RU2311678C2 - Device for registration of papillary pattern - Google Patents

Abstract

FIELD: engineering of devices for producing dactyloscopic maps, possible use in systems for biometric identification of personality.

SUBSTANCE: device contains, optically interconnected, light source, projection system and a system of photo-receiving elements, image processing block, electrically connected to system of photo-receiving elements, and a set of prisms, having finger positioning groove on the surface for perceiving fingerprints, where each prism is installed in rigid guiding elements, ensuring its possible movement along the groove axis independently from other prisms.

EFFECT: simplified design of device, expanded functional capabilities due to production of more complete picture of registration of papillary pattern of each finger.

3 cl, 1 dwg

Description

The inventive device relates to the field of optical imaging using computer technology, and more particularly to a device for fingerprint cards used in civilian and police biometric identification systems.

Known analogues of the claimed invention, for example, a device for photo-registration of patterns of papillary lines described in A.S. USSR No. 261737, IPC 7 А61В, 5/117, published January 13, 1970. The device includes a illuminator, a lens, a swivel mirror, a small screen, a swivel frosted glass, a remote screen, a camera and a working prism, the hypotenous face of which has a concave, for example cylindrical , shape. The disadvantage of the analogue is that it has a complex structure and allows you to get patterns of papillary lines of individual fingers, but does not allow you to get control prints (simultaneous fingerprint of four fingers - index, middle, ring and little fingers), which are required for law enforcement agencies.

A known optical device for acquiring fingerprint images described in US patent No. 4925300, IPC G06K 9/20 (published 05/15/1990), in which the image of the papillary pattern of the finger is formed on the surface of the conical prisms. The light from the source undergoes total internal reflection on the surface of the prism to which the finger is attached. In those places where the protrusions of the papillary pattern touch the surface of the prism, the condition of total internal reflection is violated and the light is scattered. The result is a contrast image of the fingerprint. This device has the same disadvantages as the previous counterpart.

Closest to the claimed device inherently is an optical system for fingerprinting, described in US patent No. 4792226, IPC G06K 9/24 (published December 20, 1988), containing a common prism with a flat surface for receiving control prints with simultaneous application four fingers and a system of individual prisms with grooves of different sizes to obtain individual fingerprints. This device is selected as a prototype. The disadvantage of the prototype is its complex design (the presence of a movable contact device connecting the system of individual finger prisms to the circuit for selecting images from a common prism or from a system of prisms) and large dimensions, since the device has both a common prism and a system of individual prisms. In addition, the prototype device does not allow to obtain papillary patterns located at the end of the distal phalanx of the finger (the skin area of the distal phalanx of the finger adjacent to the nail plate), which leads to the loss of information about the picture of the papillary pattern.

The problem solved by the invention is to simplify the design of the device, reducing its size and expanding functionality due to a more complete picture of the papillary pattern of each of the fingers.

This is achieved by the fact that each of the prisms is mounted in rigid guiding elements, making it possible to move independently of the other prisms along the axis of the groove. In addition, rigid guide elements are provided with resilient elements.

In addition, in each of the grooves in the area covering the end of the distal phalanx of the finger, the longitudinal generatrix of the surface of the groove has a curved shape.

The essence of the claimed technical solution is illustrated in the drawing (general view of the device) and in views A and B. The device contains an optically coupled light source 1, a prism 2 with input, output and fingerprint-bearing faces, a projection system 3 and a system of photodetector elements 4, electrically connected, for example, by cable 5 with processing unit 6 (computer). Prisms 2 are made with the possibility of independent movement (shown by arrow ↔) along the axes α, β, and γ of grooves 11. The figure shows an embodiment of a node for movable mounting of prisms. The prism 2 by means of rigid struts 15 is rigidly fixed on the plate 10, which can be moved in the grooves of the guide element 7, which is rigidly fixed on the base 9. On the base 9 is also fixed a pin 14 to which the elastic element 8 is attached, for example, a spring connecting the plate 10 with a pin 14 and ensuring the return of the plate 10 with the prism 2 fixed on it to its original position (to the pin 14 in the drawing) in the absence of external force from the side of the finger. On the fingerprint receiving face of the prism 2, grooves 11 are made, for example, of a cylindrical shape in which fingers 13 of the hand are positioned. Moreover, in each of the grooves 11, in the area covering the end of the distal phalanx of the finger, the longitudinal generatrix 12 (see drawing) of the groove surface has a curved shape, for example, as a part of a circle or parabola. This shape of the groove provides maximum coverage of the distal phalanx with the surface of the groove, and the movable mount of the prisms allows you to compensate for the difference in the lengths of the fingers in different people.

The device operates as follows.

The fingers 13 of the hand are placed in the grooves 11 of the prisms 2 in such a way as to provide the largest contact area of the skin of the fingers with the sensing surface of the grooves. The difference in the ratio of the lengths of the fingers in different people is compensated by the fact that the prisms 2 are mounted on the guiding elements, ensuring the movement of the prisms 2 along the axis of the groove 11. In the drawing, these are the axes α, β and γ. The drawing shows one embodiment of such a guide device.

Before registering the papillary pattern on the fingers of the hand, the longest finger is positioned so that its end abuts against the rise of the curved portion 12 of the groove 11. Then, the hand is moved forward, moving the corresponding prism until the groove is raised with the next finger along the length, and so on, until all registered fingers will not be located in the best way to register. If the device is made without a curved part 12 of the groove 11, then to stop the finger 13 at the end of the groove 11, an emphasis is made, for example, in the form of a plate perpendicular to the axis of the groove 11 (not shown). After that, the actual registration of the papillary pattern placed on the prisms 2 fingers 13, the principle of which is described below.

The light from source 1 enters into prism 2 through the input face (lower in the drawing) and through fingerprint surface 10 illuminates finger 13. Light is reflected and scattered by the skin in different directions, but only at the point of contact of the skin with glass can it return to the prism at angles exceeding the angle of total internal reflection for the material of the prism 2. The design of the prism ensures that this particular part of the scattered light hits the projection system 3, which forms a black-and-white picture on the photodetector system 4, with corresponding to the pattern of papillary lines on the finger 13. The system of photodetector elements 4 converts the black-and-white picture into an electrical signal, which through an electric connection 5 enters the processing unit (computer) 6 for further processing.

After removing the hand, the elastic elements 8 return the prism 2 to its original position and the device is ready to register the other hand.

Thus, the claimed device compared with the prototype allows you to get a more complete picture of the papillary pattern of the fingers, has a simple design and smaller dimensions. The applicant developed a prototype device and tested it, which showed the high quality of the images of papillary finger patterns and ease of use of the device. According to the applicant, the proposed device may be protected by a patent for an invention.

Claims (3)

1. A device for registering a papillary pattern, containing a set of prisms located between the light source and the projection system and optically coupled to them, sequentially located and optically connected to each other, the light source, the projection system and the photodetector system, electrically connected to the image processing unit, fingerprint faces of the prisms have a groove for accommodating a finger, characterized in that each of the prisms is mounted in rigid guide elements, ensuring which can move it independently of other prisms along the axis of the groove. 2. The device for registering a papillary pattern according to claim 1, characterized in that in each of the grooves in the area covering the end of the distal phalanx of the finger, the longitudinal generatrix of the surface of the groove has a curved shape. 3. The device for registering a papillary pattern according to claim 1, characterized in that the rigid guide elements are provided with elastic elements.