Optics: measuring and testing – Document pattern analysis or verification
Patent
1986-12-04
1988-11-15
Evans, F. L.
Optics: measuring and testing
Document pattern analysis or verification
356 72, 382 4, G06K 974
Patent
active
047844841
DESCRIPTION:
BRIEF SUMMARY
There are known various methods for optical scanning of the fingerprint side of a finger for ascertaining the identity of a person or for identifying the characteristic papillary pattern of a finger. The scanning may take place manually and the papillary pattern may be characterised by means of one of the known systems whereof some are digital so that the pattern characteristics may be machine processed as soon as the characterisation has been completed. Manual scanning, however, is highly time-consuming because a fingerprint readily comprises 25 characteristic details whereof at least 6-10 details will often have to be characterised in order to achieve positive identification.
There has therefore been developed various apparatuses for optical scanning of the fingerprint side of a finger. These apparatuses have a movable optical means which scans the fingerprint side. Mechanically movable means are difficult to design so that they will not take up too much space and such apparatuses moreover require regular maintenance.
The object of the invention is to provide a method and an apparatus for optical/electrical scanning of the fingerprint side of a finger without using any mechanically movable means so that there is obtained an apparatus which will not require maintenance. It is moreover an object to provide an apparatus which is rather small so that it can be built into existing apparatuses such as telephone apparatus, entrance control apparatus and the like.
Instead of mechanically scanning the fingerprint side, it is according to the invention the finger which is moved during an optical/electrical scanning where simultaneously with or immediately before the scanning the rate of movement of the finger is measured. The mechanical movements in the known apparatuses have thereby been transferred into a modest finger movement where in stead of placing the finger on or in a scanning means, the finger is slid on a scanning surface, whereby the fingerprint side is scanned and there is obtained an electrical signal representing the fingerprint which signal can be processed in the usual manner in electrical apparatuses for example for comparaison with stored information.
It is sufficient to make the scanning surface transparent at the place of scanning. The points along the scanning line where the finger touches the surface (the ridges of the fingerprint) will reflect the light differently from the points where the finger does not touch the surface. By scanning the passing finger line by line there is obtained a complete scanning of the fingerprint.
Certainty of identification or recognition is achieved in that the use of copied prints of fingers or the use of a false finger such as a plastic or rubber cast is thereby excluded. By proceeding as disclosed it is simply checked whether it is a true finger or not.
By a uniform friction between the finger and the scanning surface it is possible in a simple manner electrically to synchronise or scale the line scanning with the rate of movement which will be sufficiently constant during the scanning. The rate measuring is thus used for synchronising or scaling the scanning.
By measuring the skin resistance as disclosed there is obtained a sufficiently accurate measuring to determine whether it is a genuine finger or not.
It is sufficient to make the scanning area transparent by the scanning line. If, for example, a scanning surface made of plastics, for example glass or synthetic materials such as acrylic plastics is used, the entire surface except the scanning area itself may be coated by a black coating such as black paint or the like so that undesirable light or undesirable reflections are avoided. There is thus obtained an apparatus that is insensitive to changes in light strength etc. in the surroundings where the apparatus has been mounted.
There is thus obtained a simple apparatus where the purely physical design may be changed in many different ways, for example dependent on where the apparatus is to be used or mounted.
The functioning of the apparatus and certain
REFERENCES:
patent: 3639905 (1972-02-01), Vaida et al.
patent: 4322163 (1982-03-01), Schiller
patent: 4537484 (1985-08-01), Fowler et al.
patent: 4544267 (1985-10-01), Schiller
Evans F. L.
Jydsk Telefon A/S
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