Method and control device for adjusting and / or calibrating and / or monitoring a focus value of an optical device with zoom function

Abstract

The invention relates to a method for adjusting and / or calibrating and / or monitoring a focus value of a surgical microscope (1, 40) comprising at least one objective lens (2, 3), an image capture device (5) and a zoom system (8), the surgical microscope (1, 40) being designed to operate under at least two different zoom settings. The method comprises the following steps: (21) capturing at least one respective image of the stationary object (41) in at least two different zoom settings by means of an image capturing device (5); determining (22) a plurality of contrast values based on the focus value using the at least one detected image; and (23) using the determined contrast values for the at least two zoom settings to determine at least one target value of at least one parameter for adjusting and / or calibrating a focus value of the surgical microscope (1, 40).

Description

Technical Field

[0001] The invention relates to a method for adjusting and / or calibrating the focus value of a surgical microscope, a control device for adjusting and / or calibrating the focus value of a surgical microscope, a surgical microscope, a computer-implemented method, a computer program product, a computer-readable data carrier, and a data carrier signal. Background Art

[0002] In the context of optical devices, adjustment and calibration of the focus often play an important role. Adjustment is understood to mean a one-time setting of a device, for example during maintenance or assembly, and calibration is understood to mean the adaptation of single or multiple parameters during maintenance or assembly or operation of the device. In the context of calibration, for example control curves can be stored for later application.

[0003] For adjusting and calibrating the video module, so-called optical reference devices are usually used, which can be used in analog or digital form. These optical reference devices attempt to represent both the optical center of the master observer and the focus position of the master observer by means of a strict mechanical tolerance chain (e.g. a specified positioning of the optical unit relative to the dovetail interface on which the optical reference device is mounted). The master observer has been pre-adjusted. Therefore, the master observer is used in combination with the optical reference device as a reference, in particular for the position in the image plane (xy plane), the focus position and the rotation. When adjusting the focus, it is usually intended that the focus value at which the contrast value is maximum is only slightly different or not different at all at different zoom positions. Summary of the invention

[0004] Against this background, the object of the present invention is to provide an advantageous method for adjusting and / or calibrating the focus value of a surgical microscope, an advantageous control device for calibrating the focus value of a surgical microscope, an advantageous surgical microscope, a computer-implemented method, a computer program product, a computer-readable data carrier, and a data carrier signal.

[0005] The stated object is characterized by a method for adjusting and / or calibrating the focus value of a surgical microscope as claimed in claim 1, a control device for adjusting and / or calibrating the focus value of a surgical microscope as claimed in claim 15, a surgical microscope as claimed in claim 16, a computer-implemented method as claimed in claim 18, a computer program product according to the invention, a computer-readable data carrier according to the invention, and a data carrier signal according to the invention. The dependent claims contain further advantageous configurations of the invention.

[0006] The method according to the invention for adjusting and / or calibrating and / or monitoring the focus value of a surgical microscope comprises the following steps, the surgical microscope comprising at least one objective lens, an image capture device (e.g. in the form of a camera chip), and a zoom system, wherein the optical device is designed to operate in at least two different zoom positions (i.e. zoom positions that deviate from one another): If there are at least two different zoom positions, the image capture device captures at least one image (i.e. one image representation) of a given object. Subsequently, a plurality of contrast values ​​are determined depending on the focus value with the aid of at least one captured image. At least one corresponding contrast value can be determined in a plurality of images, which were captured with correspondingly different focus values. However, a plurality of contrast values ​​can also be determined in one captured image. This is useful for images of tilted objects.

[0007] The focus value may be a relative focus value or a focus value difference. Typically, a surgical microscope outputs a focus value that depends only on the position of the optical elements of the main objective. In this case, a flat or planar calibration object positioned perpendicular to the optical axis may be used. In the case of a surgical microscope with a constant focal length, it is advantageous to use a flat calibration object that is tilted relative to the optical axis. For example, a relative focus value in the form of a focus change or focus migration that depends on the zoom setting may be determined (e.g. calculated). The terms zoom position and zoom setting are used synonymously in this specification.

[0008] The contrast value can preferably be determined by image evaluation. The image evaluation can be performed digitally and / or automatically and / or visually. Here, a specified image point or an image fragment or an image segment can be evaluated. In a further step, at least one expected value of at least one parameter for adjusting and / or calibrating the focus value of the surgical microscope is determined with the aid of the determined contrast value for at least two zoom positions. For this purpose, the focus value at which the contrast value of the corresponding zoom position is maximum can be determined. The parameter for adjusting and / or calibrating the focus value of the surgical microscope should be understood to mean a variable that can be changed when adjusting and / or calibrating the focus value, for example, the distance between at least one objective lens and the image capture device or the distance between the individual lenses or lens groups of the objective lens.

