Patent Publication Number: US-2011063077-A1

Title: Vein authentication apparatus using total internal reflection

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2009-0087689, filed on Sep. 16, 2009, entitled “Vein Authentication Device using Total Internal Reflection,” which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a vein authentication apparatus using total internal reflection in which a protective panel for total internal reflection is provided between a light source and an imaging element, thereby realizing a small size and a slim shape. 
     2. Description of the Related Art 
     Recently, with the increased importance of personal information, the need to use biometric authentication technology as a means of protecting information or performing personal identification is rapidly increasing. Such a biometric authentication apparatus is operated as described below. 
     First, the biometric authentication apparatus is subjected to a user registration process. The user registration process is performed in such a way that the biometric authentication apparatus extracts the biometric features of a person to be registered by reading them and then stores them in a database. Meanwhile, an authentication process is performed in such a way as to authenticate a user by comparing the user&#39;s biometric features with the features stored in the database. 
     Currently, features used by biometric authentication systems include the faces, voices, the shapes of the hands, the irises, the veins, and fingerprints. Research into each type of feature is being actively carried out. 
     In particular, a biometric authentication system using veins can perform authentication only by presenting part of a human body, such as a user&#39;s hand or finger to the system. Accordingly, the vein authentication apparatus using veins meets with low psychological resistance from a user. Furthermore, since the vein authentication apparatus uses the internal information of a living body, it is robust against counterfeiting. 
     In particular, a finger vein authentication apparatus will now be described. First, the finger vein authentication apparatus radiates infrared light onto a finger. Then, the infrared light scatters inside the finger and then is transmitted to the outside. 
     Thereafter, the finger vein authentication apparatus captures the infrared light transmitted through the palm side of the finger. 
     Here, the hemoglobin of the blood absorbs infrared light from the surrounding cells. 
     Accordingly, an image captured by the finger vein authentication apparatus visualizes blood vessels distributed throughout the hypodermis of the palm side of the finger (finger veins) in the form of a dark shadow pattern (a finger vein pattern). 
     The finger vein authentication apparatus registers the features of the finger vein pattern in advance. 
     When authentication is performed, the finger vein authentication apparatus captures an image of the finger presented by a user. Thereafter, the finger vein authentication apparatus performs personal authentication by comparing the finger vein pattern of the captured image with the features which were registered in advance. 
       FIG. 1  is a diagram showing the construction of a conventional finger vein authentication apparatus  10 . The finger vein authentication apparatus  10  includes a light source  1 , a camera  2 , slits  5  and  6 , and a rotating plate  7 . 
     In the above-described finger vein authentication apparatus  10 , near infrared light emitted from the light source  1  is deprived of interference light while passing through the slit  5 , and is projected onto a finger, which is a target to be measured. 
     Thereafter, the near infrared light reflected from the finger, which is a target to be measured, is deprived of interference light while passing through the filter  6 , and then forms an image on the image sensor of the camera  2 , which is an imaging element. 
     The authentication apparatus  10  uses the rotating plate  7 , as shown in the drawing. The rotating plate  7  enables measurement while rotating the target to be measured, thereby enabling three-dimensional (3D) finger vein pattern data to be acquired. The finger vein pattern acquired by the authentication apparatus  10  is subjected to image processing using a program algorithm, and is then used as final vein recognition data. 
       FIG. 2  is a diagram showing the construction of another conventional finger vein authentication apparatus  20 . The vein authentication apparatus  20  includes a light source  23 , a transparent acrylic plate  24 , an imaging device  25 , a transmission filter  26 , and a rest  27 . 
     In the authentication apparatus  20 , light emitted by the near infrared light source  23  is radiated onto a finger, that is, a target  21  to be measured, and light including vein pattern information is reflected, passes through the transparent acrylic plate  24 , and forms an image on the image sensor of the imaging device  25 . 
