42 having a right-angled triangular cross section. The bottom surface 42a is adhered. For this bonding, an adhesive having the same refractive index as that of the light guide plate 40 is used.

An imaging device 43 is provided directly below the fingerprint collecting portion 40a of the light guide plate 40.

A light source 44 is provided at a position facing the surface 42b of the prism 42, and light L1 from the light source 44 is incident on the light guide plate 40 via the prism 42. In this case, the incident angle with respect to the light guide plate 40 is set to be slightly larger than the critical angle of total reflection of the light guide plate 40 (about 41.2 degrees in the case of general glass). This depends on the shape of the prism 42, the light source 44
Can be set according to the position and irradiation direction.

The light L1 from the light source 44 is preferably a parallel light beam, but need not be a completely parallel light beam. The reason is that light having an incident angle smaller than the critical angle of total reflection of the light guide plate 40 is
This is because the light does not propagate through the light guide plate 40 which is transmitted through the upper surface or the lower surface of the light guide plate and radiated to the outside.

Light guide plate 40 at an angle larger than the critical angle of total reflection of light guide plate 40
The light L2 incident on the light guide plate 40 propagates through the light guide plate 40 while being totally reflected by the upper surface and the lower surface of the light guide plate 40, and the fingerprint collection portion 40a
To reach.

When the finger 41 is not pressed against the fingerprint collecting portion 40a on the upper surface of the light guide plate 40, the light L2 is totally reflected and emitted to the outside from the right end surface 40b of the light guide plate 40 in the drawing. Therefore,
In this case, no light is applied to the imaging device 43.

When the finger 41 is pressed against the fingerprint sampling portion 40a on the upper surface of the light guide plate 40, the light guide plate 40
Diffuse reflection occurs at the portion in contact with the upper surface of the. Therefore, light L3 having an angle smaller than the critical angle of total reflection is emitted outside from the lower surface of the light guide plate 40 and applied to the imaging device 43. The imaging device 43 condenses the light L3, forms an image, and converts it into an electric signal. As a result, an electric signal representing the fingerprint pattern can be obtained.

FIG. 2 is a side view schematically showing a configuration of another reference example of the present application.

This reference example is basically the same as the reference example of FIG. 1, except that the light from the light source 144 is used without using a prism.
The only difference from the reference example of FIG. 1 is that it is configured to directly enter from the end surface 140c of the forty.

This reference example includes a light source 144, a light guide plate 140, and an imaging device 14.
Since it can be composed of three members (3), there is an advantage that the structure is very simple.

Note that the end surface 140c of the light guide plate 140 may be configured to be perpendicular to the upper surface and the lower surface thereof, but the light from the light source 144 is vertically incident as shown in FIG. By doing so, the incident efficiency is maximized.

FIG. 3 is a side view schematically showing a configuration of still another reference example of the present invention.

This reference example is a fingerprint sampling portion 240a for contacting the finger 241.
The structure is basically the same as that of the reference example of FIG. 2 except that light is incident from the left and right of the light guide plate 240 with the center as the center.

Light sources 244 and 245 are provided on both left and right sides of the light guide plate 240, respectively. Light from these light sources 244 and 245
The light enters the light guide plate 240 via 240c and 240b, respectively.
Thus, light from both directions is applied to the fingerprint collection portion 240a.

According to this reference example, the amount of light that is irregularly reflected by the unevenness of the fingerprint pattern and applied to the imaging device 243 is doubled, and the shading of the fingerprint pattern image can be reduced. As a result, S / N can be significantly improved.

FIG. 4 is a side view schematically showing a configuration of still another reference example of the present application.

In this reference example, an end surface 340c of the light guide plate 340 on the light source 344 side and three surfaces excluding an upper surface and a lower surface, that is, two side surfaces and an end surface
340b is a mirror surface on which a metal such as aluminum is deposited. The other configuration is exactly the same as the configuration of the reference example in FIG.

According to this reference example, the light travels through the light guide plate 340 while being reliably reflected on the two side surfaces, is reflected on the end surface 340b without going outside, and is again applied to the fingerprint collection portion 340a. As a result, similarly to the reference example in FIG. 3, the amount of light that is irregularly reflected due to the unevenness of the fingerprint pattern and applied to the imaging device 343 is greatly increased, and the shading of the fingerprint pattern image can be reduced. S / N can be greatly improved. Moreover, according to this reference example, the same effect can be obtained with only one light source without providing two light sources, so that a simpler and cheaper configuration can be achieved.

As described above, according to the above-described reference example, since it can be basically configured by the light source, the light guide plate, and the imaging device,
A very small and inexpensive fingerprint input device can be provided. In addition, of the light due to the irregular reflection at the portion in contact with the irregularities of the fingerprint, all the light having a reflection angle smaller than the critical angle of total reflection is applied to the imaging device and is imaged as an image. It can be greatly improved.

FIG. 5 is a side view schematically showing a configuration of one embodiment of the present invention, and FIG. 6 is a plan view thereof.