[0009] Depending on the requirements to be met, the method can be performed for all zoom positions or only for a number of selected zoom positions.

[0010] The determination of the expected value may comprise the determination of a change value of the focus of the surgical microscope, in particular the focus position independent of the zoom. The determination of the expected value, in particular the change value, may be based on an evaluation of the gradient of at least one curve, such as a straight line, which maps the dependence of the focus value or the detected focus change on a reference variable over the zoom position. The focus change may be specified, for example, relative to the position of the zoom center or another specified object-side reference point, such as an object mark on the object (calibration object). The focus change may be specified in any unit that may be defined, for example, by an element imaged onto the object.

[0011] A functional relationship (e.g., a linear correlation) between the gradient of the surgical microscope and the focus position or focus setting can be assumed or determined by appropriate measurements. Based on the functional relationship (e.g., the gradient of the corresponding straight line), the expected value and / or the change value can be calculated directly with the help of the contrast value determined for at least two different zoom positions or the obtained absolute focus value or relative focus value with the maximum contrast. For example, for a specific zoom setting, the expected value can be calculated and / or provided and / or displayed and / or monitored in the form of a target focus line or target focus area in the captured image of the specified object. This allows the technician to adjust and / or calibrate accordingly. The adjustment and / or calibration can be performed at a preset or any zoom setting.

[0012] The image capture device may be a camera, such as a video camera. The camera may include a camera chip. The surgical microscope may have a stereo optical system.

[0013] The invention has the advantage that a surgical microscope with a mechanical zoom system can set the focus independently of a main observer and an optical reference device. An optical reference device is therefore not necessary for adjusting and / or calibrating the focus. The deviation from an ideal device tuned to infinity (i.e. pre-adjusted so that the light beams in the magnification system are parallel when the object is in focus) can be quantified, for example, by the deviation of the focus value at which the contrast value is maximum. The focus setting is also independent of the main observer and therefore of the absence or subjective assessment of the observer. A further advantage is that the use of a measured calibration object can be dispensed with, since only relative focus values ​​can be used for adjustment and / or calibration.

[0014] In a preferred variant, the surgical microscope comprises at least a first objective, for example in the form of a main objective, and a second objective, for example in the form of a video objective, wherein the second objective is arranged in the beam path between the first objective and the image capture device.

[0015] In an advantageous variant, at least one correction value for the relative position of at least one objective (e.g. the second objective and / or the first objective) and / or the image capture device within the surgical microscope relative to the beam path can be determined based on at least one expected value.

[0016] At least one desired value may be determined and / or specified for each of the at least two zoom positions individually. At least one desired value may be determined and / or specified for the at least two zoom positions in such a way that for the at least two zoom positions the difference between the focus values ​​at which the contrast value is maximum is smaller than a specified threshold. This has the advantage that when changing the zoom position the focus value changes only slightly or if the difference is zero the focus value does not change.

[0017] For example, based on the determined focus value at which the contrast value of the corresponding zoom setting is maximum, at least one expected value of at least one parameter for adjusting and / or calibrating the focus value of the surgical microscope can be determined and / or specified. As part of the adjustment, for example, the second objective lens (i.e. the video objective lens) is preferably shifted so that a corresponding expected value for positioning and / or shifting can be determined and / or specified. At least one expected value for each of the at least two zoom positions can be determined and / or specified in one of the two zoom positions or in the other zoom position. If the inspection reveals that the surgical microscope is correctly adjusted, the expected value will be equal to the actual value or within a tolerance range. This also enables monitoring or remote monitoring of the surgical microscope.

[0018] In an advantageous variant, at least one image of a planar surface of a given object can be captured, wherein the planar surface has a surface normal which encloses an angle between 0 and 90 degrees, in particular between 5 and 85 degrees, for example 20 degrees, with the optical axis of the objective. In other words, in the above example, the planar surface encloses an angle between 90 and 0 degrees, in particular between 85 and 5 degrees, for example 70 degrees, with the optical axis of the objective. Using a planar surface has the advantage that the distance of the object point from the objective is easy to determine and image evaluation is therefore simplified.

[0019] Preferably, the object used is a known calibration object. The calibration object may have a specified pattern, such as a chessboard pattern. Thus, advantageously, in each case at least one image of a specified calibration object is captured at at least two different zoom positions, the image having known features such that high contrast areas are identifiable in the image representation. If the geometry of the calibration object is known, high contrast areas in the image can be predicted. These high contrast areas can be determined and evaluated based on the contrast. This reduces the calculation time. For example, the calibration object may be a ChArUco plate. The stated variant simplifies the determination of contrast values ​​and provides a robust solution to errors due to possible noise. For example, only contrast values ​​within a specified area in the center of the image can be determined and / or evaluated. This simplifies and speeds up adjustment and / or calibration.

