WO2025008367A1

WO2025008367A1 - Calibration device, system and method

Info

Publication number: WO2025008367A1
Application number: PCT/EP2024/068645
Authority: WO
Inventors: Stephan Böhringer; Sven Müller; Adrian RUDIN
Original assignee: MININAVIDENT AG
Current assignee: MININAVIDENT AG
Priority date: 2023-07-04
Filing date: 2024-07-03
Publication date: 2025-01-09
Anticipated expiration: 2026-01-04

Abstract

A calibration device (1) for a surgical instrument (4) having an adapter (41) for receiving a tool and an imaging unit (42) directed towards the adapter (41) for imaging the tool in operation comprises a stud member (2) and a marker carrier (3). The stud member (2) is configured to be received by the adapter (41) of the surgical instrument (4). The marker carrier (3) has a first face and a second face. The marker carrier (3) is connected to the stud member (2). The stud member (2) has an axis (23). The first face of the marker carrier (3) is provided with a first marker structure (33). The first marker structure (33) is positioned in line with the axis (23) of the stud member (2). The second face of the marker carrier (3) is provided with a second marker structure (34) and a third marker structure (35), wherein the second marker structure (34) and the third marker structure (35) are positioned offset the axis (23) of the stud member (2). The calibration device (1) is configured to selectively expose either the first face of the marker carrier (3) or the second face of the marker carrier (3) towards the imaging unit (42) of the surgical instrument (4), when the stud member (2) is received by the adapter (41) of the surgical instrument (4).

Description

DESCRIPTION

Title

CALIBRATION DEVICE, SYSTEM AND METHOD

Technical Field

[0001] The present invention relates to a calibration device according to the preamble of independent claim 1 and, more particularly, to a calibration system and a method of calibrating a surgical instrument. Such calibration devices comprising a stud member configured to be received by an adapter of a surgical instrument and a marker carrier having a first face and a second face, wherein the marker carrier is connected to the stud member and the stud member has an axis, can be used for calibrating the surgical instrument including the adapter for receiving a tool and an imaging unit directed towards the adapter for imaging the tool in operation.

Background Art

[0002] In dental and/or cranio-maxillofacial surgery it is known to use instruments for bone surgery having an intervention tool such as a drill, a round burr, a saw, a cutter, an osteotome, a scissel or the like together with a camera for observing the intervention tool and its operation. Moreover, in order to assist an operator during dental and/or cranio-maxillofacial surgery, navigation systems have been developed for controlling and/or monitoring the position and orientation of the intervention tool relative to a body part of a patient.

[0003] For example, surgical devices are known involving an image output on which the intervention tool and the body part are shown in the correct position and orientation relative to each other. An image processor generates a representation of the body part on the basis of image data captured by means of a medical imaging method such as computer tomography or the like, and on the basis of actual images captured during operation. The devices may further comprise an image display control which shows a virtual image of an actual situation on a display, wherein the virtual image is superimposed with information about the operation such as a tool axis or the like (augmented reality). The actual situation is provided by a video image capture unit which is fixedly arranged on the surgery device. The position and orientation of the intervention tool with respect to the body part is ascertained by a stationary tracking system having two or more cameras and two reference assemblies, one assembly being placed on the part of the patient’s body and the other assembly being placed on the instrument. In order to allow proper operation, the two reference assemblies always have to be within a field of view (FoV) of the tracking system.

[0004] More compact and handy systems are also known, which comprise a surgical handpiece, an imaging unit which is movably attached to the surgical handpiece, and a marker member which is attachable to a cranial bone, a facial bone, a tooth or teeth of a patient. The marker member comprises a plurality of marker elements which are detectable by the imaging unit.

[0005] In order to allow precise surgical navigation during dental and/or cranio- maxillofacial surgery, it is necessary to provide the known systems with precise and reliable information about the geometrical characteristics of the surgical instrument, in particular about the surgical instrument and its intervention tool, as well as the relative position and orientation of the surgical tool to the remainder of the surgical instrument. Hence, it is necessary to measure the geometrical characteristics of the intervention tool and the relative position and orientation of the intervention tool in the surgical instrument every time the intervention tool is changed or adapted. Moreover, as during the dental and/or cranio-maxillofacial surgery procedure the intervention tool might move inside a tool holder of the surgical instrument, it typically is also necessary to acquire or update before-mentioned information during the dental and/or cranio-maxillofacial surgery procedure.

