Methods for adjusting and / or calibrating a medical microscope and medical microscope

Abstract

Method for adjusting and / or calibrating a medical microscope (1), wherein for at least one observer beam path (2) of the medical microscope (1): images (10) of an object (40) at different magnification levels of a zoom optic (3) of the at least one observer beam path (2) are acquired by means of a detection device (4) of the at least one observer beam path (2), and a zoom center (20) is determined based on the acquired images (10), and i) further images (11) of the object (40) at different axis positions of at least one linear or rotary axis of motion (5-1,5-2) of the medical microscope (1) are acquired, and a rotation (21) of the detection device (4) relative to the at least one linear or rotary axis of motion (5-1,5-2) is determined based on the acquired further images (11).and / orii) in an eccentric imaging optic of the medical microscope (1), further images (11) of the object (40) are acquired in different focal planes and / or at different working distances, wherein a rotation (21) of the acquisition device (4) is determined based on the acquired further images (11), and wherein a reference mark (22) is determined based on the determined zoom center (20) and the determined rotation (21) and is provided for adjustment and / or calibration.

Description

The invention relates to a method for adjusting and / or calibrating a medical microscope and a medical microscope. For the alignment of medical visualization systems, especially medical microscopes, so-called zero tubes are used. These tubes, through a strict mechanical tolerance chain (from the optics to the dovetail interface on which the zero tube is mounted), attempt to define the optical center of the visualization system's primary observer. The zero tube contains a reticle engraved with a crosshair that represents the optical center. Other components of the visualization system (camera, image mirror, autofocus laser, etc.) are aligned to this optical center. The information about the position and rotation of the crosshair is lost after alignment when the zero tube is removed and can only be recovered in the field through a service call. DE 10 2019 131 646 A1 describes, for the simplification of the optical calibration of an optical observation device, a tripod for an optical observation unit with a calibration object arranged directly on the tripod and fixed in position. Furthermore, an optical observation device comprising such a tripod and an optical observation unit connected to the tripod, a method for calibrating such an optical observation device, and a computer program are described. German patent DE 10 2012 024 737 A1 describes a method for correcting parcentricity in zoom systems, particularly for stereomicroscopes and macroscopes. The method measures the positional difference in the image between at least two different zoom settings in order to determine, explicitly or implicitly, the position in the image that remains fixed during zooming (zoom center). From this, the required travel distances of a means for positioning the object in the object plane are calculated to correct the zoom-dependent parcentricity error. These distances are then used as a control variable for the corresponding positioning of the means for positioning the object in the object plane, so that the target position appears fixed in the image after or even during zooming. German patent DE 10 2013 222 295 A1 describes a digital microscope with a swivel stand, a method for its calibration, and a method for automatic focus and image center tracking when the swivel stand is actuated. The swivel stand includes an angle sensor for determining the current swivel angle of the swivel arm. The current swivel angle is processed in the control unit to perform automatic focus tracking and / or center tracking when the swivel arm is actuated. Calibration is performed using two swivel angles, whereby differing focus and image center positions are determined, and a swivel-angle-dependent function for the focus and image center position is derived from these. The invention is based on the objective of improving, and in particular simplifying, a method for adjusting and / or calibrating a medical microscope and a medical microscope. The problem is solved according to the invention by a method with the features of claim 1 and a medical microscope with the features of claim 15. Advantageous embodiments of the invention are set forth in the dependent claims. One of the fundamental ideas of the invention is to create a reference mark for adjustment and / or calibration by utilizing functions of the medical microscope, thus eliminating the need for an additional zero tube. For this purpose, an optical center of at least one observer beam path and a rotation of the observer beam path are determined by means of a rotation of a detection device of the at least one observer beam path relative to linear or rotational axes of motion and / or to axes of symmetry and / or planes of symmetry of an imaging optic of the medical microscope. This is achieved by capturing images of an object positioned within a detection area at various magnification levels of a zoom optic within the medical microscope's observation beam path, using a detection device within the observation beam path. Based on these captured images, a zoom center is determined. Specifically, the zoom center is the point in the captured images that remains constant between the different magnification levels. The zoom center is thus considered the optical center of the observation beam path. Furthermore, in an alternative approach, additional images of the object are acquired in various axial positions along at least one linear or rotary axis of the medical microscope, perpendicular to the optical axis of the observed beam path. Based on these acquired images, a rotation, specifically a rotation angle or difference angle, of the acquisition device relative to the at least one linear or rotary axis is determined. Ideally, that is, with correct alignment of the acquisition device to the at least one linear or rotary axis (particularly considering optical imaging in the observed beam path), the object in the images would shift in a desired direction (e.g., along the coordinate axes of an image sensor of the acquisition device) as it moves along the linear or rotary axis.If, however, the intended direction is not parallel to the linear axis of motion under consideration or perpendicular to the rotational axis of motion of the medical microscope, then a rotation (in particular a rotation angle or difference angle) of the scanning device relative to the linear or rotational axis of motion is present. That is, the intended direction is twisted relative to the linear or rotational axis of motion of the medical microscope or exhibits a difference angle to the linear or rotational axis of motion under consideration. The intended direction is determined, in particular, by the depicted orientation of the axis positions of the at least one linear or rotational axis of motion in a captured image, assuming ideal adjustment and / or calibration of all components of the medical microscope.In the case of a rotary axis of motion, the desired direction, due to the rotation around the rotary axis, is perpendicular to the rotary axis. The desired direction corresponds, in particular, to the direction of travel of the at least one linear or rotary axis of motion, as imaged onto an image sensor of the acquisition device via the considered observer beam path, as it would run in an ideal model of the medical microscope. By scanning along the at least one linear or rotary axis of motion and acquiring further images at different axis positions, the rotation, in particular the rotation angle or difference angle, can be determined. Alternatively or additionally, in the case of an eccentric, in particular stereoscopic, imaging optic of the medical microscope, it is provided that further images of the object are captured in different focal planes and / or at different working distances, whereby a rotation of the capture device of the imaging optic is determined based on the captured further images. For example, in the case of a simple eccentric stereoscopic imaging optic of a medical microscope, it is additionally or alternatively provided that further images of the object are acquired at a constant working distance in different focal planes. Based on these acquired images, a rotation of the acquisition device is determined, particularly relative to a reference line and / or an axis and / or plane of symmetry of the stereoscopic imaging optic. The axis of symmetry is defined here, in particular, with respect to a cross-section through