Method and system for generating three-dimensional image of at least partial section of row of teeth, computer program product and mirror element

Abstract

To provide a method and system for generating a three-dimensional image of at least a partial section of a row of teeth, computer program product and mirror element.SOLUTION: A stereo camera system for a surgical microscope is provided, the system including a first capturing device and a further capturing device. In the system, S1) respective imaged mirror images S5a, S5b are detected in an image I5a generated by the first capturing device and in an image I5b generated by the further capturing device, the imaged mirror images being provided by a mirror element that is arranged in a capture region of the stereo camera system such that a mirror image of at least a partial section of the row of teeth can be imaged by the first and further capturing devices, S2) a pose of the mirror element is determined, and S3) a three-dimensional image is determined on the basis of at least the imaged mirror images S5a, S5b and the pose of the mirror element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and system for generating a three-dimensional image of at least a partial section of a dentition using a stereo camera system of a surgical microscope, and to a computer program product and a mirror element for generating the three-dimensional image. [Background technology]

[0002] Dental impressions are made, inter alia, in dentistry, in particular in the case of restorative treatment, for example with implants, or in orthodontic treatment. For example, they serve to determine the bite position and / or the state of the jaws, in particular to record this at different points in the treatment. Dental impressions are also important as the basis for planning and manufacturing implants and braces / dental splints.

[0003] It is known that to make a dental impression, a malleable mass is pressed against the dentition. After a waiting time, usually several minutes, the now-dried mass can be removed from the dentition, providing a negative model of the dentition. This negative can then be used to make a model of the dentition, such as a plaster cast, which can be used in the above-mentioned application process. A problem lies in the fact that when the mass is removed from the dentition, minor changes to the negative can occur, leading to a decrease in the accuracy of the model made by the negative. In some situations, this deterioration can require repeated impressions. Similarly, the time required to make the impression, particularly the waiting time described above, and the consumption of materials are usually undesirable aspects.

[0004] So-called intraoral scanners are also known, which are used as an alternative to the illustrated production of impressions using malleable masses. These intraoral scanners use different measurement methods to generate a reconstruction of the dentition surface and also generate a digital model, which can serve as the basis for the applications described below. For example, this model could serve as the basis for the production of dental impressions using additive manufacturing methods, in particular 3D printers. Implants can also be produced in this way, which can then be inserted at the appropriate time.

[0005] Intraoral scanners typically use sensors to generate signals based on a respective physical measurement principle, which are then processed to create a reconstruction or model. For example, known measurement principles for intraoral scanners include confocal laser scanning, triangulation, and tactile measurement. To create a model as complete and accurate as possible, it is necessary to capture images of the entire dentition or entire teeth using the respective sensors. A drawback of known intraoral scanners is that a sensor carrier, equipped with one or more sensors used in each case, must be inserted into the mouth, particularly to capture images of the back side of the dentition, i.e., the side facing the inside of the mouth. This insertion can be very uncomfortable for patients, as it can result in undesirable contact with the lips or other areas of the oral cavity. Patients may also find the deep insertion into the oral cavity, which may be necessary, uncomfortable. Another drawback lies in the fact that the sensor carrier, or the part of the sensor carrier introduced into the mouth, must be cleaned after use, undesirably delaying reuse.

[0006] For the person making the dental impression, i.e., for example, a dentist or orthodontist, such an intraoral scanner in the treatment room represents an additional appliance whose large size disadvantageously reduces the space available in the treatment room. Furthermore, it can be difficult to integrate such an additional appliance into established processes, such as the process of making a dental impression.

[0007] Surgical microscopes are also known. These surgical microscopes are used by the user during treatment to provide an in situ image, especially a magnified image, of the treatment area. So-called surgical stereomicroscopes generally have two separate optical channels for guiding beams, which can provide the user with an impression of the depth of the examination area. For this purpose, the beams guided in the two channels can be captured by the user's eyes through eyepieces. Alternatively or additionally, surgical digital microscopes have two image capture devices, each capturing the beam of one of the optical channels to generate an image. A three-dimensional image is then provided to the user via a suitable display device based on the two images, hereinafter also referred to as corresponding images. Furthermore, other surgical microscopes are known that can optically capture depth information and provide a three-dimensional image of the treatment area. For this purpose, optical detection systems that can provide depth information based on, for example, interferometry, triangulation, time of flight (TOF), or microlens arrays can also be used in surgical microscopes, especially as an alternative to stereoscopic systems.

[0008] To ensure accurate representation, accurate calibration of the stereo camera system is required, and known calibration methods are used to determine internal and external camera parameters, which are then used by the image processing process to ensure accurate representation. Internal camera parameters describe parameters related to each camera / image capture device itself, such as its distortion. External camera parameters describe the relationship, especially the spatial relationship, of the image capture devices and therefore the camera images to each other. Such internal and external camera parameters are known to those skilled in the art.

[0009] Known prior art includes US Pat. No. 5,629,999, which discloses a method and an intraoral scanner for detecting the surface topography of semi-transparent, particularly dental, objects.

[0010] Also known is US Pat. No. 5,629,999, which also discloses an intraoral scanner for three-dimensional scanning of the upper or lower jaw with or without teeth together with the jaw components, particularly in relation to implant prostheses.

[0011] Also known is US Pat. No. 5,629,999, which also discloses an intraoral scanner for digital dental impressions in the dental field and a method for producing a digital dental impression by means of an intraoral scanner.

[0012] Also known is US Pat. No. 5,629,999, which discloses a dental observation device in which a so-called dental microscope is used. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] German Patent Application Publication No. 102020133627A1 [Patent Document 2] German Patent Application Publication No. 102019008510A1 [Patent Document 3] German Patent Application Publication No. 102016121687A1 [Patent Document 4] European Patent Application Publication No. 3689295A1 Summary of the Invention [Problem to be solved by the invention]

[0014] Against this background, the technical challenge is to develop a method and a system for generating a three-dimensional image of at least a partial section of the dentition, as well as a computer program product and a mirror element for generating this three-dimensional image, which allows for a time-fast, accurate and patient-friendly generation of the three-dimensional image, and which should further allow for improved integration into existing application processes and treatment rooms, thereby reducing the costs associated with providing such a system. [Means for solving the problem]

[0015] The solution to the technical problem is evident from the subject matter having the features of the independent claims. Further advantageous configurations of the invention are evident from the dependent claims.

[0016] A method is proposed for generating a three-dimensional image of at least a partial section of the dentition using a stereo camera system of a surgical microscope, which can be useful, in particular in medical applications, for magnifying an object or area to be examined, and thus in particular for representing a partial area of the mouth or a partial area inside the mouth.

