Method and system for generating a three-dimensional image of at least a section of a row of teeth and computer program

Abstract

Method for generating a three-dimensional image (A, A2) of at least a partial section of a row of teeth (Z) using a stereo camera system (1) of an operating microscope (2), wherein the stereo camera system (1) comprises a first image acquisition device (5a) and a further image acquisition device (5b), wherein a. in an image (I5a) produced by the first image acquisition device (5a) and in an image (I5b) produced by the further image acquisition device (5b) a mirror image (S5a, S5b) is detected, which is provided by a mirror element (3) that is arranged in a detection area (4) of the stereo camera system (1) such that a mirror image of at least one part of the row of teeth (Z) can be imaged by the first and further image acquisition devices (5a, 5b), b. a pose (P) of the mirror element (3) is determined, c. the three-dimensional image (A, A2) is determined as a function of at least the imaged mirror images (S5a, S5b) and the pose (P) of the mirror element (3).

Description

[0001] The invention relates to a method and a system for generating a three-dimensional image of at least a partial section of a row of teeth using a stereo camera system of an operating microscope, as well as a computer program.

[0002] In dentistry, particularly during restorative treatments such as implant placement or orthodontic treatment, dental impressions are taken. These serve, for example, to determine the bite position and / or jaw status, especially to document this at different stages of treatment. Dental impressions are also essential for planning and fabricating implants and braces / aligners.

[0003] As is well known, a malleable material is pressed against the teeth to create a dental impression. After a waiting period, usually a few minutes, the dried material can be removed, leaving a negative model of the teeth. This negative can then be used to create a physical model of the teeth, such as a plaster model, which can be used for the aforementioned applications. The problem is that slight changes to the negative can occur when removing the material, reducing the precision of the resulting model. This may necessitate a repeat impression. Furthermore, the time required to create the impression, especially the waiting time mentioned above, and the material consumption are generally undesirable aspects.

[0004] Intraoral scanners are also well-known and are used as alternatives to the previously described method of creating an impression with a malleable material. These scanners use various measurement techniques to generate a reconstruction of the surface of a row of teeth and a digital model, which can then serve as the basis for the applications described. For example, it is conceivable that a dental impression could be produced from this model using additive manufacturing processes, particularly 3D printers. An implant could also be manufactured in this way and then implanted promptly.

[0005] Intraoral scanners typically generate signals based on a specific physical measurement principle using sensors. These signals are then processed to reconstruct or create a model. Common measurement principles used in intraoral scanners include confocal laser scanning, triangulation, and tactile measurement. To create the most complete and accurate model possible, it is necessary to capture all sides of a row of teeth or individual teeth with the respective sensor(s). A disadvantage of current intraoral scanners is that a sensor carrier with the sensor(s) must be inserted into the mouth to capture the posterior surface (the side facing the inside of the mouth) of the teeth.This insertion can be very uncomfortable for a patient, as it may involve unpleasant contact with the lips or other areas of the mouth. The potentially necessary deep insertion into the mouth can also be uncomfortable. Another disadvantage is that the sensor carrier, or the part of the sensor carrier inserted into the mouth, must be cleaned after use, which undesirably delays reuse.

[0006] For the person taking the dental impression, such as the dentist or orthodontist, an intraoral scanner represents an additional piece of equipment in the treatment room, which, due to its size, negatively reduces the available space. Furthermore, integrating such an additional device into established processes, such as the process for taking a dental impression, can be difficult.

[0007] Surgical microscopes are another well-known type of operating microscope. These microscopes are used by a surgeon during a procedure to provide a magnified image of the treatment area, particularly the surgical site. So-called stereoscopic operating microscopes typically have two separate optical channels for beam guidance and can provide the surgeon with a depth perception of the area under examination. The beams in the two channels are viewed through eyepieces by the surgeon's eyes. Digital operating microscopes, either alternatively or additionally, include two image acquisition units, each capturing the beams in one of the optical channels to generate an image. Based on these two images, subsequently referred to as corresponding images, a three-dimensional representation is then displayed to the surgeon via a suitable display device.Furthermore, other surgical microscopes are known that can optically acquire depth information and provide three-dimensional images of a treatment area. For this purpose, optical acquisition systems can be used in the surgical microscope, particularly as an alternative to a stereoscopic system. These systems enable the provision of depth information based on interferometry, triangulation, time-of-flight (TOF), or microlens arrays.

[0008] To ensure accurate representation, precise calibration of the stereo camera system is required. Known calibration methods are used to determine intrinsic and extrinsic camera parameters, which are then used by image processing to guarantee correct representation. Intrinsic camera parameters describe parameters that relate to the camera / image acquisition device itself, such as its distortion. Extrinsic camera parameters describe, in particular, the spatial relationship between the image acquisition devices and thus between the camera images. Such intrinsic and extrinsic camera parameters are known to those skilled in the art.

[0009] The prior art includes DE 10 2020 133 627 A1, which discloses a method and an intraoral scanner for capturing the topography of the surface of a translucent, in particular dental, object.

[0010] Further known is DE 10 2019 008 510 A1, which also discloses an intraoral scanner, in particular for three-dimensional scanning of a dentate or edentulous upper or lower jaw together with jaw components in connection with implant prosthetics.

[0011] Also known is DE 10 2016 121 687 A1, which also discloses an intraoral scanner for digital dental impressions in the dental field as well as a method for creating a digital dental impression using an intraoral scanner.

[0012] Also known is EP 3 689 295 A1, which discloses a dental observation device using a so-called dental microscope.

[0013] DE 42 18 219 A1 discloses a device for non-contact measurement of a poorly accessible, three-dimensional object by optical means, creating planar images, with an optical beam source, a recording unit for recording optical beams and an evaluation unit for evaluating the information transmitted by the optical beams.

[0014] The WO 2020 / 089406 A1 discloses dental measurements, in particular a method and a system for the automatic measurement of periodontal pocket depth, i.e. the depth of a pocket between gingiva and a tooth.

[0015] DE 10 2007 060 263 A1 discloses a scanner for scanning an object, in particular a tooth or several teeth or a tooth model, and a device for determining the 3D coordinates of an object, in particular a tooth or several teeth or a tooth model.

[0016] EP 1 422 495 A1 discloses a device and a method for three-dimensional measurement of the surface shape or surface pattern of an object, a human body, a vehicle, a machine structure or the like in a non-contact manner.

[0017] Against this background, the technical challenge arises of creating a method and system for generating a three-dimensional image of at least a section of a dental arch, as well as a computer program that enables the rapid, accurate, and patient-friendly generation of this three-dimensional image. Furthermore, improved integration into existing application processes and treatment rooms should be facilitated, which in turn reduces the deployment costs for such a system.

