KR20040071848A - Fingerprint recognition device - Google Patents

Abstract

PURPOSE: A device for recognizing a fingerprint is provided to realize the effective lighting, and improve resolution and contrast by lighting the fingerprint of a finger through the total reflection on the first surface of a light guide plate, and reduce noises by setting a space between a transparent plate and the light guide plate. CONSTITUTION: The light guide plate(11) has the first surface fully reflecting the light irradiated from a side and the second surface that is an opposite surface of the first surface, and fully reflects the light by many projections formed on the first surface. The transparent plate(12) is placed in front of the second surface of the light guide plate and is touched by the fingerprint. A light source(13) is installed to the side of the light guide plate. An objective lens(15) images a fingerprint image passing the first surface of the light guide plate. A CCD(Charge Coupled Device)(16) captures the fingerprint image irradiated through the objective lens.

Description

Fingerprint recognition device

The present invention relates to a fingerprint recognition device, and more particularly, to a fingerprint recognition device having a light guide plate having a plurality of fine prism deflectors integrally formed on one surface.

Fingerprint recognition devices are commonly used for identity verification, access security, and many other purposes. Authentication functions used in the fingerprint recognition device may be classified in several ways. First, the illumination light is irradiated to the portion where the fingerprint is placed, and the image of the totally reflected fingerprint is imaged on the image sensor through the imaging lens. In the second method, a fingerprint is directly contacted with a sensor surface and recognized using the pressure difference. The third method is an optical method in which an auxiliary light is irradiated to the side of the sensor surface so that the fingerprint makes an image directly on the sensor surface.

The third optical method among the methods listed above is the most commonly used method. An optical method uses an optical prism to form an image of a fingerprint on a CCD sensor by total reflection of illumination light. Typically, the size of the fingerprint is not different and is constant, so the size of the prism is almost constant. Of course, the size of the optical prism can be reduced by allowing a fingerprint of a finger other than the thumb to be recognized, but there are limitations. Therefore, the optical prism is essential in the optical method, and thus there is a problem that the overall size can not be reduced.

An example of the optical method is disclosed in Korean Patent Laid-Open Publication No. 2002-69882, which uses an optical prism to illuminate light at a fingerprint site, and the light reflected at the fingerprint site passes through an imaging optical system through total reflection of the prism. To form an image on the CCD. This method basically uses an optical prism. In the optical method, a prism type housing is also used, which is disclosed in Patent Publication No. 92-10082. In these methods, since the axes of the fingerprint and the optical system are inclined with respect to each other, distortion occurs in the image of the formed fingerprint, and the configuration of the imaging optical system is also difficult.

Unexamined-Japanese-Patent No. 2002-123822 is mentioned by the method which does not use an optical prism differently from the above optical system. This is configured to illuminate the light generated from the side toward the fingerprint by using the light guide plate and the diffuser plate, and image it on the CCD through an imaging lens. In such a configuration, it is difficult to irradiate constant light on the front of the fingerprint, and additional components such as a diffusion sheet are added, causing a price increase.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an improved fingerprint recognition device.

Another object of the present invention is to provide a fingerprint recognition apparatus capable of irradiating illumination light without using an optical prism.

It is another object of the present invention to provide a fingerprint recognition device having a light guide plate having a specific shape that enables total reflection of illumination light on one surface.

1 is a perspective view showing a schematic configuration of a fingerprint recognition device according to the present invention.

2 illustrates a schematic side view of the fingerprint recognition device illustrated in FIG. 1.

3 schematically shows the configuration of another embodiment of the fingerprint recognition apparatus according to the present invention.

4 is an enlarged cross-sectional view showing the shape of the projection of the light guide plate included in the fingerprint recognition device according to the present invention.

