CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 U.S. National Stage of International Application No. PCT/SE2018/051086, filed Oct. 24, 2018, which claims priority to Swedish Patent Application No. 1751355-7, filed Oct. 31, 2017. The disclosures of each of the above applications are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a method of controlling an electronic device, the electronic device comprising a fingerprint sensor. The present disclosure also relates to a corresponding electronic device and to a computer program product.

BACKGROUND

Various types of biometric systems are used more and more in order to provide for increased security for accessing an electronic device, thereby providing an enhanced user convenience. In particular fingerprint sensors have been successfully integrated in such devices, for example, thanks to their small form factor, high performance and user acceptance. Among the various available fingerprint sensing principles (such as capacitive, optical, thermal, ultrasonic, etc.), capacitive sensing is currently most commonly used, in particular in applications where size and power consumption are important issues. The most common fingerprint sensors currently used have a size e.g. corresponding to fingertip (or smaller).

However, recently there has been a trend towards larger area fingerprint sensors. In relation to e.g. a mobile phone provided with a touch screen covering a majority of the front side of the mobile phone, such a large area fingerprint sensor may possibly be arranged such that it may be possible to capture a fingerprint image (of a finger of a user) essentially anywhere throughout a total surface area provided by the touch screen.

An example of such a system is disclosed in US20170053151A1, where an acoustic imaging sensor comprising a plurality of transducers is used for capturing a fingerprint image of a finger of a user touching the front of the mobile phone. The captured fingerprint image may be used either for detecting where at the front of the mobile phone the finger has placed his finger, or for authentication purposes, such as for authenticating an operation to be performed by the mobile phone.

The fingerprint sensing system according to US20170053151A1 provides for an excellent showcase of implementing fingerprint sensing throughout essentially the full front surface of the mobile phone. However, allowing uncontrolled capturing of fingerprint image data anywhere throughout the front surface of the mobile phone as is made possible using the implemented suggested in US20170053151A1 is not necessarily always positive, for example possibly having a negative impact on the responsiveness when using the fingerprint sensor. Thus, there appears to be room for further improvement, specifically in relation to how to control capturing of fingerprint image data in implementations where a large area fingerprint sensor is used.

SUMMARY

In view of above-mentioned and other drawbacks of the prior art, it is an object of the present disclosure to provide an improved method for determining and controlling where at a e.g. large area surface of a fingerprint sensor fingerprint image data may be allowed to be captured.

According to an aspect of the present disclosure, it is therefore provided a method of controlling an electronic device, the electronic device comprising a control unit, a display unit defining a first functional area, and a fingerprint sensor defining a second functional area, wherein the second functional area at least partly overlaps with the first functional area, wherein the method comprising the steps of detecting a user's finger within a portion of the second functional area of the fingerprint sensor, the portion defining a sensing area for the fingerprint sensor, the sensing area arranged at a first position within the second functional area of the fingerprint sensor, acquiring, at the sensing area using the fingerprint sensor, a fingerprint image of a finger of the user, authenticating, using the control unit, the user based on the acquired fingerprint image, receiving, at the control unit, a request to redefine the position of the sensing area, and determining, using the control unit, a second position for the sensing area only if the user has been successfully authenticated.

The present disclosure is based upon the realization that it possibly may be desirable to limit where, within a functional area of the fingerprint sensor, a fingerprint should be allowed to be acquired, such as at a selected portion (sensing area) of the functional area of the fingerprint sensor. In addition, it is desirable that a user of the electronic device may control a specific location of this selected portion of the functional area of the fingerprint sensor. However, the inventors have identified it may not be suitable to allow e.g. a relocation of the specific location to anyone. Rather, only an authenticated user should be allowed to perform such an action.

Accordingly and in line with the present disclosure, the user is first authenticated based on a fingerprint image acquired at a first position associated with the selected portion of the fingerprint sensor defining a sensing area. Then, only if the user is authenticated, the user is allowed to provide information defining a second position for the sensing area. The second position is then typically used for subsequent user operation involving the fingerprint sensor.

Advantages following the present disclosure involves e.g. for individualized operation of the electronic device comprising the fingerprint sensor based on the repositioning functionality as discussed above. In addition, since only an authenticated user is allowed to decide on where to position the sensing area, it may also be possible to allow for “hidden” authentication, possibly allowing the location for successfully acquiring a fingerprint image to be unknown for anyone else but the “true” owner of the electronic device.

Within the context of the present disclosure, the expression “fingerprint image” should be interpreted broadly and to include both a regular “visual image” of a fingerprint of a finger as well as a set of measurements relating to the finger when acquired using the fingerprint sensor. A plurality of fingerprint images may be subsequently acquired and fused together during a single session, where the resulting information is used as an input for determining fingerprint related features for used e.g. in relation to the authentication of the user's finger.

In a possible embodiment of the present disclosure the request to redefine the position of the sensing area comprises at least one of determining if a duration for detection of the finger within sensing area exceeds a first threshold, and determining if a pressure applied by the users finger within the sensing area exceeds a second threshold. That is, the repositioning may for example be initiated by the user holding his finger for a “long” time (first threshold) at the first location or by applying an increased amount of pressure (second threshold) with his finger in a direction towards the fingerprint sensor. It should however be understood that other means may be applied for initiating the repositioning, such as for example by voice command or by allowing the user to enter into a settings menu presented at a graphical user interface (GUI) provided at the display unit, or by pressing a predefined button at the electronic device, etc. The GUI may also be used for providing an instruction to the user for repositioning of the finger for determining the second position for the sensing area.

