JP2706143B2 - Fingerprint matching method and device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint collation method for collating fingerprints and a device thereof. More particularly, the present invention relates to an apparatus for recording a reflection hologram of fingerprint data, or a method and apparatus for optically filtering input fingerprint data using a hologram to form a correlation signal.

Today, you can use a credit card or bank card to buy goods and services, or use a cash service machine (Au
Withdrawing cash from tomatic teller machines (ATMs) has become commonplace. In North America, more than 900 million credit and debit cards made of plastic magnetic strips are currently used, but there are no reliable ways to verify that a card user is a legitimate user. Does not exist. When using an ATM, the personal identification number (PIN) and the signature that the user puts on the invoice are not reliable proofs, and they cannot be reliably verified. Signatures can be forged and PINs can be obtained by illicit means.

The US credit card industry traded approximately $ 350 billion in credit in 1986, of which fraud losses amounted to approximately $ 750 million. It is also well known that state police have been vigorously working to end intra-organizational plots that span thousands of credit card users and across continents. It is where you are. What this means is that the credit cards used today are not only insecure, but can also be the target of large-scale criminal activity in which prevention measures are difficult to find.

Along with an ID card incorporating a photograph of a legitimate user,
Using a credit card is one solution to this problem, and this method may be used with a passport, but this method does not guarantee a secure match. This is because the reliability of such a method depends on the human factor of the autopsy service. For example,
The method of visually confirming the identity of an individual by using a photo of an ID card can prevent the coroner from performing reliably due to stress and fatigue, and can be obstructed from the outside, or simply confirm the identity. This is because certainty is also impaired by the large number of people to be done. In addition, the appearance of a person can be changed to resemble a photo attached to an ID card, and the ID card can be pressed using a photo of an unauthorized user.

Until now, signatures, PINs and photographs have been used, albeit incompletely, as a means of identifying card users. It has also been said that fraudulent cards will cost businesses in North America more than $ 1 billion next year.

As the damage caused by unauthorized use of the card increases, the use of a fingerprint as a collation means has been studied. This is because fingerprints are different for each individual and thus provide a reliable means of identity verification.

As a matching method using a fingerprint, an optical processing method using a holographic matched filter is a main and advanced method. This optical method differs fundamentally from the digital method in that the reference information is processed in the plane of the Fourier transform normally formed by the lens, rather than in the plane of the image. In this method, the “live” fingerprint is subjected to Fourier exchange, and the fingerprint after the Fourier exchange is superimposed on a Fourier-transformed reference fingerprint to perform collation. In this method, two sets of fingerprint patterns are compared, and if they match, the result is output as a focused beam of light. This method is a real-time parallel processing method, in which a single collation can be performed within approximately one second (the time from when a fingerprint is placed on a reading lens until a match or mismatch result is obtained).

If an optical processing method is used, it is theoretically possible to perform more accurate matching. The fingerprint pattern is
It breaks or is damaged due to abrasion by cuts, abrasions, or contaminants. Abrasion of the fingerprint will provide "noise" to the comparison device, and if not compensated correctly, the verification results can be falsely matched or falsely mismatched. Attempting to compensate for "fingerprint noise" by a real-time digital method not only requires complicated processes but also incurs great expense. This is because an algorithm that uses serial processing must be used. However, in the frequency conversion, "fingerprint noise" is removed accompanying the comparison method. Since the comparison is performed using a holographically matched filter, all spatial frequencies outside the band of the reference fingerprint are removed by the matched filter. And this is
The main part of the "noise" frequency range. In addition, the use of appropriate high-pass spatial filters removes unwanted low frequencies and DC bias, resulting in correlation accuracy.
racy) can be improved. As described above, when the optical processing method is used, the degree of collation increases both when the comparison results match and when they do not match.

Several proposals have already been made for fingerprint matching methods using Fourier transform holograms and optical correlation methods. However, in terms of practical use, there are problems related to the production of equipment for implementation. Has not produced as much results. The fingerprint matching devices developed so far are not only complicated and expensive, but also lack reliability.
This was an obstacle to widespread commercialization.

