FR2890208A1 - Fingerprint identification assembly for use in e.g. cellular phone, has light source illuminating fingerprint, where illuminated fingerprint is re-illuminated to sensor by multiple reflective surfaces - Google Patents

Abstract

The assembly has an objective lens (11) mounted on top of a body (6) for receiving a fingertip. A reflective lens is mounted on a bottom of the body to receive reflected light from the objective lens. A light source (4) emits light to the reflective lens. A sensor (10) receives the reflected light from the reflective lens to compare the received reflected light with information stored inside the sensor. The light source illuminates a fingerprint, where the illuminated fingerprint is re-illuminated to the sensor by multiple reflective surfaces.

Description

DIGITAL IMPRESSION IDENTIFICATION ASSEMBLY USING THE REFLECTION

  TOTAL TO IDENTIFY A REASON FOR THE DIGITAL FOOTPRINT

  The present invention relates to a fingerprint identification assembly, and more particularly, to a fingerprint identification assembly having a first reflection lens and a second reflection lens, such that a reflection The total pattern of the fingerprint on the top of an objective lens of the set is completed and detected by a detector of the set.

  Fingerprint identification is probably one of the oldest and most established methods of identifying a person. It belongs to the field of biometrics, that is to say the identification of people by measuring or detecting parts of the human body, which is important for many applications. Many automated techniques are currently in use or in development, including reading hand lines, reading finger pores, identifying hand geometry, and recognizing the iris, retina or of the face. Of these, fingerprint identification is relatively straightforward, and it now promises to be more widely accepted, since it is convenient and a safe alternative to typed passwords, keys or signature to access restricted areas or information.

  Basically, the identification task involves determining the identity of an unknown person based on a fingerprint pattern fragment, or verifying the identity of a known person up to a certain level. certainty based on the reason for the specific fingerprint. The exact identification of the characteristics of the fingerprint is desired for a universal need, that is to say, different machines can recognize the characteristics. On the other hand, in many situations, the identifications are not necessarily universal, but only require clear resolution. The ends of human fingers have distinctive patterns of curved ridges, with a period of about 0.5 to about 1.0 mm and a depth of about 0.1 mm. The finger tissue diffuses the red light with a scattering reflectivity of about 50%, and the index of refraction of a finger is about 1.51. It may be desirable to have as wide a field of view as possible with minimal distortion to provide more features for identification and more margin of error in finger placement for the need for universal identification. On the other hand, with a touch platform on which a fingerprint will be identified, the actual size of the fingerprint could be about 10 mm, but the size of the system should be relatively small, less than 10 mm for mobile phone applications for example. Many types of fingerprint reorganization devices have been developed. Many of them first register the ridge patterns, and software extracts the coordinates and feature classes such as ridge ends and bifurcations (called minutiae). With software, the distortion can be corrected, but the image blur is difficult to remove. There is also a line of tiny pores on the ridges that is more difficult to solve, but can be used to provide more information for identification. United States Patent Application No. 2002/003892 to M Iwanaga provides a novel method for imaging fingerprints in the air for a cell phone. However, for a finger in the air, the peaks can be seen by the specular reflection of light from a localized source, but the image contrast is limited by the underlying scattering, and by the curvature at the end of the finger, so that it is not perfectly flat on the imaging surface. The rounded shape of the finger can cause unacceptable distortion of the image. On the contrary, when using the contact methods, the user flattens the tip of the finger against a surface (tactile platform); then the peaks and valleys can be distinguished by the differences in height between ridges and valleys. Identification using the contact method has been widely used. There are electronic sensors that measure the variation of capacitance, and optical detectors that see the finger pressed against a transparent plate or window. The optical contact detectors record changes in specular reflectance, imaged on a detector such as a CCD or CMOS detector array. The pixel size of the optical contact detector can go down to -5pm and the detector can be relatively small with a desired amount of pixels for sufficient resolution capability.

  Most fingerprint identification devices are light-field devices, which means that they produce a dark fingerprint peak pattern on a light background. To produce a fingerprint image with acceptable contrast, additional optical components are required to generate a uniformly clear background. Due to the additional optical components, it is difficult to manufacture a compact bright-field device.