[0006] For accurate registration and identification of a dental and/or cranio- maxillofacial surgical instrument in a comparably simple and reliable manner, WO 2018/171862 A1 describes a registration and identification tool (RIT). The RIT comprises a body, a marker member which is optically detectable and provided on the body, and a recess in the body which extends from an outer surface of the body into the inside of the body, thereby defining an extension direction of the recess. The recess has a shape such as a tapered shape such that a lateral extension of the recess decreases in a direction from the outer surface of the body towards the inside of the body.

[0007] Even though the RIT of the prior art allows for efficient registration and identification of the surgical instrument and tool, there is still a need for a preferably more conveniently applicable device allowing to calibrate a surgical instrument and intervention tool as to clearance as well as position and orientation relative to each other.

Disclosure of the Invention

[0008] According to the invention this need is settled by a calibration device as it is defined by the features of independent claim 1 , by a method as it is defined by the features of independent claim 14, and by a calibration system as it is defined by the features of independent claim 19. Preferred embodiments are subject of the dependent claims.

[0009] In one aspect, the invention is a calibration device for a surgical instrument, which has an adapter for receiving a tool and an imaging unit directed towards the adapter for imaging the tool in operation. The calibration device comprises a stud member and a marker carrier. The stud member is configured to be received by the adapter of the surgical instrument. The marker carrier has a first face and a second face. The marker carrier is connected to the stud member. The stud member has an axis.

[0010] The first face of the marker carrier is provided with a first marker structure positioned in line with the axis of the stud member. The second face of the marker carrier is provided with a second marker structure and a third marker structure. The second marker structure and the third marker structure are positioned offset the axis of the stud member. The calibration device is configured to selectively expose either the first face of the marker carrier or the second face of the marker carrier towards the imaging unit of the surgical instrument, when the stud member is received by the adapter of the surgical instrument.

[0011] The surgical instrument can particularly be embodied for dental and/or cranio- maxillofacial and/or general surgery and, thus, be a dental surgical instrument or a cranio-maxillofacial surgical instrument. [0012] The tool of the surgical instrument can be an intervention member suitable for the intended use of the surgical instrument. For example, the tool can be a drill, a round burr, a saw, a cutter, an osteotome, a scissel or the like.

[0013] The imaging unit can be a camera or a similar arrangement. In particular, it is often beneficial to have three-dimensional information available in surgery such that the camera advantageously is a 3D-camera. For being directed towards the adapter, the imaging unit can be positioned and oriented such that the adapter and advantageously also the tool when being received adapter is in a field of view (FoV) of the imaging unit.

[0014] In connection with the invention, the term “position” may relate to a location in space and may be independent from an orientation. The term “orientation” in contrast may relate to an alignment or direction and/or rotation and may be independent of the position.

[0015] The stud member typically has a cylindric or rod-like portion. For being safely received by the adapter of the surgical instrument, the stud member can be equipped with a coupling structure. For example, such coupling structure may be shaped to allow a snap-in or snap-fit connection, or the like.

[0016] The first and second faces can be essentially plane or flat surfaces or advantageously regularly arched or bent surfaces. They can be embodied as front and back faces of the marker carrier.

[0017] The marker structures can be any structures identifiable by the imaging unit of the surgical instrument. It can particularly comprise a visual pattern allowing to determine position and alignment.

[0018] The first marker structure being positioned in line with the axis of the stud member may be implemented by the axis or a prolonged projection thereof intersecting and, particularly, centrally intersecting the marker structure. The second and third marker structures may be positioned offset the axis by the axis or a prolonged projection thereof not or only peripherally intersecting these marker structures.

[0019] The calibration device according to the invention allows for accurately and efficiently determining an alignment of the imaging unit relative to the adapter by means of the first marker structure and to measure a clearance of the surgical instrument by means of the second and third marker structures. Like this, the invention provides a conveniently applicable device allowing to calibrate the surgical instrument and its tool as to clearance as well as position and orientation relative to each other.

[0020] Preferably, the marker carrier is configured to rotate about the axis of the stud member such that the calibration device is configured to selectively expose either the first face of the marker carrier or the second face of the marker carrier towards the imaging unit of the surgical instrument. Such rotatable marker carrier allows for a convenient and efficient application and, specifically, calibration by means of the calibration device. Moreover, such embodiment allows for efficient manual application of the calibration device.

[0021] For a particular convenient handling and operation, the calibration device preferably is configured to be held in one hand of an operator. For being arranged to be held in one hand, the calibration device can be appropriately dimensioned and/or shaped.