Already, some points to be improved have been pointed out in the above method. In particular, there is a problem in that an error in the collation result occurs with a considerable probability in an actual use situation. For example, if there is a displacement in the rotation direction or a change in size between the image and the hologram, the collation results will not match. Such an error in the verification result occurs even if the finger placed on the verification device is slightly rotated, and there is an optical mismatch between the device for recording the hologram and the device for confirming the identity of the card user. Even if there is. Even when the user's finger comes off or the user becomes obese and the fingerprint of the user becomes large, a change in size occurs between the image and the hologram. Even if the “live” fingerprint pattern and the reference fingerprint pattern are only shifted by 3.5 degrees in the direction of rotation, or the magnitudes of both are changed by only 2%, the signal-to-noise ratio of the matching device is
Reduce to 1/500.

Furthermore, in the conventional apparatus, the coherent light source (coherent light source) is used in both the fingerprint data recording step and the collation step, which not only increases the manufacturing cost of the apparatus but also complicates the structure of the apparatus. I was

Another problem is related to sensitivity. Optical devices must have positional stability in order to maintain a high signal-to-noise ratio. Serious malfunctions may occur.

The other problem is that the correlation signal (correlation
signal). This troubling problem has already been discussed in U.S. Pat. No. 3,781,113, issued to Thomas on Dec. 25, 1973, and also on Dec. 5, 1972.
U.S. Patent 3,704,949 granted to Thomas et al.
Reference. In both of these patents, a motorized mesh is used to chop the light to distinguish between focused (correlated) light and unfocused (decorrelated) light.

By the way, it has been found that one or more problems related to the prior art as described above can be effectively overcome by the fingerprint matching device configured as follows. The apparatus comprises a non-interfering light source for irradiating an irradiating beam along a beam path, and at least one fingerprint or fingerprint record of an individual placed on said beam path, wherein said fingerprint or fingerprint record is received. Input means comprising means for emitting along the optical information beam path an optical information beam modulated by data obtained from a fingerprint record; and an optical information beam placed on said optical information beam path and producing a Fourier-transformed optical information beam on the conversion surface. An optical Fourier transforming means, and a supporting means for supporting, on the conversion surface, a reference data record comprising a prerecorded reflection hologram of at least one reference fingerprint (the reflection hologram reflects and filters a Fourier-transformed optical information beam). Glow,
Emits light having an intensity distribution representing the degree of correlation between the reflection hologram and the optical information beam), and when the previously recorded reflection hologram is irradiated with the Fourier-transformed optical information beam, A verification result display means that operates in accordance with the intensity distribution of the reflected light.

Reflection holograms allow the use of incoherent white light sources. White light sources are less expensive and have lower sensitivity than coherent light sources such as lasers.

The device of the present invention is preferably configured such that when the user inserts two adjacent fingers into the finger position indicating device constituted by the movable guide portion, the collation process is started. The finger position pointing device is arranged so that the fingerprint of the legitimate user is placed directly and without rotation on the reading prism. This finger position pointing device constitutes another collation means. This is because if an unauthorized user inserts a finger into this finger position indicating device, the finger cannot be placed at the correct position because the position and width of the finger are different.

Also, the hologram should be at a multiplexed frequency to minimize errors due to size changes.

The invention also provides: a) irradiating a beam of incoherent light onto an input means on which at least one fingerprint is located to generate a fingerprint data beam; b) passing the fingerprint data beam to an optical Fourier transform means C) filtering the Fourier transform of the fingerprint data beam by means of a Fourier transform pre-recorded reflection hologram of at least one reference fingerprint, the Fourier transform of the fingerprint beam and the pre-recorded reflection hologram. Generating reflected light having an intensity distribution indicative of a degree of correlation with the at least one fingerprint and the at least one reference fingerprint according to the intensity distribution of light reflected from the reflection hologram. Another object of the present invention is to provide an optical fingerprint collation method comprising the steps of indicating a mismatch.

Further, the present invention is a reference data recording / creating device used together with a fingerprint collating device, comprising: a coherent light source that irradiates an irradiation beam along a beam path and a reference beam along a reference beam path; Means for receiving at least one fingerprint or fingerprint record of a placed individual and generating, along the optical information beam path, an optical information beam modulated by said at least one fingerprint or data obtained from the fingerprint record. The present invention provides a reference data recording / creating apparatus comprising: an input unit; and an optical Fourier transform unit that is placed in the optical information beam path and generates Fourier-transformed optical information on a conversion surface.

 Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an apparatus for encoding fingerprint information. This device comprises an encoding device 28 and a card 20. The card 20 may be a credit card or a passport. The coding device 28 comprises a coherent, variable wavelength light source 1 which comprises an attenuator 2
The light beam is sent to the variable beam splitter 4 via the shutter 3 and the shutter 3. This beam splitter 4 splits a light beam into two beams 22 and 23. The beam 22 passes through the objective lens 5, the pinhole spatial filter 6, and the collimating lens 7 and enters the prism 10. Prism 10 has a refractive index such that beam 22 is completely reflected when surface 24 of prism 10 is in contact with air.

Surface 24 is located at the front focal plane of lens 11. The spatial nozzle filter 17 is located on the rear focal plane of the lens 11. The reflected beam 22a passes through the lens 11, the spatial noise filter 17, and the collimating lens 18 and strikes the device 25, producing a reflection hologram on the recording medium 27 of the card 20. Card 20 is an encoding device
It is preliminarily inserted into the supporting means 29 of 28.

The beam 23 is reflected by the mirrors 12 and 13, passes through the objective lens 14, the pinhole spatial filter 15, and the collimating lens 16, and reaches the other side of the recording medium 27. At this time, the beam 23 forms an angle 26 with the beam 22a.

The device is configured such that the total travel distance of the two beams is equal.

The finger position indicator, which indicates the position of the finger, comprises a guide 8 located on the surface 24 of the prism. The position of the guide 8 is selectively converted to an analog electric signal, which is sent to an A / D converter 9. The output digital signal is sent to the magnetic piece 21 of the card 20 through the electric lead wire 19. This finger position indicator will be described in detail below with reference to FIGS. 3A and 3B.

Next, the operation of the encoding apparatus will be described. When a legitimate user puts two adjacent fingers on the reading prism 10 correctly, the position of the guide part 8 is determined, and around the three sides of the finger in consideration of the difference in finger length. The sliding fit is fixed. The analog position signal sent from the guide unit 8 is
The signal is converted into a digital signal by the A / D converter 9 and sent to the card 20 via the electric lead wire 19, where it is stored in the magnetic piece 21 (or semiconductor memory) of the card.

Next, one wavelength is selected for light source 1 and this light source is activated. The shutter 3 is opened so that the beam emitted from the light source 1 is split into two by the variable beam splitter 4. In order to remove noise, objective lenses 5 and 14 and pinhole spatial shutter 6
15 are used for each beam path. The collimating lenses 7, 16 through which each beam passes generate a very uniform plane wave with a spatial intensity change of 5% or less.

The beam 22 then reaches the prism 10. The refractive index of the prism is set such that the critical condition for total reflection is exactly satisfied at the surface 24 for the combination of glass and air. Therefore, the condition of total reflection largely depends on the refractive index of the medium adjacent to the surface 24. For this reason, when a legal user's finger is pressed against the prism surface 24 operating in the boundary region of the limit reflectance, the total reflection condition is broken at the place where the peak of the fingerprint touches. However, at the location facing the fingerprint valley, face 24
The total reflection condition is maintained because there is an interval between. As a result, the reflected beam 22a forms an information signal representing a legitimate user's fingerprint pattern.
Since the prism face 24 is located at the front focal plane of the lens 11 and the spatial nozzle filter 17 is located at the rear focal plane of the same lens, a spatial Fourier transform of the beam 22a is formed on the filter 17.

