the present invention will now be described more fully hereinafter with reference to the accompanying drawings , in which currently preferred embodiments of the invention are shown . this invention may , however , be embodied in many different forms and should not be construed as limited to the embodiments set forth herein ; rather , these embodiments are provided for thoroughness and completeness , and fully convey the scope of the invention to the skilled person . like reference characters refer to like elements throughout . turning now to the drawings and to fig1 in particular , there is schematically illustrated the electronic device according to the present invention , in the form of a mobile phone 100 with an integrated fingerprint sensor 102 and a display unit 104 with a touch screen interface 106 . in this embodiment the fingerprint sensor 102 and the display unit 104 are together arranged at the front side of the mobile phone 100 . the fingerprint sensor 102 may , for example , be used for unlocking the mobile phone 100 and / or for authorizing transactions carried out using the mobile phone 100 , etc . the fingerprint sensor 102 may of course also be placed on the backside of the mobile phone 100 . preferably and as is apparent for the skilled person , the mobile phone 100 shown in fig1 further comprises a first antenna for wlan / wi - fi communication , a second antenna for telecommunication communication , a microphone , a speaker , and a phone control unit . further hardware elements are of course possibly comprised with the mobile phone . it should furthermore be noted that the invention may be applicable in relation to any other type of portable electronic device , such as a laptop , a remote control , a tablet computer , or any other type of present or future similarly configured device . with reference to fig2 , there is conceptually illustrated a somewhat enlarged view of the fingerprint sensor 102 . in the case of employing a capacitive sensing technology , the fingerprint sensor 102 is configured to comprise a large plurality of sensing elements , preferably arranged as a two - dimensional array . the two - dimensional array may have sizes depending on the planned implementation and in an embodiment 160 × 160 pixels are used . other sizes are of course possible and within the scope of the invention , including two - dimensional array with less pixels as compared to the above example . a single sensing element ( also denoted as a pixel ) is in fig2 indicated by reference numeral 202 . it should be understood that the invention may be applied to other types of sensors , for example provided in relation to vision system . in such a case a camera is typically included where e . g . a surface of a substrate / lens provided with the camera at a location facing e . g . a user / object may be provided with a fixed pattern . the camera may be arranged to capture e . g . a face or body part of a user to be subsequently used for identifying / authenticating the user . turning to fig3 a - 3 f in combination with fig5 , there is conceptually illustrated a possible implementation of the invention . the basic idea of the invention is to utilize the geometric alignment information between e . g . a fingerprint template for a user and a fingerprint sample used for identification / authentication of the user to assist in filtering out the fixed pattern in the pattern recognition process . since a fixed pattern imposed onto e . g . the fingerprint sensor 102 will have fixed alignment to a reference coordinate system of the fingerprint sensor 102 , whereas the fingerprint sample of interest generally will not , this property can be exploited to help separate what is fingerprint sample data of interest and what is not . specifically , in fig3 a there is illustrated an example of a “ top surface ” ( e . g . coating ) of a fingerprint sensor 102 . a plurality of scratches 300 has been introduced at the top surface during normal use of the fingerprint sensor 102 , e . g . when the portable electronic device comprising the fingerprint sensor 102 has been placed in a pocket / bag of the user . it should be understood that the fixed pattern , e . g . scratches 300 , possibly could be deliberately introduced or inherent from the manufacturing of the fingerprint sensor 102 . when activating the fingerprint sensor 102 for acquiring a fingerprint image , as seen in fig3 b , the user will position his finger at or adjacently to the top surface of the fingerprint sensor 102 at a first random relative angle α 1 as compared to the fingerprint sensor 102 . the scratches 300 will accordingly be captured by the fingerprint sensor 102 along with friction ridges of the finger , the friction ridges of the finger representing the “ real ” fingerprint for the user . the digital representation of the friction ridges of the finger of the user at the first random relative angle α 1 combined with the scratches 300 at the surface of the sensor 102 are shown in fig3 c as a first distorted fingerprint image 302 . in a prior art solution , the distorted fingerprint image 302 will form an input for all subsequent image analysis , feature extraction , authentication , etc . accordingly , also the scratches will be taken as being part of the users fingerprint . however , in accordance to the invention , a first set of features being a representation of and determined , s 1 , from the distorted fingerprint image 302 are compared to a second set of features . it should be understood that each feature of the first set of features are defined to have a location and possibly a rotation provided in relation to the fingerprint sensor 102 . the second set of features may for example be determined from a second fingerprint image , or be part of e . g . a previously determined fingerprint template for the user . in the illustration provided in fig3 d , the second set of features are formed by the user again , e . g . at a later stage , positioning his finger at the fingerprint sensor 102 at a second random relative angle α 2 as compared to the fingerprint sensor 102 . in fig3 d the finger is slightly rotated as compared to the finger shown in fig3 b . in accordance to the invention , the first relative angle α 1 and the second relative angle α 2 are during normal use not expected to be the same , i . e . at least a small amount of misalignment is expected between the different times of the user positioning his finger at the fingerprint sensor 102 . in comparing fig3 b and 3 d only a small rotation is illustrated , a small translation of the position of the finger of the user is of course possible / likely . the digital representation of the friction ridges of the finger of the user at the second random relative angle α 2 combined with the scratches 300 at the surface of the sensor 102 are shown in fig3 e as a second distorted fingerprint image 304 . by means of the invention , alignment differences are measured , s 2 , the