[0022] Preferably, the calibration device comprises a cover configuration arranged to selectively cover either the second marker structure of the marker carrier or the third marker structure of the marker carrier. Like this, the second and third marker structures can safely be in sight of the imaging unit such that an efficient and accurate measurement or determination of any clearance in the surgical instrument can be achieved.

[0023] Preferably, the marker carrier has a body and a housing, wherein the body is arranged in the housing and wherein the first marker structure, the second marker structure and the third marker structure are arranged on the body. The housing may establish a convenient holding of the calibration device by a hand of an operator. As exemplified in more detail below, the housing may also provide the cover configuration mentioned above. Further, the housing may protect the marker structure on the body. The housing can particularly comprise or form a first face portion being a part of the first face of the marker carrier and a second face portion being a part of the second face of the marker carrier.

[0024] Thereby, preferably the housing is made of an obscure material and has a window. The term “obscure” in this connection may relate to not being sufficiently transparent for allowing the imaging unit to properly identify the marker structures. The window can be embodied in the second face portion of the housing. Like this, the imaging unit can be prevented from identifying what is covered by the obscure material in a sufficient quality. The window can be an opening in the housing or a transparent section of the housing. The window particularly is transparent for the imaging unit of the surgical instrument.

[0025] Thereby, the body of the marker carrier and the housing of the marker carrier preferably are movable relative to each other such that, in a second state of the housing relative to the body, the second marker structure is visible through the window and in a third state of the housing relative to the body the third marker structure is visible through the window. The second and third states typically are different positions. By this specific configuration of the marker carrier, the cover configuration mentioned above can efficiently be established by the housing.

[0026] The housing of the marker carrier preferably is laterally movable relative to the body of the marker carrier in a direction essentially perpendicular to the axis of the stud member. Advantageously, the body is arranged in the housing to laterally slide inside the housing between the second and third states.

[0027] Thereby, the body of the marker carrier and the stud member preferably are laterally and axially fixed to each other. In other words, an axial and/or lateral movement of the body relative to the stud member may be prevented by the connection between body and stud member. A rotational movement of the body relative to the stud member about the axis of the stud member may still be possible.

[0028] The housing of the marker carrier preferably is laterally movable relative to the body of the marker carrier between the second state and the third state. Like this, the housing may conveniently be laterally moved by the operator in order to expose and cover the second and third marker structures.

[0029] Thereby, the marker carrier preferably comprises a movement delimiter stopping lateral movement of the housing of the marker carrier relative to the body of the marker carrier on one side at the second state and on the other side at the third state. By such delimiter, the movement of the housing can be precisely be stopped such that the second and third marker structures can correctly be fully exposed and covered, as desired.

[0030] The housing preferably has a further window and, in a first state of the housing relative to the body, the first marker structure is visible through the further window. The further window can be embodied in the second face portion of the housing. The first state may be laterally in between the second and third states.

[0031] Thereby, the marker carrier preferably has a spring arrangement forcing the housing into the first state. Like this, a zero position can be defined in which the first marker structure is visible.

[0032] In another aspect, the invention is a method of calibrating a surgical instrument having an adapter for receiving a tool and an imaging unit directed towards the adapter for imaging the tool in operation. The method comprises the steps of: obtaining a calibration device as described above; receiving the stud member of the calibration device in the adapter of the surgical instrument; orienting the first face of the marker carrier towards the imaging unit; determining an alignment of the imaging unit relative to the adapter by the imaging unit imaging the first marker structure; orienting the second face of the marker carrier towards the imaging unit; and measuring a clearance of the surgical instrument by the imaging unit selectively imaging the second marker structure and the third marker structure.

[0033] The method according to the invention allows for efficiently calibrating the surgical instrument. In particular, alignment of the tool and the rest of the instrument relative to each other can accurately be determined as well as any relevant clearance between the involved parts can be identified and taken into account. More specifically, by determining the alignment of the imaging unit relative to the adapter, a precise conclusion of the alignment and, thus position and orientation of a tool used in operation can be achieved.

[0034] By the method according to the invention and its embodiments described below the effects and benefits of the calibration device according to the invention and its embodiments described above can efficiently be achieved.

[0035] Measuring the clearance of the surgical instrument may involve direct measurement by means of optical data obtained by the camera. It may also involve calculations and determinations in order to transform the optical data or measurements into clearance information. It further may use information about the structure of the surgical instruments such as position and/or type of joints or coupling structures and the like.