[0020] Advantageously, the size of the pattern, in particular the size of the pattern elements, is known or preset, or the size is determined. The size may be known or preset or determined in length units, for example in millimeters. Preferably, the imaging scale (for example in the form of a relationship between the corresponding size of at least one element of the calibration object, for example in millimeters, and the length unit of the camera chip, for example in pixels) is known or preset or determined. If the tilt of the calibration object is known or preset or set or determined in a defined manner, the focus value can be determined (in particular calculated) using the size and / or the imaging scale relative to a point in the image representation, for example relative to the zoom center at which the contrast value is maximum. For example, the tilt of the calibration object can be determined using a pose estimation. In addition, the geometric deformation that occurs in the case of tilt in the captured image representation of the calibration object (for example, the resulting trapezoid) can be evaluated with the aid of the camera to determine the tilt. The described configuration has the advantage that the focus value at which the contrast value is maximum and the correlation between the contrast value and the focus value can be easily and quickly reliably determined.

[0021] At each of the at least two zoom positions, an image of a specified object can be captured at a plurality of focus values. The focus value can be adjusted by means of a settable focusing system. Compared to the above-described variant, in which different focus values ​​are achieved by means of an inclined arrangement of the calibration object in the image representation, the normal of the plane surface of the calibration object can enclose an angle of 0° with the optical axis. For this purpose, the surgical microscope must be equipped with an objective lens with a variable focal length. By means of a corresponding focusing that can be automated, a value table and / or a curve can be determined for each of the at least two zoom positions, which maps the relationship between contrast values ​​and focus values. The contrast value curve can be used to adapt the focus value of the surgical microscope. Alternatively, the calibration object can be moved along the optical axis.

[0022] In an advantageous variant, the focus value of the surgical microscope for each of the at least two zoom positions is adjusted and / or calibrated separately, i.e., individually for each zoom position, such that the contrast value for each of the at least two zoom positions is maximal. Thus, in other words, when changing the zoom position, the focus value is readjusted or reset, for example with the aid of the stored data, and the stored data is then used permanently during operation to set or correct the focus value accordingly. Additionally or alternatively, in another advantageous variant, the focus value of the surgical microscope for at least two zoom positions can be adjusted and / or calibrated such that for at least two zoom positions the difference between the focus values ​​at which the contrast value is maximal is below a specified threshold.

[0023] The focus value of the surgical microscope can be adjusted and / or calibrated in several ways. For example, the focus value of the surgical microscope can be adjusted and / or calibrated by adapting the distance between the object plane (e.g., a given object) and at least one objective (e.g., a first objective (e.g., a main objective) and / or a second objective (e.g., a video objective). Thus, in this variant, the focal length is adapted by displacing at least one objective and / or the object relative to each other along the optical axis of the at least one objective.

[0024] In addition to or as an alternative to the first variant described above, the focus value of the surgical microscope can be adjusted and / or calibrated by adapting the distance between the objective lens (e.g., the first objective lens and / or the second objective lens) and the image plane of the image capture device. Thus, in this variant, at least one objective lens and the image capture device are moved relative to each other in the direction of the optical axis of the objective lens or along the optical axis of the objective lens, wherein the objective lens and / or the image capture device can be moved.

[0025] At least one objective lens (i.e., for example, the first objective lens and / or the second objective lens) may include a first optical element and a second optical element. In addition to the above two variants or as an alternative thereto, the focus value of the surgical microscope can be adjusted and / or calibrated by displacing the first optical element of the objective lens relative to the second optical element of the objective lens. An optical element is understood to refer to a plurality of optical components that are fixedly positioned relative to each other. For example, an optical element may include only one lens or a plurality of lenses. Thus, in this variant, internal focusing occurs in the corresponding objective lens, for example, in the main objective lens or the video objective lens. In particular, the optical device may include a first objective lens (e.g., the main objective lens) and a second objective lens (e.g., the video objective lens), wherein the first objective lens is arranged between the object plane and the second objective lens in the beam path. For example, the focus value of the surgical microscope can be adjusted and / or calibrated by displacing the first optical element of the first objective lens relative to the second optical element of the first objective lens and / or by displacing the first optical element of the second objective lens relative to the second optical element of the second objective lens.

[0026] Advantageously, the zoom position and / or focus value is set automatically. This simplifies adjustment and / or calibration and reduces the time required for adjustment and / or calibration.

[0027] The surgical microscope may comprise a stereoscopic optical system, wherein the stereoscopic optical system has or defines a first optical path and at least one further optical path. At least one desired value and / or calibration data of the first optical path may be determined and transferred to at least one further optical path. An optical path is understood to mean the path of light from an object through the optical system to an image plane. The described variant has the advantage that only one of the multiple optical paths has to be adjusted and / or calibrated, and the result of this process is immediately available for at least one further optical path, so that the at least one further optical path does not have to be adjusted and / or calibrated separately. This reduces the time required for adjusting and / or calibrating the stereoscopic optical system.