  In U.S. Patent No. 5,900,993, issued May 4, 1999 and entitled Lens System for Use in Fingerprint Detection, Betensky discloses a lens system in which a first and a second lens in combination with a third cylindrical lens are used for the purpose. reduce optical distortion. However, an approach using cylindrical lenses requires additional components and inherently complicates the alignment of the lens system because a lack of symmetry causes the alignment process to fail by manipulating an additional degree of freedom in the placement. lenses. Seeing the needs of a compact low-volume fingerprint identification device, such as for a keyboard, Clark et al. further disclose a compact arrangement with a focal lens system and a dark background illumination or illumination in US Patent No. 6,643,390, issued in November 2003.

  Emergent consumer applications require an advanced compact fingerprint identification device, having an appropriate image quality with minimal distortion that can be adapted for use in a small compartment, such as a cell phone or mobile phone. Ultra-thin electronic device or personal effects, and which contains a minimal number of components to facilitate production.

  To overcome these drawbacks, the present invention aims at providing an improved compact fingerprint identification assembly for solving the above mentioned problems.

  The main objective of the present invention is to provide a fingerprint identification system using total reflection to identify the fingerprint pattern.

  In one aspect of the present invention, the fingerprint identification assembly has a body having a light source for emitting uniformly distributed light, an objective lens made of a transparent material such as glass or a resin acrylic and a first concave lens for receiving light reflected from the objective lens and transmitting reflected light to the outside and a detection device securely connected to the body and having a second concave lens corresponding to the first concave lens and a detector for detecting and receiving light from the second concave lens such as that due to differences in height between the peaks and valleys of a fingerprint, distinctive light areas are formed and the distinctions are transmitted to the first concave lens, the second concave lens and the detector for recognition identification.

  The present invention relates to a fingerprint identification assembly, characterized in that it comprises: - a body having an objective lens mounted on an upper part of the body for receiving thereon a fingertip and a first reflective lens mounted on a lower portion of the body for receiving light reflected from the objective lens; a light source emitting light to the first reflective lens; and a detection device formed integrally with the body and having a detector for receiving light reflected from the first reflective lens to compare the received reflected light with information stored inside the detector.

  The present invention also relates to a fingerprint identification assembly, characterized in that it comprises: a body having an objective lens mounted on an upper part of the body for receiving thereon a fingertip, a first reflective lens mounted on a lower portion of the body for receiving light reflected from the objective lens; a light source emitting light to the first reflective lens; and a detection device formed integrally with the body and having a second reflective lens for receiving light reflected from the first reflective lens and a detector for receiving light reflected by the second reflective lens to compare the reflected light received with information stored inside the detector.

  The objective lens is in particular made of a transparent material.

  The material for producing the objective lens is chosen in particular from glass and acrylic resins.

  The assembly according to the present invention may further comprise a diaphragm mounted at a junction between the body and the detection device, a rear face of the diaphragm being coated with a black paint.

  According to a particular embodiment, the first reflective lens and, if present, the second reflective lens are concave lenses.

  According to a particular embodiment, the position of the light source is shifted with respect to the location of the objective lens, the position of the objective lens is shifted with respect to the location of the first reflective lens and, if a second reflective lens is present, the position of the first reflective lens is offset from the location of the second reflective lens.

  The objective lens may be parallel to the ground surface or may be inclined relative to the ground surface.

  According to a particular embodiment, the objective lens has a width configured so that the fingerprint is stored in the detector only when the finger is moved back and forth.

  Other objects, advantages and novel features of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

On these drawings.

  Figure 1 is a schematic view showing a preferred embodiment of the present invention; Figure 2A is a schematic view of a different embodiment of the present invention; Figure 2B is a schematic view of yet another alternative embodiment of the embodiment shown in Figure 2A; Figure 2C is a schematic view showing a variant of the objective lens of the present invention; Figures 3A, 3B and 3C are schematic diagrams of the lens head in several preferred embodiments; Figure 4A is a preferred embodiment with an even number of reflective surfaces and Figure 4B is a preferred embodiment with an odd number of reflective surfaces; Figure 4C is a diagram in which Figures 4A and 4B are shown; Figure 5A is a ray interception diagram; Figures 5B and 5C are transfer function modulation (MTF) diagrams; Figure 5D is a distortion diagram for a preferred embodiment in which the prescription of the lens is presented in Table 1; Figure 6A is a ray interception diagram; Figure 6B is a distortion diagram for a preferred embodiment in which the lens prescription is shown in Table 2; Figure 7A is a ray interception diagram; Figure 7B is a distortion diagram for a preferred embodiment in which the lens prescription is shown in Table 3; and Figure 8 is a fingerprint imaging device with a light source.

