WO2013176573A1

WO2013176573A1 - Papillary ridge pattern registration system

Info

Publication number: WO2013176573A1
Application number: PCT/RU2013/000145
Authority: WO
Inventors: Сергеевич ПРЫТКОВАнтон
Original assignee: Общество С Ограниченной Ответственностью "Абилма"
Priority date: 2012-05-21
Filing date: 2013-02-22
Publication date: 2013-11-28
Also published as: RU2484524C1

Abstract

The invention relates to the field of biometrics. The technical result consists in decreasing the cost and increasing the reliability of a papillary ridge pattern registration system, while providing a high image quality, small overall dimensions, rapid operating speed and lower energy consumption. The system comprises a light source, an element defining the position of a reader surface, an optical system, a multi-element image receiver, an electronic memory, and a processing device, wherein the electronic output image of the system is linked through combination in the processing device with no fewer than two intermediary images of lower resolution being in turn linked to the optical image of the reader surface, the spectral composition of which differs for different intermediary images, and wherein the position of the elements of the optical image on the receiving surface of the image receiver is different for different spectral compositions of radiation.

Description

PAPILLARY PATTERN REGISTRATION SYSTEM

Technical field

The invention relates to the field of biometry, in particular to systems for automated registration of papillary patterns.

State of the art

A schematic diagram of a typical papillary pattern registration system is shown in FIG. 1. The light source 1 emits in the direction of the element 2, which sets the position of the reading surface 3 of the registered object, such as, for example, papillary lines of a finger or palm of a hand. On the reading surface, due to the difference in reflection from the areas corresponding to the depressions and protrusions of the papillary pattern, the light flux from the light source becomes the image carrier of this papillary pattern. An optical system, as a rule, including a collective 4, a system of mirrors 5, a lens 6, a protective glass 7 and microlenses 8 above the image receiver, receives this stream and forms an image of the papillary pattern on the photosensitive surface 9 of the multi-element image receiver. The image receiver converts the image from optical to electronic digital in the form of an array of intensity values proportional to the radiation flux incident on the corresponding photosensitive element and transfers it to electronic memory 10. Processing device 11 reduces the scale of this electronic image to standard, thereby forming the output image of the system.

An element that sets the position of the registered object is usually made in the form of an optically transparent isosceles rectangular prism. However, there are options for constructing a registration scheme for papillary patterns, in which the role of the element that sets the position of the reading surface is played by prisms of complex shape, cylindrical elements, plane-parallel plates. In more rare cases, the role of the element that sets the position of the reading surface is played by the housing element of the system.

The number of mirrors in an optical system can be different and determines the shape and overall dimensions of the system.

The radiation receiver, as a rule, is made in the form of a ruler or matrix based on metal-oxide-semiconductor transistors or charge-coupled devices.

A common drawback of these systems, due to extremely stringent requirements for image quality, is the need to use image receivers with relatively large sizes of photosensitive elements, which leads to significant overall dimensions of the working surface of the receivers and, as a result, the extremely high cost of systems built using them.

The reason for the significant price of large-area receivers is the high cost of the silicon wafers from which they are made, and the low percentage of use of the area of such wafers.

So in FIG. 2a shows the arrangement on a silicon wafer 12 with a diameter of 150 mm of crystals 13 of a typical image pickup system for recording a papillary palm pattern with a resolution of 1000 dpi. Such a receiver has a photosensitive element size of 6.8 micrometers and contains 7216 elements horizontally and 5412 vertically. From the figure it can be seen that only 4 such crystals are placed on the plate. In addition, in this case, the useful area of the plate used for the manufacture of crystals is only about 50% of its total area. If during manufacture only four critical manufacturing defects 14 are allowed, but located, for example, as shown in FIG. 2a, then no suitable crystal will be obtained from this plate.

