A fingerprint reader and a method of operating it

[0001] The present invention relates to a fingerprint reader, and in particular to the more robust fingerprint reader, which can be used e.g. in credit cards and other types of elements that are somewhat flexible.

[0002] Fingerprint readers can be found, e.g., in documents WO99 / ​​41696 and WO2005 / 124659.

[0003] In general, fingerprint readers are based on technology that does not yield to bending, which creates a problem when they are provided in flexible elements.

[0004] Fingerprint readers for chip or electronic cards can be found, e.g., in documents US 6848617 and WO 03/009223.

[0005] In a first aspect, the invention relates to a fingerprint reader according to claim 1.

[0006] In the present context, a fingerprint reader should generally be considered to be an element adapted to determine fingerprint information.

[0007] The fingerprint sensor is an element adapted to detect at least part of the fingerprint and usually does so using a sensitive or sensitive surface. The fingerprint sensor can be adapted to determine the whole (relevant part) of the fingerprint in one measurement, which means that it has a sensitive surface that is large enough for the corresponding part of the finger to contact it simultaneously, or it can be adapted to move the finger over sensor for sequential detection of part of the fingerprint.

[0008] The sensor output information can be any type of information from which fingerprint information can be derived. This can be 2D information describing the positions / shapes of the protuberances or depressions of the fingerprint, or more complex and / or more compressed data. There are significant differences between the sensors here.

[0009] In the present context, a rigid element is an element that provides / maintains sufficient rigidity in the sensor so that it does not bend too much under the influence of a predetermined force. Of course, the property will be different in different applications, depending on how resistant the sensor is, but for use in e.g. credit cards, stiffness of 100 N / mm is preferred² or higher, e.g. 150 N / mm², preferably 200 N / mm² or higher, e.g. 250 N / mm², preferably 300 N / mm² or higher, e.g. 350 N / mm², preferably 400 N / mm² or greater.

[0010] In a preferred embodiment, the rigid element comprises a polymer, metal, fiberglass / epoxy layer, e.g. PCB, determining the total rigidity of the rigid element, 0.2 mm or more thick, e.g. 0.4 mm or more, 0.5 mm or more, 1 mm or more.

Preferably, a notch / recess or through hole extends along the main outer surface of the rigid element to accommodate the sensor there, with the sensitive surface facing away from the rigid element.

[0012] The rigid element may be PCBs, wherein the first electric conductors are formed in the conductive layers of the PCBs.

[0013] In one embodiment, the rigid member further comprises one or more electrically conductive surface parts located adjacent the sensitive surface of the sensor and adapted to be in contact with the finger, also in contact with the sensor. These parts of the conductive surface may alternatively or additionally be positioned adjacent the outer edge of the indentation / recess / through hole.

In this context, "adjacent" means that the finger will contact simultaneously both parts (part) of the electrically conductive surface and part of the sensitive surface of the sensor. Thus, usually the part of the sensitive surface and the part (part) of the electrically conductive surface will be apart spaced not more than 5 mm, e.g. 3 mm, preferably not more than 2 or 1 mm.

[0015] In this embodiment, it is preferred that the reader further includes means for providing a signal to the conductive part of the surface, the sensor being adapted to provide output information based on that signal provided to that (these) part of the surface.

[0016] Preferably, so-called Active Capacitive Measurement, in which an RF signal is introduced into the finger via a conductive surface (s), and the sensitive sensor elements detect the signal, like antennas, as the signal strength depends on the capacitive / resistive connection, therefore from the distance between the skin and the pixel.

[0017] Furthermore, placing the sensor and the conductive surface (s) in predetermined positions improves the detection and structure of the system, [0018] In this or another embodiment, the reader further includes a processing element containing information about the identity, the processing element is adapted to:

- receiving output information from the sensor,

- comparing the information received with the identity information, and

- consistency between information received and identity information.

[0019] In this context, "compliance" refers to the current type of information. It is important that based on this information it can be determined whether the detected / sensed fingerprint matches the one for which the information was saved.

[0020] Thus, a person's identity can be determined based on the determined fingerprint information and predetermined identity information that can be stored in the sensor or in combination with it.

[0021] In this regard, positive identification of a person or compliance of information may trigger an application that is only available after positive identification. This application may relate to data transmission as part of a financial transaction or door opening / access to the area. Any application supported today by smart cards or identification token can be launched in this way.

[0022] A particularly interesting aspect relates to a card in the size of a credit card comprising a fingerprint sensor according to the first aspect of the invention.