[0018] The solution to the technical problem is provided by the articles with the features of the independent claims. Further advantageous embodiments of the invention are described in the dependent claims.

[0019] A method is proposed for generating a three-dimensional image of at least a portion of a dental arch using a stereo camera system of an operating microscope. The operating microscope can be used for magnifying examination objects or areas, particularly in medical applications. Thus, specific areas of the mouth or parts of the mouth can be visualized.

[0020] The surgical microscope comprises a stereo camera system with a first image acquisition unit and a second image acquisition unit. These can each be configured to generate a two-dimensional image. The images can be generated with a predetermined number of pixels and thus a specific resolution. An image sensor in an image acquisition unit can be, for example, a CMOS sensor or a CCD sensor. Of course, other sensor types can also be used. As previously explained, the surgical microscope can include two optically separate beam paths, with the first image acquisition unit being arranged and / or configured such that an image can be generated based on the rays guided in the first beam path.The additional image acquisition device can be arranged and / or designed such that a further image can be generated based on the rays guided in the subsequent beam path. The images can, in particular, be generated simultaneously. Furthermore, the images generated by the first and subsequent image acquisition devices, which are then used to generate the three-dimensional image, can be referred to as corresponding images. Also described is an operating microscope which, in addition to or as an alternative to the stereo camera system, uses a further optical acquisition system to generate the three-dimensional image, in particular to provide depth information. Such optical acquisition systems have already been described in the introduction.

[0021] Furthermore, the surgical microscope can include at least one optical element for beam guidance and / or shaping, which may in particular be designed as a lens element, whereby the at least one optical element may, for example, serve to generate a magnified image. Optical properties of the surgical microscope, such as magnification, focus point, zoom, exposure time, and the size of a field of view, may be adjustable.

[0022] The stereo camera system can be a calibrated stereo camera system. In particular, the intrinsic and extrinsic parameters of the stereo camera system described above can be predetermined, especially via a calibration method known to those skilled in the art. Preferably, the aforementioned parameters are determined for all or predetermined operating states of the surgical microscope, wherein an operating state is characterized by the set (adjustable) parameters of the surgical microscope (for example, zoom, focus point, field of view).

[0023] It is possible that the operating microscope additionally includes at least one eyepiece through which or into which a user can look to visually perceive the image produced by the operating microscope. In particular, the user can also perceive the examination area three-dimensionally through the eyepiece. The operating microscope can include at least one objective or objective system, which comprises at least one optical element for beam guidance and / or shaping. The eyepiece can be optically connected to the objective.

[0024] The operating microscope can be part of a microscopy system, which may also include a stand for mounting the operating microscope. The stand can be designed to allow movement of the operating microscope in space, in particular with at least one degree of freedom, preferably with six degrees of freedom, where one degree of freedom can be translational or rotational. The degrees of freedom can refer to a reference coordinate system. A vertical axis (z-axis) of this reference coordinate system can be oriented parallel to and opposite to the force of gravity. A longitudinal axis (x-axis) and a transverse axis (y-axis) of this reference coordinate system can define a plane oriented perpendicular to the vertical axis. Furthermore, the longitudinal and transverse axes can also be orthogonal to each other.Furthermore, the stand can include at least one drive unit for moving the operating microscope, such as a servo motor. The stand can also include means for transmitting force / torque, e.g., gear and / or coupling units. The operating microscope can thus be movably mounted or held. This allows a user, among other things, to change the pose, i.e., the position and / or orientation, of the operating microscope, for example, to change the viewing angle of one examination area or to view other areas.

[0025] The operating microscope can be, in particular, a dental operating microscope, which is designed to produce images in dental applications.

[0026] A section of a row of teeth can, in particular, comprise at least one tooth or part of a tooth. For the purposes of this invention, a tooth can also refer to a dental prosthesis.

[0027] According to the invention, the proposed method comprises the following steps: In a first step, a mirror image is detected in both an image produced by the first image acquisition unit of the stereo camera system and in an image produced by the second image acquisition unit of the stereo camera system. This mirror image is provided by a mirror element located within a detection area of ​​the stereo camera system.

[0028] In particular, the aforementioned mirror element can be positioned within the detection range of the stereo camera system prior to the detection of the imaged reflection, whereby a reflection of at least a partial section of the dental arch can be imaged by the first and subsequent image acquisition devices. Furthermore, images can be generated by the image acquisition devices prior to detection, especially corresponding images, which are then used to determine the three-dimensional image. This will be explained in more detail below.

[0029] The mirror element can be, in particular, a dental mirror or a part thereof. The mirror element can, in particular, have or form a reflective surface that reflects radiation. The image of the reflective surface, i.e., the projected mirror image, generated by an image acquisition device is produced by capturing this reflected radiation. The mirror image produced / provided by the mirror element is thus perceived by capturing the reflected radiation. Capture by the image acquisition device generates a projected mirror image. However, in addition to the projected mirror image, the image generated by an image acquisition device can also include other areas that do not depict the projected mirror image. In other words, the projected mirror image can be projected into a sub-area of ​​the image generated by an image acquisition device. The projected mirror image depicts at least a portion of the dental arch.The mirror element can further include a frame section that surrounds the mirror surface. It can also include a handle section to allow a user to position the mirror element in the room. The mirror element is preferably a mirror element with a flat, non-curved mirror surface. Preferably, the mirror surface is round. However, it is also conceivable to use rectangular mirror surfaces.

[0030] In a second step, the pose of the mirror element, particularly the mirror surface, is determined. The pose can include a translational and a rotational component. For example, the position of a reference point of the mirror element, such as the center point of the mirror surface, and the orientation of the mirror element, such as the orientation of a normal to the mirror surface, can be defined as the pose of the mirror element. Naturally, the positions of multiple reference points or the orientations of multiple segments of the mirror element can also be defined as the pose, especially in the case of a curved mirror surface. Exemplary methods for determining the pose are explained in more detail below. The pose can be determined in a reference coordinate system. This could be, for example, the reference coordinate system of the stereo camera system, the operating microscope, or the reference coordinate system described above.