[0028] The control device according to the invention for adjusting and / or calibrating and / or monitoring the focus value of a surgical microscope comprising at least one objective, an image capture device and a zoom system is designed to carry out the previously described method according to the invention. The control device has the features and advantages already described above.

[0029] The surgical microscope according to the invention comprises at least one objective lens, an image capture device (e.g. a camera, in particular a video camera), and a zoom system. The surgical microscope is designed to operate in at least two different zoom positions. The surgical microscope is also designed to perform the method according to the invention described above. The surgical microscope may comprise the control device according to the invention described above. The surgical microscope according to the invention has the features and advantages already described. The surgical microscope preferably has a stereoscopic optical system.

[0030] The computer-implemented method according to the present invention comprises instructions, which, when a computer executes the program, cause the computer to execute the method according to the present invention described above. The computer program product according to the present invention comprises instructions, which, when a computer executes the program, cause the computer to execute the method according to the present invention described above. The computer program product according to the present invention is stored on a computer-readable data carrier according to the present invention. The data carrier signal according to the present invention transmits the computer program product according to the present invention. The computer-implemented method according to the present invention, the computer program product according to the present invention, the computer-readable data carrier according to the present invention, and the data carrier signal according to the present invention have the above-mentioned features and advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention is explained in more detail below with reference to the accompanying drawings based on exemplary embodiments. Although the present invention has been more specifically described and illustrated with the aid of preferred exemplary embodiments, the present invention is not limited to the disclosed examples, and other variants can be derived from the present invention by those skilled in the art without departing from the scope of protection of the present invention.

[0032] These figures are not necessarily accurate and drawn to scale in every detail, and may be presented in an exaggerated or reduced form for the sake of clarity. Therefore, the functional details disclosed herein should not be understood as limiting, but merely as an illustrative basis to provide guidance for those skilled in the art to use the present invention in various ways.

[0033] When used in a series of two or more elements, the expression "and / or" herein means that any of the listed elements may be used alone, or any combination of two or more of the listed elements may be used. For example, if a structure is described as including components A, B, and / or C, the structure may include: A alone; B alone; C alone; A and B together; A and C together; B and C together; or A, B, and C together.

[0034] Figure 1 The beam paths through the surgical microscope are schematically shown for two zoom positions.

[0035] Figure 2 The method according to the invention is schematically shown in the form of a flow chart.

[0036] Figure 3 The contrast value curves are schematically shown as a function of the focus value for two zoom positions.

[0037] Figure 4 The relationship between the contrast value curve and the focus value for four zoom positions is schematically shown.

[0038] Figure 5 A surgical microscope to be calibrated and a calibration object are schematically shown.

[0039] Figure 6 Two images of a calibration object captured at different zoom positions are schematically shown.

[0040] Figure 7 The focus value change versus zoom position for three different adjustment or calibration states is schematically shown in the form of a diagram.

[0041] Figure 8 The display of contrast lines (actual focus lines) and desired focus lines in a captured image of a calibration object is schematically shown.

[0042] Fig. 9 A first variant of a surgical microscope according to the invention with a control device according to the invention is shown schematically.

[0043] Fig.10A second variant of the surgical microscope according to the invention is shown schematically with a control device according to the invention. DETAILED DESCRIPTION

[0044] The following references Figure 1 The background of the present invention is explained in more detail. Figure 1 The beam path 10 through the surgical microscope 1 is schematically shown in two zoom positions. Figure 1 In the upper part of the image, a first zoom position with a low zoom value is set, and in the Figure 1 In the lower part of the embodiment, a second zoom position with a high zoom value is set. Therefore, the zoom value of the beam path shown in the upper part is smaller than the zoom value of the beam path shown in the lower part.

[0045] The surgical microscope 1 comprises a first objective 3 in the form of a main objective and a second objective 2 in the form of a video objective, each of which comprises at least one lens or lens group. The second objective 2 is arranged in the beam path between the first objective 3 and the image capture device 5. In each case, Figure 1 On the left side, the beam path 10 is shown upstream of the surgical microscope 1 and on the right side, downstream of the surgical microscope 1. Thus, Figure 1 The beam directions in FIG. extend from left to right. Starting from the object plane 4, the object point is imaged onto the image plane of the image capture device 5, for example onto a camera chip. In the example shown, the first beam 11 and the second beam 12 each image an object point onto the camera chip 5. The beams 11 and 12 first pass through the first objective 3. The beam paths downstream of the first objective 3 and upstream of the second objective 2 are in each case afocal. The region in which the afocal radiation beams occur is denoted by reference numeral 6 in each case. Therefore, parallel beam paths exist in the region 6.