[0036] Preferably, in the method, imaging the first marker structure is stereo-imaging the first marker structure as well as selectively imaging the second marker structure and the third marker structure is selectively stereo-imaging the second marker structure and the third marker structure. By such stereo imaging, a three-dimensional evaluation can efficiently be achieved which may increase accuracy of the calibration.

[0037] Preferably, for determining an alignment of the imaging unit relative to the adapter by the imaging unit imaging the first marker structure while the first face of the marker carrier is oriented towards the imaging unit, the imaging unit is rotated. Such rotation allows for precisely determining alignment of the imaging unit relative to the adapter.

[0038] Thereby, the imaging unit preferably is rotated about an axis extending essentially perpendicular to the first face of the marker carrier. More specifically, the imaging unit preferably is rotated clockwise by about 90° and counter-clockwise by about 90°. Such type and extent of rotation allows for a particularly efficient calibration in a relevant range.

[0039] In another further aspect, the invention is a calibration system comprising a surgical instrument and a calibration device as described above. The surgical instrument has an adapter for receiving a tool and an imaging unit directed towards the adapter for imaging the tool in operation.

[0040] By the calibration system according to the invention and its embodiments described below, the effects and benefits achieved by the calibration device and its embodiments described above can efficiently be achieved.

[0041] Preferably, the surgical instrument comprises a handheld motor, a coupling piece and a support member, wherein the imaging unit is fixed to the support member, the support member is mounted to the handheld motor, the coupling piece is releasably coupled to the handheld motor and the coupling piece is equipped with the adapter. Such surgical instrument may be beneficial in many dental or cranio-maxillofacial surgery applications but require proper calibration as can be efficiently achieved by the calibration device. Thus, a combination of such instrument and the calibration device can be particularly advantageous.

[0042] Preferably, the calibration system comprises a processing unit configured to determine an alignment of the imaging unit of the calibration device relative to the adapter of the calibration device by evaluating alignment data collected by the imaging unit of the calibration device when imaging the first marker structure of the calibration device while the adapter of the surgical instrument receives the stud member of the calibration device. By means of such processing unit an automatic calibration process can be achieved at an appropriate accuracy.

[0043] The processing unit can be embodied by any suitably structure such as by an internal or external computer or the like. The term “computer” in this connection can relate to any suitable computing device such as laptop computer, a desktop computer, a server computer, a tablet, a smartphone. The term covers single devices as well as combined devices. A computer can, for example, be a distributed system, such as a cloud solution, performing different tasks at different locations. A computer typically involves a processor or central processing unit (CPU), a permanent data storage having a recording media such as a hard disk, a flash memory or the like, a random access memory (RAM), a read only memory (ROM), a communication adapter such as an universal serial bus (USB) adapter, a local area network (LAN) adapter, a wireless LAN (WLAN) adapter, a Bluetooth adapter or the like, and a user interface such as a keyboard, a mouse, a touch screen, a screen, a microphone, a speaker or the like. Computers can be embodied with a broad variety of components as the components listed here.

[0044] Thereby, the processing unit preferably is configured to measure a clearance of the surgical instrument by evaluating clearance data collected by the imaging unit of the calibration device when selectively imaging the second marker structure of the calibration device and the third marker structure of the calibration device while the adapter of the surgical instrument receives the stud member of the calibration device. Such processing unit allows for an efficient and accurate calibration.

[0045] The processing unit can be embodied to implement the method according to the invention or any of its embodiments described above, or portions thereof. It can execute a computer program or software to perform steps of the method according to the invention.

[0046] For example, the processing unit can be embodied to determine an alignment of the imaging unit relative to the adapter by the imaging unit imaging the first marker structure when the stud member of the calibration device is received in the adapter of the surgical instrument and when the first face of the marker carrier is oriented towards the imaging unit; and to measure a clearance of the surgical instrument by selectively imaging the second marker structure and the third marker structure when the second face of the marker carrier is oriented towards the imaging unit.

Brief Description of the Drawings

[0047] The calibration device according to the invention, the calibration system according to the invention and the method according to the invention are described in more detail hereinbelow by way of exemplary embodiments and with reference to the attached drawings, in which:

Fig. 1 shows a perspective view on an embodiment of a calibration device according to the invention in a first state;

Fig. 2 shows a top view on a first face of the calibration device of Fig. 1 in the first state;

Fig. 3 shows a top view on a second face of the calibration device of Fig. 1 in the first state;

Fig. 4 shows side view of an embodiment of a calibration system according to the invention comprising the calibration device of Fig. 1 and a surgical instrument;

Fig. 5 shows a perspective view on the calibration system of Fig. 4 with the calibration device in the first state;

Fig. 6 shows a perspective view on the calibration system of Fig. 4 with the calibration system in a second state; and

Fig. 7 shows a perspective view on the calibration system of Fig. 4 with the calibration system in a third state.