a main objective of the imaging optic. Due to the change in the focal plane, a stereo angle of the stereoscopic imaging optic changes. The magnification is preferably kept constant. If the magnification varies, it can be compensated for, in particular, by computation and / or image processing.Changing the stereo angle alters the imaged object area. The object's features move in subsequent images, ideally along a straight line, neglecting or subtracting distortion. This straight line coincides with an axis and / or plane of symmetry of the stereoscopic imaging optics. Specifically, it is the line along which the focal points of the respective beam paths move towards or away from each other when the stereo angle is changed. The direction of this line, and thus the direction of the reference line and / or axis and / or plane of symmetry of the imaging optics, can be determined from the movement of the features in the captured images. Subsequently, the rotation of the scanning device can be determined based on this determined reference line and / or axis and / or plane of symmetry. Alternatively or additionally, for example in the case of a double-eccentric stereoscopic imaging optic of a medical microscope, it is provided that further images of the object are acquired, particularly at constant magnification, while the object is positioned at different distances from the imaging optic. Based on these acquired further images, a rotation of the acquisition device is determined, particularly relative to a reference line and / or an axis and / or plane of symmetry of the stereoscopic imaging optic. If the object is moved towards the imaging optic while otherwise constant settings are maintained (particularly in the z-direction if the acquisition area maps an xy-plane), the features of the object in the further images of the respective beam paths move in one direction, neglecting distortion in each beam path.For the two beam paths of the stereoscopic imaging optics, these directions are determined based on the features shown in the following illustrations. These directions, in particular, define an angle. Starting from this angle, for example, an angle bisector can be determined as a reference line (especially with respect to the imaged object area), or an axis of symmetry (especially with respect to a cross-section of the main objective lens), and / or a plane of symmetry (especially with respect to the imaging optics). Alternatively, a line perpendicular to the angle bisector can be used as a reference line, axis of symmetry, and / or plane of symmetry. Subsequently, the rotation of the scanning device can be determined based on the reference line, axis of symmetry, and / or plane of symmetry thus determined. Defocusing can change the image scale. This can be modeled and / or corrected. However, this only needs to be considered for features that are not located on the axis of symmetry. Alternatively, only features near the axis of symmetry can be used. Even with a simple eccentric imaging optic, it is fundamentally possible to determine a reference line and / or axis of symmetry and / or plane of symmetry by varying the working distance. Similarly, with a double eccentric imaging optic, it is fundamentally possible to acquire further images at different focal planes. The procedure is analogous in each case. In principle, the variants can be combined in a single embodiment. Starting from the determined zoom center and the determined rotation, in particular the rotation angle or difference angle, a reference mark (especially in the form of a crosshair which is reflected into the observer beam path) is determined and provided for adjustment and / or calibration. In particular, a method for adjusting and / or calibrating a medical microscope is provided, wherein for at least one observer beam path of the medical microscope: images of an object at different magnification levels of a zoom optic of the at least one observer beam path are captured by means of a detection device of the at least one observer beam path, and a zoom center is determined from the captured images, and i) further images of the object, in particular at a constant magnification, are captured in different axis positions of at least one linear or rotational axis of movement of the medical microscope, in particular perpendicular to the optical axis of the at least one observer beam path.wherein, based on the captured additional images, a rotation of the capture device relative to at least one linear or rotary axis of movement is determined, and / or ii) in the case of an eccentric, in particular stereoscopic, imaging optic of the medical microscope, further images of the object are captured in different focal planes and / or at different working distances, wherein, based on the captured additional images, a rotation of the capture device is determined, and wherein a reference mark is determined based on the determined zoom center and the determined rotation and is provided for adjustment and / or calibration. Furthermore, a medical microscope is provided, in particular comprising at least one observer beam path with a zoom optic, a detection device, and at least one linear or rotary axis of movement, which is arranged in particular perpendicular to an optical axis of the at least one observer beam path, and / or an eccentric, in particular stereoscopic, imaging optic; and a control device, wherein the control device is configured to determine a zoom center in detected images, which are or have been detected of an object at different magnification levels of the zoom optic by means of the detection device;i) to determine a rotation of the detection device relative to the at least one linear or rotary axis of movement starting from captured additional images, which are or were captured of the object, in particular at constant magnification, in different axis positions of the at least one linear or rotary axis of movement of the medical microscope, in particular perpendicular to the optical axis of the at least one observer beam path; and / or ii) in the case of an eccentric, in particular stereoscopic, imaging optic of the medical microscope, to determine a rotation of the detection device starting from captured additional images, which are or were captured of the object in different focal planes and / or at different working distances;and to determine a reference mark starting from the specified zoom center and rotation, and to provide it for adjustment and / or calibration. One advantage of this method and the medical microscope is that a reference mark can be established at any time, eliminating the need for a null tube for adjustment and / or calibration. This allows components of the observer beam path of the medical microscope to be adjusted and / or calibrated even after initial setup and / or calibration, without requiring additional service. This ensures that the visualization quality can be verified and maintained consistently. The zoom center is determined in particular with respect to the coordinates or coordinate axes of image elements of an image sensor of the acquisition device of the at least one observer beam path and / or the coordinates or coordinate axes of the corresponding captured images. The rotation is also determined in particular with respect to the coordinates or coordinate axes of the image elements of the image sensor of the at least one observer beam path and / or the coordinates or coordinate axes of the corresponding captured images. However, other reference systems can also be chosen. A medical microscope is specifically a surgical microscope. However, a medical microscope can also be a microscope used for medical examinations and / or diagnostic purposes, for example in the field of ophthalmology. A common main objective of a stereoscopic imaging system, shared by a right and a left beam path, has two axes of symmetry, particularly with respect to the image or a cross-section of the main objective. These axes are perpendicular to each other and intersect at the center of the main objective. The axes of symmetry of the cross-section coincide with planes of symmetry of the imaging system. In a simply eccentric stereoscopic imaging system, the respective optical axes of the right and left beam paths do not pass through the center of the main objective, but rather traverse it away from either of the axes of symmetry or planes of symmetry.In a double eccentric stereoscopic imaging optic, the respective optical axes of the right and left beam paths do not pass through the center of the main objective, but rather pass through the main objective away from both axes or planes of symmetry. Parts of the medical microscope, particularly the control unit, can be designed individually or collectively