The filter 17 removes spatial frequency components above and below the human fingerprint pattern range and unnecessary low frequency components. This partially eliminates "fingerprint noise" due to cuts, abrasions, and contaminants.
A collimating lens 18 is located behind the filter 17 to maintain the focus of the spatial exchange. Card 20
The device 25, which produces a reflection hologram on the surface, allows the Fourier space exchange of the fingerprint
Recorded at 26. This process is performed step-by-step over a series of wavelengths β (1)... Β (n) that are appropriately selected to minimize errors due to size changes. (When β (1)> β (n)), β (1)
The change in magnitude up to / β (n) is β (1) and β (n)
If both are within the range of the spectrum of the white light source 31 (FIG. 2), it is surely compensated. In each step, the recording medium 27 mounted on a flexible substrate is formed by a step-and-repeat method using a holographic camera.
Exposure to interference patterns. At the end of the last step, the recording medium is an encoding plate which is a frequency multiplexed Fourier transform reflection hologram. The coding plate is then glued or sandwiched between the cards. Angle 26 is a function of the optical resolution of the reflection hologram processing method. As the resolution decreases, so does the angle 26.
However, this angle 26 must be large enough to angularly separate the "corss-correlation" signal 50b from other optical signals in the fingerprint comparison device of FIG.

The coding plate and the information stored on the finger width and the relative position of the finger stored therein form a reference data record.

FIG. 2 shows an apparatus for comparing a reference data record with an actual fingerprint. This device comprises a comparison device 30 and a card 20. The device 30 also provides a beam of light,
A non-coherent white light source 31 that is directed to a reading prism 35 via an objective lens 32, a pinhole spatial filter 33, a collimating lens 34, and a diffraction grating 37 is provided. The reading prism 35 has a refractive index such that the beam 50 is totally reflected while the prism surface 48 is in contact with air. The prism 35 is located on the front focal plane of the lens 36. The reflected beam 50a passes through the lens 36 and reaches the encoding plate 38 on the card 20. The position of the card 20 is determined by the positioning means 44 on the rear focal plane of the lens 36. Beam 50a is angle 49 (angle 26 in FIG. 1).
) And reflected from the encoding plate 38, through an image lens 39, and through a matrix optical threshold analyzer (matr
ix photo-threshold analyzer) The optical threshold analyzer 40 is electrically connected to a light 45.

The reader 42 made of a magnetic piece is located close to the magnetic piece 21 of the card 20. This reader 42 is electrically
Connected to A converter 47. A lead wire 46 extending from the D / A converter is connected to a series of motors and gears indicated by reference numeral 43. These motors and gears 43
The mechanical finger position guide 41 is connected to each other. The guide 41 constitutes a part of the finger position indicator shown in FIG.

In actual operation, first, the card 20 is positioned by the positioning means 44.
Insert Next, the position information for the guide section 41 is read from the card 20, and the guide section 41 is positioned at an appropriate position. That is, information recorded on the magnetic piece 21 of the card 20 is read by a reader 42, and this digital information is passed through a D / A converter 47, an electric lead wire 46, a series of motors and gears 43, Used to determine 41 locations.

Next, the user places an appropriate finger on the surface of the reading prism 35.
It is placed on the guide 41 so as to be in contact with 48. The incoherent white light source 31 is activated, and the beam 50 emitted from this light source is
The light passes through an objective lens 32 and a pinhole spatial filter 33. The noise of the beam 50 is filtered by the pinhole spatial filter 33.
To be removed. Subsequently, the beam 50 is collimated by the lens 34 and reaches the prism 35 through the two-dimensional diffraction grating 37. As with the prism 10 of FIG. 1, the refractive index of the prism 35 is set such that the reflected beam 50 is an information signal representing the fingerprint pattern of the user. Since the face 48 of the prism 35 is located at the front focal plane of the lens 36, a Fourier transform of the beam 50a is formed at the rear focal plane of the lens 36 at which the encoding plate 38, which is a reflection hologram, is located. Prism 35
By measuring the degree of correlation between the fingerprint placed on the surface 48 and the reference fingerprint encoded by holography, comparison / collation of fingerprints is performed. Since the Fourier transform reflection hologram is a filter matched to the legitimate user's fingerprint, the beam 50a (this beam is
Is reflected from the hologram of the encoding plate 38 of the card 20, the degree of correlation between the two can be obtained. In the conversion area, such a degree of correlation is obtained by reflecting the Fourier transform of the fingerprint of the finger placed on the prism 35 to the hologram on the card.
It is obtained naturally. Reflected beam 50b
Is then passed through an image lens 39 to a matrix optical threshold analyzer 40. If the user's fingerprint matches the hologram reference fingerprint, an in-focus bright light spot appears on the matrix optical threshold analyzer 40. On the other hand, if the two do not match, a point of light appears in the analyzer 40 in a diffused state. When the degree of the crosscorrelation exceeds a predetermined value, it is confirmed that the user of the card is a legal user. The success of this confirmation is indicated by the lighting of the light 45.