Description of Embodiments

[0048] In the following description certain terms are used for reasons of convenience and are not intended to limit the invention. The terms “right”, “left”, “up”, “down”, “under" and “above" refer to directions in the figures. The terminology comprises the explicitly mentioned terms as well as their derivations and terms with a similar meaning. Also, spatially relative terms, such as "beneath", "below", "lower", "above", "upper", "proximal", "distal", and the like, may be used to describe one element's or feature's relationship to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass different positions and orientations of the devices in use or operation in addition to the position and orientation shown in the figures. For example, if a device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be "above" or "over" the other elements or features. Thus, the exemplary term "below" can encompass both positions and orientations of above and below. The devices may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein interpreted accordingly. Likewise, descriptions of movement along and around various axes include various special device positions and orientations.

[0049] To avoid repetition in the figures and the descriptions of the various aspects and illustrative embodiments, it should be understood that many features are common to many aspects and embodiments. Omission of an aspect from a description or figure does not imply that the aspect is missing from embodiments that incorporate that aspect. Instead, the aspect may have been omitted for clarity and to avoid prolix description. In this context, the following applies to the rest of this description: If, in order to clarify the drawings, a figure contains reference signs which are not explained in the directly associated part of the description, then it is referred to previous or following description sections. Further, for reason of lucidity, if in a drawing not all features of a part are provided with reference signs it is referred to other drawings showing the same part. Like numbers in two or more figures represent the same or similar elements.

[0050] Fig. 1 shows an embodiment of a handheld calibration device 1 according to the invention. The calibration device 1 comprises a stud member 2 and a marker carrier 3. The stud member 2 has an adapter coupling 21 and a rod portion 22. The adapter coupling 21 is designed for a snap-fit connection and has an asymmetric shape. It is particularly configured to be received by an adapter of an instrument as described in more detail below.

[0051] The marker carrier 3 has a housing 31 and a body 32 partially arranged inside the housing 31. The housing 31 is essentially cuboid shaped, wherein it comprises a plane front face portion 311 and a plane back face portion 313. The front and back side portions 311 , 313 are laterally connected by side walls 315. The housing 31 is made of an obscure material.

[0052] The body 32 has an essentially cuboid shaped portion 322 inside the housing

31 and a trapezoid portion 321 extending outside the housing 31 towards the stud member 2. The rod portion 22 of the stud member 2 is connected to the trapezoid portion 321 of the body 32 such that the body 32 and the stud member 2 are laterally or radially and axially fixed to each other. As described in more detail below, the connection of the rod portion 22 to the trapezoid portion 321 still allows a rotation of the body 32 about an axis 23.

[0053] The cuboid shaped portion 322 of the body 32 is provided with a first marker structure 33. The front face portion 311 of the housing 31 is equipped with a centrally positioned front window 312 through which the cuboid shaped portion 322 of the body

32 is visible. Likewise, the back face portion 313 of the housing 31 is equipped with a centrally positioned back window 314 through which the cuboid shaped portion 322 of the body 32 is visible. In the situation shown in Fig. 1 , the first marker structure 33 is visible through the front window 312. The first marker structure 33 is established by a specific visual pattern formed by lines 331 and dots 332.

[0054] Inside the housing 31 , the body 32 is held on an axle 37. Moreover, between each lateral end of the body 32 and a neighbouring one of the side walls 315 of the housing 31 a helical spring 36 is arranged on the axle 37. The two helical springs 36 are essentially identical such that the body 32 is centrally located inside the housing 31 when no external force is acting on the marker carrier 3 and/or the stud member 2.

[0055] In Fig. 2 the calibration device 1 is shown in a front view. Thereby, it can be seen that the side of the cuboid shaped portion 322 of the body 32 provided with the first marker structure 33 together with the front face portion 311 of the housing 31 establish a first face of the marker carrier 3. The first face of the marker carrier 3 is essentially plane or flat.