[0031] In a third step, the three-dimensional image is determined based on at least the mirror images detected in the (corresponding) images generated by the two image acquisition devices and the pose of the mirror element. For this purpose, a stereo reconstruction method can be used, for example, with the mirror images serving as input images for this method. Such methods are known to those skilled in the art. In particular, corresponding pixels in the two input images can be determined using such methods. Such corresponding pixels or pixel sets can be determined, for example, using a feature-matching method. Corresponding methods and features are known to those skilled in the art. Exemplary features are so-called SIFT features, i.e., features for a scale-invariant feature transformation.Of course, other methods can also be used for determination, such as variational methods or AI-based methods. Then, for an object point or segment that is mapped into corresponding image points or sets of image points, three-dimensional coordinates can be determined in the reference coordinate system described above. This can also be referred to as reconstruction, whereby a corresponding reconstruction procedure is carried out depending on the pose of the mirror element. In particular, at least one step of the reconstruction procedure can be carried out depending on the pose. Specifically, the pose can be represented by at least one parameter, whereby the at least one step of the procedure is carried out depending on the parameter or takes the parameter into account during its execution.Preferably, a stereotriangulation reconstruction method is used to determine the three-dimensional image. Stereotriangulation reconstruction methods are known to those skilled in the art. In this case, a projection matrix used in the reconstruction, which describes a perspective transformation of three-dimensional object coordinates in a reference coordinate system into two-dimensional image coordinates, can be determined depending on the pose of the mirror element and (known) laws of reflection. In other words, the pose of the mirror element influences the projection matrix of both image acquisition devices and thus also the stereotriangulation reconstruction performed on the basis of or depending on these projection matrices. For example, a so-called homogeneous solution method or a so-called inhomogeneous solution method can be used to determine the three-dimensional coordinates.It is possible that a rectification procedure is carried out before the determination of the three-dimensional image to compensate for or eliminate, in particular, non-linear distortions of the images.

[0032] The proposed method advantageously enables the simple, accurate and patient-friendly creation of a three-dimensional image, in particular an intraoral scan, since, compared to the existing methods described above, usually only a small mirror element needs to be placed in the mouth to capture and three-dimensionally represent a section of a row of teeth.

[0033] The proposed method is used in particular to generate a three-dimensional image of the posterior surface of a row of teeth and / or of the occlusal or chewing surfaces of the row of teeth. The posterior surface of the row of teeth can, in particular, refer to the side of the row of teeth facing the interior of the mouth. A three-dimensional image of the anterior surface of a row of teeth or a section thereof can be determined without the first and second steps described above. In particular, the three-dimensional image can be determined based on corresponding images generated by the image acquisition devices, whereby known methods for stereo reconstruction can be applied. The image acquisition devices for generating the image can be located outside the oral cavity, i.e., extraorally. Thus, the method can also be referred to as an extraoral scan.

[0034] The three-dimensional model can be generated, for example, as a CAD data set, such as in STL format. Such a three-dimensional model can then be visualized, for example, by displaying it on a screen. The three-dimensional model can also be used in further processes, such as CAD / CAM processes, for example, to create a dental impression.

[0035] In a further embodiment, the three-dimensional image is additionally determined depending on at least one optical property of the mirror element. This at least one optical property can be predetermined. Alternatively, the at least one optical property can also be determined in a further step of the proposed method, in particular image-based, i.e., by evaluating at least one image of the mirror element. An optical property of the mirror element can, in particular, be a magnification or reduction property. Of course, other optical properties of the mirror element that affect the imaging of the mirror image can also be taken into account. For example, the optical property can be represented by the projection matrix described. This advantageously results in high accuracy of the generated three-dimensional image.

[0036] Alternatively or cumulatively, the three-dimensional image is additionally determined depending on at least one imaging property of the operating microscope. An imaging property can be, in particular, a set magnification (zoom), a set focus point, or another imaging property that affects the projected image. This imaging property can also be represented by the projection matrix described above. This also advantageously results in the generation of a highly accurate three-dimensional image.

[0037] In a further embodiment, at least depending on the pose of the mirror element, (corresponding) images of virtual image acquisition devices are determined, wherein at least one corresponding section of the tooth row mirrored in a catadioptric system is depicted in an image of such a virtual image acquisition device. Furthermore, the three-dimensional image is determined depending on the images, in particular the corresponding section in the respective images, of the virtual image acquisition devices.

[0038] The catadioptric system is an optical transmission system that includes at least the mirror element and optical elements of an image acquisition device, such as a lens. In particular, the catadioptric system can include optical elements of the objective lens of a surgical microscope. A beam path through the catadioptric system can be determined based on known or determinable optical properties of the optical elements in the catadioptric system, the pose of the mirror element, and known optical principles.

[0039] The virtual image acquisition device is a mathematical or physical model of an image acquisition device, which can be evaluated using computer-aided methods. Depending on the model, a virtual image generated by the virtual image acquisition device can be created or calculated, particularly through a computer-implemented calculation of the pixels. This virtual image depends, among other things, on parameters of the (modeled) image acquisition device and its pose. These parameters, especially extrinsic and / or intrinsic parameters, of the virtual image acquisition device can depend on the optical properties of the mirror element. For example, if the mirror surface is flat and has no magnification properties, the intrinsic parameters of the virtual image acquisition device can be the same as the intrinsic parameters of the modeled image acquisition device.

[0040] In particular, depending on the pose of the mirror element, a pose of the virtual image acquisition device can be determined such that the virtual image of the virtual image acquisition device in this pose depicts the unmirrored section of the dental arch that is mirrored by the catadioptric system and thus also by the mirror element. This section is designated as the corresponding segment. Besides the pose of the mirror element, the generation of such a virtual image also depends on the (further) properties of the catadioptric system, e.g., the zoom setting of a lens.

[0041] The three-dimensional image can then be determined using a method known to those skilled in the art, depending on the virtual image, in particular the corresponding section. Exemplary methods have been explained above. In such a method, properties of the catadioptric system, and thus also the pose of the mirror element, can be taken into account. In other words, the reflected image can be transformed into an unreflected image, and then the three-dimensional image can be generated based on the unreflected image. This advantageously results in an accurate and computationally simple determination of the three-dimensional image, which can be generated with high precision.

[0042] In a further embodiment, the pose is determined by evaluating at least one property of the imaged reflection or the imaged mirror element (or a section thereof). This at least one property can be determined image-based, in particular by evaluating the image generated by the respective image acquisition device. Specifically, the imaged mirror surface or mirror element can be recognized in such an image, for example, by object recognition methods known to those skilled in the art. Object recognition methods can, for example, be segmentation methods. Thus, for example, the imaged mirror surface, the imaged frame section, or an imaged handle section can be recognized image-based. It is possible, for example, to identify a section, e.g., a frame section, of the mirror element made of material with predetermined optical properties, e.g.,to be made of matte material, in particular to enable reliable detection of this section in the image. Alternatively, detection can also be carried out by a user selecting an image area, for example via a suitable input device, in which the mirror image or the section to be detected is depicted.