[0023] A card in the size of a credit card is a card with a longer dimension of 15 cm or less and a thickness of 3 mm or less. In fact, a size similar to the size of a standard credit card is preferred. One of the definitions of this type of card is the so-called 1D-1 card.

[0024] Such credit card must be flexible as stated in the ISO / IEC 10373-1 standard; the card subjected to a test load must achieve a deformation of between 35 and 13 mm and must return to no more than 1.5 mm from flat within one minute of removing the load.

[0025] This required flexibility creates a problem for the sensor. Thus, it is preferred that the sensor is stiffened or that the sensor surroundings are stiffened by a rigid element. In addition, it is desirable to maintain the total required stiffness / flexibility of the card, so the size of the rigid element along the long side of the rectangular card is no more than 25%, e.g. no more than 20%. Thus, the rest of the card may bend, and the sensor environment is more rigid.

[0026] In this aspect, it is preferred that the card further includes a processing element adapted to receive output from the sensor, the rigid element further comprising one or more parts of an electrically conductive surface, each of which is connected to the processing element. Thus, the signal from the sensor can be delivered to the processing element via a rigid element, which can be a PCB, to which the processing element can be connected to also provide this element with some rigidity and protect it from excessive bending.

[0027] The last aspect of the invention relates to a method according to claim 7 operating the fingerprint reader according to the first aspect or the card according to a particularly interesting aspect.

[0028] Thus, the sensor is supported or stiffened by a rigid element both during operation and in periods of inactivity when the user can operate the reader in a more random manner.

[0029] Furthermore, the rigid element is used not only for stiffening, but also for transmitting signals from the sensor.

[0030] In this or another embodiment, the coupling step includes contacting the applied finger additionally with one or more portions of the electrically conductive surface of the rigid element positioned adjacent the sensitive surface of the sensor. In addition, and in particular when the output stage includes providing a signal to the conductive portion of the surface and providing output information based on the signal provided in that (these) portion of the surface, a better fingerprint reading can be obtained.

[0031] Proper placement of the sensor relative to the rigid element and also the use of the surface of this rigid element simplifies the arrangement, while facilitating a good relationship between the relative positions of the two elements.

[0032] In another embodiment, the method further comprises the steps of;

- comparing the output with predetermined identity information, and

- consistency between information received and identity information.

[0033] The person's identity or the person's right to use e.g. a card for e.g. transactions, access, etc. can therefore be found, and the card processing element, etc. can then be used to support additional operations that are allowed / started / only started when the correct fingerprint has been entered, [0034] In the following, preferred embodiments of the invention will be described with reference to the figures, wherein:

- Fig. 1 illustrates a preferred embodiment seen from above,

- Figures 2 and 3 illustrate cross-sections of two different embodiments,

- Fig. 4 illustrates two detection methods.

[0035] Fig. 1 shows a preferred embodiment of a card or reader 8 with a sensor 12 positioned on or in the surface of the rigid element / PCB 10 for sliding a finger over the sensor 12, whereby information regarding fingerprint is displayed at the output.

[0036] In the present embodiment, the sensor 12 is adapted to move the finger (elongated structure). Alternatively, a sensor with a larger surface can be used that is adapted to read the fingerprint without finger movement.

[0037] The subject sensor 12 is of the so-called active capacitive measurement, which requires one or more electrodes 14 and 16, provided in its vicinity, to supply the signal to the finger during movement. This type of sensor can be found in WO99 / ​​41696. This is described below. [0038] In addition, a processor 24 may be provided on the PCB 10 to receive output information from the sensor 12 and to provide or control the signal (s) provided (to) to the electrodes 14 and 16.

[0039] Communication / supply of power between the processor 24 and the environment, such as a card reader or the like, can be supported by electrodes 18, 20, 22, which are provided around the sensor 12. However, the positions of these electrodes can be chosen freely. Of course, such power supply or communication can also, additionally or alternatively, take place through electrodes 14 and 16, [0040] To provide in PCB 8 card 10 and components attached thereto, it can be laminated in the same way as integrated circuits etc. are currently laminated in electronic cards.

[0041] In Figs. 2 and 3, cross sections are shown along the dashed line of Fig. 1. These two figures illustrate alternative embodiments in which the sensor 12 is provided either in the recess / indentation 26 (see Fig. 2) or in the opening 26 'through (see Fig. 3) PCB 10.

[0042] It should be noted that the thickness of the electrodes 14, 16, 18 and 20 can be exaggerated, but in principle any position and thickness can be used. Thicker electrodes also assist in providing a rigid element 10 supporting the sensor 12.