If you build a receiver with the same amount photosensitive elements, but with a size of 1.4 micrometers, then the arrangement of crystals on the plate 15 with a diameter of 150 mm can be, for example, as shown in FIG. 26. In this case, 137 crystals 16 are placed on the plate, which already occupy 80% of the plate area. Moreover, if during production four critical manufacturing defects 17 are located, located in the same manner as shown in FIG. 2a, then 133 suitable crystals will be obtained from this plate. Thus, due to defects, the losses will amount to only 3% of the total number of crystals on the plate.

However, despite the obvious advantages, the use of receivers with small sizes of photosensitive elements in registration systems of papillary patterns is constrained by insufficient quality of the image formed, in particular, noise and charge spreading between the elements to comply with current biometric standards. The main such standard for papillary pattern registration systems is currently the FBI EBTS Appendix F.

There are few options for constructing registration systems for papillary patterns that realize the required resolution and size, reading areas when using relatively cheap image receivers.

So, in US patent 5859420 dated January 12, 1999 for IPC GO 1B 11/124, a system is shown in which the resolution of the registration system for papillary patterns is increased by dividing the system into several channels, each of which forms a separate image part of the registered object, after which the image parts are combined into the output image.

US Pat. No. 6,928,195 dated 08/08/2005 for IPC G06K9 / 32 shows a system that can increase the resolution of the registration system for papillary patterns without increasing the number of photosensitive elements of the image receiver by using a swinging mirror in the system to form several spatially spaced intermediate images and forming an output image in which the elements of the intermediate images alternate.

This system is the closest analogue of the invention. Its main drawback is the presence of additional elements and procedures that, although they allow the use of a relatively inexpensive receiver, however, they themselves make an additional contribution to the high cost of the system and reduce its reliability. As a result, a significant reduction in the total cost of the system is not achieved, but at the same time reliability is reduced, dimensions are increased, energy consumption is increased and system performance is reduced.

Object of the invention

The objective of the present invention is the implementation of the registration system of papillary patterns, which has low cost, high reliability and at the same time provides high image quality, small overall dimensions, high speed and low power consumption.

SUMMARY OF THE INVENTION

This problem is solved due to the fact that the registration system of papillary patterns contains a light source that forms the working radiation, an element that sets the position of the reading surface of the papillary pattern, an optical system that reads the image of this surface at an angle i to its normal, a multi-element image receiver, electronic memory for image storage and processing device, and in electronic memory the output image of the reading surface of the papillary pattern is electrically connected with at least two intermediate images of a resolution lower than the output, by combining, in the processing device, the intensity values between the elements of the intermediate images intersecting in different intermediate images the same image area of the reading surface of the papillary pattern, and each of the intermediate images it is connected electrically with the photosensitive elements of the image receiver, which are connected optically to the radiation source and the reading surface of the papillary pattern through the image of the reading surface of the papillary pattern formed by the optical system, the spectral composition of which is not the same in different intermediate images, and the position of the elements of the optical image on the receiving surface of the image receiver is not the same for of these various spectral compositions of radiation.

The image receiver is preferably monochromatic.

Intermediate images are preferably associated with the photosensitive elements of the image receiver through the normalization of histograms in the processing device in order to compensate for the mismatch between the histograms of the intermediate images due to differences in the light flux from the light source, reflection coefficient from the recorded object, transmission of the optical system and the sensitivity of the image receiver for different spectral radiation compositions.

Between the reading surface and the image receiver, the system preferably comprises a refractive surface that is asymmetrical with respect to the optical beam connecting the centers of the object and the image. In another embodiment, the part of the optical system that forms the actual image of the reading surface may have an increase in chromatism sufficient to effect the necessary mutual displacement of intermediate images of different spectral composition.

The spectral composition of the working radiation preferably lies in the range from 380 to 1200 nanometers.

The reading angle i preferably exceeds the angle of total internal reflection for the material of which the element is made, specifying the position of the reading surface.