[0043] A property of the imaged reflection or mirror element can be a geometric property, such as a dimensional property like a dimensional quantity. A dimensional quantity can be a width, a height, a diameter, or another dimensional quantity. A property can also be a shape property, such as a geometric shape like a circle, an ellipse, a rectangle, or another geometric shape. In particular, a shape factor can be determined that represents a relationship between an imaged shape and an actual shape, with the pose being determined as a function of the shape factor.

[0044] As previously explained, the pose of the mirror element can influence the image captured by the image acquisition devices. Thus, the pose can also influence how an actual property of the mirror image or mirror element is mapped to a property of the imaged mirror image or element. If a relationship between the actual property and the property of the imaged mirror image can be described by a transformation matrix that depends on the pose, then the pose can be determined based on the actual property and the property of the imaged mirror image or imaged mirror element. The actual property may be known in advance, e.g., from a model, particularly a CAD model, of the mirror element, or it may be determinable.

[0045] If the mirror element or a part thereof, in particular the mirror surface, is circular, and the reflected image is elliptical, then, depending on properties of the ellipse, for example, the orientation and lengths of the ellipse's axes, as well as the known properties of the circular mirror element, the pose can be determined such that the known properties are transformed into the properties of the reflected image. If polygonal mirror elements, in particular equilateral polygonal mirror elements, are used, then at least part of the pose can be determined via a ratio of the edge lengths in the image and the relative position of the edges in the image to each other.

[0046] The property can also be a pose of the depicted mirror image or mirror element, or a part thereof, within the image coordinate system. The position can be determined, for example, as the position of a reference point, such as a geometric center. The orientation can be determined, for example, as the orientation of an axis of a reference segment. If the mirror element includes a handle section, this can be recognized in the image, and its position and / or orientation can be determined. For example, the orientation of a longitudinal axis of the handle section can be determined.

[0047] If the pose is determined by evaluating at least one property of the imaged mirror image or the imaged mirror element, a simple determination of the pose is advantageously achieved, since the images generated anyway can be evaluated to determine the pose.

[0048] Alternatively, the pose can be determined using markers. For this purpose, the mirror element can have or form at least one marker element to determine its pose. Of course, it is also possible for the mirror element to have or form multiple markers, whereby the pose of the mirror element can be determined depending on a known relative position and / or dimension of these markers.

[0049] The marker element can be active or, preferably, passive. It can be configured to be detected by a detection device. The detection device can, in particular, be an image capture device. In this case, the marker element can be optically detectable. For example, it is conceivable that an optically detectable marker has a predetermined pattern that allows the determination of the marker's pose and thus the mirror element's position. Such optically detectable patterns can, for example, be in the form of QR codes. Optically detectable markers can also be reflective, being designed to reflect radiation from a predetermined wavelength range, such as the infrared wavelength range.The image acquisition device for optically capturing the marker element can be an image acquisition device of the stereo camera system or a different image acquisition device. If the mirror element comprises several marker elements, the pose of the mirror element can also be determined depending on the relative position of the imaged marker elements in the image. The pose of the mirror element can also be determined, at least partially, by a stereoscopic determination of the pose of at least one marker element.

[0050] Using the image acquisition device and the marker element, a so-called monoscopic pose determination can be performed. Here, the pose can be determined by evaluating a two-dimensional image, in particular exactly one two-dimensional image from exactly one image acquisition device. Specifically, the position can be determined by evaluating the intensity values ​​of pixels in the two-dimensional image. Such methods for image-based position determination with exactly one image acquisition device and / or based on exactly one two-dimensional image are known to those skilled in the art. If a stereo camera system is used, the pose can also be determined by evaluating the corresponding images from the image acquisition devices.

[0051] In particular, the pose can be determined using optical tracking methods, specifically employing an image capture device to determine the pose. Such optical tracking can be marker-based, using special visually or optically detectable marker elements, such as QR codes or other optical patterns, to determine the pose.

[0052] Alternatively, particularly in the previously explained determination of the pose by evaluating at least one property of the depicted mirror image or the depicted mirror element, markerless tracking methods can also be used, whereby features are recorded and used to determine the pose.

[0053] As an alternative to an optically detectable marker element, a marker element that can be detected in another way can also be used to determine the pose of the mirror element, for example, a marker element that can be detected magnetically, capacitively, inductively, or radio-based. For example, a marker element can be designed as an RFID tag.

[0054] It is also possible for the mirror element to include a pose sensor, for example an initialization sensor or a GNSS sensor, wherein the pose is determined depending on the output signals of such a sensor. In such an embodiment, the operating microscope can include a receiver for the output signals generated by the pose sensor or be connected to such a receiver.

[0055] Of course, it is also possible to determine the pose using a hybrid method, whereby such a hybrid method combines at least two of the previously explained methods for determining a pose.

[0056] In the case of marker-based pose determination, a very accurate pose determination is advantageously achieved, which in turn leads to the generation of an accurate three-dimensional image.

[0057] A marker element can also be identifiable, in particular uniquely. For example, a pattern of an optically detectable marker can encode the marker's identity. Thus, the marker element or the mirror element can be identified by detecting the marker element. Properties of the mirror element, especially the optical properties described above, can be assigned to this determinable identity. This assignment, as well as the identity and the properties, can be stored, for example, in a storage device in a retrievable or readable manner. This advantageously results in a simple determination of the mirror element's optical properties.

[0058] In a further embodiment, for marker-based pose determination, at least one marker element is imaged by at least one image acquisition device of the stereo camera system or by a further image acquisition device. The at least one marker element is arranged on the mirror element or is formed by it. The pose is then determined depending on at least one property of the imaged marker element. This has already been explained above. The further image acquisition device can, in particular, be a tracking camera or a background camera of a microscopy system, which is configured differently from the image acquisition devices of the stereo camera system. This tracking or background camera can, in particular, serve for marker-based tracking of further instruments.In both cases, the simplest possible integration of an optical determination of the pose when using the operating microscope or a microscopy system with the operating microscope is advantageously achieved.

[0059] In a further embodiment, the focus position of the operating microscope is adjusted depending on the pose of the mirror element. This makes it possible, in particular, to set the focus position on a point on the mirror surface or on a point that is no more than a predetermined distance from the mirror surface. The predetermined distance can, in particular, depend on the depth of field of the operating microscope, and especially be smaller than the depth of field. The depth of field is known or can be determined. This enables high image quality to be achieved for the mirror image, which in turn advantageously increases the accuracy of the generated three-dimensional image. In particular, this also makes it easier and more reliable to detect the imaged mirror image in an image acquisition device.

