JP2007072942A - Fingerprint recognition assembly using reflection for recognizing fingerprint pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fingerprint recognition assembly using combination of reflection and transmission of light corresponding to fingerprint for recognizing fingerprint pattern. <P>SOLUTION: The fingerprint recognition assembly includes a laminated lens containing a first lens, a second lens, and a third lens integrated with the first lens and the second lens. The first lens, the second lens, and the third lens have their own dielectric films covering them respectively. At least one luminous object is placed at bottom of the laminated lens, and a sensor is placed under the laminated lens for receiving the fingerprint image on top of the laminated lens. The dielectric films on the laminated lens make the lights from at least one of the luminous objects partially reflected by the fingerprint on the laminated lens and partly transmits the second lens, and the third lens, so that the sensor can receive them. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fingerprint identification assembly, in particular a fingerprint having a first lens, a second lens, and a third lens fitted to, ie, integrated with, the first lens and the second lens. A focus of the fingerprint image sensed by a sensor of the fingerprint identification assembly by a combination of light reflection and transmission corresponding to a fingerprint pattern on the first lens of the fingerprint identification assembly And a fingerprint identification assembly.

  Fingerprint identification is probably one of the oldest and most established methods of identifying an individual. It belongs to the field of biometrics, i.e. identifying people by measuring and sensing parts of the body and is important for various applications. A number of automated techniques are currently in use or in development, including palmprint reading, finger pore reading, palm shape identification and iris, retina or face recognition. Of these, identity verification with fingerprints is fairly easy and is expected to be more widely accepted as it is a convenient and secure alternative to entered passwords, keys or signatures to access restricted areas or information. It is.

  Basically, the identification task involves the determination of the identification of an unknown person based on a fragment of the fingerprint pattern or the confirmation of the identification of a known person at a certain level based on a specific fingerprint pattern. For accurate identification of fingerprint features, it is desirable that it is universally necessary, that is, that different machines can recognize the features. On the other hand, in many situations, identification does not necessarily have to be universal and only requires clear resolution. Human fingertips have a unique pattern of curved ridges with a depth of about 0.1 mm and a period of about 0.5-1.0 mm. The finger tissue scatters red light with a diffuse reflectance of about 50%, and the finger refractive index is about 1.51. It is desirable to have as wide a field of view as possible with minimal distortion in order to give more features for identification and wider tolerance for finger placement errors due to the need for universal identification. On the other hand, the effective size of the fingerprint is about 10 mm in the contact table on which the fingerprint is identified, but the size of the system must be smaller than 10 mm in order to be applied to, for example, a mobile phone. Many types of fingerprint reorganization devices have been developed. They primarily record ridge patterns first, and then the software extracts the coordinates and types of features such as ridge edges and branches (called "minutiae"). Although distortion can be corrected by software, image blur is difficult to remove. Also, the ridges have a row of small pores that are more difficult to resolve but can be used to provide more detailed information for identification. M.M. US Patent Application No. 2002/003892 by Iwanaga proposed a new method for fingerprint imaging in the air for mobile phones. However, because the finger is in the air, the ridges can be seen by specular reflection of light from a local light source, but the image contrast is a potential because the finger is not in full contact with the imaging surface. Limited by scattering and finger tilt. The rounded shape of the fingers can cause unacceptable distortion. In contrast, when using the contact method, the user can fit the fingertips to the surface of the contact table, and ridges and valleys can be distinguished by their height difference. Identification using contact methods is widely used. There are electronic sensors that measure changes in capacitance, and optical sensors that look at a finger pressed against a transparent platen or window. Optical contact sensors record changes in the specular reflectivity of sensors such as CCD and CMOS sensor arrays. The pixel size of the photocontact sensor can be as small as 5 microns, and the photocontact sensor can be made quite small with an appropriate number of pixels for sufficient resolution capability.

Most fingerprint identification devices are bright field devices. That is, they produce a dark fingerprint ridge pattern on a light background. In order to produce a fingerprint image with acceptable contrast, additional optics are required to create a uniform bright background. Since additional optical components are required, it is difficult to make a small bright field device. Patent Document 1 relating to the invention by Betensky, whose name is “Lens System Used for Fingerprint Sensing”, which was patented on May 4, 1999, is that the first and second lenses combined with the third cylindrical lens are The lens system used to reduce optical distortion is described. However, the method of using a cylindrical lens requires additional parts, and since it is not symmetric, a problem arises in the adjustment process that handles the extra degree of freedom of the lens arrangement, which essentially complicates the adjustment of the lens system. In view of the need for a small fingerprint identification device such as that for a keyboard, Clark et al., In US Pat. An identification device is shown.
US Patent No. 5,900,993 US Pat. No. 6,643,390

  What is needed for new applications in consumer equipment is a small compartment such as a cell phone, ultra-thin electronic device or personal belongings with adequate imaging performance with minimal distortion. It is a small fingerprint identification device that can be adapted for use in and that includes a minimum number of parts to facilitate production.