[0043] Preferably, the surfaces of at least the sensor 12 and the electrodes 14 and 16 are close together and at the same height to ensure that the finger sliding over it comes into contact with all these surfaces. [0044] It can be seen that providing the sensor 12 in the cavity / through hole 26/26 'has several advantages. One advantage is that the sensor 12 is protected by PCB 10, which is preferably relatively rigid. Such an elongated or larger surface sensor 12 can easily break, as it is usually tough and brittle to the glass, and because it may be desirable to provide a very thin sensor 12. In practice, it may be desirable to grind the sensor 12 to a thickness of 100 pm, eg to obtain total thickness as small as possible.

[0045] The thin sensor 12 may only require a very shallow indentation or recess in the PCB 10, while the higher or thicker sensors 12 may require a through hole, depending on the thickness of the PCB 10.

[0046] To provide the sensor 12 with the desired rigidity, the PCB 10 or PCB may be multi-layer, eg four-layer, wherein the PCB has a bending strength of 200-1000 N / mm2, eg between 460 and 580 N / mm2, ie like 1.6mm thick glass / epoxy fiber substrate (IPC-TM650, test method 2.4.4).

[0047] Naturally, this stiffness can be changed by changing the thickness or composition of the PCB 10.

[0048] The sensor 12 can be attached to the PCB 10 in any desired way. Usually the sensor 12 is electrically connected to one or more electrical conductors (not illustrated) on PCB 10, and such a connection may be sufficient. Alternatively or additionally, gluing or soldering / welding can be used.

[0049] Typically, PCB 10 includes a number of conductive elements connecting electrodes 14, 16, 18, 20 and 22 to processor 24 and sensor 12. They can be provided on the surface of PCB 10 and / or in the interior in a multilayer structure. [0050] At present, PCB 10 can be used in chip credit cards 8, wherein the processor 24 can be used to support both data from sensor 12, comparing the data received from recorded data to determine whether the person who uses the card is allowed to use this card, as well as ordinary transactions / communications supported by chip cards. Alternatively, a number of processors (integrated circuits, ASICs, FPGAs or their connections) can be used, [0051] Of course any type of communication can be used, eg via electrodes 18, 20, 22, wireless (eg radio, RF, RFiD, infrared, electromagnetic fields) or via other electrodes.

[0052] As mentioned above, the preferred measurement method is the active capacitive measurement method, as used by the sensors from Fingerprint Gards AB from Sweden, which has several significant advantages such as the commonly known high image quality, programmable pixels and 256 gray scale values ​​from each pixel. The sensors contain small capacitive plates, each with its own electrical circuit built into the integrated circuit. The sensors use the FPA (HSPA) method High Sensitive Pixel Amplifier), which allows each pixel in the sensor to detect a very weak signal, which improves the image quality for all types of fingers.

[0053] Direct and active capacitive measurement is illustrated at the top and bottom respectively of Fig 4. [0054] Extremely weak electric charges are generated, sent by the finger, forming a pattern between the protuberances or depressions of the finger and the sensor plates . Using these charges, the sensor measures surface capacity standard.

[0055] This product also has a protective coating, 25 to 30 times thicker than other suppliers, which helps the sensors withstand much more than the requirement of European Community Standard Class 4, ie 15kV for static electricity (ESD), as well as friction and tearing.

[0056] Capacity is the ability to store electrical charge. Sensor 12 contains tens of thousands of small capacitive plates with their own electrical circuits embedded in the integrated circuit. When a finger is placed on the sensor, extremely weak electric charges are generated, forming a pattern between the finger protuberances or depressions and the sensor plates. Using these charges, the sensor measures the surface capacity standard. The measured values ​​are digitized by the sensor and then sent to the neighboring microprocessor.

[0057] The surface of the capacitive sensor is a precise matrix of plates, capable of measuring the capacity between these plates and the contour of the fingerprint. This can be done directly by applying an electric charge to the plate;

[0058J The lower method of Fig. 4, which is the preferred method, is called the active measurement method, sometimes referred to as reflective or inductive capacitance measurement, and has several advantages. By using programmable logic inside the capacitive sensor system it is possible to read and adjust sensor reception for different skin types and conditions, another important advantage is that the enhanced signal transmission between the fingerprint surface and sensor plates allows the sensor surface to be put in a strong layer of protective coating to 25-30 times thicker than other suppliers. This enables the sensor to withstand the required electrostatic discharge (ESD) of 15kV and well above, as well as more than a million sensor touches during wear tests.