EP0807296A2

EP0807296A2 - Fingerprint profile registration system

Info

Publication number: EP0807296A2
Application number: EP96932857A
Authority: EP
Inventors: Antonie Hendrikus Meijering; Lodewijk Johan Van Ruyven
Original assignee: Gebroeders Frencken Beheer BV
Current assignee: Gebroeders Frencken Beheer BV
Priority date: 1995-09-28
Filing date: 1996-09-24
Publication date: 1997-11-19
Also published as: NL1001307C1; WO1997012340A3; WO1997012340A2

Abstract

An apparatus for fingerline profile characterisation is provided with a light-pen shaped scanning system as well a television camera shaped imaging system. The apparatus offers the possibility to combine rapid camera imaging with a high resolution light-pen imaging. Thus the registration can be optimized with respect to velocity and reliability. Particularly signals from the camera imaging can be used to control the light-pen system. The velocity and reliability of the light-pen registration can be improved by using optical means in which turning points in the mechanical movement are avoided. Particularly two optical wedges rotatable in a reverse sense with respect to one another are used to generate a linear x-y scanning by a singular rotation.

Description

FINGERPRINT PROFILE REGISTRATION SYSTEM

The invention relates to a fingerline profile registration system comprising a sequentially pixel wise acting fingerprint registration device.

Such a registration system is known from WO 93-18486. A system disclosed therein suffers from a restricted speed of registration, due to the mechanical scanning method. It is an object of the invention to avoid this disadvantage and to this end a fingerprint profile registration system as listed in the preamble is characterized in that said sequentially acting device is arranged to registrate a first part of an exposed skin area and an imaging device is added to the system to registrate a second part of the exposed skin area enabling a high speed, simultaneous imaging of a fingerprint to be examined. Due to the fact that a fingerprint profile registration system according to the invention comprises as well a point to point, thus a sequential pixel wise imaging registration as a television camera, thus a simultaneous imaging device, a very reliable and high speed imaging can be realised.

Due to the fact that a fingerprint profile registration system as described in WO 93- 18486 is capable to measure fingerline properties in great detail, only a small skin area is needed for verification, provided identical parts of the exposed skin are measured. On the other hand CCD-camera type of fingerprint recognition systems are based on comparing the location of typica and therefore the accuracy increases with increasing test area or in other words missing a small part of a test area in the centre makes no difference if the same area also is excluded in the initial registration proces. For this reason use is made in a preferred embodiment of the invention of a glass parallopipid with a small hole peφendicular to the largest surface of said parallopipid. In this hole a reflective elastomer is placed as support for part of the skin surface to be investigated. Since both systems work simultaneously a very reliable and high speed imaging can be realised. The choice which of the imaging means will be used is denoted by the reliability of the registration in search but for example also by the quality of the object to be registrated, thus of the shape of the fingerprint or of an image thereof.

The registration of a humid or to the contrary a very dry or destructed fingerline profile can force to the slow sequential registration menthod for example, using the large area to check the orientation. In a preferred embodiment the simultaneous imaging device is provided with a CCD camera comprising a number of imaging pixel elements adapted to the resolving power of the registration system. Such a camera is cheap, is very reliable and has a high dynamic range in control and read out. Useful CCD camera systems are commercially availably. A fingerline profile registration system provided with a CCD camera is known per sβ from EP 300167. An apparatus disclosed therein suffers from a restricted resolving power and as a consequence the reliability can be unsufficient for a lot of applications.

A further preferred embodiment comprises means for selecting as yet sequentially to registrate object parts selected from images generated by a simultaneously imaging device.

Such a discriminator enables the combination of a high speed camera registration and a light-pen registration of image parts of the profile which are unsufficient accurate for further registration or of image parts having a relatively high density of profile characteristics.

In a further embodiment a sequential optical scanning device is provided with means for the use of focussing signals as height or dept defining signals (z-signals). Using these height focussing signals for a light-pen device the light-pen does not need any mechanical z movement. This fact increases the speed of scanning and results in a cheaper and more reliable device.

A further enbodiment comprises an opto-mechanical x-y scanning device provided with a pair of wedges Iocated in the beampath of the scanning light beam, which wedges are axially rotatable in a reverse sence with respect to one another such that the scanning light beam executes a linear x-y scanning

The fundamental advantage of such an embodiment is that mechanical turning points occurring in a normal opto-mechanical scanning device are avoided. The two wedges have merely to be rotated continously in a reverse sence to one another. Such a scanning can be very fast whilst the device becomes mechanical reliable and relatively cheap.

In a further embodiment signals generated by a simultaneously acting imaging device are used to control an opto-mechanical scanning system.

By combining signals from sequentially scanning registration and camera image signals a very efficient registration method can be realised. A camera image will still be recordered in practise and thus the camera signals needed are available without any additional action.

In a further embodiment segmented line transformation methods, are used for fingerline profile characterisation. Such methods per se are known from the literature for example from JEEE transactions on pattern analysis and machine intelligence vol 16 no 5 May 1994 pp 513-519 and thus need no further explanation here. These methods delever a very reliable line characterisation and show a high dynamic range for adapting to the shape of the line to be characterised.