The comparison device 30 may be made by injection molding in order to fix all optical members that may be subject to movement or vibration in a single mold. Also, the use of a mold maintains the optical consistency of all comparison devices, thus reducing the possibility of fingerprint size changes between the encoding device and the comparison device.

3A and 3B show a guide portion of the finger position indicator.
This indicator is used for both the encoding device of FIG. 1 and the comparing device of FIG. Two adjacent fingers 51 are in direct contact with a rigid guide 55.
While these fingers are in contact with the support portion 57 that is slightly inclined,
It is located above the “read” prism 56. Next, in the encoding device, the finger length guides 52 and 53 move to come into close contact with the tips of the fingers. The finger width guide 54 subsequently moves to make a tight contact with the right side of the finger at the right end. Then, such position information is sent to and recorded on the magnetic piece 21 of the card 20 placed in the encoding device. On the other hand, in the case of the comparison device, the information read from the magnetic piece 21 of
Prior to placing 51, it is used to position guides 52, 53, 54.

Next, the reason why the finger position indicator can improve the matching accuracy will be described. In principle, no fingerprint matching device can prevent some errors from occurring. For example, when trying to confirm the identity of the card user with one fingerprint, if the resolution of the device cannot distinguish between two similar fingerprints of another person, a match is required to indicate that the two match. There is a danger of processing signals incorrectly. By the way, if two fingerprints are used, the possibility of outputting a false match signal is reduced, but as long as the limit value is the same, the probability of outputting a false mismatch signal increases. Although lowering the threshold value can lower the output probability of such a false mismatch signal,
Unless we introduce another comparison parameter, we will again increase the output probability of the false match signal,
As a result, there is no point in using two fingerprints.

By the way, the shape of a finger can be said to be almost unique to each individual, and differs from person to person. Therefore, if the shape of the finger is used as a comparison parameter in addition to the two fingerprints, not only can the matching accuracy be improved, but also the limit value relating to the degree of correlation of the fingerprint can be reduced to reduce the output probability of a false mismatch signal. it can. For example, let P (a) be the probability that two humans have similar fingerprints within a predetermined limit, and that two humans hold two adjacent fingers with similar shapes. Assuming that there is a probability of P (a), the probability that two humans have a similar fingerprint and a similar finger shape is the product P (a) * P (b) of P (a) and P (b). Become. That is, the probability that they are similar is reduced by at least one digit. As described above, in the case where two persons cannot be distinguished by a fingerprint, there are many cases in which the distinction can be made by the shape of the finger.

In the present invention, the relative positions of two fingerprints and two
The width of the finger of the book provides information about the shape of the finger.

Returning to FIG. 2, the operation of the comparison device will be described. In the case of this device, assuming that the card user is not a legal user, the two fingerprints of two fingers adjacent to the unauthorized user are, by the guide unit 41, originally the fingerprint of the legitimate user, It is located at a different location from the location on the "read" prism to be located. Therefore, the area of the fingerprint of the unauthorized user is different from that of the authorized user (the aperture of the “read” prism is not wide), or the relative position of the fingerprint of the unauthorized user does not match that of the authorized user. Probability is high. In any case, since a fingerprint pattern different from the fingerprint pattern of the reflection hologram of the card 20 is displayed by Fourier transform, no coincidence occurs.

A plate with a record of the user's fingerprint attached to the surface,
Instead of the prism shown in FIGS. 1 and 2, it may be used as input means. The plate is located at the front focal plane of the lens between the illumination beam and the Fourier transform lens.

If the card 20 is a passport, personal information,
A memory may be provided to record customs clearance information, usually recorded by stamps.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus for signing fingerprint information,
FIG. 2 is a schematic diagram of an apparatus for comparing a reference data record with a fingerprint, and FIGS. 3A and 3B are schematic diagrams of a guide portion of a finger position indicator. 31 ... light source, 35 ... prism, 36 ... lens.