[0017] The surgical microscope may include a stereo camera system having a first image capture device and an additional image capture device. Each of these may be designed to generate a two-dimensional image. In this case, the image may be generated with a predetermined number of pixels, and thus a predetermined resolution. For example, the image sensors of the image capture devices may be CMOS or CCD sensors. Obviously, other sensor types may be used. As described above, the surgical microscope may include two optically separated beam paths, in which the first image capture device is positioned and / or designed to generate an image based on a beam directed in the first beam path. The additional image capture device may be positioned and / or designed to generate an additional image based on a beam directed in the additional beam path. In particular, these images may be generated simultaneously. Furthermore, the images generated by the first image capture device and the additional image capture device and subsequently used to generate a three-dimensional image may be referred to as corresponding images. This description also applies to surgical microscopes that use additional optical capture systems to generate three-dimensional images, in addition to or instead of the stereo camera system, particularly to provide depth information. Such optical capture systems have already been described in the introduction above.

[0018] Furthermore, the surgical microscope may comprise at least one optical element for beam guidance and / or beam shaping, which may in particular take the form of a lens element, where the at least one optical element may serve, for example, to generate a magnified image. The optical properties of the surgical microscope, such as magnification, focus, zoom, exposure time, and capture area size, may be adjustable.

[0019] The stereo camera system may be a calibrated stereo camera system. In particular, the above-mentioned internal and external parameters of the stereo camera system can therefore be predetermined, in particular by means of calibration methods known to those skilled in the art. Preferably, the above-mentioned parameters are determined for all operating states of the surgical microscope or for predetermined operating states, where the operating states are characterized by set (adjustable) parameters of the surgical microscope (e.g., zoom, focus, capture area).

[0020] The surgical microscope further comprises at least one eyepiece through which or into which a user can gaze to visually capture an image generated by the surgical microscope. In particular, the user can also view the examination area in three dimensions through the eyepiece. The surgical microscope can comprise at least one objective lens or objective lens system, where the objective lens system includes at least one optical element for beam guidance and / or beam shaping. The eyepiece can be or may be optically connected to the objective lens.

[0021] The surgical microscope may be part of a microscope system, which may include not only the surgical microscope but also a stand for holding the surgical microscope. In this regard, the stand may be designed to allow movement of the surgical microscope in space with at least one degree of freedom, preferably six degrees of freedom, where the degrees of freedom may be translational or rotational. The relevant degrees of freedom may be related to a reference coordinate system. The vertical axis (z-axis) of this reference coordinate system may be oriented parallel to and opposite to gravity. The longitudinal axis (x-axis) and the transverse axis (y-axis) of this reference coordinate system may span a plane oriented perpendicular to the vertical axis. Furthermore, the longitudinal and transverse axes may be oriented perpendicular to each other. Furthermore, the stand may include at least one drive device, e.g., a servomotor, for moving the surgical microscope. The stand may also include means for transmitting forces / moments, e.g., gears and / or coupling units. Thus, the surgical microscope may be mounted or held in a movable manner. Among other things, this allows the user to change the attitude, i.e. the position and / or orientation, of the surgical microscope, for example to change the viewing angle in the examination area or to view other examination areas.

[0022] The operating microscope may in particular be a dental operating microscope, which is designed to generate images for dental applications.

[0023] A partial section of the dentition may in particular comprise at least one tooth or part of one tooth. Teeth may also refer to dentures within the meaning of the present invention.

[0024] According to the present invention, the proposed method comprises the following steps:

[0025] In a first step, in an image generated by a first image capture device of the stereo camera system and in an image generated by a further image capture device of the stereo camera system, respective imaged mirror images are detected, the mirror images being provided by mirror elements arranged in the capture area of the stereo camera system.

[0026] Thus, in particular, before the imaged mirror image is detected, the above-mentioned mirror element can be arranged in a capture area of a stereo camera system, where the first and further image capture devices can image a mirror image of at least one partial section of the dentition. In addition, before the detection, the image capture devices can generate images, in particular corresponding images, which are then used to determine the three-dimensional image, as will be explained in more detail below.

[0027] In particular, the mirror element may have or take the form of a mirror surface that reflects radiation. The image of the mirror surface, i.e., the imaged mirror image, generated by the image capture device is generated by capturing this reflected radiation. Thus, the mirror image generated / provided by the mirror element is sensed by capturing the reflected radiation. Capture by the image capture device generates the imaged mirror image. However, the image generated by the image capture device may include, in addition to the imaged mirror image, additional areas that do not include a mirror image. In other words, the mirror image may be imaged in a partial area of the image generated by the image capture device. In the imaged mirror image, at least one partial section of the dentition is imaged. The mirror element may further include a frame section surrounding the mirror surface. The mirror element may also include a handle section so that the user can position the mirror element in space. The mirror element is preferably a mirror element with a non-curved mirror surface. Preferably, the mirror surface is a circular surface. However, it is also conceivable to use a polygonal mirror surface.

[0028] In a second step, the orientation of the mirror element, in particular the mirror surface, is determined. The orientation includes a translational component and a rotational component. For example, the position of a reference point of the mirror element, e.g., the center of the mirror surface, and the orientation of the mirror element, e.g., the orientation of the normal to the mirror surface, can be determined as the orientation of the mirror element. It is obvious that the positions of multiple reference points of the mirror element or the orientations of multiple subsections can also be determined as the orientation, especially in the case of a curved mirror surface. Exemplary methods for determining the orientation will be described in detail later. The orientation can be determined in a reference coordinate system. For example, this may be the reference coordinate system of a stereo camera system or of a surgical microscope, or the reference coordinate system described above.