[0056] The stud member 2 comprises the central axis 23. In the first state shown in Fig. 2, in which no external force acts on the marker carrier 3 and the stud member 2, the first marker structure 33 is positioned in line with the axis 23 of the stud member 2 and, thus is fully visible through the front window 312. [0057] Fig. 3 shows the calibration device 1 in a back view. The side of the cuboid shaped portion 322 of the body 32 provided with the second marker structure 34 and the third marker structure 35 together with the back face portion 313 of the housing 31 establish a second face of the marker carrier 3. The second face of the marker carrier 3 also is essentially plane or flat.

[0058] In the first state shown in Fig. 3, the second marker structure 34 and the third marker structure 35 are positioned offset the axis 23 of the stud member 2. Hence, the second and third marker structures 34, 35 are only partially visible through the back window 314. In correspondence with the first marker structure 33, the second and third marker structures 34, 35 are established by the same specific visual pattern formed by lines 341 , 351 and dots 342, 352.

[0059] Fig. 4 shows an embodiment of a calibration system 5 comprising the calibration device 1 and a dental surgical instrument 4. The instrument 4 has an adapter 41 designed to receive a tool as intervention member such as a drill, a round burr, a saw, a cutter, an osteotome, a scissel or the like. In the situation of Fig. 4, the adapter 41 receives the adapter coupling 21 of the stud member 2 of the calibration device 1 such that the calibration device 1 is coupled to the surgical instrument 4. In particular, for receiving, the adapter 41 snap-fits adapter coupling 21 .

[0060] The surgical instrument 4 comprises a handheld motor 43, a coupling piece 45, a support member 44 and a stereo-camera 42 as imaging unit. The stereo-camera 42 is mounted to the handheld motor 43 by means of the support member 44. Further, it is directed towards the adapter 41 in order to be capable for imaging the tool received by the adapter 41 in operation

[0061] In Fig. 5 the calibration system 5 is shown with the calibration device 1 in the first state and with the first face of the marker carrier 3 including the front face portion 311 of the housing 31 and the first marker structure 33 on the cuboid shaped portion 322 of the body 32 oriented towards the stereo-camera 42 of the surgical instrument 4. The stereo-camera 42 is ll-like shaped such that an appropriate visibility of the calibration device 1 can be achieved in use.

[0062] The calibration device 1 is arranged to rotate the marker carrier 3 about the axis 23 when the stud member 2 is coupled to the surgical instrument 4, i.e. , received by the adapter 41 . This allows for selectively exposing the first face of the marker carrier 3 or the second face of the marker carrier 3 to the stereo-camera 42.

[0063] In an embodiment of the method according to the invention, when the stud member 2 of the calibration device 1 is received in the adapter 41 of the surgical instrument 4, the first face of the marker carrier 3 is oriented towards the stereo-camera 42 as shown in Fig. 5.

[0064] For determining an alignment of the stereo-camera 42 relative to the adapter 41 , the stereo-camera 42 captures the first marker structure 33. Such rotational movement can be embodied by the stereo-camera 42 being rotated around the handheld motor 43, e.g., by means of a spring mechanism. More specifically, as indicated by the dashed line in Fig. 5, the stereo-camera 42 is rotated about an axis defined by a coupling between the motor 43 and the coupling piece 45. In particular, this axis extends more or less perpendicular to the first face of the marker carrier 3.

[0065] For an appropriate and accurate determination of the alignment of the stereocamera 42 relative to the adapter 41 , the stereo-camera 42 is rotated clockwise by about 90° and counter-clockwise by about 90°. Such rotation can particularly be stepwise, as the coupling between the motor 43 and the coupling piece 45 typically allow stepwise rotation. Also, the rotation can be repeated back and forth until an appropriate set of data is collected. In addition to collecting data for an accurate alignment, the rotational configuration of the stereo-camera 42 relative to the adapter 41 allows to position the stereo-camera 42 in the most suitable position during operation of the surgical instrument 4.

[0066] Fig. 6 shows the calibration device 1 in a second state in which the marker carrier 3 is rotated by 180° about the axis 23 compared to the first state of Fig. 5. Like this, the second face of the marker carrier 3 is oriented towards the stereo-camera 42 (not visible in Fig. 6). In this second state clearance of the surgical instrument 4 is measured by selectively imaging the second marker structure 34 and the third marker structure 35.

[0067] More specifically, for stereo-imaging the second marker structure 34, the housing 31 is manually shifted along the axle 37 to the left against the spring force of the right-hand spring 36 until the complete second marker structure 34 is visible through the back window 314 as indicated by the dashed arrow.