as a combination of hardware and software, for example, as program code executed on a microcontroller or microprocessor. However, it is also possible for parts to be designed individually or collectively as an application-specific integrated circuit (ASIC) and / or a field-programmable gate array (FPGA). In one embodiment, the provision includes displaying the reference mark on at least one display device of the medical microscope. This allows the reference mark to be visually detected and used during adjustment and / or calibration. A display device can be either an external display device or a display device within the at least one observer beam path of the medical microscope. The display device can, for example, be a projection device that can project information and / or images into the observer beam path so that they can be displayed alongside and / or superimposed on a detection area captured by an imaging optic. In one embodiment, the defined reference mark is displayed as a virtual zero tube on the at least one display unit of the medical microscope. This allows adjustment and / or calibration to be performed in a known manner, similar to a physical zero tube. In particular, such a virtual zero tube can include a crosshair, the center of which corresponds to the defined zoom center, and one of the lines of which runs parallel to the at least one linear or rotational axis of movement of the medical microscope. In one embodiment, the detection device is adjusted and / or calibrated using the reference mark. Specifically, it is provided that any rotation of the detection device relative to at least one linear or rotary axis of motion is corrected by adjusting the device so that the specific rotation (in particular, a rotation angle or difference angle) disappears. Alternatively or additionally, it may be provided that the specific rotation is corrected by calibration. This is achieved, in particular, by rotating images captured by the detection device using (digital) image processing. In one embodiment, a mirroring device for the at least one observer beam path is adjusted and / or calibrated relative to a specific reference mark. Since information reflected into the at least one observer beam path by the mirroring device is also detected by the detection device of the at least one observer beam path, the position and orientation of the reflected information can be compared with the specific reference mark. Based on the comparison result, the mirroring device can then be adjusted and / or calibrated. For example, it may be possible to reflect a crosshair using the mirroring device and compare this crosshair with a crosshair of the reference mark.By comparing them, deviations in both relative position and orientation can be determined and used for adjustment and / or calibration. In one embodiment, a reference object is aligned to a specific reference mark, and components of the medical microscope are adjusted and / or calibrated using this reference object. This allows for the simple provision of a physically available reference object, which can then be used to adjust and / or calibrate components of the at least one observer beam path. Additionally, the reference object can be aligned in focus by contrast analysis of the image. For example, the reference object can be aligned manually by placing it within the field of view of the medical microscope and positioning and aligning it using the displayed reference mark, such as the virtual null tube.Subsequently, the components, including the detection device of the at least one observer beam path and / or a display device, such as a mirroring device, can be adjusted and / or calibrated using the positioned and aligned reference object. For this purpose, a user can detect the reference object and the (mirrored) reference mark through an eyepiece or via the display device of the medical microscope, whereby the reference mark is displayed by means of a display device, in particular a mirroring device, in the at least one observer beam path. Alternatively or additionally, an external display device can be used, on which the detection area with the reference object and the reference mark are displayed. The reference mark can then be determined again, and the adjustment and / or calibration performed can be checked. In one embodiment, the specified reference mark is stored, and the state of the medical microscope is monitored based on this stored reference mark and at least one further reference mark determined at a later time. This allows for the improvement, and especially automated monitoring, of the medical microscope's condition, particularly with regard to mechanical adjustment and / or calibration. For example, a reference mark acquired at a later time can be compared with the stored reference mark. Deviations between the zoom centers and the rotations of the reference marks can then be determined and compared with respective threshold values.If one of the threshold values ​​is exceeded, this can be communicated to a user and / or a service technician, and / or a service signal and / or an adjustment signal can be generated to indicate the need for readjustment and / or calibration and / or replacement of a component. For example, it may be possible to automatically check for such a deviation when the medical microscope is powered on and / or shut down. In one embodiment, a reference mark is determined for each detection device and / or each observer beam path of the medical microscope, and the detection devices and / or components of the observer beam paths are adjusted and / or calibrated relative to each other based on these respective reference marks. This allows, in particular, the correction of binocular aberration in stereomicroscopes with two observer beam paths, thus improving three-dimensional imaging. In one embodiment, the zoom center is determined by identifying and correspondingly assigning identical features in images captured at different zoom levels. The zoom center is then determined by the intersection of lines formed by connecting the corresponding features in the superimposed images. These measures, particularly the necessary feature recognition, are performed by the control unit of the medical microscope. For example, known computer vision and pattern recognition methods can be used. Known machine learning and artificial intelligence methods, especially in the areas of pattern recognition and feature extraction, can also be employed. If a zoom center is defined for different zoom ranges (each encompassing at least two zoom levels), ideally the zoom center should remain stationary. However, a shift in the zoom center or a positional difference between specific zoom centers in different zoom ranges can be used to detect inferior and / or faulty optics. This can be achieved by defining a zoom center for each zoom range, comparing the positions of these centers, and then comparing any positional differences between them to a predefined threshold. If the position difference exceeds the specified threshold, an (error) signal or (error) message is generated and provided, in particular output. It may also be possible, additionally or alternatively, to compare the intersection point of the lines for different zoom ranges (each comprising at least two zoom levels). The dispersion of the intersection point positions can then be used as a measure for a quality criterion to evaluate an optical system and / or its condition. For this purpose, an intersection point of the lines can be determined in each of the different zoom ranges, the positions of these intersection points are compared, and any position difference between the intersection points is compared to a predefined threshold. If a position difference exceeds the predefined threshold, an (error) signal is generated and provided, in particular, output. In one embodiment, it is provided that, to determine the rotation, identical features in the captured images are recognized and assigned to one another. Starting from these identical features, a displacement direction of the same features is determined with respect to the superimposed captured images, and the rotation is then determined based on this displacement direction. These measures, in particular the necessary feature recognition, are carried out by the control unit of the medical microscope. For example, known computer vision and pattern recognition methods can be used for this purpose. Known machine learning and artificial intelligence methods can also be used, especially in the areas of pattern recognition and feature extraction.The rotation can then be determined, for example, by comparing the direction of displacement with a target direction (e.g., a coordinate axis of the detection device). In