In these figures, reference numeral 440 denotes a transparent light guide plate installed horizontally, which is formed of, for example, a rectangular glass plate. At the center position of the light guide plate 440, there is provided a through hole 447 for collecting a fingerprint in which a finger 441 to which a fingerprint pattern is to be input is placed in the opening above the finger. This through hole 4
47 has an elliptical shape having a diameter slightly smaller than the size of the finger 441, and the finger 441 is pressed down with the fingerprint face down so as to cover the opening of the through hole 447 during fingerprint collection.

The size of the light guide plate 440 depends on the light propagation direction (left-right direction in the figure)
The length is about 100 mm and the width is about 50 mm. The length in the light propagation direction is the length of the through hole 447 for collecting fingerprints (10
~ 20mm).

Immediately below the through hole 447 for collecting a fingerprint in the light guide plate 440, an imaging device 443 is provided.

Light sources 444 and 445 are provided on both left and right sides of the light guide plate 440, respectively, and light from these light sources 444 and 445 is vertically applied to the end surfaces 440c and 440b, respectively, and enters the light guide plate 440.

In this case, the angle of incidence on the light guide plate 440 is set to be slightly larger than the critical angle of total reflection of the light guide plate 440 (about 41.2 degrees in the case of general glass).

The lights L4 and L5 from the light sources 444 and 445 are preferably parallel rays, but need not be completely parallel rays. The reason is that light having an incident angle smaller than the critical angle of total reflection of the light guide plate 440 is transmitted through the upper or lower surface of the light guide plate 440 and radiated to the outside, and does not propagate in the light guide plate 440.

Light guide plate 4 at an angle larger than the critical angle of total reflection of light guide plate 440
The lights L6 and L7 incident on the light guide plate 440 propagate through the light guide plate 440 while being totally reflected by the upper and lower surfaces of the light guide plate 440, and reach the fingerprint collecting through hole 447. And its through hole 447
From the end surface 447a of the light guide plate 440, that is, into the through hole 447.

Since the finger 441 is pressed with the fingerprint side down so as to cover the through hole 447, the emitted lights L8 and L9
Is irradiated on the fingerprint surface of the finger 441 from a low angle. This light L8
And L9 are reflected by the unevenness of the fingerprint pattern, and the emitted light L1
0 is applied to the imaging device 443. Imaging device 443
Collects the light L10, forms an image, and converts it into an electric signal. As a result, an electric signal representing the fingerprint pattern can be obtained.

According to this embodiment, since light is applied from both directions of the light guide plate 440, the fingerprint surface is illuminated from both sides. For this reason, the amount of light applied to the imaging device 443 greatly increases, so that the S / N can be greatly improved and the shading of the fingerprint pattern image can be reduced.

Moreover, since this embodiment can be constituted by four members of the light sources 444 and 445, the light guide plate 440, and the imaging device 443,
This has the advantage that the structure is very simple.

FIG. 7 is a side view schematically showing the configuration of another embodiment of the present invention, and FIG. 8 is a plan view thereof.

This embodiment is basically the same as the embodiment of FIGS. 5 and 6, except for the end surface 540c of the light guide plate 540 on the light source 544 side, the end surface 540b of the light source 545 side, and the upper and lower surfaces. One side 540
The side surfaces of d and 540e are all mirror surfaces on which a metal such as aluminum is deposited.

According to this embodiment, the light incident from the left and right light sources 544 and 545 travels inside the light guide plate 540 while being reliably reflected on the two side surfaces without going outside, and reaches the through hole 547 for fingerprint collection. I do. As a result, the amount of light reflected by the unevenness of the fingerprint pattern of the finger 541 and applied to the imaging device 543 increases, and S / N can be improved.

FIG. 9 is a side view schematically showing a configuration of still another embodiment of the present invention, and FIG. 10 is a plan view thereof.

This embodiment is basically the same as the embodiment of FIGS. 5 and 6, except that the angle of the end surface 647a of the through hole 647 for fingerprint collection of the light guide plate 640 is different from that of FIGS. 5 and 6. This is different from the embodiment. That is, in the embodiment of FIGS. 5 and 6, the end face 447a
Is perpendicular to the upper and lower surfaces of the light guide plate 440, but in this embodiment, the through holes 647 are tapered end surfaces 647a that are inclined so as to expand downward. Therefore, light that travels in parallel from the light sources 644 and 645 in the light guide plate 640 and reaches the through hole 647 is greatly refracted at the end face 647a, and more light is applied to the fingerprint surface of the finger 641.
As a result, the amount of light reflected by the unevenness of the fingerprint pattern of the finger 641 and applied to the imaging device 643 is greatly increased, and the S / N can be greatly improved.

FIG. 11 is a side view schematically showing a configuration of still another embodiment of the present invention, and FIG. 12 is a plan view thereof.