     Here, in order to acquire vein pattern data, an infrared transmission filter  26  for acquiring an image of near infrared rays while blocking visible rays is disposed in front of the imaging device  25 . Here, an optical axis  28  and a capture direction  29  are set to directions perpendicular to the direction of the finger which is placed on the rest  27 . 
     However, the conventional authentication apparatuses are implemented in the form of independent measuring apparatuses and perform vein authentication, so that they have size and cost problems. In particular, the shapes of the conventional apparatuses are limited in application to mobile phone terminals because they do not meet the requirements of a small size and a slim shape. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and the present invention is directed to a vein authentication apparatus which is capable of providing the path of light emitted by a light source using a protective panel for total internal reflection for totally reflecting the light emitted by the light source, so that a small size and a slim shape can be realized, thereby enabling the authentication apparatus to be installed in a mobile phone terminal. 
     In order to accomplish the above object, the present invention provides a vein authentication apparatus, including a protective panel made of a plate-shaped transparent material, provided with a finger-resting surface on which a fingertip is placed, provided with a light entry hole which is formed on one side of a surface opposite the finger-resting surface with respect to a reference line and which is configured to receive near infrared rays and totally reflect the near infrared rays toward the fingertip placed on the finger-resting surface, and provided with a light exit hole which is formed on the other side of the surface opposite the finger-resting surface with respect to the reference line, which is opposite the side on which the light entry hole is disposed, and which is configured to emit light reflected from the fingertip; a light source located adjacent to the light entry hole of the protective panel, and configured to emit the near infrared rays; an imaging element located adjacent to the light exit hole of the protective panel, and configured to receive the light reflected from the fingertip and then acquire a vein pattern; a light entry-side diffraction element located in the light entry hole of the protective panel, and configured to guide the light emitted by the light source toward the fingertip; a light exit-side diffraction element located in the light exit hole of the protective panel, and configured to guide the light reflected from the fingertip toward the imaging element; and an authentication unit configured to perform vein authentication using the vein pattern acquired by the imaging element. 
     The protective panel is located on a surface of an LCD panel of a portable terminal, the light source is located on one side of the LCD panel, and the imaging element is located on a remaining side of the LCD panel opposite that on which the light source is located. 
     A finger-resting surface partitioned off from the protective panel is located within the LCD panel. 
     The light entry-side diffraction element and the light exit-side diffraction element are formed of diffraction gratings. 
     The vein authentication apparatus further includes a visual light blocking filter for blocking visible rays, the visual light blocking filter being disposed between the protective panel and the imaging element. 
     The vein authentication apparatus further includes a condenser lens for condensing the reflected light onto the imaging element, the condenser lens being disposed between the protective panel and the imaging element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram showing the construction of a conventional finger vein authentication apparatus; 
         FIG. 2  is a diagram showing the construction of another conventional finger vein authentication apparatus; 
         FIG. 3  is a diagram showing the construction of a vein authentication apparatus using total internal reflection according to an embodiment of the present invention; 
         FIG. 4  is a sectional view showing an application in which the vein authentication apparatus using total internal reflection according to the embodiment of the present invention has been applied to a mobile phone terminal; 
         FIG. 5A  is a plan view showing a vein authentication apparatus according to an embodiment of the present invention, which has been applied to a mobile phone terminal; and 
         FIG. 5B  is a diagram showing the vein authentication apparatus with a fingertip placed on a finger-resting surface. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A vein authentication apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used throughout the different drawings to designate the same or corresponding components, and related redundant descriptions will be omitted. 
       FIG. 3  is a diagram showing the construction of a vein authentication apparatus using total internal reflection according to an embodiment of the present invention. 
     As shown in  FIG. 3 , the vein authentication apparatus using total internal reflection according to the embodiment of the present invention includes a light source  30 , a light entry-side diffraction element  31 , a protective panel for total internal reflection  32 , a light exit-side diffraction element  33 , an imaging element  34 , a control unit  40 , a light source drive unit  41 , an imaging element drive unit  42 , an image processing unit  43 , an authentication unit  44 , and a pattern maintaining unit  45 . 