one embodiment, the zoom center is determined by evaluating the optical flow in the captured images. The zoom center is then the point in the captured images that does not move, or moves the least. The necessary measures for this are carried out by means of the control unit of the medical microscope. In one embodiment, the optical flow in the captured images is evaluated to determine the rotation. Specifically, a displacement direction is determined based on the optical flow and compared to a target direction. Based on this comparison, the rotation, particularly a rotation angle or difference angle, can be determined. The necessary steps are performed using the control unit of the medical microscope. In one embodiment, the object comprises a checkerboard pattern and / or a Charucoboard. This allows for particularly easy-to-recognize features to be provided on the object. Pattern recognition and position determination of the features in the captured images and other captured images can thus be improved. In one embodiment, the zoom center is used as the center for a digital zoom. For this purpose, the reference mark is determined, stored, and made available as a parameter value for a digital zoom function of a display device. In one embodiment, it is provided that only a sub-area of ​​the captured images near the zoom center is used to determine the rotation. This sub-area is, in particular, a predefined sub-area. This can reduce the computing power required for evaluation. Furthermore, it can also reduce or eliminate any distortion effects that may be present, which decrease with distance from the zoom center. Further features for the design of the medical microscope emerge from the description of the various embodiments of the process. The advantages of the medical microscope are the same in each case as in the embodiments of the process. The invention is explained in more detail below with reference to preferred embodiments and the figures. Figure 1 shows a schematic representation of one embodiment of the medical microscope; Figure 2 shows a schematic representation to illustrate one embodiment of the method and the medical microscope (determining the zoom center); Figure 3 shows a schematic representation to illustrate another embodiment of the method and the medical microscope (determining the rotation); Figures 4a-d show schematic representations of captured images of an object comprising a Charucoboard at various magnification levels to illustrate one embodiment of the method and the medical microscope.4e A schematic representation of superimposed captured images at different zoom levels to illustrate an embodiment of the method and the medical microscope (determining the zoom center); Fig. 5 A schematic representation of further captured images of an object comprising a Charucoboard at different axis positions to illustrate an embodiment of the method and the medical microscope (determining the rotation); Fig. 6 A schematic representation of an image captured by means of a misaligned capture device with a reference mark shown therein to illustrate an embodiment of the method and the medical microscope; Fig. 7 A schematic representation to illustrate a further embodiment of the method and the medical microscope; Fig.8 a schematic flowchart of an embodiment of the method for adjusting a medical microscope; Figs. 9a-9d schematic illustrations to explain a variant of the method and the medical microscope; Figs. 10a-10f schematic illustrations to explain another variant of the method and the medical microscope. Figure 1 shows a schematic representation of an embodiment of the medical microscope 1. The medical microscope 1 comprises an observer beam path 2 with a zoom optic 3, a detection device 4, for example, a camera, and two linear or rotary axes of movement 5-1, 5-2, which are arranged perpendicular to an optical axis 6 of the observer beam path 2. For clarity, only one observer beam path 2 is shown; however, the medical microscope 1 can, in principle, also comprise more than one observer beam path, in particular two observer beam paths. Furthermore, the medical microscope 1 comprises a control unit 7. The control unit 7 comprises, for example, a computing unit 7-1, for example, a microprocessor, and a memory 7-2. The method described in this disclosure is explained in more detail below with reference to the medical microscope 1. In particular, the medical microscope 1 further comprises a stand 8 which is arranged on an actuator 9. Via the stand 8, the actuator 9 can move the observer beam path 2 along the linear or rotational axes of movement 5-1, 5-2. The zoom optics 3, the detection device 4 and the actuators 9 are controlled or regulated by means of the control unit 7. The control unit 7 is configured to determine a zoom center 20 in the captured images shown in Fig. 10, each of which is or was captured by an object 40 at different magnification levels of the zoom optics 3 using the detection unit 4. The different magnification levels are set automatically at the zoom optics 3 by means of the control unit 7, for which purpose the control unit 7 generates control signals 30 and supplies them to the zoom optics 3. However, this can also be done manually or in another way. Furthermore, the control unit 7 is configured in one variant to determine a rotation 21, in particular a rotation angle or differential angle, of the detection unit 4 relative to the linear or rotary axis of movement 5-1, based on further detected objects (Fig. 11), which are or were detected by the object 40, particularly at constant magnification, in different axis positions of the linear or rotary axis of movement 5-1 of the medical microscope, which runs perpendicular to the optical axis 6 of the observer beam path 2. The different axis positions are set at the actuator 9, in particular by means of the control unit 7, for which purpose the control unit 7 generates control signals 31 and supplies them to the actuator 9. In another variant, alternatively or additionally in the case of an eccentric, in particular stereoscopic, imaging optic 12 of the medical microscope 1, it is provided that the control device 7 is configured to determine a rotation 21 of the detection device 4 starting from detected further Fig. 11, which are or were detected by the object 40 in different focal planes F1, F2 (Fig. 9a) and / or at different working distances. For example, alternatively or additionally, in the case of a simple eccentric stereoscopic imaging optic of the medical microscope 1, the control device 7 is configured to determine a rotation 21 of the detection device(s) 4 relative to an axis of symmetry (with respect to a detected object area or a cross-section through the main objective) and / or plane of symmetry (with respect to the imaging optic) of the stereoscopic imaging optic, starting from detected further objects (Fig. 11), which are or were detected by the object 40 at a constant magnification in different focal planes. This variant is explained schematically below with reference to Figs. 9a to 9d. Alternatively or additionally, for example, in the case of a double eccentric stereoscopic imaging optic of the medical microscope 1, the control device 7 is configured to determine a rotation 21 of the detection device(s) 4 relative to an axis and / or plane of symmetry of the stereoscopic imaging optic, starting from further detected objects (Fig. 11), which are or were detected by the object 40, particularly at a constant magnification, while the object 40 is or is arranged at different distances from the imaging optic 12. This variant is explained schematically below with reference to Figs. 10a to 10f. The control unit 7 then determines a reference mark 22 starting from the determined zoom center 20 and the determined rotation 21 and provides the determined reference mark 22 for adjustment and / or calibration. A medical microscope 1 typically has several, in particular two, linear or rotary axes of motion 5-1, 5-2 arranged perpendicular to each other and perpendicular to the optical axis 6 of the observer beam path 2. The measures for determining the rotation 21 (in particular the rotation angle or difference angle) according to the first variant can then be carried out analogously for the further, in particular second, linear or rotary axis of motion 5-2. The provision of the information may include displaying the reference mark 22 on at least one display device 15 of the medical microscope 1. The display device 15 may, for example, be a computer monitor 16. Furthermore, the display device 15 may be a reflection device 17 of the medical microscope 1, by means of which information (in particular via a semi-transparent mirror) can be reflected into the observer beam path 2 so that it can be