[0029] In a third step, a three-dimensional image is determined based at least on the imaged mirror images detected in the (corresponding) images generated by the two image capturing devices and the poses of the mirror elements. For example, a stereo reconstruction method can be used for this purpose, with the imaged mirror images forming the input image for this method. Such methods are known to those skilled in the art. In particular, such methods can determine corresponding pixels in the two input images. For example, such corresponding pixels or pixel sets can be determined using feature matching methods. Corresponding methods and features are known to those skilled in the art. Exemplary features are known as SIFT features, i.e., features for / of scale-invariant feature transforms. However, it is obvious that other methods, such as variational methods or AI-based methods, can also be used for the determination. Next, three-dimensional coordinates can be determined in the reference coordinate system described above for the object points or object sections imaged at the corresponding pixels or pixel sets. This can also be referred to as reconstruction, in which a corresponding reconstruction method is performed based on the poses of the mirror elements. In particular, at least one method step of the reconstruction method can be performed based on the poses. In particular, the pose can be represented by at least one parameter, and at least one method step is performed based on or takes into account the parameter during execution. Preferably, a stereo triangulation reconstruction method is performed to determine the three-dimensional image. Stereo triangulation reconstruction methods are known to those skilled in the art. In this case, the projection matrix used during reconstruction, which describes the perspective transformation of three-dimensional object coordinates in a reference coordinate system into two-dimensional image coordinates, can be determined based on the pose of the mirror elements and the (known) laws of reflection. In other words, the pose of the mirror elements affects the projection matrices of both image capture devices and therefore also affects the stereo triangulation reconstruction performed based on or in response to these projection matrices. For example, so-called homogeneous or so-called non-homogeneous methods may be applied to determine the three-dimensional coordinates. In particular, a rectification method for correcting or removing non-linear distortions in the image can be performed before the three-dimensional image is determined.

[0030] The proposed method advantageously allows for simple, accurate and patient-friendly generation of three-dimensional images, in particular intraoral scanning, compared to the existing methods described above, since generally only small-sized mirror elements need to be placed inside the mouth to capture a partial section of the dentition and image it in three dimensions.

[0031] The proposed method is used in particular to generate a three-dimensional image of the back side of the dentition and / or the occlusal or chewing surface of the dentition. The back side of the dentition may in particular refer to the side of the dentition facing the inside of the mouth. A three-dimensional image of the front side of the dentition or of a partial section of this dentition can be determined without carrying out the first and second steps described above. Thus, in particular, the three-dimensional image can be determined based on corresponding images generated by an image capture device, where known methods for stereo reconstruction can in particular be used. The image capture device generating the images can be positioned outside the oral cavity, i.e. extraorally. Therefore, the method can also be referred to as extraoral scanning.

[0032] For example, three-dimensional images can be generated in the form of CAD data, for example in STL format.These three-dimensional images can then be visualized, for example by outputting them on a display device.The three-dimensional images can also be used in further processes, for example in CAD / CAM processes, for example to make dental impressions.

[0033] In a further embodiment, the three-dimensional image is further determined depending on at least one optical property of the mirror elements. In this regard, the at least one optical property may be predetermined. Alternatively, the at least one optical property may be determined in a further step of the proposed method, in particular in an image-based manner, i.e., by evaluating at least one image of the mirror elements. In particular, the optical property of the mirror elements may be a magnification or reduction property. It is obvious that other optical properties of the mirror elements that affect the mirror imaging may also be taken into account. For example, the optical property may be represented by the described projection matrix. This advantageously results in a highly accurate registration of the generated three-dimensional image.

[0034] Alternatively or additionally, the three-dimensional image is further determined depending on at least one imaging property of the surgical microscope. In particular, the imaging property may be a set magnification (zoom), a set focus, or any other imaging property that influences the imaged mirror image. This imaging property may also be represented by the described projection matrix. This also advantageously provides the possibility to generate three-dimensional images with high accuracy.

[0035] In a further embodiment, a (corresponding) image of the virtual image capturing device is determined based on at least the orientation of the mirror element, wherein at least one corresponding section of the dentition reflected in the catadioptric system is imaged in such an image of the virtual image capturing device. Furthermore, the three-dimensional image is determined based on the images of the virtual image capturing device, in particular the corresponding section in each image.

[0036] A catadioptric system refers to a relay optical system comprising at least mirror elements and optical elements of an image capture device, such as an objective lens. In particular, the catadioptric system may comprise optical elements of an objective lens of a surgical microscope. The beam path through the catadioptric system can be determined based on the optical properties of the optical elements of the catadioptric system, which are known or determinable in advance, as well as on the orientation of the mirror elements and known laws of optics.

[0037] A virtual image capture device is a mathematical or physical model of an image capture device, which can be evaluated, in particular with the aid of a computer. Depending on the model, it is possible to generate or calculate a virtual image generated by the virtual image capture device, in particular by computer-implemented calculation of pixels. This virtual image depends, inter alia, on the parameters of the (modeled) image capture device and on the attitude of the (modeled) image capture device. These parameters, in particular the external and / or internal parameters, of the virtual image capture device may depend on the optical properties of the mirror elements. If the mirror surface is, for example, not curved and does not have magnification properties, the internal parameters of the virtual image capture device may be equal to the internal parameters of the modeled image capture device.

[0038] In particular, the pose of the virtual image capturing device can be determined based on the pose of the mirror elements, such that the virtual image of the virtual image capturing device in this pose images a non-reflected section of the dentition that is reflected by the catadioptric system and thus also reflected by the mirror elements, which non-reflected section represents the corresponding section. In addition to the pose of the mirror elements, the generation of such a virtual image also depends on (further) properties of the catadioptric system, for example the set zoom of the objective lens.

[0039] A three-dimensional image can then be determined based on the virtual image, particularly of the corresponding section, using methods known to those skilled in the art. Exemplary methods have been described above. Such methods can, in particular, take into account the characteristics of the catadioptric system and thus the orientation of the mirror elements. In other words, the reflected image can be converted into a non-reflected image, and then the three-dimensional image can be generated based on the non-reflected image. This advantageously allows for an accurate and computationally easily implemented determination of a three-dimensional image that can be generated with particularly high precision.

[0040] In a further embodiment, the pose is determined by evaluating at least one characteristic of the imaged mirror image or the imaged mirror element (or a section thereof). The at least one characteristic can be determined in an image-based manner, in particular by evaluating the image generated by the respective image capture device. In particular, the imaged mirror surface or the imaged mirror element can be recognized in such an image, for example, by an object recognition method known to those skilled in the art. For example, the object recognition method may be a segmentation method. Thus, for example, the imaged mirror surface, the imaged frame section, or the imaged handle section can be recognized in an image-based manner. For example, it is possible to form a section of the mirror element, for example, the frame section, from a material with predetermined optical properties, for example, from a matte material, in order to enable reliable detection of this section in the image. Alternatively, detection can also be performed by a user selecting, for example by means of a suitable input device, an image area in which the mirror image or the section to be detected is imaged.

[0041] The property of the imaged mirror image or imaged mirror element may be a geometric property of the imaged mirror image, e.g., a dimensional property such as a dimensional variable. The dimensional variable may be a width, a height, a diameter, or any other dimensional variable. Furthermore, the property may be a shape property, e.g., a geometric shape such as a circle, an ellipsoid, a rectangle, or any other geometric shape. In particular, a shape factor may be determined that represents a relationship between the imaged shape and the actual shape, and the pose is determined based on the shape factor.