The processing device, the image receiver and the light source are preferably electrically coupled to provide a synchronization of the reading period of the intermediate images with the radiation period of the desired spectral composition.

Result of invention

The technical result provided by the given set of features is to reduce cost, increase reliability, ensure high image quality, small overall dimensions, high speed and low power consumption of the papillary pattern registration system.

The implementation of the invention

An example embodiment of the invention can be shown based on the circuit shown in FIG. 3. A light source, which is a light panel 1, capable of emitting in two spectral ranges due to the use of two types of LEDs with dominant radiation wavelengths of 470 and 525 nanometers, alternately and synchronously with the flash pulses from a camera containing an image receiver, emits in one of these ranges in the direction of an isosceles rectangular prism 2 of optically transparent material. Having passed the input side of the prism 21, light enters at the angle of total internal reflection on the hypotenuse face 3, which defines the reading surface of the papillary pattern. A registered object, such as, for example, papillary lines of a finger or palm of a hand, is placed on this surface. In places corresponding to the protrusions of the papillary pattern, the luminous flux from the light source is partially absorbed by the registered object, in other zones it is completely reflected by the hypotenuse face of the prism. Thus, the luminous flux becomes the image carrier of the registered papillary pattern. Further, the light passes through the output cathete face 22 of the prism, plane-parallel the plate 30, the collective 4, is reflected on the mirror 5 and hits the lens 6. The lens forms an image of the recorded object on the photosensitive surface 9 of the monochromatic camera, built on a metal-oxide-semiconductor transistor matrix. Moreover, one photosensitive element accounts for 1.5 elements of the required resolution on the registered object, and the images for two emitted spectral ranges are mutually offset on the receiving surface by an amount corresponding to 0.5 of the size of the element of the required resolution. This displacement is achieved due to the dispersion on a plane-parallel plate 30, inclined with respect to the optical axis. Rays of different wavelengths are refracted on the surface 31 at different angles and, as a result, reach the surface 32 at different points. After refraction on surface 32, the rays of different wavelengths are mutually parallel and mutually offset. The elements of the optical system and the image receiver are rigidly mounted on a single housing. The camera generates a digital image of the recorded object in the form of an array of intensity values associated with the light flux incident on the corresponding photosensitive element, and transfers it via USB to the memory 10 of the computer with processor 11. Thus, two intermediate images are transmitted, and the first intermediate image is read camera during the emission of light with a dominant wavelength of 470 nm, and the second during the emission of light with a dominant wavelength of 525 nm. Further, the intensities of the elements of the second image are normalized by a computer program to ensure the mutual correspondence of the histograms of the first and second images. The deviation from this correspondence is caused by the difference in the luminous flux from the light source, the reflection coefficient from the recorded object, the transmission of the optical system and the sensitivity of the image receiver for different spectral compositions of the radiation. From the obtained two intermediate images, one output image is formed. For this computer program combines the values of the intensities of the elements crossing the same area in the image of the registered object. The principle of this combination for the image section is shown in FIG. 4. Suppose that two mutually shifted vertical images with dominant wavelengths of 470 and

525 nm, corresponding to zones B and C on the registered object, which coincide in the horizontal direction with zone A. Labels A1, B1, CI, A2,

B2, C2, etc., the elements of the registered object corresponding to the resolution elements of the corresponding image are indicated.

It is easy to see that the value of the intensity of the element B1 corresponds to the sum of the values of the intensity of the element A1 and 0.5 values of the intensity of the element

A2. In addition, the intensity value of element C1 corresponds to a sum of 0.5 of the intensity value of element A1 and the intensity value of element A2.

Those. we get a system of two equations with two unknowns:

A1 +0.5 A2 = B1

0.5 -A1 + A2 = C1 ^'

Solving this system, we obtain the intensities A1 and A2 of the output image:

_{A 1} _ B1 -0.5 C1

0.75

A2 = C1 -0.5 A1

Further, AZ = B2-0.5 A2.