detected both by an eyepiece and by a sensor of the detection device 4. In particular, it can be provided that the specific reference mark 22 is displayed in the form of a virtual zero tube on the at least one display device 15 of the medical microscope 1. Such a virtual zero tube includes, in particular, a crosshair. It may be provided that the detection device 4 is adjusted and / or calibrated using the reference mark 22. For this purpose, the defined reference mark 22, in particular a virtual zero tube in the form of a crosshair, can be displayed, for example, by means of the projection device 17 and projected into the observer beam path 2. The detection device 4 is then adjusted, in particular mechanically, such that the center of the image coincides with the projected reference mark 22 and the path of a two-dimensional grid of image elements of the sensor of the detection device 4 corresponds to the path of the lines of the crosshair. Subsequently, a new reference mark 22 can be determined and the adjustment and / or calibration of the detection device 4 can be checked. Furthermore, it may be provided that the reflection device 17 of the observer beam path 2 is adjusted and / or calibrated starting from the specified reference mark 22. For this purpose, the reflection device 17 is adjusted and / or calibrated, in particular to the reference mark 22, especially using a virtual zero tube in the form of a crosshair. It may be provided that a reference object 41 is aligned with the specific reference mark 22, whereby components of the medical microscope 1 are adjusted and / or calibrated using the aligned reference object 41. These components may include, for example, the zoom optics 3, the detection device 4, other imaging optics, and / or the reflection device 17. It can be provided that the specified reference mark 22 is stored, and the state of the medical microscope 1 is monitored based on the stored reference mark 22 and at least one further reference mark 23 determined at a later time. For this purpose, a difference between the stored reference mark 22 and the further reference mark 23 detected at a later time is determined and compared, for example, with predefined threshold values, such as for a positional difference and for a rotational difference. If one of the threshold values ​​is exceeded, a signal can be generated, for example, indicating a misalignment of the medical microscope 1. The signal can be displayed, for example, on one of the display devices 15. The medical microscope 1 may be provided with additional observer beam paths (not shown), each with an additional detection device (not shown). It may then be provided that a reference mark 22 is determined for each detection device and / or each observer beam path of the medical microscope 1, whereby the detection devices and / or components of the observer beam paths are adjusted and / or calibrated relative to each other based on the respective determined reference marks 22. For example, a binocular error can be corrected in this way in a stereomicroscope. It may be provided that only a sub-area of ​​the captured further Fig. 11 near the zoom center 20 is used to determine the rotation 21. Figure 2 shows a schematic representation illustrating one embodiment of the method and the medical microscope. In this embodiment, the zoom center 20 is determined by identifying identical features 51-x, 52-x, 53-x in Figures 10 captured at different zoom levels and assigning them to each other. The zoom center 20 is then determined by the intersection point 54 of lines 55, 56, 57, which are formed by connecting the corresponding features 51-x, 52-x, 53-x in the superimposed Figures 10. Figure 2 shows two Figures 10 superimposed at different zoom levels. As the magnification increases, the features 51-x, 52-x, 53-x move from the inside out along the lines 55, 56, 57 in Figures 10. By connecting the respective corresponding features 51-x, 52-x, 53-x, the straight lines 55, 56, 57 are obtained, whose intersection point 54 gives the zoom center 20.The zoom center 20 hardly moves at all when the magnification is changed at the various zoom levels, and ideally not at all. Computer vision and / or machine learning methods can be used to detect and / or determine the position of features 51-x, 52-x, 53-x. It can be provided that a zoom center 20 is determined for each of the different zoom ranges, and the positions of the determined zoom centers 20 are compared with each other. Any position difference between the zoom centers 20 is then compared with a predefined threshold. If a position difference exceeds the predefined threshold, an (error) signal is generated and provided, in particular, output. It may also be provided, additionally or alternatively, to compare the intersection point 54 of lines 55, 56, 57 for different zoom ranges (each comprising at least two zoom levels). The dispersion of the position of the intersection points 54 can be used as a measure for a quality criterion to evaluate an optic and / or its condition. For this purpose, it may be provided that an intersection point 54 of lines 55, 56, 57 is determined in each of the different zoom ranges, and the position of the determined intersection points 54 is compared with each other. Any position difference between the intersection points 54 is then compared with a predefined threshold. If a position difference exceeds the predefined threshold, an (error) signal or message is generated and provided, in particular, output. Figure 3 shows a schematic representation illustrating a further embodiment of the method and the medical microscope. In this embodiment, to determine the rotation 21, in particular the rotation angle or difference angle, identical features 61-x, 62-x in the captured further images 11 are detected and assigned to each other. Starting from these identical features 61-x, 62-x, a displacement direction 63 of the same features 61-x, 62-x is determined with respect to the superimposed captured further images 11, and the rotation 21 is determined based on this determined displacement direction 63. Figure 3 shows two superimposed further images 11, which were captured at different axis positions of a linear or rotary axis of motion.Since the linear axis or a direction perpendicular to the rotational axis does not run along a coordinate axis 64 of the image elements of the image sensor of the detection device, which is defined, for example, as the target orientation and / or target direction, the further figures in Fig. 11 are rotated relative to the linear axis or the direction perpendicular to the rotational axis of movement. This rotation 21, in particular in the form of a rotation angle or difference angle, can be determined from the further figures in Fig. 11 (the rotation about the rotational axis in Fig. 11 results in a movement perpendicular to the rotational axis). For this purpose, the displacement direction 63 is determined in each case by connecting the same features 61-x, 62-x. A difference between a coordinate axis 64 of the image sensor and the displacement direction 63 results in the rotation 21 (in particular the rotation angle or difference angle). It can be provided, in particular, that the additional figures in Fig. 11 are captured and / or selected such that as many identical features 61-x, 62-x as possible are present in the additional figures in Fig. 11. Furthermore, it can be provided that the additional figures in Fig. 11 are captured and / or selected such that the distance between the identical features 61-x, 62-x in the additional figures in Fig. 11 is as large as possible. This can increase the accuracy in determining the rotation 21 (in particular the rotation angle or difference angle). Computer vision and / or machine learning methods can be used to detect and / or determine the position of the features 61-x, 62-x. The procedure is carried out analogously for a further linear or rotary axis of motion that is perpendicular to the optical axis of the observer's beam path. If a further, in particular a second, linear or rotary axis of motion is not perpendicular to a first linear or rotary axis of motion, a value averaged between the linear or rotary axes of motion can be used for a target orientation and / or target direction. It may be possible to determine the zoom center 20 by evaluating the optical flow in the captured image 10. For this purpose, the point in the captured image 10 that moves the least at the various magnification levels is identified. This point is then set as the zoom center 20. It can be provided that, to determine the rotation 21, in particular a rotation angle or difference angle, an optical flow in the captured further image in Fig. 11 is evaluated. The optical flow results from the movement