     The light source  30  radiates light to a fingertip  50 , and is formed of, for example, a Light Emitting Diode (LED). 
     The light source  30  is disposed opposite the imaging element  34  with respect to the fingertip  50 , and is disposed at a location opposite that of the imaging element  34  in the transverse direction (the x direction) of the fingertip  50 . The light source  30  radiates light in a wavelength range of 700 to 1200 nm so as to capture a user&#39;s veins, which are internal organs of the fingertip  50 . 
     Meanwhile, the light entry-side diffraction element  31  is disposed in a light entry hole adjacent to the light source  30  of the protective panel  32 , that is, is disposed adjacent to the light source  30 , and guides light, emitted from the light source  30 , toward the fingertip  50  placed on the protective panel  32 . 
     The light exit-side diffraction element  33  is disposed in a light exit hole adjacent to the imaging element  34  of the protective panel  32 , that is, is disposed adjacent to the imaging element  34 , and guides light, reflected from the fingertip  50  and moved away from the fingertip  50 , toward the imaging element  34 . 
     The light exit-side diffraction element  33  is disposed opposite the light entry-side diffraction element  31  with respect to the fingertip  50 , and is disposed opposite the light entry-side diffraction element  31  in the transverse direction (x direction) of the fingertip  50 . 
     Diffraction gratings may be used as the diffraction elements  31  and  33 . The specifications of the diffraction gratings are determined depending on the wavelength of the near infrared light source  30  used for the measurement of a vein pattern and the thickness and refractive index of the protective panel  32 . 
     For example, when the wavelength of the light source  30  falls within the near infrared region of 700-4200 nm, the thickness of the protective panel  32  is 1 mm and the refractive index of the protective panel  32  is 1.5, it is preferred that the diffraction gratings have a grating period in the range of 500-900 nm. Such a diffraction grating with such a period can be manufactured by forming a master using a semiconductor process using lithography or a photo mask, performing stamper work and finally conducting a molding process. 
     The protective panel  32  is made of a plate-shaped transparent material, and has a finger-resting surface on which the fingertip  50  is placed. The finger-resting surface may be located at the center of the protective panel  32 , or may be located on one side of the protective panel  32 . In particular, it is preferred that the finger-resting surface be located above the center of the protective panel  32 . 
     As described above, the protective panel  32  provides a region (surface) on which the fingertip  50  is placed. However, it is not necessary to directly bring the fingertip  50  into contact with the protective panel  32  and the fingertip  50  may be merely placed above the protective panel  32 . 
     The protective panel  32  is made of a plate-shaped transparent material as described above, thereby preventing impurities, such as dust, from entering into the apparatus. 
     Furthermore, the protective panel  32  is provided with the light entry hole on one side of a surface opposite the finger-resting surface, and the light entry hole receives near infrared rays and totally reflects the near infrared rays toward the fingertip  50  placed on the finger-resting surface. Furthermore, the protective panel  32  is provided with the light exit hole on the other side of the surface opposite the finger-resting surface, which is opposite the side on which the light entry hole, and emits light reflected from the fingertip  50 . 
     The protective panel  32  constructed as described above totally reflects incident light so as to direct the incident light toward the fingertip  50  placed on the protective panel  32  and direct light reflected from the fingertip  50  toward the light exit-side diffraction element  33 . 
     Here, total internal reflection refers to a phenomenon in which light with an incident angle equal to or grater than a specific angle is entirely reflected from the boundary surface of a medium, and is used for optical communication using optical fiber. The protective panel  32  is made of transparent material such as glass or resin. 
     An element for transmitting only near infrared light may be used as the protective panel  32 . If so, unnecessary light, such as solar light or fluorescent lamp light, can be prevented when a vein pattern is captured. 