Claims (11)

(57) [Claims] A) a light source for irradiating an irradiation beam; and b) an optical device which receives a fingerprint of an individual placed in a beam path of the irradiation beam or fingerprint information obtained from a fingerprint record and modulates the information based on the fingerprint information. Input means for generating an information beam; c) optical Fourier exchange means for Fourier transforming the optical information beam and supplying the Fourier-transformed optical information beam to a conversion surface; and d) information relating to a reference fingerprint is recorded. Means for supporting an object including a reflection hologram such that the reflection hologram is on the conversion surface; e) a Fourier-transformed optical information beam generated by reflection from the reflection hologram; and the reflection hologram and the optical information beam And a collation result display means that operates in accordance with the intensity distribution of the light. A scientific fingerprint collation device. 2. The reflection hologram according to claim 1, wherein said reflection hologram records information relating to reference fingerprints obtained from at least two reference fingers adjacent to each other, and said object determines a width and a relative position of said at least two reference fingers. The input means comprises movable means for determining a position in accordance with the data representing the width and the relative position of the two adjacent reference fingers. 2. The optical fingerprint collating apparatus according to claim 1, wherein a position of said fingerprint or fingerprint record in said input means is determined. 3. The reflection hologram according to claim 1, wherein the reflection hologram is a frequency-multiplexed reflection hologram, wherein each frequency is within a range of a spectrum of the light source, so that sensitivity to a change in the size of the reference fingerprint is reduced. 2. The optical fingerprint matching device according to claim 1, wherein: 4. The reflection hologram according to claim 1, wherein said reflection hologram is a frequency-multiplexed reflection hologram, wherein each frequency is within a range of a spectrum of said light source, thereby reducing sensitivity to a change in size of said reference fingerprint. 3. The optical fingerprint matching device according to claim 2, wherein: 5. a) irradiating a light beam at an input means on which at least one fingerprint is placed to generate a fingerprint data beam; b) passing the fingerprint data beam through an optical Fourier transform means; The Fourier-transformed fingerprint data beam is reflected by a reflection hologram in which information on a reference fingerprint is recorded, to generate reflected light having an intensity distribution indicating a degree of correlation between the fingerprint data beam and the reflection hologram. An optical fingerprint collation method that indicates whether the fingerprint and the reference fingerprint match or not according to the light intensity distribution. 6. A light source for irradiating an irradiation beam and a reference beam, and b) receiving a fingerprint of a person placed on the beam path of the irradiation beam or fingerprint information obtained from a fingerprint record, and based on the fingerprint information. Input means for generating a modulated optical information beam; c) optical Fourier transform means for Fourier transforming the optical information beam and supplying the Fourier-transformed optical information beam to a conversion surface; d) the conversion surface and the reference Means for supporting the recording medium so as to be located on both sides of the beam path; e) reflection forming a reflection hologram on the recording medium based on the Fourier-transformed optical information beam and the reference beam. Reference data creation device comprising hologram processing means 7. A wavelength of light emitted from said light source is selectable, and said reflection hologram processing means is for creating a frequency-multiplexed reflection hologram on said recording medium. 7. The reference data creation device according to claim 6, wherein 8. A memory in which said input means comprises means for issuing a position signal for determining a position by at least two fingers adjacent to each other of an individual, and wherein said recording medium includes means for encoding said position signal. 7. The reference data creating apparatus according to claim 6, further comprising: 9. A memory in which said input means comprises means for issuing a position signal for positioning with at least two fingers of an individual adjacent to each other, and wherein said recording medium has means for encoding said position signal. The reference data creating device according to claim 7, comprising: 10. The apparatus according to claim 5, wherein at least two fingerprints are used and said at least two fingerprints are positioned on said input means in accordance with data relating to a finger width and a relative position of the finger. The described optical fingerprint collation method. 11. The reflection hologram is a frequency multiplexing reflection hologram, and when irradiating light from the light source to input means, a frequency spectrum including each frequency is stored in the frequency multiplexing reflection hologram. 11. The optical fingerprint collation method according to claim 10, wherein the optical fingerprint collating method is applied.