[0042] As explained above, the pose of a mirror element can affect its imaging by an image capturing device. Therefore, the pose can also affect how the actual properties of a mirror image or mirror element are mapped to the properties of the imaged mirror image or mirror element. If the relationship between the actual properties and the properties of the imaged mirror image can be described by a transformation matrix that depends on the pose, the pose can be determined based on the actual properties and the properties of the imaged mirror image or mirror element. The actual properties may be already known or determinable from a model, e.g., a model of the mirror element, particularly a CAD model.

[0043] If the mirror element or part thereof, in particular the mirror surface, is circular and the imaged mirror image is elliptical, the pose can be determined based on the properties of the ellipse, such as the orientation and length of the ellipse axis, and on the properties of the circular mirror element that are known in advance, in such a way that the known properties are transformed into properties of the imaged mirror image. If polygonal mirror elements, in particular regular polygonal mirror elements, are used, the pose can be determined at least in part by the ratio of the lengths of the edges in the image and the relative positions of the edges in the image with respect to each other.

[0044] Furthermore, the characteristic may be the orientation of the imaged mirror image or the imaged mirror element or part thereof in the image coordinate system. For example, the position may be determined as the position of a reference point, e.g., a geometric center. For example, the orientation may be determined as the orientation of an axis of a reference section. For example, if the mirror element includes a handle section, the handle section may be recognized in the image, and its position and / or orientation may be determined. For example, the orientation of the longitudinal axis of the handle section may be determined.

[0045] If the attitude is determined by evaluating at least one characteristic of the imaged mirror image or of the imaged mirror element, this advantageously results in a simple determination of the attitude, since the image generated in any case can be evaluated for the purpose of determining the attitude.

[0046] Alternatively, the orientation may be determined based on markers. To this end, the mirror element may include or take the form of at least one marker element for determining the orientation of the mirror element. Obviously, the mirror element may also include or take the form of multiple markers, and the orientation of the mirror element may be determined based on the previously known relative positions and / or dimensioning of these markers.

[0047] The marker elements may be active or passive. They may be designed to be captured by a capture device. In particular, the capture device may be an image capture device. Accordingly, in this case, the marker elements may be optically captureable marker elements. For example, the optically captureable marker may include a predetermined pattern that allows the pose of the marker, and therefore the pose of the mirror element, to be determined. For example, such an optically captureable pattern may take the form of a QR code. Furthermore, such optically captureable markers may be reflective marker elements, designed to reflect, for example, radiation from a predetermined wavelength range, such as the infrared wavelength range. The image capture device that optically captures the marker elements may be an image capture device of a stereo camera system or a different image capture device. If the mirror element includes multiple marker elements, the pose of the mirror element may also be determined based on the relative positions of the imaged marker elements in the image. Furthermore, the pose of the mirror element may be determined, at least in part, by determining at least the stereoscopic pose of the marker elements.

[0048] The image capture device and the marker elements can be used to perform what is known in particular as monoscopic pose determination. In this case, the pose can be determined by evaluating a two-dimensional image, in particular exactly one two-dimensional image of exactly one image capture device. In particular, an evaluation of the intensity values of the pixels of the two-dimensional image can be performed to determine the position. Such methods of image-based position detection using exactly one image capture device and / or based on exactly one two-dimensional image are known to those skilled in the art. However, if a stereo camera system is used, the pose can also be determined by evaluating corresponding images of the image capture device.

[0049] In particular, the pose can thus be determined by optical tracking methods, in particular using an image capture device, which may be marker-based tracking, in which case specific visually or optically captureable marker elements, such as QR codes or optical patterns of different designs, are used to determine the pose.

[0050] Alternatively, in particular in determining the above-mentioned pose by evaluating at least one property of the imaged mirror image or the imaged mirror element, markerless tracking methods can also be applied, in which features are captured and used to determine the pose.

[0051] However, instead of optically capturable marker elements, it is also possible to use marker elements that can be capturable in other ways to determine the orientation of the mirror element, for example magnetically, capacitively, inductively or in a radio-based manner, for example the marker elements may be designed as RFID tags.

[0052] The mirror element may also include an orientation sensor, such as an initial sensor or a GNSS sensor, and the orientation may be determined based on the output signal of such a sensor. In such an embodiment, the surgical microscope may include or be connected to a receiving device for the output signal generated by the orientation sensor.

[0053] Obviously, it is also possible to determine pose using a hybrid method, which combines at least two of the methods for determining pose described above.

[0054] Marker-based pose determination advantageously provides very accurate pose determination, resulting in accurate three-dimensional images.

[0055] The marker elements may be identifiable, in particular bijectively. For example, a pattern of optically identifiable markers may encode the marker's identity. Thus, the marker elements or mirror elements may be made identifiable by incorporating the marker elements. The thus determinable identity may be assigned to the properties of the mirror elements, in particular the optical properties described above. This assignment, as well as the identity and the properties, may be stored in a retrievable or readable manner, for example in a memory device. This advantageously allows the optical properties of the mirror elements to be simply determined.

[0056] For the purpose of marker-based pose determination, in a further embodiment, at least one marker element is imaged by at least one image capture device of the stereo camera system or by a further image capture device. The at least one marker element is arranged on or formed by a mirror element. The pose is then determined based on at least one property of the imaged marker element, as already explained above. The further image capture device may in particular be a tracking camera or an environmental camera of the microscope system, which takes a different form from the image capture device of the stereo camera system. This tracking camera or environmental camera can in particular serve for marker-based tracking of the further instrument. In any case, the use of a surgical microscope or a microscope system with a surgical microscope advantageously results in the simplest possible integration of optical pose determination.

[0057] In a further embodiment, the focal position of the surgical microscope is set based on the orientation of the mirror element. In particular, this allows the focal position to be set on a point on the mirror surface or on a point spaced a predetermined distance from the mirror surface. In particular, the predetermined distance depends on the depth of field of the surgical microscope and can be smaller than the depth of field range. In this case, the depth of field is known or can be determined in advance. As a result, a high imaging quality can be obtained for the mirror image, which advantageously increases the accuracy of the generated three-dimensional image.

[0058] In particular, this also allows the imaged mirror image to be more easily and reliably detected in the image of the image capture device.

[0059] In a further embodiment, the radiation captured to generate the images of the stereo camera system is filtered. In a preferred embodiment, the filtering is polarization filtering. However, it is clear that other radiation filters may also be used. Advantageously, this allows unwanted reflections from the tooth surfaces to be suppressed in the images, which further improves the accuracy of the generated three-dimensional image. In this case, polarization filtering allows for the greatest possible or complete suppression of reflections.