     Meanwhile, the imaging element  34  is disposed adjacent to the light exit hole of the protective panel  32 , captures light reflected from the inside of the fingertip  50  and emitted from the desired protective panel  32 , and is formed of, for example, a CCD or a CMOS sensor. 
     In order to extract and use only a vein pattern using near infrared light, a visual light blocking filter (not shown) may be used as the imaging element  34 . 
     The visual light blocking filter may be disposed between the light exit-side diffraction element  33  and the imaging element  34 , and limits the entry of incident light into the imaging element  34  by selectively blocking the light emitted by the light exit-side diffraction element  33 . 
     A condenser lens (not shown) may be disposed between the imaging element  34  and the protective panel  32  so as to condense light radiated onto the fingertip  50  by forming an image of the desired target surface of the fingertip  50  on the light receiving surface of the imaging element  34 . However, the thickness or diameter of the condenser lens may be appropriately set by taking into account the desired magnification of a formed image or resolution. 
     Meanwhile, the image processing unit  43 , under the control of the control unit  40 , performs predetermined image processing on captured data obtained by the imaging element  34  and outputs the captured data to the authentication unit  44 . The image processing unit  43 , and the authentication unit  44  and the control unit  40 , which will be described later, are formed of, for example, a microcomputer. 
     The pattern maintaining unit  45  maintains a vein authentication pattern (which is a comparative pattern to be compared with a captured pattern acquired when authentication is performed and is acquired by previously capturing finger veins), and is formed of to nonvolatile memory (for example, Electrically Erasable Programmable Read Only Memory (EEPROM)). 
     The authentication unit  44 , under the control of the control unit  40 , authenticates the fingertip  50  by comparing a vein pattern output by the image processing unit  43  with the vein authentication pattern maintained by the pattern maintaining unit  45 . 
     The light source drive unit  41  operates the light source  30  in response to the control of the control unit  40 . The imaging element drive unit  42  performs image capturing driving (light receiving driving) on the imaging element  34  in response to the control of the control unit  40 . The control unit  40  controls the operation of the image processing unit  43 , the authentication unit  44 , the light source drive unit  41  and the imaging element drive unit  42 . 
     Next, the operation and advantages of the vein authentication apparatus using total internal reflection according to the embodiment of the present invention will be described below. 
     In the vein authentication apparatus, when the fingertip  50  is placed on the protective panel  32 , the light source  30  is operated by the light source drive unit  41 , and near infrared rays are emitted by the light source  30 . 
     Meanwhile, the path of the light emitted by the light source  30  is changed by the light entry-side diffraction element  31  such that it can be directed toward the fingertip  50 . 
     When the path of the light emitted by the light source  30  is changed by the light entry-side diffraction element  31 , the light is incident on the upper surface of the protective panel  32  on which the fingertip  50  is placed, in which case the protective panel  32  performs total reflection such that the incident light is directed toward the lower surface of the protective panel  32  opposite the upper surface of the protective panel  32  on which the fingertip  50  is placed. 
     Thereafter, the light incident on the lower surface of the protective panel  32  opposite the upper surface on which the fingertip  50  is placed is totally reflected by the upper surface opposite the lower surface on which the fingertip  50  is placed, so that the incident light can be directed toward the fingertip  50 . 
     Thereafter, the light incident on the fingertip  50  is reflected by the fingertip  50 , and is then scattered in all directions. 
     Thereafter, the light which meets the total reflection requirement of the protective panel  32  is finally directed toward the light exit-side diffraction element  33  located in the light exit hole of the protective panel  32 . 
     Thereafter, the light exit-side diffraction element  33  passes the light reflected from the fingertip  50  placed on the protective panel  32  toward the imaging element  34  so that the reflected light is focused on the light receiving surface of the imaging element  34 . By doing so, the captured data of the veins of the fingertip  50  is acquired by the imaging element  34 . 