of features in the captured further image in Fig. 11 when the observer beam path is moved along the linear or rotational axis of motion. From a deviation of a direction of motion determined from the optical flow and a target orientation and / or target direction, the rotation 21 (in particular the rotation angle or difference angle) can be determined, analogously to Fig. 3. It may be provided that object 40 includes a checkerboard and / or a Charucoboard 42 (Figs. 4a to 4e). This allows for particularly easily recognizable features to be provided. A Charucoboard 42 is shown by way of example in Figures 4a to 4e. The determination of the zoom center 20 is shown, as already described with reference to Figure 2. Figures 4a to 4d show Figures 10, which were acquired at different magnification levels of the zoom optics. In Figure 4e, Figures 10 shown in Figures 4c and 4d are superimposed. Lines 55 were drawn using identical features (not labeled) in both Figures 10, intersecting at a point 54. The point of intersection 54 is the zoom center 20. Figure 5 further shows the determination of a displacement direction 63 for determining the rotation using a Charucoboard 42. Here, the observer beam path is moved along two mutually perpendicular linear or rotational axes of motion in both directions, each time starting from the additional figure 11 shown in the center of Figure 5. The additional figures 11 shown above and below in Figure 5 correspond to a movement along / around one of the linear or rotational axes of motion, and the additional figures 11 shown to the left and right in Figure 5 correspond to a movement along / around the other linear or rotational axes of motion.It is assumed here that the linear or rotational axes of motion are arranged perpendicular to each other and perpendicular to the optical axis of the observer beam path through which a detection device captures the further Fig. 11. A movement about a rotational axis of motion leads, in particular, to a movement perpendicular to the rotational axis of motion in the captured Fig. 11. The direction of displacement 63 is illustrated by one of the Aruco-IDs of the Charucoboard 42, which in each case shifts from the center of the further Fig. 11 shown in the center of Fig. 5 to an edge region of the respective subsequent further Fig. 11 (indicated by the respective arrows). The rotation (in particular a rotation angle or difference angle) is determined starting from the determined direction of displacement 63, as already explained above with reference to Fig.3 was explained, taking into account the results for both linear or rotational axes of motion. Figure 6 shows a schematic representation of Figure 10, captured by a misaligned detection device, with a reference mark 22 displayed therein to illustrate an embodiment of the method and the medical microscope. In this embodiment, the reference mark 22 is displayed on a display device. It is particularly intended to display the specific reference mark 22 together with a captured Figure 10 on a display device 15 (Figure 1). For example, it may be possible to reflect the specific reference mark 22 into the observer beam path 2 (Figure 1) by means of a reflection device 17, so that it can be captured via an eyepiece and / or by means of the detection device 4. The reference mark 22 has the form of a crosshair, with the intersection of the lines of the crosshair corresponding to the zoom center.In the example shown, an orientation of the crosshairs corresponds to the rotation 21, in particular a rotation angle or difference angle, in each case between coordinate axes of a coordinate system of an image sensor of the detection device 4 and the linear or rotational axes of movement 5-1, 5-2 ( Fig. 1 ). Figure 7 shows a schematic representation illustrating one embodiment of the method and the medical microscope. This embodiment provides that a reference object 41 is aligned with a specific reference mark 22, and components of the medical microscope are adjusted and / or calibrated using the aligned reference object 41. The reference object 41 shown in Figure 7, for example, has several line markings 43 that run parallel and perpendicular to each other. The alignment of the line markings 43 is manually determined using the reference mark 22, i.e., the crosshairs. After alignment, the components of the medical microscope can be adjusted using the aligned reference object 41 (see also Figure 1).The detection device can also be adjusted, whereby in the example shown the detection device would have to be rotated clockwise by a specific rotation, in particular by a specific rotation angle or difference angle, so that a course of coordinate axes of an image sensor of the detection device corresponds with the line markings 43 of the reference object 41. Figure 8 shows a schematic flowchart of an embodiment of the method for adjusting and / or calibrating a medical microscope. The method is explained below for one observer beam path of the medical microscope. However, the process steps can be carried out in the same way for other observer beam paths. In process step 100, images of an object at different magnification levels of a zoom optic of the observer beam path are captured by means of a detection device of the observer beam path. In process step 101, a zoom center is determined based on the captured images. In process step 102, further images of the object are acquired at a constant magnification in various axis positions of at least one linear or rotary axis of movement of the medical microscope, in particular one that runs perpendicular to the optical axis of the at least one observer beam path. Further images are acquired at at least two axis positions. In a process step 103, starting from the captured further images, a rotation, in particular a rotation angle or difference angle, of the capture device relative to at least one linear or rotary axis of movement, which can be defined as the target orientation and / or target direction, is determined. Alternatively or additionally, in process step 102, with an eccentric imaging optic of the medical microscope, further images of the object can be acquired in different focal planes and / or at different working distances. Based on these acquired additional images, a rotation of the acquisition device is determined, in particular relative to an axis of symmetry (with respect to a cross-section of the main objective) and / or a plane of symmetry (with respect to the imaging optic). In process step 103, based on these acquired additional images, a rotation of the acquisition device is determined, in particular relative to the axis of symmetry and / or plane of symmetry of the stereoscopic imaging optic. For example, alternatively or additionally, in process step 102, with a simple eccentric stereoscopic imaging optic of the medical microscope, further images of the object, particularly at constant magnification, can be acquired in different focal planes. In process step 103, based on these acquired additional images, a rotation of the acquisition device relative to an axis and / or plane of symmetry of the stereoscopic imaging optic is determined. For example, alternatively or additionally, in process step 102, with a double-eccentric stereoscopic imaging optic of the medical microscope, further images of the object could be acquired, particularly at a constant magnification, while the object is positioned at different distances from the imaging optic. In process step 103, based on the acquired additional images, a rotation of the acquisition device relative to an axis and / or plane of symmetry of the stereoscopic imaging optic is determined. In process step 104, a reference mark is determined based on the specified zoom center and rotation and provided for adjustment and / or calibration. The reference mark can, for example, include a crosshair. In process step 105, it may be provided that the provisioning includes displaying the reference mark on at least one display unit of the medical microscope. In particular, it may be provided that the specific reference mark is displayed on the at least one display unit of the medical microscope in the form of a virtual null tube (e.g., in the form of a crosshair). In process step 106, it may be provided that the detection device is adjusted and / or calibrated using the reference mark. Furthermore, in a process step 107 it may be provided that a reflection device of the at least one observer beam path is adjusted and / or calibrated starting from the specified reference mark. In a process step 108, it may be provided that a reference object is aligned to the specific reference mark, whereby components of the medical microscope, in particular components of a respective observed beam path, are