in the enclosed drawings , an embodiment of a transmitter unit in accordance with the invention is indicated by the reference sign 1 . it comprises a body including a fastening portion 2 and an extension and / or led support 3 which comprises a signal led 5 and a status led 4 . opposite the support 3 , the activating switch 6 — in this case , a contact switch — is attached to the fastening portion 2 . the switch 6 can be any switch , including for example a push - button switch . a cavity 9 is provided in the lower part of the support 3 for a button cell battery 8 which provides the energy supply for emitting signals through the leds 4 , 5 . a passage 7 — in this case , a circular hole — is situated in the upper part of the fastening portion 2 . the aforesaid component designations can in particular be gathered from fig1 to 3 . fig4 to 7 show an instrument 10 which comprises an instrument grip 11 and a tip 13 and which is embodied as a pointer and / or pointing apparatus . the grip has a corrugated portion 12 at which it can be securely held , and three reference markers 14 , and 18 protrude upwards out of the grip and serve as tracking markers for a medical tracking system 31 which comprises two tracking cameras which are schematically shown in fig6 and 7 but not separately indicated . the foremost tracking marker 18 is shown in more detail in fig4 and comprises the protruding marker holder 16 and the marker sphere 17 on the fixing portion 19 . as can be gathered from fig4 and 5 , the transmitter unit 1 in this embodiment is plugged onto the marker holder 16 using the transit hole 7 and then onto the fixing portion 19 and is fixed and / or secured against being unintentionally lost by screwing - on the marker sphere 17 . fig6 and 7 also show different defined spatial regions 40 , 41 , 42 and 43 which are formed and / or defined around tracking references 30 and / or 35 . the subsequent description of the invention will now be based on said figures and designations . like any standard navigation instrument comprising passive tracking technology , the instrument 10 also has reflection markers 14 , 15 and 18 , and these markers and / or their reflective spheres ( for example , 17 ) reflect emitted infrared light and are thus positionally detected by the tracking system 31 . conventional navigation systems use these position data as three - dimensional position information for particular marker geometries and assign it to particular instruments , such that the navigation system always for example knows where the front end of the tip 13 of the instrument 10 is situated . the transmitter unit 1 in accordance with the present invention , which can be regarded as an active input device for software control , is fastened to an instrument marker 18 on the instrument 10 as shown in fig4 and 5 and as already described above . in this position , the switch 6 can easily be reached by a finger ; when it is activated , the infrared led 5 emits an infrared light signal for software control , which is for example detected by the tracking system 31 , and the led 4 emits a visible light signal as a confirmation or status signal , so that the user knows that the invisible infrared signal of the led 5 has indeed also been transmitted . as already indicated above , the power supply for this is provided by the button cell 8 in the battery holder 9 . the transmitter unit 1 , which in this case is produced from plastic as a disposable item , is advantageously designed such that it can be attached symmetrically , such that it can be attached to the instrument universally for right - handed or left - handed operation , i . e . with the support extension 3 aligned in one or other direction of the instrument body , away from its longitudinal axis . in the preferred embodiment , the transmitter unit 1 is attached at a defined position on the navigated instrument 10 , namely to the fixing portion 19 , such that the software can identify the positional range of the infrared led support signal , which is stored in the navigation system together with the geometric information about the instrument 10 . when the activating switch 6 is activated , the infrared led signal of the diode 5 is activated . during this “ active mode ”, the led 5 is tracked by the tracking cameras of the tracking system 31 , and the signal emitted is used to control a software functionality of the navigation system , for example as a confirmation signal . the positional accuracy of the infrared led 5 is then less important , because only the more exactly positioned passive markers 14 , 15 and 18 reference the instrument geometry . for this reason , the transmitter unit can be designed very simply and cheaply , as a sterile disposable item . in another embodiment , active trigger signals could be used to digitize registration points on objects , for example bone surfaces , without having to generate additional trigger movements or other trigger signals . with respect to applicability , active disposable transmitter units in accordance with the invention can be universally used in combination with any possible existing passive instruments and pointing apparatuses ( pointers ), and already - existing passive pointer apparatuses can therefore be equipped and / or augmented with active control functionalities . the transmitter units could also be embodied to be compatible with other passive navigated instruments , for example drill guides , cutting blocks , awls , broaching tools , etc ., wherein they would likewise be fastened ( as disposable items ) to these instruments and detached again after use . if such sets of instruments are provided , they could have specifically assigned and embodied interfaces for attaching the universal disposable transmitter units . other technical features can be integrated , such as additional infrared leds , wireless rf communications modules or a plurality of control buttons , which would increase functionality even further , in particular also with regard to the software interaction for standard passive instruments . another aspect of the invention , which may be referred to as non - contact software workflow control , shall now be explained in more detail by referring specifically to fig6 and 7 . during medical navigation , reference arrays 30 , 35 are usually provided and fastened to the patient , in order to be able to reproduce the patient &# 39 ; s movements and integrate them into navigation . on the basis of these reference geometries 30 , 35 ( or also on the basis of other reference geometries provided ), it is then possible to determine pre - defined virtual spatial regions which can serve as a remote control for using the instrument . if , for example , a pointed end of a navigated instrument is introduced into such a remote control region , for example the region 40 around the reference array 30 in fig6 , a particular “ remote control mode ” for the software is launched . in the case of “ one - button ” control , the user can then control functionalities of the active transmitter unit in order to communicate simple commands such as “ next ”, “ back ” or “ select ”. thus , “ next ” functions can for example be assigned to short signals ( less than 0 . 