A further embodiment according to the invention is provided with means for a point-to-point registration of relative angle variation of a tangent running along a line to be registrated. This menthod of registration is based on the knowledge that the shape of a fingerline is fully defined by a function K (s) on a line segment s whereby s denotes the running path part meansured along a fingerline and K (s) equals d θ / d s wherein Q (s) is the local angle between the line and the tangent. Thus the relative angle variation along the fingerline is defined and it is possible to code a collection of fingerlines using crossing points of a tranformed fingerline J K (s) taken as code wherin J is a number > 1.

The invention will be described in more detail hereafter with references to the drawing in which.

Fig. 1 shows schematically a registration system according to the invention, Fig. 2 shows a rotable wedge system to be used in such a system and Fig. 3 shows an embodiment of a coding line transformation therein.

A registration apparatus as showed in figure 1 is provided with a pierced trurr.cated prism 2 having a hole 3 provided with a reflecting elastomer skin support 5 a object surface 4 preferably forming part of the base plane 3 of a rectangular prism. The object surface 4 is illuminated with a lightbeam 10 from a light soure 6 via a prism surface 8. A lightbeam 12 refleted on the object surface 4 strikes, running through a prism surface 14 an entrance screen of a camera 16. The camera 16 prefarably has the shape of a CCD camera in which the number of light sensitive elements is adapted to an image resolution to be realised. The camera is connected to a signal processing device 18 for registration, processing, recording and control of image signals of a fingerline profile 20 positioned against the object surface 4. In this manner a fingerline profile can be recordered rapidly and can be analysed for further use.

In a sequential recording system 21 a light beam 24 of a light pen system 22 passes through a mirror 26 and an x - y - z scanning system 28, an objective lens 30 and a field lens 32 a top surface 34 of, in this case a truncated prism 2, and also strikes the object surface 4. A lightbeam reflected on the object surface strikes, running in a reverse direction, for example a photo diode system 36 of the light pen system. Thus a high resolution image can be generated of a fingerline profile or of a selected part thereof. Also a height information carrying image signal can thus be realised. Arrows x and z in figure 1 define the relevant scanning directions. The y-scan is directed square to the drawing surface. Via a connection 40 the scanning system is coupled to a signal processing unit 18.

A mechanical z movement for the relevant scanning can be avoided by means 41 arranged to obtain z values from the local focussing signals for the light pen system. In a similar manner camera image signals can be used for light-pen system control via a connection 42. Futher means 43 can be added to generate a point - to - point registration of the relative angle variation of the tangent running along the fingerline to be recorded. The system can furtheron be completed by adding signal processing units well known per se for example to select characteristic data for an on - line comparison of recorded data with data stocked in a memory etc.

An optical scanning system as shown in figure 2 is provided with a first optical wedge 50, a second optical wedge 52 being mounted in a support 54 and a support 56 respectivily. The wedges are mutually coupled enabling rotation in a mutually reverse sense with respect to one another as indicated with arrows 58 and 60. With such a system mounted for example in the beampath of the light beam 24 an x-y scanning can be generated with said light beam. Thus the time consuming and disturbing change-over points for the moving elements during scanning are avoided.

Claims

1 Fingerline profile registration system comprising a sequentially pixel wise acting fingerprint registration device characterized in that said sequentially acting device is arranged to registrate a first part of an exposed skin area and an image device (16) is added to registrate a second part of the exposed skin area enabling a high speed simultaneous complete imaging of a fingerlineprint to be registrated.

2 Fingerline profile registration system as claimed in claim 1 wherein the simultaneous imaging device is provided with a CCD camera comprising a number of image pixel elements adapted to the resolving power of the registration system.

3 Fingerline profile registration system as claimed in claim 1 or 2 wherein means (18) are provided for selecting sequentially to registrate object parts from simultaneously imaging signals.

4 Fingerline profile registration system as claimed in claim 1 , 2 or 3 wherein the sequential optical scanning device is provided with means (41) enabling the use of focussing signals as depth defining signals (z-signals). 5 Fingerline profile registration system as claimed in claim 1, 2, 3 or 4 wherein an opto¬ mechanical x-y scanning device is provided having a pair of optical means (50 and 52) Iocated in the beampath of the scanning beam which means are continuously rotatable with respect to one other, generating a linear x-y scanning for the scanning beam.

6 Fingerline profile registration system as claimed in claim 5 wherein the optical means (50 and 52) are optical wedges rotable with respect to one another mounted in the beampath of the scanning beam.

7 Fingerline profile registration system as claimed in any one of the preceding claims wherein signals generated by a simultaneously acting imaging device are used to control an opto-mechanical scanning system. 8 Fingerline profile registration system as claimed in any one of the preceding claims wherein use is made of segmented line transformation methods for fingerline profile characterisation.

9 Fingerline registration system as claimed in any one of the preceding claims wherein means are provided for a point - to - point registration of relative angle variation of a tangent running along a line to be registrated

10 Opto mechanical lightbeam scanning system provided with a pair of mutually in a reverse sense with respect to one another rotable optical wedges (50 and 52).