[0046] When adjusting and / or calibrating the surgical microscope 1, the Figure 1 In the horizontal direction of the video objective 2, at least one lens, a group of lenses or a camera chip 5 is moved. If the video objective 2 is correctly focused (e.g. Figure 1 ), the beams forming the axial beam (ie the second beam 12 in the present case) each converge at a point on the camera chip 5 independently of the zoom position (and therefore not in front of or behind the camera chip 5).

[0047] The following uses Figures 2 to 6An example of a method for adjusting and / or calibrating the focus value of a surgical microscope according to the invention is described in more detail. The surgical microscope comprises at least one objective (e.g. a first objective 3 in the form of a main objective and a second objective 2 in the form of a video objective), an image capture device 5 and a zoom system, and is designed to operate in at least two different zoom positions. The video objective 2 is arranged between the main objective 3 and the image capture device 5 in the beam path 10.

[0048] Figure 2 The method according to the invention is schematically illustrated in the form of a flow chart. In a first step 21, at least one image or image representation of a specified object, preferably a known calibration object, is captured by means of an image capture device 5 in each case at at least two different zoom positions. In a second step 22, one or more contrast values ​​are determined depending on the focus value with the aid of at least one captured image. This is preferably done with the aid of suitable image evaluation software, which is configured, for example, to quantify black-and-white transitions of the image with regard to contrast. In a third step 23, at least one desired value and optionally a correction value of at least one parameter for adjusting and / or calibrating the focus value of the surgical microscope is determined with the aid of the contrast values ​​determined for at least two zoom positions. In this context, the focus value at which the contrast value for the respective zoom position is maximum can be determined. The following uses Figures 6 to 8 An example of implementation of step 23 is explained in more detail.

[0049] The determined focus value at which the contrast value of the corresponding zoom position is maximum can be used in an optional step 24 to adjust and / or calibrate the surgical microscope, for example by adjusting and / or calibrating the surgical microscope in such a way that the focus position (in particular the focus position of the video objective 2) is adapted so that the maximum of the contrast curve (i.e. the maximum of at least two contrast curves) occurs at the same focus value or at a focus difference that is less than a specified threshold. Once the desired focus difference is reached, the surgical microscope (in particular the video objective) is correctly adjusted and / or calibrated in focus. In the case of a focus difference of zero, the surgical microscope (in particular the objective) is tuned to infinity.

[0050] Alternatively or additionally, in step 24, the determined focus value (at which the contrast value of the corresponding zoom position is maximum) can be stored for controlling the surgical microscope and used when adjusting and / or calibrating the focus value using the various zoom positions. For example, after the surgical microscope is installed and adjusted, the contrast value curves for the various zoom positions can be recorded and stored in the device. If the zoom setting is changed, the new actuation value of the focusing system can therefore be determined and set according to the stored curve. This ensures a clear image. Therefore, only a rough adjustment is required, or in some cases, the adjustment may be redundant. This digital calibration can be done in the main objective, in the video objective or by shifting the camera chip. Therefore, it is no longer necessary to perfectly adapt the magnification system to infinity. However, other image errors may occur, which can be corrected digitally.

[0051] Figure 3 The contrast value curves are schematically shown as a function of the focus value for two zoom positions. Figure 4 The contrast value curves for four zoom positions are schematically shown as a function of the focus value. On the x-axis, the focus value f is plotted in each case in millimeters, and on the y-axis, the contrast value normalized to unity is plotted. Figure 3 , the contrast value curve 31 has been determined at a zoom position with a zoom value of 1.0 and has a maximum at a focus value of 211.6 mm. The contrast value curve 32 has been determined at a zoom position with a zoom value of 2.4 and has a maximum at a focus value of 211.4 mm. Here, the focus values ​​with maximum contrast are relatively close together, so that further adjustment and / or calibration can be omitted if appropriate. Figure 4 In FIG. 3 , a contrast value curve 33 at a zoom position with a zoom value of 1.0, a contrast value curve 34 at a zoom position with a zoom value of 1.5, a contrast value curve 35 at a zoom position with a zoom value of 2.0, and a contrast value curve 36 at a zoom position with a zoom value of 2.4 have been determined. Here, the focus values ​​with the maximum contrast are relatively far apart, so that the contrast value curves can be used to adjust and / or calibrate the surgical microscope.

[0052] There are various options for carrying out step 22, ie for determining a plurality of contrast values ​​depending on the focus value by means of the captured image. If the surgical microscope has a focusing system, ie the focus value can be set automatically, the image can be captured automatically. Figure 3 and Figure 4 The focusing can thus be automatic and corresponding images of the calibration object can be captured for each focus value and evaluated in terms of contrast. If an automatic zoom system is also available, the individual zoom settings can also be set automatically.