What is very difficult for a small fingerprint imaging device is that the system must be quite small, but the size of the object and the size of the sensor are not at all small. In other words, the effective field of view increases in both image space and object space. One way to eliminate this difficulty in lens design is to utilize a partially reflective system so that the total effective optical path length can be increased. Such a system was invented in 1997 under the name of a concentric optical system by Togino et al. For use as an imaging optical system or an eyepiece optical system (see Patent Document 3). Togino et al. Have shown that a concentric optical system is capable of clear imaging with virtually no chromatic aberration at viewing angles up to about 90 ° and pupil diameters up to about 10 mm. However, unlike Togino's claim that an object is far from the lens or infinitely away from the lens, the fingerprint imaging device requires a finite-conjugate system configuration. And
US Pat. No. 5,644,436

  The present invention provides an improved and compact fingerprint identification assembly to overcome the above disadvantages.

  A principal object of the present invention is to provide a fingerprint identification assembly that uses a combination of light reflection and transmission corresponding to a fingerprint to identify a fingerprint pattern.

  In one aspect of the present invention, the fingerprint identification assembly includes a first lens, a second lens, and a third lens integrated with the first lens and the second lens. . In addition, at least one light source is located under the laminated lens for projecting light onto the laminated lens, and a sensor is provided under the laminated lens for receiving a reflected fingerprint image.

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

  Embodiments 1 to 3 of the concentric optical system according to the present invention will be described below with reference to the drawings. The height of the working object is 6 mm, so the object size is 12 mm. The F number is 3.5. The wavelength of the light source of the light emitter is 720 nm.

  A first embodiment of the present invention will be described below with reference to FIG. The lens head is formed of two different materials, the first material is a plastic material (acrylic) and the second material is glass (BK7). Table 1 shows lens specifications. In this embodiment, the lens surfaces are all spherical. 6, 7A, 7B, 8A, and 8B show the aberration, MTF, distortion, and spot diagram of this example, respectively.

  A second embodiment of the present invention will be described below with reference to FIG. The lens head is formed of two different materials, the first material is a plastic material (acrylic) and the second material is glass (BK7). Table 2 shows lens specifications. The total thickness of the lens of this example is reduced to within 10 mm. In this embodiment, the lens surfaces are all spherical. 10, 11A, 11B, 12A, and 12B show the aberration, MTF, distortion, and spot diagram of this example, respectively.

  A third embodiment of the present invention will be described below with reference to FIG. The lens head is formed of two different materials, the first material is a plastic material (acrylic) and the second material is glass (BK7). Table 3 shows lens specifications. The total thickness of the lens of this example is reduced to within 10 mm. In this embodiment, the second surface of the lens is aspheric. The non-surface sag equation is shown below.

  Where c is the curvature of the surface (c = 1 / r, r is the radius of curvature), y is the radial distance from the axis, k is the conic constant, and AD, AE, AF and AG are , Fourth order, sixth order, eighth order and tenth order deformation coefficients. 14, 15A, 15B, 16A, and 16B show the aberration, MTF, distortion, and spot diagram of this example, respectively. In this embodiment, the aspheric coefficients of the lens surfaces 1 and 3 are AD = −0.004813, AE = 0.003481, and AF = + 9.698 × 10−5. The conic constant k and the aspheric coefficient AG are zero.

  FIG. 5 shows a preferred embodiment of the lens head. FIG. 6 shows typical aberration properties of the lens head shown in FIG. 7A and 7B show the typical MTF performance of the lens head shown in FIG. 8A and 8B show distortion and spot diagrams of the lens head shown in FIG. FIG. 9 shows a preferred embodiment of the lens head. FIG. 10 shows typical aberration properties of the lens head shown in FIG. 11A and 11B show typical MTF performance of the lens head shown in FIG. 12A and 12B show distortion and spot diagrams of the lens head shown in FIG. FIG. 13 shows a preferred embodiment of the lens head. FIG. 14 shows typical aberration properties of the lens head shown in FIG. 15A and 15B show typical MTF performance of the lens head shown in FIG. 16A and 16B show distortion and spot diagrams of the lens head shown in FIG.

  Referring to FIG. 1, the fingerprint identification assembly according to the present invention includes a laminated lens 2, at least one light emitter 3 and a sensor 4.

  The present invention uses light from at least one light emitter 3 to reveal a fingerprint image on top of the laminated lens 2. Due to the structure of the laminated lens 2, the light from the at least one light emitter 3 is partially reflected and partially reflected so that an image of the fingerprint on the upper side of the laminated lens 2 can be clearly shown to the sensor 4. Transparent.