In a similar way, intensity values for all elements of the output image can be calculated.

The applicant has made samples of papillary pattern scanners that implement the present invention. The experimental data confirmed that when combining mutually displaced images of different spectral composition, it is possible to build a papillary pattern registration system that meets the FBI EBTS Appendix F standard using an image receiver with a smaller than the number of elements of the output image, the number of photosensitive elements.

The use of a small photosensitive area has led to a relatively low cost of the image receiver and lower power consumption. The formation of the output image with increased resolution and the normalization of histograms of intermediate images made it possible to ensure high image quality. Also, due to the small size of the photosensitive surface, the focal length of the lens was significantly reduced compared to the closest analogue, which led to a decrease in the size of the system and the cost of the lens. There are no moving elements in the system, which leads to an increase, in comparison with the closest analogue, in the speed and reliability of the system.

Brief Description of the Drawings

The prior art and the invention is illustrated by drawings.

In FIG. 1 shows a typical construction scheme for the registration of papillary patterns.

In FIG. Figure 2 shows the location of the crystals of the image receiver with the number of light-sensitive elements 7216 horizontally and 5412 vertically on a plate with a diameter of 150 mm for various sizes of photosensitive elements. In FIG. 2a shows crystals with an element size of 6.8 micrometers, in FIG. 26 shows crystals with an element size of 1.4 micrometers.

In FIG. 3 shows a diagram of an implementation of a papillary pattern registration system built on a multi-band light source and using a combination of mutually offset intermediate images of different spectral composition to obtain a higher resolution output image.

In FIG. 4 shows a scheme for combining mutually offset intermediate images of different spectral composition to obtain a higher resolution output image.

Claims

Claim

1. The registration system of papillary patterns, containing a light source that generates working radiation, an element that sets the position of the reading surface of the papillary pattern, an optical system that reads the image of this surface at an angle i to its normal, a multi-element image receiver, an electronic memory for storing images, and a processing device characterized in that in electronic memory the output image of the reading surface of the papillary pattern is electrically connected to at least two intermediate images less than the output resolution through the combination in the processing device, the intensity values between the elements of the intermediate images intersecting in different intermediate images the same region of the image of the reading surface, and each of the intermediate images is connected electrically to the photosensitive elements of the image receiver, which are connected optically with a radiation source and a reading surface of a papillary pattern through an image formed on top of the optical system readings, and the reading angle i and the spectral composition of the working radiation provide a difference in the light flux in the reading direction for the protrusions and depressions of the papillary pattern, the spectral composition of the radiation is not the same in different intermediate images, and the position of the optical image elements on the receiving surface of the image receiver is not the same for these different spectral radiation compositions.

2. The system according to claim 1, characterized in that the image receiver is monochromatic.

3. The system according to claim 1, characterized in that the intermediate images are associated with the photosensitive elements of the image receiver through the normalization of the histograms in the processing device in order to compensate for the mutual inconsistency of the intermediate histograms images due to differences in the luminous flux from the light source, the reflection coefficient from the registered object, the transmission of the optical system and the sensitivity of the image receiver for various spectral compositions of radiation.

4. The system according to claim 1, characterized in that between the read surface and the image receiver, the system comprises a refractive surface that is asymmetric with respect to the optical beam connecting the centers of the object and the image.

5. The system according to claim 1, characterized in that the part of the optical system that forms the actual image of the read surface has an increase in chromatism sufficient to effect the necessary mutual displacement of intermediate images of different spectral composition.

6. The system according to claim 1, characterized in that the spectral composition of the working radiation lies in the range from 380 to 1200 nanometers.

7. The system according to claim 1, characterized in that the reading angle i exceeds the angle of total internal reflection for the material from which the element specifying the position of the reading surface is made.

8. The system according to claim 1, characterized in that the processing device, the image receiver and the light source are electrically coupled to ensure synchronization of the reading period of the intermediate images with the radiation period of the desired spectral composition.