adjusted and / or calibrated on the basis of the aligned reference object. In process step 109, it may be provided that the specified reference mark is stored, and the state of the medical microscope is monitored based on the stored reference mark and at least one further reference mark determined at a later time. This can be achieved, for example, by projecting the stored reference mark into the observed beam path using a projection device, whereby the projection is detected by the observer beam path's detection device and compared with the further specified reference mark. Furthermore, it can be verified whether the reference mark is still at the same position in the image sensor's coordinate system at a later time. Based on a comparison result, readjustment and / or recalibration can then be initiated. Further embodiments of the method have already been described with reference to Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7. Figures 9a to 9d show schematic representations to illustrate a variant of the method and the medical microscope. In the case of a simple eccentric stereoscopic imaging optic 12 of the medical microscope 1 (Fig. 1), the control device 7 (Fig. 1) is configured to determine a rotation 21 of the detection device 4 (Fig. 1) relative to an axis of symmetry 13 (with respect to a cross-section of a main objective 12o) of the stereoscopic imaging optic 12, starting from detected further objects (Fig. 11), which are or were detected by the object 40 at a constant magnification in different focal planes F1, F2. It should be noted that the focal planes F1 and F2 for the two beam paths 12l, 12r are, in reality, tilted relative to each other due to the stereo angle.intersect at the stereo angle; however, this is neglected for the sake of simplicity in the present illustration. Fig. 9a schematically shows the stereoscopic imaging optics 12. When the focal plane F1, F2 is changed, a stereo angle between the left beam path 12l and the right beam path 12r changes. Fig. 9b schematically shows the imaging through the main objective 12o as a cross-section. With respect to the cross-section, there are two axes of symmetry 13, 14, which are perpendicular to each other and intersect at the center of the main objective 12o. The axis of symmetry 14 coincides with the plane of symmetry 24 of the main objective 12o shown in Fig. 9a.In a simple eccentric stereoscopic imaging optic 12, as assumed here by way of example, the respective optical axes 6l, 6r of the left beam path 12l and the right beam path 12r do not pass through the center of the main objective 12o, but rather traverse the main objective 12o away from the axis of symmetry 14. The optical axes 6l, 6r, however, lie on the axis of symmetry 13. Fig. 9c shows, by way of example, two further Fig. 11 images captured by the object 40 in different focal planes F1, F2, which are superimposed (further Fig. 11 images captured by only one of the beam paths 12l, 12r are sufficient here). Identical features 61-x, 62-x shift with respect to the image elements that depict these features 61-x, 62-x. Therefore, an optical flow can be determined in particular in the form of a vector field of parallel vectors or a displacement direction 63. This displacement direction 63 coincides with the axis of symmetry 13 (or...).the corresponding plane of symmetry). Between a coordinate axis 64 of the detection device 4 (or an image sensor of the detection device 4), which specifies an actual orientation, and the displacement direction 64, the rotation 21 can be determined in the form of a deviation or difference angle, as indicated in Fig. 9c. The orientation of the symmetry axis 13 can subsequently be used as the target orientation or target direction to which the coordinate axis 64 of the detection device 4 (or of the image sensor of the detection device 4) is adjusted (so that the target orientation and the coordinate axis 64 are subsequently at least parallel to each other). Figure 9d shows a further schematic representation to illustrate the variant with a simple eccentric stereoscopic imaging optic 12. It shows a respective object region 25l, 25r that is imaged and captured when the focus changes (which is indicated by the suffix appended to the reference symbol). If the focus of the main objective 12o changes, the imaged object region 25l, 25r also changes. At focus, the object regions 25l-1, 25r-1 are superimposed, meaning that the left and right optical images each image the same object region 25l-1, 25r-1. When defocused, the left beam path 12l and the right beam path 12r image object regions 25l-2, 25r-2 that are offset from each other. Features 61, 62 (only two are shown with a reference symbol as examples) move during defocusing, in particular in a direction parallel to the axis of symmetry 13. Figures 10a to 10f show schematic representations to illustrate a further variant of the method and the medical microscope. In the case of a double eccentric stereoscopic imaging optic 12 of the medical microscope 1 (Fig. 1), the control device 7 (Fig. 1) is configured to determine a rotation 21 of the detection device 4 (Fig. 1) relative to an axis of symmetry 13, 14 of the stereoscopic imaging optic 12, starting from detected further objects (Fig. 11, 11l, 11r) that are or were detected by the object 40, at a particularly constant magnification, while the object 40 is or is arranged at different distances from the imaging optic 12. Fig. 10a schematically shows the stereoscopic imaging optics 12. The object 40 is moved, for example, by means of a service hook (not shown) mounted below the microscope, towards the imaging optics 12 (or...in particular parallel to the plane of symmetry 24 of the main lens), as indicated by the arrow. In principle, the object 40 can also be moved in the opposite direction. Figure 10b schematically shows the imaging through the main lens 120 as a cross-section. With reference to the cross-section of the main lens 120, there are two axes of symmetry 13, 14, which are perpendicular to each other and intersect at the center of the main lens 120. In a double eccentric stereoscopic imaging optic 12, as assumed here by way of example, the respective optical axes 6l, 6r of the left beam path 12l and the right beam path 12r do not pass through the center of the main objective 12o, but rather pass through the main objective 12o away from both axes of symmetry 13, 14. Fig. 10c shows, by way of example, two superimposed left-hand images (Fig. 11l) which were captured by the left beam path 12l for different object positions.Fig. 10d shows, by way of example, two superimposed right-hand images, Fig. 11r, which were accordingly captured by the right-hand beam path 12r for the different object positions. At focus, the respective optical axis 6l, 6r (or the specific zoom center 20) always hits the same object point, so that this point rests in Fig. 11l, 11r; that is, an object point is always imaged onto the same image elements of the acquisition device. If the object is moved towards the imaging optics 12 (or, in particular, parallel to the plane of symmetry 24 of the main objective) while all other settings remain constant, a feature 61-x, 62-x of the object 40 moves in a specific direction in both beam paths 12l, 12r as the distance between the object 40 and the imaging optics 12 decreases. These directions are determined for the two beam paths 12l, 12r of the stereoscopic imaging optics 12. Starting from these directions, for example, an angle bisector 19 (Fig. 10b) can be determined as the axis of symmetry 14. Alternatively, a direction perpendicular to the angle bisector 19 in the object region can be used as the axis of symmetry 13. Subsequently, the rotation 21 of the detection device(s) 4 can be determined starting from the axis of symmetry 13, 14 thus determined, for example, by defining a coordinate axis of the detection device 4 (orThe position of an image sensor of the detection device 4 is compared with the axis of symmetry 13, 14, and in particular a difference angle is determined as a rotation 21. The axis of symmetry 13, 14 determined in this way then serves in particular as the target direction to which the coordinate axis of the detection device 4 (or of an image sensor of the detection device 4) can be adjusted. Figures 10e and 10f show further schematic representations to illustrate the further variant with a double eccentric stereoscopic imaging optic 12. An object area 25l, 25r, imaged by a left beam path 12l and a right beam path 12r of the imaging optic 12, changes when the working distance is changed. This is shown schematically in Figure 10e for two working distances, each characterized by the suffix appended to the reference numeral. A first working distance (suffix 1) corresponds in