[0053] If the focus value is not automatically settable, the focus difference (which results from the two zoom positions with an obliquely positioned target as object) can be read visually or preferably determined by image evaluation as already described above. The focus value difference leads to the necessary setting of the focus position of the optical device, in particular the video objective. Figure 5 and Figure 6 to explain this variation.

[0054] Figure 5 Schematically shown are a surgical microscope 40 to be adjusted and / or calibrated and a calibration object 41. Calibration object 41 may be fixedly connectable or connected to surgical microscope 40.

[0055] A calibration object 41, which preferably has a planar surface 42 with a known pattern, preferably a ChArUco pattern, is arranged tilted relative to the optical axis 7. In this case, a surface normal 43 of the surface 42 of the calibration object 41 may enclose an angle 44 between 5 and 85 degrees, for example 20 degrees, with the optical axis 7. This corresponds to an angle 45 between 85 and 5 degrees, for example 70 degrees, between the surface 42 and the optical axis 7. For the tilted calibration object 41, contrast values ​​may be calculated for a plurality of focus values ​​in the image.

[0056] Advantageously, the dimensions of the pattern, in particular the dimensions of the pattern elements, are known or preset or the dimensions are determined. The dimensions may be known or preset or determined in length units, for example millimeters. Preferably, the imaging scale, for example in the form of a relationship between the corresponding dimensions of at least one element of the pattern in pixels and the length unit, is known or preset or determined. If the inclination of the calibration object 41 is known or preset or set in a defined manner or determined, for example, by means of a posture estimation, the focus value at which the contrast value is maximum can be determined (in particular calculated) by means of the dimensions and / or the imaging scale. This configuration has the advantage that the focus value at which the contrast value is maximum and the correlation between the contrast value and the focus value can be reliably determined easily and quickly.

[0057] The variant with the tilted calibration object 41 also offers the advantage that an optical system (in particular a surgical microscope) with a fixed focal length can also be adjusted and / or calibrated. For this purpose, the contrast value curves for at least two zoom positions are first determined, and then the desired focus position for at least one zoom position can be calculated and / or provided and / or displayed, so that the technician can use the displayed desired focus position to adjust and / or calibrate the optical system (see, for example, below). Figure 8 ).

[0058] Figure 6Two images 18 of a calibration object 41 captured at different zoom positions are schematically shown. There is a zoom center and it is preferably placed in a point in the center of the image. If the zoom center is not in the center of the image, it is useful to place the coordinate origin of the object-side coordinate system used in the object point of the zoom center (the projection of the zoom center onto the object). In particular, the zoom center is a point that does not move between the various magnification levels in the captured image representation. In particular, the zoom center can be regarded as the optical center of the observer's beam path. Camera systems are typically designed and / or adjusted so that the object point imaged onto the center of the camera chip does not move in the image representation during zooming. In this case, the optical axis defined by the zoom system will intersect the center of the camera chip. The calibration object 41 is tilted so that Figure 6 The focus value in varies from left to right. The image shown on the left is captured at a first zoom position, and the image shown on the right is captured at a second zoom position. Contrast lines (i.e., vertical lines with the highest contrast in the images shown) are denoted by reference numeral 46. Figure 6 Compared with the contrast line 46 at the first zoom position shown on the left side of FIG. 1 , the contrast line 46 at the second zoom position (i.e., at Figure 6 In the depiction shown on the right side of FIG. 4 , the contrast line 46 is located further to the right of the calibration object 41 in the image relative to the object mark 17 on the calibration object 41. In other words, the contrast line 46 is located at Figure 6 In the depiction shown on the left side of FIG. 1 , there are about three checkerboard patterns (white squares or black squares) on the left side of the object mark 17, and Figure 6 The depiction shown on the right has approximately two checkerboard patterns to the left of the object marking 17. Therefore, the contrast lines 46 are shifted relative to the calibration object 41 or the object marking 17. This means that the focal plane moves (or in other words migrates) along the optical axis 7 when switching between two zoom positions. If the contrast lines 46 were always at the same position on the object, the focus value difference would be zero. The object marking 17 can be placed anywhere on the object. The relative change or migration of the contrast lines 46 will remain the same. However, it is preferred to choose an object point that coincides with the zoom center and therefore with the optical axis of the zoom system.