Furthermore, the determination of the second position for the sensing area may for example comprise determining a position of the user's finger within the second functional area. Accordingly, the total functional area of the fingerprint sensor may possibly be used for determining the second location. That is, the total functional area of the fingerprint sensor may be used for identifying the location of the users finger for determining the second position, such as for example by acquiring, using the fingerprint sensor, one or a plurality of fingerprint images at the second functional area at least partly outside of the sensing area.

As an alternative (or also), the display unit may be implemented as a touch display screen and determination of the position of the user's finger may comprises determining a position of the user's finger within the first functional area of the touch display screen, and correlating a coordinate system for the first functional area with a coordinate system for the second functional area for determining the position of the user's finger within the second functional area. Accordingly, an indication of the second location is determined using the touch screen and then “mapped” to the coordinate system of the fingerprint sensor.

In an embodiment of the present disclosure, the first position is different from the second position. It may be possible to only allow the second position to be set if the second position differs from the first position with more than a distance threshold. Possibly, such a distance threshold may correspond to at least 5% of a width or height of the functional area of the fingerprint sensor.

As defined above the first functional area of the display unit at least partly overlaps with the second functional area pf the fingerprint sensor. In a preferred embodiment of the present disclosure the second functional area constitutes at least 70% of the first functional area, preferably at least 80% and most preferably 90%. Accordingly, in such an embodiment the functional are of the fingerprint sensor will be defined to be within “a boundary” of the display unit, where the display unit overlaps with the fingerprint sensor. As would be apparent, there may thus be desirable (in line with the discussion above) to have information available for allowing a correlation between a coordinate system for the display unit and the overlap between the display unit and the fingerprint sensor to be readily available when the display unit (and touch screen) is used for determining the second position.

The fingerprint sensor may, as indicated above, be implemented using any kind of currently or future fingerprint sensing principles, including for example capacitive, optical, thermal or ultrasonic sensing technology.

In a preferred embodiment of the present disclosure, the fingerprint sensor is implemented using said ultrasonic technology. In a possible embodiment, the fingerprint sensor may comprise a plurality of ultrasonic transducers in the vicinity of a circumference of the second functional area, and the method further comprises the step of operating a selected portion of the plurality of ultrasonic transducers for acquiring the fingerprint image. Preferably, the portion of the plurality of ultrasonic transducers may be selected based on the first or the second position of the sensing area. Accordingly, rather than activating all of the transducers only a selected few or set of transducers are used, thus allowing for an optimization of an energy consumption of the fingerprint sensor, possibly allowing for an increase operational lifetime of the electronic device in case the electronic device is battery powered.

It may, in line with the present disclosure, be possible to further allow for a size of the user's finger to be identified (i.e. the area of the finger comprising the users fingerprint), and defining a size of the sensing area based on the size of identified size of the user's finger. Such an embodiment may possibly further increase the security of the electronic device as only a sensing area corresponding to that specific user may be allowed to be used for acquiring fingerprint images. In addition, this may also allow for a further optimization of the number of ultrasonic transducers that are to be selected/activated for capturing fingerprint images.

According to the present disclosure, the control unit is preferably an ASIC, a microprocessor or any other type of computing device for controlling the operation of the fingerprint sensor. However, the control unit may also be a general control unit comprised with the electronic device, for example configured for controlling the overall operation of the electronic device.

According to another aspect of the present disclosure, there is provided an electronic device, comprising a control unit, a display unit defining a first functional area and a fingerprint sensor defining a second functional area, wherein the second functional area at least partly overlaps with the first functional area, wherein the electronic device is adapted to detect a user's finger within a portion of the second functional area of the fingerprint sensor, the portion defining a sensing area for the fingerprint sensor, the sensing area arranged at a first position within the second functional area of the fingerprint sensor, acquire, at the sensing area using the fingerprint sensor, a fingerprint image of a finger of the user, authenticate, using the control unit, the user based on the acquired fingerprint image, receive, at the control unit, a request to redefine the position of the sensing area, and determine, using the control unit, a second position for the sensing area only if the user has been successfully authenticated. This aspect of the present disclosure provides similar advantages as discussed above in relation to the previous aspect of the present disclosure.

In a possible embodiment of the present disclosure the electronic device is mobile and implemented as a mobile phone, a tablet or a laptop.

According to a further aspect of the present disclosure, there is provided a computer program product comprising a non-transitory computer readable medium having stored thereon computer program means for a control unit adapted for controlling an electronic device, the electronic device further comprising a display unit defining a first functional area, and a fingerprint sensor defining a second functional area, wherein the second functional area at least partly overlaps with the first functional area, wherein the computer program product comprises code for detecting a user's finger within a portion of the second functional area of the fingerprint sensor, the portion defining a sensing area for the fingerprint sensor, the sensing area arranged at a first position within the second functional area of the fingerprint sensor, code for detecting acquiring, at the sensing area using the fingerprint sensor, a fingerprint image of a finger of the user, code for detecting authenticating, using the control unit, the user based on the acquired fingerprint image, code for detecting receiving, at the control unit, a request to redefine the position of the sensing area, and code for detecting determining, using the control unit, a second position for the sensing area only if the user has been successfully authenticated. Also, this aspect of the present disclosure provides similar advantages as discussed above in relation to the previous aspects of the present disclosure.

As mentioned above, the control unit is preferably an ASIC, a microprocessor or any other type of computing device. Similarly, a software executed by the control unit for operating the inventive system may be stored on a computer readable medium, being any type of memory device, including one of a removable nonvolatile random access memory, a hard disk drive, a floppy disk, a CD-ROM, a DVD-ROM, a USB memory, an SD memory card, or a similar computer readable medium known in the art.

Further features of, and advantages with, the present disclosure will become apparent when studying the appended claims and the following description. The skilled addressee realize that different features of the present disclosure may be combined to create embodiments other than those described in the following, without departing from the scope of the present disclosure.