  Using the contact method known in the prior art, the finger can be viewed or illuminated obliquely to increase the total internal reflection (TIR) contrast. Illumination with a light background or a dark background can be chosen. With bright field illumination, light is directed into the aperture of the diaphragm. If there is no contact, the light is reflected completely from the platen surface. When a finger is in contact, the TIR does not occur, and most of the light is scattered out of the viewing path, so that the peaks appear dark. In dark background illumination, the detector receives scattered light from the contact regions of the finger beyond the critical angle. When there is no contact, the finger is not visible from the detector. The ridges of the finger appear clear. Both illumination schemes can be adopted in the present invention. Essentially, the fingerprint pattern on the touchpad is virtually like a radiance object and the lens reduces the size of that source image, to fit the image sensor specification with the appropriate imaging performance .

  To reduce the size of the volume and acquire enough resolution, multiple reflective surfaces are used in the lens. Referring to Figure 1, in a preferred embodiment, the fingerprint illuminated by a light source (not shown) and re-illuminated at the detector by the multiple reflective surfaces successively from the first surface, the second surface and then on the image sensor. All reflective surfaces have a coating to prevent loss. Additional surfaces may be added between the second surface and the plane of the image as shown in Figure 2 in which two types of configurations can be seen. Figure 2A is a symmetrical configuration in which the reflective surfaces are of even number, while Figure 2B is an asymmetric configuration in which the number of reflective surfaces is odd. More reflective surfaces provide more degrees of freedom to improve imaging performance for the lens.

  In embodiments, the light source is adopted with 720 nm for a specific red LED, the size of the object is 10 mm. The imaging detector operates for f / # = - 3.5; the typical image size is a quarter of the size of the object or smaller. The thickness of the lens is generally less than 10 mm. The material of the lens is an acrylic material (Acryl). For an aspheric surface, the sag equation is described by: zz = cy + ADy4 + AEy6 + AFy8 + AGy10 1 + V1- (1 + K) c2y2 where c is the curvature of the surface (c = 1 / r, r is the radius of curvature), y is the radial distance to the axis, and k is the conic constant, AD, AE, AF, and AG are the fourth, sixth, eighth, and tenth order deformation coefficients.

  To illustrate the symmetrical embodiment, a lens prescription shown in Table 1 is included.

Table 1

  Surface Thickness Radius Comments bend (mm) (mm) Obj 0 7, 6 1 3, 597811 -7.6 Reflector 2 9,618052 10 Reflector Img 0 The radius interception diagram is shown in Figure 5A and the MTF across the entire object size at three different spatial frequencies (2 lp / mm, 6 lp / mm and 10 lp / mm) is shown in Figure 5B and 5C. The distortion effect is shown in Figure 5 (c) based on the illumination of the object.

  A different arrangement with a shorter lens size is described and the prescription of the lens is shown in Table 2.

Table 2

  Surface Thickness Radius Comments bend (mm) (mm) Obj 0 5.0 1 12, 285095 -5.0 Reflector 2 5,194983 3,704574 Reflector Img 0 The radius interception diagram is shown in Figure 6A and the distortion effect is shown in Figure 6B based on an illumination of an object.

  Additional refinement can be achieved by including an aspherical surface. A lens prescription shown in Table 3 is included.

Table 3

  Surface Thickness Radius Comments bend (mm) (mm) Obj 0 6,59 1 6, 10643 -6,59 Reflector 2 7,664650 6,6 Reflective Aspherical Coefficients: AD = -8,9864X10-3 AE = 2, 5227X10 -2 AF = -1.6825X10-2 Img 0 The ray interception diagram is shown in Figure 7A and the effect of distortion is shown in Figure 7B based on an illumination of an object.

  With the lens shown above, a fingerprint object may be on the touch platform and light from the source, for example an LED, will illuminate on the fingerprint. Due to the reflection, a scattered part will be reflected by the reflective surface and collected by the image detector.

  Referring again to FIG. 1, it may be noted that the fingerprint identification assembly according to the present invention comprises a body 6 having a light source 4 for emitting uniformly distributed light, a lens lens 11 mounted on a top of the body 6 and made of transparent material such as glass or an acrylic resin and a first concave lens 12 mounted on a lower face of the body 6 to receive reflected light from the objective lens 11 and transmitting the light reflected to the outside and a detection device 8 securely connected to the body 6 and having a second concave lens 14 corresponding to the first concave lens 12 and a detector 10 for detecting and receiving light from the second concave lens 14, so that because of the differences between the ridges and valleys of a fingerprint, areas of light say The pins are formed and the distinctions of the specific fingerprint are transmitted to the first concave lens 12, the second concave lens 14 and the detector 10 for identification recognition. From this application, it may be noted that the objective lens 11 is parallel to a surface of the ground. However, from the representation of Figure 2A, it may be noted that although the objective lens 11 is inclined with respect to the ground surface, the object of the present invention can still be achieved.