[0060] In a further embodiment, the filter elements are arranged in the illumination beam path and / or in the imaging beam path of the surgical microscope. In particular, a respective filter element can be arranged in each imaging beam path. In either case, a good structural integration of the filter elements in the surgical microscope or in the microscope system is achieved, which allows the generation of highly accurate three-dimensional images.

[0061] Further alternatively or additionally, a filter element may be arranged on the mirror element. For example, the filter element may be arranged on the mirror surface of the mirror element. Advantageously, the mirror element provides the desired filter characteristics, and as a result, there is no need to integrate additional filter elements in the surgical microscope or microscope system to generate high-precision three-dimensional images.

[0062] In a further embodiment, at least one partial section of the dentition is illuminated by radiation having predetermined radiation characteristics. For example, such radiation characteristics may be (a) a predetermined wavelength of the radiation used for illumination purposes, a predetermined intensity, or, in a preferred embodiment, predetermined polarization or further characteristics of the radiation used for illumination purposes. Advantageously, this also allows for reduced reflections from the tooth surfaces, which further provides a high degree of accuracy in the generated three-dimensional image.

[0063] In a further embodiment, the images generated by the stereo camera system are filtered, and the three-dimensional image is determined based on at least the filtered images. In particular, the filtering can be performed to reduce unwanted reflections in the image. However, in general, the filtering can also serve to improve the image quality, which further advantageously improves the accuracy of the three-dimensional image. An exemplary method of filtering for reflection suppression is the so-called tone mapping method.

[0064] For example, teeth can be temporarily stained during image capture, after which color filtering can be performed, for example, reducing color components in the image that differ from the color of the staining.

[0065] In a further embodiment, at least one quality criterion of the three-dimensional image is determined. Furthermore, if the quality criterion is below a predetermined threshold, user information is generated. Therefore, in this case, the quality criterion is selected to be proportional to the quality of the three-dimensional image. The user information can be output to the user via an output device, for example, via an optical or acoustic output device. This can be part of the surgical microscope or part of the microscope system.

[0066] For example, it can be determined whether the point density in a predetermined section of the generated three-dimensional image is below a predetermined threshold. Since it may be desirable to perform a more accurate reconstruction with a higher density in at least this subsection, user information can be generated in such cases. In particular, the determined quality criterion, for example the point density, can be generated as part of the user information.

[0067] Furthermore, if the quality metric is determined in a sub-region specific manner, information about the sub-region, in particular its pose, can be generated as part of the user information.

[0068] This advantageously ensures high accuracy of the generated three-dimensional image, since user information is generated in cases where there is a possibility of undesirably low quality, and the method is, for example, performed again for partial areas in which an unacceptably low quality criterion has been determined.

[0069] A system for generating a three-dimensional image of at least a partial section of a dentition is also proposed, wherein the system comprises a stereo camera system and at least one evaluation device, the stereo camera system comprising a first image capture device and a further image capture device, the system being adapted to perform a method according to one of the embodiments described in the present disclosure, in particular a) detecting a mirror image imaged in an image generated by a first image capture device and in an image generated by a further image capture device, the mirror image being generated by a mirror element, the mirror element being positioned in a capture area of the stereo camera system and reflecting at least one partial section of the dentition; b) determining the pose of the mirror element; c) determining a three-dimensional image based at least on the imaged mirror image and the orientation of the mirror element; is configured to run

[0070] The evaluation device may take the form of or comprise a computing device, which may further comprise or take the form of a microcontroller or an integrated circuit, in which case the evaluation device is capable of performing at least one of steps a), b) and c), but preferably all of these steps.

[0071] The system may be a component of a surgical microscope or a microscope system, which may comprise a stereo camera system and an evaluation device. Furthermore, the system may comprise a capture device for capturing marker elements. Furthermore, the system may comprise a filter element for filtering radiation responsible for generating the image of the stereo camera system. Furthermore, the system may comprise an illumination device for illuminating the partial section with a predetermined radiation characteristic. Furthermore, the system may comprise an output device for user information.

[0072] The system advantageously allows the implementation of a method according to one of the embodiments described in the present disclosure, with the advantages also already described.

[0073] In a further embodiment, the system comprises a mirror element positioned in the capture area of the stereo camera system.

[0074] Also proposed is a computer program product having a computer program, wherein the computer program comprises software means for performing one, some or all steps of the method according to one of the embodiments described in the present disclosure, in particular from the set comprising step 1, step 2 and step 3, when the computer program is executed by or in a computer or in an automation system. In other words, the method can be a computer-implemented method.

[0075] A mirror element for generating a three-dimensional image of at least a partial section of the dentition is also proposed. According to the invention, the mirror element comprises or forms at least one marker element for determining the orientation of the mirror element. Alternatively or additionally, the mirror element comprises or forms at least one filter element for filtering reflected radiation. This and the corresponding advantages have already been explained above.

[0076] The present invention will now be described in detail based on exemplary embodiments. [Brief explanation of the drawings]

[0077] [Figure 1] 1 shows a schematic flow chart of a method according to the present invention. [Figure 2] 4 shows a schematic flow chart of a method according to the invention in a further embodiment; [Figure 3] 1 shows a schematic block diagram of a system according to the present invention; [Figure 4a] 1 shows a mirror element in a first position. [Figure 4b] 4b shows the mirror element shown in FIG. 4a in a further position; [Figure 4c] 4b shows the mirror element shown in FIG. 4a in a further position; [Figure 4d] 4b shows the mirror element shown in FIG. 4a in a further position; [Figure 5] 1 shows a schematic diagram of a mirror element according to the present invention; [Figure 6] FIG. 1 shows a schematic block diagram of a virtual image capturing device. [Figure 7a] 1 shows a schematic diagram of a stereoscopic capture of a dentition without mirror elements. [Figure 7b] FIG. 1 is a schematic diagram of the stereoscopic capture of a dentition by mirror elements. DETAILED DESCRIPTION OF THE INVENTION

[0078] Hereinafter, the same reference numerals refer to elements having the same or similar technical features.