[0068] As shown in Fig. 7, in a third state of the calibration device 1 the housing 31 is manually shifted along the axle 37 to the right against the spring force of the left-hand spring 36 until the complete third marker structure 35 is visible through the back window 314 as indicated by the dashed arrow. In this position of the second state of the marker carrier 3, the stereo-camera 42 is still capturing or imaging.

[0069] By being embodied and operated as shown in Fig. 6 and Fig. 7, the housing 31 of the marker carrier 3 establishes a cover configuration to selectively cover either the second marker structure 34 of the marker carrier 3 or the third marker structure 35 of the marker carrier 3. The marker carrier 3 comprises a movement delimiter stopping lateral movement of the housing 31 relative to the body 32 of the marker carrier on one side at the second state and on the other side at the third state.

[0070] For calibration and particularly for determining the alignment of the stereo-camera 42 relative to the adapter 41 by evaluating alignment data collected by the stereo-camera 42, the calibration system 5 comprises a processing unit. The processing unit is configured to measure the clearance of the surgical instrument 4 by evaluating clearance data collected by the stereo-camera 42 when selectively imaging the second marker structure 34 and the third marker structure 35.

[0071] This description and the accompanying drawings that illustrate aspects and embodiments of the present invention should not be taken as limiting-the claims defining the protected invention. In other words, while the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Various mechanical, compositional, structural, electrical, and operational changes may be made without departing from the spirit and scope of this description and the claims. In some instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the invention. Thus, it will be understood that changes and modifications may be made by those of ordinary skill within the scope and spirit of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. [0072] The disclosure also covers all further features shown in the Figs, individually although they may not have been described in the afore or following description. Also, single alternatives of the embodiments described in the figures and the description and single alternatives of features thereof can be disclaimed from the subject matter of the invention or from disclosed subject matter. The disclosure comprises subject matter consisting of the features defined in the claims or the exemplary embodiments as well as subject matter comprising said features.

[0073] 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. A single unit or step may fulfil the functions of several features recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The terms “essentially”, “about”, “approximately” and the like in connection with an attribute or a value particularly also define exactly the attribute or exactly the value, respectively. The term “about” in the context of a given numerate value or range refers to a value or range that is, e.g., within 20%, within 10%, within 5%, or within 2% of the given value or range. Components described as coupled or connected may be electrically or mechanically directly coupled, or they may be indirectly coupled via one or more intermediate components. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A calibration device (1 ) for a surgical instrument (4) having an adapter (41 ) for receiving a tool and an imaging unit (42) directed towards the adapter (41 ) for imaging the tool in operation, comprising a stud member (2) configured to be received by the adapter (41 ) of the surgical instrument (4); and a marker carrier (3) having a first face and a second face, wherein the marker carrier (3) is connected to the stud member (2), and wherein the stud member (2) has an axis (23), characterized in that the first face of the marker carrier (3) is provided with a first marker structure (33), wherein the first marker structure (33) is positioned in line with the axis (23) of the stud member (2), the second face of the marker carrier (3) is provided with a second marker structure (34) and a third marker structure (35), wherein the second marker structure (34) and the third marker structure (35) are positioned offset the axis (23) of the stud member (2), and the calibration device (1 ) is configured to selectively expose either the first face of the marker carrier (3) or the second face of the marker carrier (3) towards the imaging unit (42) of the surgical instrument (4), when the stud member (2) is received by the adapter (41 ) of the surgical instrument (4).

2. The calibration device (1 ) of claim 1 , wherein the marker carrier (3) is configured to rotate about the axis (23) of the stud member (2) such that the calibration device (1 ) is configured to selectively expose either the first face of the marker carrier (3) or the second face of the marker carrier (3) towards the imaging unit (42) of the surgical instrument (4).

3. The calibration device (1 ) of claim 1 or 2, being configured to be held in one hand of an operator.

4. The calibration device (1 ) of any one of the preceding claims, comprising a cover configuration (31 , 312, 314) arranged to selectively cover either the second marker structure (34) of the marker carrier (3) or the third marker structure (35) of the marker carrier (3).

5. The calibration device (1 ) of any one of the preceding claims, wherein the marker carrier (3) has a body (32) and a housing (31 ), wherein the body (32) is arranged in the housing (31 ) and wherein the first marker structure (33), the second marker structure (34) and the third marker structure (35) are arranged on the body (32).

6. The calibration device (1 ) of claim 5, wherein the housing (31 ) is made of an obscure material and has a window (312).