measurements made between the locations of the first set of features and the features of the second set of features . as is understood from the above , the features of the first and the second set of features relating to the scratches will have essentially ( or identically ) the same location ( and possibly rotation ) as compared to e . g . the reference coordinate system of the fingerprint sensor 102 . in the illustration provided in fig3 f , the first set of features relating to the first distorted fingerprint image 302 have been compared to the second set of features relating to the second distorted fingerprint image 304 . in accordance to the invention , a sub - set of features having alignment differences being “ too small ”, being smaller than a threshold , are extracted out and identified , s 3 , as possibly being part of the fixed pattern , e . g . conceptually illustrated as the scratches 300 , at the surface of the fingerprint sensor 102 . the identified sub - set of features may for example be filtered out from the first 302 and / or the second 304 distorted fingerprint images , thus forming a purified fingerprint image . the information may alternatively be used within a matching process , possibly allowing for a higher matching threshold if an in comparison large amount of fixed pattern has been identified . in a possible embodiment of the invention , it may be of interest to allow for a fingerprint template for the user to be “ continuously ” updated during use , for allowing small changes to the fingerprint of the user to be accounted for . it is undesirable to introduce a fixed pattern with such an updated fingerprint template . thus , it may in accordance to the invention be possible to check that a given feature from a first fingerprint image can be found in another fingerprint image with a non - identity transform ( i . e . “ enough misalignment ”), before the feature is allowed to be admitted into the template . this constraint to template updating should also allow for an improved safety of a system comprising the disclosed solution as e . g . an intentionally introduced fixed pattern ( e . g . by a potential imposter ) will be identified and accordingly not allowed to be introduced with any updated fingerprint templates . in the above presentation of the invention it is stated that the identification of the possible fixed pattern is done when the alignment difference is less than a threshold . the threshold could be predetermined or be continuously updated . the threshold could also be dependent on if it previously has been determined that a fixed pattern is present at the fingerprint sensor 102 . the threshold may also in some implementations be allowed to be set by the user , e . g . for improved security / safety of the system comprising the fingerprint sensor 102 . in accordance with the invention , the fingerprint sensor 102 and the operation for acquiring a fingerprint image is achieved using a conceptualized fingerprint sensor system 400 as is illustrated in fig4 . the fingerprint sensor system 400 in turn , typically , forms part of the electronic device / mobile as is exemplified in fig1 . the fingerprint sensor system 400 comprises the fingerprint sensor 102 and a processing circuitry , such as a control unit 402 for controlling the fingerprint sensor 102 . the fingerprint sensor system 400 further comprises a memory , such as a database 404 , e . g . storing a fingerprint template for the user . the control unit 402 may each include a microprocessor , microcontroller , programmable digital signal processor or another programmable device . the control unit 402 may also , or instead , each include an application specific integrated circuit , a programmable gate array or programmable array logic , a programmable logic device , or a digital signal processor . where the control unit 402 includes a programmable device such as the microprocessor , microcontroller or programmable digital signal processor mentioned above , the processor may further include computer executable code that controls operation of the programmable device . it should be understood that all or some parts of the functionality provided by means of the control unit 402 ( or generally discussed as “ processing circuitry ”) may be at least partly integrated with the fingerprint sensor 402 . the control functionality of the present disclosure may be implemented using existing computer processors , or by a special purpose computer processor for an appropriate system , incorporated for this or another purpose , or by a hardwire system . embodiments within the scope of the present disclosure include program products comprising machine - readable medium for carrying or having machine - executable instructions or data structures stored thereon . such machine - readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor . by way of example , such machine - readable media can comprise ram , rom , eprom , eeprom , cd - rom or other optical disk storage , magnetic disk storage or other magnetic storage devices , or any other medium which can be used to carry or store desired program code in the form of machine - executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor . when information is transferred or provided over a network or another communications connection ( either hardwired , wireless , or a combination of hardwired or wireless ) to a machine , the machine properly views the connection as a machine - readable medium . thus , any such connection is properly termed a machine - readable medium . combinations of the above are also included within the scope of machine - readable media . machine - executable instructions include , for example , instructions and data which cause a general purpose computer , special purpose computer , or special purpose processing machines to perform a certain function or group of functions . although the figures may show a sequence the order of the steps may differ from what is depicted . also two or more steps may be performed concurrently or with partial concurrence . such variation will depend on the software and hardware systems chosen and on designer choice . all such variations are within the scope of the disclosure . likewise , software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps , processing steps , comparison steps and decision steps . additionally , even though the invention has been described with reference to specific exemplifying embodiments thereof , many different alterations , modifications and the like will become apparent for those skilled in the art . in addition , variations to the disclosed embodiments can be understood and effected by the skilled addressee in practicing the claimed invention , from a study of the drawings , the disclosure , and the appended claims . furthermore , in the claims , the word “ comprising ” does not exclude other elements or steps , and the indefinite article “ a ” or “ an ” does not exclude a plurality .