[0079] FIG. 1 shows a schematic flow chart of a method according to the present invention for generating a three-dimensional image A of at least a partial section of dentition Z (see FIG. 3) using a stereo camera system 1 of a surgical microscope 2. Prior to a first step S1 of the method, a mirror element 3 is positioned in the capture area 4 of the stereo camera system 1 so that a mirror image of at least a partial section of dentition Z can be imaged by a first image capture device 5a and by a further image capture device 5b of the stereo camera system 1 (positioning step SA). Following this positioning, the first image capture device 5a and the further image capture device 5b each generate respective images I5a, I5b, which may be referred to as corresponding images (image generation step SB). These may be generated from different positions and / or with different orientations. Furthermore, they may be generated simultaneously or with a predetermined maximum time offset. Next, in a first step S1 of the method, an imaged mirror image S5a is detected in the image I5a generated by the first image capture device 5a, for example, using an object recognition method. In addition to the partial area in which the mirror image provided by the mirror element 3 is imaged, the image I5a generated by the first image capture device 5a may in this case contain further partial areas, for example, which image other partial sections of the dentition Z, in particular partial sections not reflected by the mirror element 3. A correspondingly imaged mirror image S5b is also detected in the image I5b generated by the further image capture device 5b. The thus detected imaged mirror images S5a, S5b form input variables for determining the three-dimensional image A. In a second step S2 of the method, the pose P, i.e., the position and / or orientation, of the mirror element 3 is determined in a reference coordinate system. The reference coordinate system may be the coordinate system of the surgical microscope 2 serving as a reference or the coordinate system of the stereo camera system 1 serving as a reference. Obviously, other reference coordinate systems are also conceivable. In addition to the imaged mirror images S5a, S5b, the pose P forms a further input variable for determining the three-dimensional image A.

[0080] Then, in a third step S3, a three-dimensional image A is determined based on at least the imaged mirror images S5a, S5b and the pose P of the mirror element 3, for example via or using stereo reconstruction, as already explained above.

[0081] In this connection, it should be mentioned that the order of the first step S1 and the second step S2 depicted in Fig. 1 is not essential: in particular, it is possible to determine the pose P simultaneously with or before the detection of the imaged mirror images S5a, S5b.

[0082] The three-dimensional image A can further be determined as a function of at least one optical property of the mirror element 3. This optical property then forms a further input variable for the third step S3. In this regard, the optical property may be predetermined. In this case, it is possible to identify the mirror element, in particular, by assigning at least one optical property to an identification of the mirror element 3, preferably in one-to-one correspondence. Depending on this assignment, the optical property can then be determined using the determined identification of the mirror element 3, which can be retrieved, for example, from a database that can be stored in a storage device and represents the assignment of the identification to the at least one optical property. Such an identification step, not shown in FIG. 1, can be performed before the third step S3. Preferably, an image-based identification of the mirror element can be performed, for which purpose, at least one of the generated images I5a, I5b in which the mirror element 3 is imaged is evaluated. For example, although not necessarily, the identification can be performed simultaneously with the determination of the pose in the second step S2. This identification can be performed by evaluating at least the properties of the imaged mirror element or in a marker-based manner. This will be explained in more detail below in relation to determining the pose P.

[0083] Alternatively or additionally, before the third step S3, a determination of an imaging property of the surgical microscope 2, for example the currently set zoom, can also be carried out. This imaging property of the surgical microscope 2 can then form a further input variable for the third step S3. Thus, the three-dimensional image A can further be determined depending on at least one optical property of the mirror element 3 and / or depending on at least one imaging property of the surgical microscope 2.

[0084] Determining the pose P of the mirror element 3 in the second step S2 can be performed in an image-based manner, in particular by evaluating at least one property of the imaged mirror image S5a, S5b or the imaged mirror element 3. The property may be a dimensional property. The property may also be a shape property, as explained above. In particular, the property in the image S5a, S5b can be determined and compared with a previously known property of the mirror image or mirror element 3 in a reference position (see, for example, FIG. 4a), in particular including a mathematically determinable image of the mirror image or mirror element 3 in this reference position. The pose P of the mirror element 3 can then be determined from the deviation between the actual property in the image and the previously known property thus determined. For example, it is possible to determine a transformation used to convert the image of the mirror image or mirror element in the reference position to the actual image, said transformation comprising information about the current pose P of the mirror element 3.

[0085] Alternatively, the determination of the attitude P may be performed in a marker-based manner. For this purpose, it is possible to capture a marker element, which in the exemplary embodiment of FIG. 5 is shown as an optically captureable marker element 6. Such a marker element 6 may be an active marker element, i.e., a marker element that consumes energy to generate a captureable signal, or a passive marker element that can be captured without consuming energy. The optically captureable marker element 6 shown in FIG. 5, which takes the form of a barcode or optical pattern, is an example of a passive marker element. However, it is also obvious that the optically captureable marker may also be an active marker that, for example, consumes energy to generate an optically captureable signal. However, instead of the optically captureable marker element 6, a marker element that can be captured in another form, for example a magnetically captureable marker element, may also be used. In this case, the marker element may be arranged in or on the mirror element 3, where the attitude P of the mirror element can then be determined based on the captured marker element.

[0086] If at least one marker element is an optically captureable marker element 6, such as the passive optically captureable marker element 6 shown in Figure 5, the at least one marker element may be imaged by at least one image capturing device 5a, 5b of the stereo camera system 1 or by a further image capturing device (not shown) in order to determine the pose P, and the pose P may then be determined depending on at least one property of the imaged marker element. In this case, the pose P can only be determined after the respective images I5a, I5b have been captured.

[0087] It is also conceivable that the focal position of the surgical microscope 2 is set based on the orientation P of the mirror element 3. In this case, the images I5a, I5b, which are evaluated for determining the three-dimensional image A, can be generated after the orientation P has been determined. If the orientation P is determined in an image-based manner, the images useful for determining the orientation P can be generated before the orientation P has been determined, whereupon the focal position is then set based on the orientation P, and the images I5a, I5b useful for detecting the imaged mirror images S5a, S5b are then generated.

[0088] FIG. 2 shows a schematic flowchart of a method according to a further embodiment. In contrast to the embodiment shown in FIG. 1, in a further image generation step SBV, images I5a, I5b, i.e., corresponding images, from the front side 7 of the dentition Z are further generated, whereupon a three-dimensional partial image A1 of the front side is generated based on these images I5a, I5b in a reconstruction step SRV. The method shown in FIG. 1 is then carried out, whereby the image A generated is a partial image A2 of the back side 8 of the dentition Z, or of the chewing surfaces 9 of the teeth in the dentition Z. The partial images A1, A2 are fused / merged in a fusion step FS to form the resulting image A of the dentition Z. For this purpose, in particular, corresponding points in the three-dimensional partial images A1, A2 can be detected to fuse the partial images A1, A2. For this purpose, it may be necessary to scale the structures imaged in at least one of the partial images A1, A2, in particular the structure in the partial image A2 of the back side 8. Such scaling can be performed in particular depending on the distance between the mirror element 13 and the reflected section of the dentition Z. This distance can be determined in particular based on the pose P of the mirror element 13. This distance can also be determined based on different focal positions of the stereo camera system 1, as will be explained in more detail below. The partial images A1, A2 and the resulting image A can preferably be provided in STL data format, which allows these images to be advantageously used in further processes, in particular in CAD / CAM processes. The resulting three-dimensional image A or the partial images A1, A2 can also be displayed to the user via a suitable display device. It is also possible to overlay information, such as color information, on the displayed image.