particular to focusing, and a second working distance (suffix 2) corresponds in particular to defocusing. The displacement directions 63 of exemplary features 61, 62, which result from changing the working distance, are also shown.The displacement directions 63 are determined here, in particular with respect to an identical feature arrangement in both object areas 25l, 25r (pattern recognition methods known per se can be used to identify the features). Based on the determined displacement directions 63, an angle and an angle bisector 19 (Fig. 10b) can then be determined, as described above. Fig. 10f shows the situation with the detected object areas 25l, 25r rotated relative to each other (the rotations of the detection devices are therefore different). Here, too, the displacement directions 63, an angle between the displacement directions 63, and an angle bisector 19 in the object area can be determined, particularly due to the identical feature arrangement in both object areas 25l, 25r.The detection devices can then be adjusted to correct the respective rotation. The embodiments are explained using a stereoscopic imaging optic as an example. However, the method can also be applied analogously to a monoscopic imaging optic or a single beam path. In particular, it can be provided that, starting from a displacement direction 63 determined by changing the focal plane and / or at different working distances, a reference direction or target direction is defined as a reference mark to which a coordinate axis of the detection device 4 (or the image sensor of the detection device 4) can be adjusted. Reference symbol list 1 Medical microscope 2 Observer beam path 3 Zoom optics 4 Acquisition device 5-1 Linear or rotary axis of movement 5-2 Linear or rotary axis of movement 6 Optical axis 6l Optical axis (left beam path) 6r Optical axis (right beam path) 7 Control device 7-1 Computing device 7-2 Memory 8 Stand 9 Actuators 10 Acquired image 11 Acquired additional image 12 Stereoscopic imaging optics 12l Left beam path 12r Right beam path 12o Main objective 13 Axis of symmetry 14 Axis of symmetry 15 Display device 16 Computer monitor 17 Reflection device 18 Stereo angle 19 Angle bisector 20 Zoom center 21 Rotation 22 Reference mark 23 Additional reference mark 24 Plane of symmetry 25l Object area (left beam path) 25r Object area (right beam path) 30 Control signals 31 Control signals 40 Object 41 Reference object 42 Charucoboard 43 Line markings 51-x Feature 52-x Feature 53-x Feature 54 Intersection 55 Line 56 Line57 Straight line 61-x Feature 62-x Feature 63 Direction of displacement 64 Coordinate axis Image sensor (target orientation) 100-109 Procedure steps of the procedure F1, F2 Focus plane

Claims

Method for adjusting and / or calibrating a medical microscope (1), wherein for at least one observer beam path (2) of the medical microscope (1): images (10) of an object (40) at different magnification levels of a zoom optic (3) of the at least one observer beam path (2) are acquired by means of a detection device (4) of the at least one observer beam path (2), and a zoom center (20) is determined based on the acquired images (10), and i) further images (11) of the object (40) at different axis positions of at least one linear or rotary axis of motion (5-1,5-2) of the medical microscope (1) are acquired, and a rotation (21) of the detection device (4) relative to the at least one linear or rotary axis of motion (5-1,5-2) is determined based on the acquired further images (11).and / orii) in an eccentric imaging optic of the medical microscope (1), further images (11) of the object (40) are acquired in different focal planes and / or at different working distances, wherein a rotation (21) of the acquisition device (4) is determined based on the acquired further images (11), and wherein a reference mark (22) is determined based on the determined zoom center (20) and the determined rotation (21) and is provided for adjustment and / or calibration. Method according to claim 1, characterized in that the provision comprises displaying the reference mark (22) on at least one display device (15) of the medical microscope (1). Method according to claim 2, characterized in that the specified reference mark (22) is displayed in the form of a virtual null tube on the at least one display device (15) of the medical microscope (1). Method according to one of the preceding claims, characterized in that the detection device (4) is adjusted and / or calibrated by means of the reference mark (22). Method according to one of the preceding claims, characterized in that a reflection device (17) of the at least one observer beam path (2) is adjusted and / or calibrated starting from the determined reference mark (22). Method according to one of the preceding claims, characterized in that a reference object (41) is aligned to the specific reference mark (22), wherein components of the medical microscope (1) are adjusted and / or calibrated on the basis of the aligned reference object (41). Method according to one of the preceding claims, characterized in that the specified reference mark (22) is stored, wherein, starting from the stored reference mark (22) and at least one further reference mark determined at a later time, a state of the medical microscope (1) is monitored. Method according to one of the preceding claims, characterized in that a reference mark (22) is determined for each detection device (4) and / or each observer beam path (2) of the medical microscope (1), wherein the detection devices (4) and / or components of the observer beam paths (2) are adjusted and / or calibrated relative to each other starting from the respective determined reference marks (22). Method according to one of the preceding claims, characterized in that, to determine the zoom center (20), identical features (51-x, 52-x, 53-x) are recognized in the images (10) captured at different zoom levels and are each assigned to one another, wherein the zoom center (20) is determined on the basis of an intersection point (54) of straight lines (55, 56, 57) which result from connecting the respective corresponding features (51-x, 52-x, 53-x) in the superimposed captured images (10). Method according to one of the preceding claims, characterized in that, for determining the rotation (21), identical features (61-x, 62-x) in the captured further images (11) are recognized and each is assigned to one another, wherein, starting from the identical features (61-x, 62-x), a displacement direction (63) of the identical features (61-x, 62-x) is determined with reference to the superimposed captured further images (11), and wherein the rotation (21) is determined starting from the determined displacement direction (63). Method according to one of the preceding claims, characterized in that an optical flow in the captured images (10) is evaluated to determine the zoom center (20). Method according to one of the preceding claims, characterized in that an optical flow in the captured further images (11) is evaluated to determine the rotation (21). Method according to one of the preceding claims, characterized in that the object (40) comprises a checkerboard and / or a Charucoboard (42). Method according to one of the preceding claims, characterized in that only a partial area of ​​the captured further images (11) in the vicinity of the zoom center (20) is used to determine the rotation (21). Medical microscope (1), comprising: at least one observer beam path (2) with a zoom optic (3), a detection device (4), and at least one linear or rotary axis of motion (5-1,5-2) and / or an eccentric imaging optic (12); and a control device (7), wherein the control device (7) is configured to determine a zoom center (20) in detected images (10) which are or have been detected by an object (40) at different magnification levels of the zoom optic (3) by means of the detection device (4); i) to determine a rotation (21) of the detection device (4) relative to the at least one linear or rotary axis of motion (5-1,5-2) starting from detected further images (11) which are or have been detected by the object (40) at different axis positions of the at least one linear or rotary axis of motion (5-1,5-2) of the medical microscope (1);and / orii) in the case of an eccentric imaging optic (12) of the medical microscope (1), to determine a rotation (21) of the acquisition device (4) starting from acquired further images (11) which are or were acquired of the object (40) in different focal planes (F1,F2) and / or at different working distances, and to determine a reference mark (22) starting from the determined zoom center (22) and the determined rotation (21) and to provide it for adjustment and / or calibration.;

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