[0060] In another embodiment, the radiation captured to generate the images of the stereo camera system is filtered. In a preferred embodiment, the filtering is polarization filtering. Of course, other radiation filters can also be used. This advantageously suppresses unwanted reflections on a tooth surface in the image, thereby increasing the accuracy of the generated three-dimensional image. Polarization filtering enables the strongest possible, or even complete, suppression of reflections.

[0061] In another embodiment, a filter element is arranged in an illumination beam path of the surgical microscope and / or in an imaging beam path. In particular, a filter element can be arranged in each imaging beam path. In both cases, this results in good structural integration of a filter element into the surgical microscope or into a microscopy system, which enables the generation of a three-dimensional image with high accuracy.

[0062] Alternatively or cumulatively, a filter element is arranged on the mirror element. For example, the filter element can be arranged on a mirror surface of the mirror element. This advantageously eliminates the need to integrate an additional filter element into the operating microscope or microscopy system to generate a highly accurate three-dimensional image, as the mirror element provides the desired filtering properties.

[0063] In a further embodiment, at least one section of the tooth row is illuminated with radiation having predetermined radiation properties. Such radiation properties can be, for example, predetermined wavelength(s) of the radiation used for illumination, predetermined intensities, or, in a preferred embodiment, predetermined polarization properties or other properties of the radiation used for illumination. This also advantageously reduces reflections on the tooth surface, which in turn has a beneficial effect on the accuracy of the generated three-dimensional image.

[0064] In another embodiment, the images generated by the stereo camera system are filtered, with the three-dimensional image being determined based on at least the filtered images. In particular, filtering can be performed to reduce unwanted reflections in the image. However, filtering can also generally serve to improve image quality, which in turn advantageously increases the accuracy of the three-dimensional image. An exemplary filtering method for reflection suppression is the so-called tone mapping technique.

[0065] For example, it is possible to temporarily stain the teeth during image acquisition. Color filtering can then be performed, reducing, for example, the color components in the image that differ from the staining color.

[0066] In a further embodiment, at least one quality measure of the three-dimensional image is determined. Furthermore, user information is generated if the quality measure is less than a predetermined threshold. Here, the quality measure is chosen such that it is proportional to the quality of the three-dimensional image. The user information can be output to the user via an output device, for example, an optical or acoustic output device. This can be part of the surgical microscope or a microscopy system.

[0067] For example, it can be determined whether the point density in a predetermined section of the generated three-dimensional image is lower than the predetermined threshold. If this is the case, user information can be generated, as it may be desirable to perform a more accurate reconstruction with a higher density, at least in this sub-area. In particular, the specific quality measure, e.g., the point density, can be generated as part of the user information.

[0068] Furthermore, if the quality measure is determined in a sub-area-specific manner, information about the sub-area, in particular its position, can be generated as part of the user information.

[0069] This advantageously ensures a high accuracy of the generated three-dimensional image, since in the event of an undesirably low quality, user information is generated and the process is repeated, for example, for the sub-area for which the too low quality level was determined.

[0070] A further proposed system is for generating a three-dimensional image of at least a partial section of a row of teeth, wherein the system comprises a stereo camera system and at least one evaluation unit. The stereo camera system comprises a first and a further image acquisition unit. The system is configured to perform a method according to one of the embodiments described in this disclosure, in particular the steps: a) Detection of a mirror image in an image produced by the first image acquisition device and in an image produced by the further image acquisition device, wherein the mirror image is provided by a mirror element arranged in a detection area of ​​the stereo camera system and which reflects at least one part of the row of teeth, b) Determining a pose of the mirror element, c) Determination of the three-dimensional image depending on at least the mirror images shown and the pose of the mirror element.

[0071] The evaluation unit can be configured as a computing unit or include one. A computing unit, in turn, can include a microcontroller or an integrated circuit, or be configured as such. The evaluation unit can perform at least one, but preferably all, of the steps a), b), and c).

[0072] The system can be part of a surgical microscope or a microscopy system, whereby the surgical microscope or microscopy system can include the stereo camera system and the evaluation unit. Furthermore, the system can include a detection device for capturing a marker element. The system can also include a filter element for filtering the radiation used to generate the images from the stereo camera system. The system can further include an illumination device for illuminating the section with predetermined radiation properties. Finally, the system can include an output device for user information.

[0073] The system advantageously enables the execution of a method according to one of the embodiments described in this disclosure, with the advantages already described.

[0074] In another embodiment, the system includes a mirror element for arrangement in the detection area of ​​the stereo camera system.

[0075] A further proposal is a computer program comprising software means for executing one, several, or all steps, in particular the set of first step, second step, third step, of a method according to one of the embodiments described in this disclosure, 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.

[0076] A mirror element for generating a three-dimensional image of at least a partial section of a row of teeth is further described. According to the invention, the mirror element has or forms at least one marker element for determining the pose of the mirror element. Alternatively or cumulatively, the mirror element has or forms at least one filter element for filtering the reflected radiation. This and corresponding advantages have already been explained above.

[0077] The invention is explained in more detail using exemplary embodiments. The figures show: Fig. 1 a schematic flowchart of a method according to the invention, Fig. 2 a schematic flowchart of a method according to the invention in a further embodiment, Fig. 3 a schematic block diagram of a system according to the invention, Fig. 4a a mirror element in a first pose, Fig. 4b the in Fig. 4a mirror element shown in another pose, Fig. 4c that in Fig. 4a mirror element shown in another pose, Fig. 4d that in Fig. 4a mirror element shown in another pose, Fig. 5 a schematic representation of a mirror element according to the invention, Fig. 6 a schematic block diagram of a virtual image acquisition device, Fig. 7a a schematic view of a stereoscopic recording of a row of teeth without a mirror element and Fig. 7b a schematic view of a stereoscopic recording of a row of teeth with a mirror element.

[0078] In the following, identical reference symbols denote elements with the same or similar technical characteristics.