[0089] Figure 3 shows a schematic block diagram of a system according to the invention for generating a three-dimensional image A of at least a partial section of a dentition Z, where the system comprises a stereo camera system 1 and at least one evaluation device 10. The system is configured to perform at least steps S1, S2, S3 shown in Figures 1 and 2. It will be appreciated that the system can also be configured to perform steps SBV, SRV, FS shown in Figure 2. In this case, the steps or at least some of them can be performed by the evaluation device 10.

[0090] FIG. 3 schematically illustrates the capture area EB of the image capture devices 5a, 5b and the optically separated beam paths 11a, 11b of the surgical microscope 2. The illumination device of the surgical microscope 2, which can illuminate the dentition Z, is not shown. In this case, the illumination device can generate radiation with predetermined radiation characteristics, particularly predetermined polarization characteristics. The radiation reflected by the dentition Z reaches the image sensors of the image capture devices 5a, 5b via the beam paths 11a, 11b, thereby generating images I5a, I5b of the dentition Z, which can be evaluated by the evaluation device 10. Also shown is the mirror element 3, which reflects the beam from the dentition Z, particularly its back side 8. This reflected radiation also reaches the image sensor via the beam paths 11a, 11b and is imaged there as a mirror image. This image can then be detected as a mirror image by the evaluation device 10.

[0091] The radiation captured to generate the images I5a, I5b of the stereo camera system 1 can be filtered. This can be done, for example, by filter elements, which are arranged in each case in the beam paths 11a, 11b. Furthermore, filter elements may be arranged in the illumination beam path of an illumination device (not shown) of the surgical microscope 1. Furthermore, filter elements may be arranged on / at the mirror element 3. In particular, such filter elements may be polarizing filter elements. It is also possible for the evaluation device 10 to filter the images I5a, I5b generated by the image capture devices 5a, 5b, for example to suppress reflections.

[0092] Figure 4a shows an image of a mirror element 3 in a reference position. The mirror element 3 comprises a handle section 12 and a circular mirror section 13, which further comprises a mirror surface 14. For example, the centre of this mirror surface 14 is the reference point P3 of the mirror element 3. A coordinate system at rest relative to the mirror is depicted, which has longitudinal, horizontal, y and vertical axes z3 (see Figure 4b).

[0093] Figure 4b shows an image of the mirror element 3 in a position P, which occurs when the mirror element 3 is rotated about its longitudinal axis x3a from the reference position shown in Figure 4a. It is clear that the round mirror surface 14 shown in Figure 4a is now imaged as an ellipse. Depending on the orientation and length of the major and minor axes of this ellipse, which can be detected, for example, by object recognition methods, it is possible to determine the rotation angle by which the mirror element 3 has rotated about its longitudinal axis x3a, and again the current position P of the imaged mirror element 3 shown in Figure 4b.

[0094] In a similar manner, Figures 4c and 4d show the imaged mirror element 3 rotated about the horizontal axis y3 (Figure 4c) or about the vertical axis z3 (Figure 4d) relative to the reference position shown in Figure 4a. For example, the corresponding rotation angle can be determined based on the orientation of the vertical axis x3 (Figure 4d) and / or based on the orientation and length of the axes of the elliptical image of the mirror surface 14.

[0095] It can be seen from Figures 4a to 4d that a shape-based determination of the pose P of the mirror element 3 can be made, that is, the shape characteristics of the imaged mirror element 3 can be determined and then the pose P can be determined based on these characteristics.

[0096] It is also clear that the center of the mirror surface 14 can be detected. If the focus is directed not only at the point reflected at the mirror surface 14, for example at the center, but also at the non-reflected edge of the mirror surface 14, it is possible to ascertain the distance of the mirror surface 14, and in particular the reflecting point, from the dentition Z by the difference in focus position.

[0097] In particular, it is possible to determine the difference between the focal position when the stereo camera system 1 or the surgical microscope 2 is focused on a point of an edge that is not reflected, e.g., a point of the frame section 13, and the focal position when the stereo camera system 1 or the surgical microscope 2 is focused on a point of the object that is reflected on the mirror surface 14, e.g., a point that is reflected on the center of the mirror surface 14. This difference in focal positions can represent the distance of the mirror element 13 from the object, in this case, a point on the dentition Z, and the distance can therefore be determined based on this difference. Furthermore, the distance can also be determined based on the orientation P of the mirror element 13. This distance information can be used for scaling within the described stereo reconstruction, in particular to match the magnification when reconstructing a reflected section, e.g., the back side 8 of the dentition Z, to the magnification when reconstructing a non-reflected section, e.g., the front side 7 of the dentition Z, i.e., to perform scaling.

[0098] 5 shows a schematic diagram of a mirror element 3 according to the present invention. The mirror element 3 includes or forms, on the handle section 12, marker elements 6 in the form of optically captureable bar codes. The mirror element 3 also includes, on the frame section 13 of the mirror surface 14, further optically captureable marker elements 6 in the form of bar codes. These can be captured in an image of the mirror element 3, which marker elements allow, among other things, to identify the mirror element 3 and to determine the pose P of the mirror element 3. In particular, each marker element 6 can be detected in the case of the mirror element 3 shown in FIG. 5, after which the pose P can be determined by the relative placement of the marker elements in the image.

[0099] Figure 6 shows a schematic diagram of the image capture device 5 (see Figure 3) of the stereo camera system 1 and the mirror element 3 arranged in the capture area EB of the image capture device 5. The object point OP to be imaged, e.g. a point on the surface of the dentition Z (see Figure 3), is also shown. The normal n of the mirror surface 14 of the mirror element 3 is also shown.

[0100] A virtual image capture device 15 is also represented. The (virtual) image of this virtual image capture device 15 can be determined by evaluating a mathematical or physical model. In particular, the model is determined in such a way that a virtual image is generated, which images, in a non-reflective manner, object points OP corresponding to sections of the dentition Z, i.e., in particular sections reflected in a catadioptric system, however taking into account the properties of the catadioptric system. Based on the virtual image, a three-dimensional image A can then be determined using methods known to those skilled in the art, for example via or using stereo reconstruction, as has already been explained above.