9 and FIG. 10, the end face 647a of the through hole 647 for fingerprint collection of the light guide plate 640 is linearly inclined, whereas in this embodiment, the end face 747a of the through hole 747 is linearly inclined. Are inclined so as to spread downward in a parabolic manner. Therefore, light traveling from the light sources 744 and 745 in the light guide plate 740 in parallel and reaching the through hole 747 is refracted by the end face 747a so as to be focused on the fingerprint surface of the finger 741. As a result, the light is reflected by the unevenness of the fingerprint pattern of the
, The amount of light applied to the light emitting element is more greatly increased, and the S / N can be more greatly improved.

As described above, according to the invention of the present application, the fingerprint input device can be basically composed of the light source, the light guide plate having holes, and the imaging device, and thus a very small and inexpensive fingerprint input device can be provided. In addition, since the unevenness of the fingerprint and the light guide plate are not in contact with each other, it is possible to prevent the surface of the light guide plate from being stained due to the contact, and to avoid a temporal change due to the stain. That is, according to the fingerprint input device of the type in which a finger is brought into contact with a light guide plate or a prism, the surface of the light guide plate or the prism is stained, and the S / N gradually deteriorates due to the stain, and finally the fingerprint Recognition and collation may not be possible,
In addition, sometimes the fingerprint pattern of the previous finger remains, and there is a possibility that the recognition and collation of the fingerprint may be mistaken.

Furthermore, according to the invention of the present application, the position of the finger can be reliably fixed by the through hole, and the unevenness of the fingerprint can be clearly brought out by irradiating the finger with light at a low angle, S / N can be greatly improved.

[Effects of the Invention] According to the invention of the present application, a light guide plate having a through hole for placing a finger to input a fingerprint pattern, a light source, and a light guide plate for transmitting light from the light source from at least one surface of the light guide plate The light guide plate includes means for allowing light to enter at an incident angle at which light is totally reflected, and imaging means provided at a position facing the finger through the through hole of the light guide plate, and the light guide plate transmits the incident light to the through hole. It is configured to emit light from the end face and irradiate the finger, and the imaging unit is configured to receive light reflected by the fingerprint pattern of the finger, thereby providing a very small and inexpensive fingerprint input device. be able to. In addition, since the unevenness of the fingerprint and the light guide plate are not in contact with each other, it is possible to prevent the surface of the light guide plate from being stained due to the contact, and it is possible to avoid a temporal change due to the stain. Further, by irradiating the finger with light at a low angle, the unevenness of the fingerprint can be clearly brought out, so that the S / N can be significantly improved.

When the light guide plate has a reflective film on all surfaces except a surface on which light from a light source enters, an end surface of the through hole, and two surfaces orthogonal to the axis of the through hole, the light is reflected by the reflective film. Is reflected without returning to the outside and reaches the fingerprint collection portion again, so the amount of light applied to the imaging means is greatly increased, the shading of the fingerprint pattern image can be reduced, and the S / N can be greatly increased. Can be improved.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing the configuration of one reference example of the present application. FIG. 2 is a side view schematically showing the configuration of another embodiment of the first invention of the present application, FIG. 3 is a side view schematically showing the configuration of still another reference example of the present invention, and FIG. FIG. 5 is a side view schematically showing the configuration of still another reference example of the present application, FIG. 5 is a side view schematically showing the configuration of one embodiment of the present invention, and FIG.
FIG. 7 is a plan view, FIG. 7 is a side view schematically showing the configuration of another embodiment of the present invention, FIG. 8 is a plan view thereof, and FIG. 9 is a plan view of still another embodiment of the present invention. FIG. 10 is a side view schematically showing the configuration, FIG. 10 is a plan view thereof, FIG. 11 is a side view schematically showing the configuration of still another embodiment of the present invention, and FIG.
FIG. 1 is a plan view, and FIGS. 13, 14 and 15 are side views of a conventional fingerprint input device. 40, 140, 240, 340, 440, 540, 640, 740 …… Light guide plate, 4
0a, 240a, 340a: Fingerprint collection part, 41, 241, 341, 44
1, 541, 641, 741 ... finger, 42 ... prism, 43, 143, 2
43, 343, 443, 543, 643, 743 ... Imaging device, 44, 1
44, 244, 245, 344, 444, 445, 544, 545, 644, 645, 7
44, 745: Light source, 447, 547, 647, 747 ... Through holes.

Claims (2)

(57) [Claims] 1. A light guide plate having a through hole for placing a finger to input a fingerprint pattern, a light source, and light from the light source being transmitted from at least one surface of the light guide plate into the light guide plate. The light guide plate is provided with means for making the light incident at an angle of total reflection, and imaging means provided at a position facing the finger through the through hole of the light guide plate, and the light guide plate passes the incident light through the light guide plate. A fingerprint input device configured to emit light from an end face of the hole to irradiate the finger, and the imaging unit is configured to receive the light reflected by a fingerprint pattern of the finger. . 2. The light guide plate according to claim 1, wherein the light guide plate has a surface on which light from the light source is incident, an end surface of the through hole, and an axis perpendicular to the axis of the through hole.
2. The fingerprint input device according to claim 1, wherein a reflection film is provided on all surfaces except for one surface.