[0079] Fig. Figure 1 shows a schematic flowchart of a method according to the invention for generating a three-dimensional image A of at least a partial section of a tooth row Z (see Figure 1). Fig. 3) with a stereo camera system 1 of an operating microscope 2. Before a first step S1 of the procedure, a mirror element 3 is arranged in a detection area 4 of the stereo camera system 1 such that a mirror image of at least the partial section of the dental arch Z can be imaged by a first image acquisition device 5a and by a further image acquisition device 5b of the stereo camera system 1 (arrangement step SA). After this arrangement, an image I5a, I5b is generated by both the first image acquisition device 5a and the further image acquisition device 5b, whereby these images I5a, I5b can be referred to as corresponding images (image generation step SB). These are generated from different positions and / or with different orientations. Furthermore, they can be generated simultaneously or with a predetermined maximum time offset.In a first step S1 of the process, a mirror image S5a is detected in the image I5a generated by the first image acquisition device 5a, for example, using an object recognition method. The image I5a generated by the first image acquisition device 5a can include, in addition to a sub-area containing the mirror image provided by the mirror element 3, further sub-areas that, for example, depict other sections of the tooth row Z, particularly those not reflected by the mirror element 3. Similarly, a mirror image S5b is also detected in the image I5b generated by the second image acquisition device 5b. The mirror images S5a and S5b detected in this way form input variables for determining the three-dimensional image A. In a second step S2 of the process, a pose P, i.e., a position and / or orientation of the mirror element 3, is determined in a reference coordinate system.The reference coordinate system can be a reference coordinate system of the operating microscope 2 or a reference coordinate system of the stereo camera system 1. Of course, other reference coordinate systems are also conceivable. In addition to the mirror images S5a and S5b shown, the pose P forms another input parameter for determining the three-dimensional image A.

[0080] In a third step S3, the three-dimensional image A is then determined as a function of at least the depicted mirror images S5a, S5b and the pose P of the mirror element 3, for example via a stereo reconstruction. This has already been explained previously.

[0081] It should be mentioned here that the in Fig. The sequence of the first and second steps S1, S2 shown in point 1 is not mandatory. In particular, it is possible to determine the pose P simultaneously with or before the detection of the depicted mirror images S5a, S5b.

[0082] Furthermore, it is possible that the three-dimensional image A is additionally determined depending on at least one optical property of the mirror element 3. This optical property then forms a further input variable for the third step S3. The optical property can be predetermined. In this case, it is particularly possible to identify the mirror element, whereby the at least one optical property can be assigned to the preferably unique identity of the mirror element 3. Depending on this assignment, the optical property can then be determined using the determined identity of the mirror element 3, for example, retrieved from a database that can be stored in a storage device and represents the assignment of identity to the at least one optical property. Such an identification step, which is described in Fig. Since the identification of the mirror element is not shown, it can be carried out before the third step S3. Preferably, an image-based identification of the mirror element can be performed, for which at least one of the generated images I5a, I5b, in which the mirror element 3 is mapped, is evaluated. For example, but not necessarily, the identification can be carried out simultaneously with the determination of the pose in the second step S2. The identification can be carried out by evaluating at least one property of the mapped mirror element or using a marker-based approach. This will be explained in more detail below with regard to the determination of the pose P.

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

[0084] The determination of the pose P of mirror element 3 in the second step S2 can be image-based, in particular by evaluating at least one property of the imaged mirror image S5a, S5b or of the imaged mirror element 3. The property can be a dimensional property. It can also be a shape property. Such properties have been explained previously. In particular, the properties in the image S5a, S5b can be determined and compared with previously known properties of the mirror image or of mirror element 3 in a reference position (see, for example, [reference]). Fig. 4a) can be compared, in particular with a computationally determinable representation of the mirror image or the mirror element 3 in this reference position. From a deviation between the actual property in the representation and the previously known property determined in this way, the pose P of the mirror element 3 can then be determined. For example, a transformation can be determined with which the representation of the mirror image or the mirror element in the reference position is transformed into the actual representation, whereby this transformation contains information about the current pose P of the mirror element 3.

[0085] Alternatively, the determination of pose P can be marker-based. For this purpose, marker elements, which in an exemplary embodiment are Fig. 5 are represented as optically detectable marker elements 6. Such marker elements 6 can be active marker elements, i.e., marker elements that generate detectable signals using energy, or passive marker elements that can be detected without energy consumption by the marker element. An example of a passive marker element is the one shown in Fig. The 5 depicted optically detectable marker elements 6 are designed in the form of barcodes or optical patterns. Of course, optically detectable markers can also be active markers that, for example, generate optically detectable signals while consuming energy. Alternatively, marker elements that can be detected in other forms, such as magnetically detectable marker elements, can also be used. A marker element can be arranged in or on the mirror element 3, whereby the pose P of the mirror element can then be determined depending on the detected marker element.

[0086] Is at least one marker element an optically detectable marker element 6, e.g., the one in Fig. If the passive, optically detectable marker element 6 is shown in Figure 5, then, to determine the pose P, at least one marker element can be imaged by at least one image acquisition device 5a, 5b of the stereo camera system 1 or by another (not shown) image acquisition device, and the pose P can then be determined depending on at least one property of the imaged marker element. In this case, the determination of the pose P can only be carried out after the respective image I5a, I5b has been acquired.

[0087] It is also conceivable that the focus position of the operating microscope 2 is set depending on the pose P of the mirror element 3. In this case, the generation of images I5a, I5b, which are evaluated to determine the three-dimensional image A, can take place after the pose P has been determined. If the pose P is determined image-based, images can be generated before the pose P is determined. These images serve to determine the pose P, and then the focus position is set depending on the pose P. Finally, images I5a, I5b are generated, which serve to detect the reflected image S5a, S5b.

[0088] Fig. Figure 2 shows a schematic flowchart of a further embodiment of a method according to the invention. In contrast to the one in Fig. In the embodiment shown in Figure 1, images I5a and I5b, i.e., corresponding images, of a front surface 7 of the tooth row Z are additionally generated in a further image generation step SBV, wherein, depending on these images I5a and I5b, a three-dimensional partial image A1 of the front surface is generated in a reconstruction step SRV. Subsequently, the Fig. The procedure described in Figure 1 is carried out, wherein the resulting image A is a partial image A2 of a posterior surface 8 of the dental arch Z and of occlusal surfaces 9 of the teeth of dental arch Z. The partial images A1, A2 are fused / combined in a fusion step FS to form a resulting image A of dental arch Z. For this purpose, corresponding points in the three-dimensional partial images A1, A2 can be detected in order to fuse the partial images A1, A2. For this, it may be necessary to scale the structures depicted in at least one of the partial images A1, A2, in particular those in the partial image A2 of the posterior surface 8. Such scaling can be performed, in particular, depending on the distance between mirror element 13 and the mirrored section of dental arch Z. This distance can be determined, in particular depending on the pose P of the mirror element 13.The distance can also be determined depending on different focus positions of the stereo camera system 1, which will be explained in more detail below. The partial images A1, A2, and the resulting image A can preferably be provided in an STL data format, which advantageously allows them to be used in further processes, especially in CAD / CAM processes. The resulting three-dimensional image A, or the partial images A1, A2, can also be displayed to a user via a suitable display device. It is possible to overlay information, such as color information, onto the displayed image.