[0059] The contrast line 46 is located at the calibration object 41 from the first zoom position (see Figure 6 ) to the second zoom position (see Figure 6The conversion of a horizontal displacement of the contrast line 46 (depicted on the right side of FIG. 4 ) into a vertical difference (i.e. a difference in the direction of the optical axis 7 ) corresponds to a focus value difference. This focus value difference can be calculated from the displacement of the contrast line 46, the geometry of the experimental arrangement and the scale (e.g. the size of the ChArUco markings of the pattern on the plane surface 42 of the calibration object 41 ). Typically, the focal plane is a sphere, so that the contrast line 46 shown represents an approximation of a contrast curve. If the curvature of the contrast curve (i.e. the deviation of the contrast line 46 (straight line) shown from the actual contrast curve) is small, then the approximation to a line is reasonable. Otherwise, the actual contrast curve must be taken into account.

[0060] In all variants, it is advantageous to use a known calibration object, such as a chessboard or a ChArUco board. This simplifies the detection and evaluation of the contrast.

[0061] Figure 6 The change in contrast lines shown in indicates a shift or change in focus value depending on the zoom position. Figure 7 The zoom position Z is plotted on the x-axis and the focus value F is plotted on the y-axis. The focus value may be specified in millimeters or in pixels or in any unit that characterizes the migration of the focus relative to the calibration object 41 (e.g., relative to the migration of the object marking 17 on the calibration object 41). The size of the geometric shape or structure imaged on the calibration object 41 may be used as a scale. For example, in Figure 6 In the example shown, the width of one of the imaged rectangles can be used as a scale. Since the procedure according to the invention explained in detail below requires only relative focus values, i.e. deviations of the determined focus values ​​from a reference point or from each other, the invention has the advantage that the adjustment and / or calibration can be performed with any calibration object 41. Thus, no measured calibration object is required.

[0062] Figure 7 The results of three measurements are shown. For example, for zoom position Z 1 and zoom position Z 2 A focus value F is determined. The focus value F is preferably determined for more than two zoom positions Z. A function of the focus value can be determined from the measured values ​​F=f(Z) depending on the zoom position. This can preferably be assumed to be a straight line with a gradient g(F~g*Z). The migration of the focus value relative to the calibration object is represented by the gradient g. The absolute value of the gradient g should be minimized in the adjustment and / or calibration and preferably approach zero or be set to approach zero. In other words, due to the adjustment and / or calibration, the straight line should preferably extend parallel to the x-axis.

[0063] exist Figure 7 In the first measurement, it is determined that the zoom value Z 1 The focus value F is determined at1 and at zoom value Z 2 The focal value F 2 and has a gradient g=(F 2 –F 1 ) / (Z 2 –Z 1 ). The focus value of the surgical microscope is then increased or decreased by ΔF and a second measurement is performed in the same manner as the first measurement. The increase or decrease can be done at any zoom position. Here, a straight line 26 is determined with a lower gradient than the straight line 25. The focus value of the surgical microscope is then further increased or decreased and a third measurement is performed in the same manner as the first two measurements. In this case, a straight line 27 with a negative gradient is determined.

[0064] Based on the correlation thus determined between the change in focus value ΔF of the surgical microscope and the gradient g (g=f(ΔF)), the focus value of the surgical microscope can be adjusted or calibrated in such a way that a gradient g of zero (or close to zero, taking into account a predetermined tolerance) is obtained. It has been found that there is generally a linear correlation that is independent of the zoom (g≈m*(ΔF), where m indicates an increase), so that two measurements (e.g. a first measurement with a tilted calibration object at a first zoom position and a second measurement with a tilted calibration object at a second zoom position) are in principle sufficient to determine a desired value or target value for adjustment and / or calibration, in particular the value by which the current focus value of the surgical microscope must be increased or decreased in order to change the absolute value of the gradient g as desired. Thus, on the one hand, as described, in the context of the method according to the invention, the correlation between the change in focus value ΔF of the surgical microscope and the gradient g can be determined or assumed to be known. In the latter case, the surgical microscope can be adjusted and / or calibrated based on the determination of only one gradient. The required change in the focus value can be specified, for example, in millimeters.

[0065] In conjunction with the adjustment and / or calibration, the determined desired or target value can be displayed to a technician, for example in the form of a tolerance bar, tolerance band, line or curve extending parallel to the determined contrast curve or contrast line 46 . Figure 8 This is schematically illustrated. In the example shown, the calibration object 41 is tilted in such a way that the focus changes from top to bottom. Figure 8 In the captured image 18 of the calibration object 41 , the desired line is denoted by reference numeral 29 , and the line having the current highest contrast (ie, the current contrast line) is denoted by reference numeral 28 .

[0066] There are various options for adjusting and / or calibrating the focus values ​​of the surgical microscope 1 for individual or all zoom positions, which options can be applied individually or in combination with each other. A first variant is to change the focal length, i.e. the distance between the object or object plane 4 and at least one of the objectives 2, 3. In the case of a surgical microscope 1 comprising a main objective 3 and a video objective 2, in this case the main objective 3 can be moved relative to the object or object plane 4. A second variant is to change the distance between the objective 2 of the surgical microscope 1 and the image plane 5. In this case, the image capture device 5 (i.e., for example a camera or a camera chip) or the second objective 2 can be moved, i.e. displaced relative to each other.