<Brief Description of Major Codes in Drawings>

11. Light guide plate 12. Transparent flat plate

13. Light source 14. Reflector

15. Imaging Lens 16. Imaging Device

In order to achieve the above object, according to the present invention, there is provided a light guide plate including a first surface on which light incident from a side is totally reflected and a second surface opposite to the first surface; A transparent plate disposed in front of the second surface of the light guide plate and in which a fingerprint of a finger is in contact; A light source disposed at a side of the light guide plate; An imaging lens for forming an image of a fingerprint transmitted through the first surface of the light guide plate; Provided is a fingerprint recognition device comprising; an image pickup device for picking up an image of a fingerprint incident through the imaging lens.

In addition, according to the present invention, there is provided a light guide plate having a first surface on which light incident from a side is totally reflected and a second surface opposite to the first surface; A transparent plate disposed in front of the second surface of the light guide plate and in which a fingerprint of a finger is in contact; A light source disposed at a side of the light guide plate; At least one mirror disposed at an angle with respect to the first surface of the light guide plate to reflect an image of a fingerprint transmitted through the first surface of the light guide plate; An imaging lens for forming light reflected from the at least one mirror; Provided is a fingerprint recognition device comprising; an image pickup device for picking up an image of a fingerprint incident through the imaging lens.

According to an aspect of the present invention, the light source further includes a reflector surrounding the light source to reflect the light reflected from the light guide plate.

In addition, according to another feature of the invention, the light from the light source is totally reflected by a plurality of projections formed on the first surface of the light guide plate.

According to another feature of the invention, the distance between the fingerprint contact surface of the transparent plate and the imaging lens is 20 to 25 mm.

According to another feature of the invention, the distance between the fingerprint contact surface of the transparent plate and the imaging lens is 10 to 15 mm.

Hereinafter, the present invention will be described in more detail.

The present invention provides a manner in which illumination light can be irradiated to a fingerprint without using an optical prism. While the light refracts between the medium and the medium, the light has a total reflection angle in which the incident light does not refraction but totally reflects due to the relationship between the refractive index difference between the medium and the incident angle. In the present invention, the total reflection characteristic is used to allow the light incident from the light source disposed on the side of the light guide plate to be totally reflected on one surface of the light guide plate. Therefore, the light incident from the light source disposed on the side of the light guide plate to the inside of the light guide plate is totally reflected at the first surface of the light guide plate and exits to the second surface. When the second surface is set as a surface for recognizing a fingerprint, light reflected from the fingerprint is incident to the light guide plate again. The angle of incidence of the light reflected from the fingerprint and incident on the light guide plate is nearly perpendicular to the plane of the light guide plate so that most of the light passes through the first surface of the light guide plate. In this way, the light transmitted through the first surface of the light guide plate is formed on the imaging device through the imaging lens.

The present invention will be described in more detail with reference to an embodiment shown in the accompanying drawings.

1 is a perspective view showing a schematic configuration of a fingerprint recognition device according to the present invention.

Referring to the drawings, the fingerprint recognition apparatus includes a light guide plate 11 having a first surface 11a through which light incident from the side is totally reflected, and a second surface 11b opposite to the first surface 11a; The transparent plate 12 disposed on the second surface 11b of the light guide plate 11, the light source 13 disposed on the side surface of the light guide plate 11, and the light reflected from the light source 13 are disposed on the light guide plate 11. Incident through the imaging lens 15 and the imaging lens 15 for forming an image of a fingerprint transmitted through the first surface 11a of the light guide plate 11. An imaging device 16 for imaging an image of the fingerprint is provided.

In the light guide plate 11, the surface viewed from the front in FIG. 1 becomes the first surface 11 a, and the light incident directly from the light source 13 disposed on the side surface of the light guide plate 11 in the first surface 11 a. Total reflection occurs for. This total reflection action is made possible by forming a large number of fine surfaces inclined at a predetermined angle on the first surface 11a. Therefore, the light incident from the side surface of the light guide plate 11 will be totally reflected at the first surface 11a and exit to the second surface 11b.

The opposite side of the first surface 11a of the light guide plate 11 becomes the second surface 11b. Unlike the first surface 11a, the second surface 11b is formed as a flat plate having a smooth surface. Light incident directly on the second surface 11b from the light source 13 disposed on the side of the light guide plate 11 is transmitted or reflected depending on the incident angle. The light transmitted through the second surface 11b illuminates the fingerprint located on the surface of the transparent flat plate 12, and the light reflected from the second surface 11b is incident on the first surface 11a again to be totally reflected. will be.