  It may be noted that additional lenses may be added to the structure of the present invention to increase the clarity of the fingerprint. In other words, the number of lenses used can be odd or even.

  From the description above, one can

  note that, when the light source 4 is activated, the light from the light source 4 moves in an effective reflection area 13 created by the first concave lens 12 and arrives at the objective lens 11.

  Due to the fact that a finger is placed on a top of the objective lens 11, different areas of light, for example light areas and dark areas, are formed because of the ridges and valleys of the fingerprint. As a result of the peaks and valleys, a distinctive reflection light is transmitted to the first concave lens 12 with a black coating on a bottom of the first concave lens 12 to prevent loss of light. A diaphragm 16 is formed between a seal between the body 6 and the detection device 8 to control the focusing of the reflected light from the first concave lens 12. In order to enhance the light focusing effect, a rear face diaphragm 16 is coated with black. Then, the light is reflected by the second concave lens 14 to the detector 10. Due to the fact that the reflection light path is arranged on the basis of the TIR, the distinctive light of the fingerprint is totally reflected at the Once by the first concave lens 12 and the second lens 14, and received by the detector 10, the detector 10 is able to compare the pattern of light received with what is stored inside the memory bank to distinguish the identity of the one to whom the fingerprint belongs.

  The location of the light source 4 is shifted with respect to the location of the objective lens 11 and the position of the first concave lens 12 is shifted with respect to the objective lens 11. In addition, the position of the second lens Concave 14 is offset from the location of the first concave lens 12. Thus, the TIR is accomplished successfully.

  It should be understood, however, that although many features and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and operation of the invention, the description is illustrative only, and changes may be made in detail, particularly with respect to the shape, size and arrangement of the parts within the principles of the invention to the fullest extent indicated by the broad meaning of the terms in which the claims annexed are expressed.

Claims (8)

  1 - Fingerprint identification assembly, characterized in that it comprises: a body (6) having an objective lens (11) mounted on an upper part of the body (6) for receiving thereon one end finger and a first reflective lens (12) mounted on a lower portion of the body (6) for receiving light reflected from the objective lens (11); a light source (4) emitting light towards the first reflective lens (12); and a detection device formed integrally with the body (6) and having a detector (10) for receiving the light reflected by the first reflective lens (12) to compare the received reflected light with information stored at the inside the detector (10).   2 - Fingerprint identification assembly, characterized in that it comprises: - a body (6) having an objective lens (11) mounted on an upper part of the body (6) to receive thereon a fingertip, a first reflective lens (12) mounted on a lower portion of the body (6) for receiving light reflected from the objective lens (11); a light source (4) emitting light to the first reflective lens (12); and a detection device formed integrally with the body (6) and having a second reflective lens (14) for receiving light reflected from the first reflective lens (12) and a detector (10) for receiving the reflected light by the second reflective lens (14) for comparing the received reflected light with information stored inside the detector (10).   3 - assembly according to one of claims 1 or 2, characterized in that the objective lens (11) 5 is made of a transparent material.   4 - assembly according to claim 3, characterized in that the material for manufacturing the objective lens is selected from glass and acrylic resins.   - Set according to one of claims 1 to   4, characterized in that it further comprises a diaphragm (16) mounted at a junction between the body (6) and the detection device, a rear face of the diaphragm (16) being coated with a black paint.   6 - assembly according to one of claims 1 to   5, characterized in that the first reflective lens (12) and, if present, the second reflective lens (14) are concave lenses.   7 - assembly according to one of claims 1 to   6, characterized in that the position of the light source (4) is shifted with respect to the location of the objective lens (11), the position of the objective lens (11) is shifted with respect to the location of the first reflective lens (12) and, if a second reflective lens (14) is present, the position of the first reflective lens (12) is shifted with respect to the location of the second reflective lens (14).   8 - assembly according to one of claims 1 to 7, characterized in that the objective lens (11) is parallel to the surface of the ground.   9 - assembly according to one of claims 1 to 7, characterized in that the objective lens (11) is inclined relative to the ground surface.   - Set according to one of claims 1 to   9, characterized in that the objective lens (11) has a width configured so that the fingerprint is stored in the detector (10) only when the finger is moved back and forth.