[0089] Fig. Figure 3 shows a schematic block diagram of a system according to the invention for generating a three-dimensional image of at least a partial section of a row of teeth Z, wherein the system comprises a stereo camera system 1 and at least one evaluation unit 10. The system is configured to at least the Fig. 1 and Fig. to perform the steps S1, S2, S3 shown in the diagram. Of course, the system can also be configured to... Fig. The steps SBV, SRV, FS shown in the diagram are to be carried out. These steps, or at least parts of them, can be carried out by the evaluation unit 10.

[0090] In Fig. Figure 3 schematically depicts the acquisition areas EB of the image acquisition devices 5a, 5b and the optically separated beam paths 11a, 11b of the operating microscope 2. Not shown is the illumination device of the operating microscope 2, which can illuminate the dental arch Z. The illumination device can generate radiation with predetermined radiation properties, in particular predetermined polarization properties. The radiation reflected from the dental arch Z passes via the beam paths 11a, 11b to the image sensors of the image acquisition devices 5a, 5b, thereby generating an image I5a, I5b of the dental arch Z. This image can be evaluated by the evaluation unit 10.Also shown is a mirror element 3, which also reflects rays from the tooth row Z, in particular its back surface 8, whereby this reflected radiation also passes through the beam paths 11a, 11b to the image sensors and is imaged there as a mirror image. This image can then be detected by the evaluation unit 10 as an imaged mirror image.

[0091] It is possible that the radiation captured to generate the images I5a, I5b of the stereo camera system 1 is filtered. This can be achieved by filter elements, which are, for example, arranged in the beam paths 11a, 11b. A filter element can also be arranged in an illumination beam path of an illumination device (not shown) of the operating microscope 2. A filter element can also be arranged on / at the mirror element 3. Such a filter element can, in particular, be a polarizing filter element. Furthermore, it is possible that the evaluation unit 10 filters the image I5a, I5b generated by the image acquisition devices 5a, 5b, for example, to suppress reflections.

[0092] Fig. Figure 4a shows an image of a mirror element 3 in a reference pose. The mirror element 3 comprises a handle section 12 and a round mirror section 13, which in turn comprises a mirror surface 14. A reference point P3 of the mirror element 3 is, for example, the center point of this mirror surface 14. A mirror-fixed coordinate system is shown with a longitudinal axis x3, a transverse axis y3, and a vertical axis z3 (see Figure 4a). Fig. 4b).

[0093] Fig. Figure 4b shows an image of the mirror element 3 in a pose P, which is established when the mirror element 3 is removed from the position shown in Figure 4b. Fig. The reference position shown in 4a is rotated about the longitudinal axis x3a. It can be seen that the position shown in Fig. The round mirror surface 14 shown in Figure 4a is then mapped as an ellipse. Depending on the orientation and length of the major and minor axes of this ellipse, which can be detected, for example, using an object recognition method, it is then possible to determine the rotation angle of the mirror element 3 about the longitudinal axis x3a, which in turn determines the current pose P of the mirror element 3. Fig. The mirror element 3 shown in 4b can be determined.

[0094] In an analogous way, they show Fig. 4c and Fig. 4d depicted mirror elements 3, which, compared to the one in Fig. 4a shown reference position around the transverse axis y3 ( Fig. 4c) or around the vertical axis z3 ( Fig. 4d) were rotated. The corresponding rotation angles can, for example, depend on an orientation of the longitudinal axis x3 ( Fig. 4d) and / or depending on the orientation and length of the axes of an elliptical image of the mirror surface 14.

[0095] From the Fig. From 4a to 4d it follows that a shape-based determination of the pose P of the mirror element 3 can be carried out, whereby shape properties of the imaged mirror element 3 can be determined and the pose P can then be determined depending on these properties.

[0096] It is also evident that a center point of the mirror surface 14 can be detected. If, in addition to a point reflected on the mirror surface 14, e.g., the center point, the focus is also placed on a non-reflective edge of the mirror surface 14, the distance of the mirror surface 14, in particular the point of reflection, to the tooth row Z can be determined by the difference in the focus positions.

[0097] In particular, a difference can be determined between the focus position when the stereo camera system 1 or the operating microscope 2 is focused on a point of the non-reflective edge, e.g., a point of the frame section 13, and the focus position when focused on a point of the object projected onto the mirror surface 14, for example, a point reflected at the center of the mirror surface 14. This difference in focus positions can represent a distance between the mirror element 13 and the object, here a point on the row of teeth Z, whereby the distance can be determined as a function of this difference. Additionally, the distance can also be determined as a function of the pose P of the mirror element 13. This distance information can be used for scaling in the described stereo reconstruction, in particular to achieve magnification when reconstructing a projected section, e.g.,to adapt the back 8 of the tooth row Z to an enlargement in a reconstruction of an unmirrored section, e.g. the front 7 of the tooth row Z, i.e. to perform a scaling.

[0098] Fig. Figure 5 shows a schematic representation of a mirror element 3 according to the invention. This element has, or forms, a marker element 6 on a handle section 12, which is designed as an optically detectable barcode. The mirror element 3 also has further optically detectable marker elements 6, designed as barcodes, on a frame section 13 of the mirror surface 14. These can be detected in an image of the mirror element 3, and these marker elements enable, in particular, the identification of the mirror element 3 as well as the determination of the pose P of the mirror element 3. In particular, in the case of the Fig. Each marker element 6 of the mirror element 3 shown in the image can be detected, and the pose P can then be determined via a relative arrangement of the marker elements in the image.

[0099] Fig. Figure 6 shows a schematic representation of an image acquisition device 5 of a stereo camera system 1 (see Fig. 3) and a mirror element 3, which is arranged in the detection area EB of the image acquisition device 5. Also shown is an object point OP to be imaged, for example a point on the surface of a row of teeth Z (see Fig. 3). Also shown is a normal n of a mirror surface 14 of the mirror element 3.

[0100] Also shown is a virtual image acquisition device 15. A (virtual) image of this virtual image acquisition device 15 can be determined by evaluating a mathematical or physical model. The model is determined in such a way that a virtual image is generated which depicts a section of the dental arch Z, in particular the object point OP, which corresponds to the section mirrored in the catadioptric system, in an unmirrored manner, taking into account the properties of the catadioptric system. The three-dimensional image A can then be determined as a function of the virtual image using a method known to those skilled in the art, for example, via a stereo reconstruction. This has already been explained above.