The transparent plate 12 is intended to perform a fingerprint recognition action by bringing a finger into contact with the surface thereof. The transparent flat plate 12 is preferably arranged at a predetermined interval from the light guide plate 11. The transparent plate 12 serves to limit the light guide plate 11 from coming into direct contact with the external environment, thereby ensuring reliability and permanence with respect to the transmission of light through the light guide plate 11. If the transparent flat plate 12 and the light guide plate 11 are in contact with each other, noise may be generated to reduce resolution and contrast in the image of the fingerprint. Therefore, the transparent plate 12 and the light guide plate 11 should be spaced apart so that there is a predetermined gap therebetween.

The light source 13 is a light emitting element such as a light emitting diode arranged on the side of the light guide plate 11. The light incident from the light source 13 is totally reflected on the first surface 11a and transmitted through the second surface 11b to illuminate the fingerprint of the finger in contact with the transparent flat plate 12. One to five light emitting diodes used as the light source 13 may be disposed along the side surface of the light guide plate 11.

The reflection shade 14 may be provided to allow the light emitted from the light source 13 to be incident more efficiently into the light guide plate 11. The reflector 12 is formed to surround the outside of the light source 13 except for the side of the light guide plate 11, and a material having a high reflectance is coated on the inner surface thereof. Light reflected from the inner surface of the reflector 12 is incident on the light guide plate 11 to illuminate the fingerprint through the second surface 11b of the light guide plate 11. It is to be understood that the reflection shade 12 is optional and that the reflection shade improves the efficiency of the device and that fingerprint recognition is possible even without the reflection shade 12.

The image of the fingerprint in contact with the transparent plate 12 may be illuminated and transmitted through the transparent plate 12 and the light guide plate 11. Since the second surface 11b of the light guide plate 11 is a smooth surface, transmission is possible, and the image of the fingerprint is vertically incident on the first surface 11a of the light guide plate 11, so that transmission is also possible.

The image of the transmitted fingerprint may be imaged through the imaging lens 15 and sensed by the imaging device 16. The imaging lens 15 should be spaced apart from the light guide plate 11 by a predetermined distance so as to image the entire image of the fingerprint incident through the light guide plate 11. For example, the distance between the surface of the transparent flat plate 12 to which the fingerprint of the finger is in contact with the imaging lens lens 15 is preferably 20 mm to 25 mm.

2 illustrates a schematic side view of the fingerprint recognition device illustrated in FIG. 1. In Fig. 2, the configurations indicated by the same numbers as those in Fig. 1 are the same as those shown in Fig. 1. In FIG. 2, the imaging lens and the image pickup device are omitted for convenience of illustration.

Referring to the drawings, it can be seen that the fingerprint 21 can be illuminated by the contact of the finger 21 on the surface of the transparent plate 12. The fingerprint is illuminated by the light incident from the light source 13 incident through the second surface 11b of the light guide plate 11 and the transparent flat plate 12. In addition, since the light reflected from the fingerprint of the finger 21 is incident almost perpendicularly to the first surface 11a of the light guide plate 11, the projections 22 formed on the first surface 11a of the light guide plate 11 are formed. It can be transmitted to the imaging lens 15 (FIG. 1) without being totally reflected following the action. As described above, the projection 22 is incident on the first surface 11a of the light guide plate 11 when the light illuminated from the light source 13 disposed on the side of the light guide plate 11 to the inside of the light guide plate 11 is incident. It has a shape which can totally reflect this to the second surface 11b.

3 schematically shows the configuration of another embodiment of the fingerprint recognition apparatus according to the present invention. In Fig. 3, the configurations indicated by the same numbers as those in Fig. 1 are the same as the configurations shown in Fig. 1.