     Thereafter, the vein pattern acquired by the imaging element  34  is subjected to appropriate image processing by the image processing unit  43 , and is input to the authentication unit  44 . The authentication unit  44  performs authentication by comparing the input vein pattern with the authentication pattern used for vein authentication and maintained by the pattern maintaining unit  45 . As a result, a vein authentication result (authentication result data Dout) is output, thus completing vein authentication. 
     Meanwhile, since the vein authentication apparatus using total internal reflection according to the embodiment of the present invention can be implemented in a small size and a slim shape, it can be applied to a portable terminal. 
       FIG. 4  is a sectional view showing an application in which the vein authentication apparatus using total internal reflection according to the embodiment of the present invention has been applied to a mobile phone terminal  70 . 
     As shown in  FIG. 4 , the vein authentication apparatus according to the embodiment of the present invention is installed on the mobile phone terminal  70 . 
     A light source  30  is located on one side of an LCD panel  70 , and is located opposite the imaging element  34  with respect to a fingertip  50 , that is, opposite an imaging element  34  in the transverse direction (the x direction) of the fingertip  50 . 
     Next, a protective panel  32  is located to cover the upper surface of the LCD panel  70 , and protects the LCD panel  70  from the outside. A light entry-side diffraction element  32  is disposed in a light entry hole adjacent to the light source  30 , while a light exit-side diffraction element  33  is disposed in a light exit hole adjacent to the imaging element  34 . 
     Meanwhile, the imaging element  34  is located on the outer side of the LCD panel  70 , and is located on the side opposite that on which the light source  30  is located with respect to the fingertip  50 . 
     As described above, the light source  30  and the imaging element  34  are located on respective sides of the LCD panel  70 , and the protective panel  32  is placed above the LCD panel  70 , so that the vein authentication apparatus according to the embodiment of the present invention enables the application of the present invention to be applied to a mobile phone terminal without increasing the size of the mobile phone terminal. 
       FIG. 5A  is a plan view showing a vein authentication apparatus according to an embodiment of the present invention, which has been applied to a mobile phone terminal  60 . The surface of the vein authentication apparatus is formed of the surface of a protective panel  32  covering an LCD panel  70  in the mobile phone terminal  60  including the LCD panel  70  and a keypad  80 . 
     A part of the surface of the vein authentication apparatus is partitioned off, and forms a finger-resting surface  32   a  capable of recognizing a vein pattern when a finger of a measurement target is placed thereon. 
     In order to increase the accuracy of the recognition of the veins of the finger, the finger-resting surface  32   a  formed by partitioning off a part of the surface of the vein to authentication apparatus may be formed to be smaller than the surface of the LCD panel  70 , as shown in  FIG. 5A . 
     It will be apparent that the size of the finger-resting surface  32   a  may be implemented to be larger than that of the LCD panel  70 . 
     Here, since the finger-resting surface  32   a  has a flat structure as a whole, the authentication apparatus is able to be installed on apparatuses which do not allow depressed and protruding shapes due to physical and design limitations, such as a notebook Personal Computer (PC), a Personal Digital Assistant (PDA), the surface of a keyboard, and the surface of the manipulation panel of an Automatic Teller Machine (ATM), in addition to a mobile phone terminal. 
       FIG. 5B  is a diagram showing the vein authentication apparatus with the fingertip  50  placed on the finger-resting surface  32   a.    
     According to the above-described present invention, it is possible to implement a small and slim vein authentication apparatus so that it can be applied to a mobile phone terminal. 
     Furthermore, according to the present invention, it is possible to impart a user authentication function using biometric information to a mobile phone terminal, so that an advantage arises in that the security of a mobile phone terminal can be significantly increased. 
     Moreover, according to the present invention, user authentication can be made only by bringing a user&#39;s finger to the LCD screen of a mobile phone terminal, so that another advantage arises in that the user&#39;s convenience can be significantly increased. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.