[0101] Fig. Figure 7a shows a schematic view of a stereoscopic acquisition of a row of teeth Z by two image acquisition devices 5a, 5b of a stereo camera system 1 without a mirror element 3. Shown is an acquisition of an anterior surface 7 of the row of teeth Z as it would be, for example, in the further image generation step SBV (see Figure 7a). Fig. 2) to reconstruct a three-dimensional image A of the front side 7.

[0102] Fig. 7b a schematic view of a stereoscopic recording of a row of teeth Z by two image acquisition devices 5a, 5b of a stereo camera system 1 with mirror element 3. Shown is a mirror element 3 which is arranged inside the mouth and which is a mirror image of a back 8 (see Fig.3) of the tooth row Z, whereby this mirror image is then imaged by the image acquisition devices 5a, 5b. Based on the correspondingly imaged mirror images S5a, S5b, a three-dimensional image A of the back 8 is then reconstructed.

[0103] Furthermore, preoperative data can also be used with the images generated by the image acquisition devices 5a, 5b to generate the three-dimensional images A.

[0104] Alternatively, and analogous to the stereoscopic acquisition of a treatment area, it may also be possible to optically acquire depth information using a different acquisition system within the operating microscope in order to generate a three-dimensional image of at least a section of a dental arch. For this purpose, instead of the image generated by the first image acquisition device and the image generated by the second, an alternative image can be generated with this other acquisition system. This alternative image is created by detecting a reflection provided by a mirror element located within the acquisition area of ​​the operating microscope, and in particular within the acquisition area of ​​the acquisition system itself. Then, as explained, the pose of the mirror element and the three-dimensional image can be determined based on at least the projected reflection and the pose of the mirror element.Thus, among other things, the optical depth information of a section of the dental arch can be captured for the operating microscope and especially for the detection system and embedded in a suitable coordinate system. Reference symbol list 1 stereo camera system 2 Operating microscopes 3 mirror elements 4. Detection area 5, 5a, 5b Image capture device 6 optically detectable marker elements 7 Front 8 Back 9 chewing surface 10 Evaluation unit 11a, 11b Beam path 12 Handle section 13 Framework section 14 Mirror surface 15 virtual image capture devices SA Arrangement Step SB Image generation step S1 first step S2 second step S3 third step SBV image generation step SRV Reconstruction Step EB recording area I5a, I5b images S5a, S5b depicted mirror image P Pose A1, A2, A Image OP Object Point

Claims

[1] Method for generating a three-dimensional image (A, A2) of at least a partial section of a row of teeth (Z) using a stereo camera system (1) of an operating microscope (2), wherein the stereo camera system (1) comprises a first image acquisition device (5a) and a further image acquisition device (5b), wherein a. in an image (I5a) produced by the first image acquisition device (5a) and in an image (I5b) produced by the further image acquisition device (5b) a mirror image (S5a, S5b) is detected, which is provided by a mirror element (3) that is arranged in a detection area (4) of the stereo camera system (1) such that a mirror image of at least one part of the row of teeth (Z) can be imaged by the first and further image acquisition devices (5a, 5b), b. a pose (P) of the mirror element (3) is determined, c. the three-dimensional image (A, A2) is determined as a function of at least the imaged mirror images (S5a, S5b) and the pose (P) of the mirror element (3). [2] Method according to claim 1, characterized by , that the three-dimensional image (A, A2) is additionally determined depending on at least one optical property of the mirror element (3) and / or at least one imaging property of the operating microscope (2). [3] Method according to any of the preceding claims, characterized by , that at least depending on the pose (P) of the mirror element (3) images of virtual image acquisition devices are determined, wherein at least one corresponding section of the row of teeth (Z) mirrored in a catadioptric system is mapped into an image of such a virtual image acquisition device, wherein the three-dimensional image (A, A2) is determined depending on at least the images of the virtual image acquisition devices. [4] Method according to any of the preceding claims, characterized by , that the pose (P) is determined by evaluating at least one property of the imaged mirror image or the imaged mirror element (3) or by marker-based means. [5] Method according to claim 4, characterized by , that for marker-based determination of the pose (P) at least one marker element (5) is imaged by at least one image acquisition device (5a, 5b) of the stereo camera system (1) or by another image acquisition device, wherein the at least one marker element (6) is arranged on or formed by the mirror element (3), wherein the pose (P) is determined as a function of at least one property of the imaged marker element (6). [6] Method according to any of the preceding claims, characterized by , that a focus position of the operating microscope (2) is set depending on the pose (P) of the mirror element (3). [7] Method according to any of the preceding claims, characterized by , that the radiation captured to generate the images (I5a, I5b) of the stereo camera system (1) is filtered. [8] Method according to claim 7, characterized by that the filtering is a polarization filter. [9] Method according to claim 7 or 8, characterized by , that a filter element is arranged in an illumination beam path and / or in an imaging beam path (11a, 11b) and / or on the mirror element (3). [10] Method according to any of the preceding claims, characterized by , that at least one section of the dental arch (Z) is illuminated with radiation with predetermined radiation properties. [11] Method according to claim 10, characterized by , that the radiation is generated with predetermined polarization properties. [12] Method according to any of the preceding claims, characterized by, that the images (I5a, I5b) produced by the stereo camera system are filtered, whereby the three-dimensional image (A, A2) is determined as a function of at least the filtered images. [13] Method according to any of the preceding claims, characterized by , that at least one quality measure of the three-dimensional image (A, A2) is determined, whereby user information is generated if the quality measure is less than a predetermined threshold. [14] System for generating a three-dimensional image (A, A2) of at least a section of a row of teeth (Z), comprising a stereo camera system (1) comprising a first and at least one further image acquisition device (5a, 5b) and at least one evaluation device (10), characterized by that the system is configured to perform the following steps: a. Detection of a mirror image (S5a, S5b) in an image (I5a) produced by the first image acquisition device (5a) and in an image (15b) produced by the further image acquisition device (5b), wherein the mirror image is produced by a mirror element (3) that is arranged in a detection area (4) of the stereo camera system (1) and that reflects at least one part of the row of teeth (Z), b. Determining a pose (P) of the mirror element (3), c. Determination of the three-dimensional image (A, A2) depending on at least the imaged mirror images (S5a, S5b) and the pose (P) of the mirror element (3). [15] System according to claim 14, characterized by , that the system includes a mirror element (3). [16] Computer program, wherein the computer program comprises software means for performing one, several or all steps a) to c) of the method according to any one of claims 1 to 13, when the computer program is executed by or in a computer or an automation system.

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