Referring to the drawing, a transparent plate 12 is disposed on the front surface of the light guide plate 11, and a fingerprint of a finger is contacted with the transparent plate 12. A projection for total reflection is formed on one surface of the light guide plate 11 as in the example shown in FIG. 2.

The fingerprint recognition device shown in FIG. 3 is characterized by at least one mirror for changing the path of light. In the embodiment shown in the figure, a first mirror 31 and a second mirror 32 are provided. The first mirror 31 reflects the image of the fingerprint incident from the light guide plate 11 toward the second mirror 32, and the second mirror 32 injects the image of the fingerprint into the imaging lens 33 again. An image of a fingerprint formed through the imaging lens 33 is detected by the imaging device 34.

In the example shown in FIG. 3, the thickness of the fingerprint recognition device may be reduced by at least one mirror. That is, the thickness of the entire fingerprint recognition device can be reduced by the first mirror 31 and the second mirror 32. In the example shown in FIGS. 1 and 2, a relatively wide predetermined distance exists between the light guide plate 11 and the imaging lens 15 so that the image of the fingerprint passing through the light guide plate 11 is formed on the imaging lens 15. On the other hand, in the example shown in FIG. 3, since the first and second mirrors 31 and 32 are provided, the imaging lens 33 can be disposed relatively closer to the light guide plate 11. Therefore, the thickness of the entire fingerprint recognition device can be made thin. For example, by using the first and second mirrors 31 and 32, the distance from the surface of the transparent flat plate 12 to which the fingerprint contacts the imaging lens 33 can be realized between 10 mm and 15 mm. .

4 is an enlarged cross-sectional view of protrusions formed on the light guide plate 11.

Referring to the drawings, the projection is formed by repeatedly the hill 41 and the valley 42, the distance (L) between the mountain is 150 to 250 micrometers, the valley from the top of the mountain 41 ( The depth h to 42 is 3 to 8 micrometers, and the angle a formed between the horizontal line passing through the top of the mountain 41 and the line extending from the top of the mountain 41 to the valley 42. ) Is 42 degrees to 48 degrees. Those skilled in the art will understand the shape of the projections from FIG.

In the fingerprint recognition apparatus according to the present invention, since most of the light generated from the light source disposed on the side of the light guide plate is totally reflected on the first surface of the light guide plate to illuminate the fingerprint of the finger, effective illumination is achieved, and resolution and contrast are improved. There is an advantage to be improved. In addition, by setting a gap between the transparent plate and the light guide plate, noise can be reduced, and when the mirror is used, the overall thickness can be reduced.

Although the present invention has been described with reference to one embodiment shown in the accompanying drawings, this is only illustrative, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Could be. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (5)

A light guide plate having a first surface through which light incident from the side surface is totally reflected, and a second surface opposite to the first surface, wherein the light is totally reflected by a plurality of protrusions formed on the first surface; A transparent plate disposed in front of the second surface of the light guide plate and in which a fingerprint of a finger is in contact; A light source disposed at a side of the light guide plate; An imaging lens for forming an image of a fingerprint transmitted through the first surface of the light guide plate; And an imaging device for capturing an image of a fingerprint incident through the imaging lens. A light guide plate having a first surface through which light incident from the side surface is totally reflected, and a second surface opposite to the first surface, wherein the light is totally reflected by a plurality of protrusions formed on the first surface; A transparent plate disposed in front of the second surface of the light guide plate and in which a fingerprint of a finger is in contact; A light source disposed at a side of the light guide plate; At least one mirror disposed at an angle with respect to the first surface of the light guide plate to reflect an image of a fingerprint transmitted through the first surface of the light guide plate; An imaging lens for forming light reflected from the at least one mirror; And an imaging device for capturing an image of a fingerprint incident through the imaging lens. The method according to claim 1 or 2, And a reflecting unit surrounding the light source to reflect the light reflected from the light source into the light guide plate. The method of claim 1, And a distance between the fingerprint contact surface of the transparent plate and the imaging lens is 20 to 25 mm. The method of claim 2, A distance between the fingerprint contact surface of the transparent plate and the imaging lens is 10 to 15 mm.