  Referring to FIG. 2, the first embodiment of the present invention is shown, and the laminated lens 2 is integrated with the first lens 21, the second lens 23, the first lens 21 and the second lens 23. The third lens 24 is formed. Preferably, two light emitters 3 are provided below the laminated lens 2, and the sensor 4 is positioned under the laminated lens 2. Preferably, the first lens 21, the second lens 23 and the third lens 24 are made of glass, plastic or a combination of glass and plastic. Further, the first lens 21, the second lens 23, and the first lens 21 are so reflected that the light from the at least one light emitter 3 is partially reflected and partially transmitted through the second lens 23 and the third lens 24. A metal film or a dielectric film is applied to each of the three lenses 24.

  When the fingerprint identification assembly according to the present invention is used, light from at least one light emitter 3 is projected onto the first lens 21. Thereafter, a first reflected light beam b 1 and a first transmitted light beam b 2 passing through the second lens 23 are generated according to the waveform pattern of the fingerprint on the first lens 21. The first transmitted light b2 is reflected by the third lens 24 so as to generate a second reflected light b3 to the second lens 23. The second reflected light beam b3 is reflected by the second lens 23 and then changed to the third reflected light beam b4. The third reflected light beam b4 is projected through the third lens 24 to generate the last light beam b5 sensed by the sensor 4. Therefore, the path of light from at least one light emitter 3 is b1 → b2 → b3 → b4 → b5 → image. Preferably, the laminated lens 2 of the present invention has a thickness limit of 15 mm so that the path of light from at least one light emitter 3 is lengthened and thereby the angle of incidence on the sensor 4 is reduced. Thus, the entire fingerprint identification assembly of the present invention is compact.

  Referring to FIG. 3, the illustrated embodiment has substantially the same structure as that shown in FIG. The only difference between the two is that the first lens 21 'has a flat upper surface.

  Referring to FIG. 4, the illustrated embodiment has substantially the same structure as that shown in FIG. The only difference between the two is that the first lens 21 "has a concave top surface.

  Although many features and advantages of the present invention have been set forth above along with details of the structure and function of the invention, the disclosure is illustrative only and is in accordance with the general broad meaning of the terms expressed in the claims. Obviously, changes may be made in details, particularly with respect to shape, size and arrangement of parts, within the scope of the disclosed principles of the invention.

The side view which shows that the finger | toe is placed on the upper part of the lamination lens of the fingerprint identification assembly which concerns on this invention. Schematic showing the path of light from a light source that focuses a fingerprint image as received by a sensor. Schematic which shows the different application of the laminated lens which concerns on this invention. Schematic which shows the further different application of the laminated lens which concerns on this invention. The side view of the lens head concerning the present invention. FIG. 6 is a diagram illustrating typical aberration characteristics of the lens head illustrated in FIG. 5. FIG. 6 is a diagram showing a typical MTF performance of the lens head shown in FIG. 5. FIG. 6 is a diagram showing a typical MTF performance of the lens head shown in FIG. 5. FIG. 6 is a diagram showing distortion of the lens head shown in FIG. 5. FIG. 6 is a diagram showing a spot diagram of the lens head shown in FIG. 5. Table 2 is a side view of a preferred embodiment of a lens head whose lens specifications are shown in Table 2. FIG. 10 is a diagram illustrating typical aberration characteristics of the lens head illustrated in FIG. 9. The figure which shows the performance of typical MTF of the lens head shown in FIG. The figure which shows the performance of typical MTF of the lens head shown in FIG. FIG. 10 is a diagram showing distortion of the lens head shown in FIG. 9. The figure which shows the spot diagram of the lens head shown in FIG. FIG. 3 is a side view of a preferred embodiment of a lens head whose lens specifications are shown in Table 3. FIG. 14 is a diagram illustrating typical aberration properties of the lens head illustrated in FIG. 13. FIG. 14 is a diagram showing typical MTF performance of the lens head shown in FIG. 13. FIG. 14 is a diagram showing typical MTF performance of the lens head shown in FIG. 13. FIG. 14 is a diagram showing distortion of the lens head shown in FIG. 13. The figure which shows the spot diagram of the lens head shown in FIG.

Explanation of symbols

2 Laminated lens 3 Luminescent body 4 Sensor 21, 21 ', 21 "1st lens 23 2nd lens 24 3rd lens

Claims (3)

  A laminated lens having a first lens, a second lens, the first lens, and a third lens integrated with the second lens, and at least one light emitter located below the laminated lens; A sensor located under the laminated lens to receive an image of a fingerprint on the laminated lens, wherein each of the first lens, the second lens, and the third lens covers it The second lens and the thin lens of the laminated lens so that light from the at least one light emitter is partially reflected by a fingerprint on the laminated lens and received by the sensor. A fingerprint identification assembly partially transmissive through the third lens.   The fingerprint identification assembly of claim 1, wherein the first lens has a flat top surface. The fingerprint identification assembly of claim 1, wherein the first lens has a concave top surface.

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