[0101] Figure 7a shows a schematic illustration of the stereoscopic capture of the dentition Z by two image capture devices 5a, 5b of a stereo camera system 1 without a mirror element 3. The capture of the front side 7 of the dentition Z is shown, for example, as performed in a further image generation step SBV (see Figure 2) for reconstructing a three-dimensional image A of the front side 7.

[0102] 7b shows a schematic diagram of the stereoscopic capture of dentition Z by two image capture devices 5a, 5b of the stereo camera system 1 together with a mirror element 3. The mirror element 3 is shown positioned inside the mouth and providing a mirror image of the back side 8 (see FIG. 3) of dentition Z, which is then imaged by the image capture devices 5a, 5b. A three-dimensional image A of the back side 8 is then reconstructed based on the correspondingly imaged mirror images S5a, S5b.

[0103] Additionally, pre-operative data may be used in conjunction with the images generated by the image capture devices 5a, 5b to generate the three-dimensional image A.

[0104] Alternatively and similarly to stereoscopic detection of the treatment area, it may also be possible to optically capture depth information using a separate image capture system used with the surgical microscope to generate a three-dimensional image of at least a partial section of the dentition. For this purpose, instead of the image generated by the first image capture device and the image generated by the further image capture device, this other detection system can be used to generate a substitute image, in which a mirror image provided by a mirror element arranged in the capture area of the surgical microscope, in particular in the capture area of the capture system, is detected. Then, as described, based on at least the imaged mirror image and the orientation of the mirror element, the orientation of the mirror element and the three-dimensional image can be determined. Therefore, inter alia, optical depth information of the partial section of the dentition can be captured, in particular for the surgical microscope and for the imaging system, and can be embedded in an appropriate coordinate system. [Explanation of symbols]

[0105] 1 Stereo camera system 2 Surgical microscope 3 Mirror Elements 4 Capture Area 5, 5a, 5b Image Capture Device 6 Optically Captivable Marker Elements 7 Front side 8 Back side 9 Chewing surface 10 Evaluation Devices 11a, 11b Beam path 12 Handle Sections 13 Frame Section 14 Mirror surface 15 Virtual Image Capture Device SA Placement Steps SB image generation step S1 First step S2 Second step S3 Third step SBV image generation step SRV Reconfiguration Step EB capture area I5a and I5b images S5a, S5b Mirror image P posture A1, A2, A images OP target point

Claims

1. 1. A method for generating a three-dimensional image (A, A2) of at least a partial section of a dentition (Z) using a stereo camera system (1) of a surgical microscope (2), said stereo camera system (1) comprising a first image capture device (5a) and a further image capture device (5b), a. Respective imaged mirror images (S5a, S5b) are detected in the image (15a) generated by the first image capture device (5a) and in the image (15b) generated by the further image capture device (5b), the imaged mirror images being provided by a mirror element (3) arranged in a capture area (4) of the stereo camera system (1) such that a mirror image of the at least one partial section of the dentition (Z) can be imaged by the first image capture device (5a) and the further image capture device (5b), b. The orientation (P) of the mirror element (3) is determined; c) said three-dimensional image (A, A2) is determined based on at least said imaged mirror images (S5a, S5b) and said pose (P) of said mirror element (3).

2. 2. The method according to claim 1, characterized in that the three-dimensional image (A, A2) is further determined depending on at least one optical property of the mirror element (3) and / or at least one imaging property of the surgical microscope (2).

3. 3. The method according to claim 1 or 2, characterized in that an image of a virtual image capturing device is determined based on at least the position (P) of the mirror element (3), the at least one corresponding section of the dentition (Z) reflected in a catadioptric system is imaged in the image of such virtual image capturing device, and the three-dimensional image (A, A2) is determined based on at least the image of the virtual image capturing device.

4. 3. The method according to claim 1 or 2, characterized in that the pose (P) is determined by evaluating at least one property of the imaged mirror image or of the imaged mirror element (3), or in a marker-based manner.

5. 5. The method according to claim 4, characterized in that for the marker-based determination of the pose (P), at least a marker element (6) is imaged by at least one image capturing device (5a, 5b) of the stereo camera system (1) or by a further image capturing device, and the at least one marker element (6) is arranged on or formed by the mirror element (3), and the pose (P) is determined depending on at least one property of the imaged marker element (6).

6. 3. The method according to claim 1 or 2, characterized in that the focus position of the surgical microscope (2) is set based on the orientation (P) of the mirror element (3).

7. 3. A method according to claim 1 or 2, characterized in that the radiation captured for the purpose of generating the images (I5a, I5b) of the stereo camera system (1) is filtered.

8. 8. The method of claim 7, wherein the filtering is polarization filtering.

9. 8. Method according to claim 7, characterized in that a filter element is arranged in the illumination beam path and / or in the imaging beam path (11a, 11b) and / or above the mirror element (3).

10. 3. A method according to claim 1 or 2, characterized in that the at least one partial section of the dentition (Z) is irradiated with radiation having a predetermined radiation characteristic.

11. 11. The method of claim 10, wherein the radiation is generated with predetermined polarization characteristics.

12. 3. The method according to claim 1 or 2, characterized in that the images (I5a, I5b) produced by the stereo camera system are filtered and the three-dimensional image (A, A2) is determined on the basis of at least the filtered images.

13. 3. A method according to claim 1 or 2, characterized in that at least one quality metric of said three-dimensional image (A, A2) is determined and user information is generated if said quality metric is below a predetermined threshold.

14. A system for generating a three-dimensional image (A, A2) of at least a partial section of a dentition (Z), comprising a stereo camera system (1) with a first image capture device (5a) and at least one further image capture device (5b), and at least one evaluation device (10), a. detecting mirror images (S5a, S5b) imaged in an image (15a) generated by the first image capture device (5a) and in an image (15b) generated by the further image capture device (5b), said mirror images being generated by a mirror element (3) arranged in a capture area (4) of the stereo camera system (1) and reflecting said at least one partial section of the dentition (Z); b. Determining the pose (P) of said mirror element (3); c. determining said three-dimensional image (A, A2) based on at least said imaged mirror images (S5a, S5b) and said pose (P) of said mirror element (3); A system configured to execute the

15. 15. A system according to claim 14, characterized in that it comprises a mirror element (3).

16. 3. A computer program comprising software means for carrying out one, some or all of steps a) to c) of the method according to claim 1 or 2 when the computer program is executed by or in a computer or automation system.

Images