5 seconds ), while activating the switch 6 for longer ( more than one second ) can be classified and pre - defined as a “ back ” command , when the tip 13 of the pointer instrument 10 is situated in the virtual region 40 around the reference array 30 . if a different function , for example a “ select ” function , is then required , the user can remove the front end of the tip 13 from the virtual region 40 around the reference array 30 , and when the tracking and navigation system determines that this tip end is not situated in the region 40 , a different command is assigned to activating the switch 6 , for example a “ select ” command . subsequent clicks on the active input device 1 would then for example confirm , select , activate or digitize reference points on parts of the patient &# 39 ; s body . using a “ sustained ” activation of the button and / or signal emitter , it is also possible to register multiple surfaces , wherein the tip of the pointer instrument is guided over the surface to be registered , and the software ensures that points are not repeatedly recorded . the remote control regions 40 in accordance with the invention are situated in a freely defined and definable space around the reference array 30 . another embodiment , shown in fig7 , provides for sub - dividing the remote control region into three free regions 41 , 42 and 43 between the arms of the reference star 35 . each region then has a different functionality when the pointer tip is introduced into it , and corresponding functionalities can be accessed by pressing the activating switch 6 , wherein the tip of the pointer can remain spatially free and does not have to contact the reference star 35 at predetermined or pre - defined locations , such that shifts in references and resultant registration inaccuracies are avoided . the embodiments of the present invention thus enable a non - contact , wireless and very comfortable interaction between the person performing the treatment and a software of a navigation system . the person performing the treatment controls the functionalities of the system by using a navigated instrument in the sterile environment . by assigning an active interaction device to the passive navigated instrument , the range of possible methods is extended and allows a greater variety of control inputs ( for example , during registration ), without having to perform the movements or perform separate selecting or confirming controls . the transmitter unit can be placed , as a disposable item and active auxiliary element , onto existing passive navigated instruments ( for example as a clip ), and it is thus possible to avoid problems which arise , due to integrated electronics , when heat and steam are used in sterilizations . the advantages of the invention in general and of different specific embodiments of the invention can also be listed as follows : an intuitive interaction between the user and the software / computer system is possible ; objects can be registered in the navigation system more comfortably , easily and quickly ; slipping during object registration , for example bone registration , can be avoided because confirming movements are avoided ( pivoting ); it becomes possible to optimally align reference arrays for the best possible recognition / accuracy during registration ( pivoting movements through regions with restricted visibility is not required ); there is no need for autoclaving , such that damage to electronic components and energy supply elements can be avoided ; there is compatibility with existing passive instruments , such as for example pointers ; and computer program elements of the invention may be embodied in hardware and / or software ( including firmware , resident software , micro - code , etc .). the computer program elements of the invention may take the form of a computer program product which may be embodied by a computer - usable or computer - readable storage medium comprising computer - usable or computer - readable program instructions , “ code ” or a “ computer program ” embodied in said medium for use by or in connection with the instruction executing system . within the context of this application , a computer - usable or computer - readable medium may be any medium which can contain , store , communicate , propagate or transport the program for use by or in connection with the instruction executing system , apparatus or device . the computer - usable or computer - readable medium may for example be , but is not limited to , an electronic , magnetic , optical , electromagnetic , infrared or semiconductor system , apparatus , device or medium of propagation , such as for example the internet . the computer - usable or computer - readable medium could even for example be paper or another suitable medium on which the program is printed , since the program could be electronically captured , for example by optically scanning the paper or other suitable medium , and then compiled , interpreted or otherwise processed in a suitable manner . the computer program product and any software and / or hardware described here form the various means for performing the functions of the invention in the example embodiment ( s ). although the invention has been shown and described with respect to one or more particular preferred embodiments , it is clear that equivalent amendments or modifications will occur to the person skilled in the art when reading and interpreting the text and enclosed drawing ( s ) of this specification . in particular with regard to the various functions performed by the elements ( components , assemblies , devices , compositions , etc .) described above , the terms used to describe such elements ( including any reference to a “ means ”) are intended , unless expressly indicated otherwise , to correspond to any element which performs the specified function of the element described , i . e . which is functionally equivalent to it , even if it is not structurally equivalent to the disclosed structure which performs the function in the example embodiment ( s ) illustrated here . moreover , while a particular feature of the invention may have been described above with respect to only one or some of the embodiments illustrated , such a feature may also be combined with one or more other features of the other embodiments , in any way such as may be desirable or advantageous for any given application of the invention .
the invention relates to a medical instrument , comprising a signal transmitter and at least one activating device for activating the transmitter which is provided on a transmitter unit which is separate from the instrument , wherein the transmitter unit is a unit which can be fastened to the exterior of the instrument . it also relates to a method for controlling a treatment - assisting medical software by means of a signal transmitter which is arranged on a medical instrument , wherein the instrument is positionally detected by means of a medical tracking system , and wherein the software assigns a different significance to the signal output by the transmitter depending on the position of the instrument .