7. The calibration device (1 ) of claim 6, wherein the body (32) of the marker carrier (3) and the housing (31 ) of the marker carrier (3) are movable relative to each other such that in a second state of the housing (31 ) relative to the body (32) the second marker structure (34) is visible through the window (312) and in a third state of the housing (31 ) relative to the body (32) the third marker structure (35) is visible through the window (312).

8. The calibration device (1 ) of claim 7 or 8, wherein the housing (31 ) of the marker carrier (3) is laterally movable relative to the body (32) of the marker carrier (3) in a direction essentially perpendicular to the axis (23) of the stud member (2).

9. The calibration device (1 ) of claim 8, wherein the body (32) of the marker carrier (3) and the stud member (2) are laterally and axially fixed to each other.

10. The calibration device (1 ) of claim 8 or 9, wherein the housing (31 ) of the marker carrier (3) is laterally movable relative to the body (32) of the marker carrier (3) between the second state and the third state.

11. The calibration device (1 ) of claim 10, wherein the marker carrier (3) comprises a movement delimiter stopping lateral movement of the housing (31 ) of the marker carrier (3) relative to the body (32) of the marker carrier (3) on one side at the second state and on the other side at the third state.

12. The calibration device (1 ) of any one of claims 7 to 11 , wherein the housing (31 ) has a further window (314) and, in a first state of the housing (31 ) relative to the body (32), the first marker structure (33) is visible through the further window (314).

13. The calibration device (1 ) of claim 12, wherein the marker carrier (3) has a spring arrangement forcing the housing (31 ) into the first state.

14. A method of calibrating a surgical instrument (4) having an adapter (41 ) for receiving a tool and an imaging unit (42) directed towards the adapter (41 ) for imaging the tool in operation, comprising: obtaining a calibration device (1 ) according to any one of the preceding claims; receiving the stud member (2) of the calibration device (1 ) in the adapter (41 ) of the surgical instrument (4); orienting the first face of the marker carrier (3) towards the imaging unit (42); determining an alignment of the imaging unit (42) relative to the adapter

(41 ) by the imaging unit (42) imaging the first marker structure (33); orienting the second face of the marker carrier (3) towards the imaging unit (42); and measuring a clearance of the surgical instrument (4) by the imaging unit

(42) selectively imaging the second marker structure (34) and the third marker structure (35).

15. The method of claim 14, wherein imaging the first marker structure (33) is stereo-imaging the first marker structure (33) and wherein selectively imaging the second marker structure (34) and the third marker structure (35) is selectively stereo-imaging the second marker structure (34) and the third marker structure

16. The method of claim 14 or 15, wherein for determining an alignment of the imaging unit (42) relative to the adapter (41 ) by the imaging unit (42) imaging the first marker structure (33) while the first face of the marker carrier (3) is oriented towards the imaging unit (42), the surgical instrument (4) is rotated.

17. The method of claim 16, wherein the imaging unit (42) is rotated about an axis extending essentially perpendicular to the first face of the marker carrier (3).

18. The method of claim 16 or 17, wherein the imaging unit (42) is rotated clockwise by about 90° and counter-clockwise by about 90°.

19. A calibration system, comprising a surgical instrument (4) and a calibration device (1 ) according to any one of the preceding claims, wherein the surgical instrument (4) has an adapter (41 ) for receiving a tool and an imaging unit (42) directed towards the adapter (41 ) for imaging the tool in operation.

20. The calibration system of claim 19, wherein the surgical instrument (4) comprises a handheld motor (43), a coupling piece (45) and a support member (44), wherein the imaging unit (42) is fixed to the support member (44), the support member (44) is mounted to the handheld motor (43), the coupling piece (45) is releasably coupled to the handheld motor (43) and the coupling piece (45) is equipped with the adapter (41 ).

21. The calibration system of claim 19 or 20, comprising a processing unit configured to determine an alignment of the imaging unit (42) of the calibration device (1 ) relative to the adapter (41 ) of the calibration device (1 ) by evaluating alignment data collected by the imaging unit (42) of the calibration device (1 ) when imaging the first marker structure (33) of the calibration device (1 ) while the adapter (41 ) of the surgical instrument (4) receives the stud member (2) of the calibration device (1 ).

22. The calibration system of claim 21 , wherein the processing unit is configured to measure a clearance of the surgical instrument (4) by evaluating clearance data collected by the imaging unit (42) of the calibration device (1 ) when selectively imaging the second marker structure (34) of the calibration device (1 ) and the third marker structure (35) of the calibration device (1 ) while the adapter (41 ) of the surgical instrument (4) receives the stud member (2) of the calibration device (1 ).