[0067] A third variant consists in using an objective 2, 3 which allows internal focusing, which therefore comprises at least one first optical element and at least one second optical element, wherein the first optical element and the second optical element are displaceable relative to each other. This means that at least one of these optical elements can be displaced, while the other optical element is fixed. In the case of an operating microscope, the main objective 3 can be designed as an objective with a variable focal length. Additionally or alternatively, the video objective 2 can allow appropriate internal focusing.

[0068] Fig. 9 A first variant of a surgical microscope 40 according to the invention is schematically shown. The surgical microscope 40 comprises a control device 13 according to the invention, which is designed to carry out the method according to the invention, for example as described above with reference to Figures 2 to 8 Variant of the method described. The surgical microscope 40 shown comprises a first objective 2 (e.g. in the form of a video objective 2), a second objective 3 (e.g. in the form of a main objective 3), a zoom system 8 for changing the zoom position, and an image capture device 5 (e.g. a camera 5). The first objective 2 and / or the second objective 3 can be designed as an objective with a variable focal length and therefore each comprises at least two lenses or lens groups that are displaceable relative to each other.

[0069] The first objective 3, the zoom system 8, the second objective 2 and the image capture device 5 are optically connected to one another in the order mentioned, i.e. arranged successively in the beam path 10. A control device 13 is connected to the above-mentioned components 2, 3, 5 and 8 for signal transmission 15 and in particular controls the zoom system 8.

[0070] Fig.10 A second variant of the surgical microscope 40 according to the invention is schematically shown in a three-dimensional configuration. Fig. 9Compared to the variants shown in , in each case there are two video objectives 2 and an image capture device 5 (in particular a camera chip) arranged parallel to each other in a beam path 10. The zoom system 8 can have its own optical elements for the respective beam paths, i.e. the first optical path and the second optical path (separate beam paths or optical paths). An identical and synchronous displacement of the lenses can be achieved by mechanical, electronic or electromechanical coupling. In the context of the method according to the invention, at least one desired value and / or calibration data for the first optical path can be determined and transferred to the second optical path.

[0071] If there is a calibration of the stereo system (e.g. in the form of a camera matrix and / or distortion coefficients), the topography can be created during the operation. The plane or sphere of the topography will have the highest contrast and will intersect the topography. This contrast evaluation can be performed in one camera image and / or in both camera images. The point with the highest contrast in the image representation can be shown with a free curve in the camera image. If the focus value of the surgical microscope is set correctly, this free curve will migrate with the object in the camera image when the zoom setting is changed. The free curve can then be plotted according to the zoom ( Figure 7 This focus shift is calculated using the gradient of the straight line in the image (the gradient of the straight line in the image). If this is not the case, or if the relative shift at the topography is too large, a service technician can be informed for readjustment purposes and / or the user can be informed. Alternatively, the user can be requested to perform this monitoring regularly. Thus, this method also enables on-the-spot monitoring of the focus values.

[0072] Reference numerals list:

[0073] 1. Surgical microscope

[0074] 2 Second objective lens, video objective lens

[0075] 3 First objective lens, main objective lens

[0076] 4 Object plane

[0077] 5 Image capture device, camera chip, image plane

[0078] 6 Afocal beam

[0079] 7 Optical Axis

[0080] 8 Zoom system

[0081] 10 Beam Path

[0082] 11 The First Beam

[0083] 12 Second Beam

[0084] 13 Control Devices

[0085] 15 Signal Transmission

[0086] 17 Object Labeling

[0087] 18 Captured image of the surface of the calibration object

[0088] 21 Capturing at least one corresponding image of a specified object having at least two different zoom positions

[0089] 22 Determining one or more contrast values ​​depending on the focus value by means of at least one captured image

[0090] 23 using the determined contrast values ​​for at least two zoom positions to determine at least one desired value of at least one parameter for adjusting and / or calibrating the focus value

[0091] 24 Adjust and / or calibrate the surgical microscope

[0092] 25 First measurement

[0093] 26 Second measurement

[0094] 27 Third Measurement

[0095] 28 Actual focal line

[0096] 29 Target focal line

[0097] 31 Contrast value curve

[0098] 32 Contrast value curve

[0099] 33 Contrast value curve

[0100] 34 Contrast value curve

[0101] 35 Contrast value curve

[0102] 36 Contrast value curve

[0103] 40. Surgical Microscope

[0104] 41 Calibration Objects

[0105] 42 Plane Surface

[0106] 43 Surface Normal

[0107] 44 Angle

[0108] 45 Angle

[0109] 46 Contrast Lines

[0110] f Focus

Claims

1. A method for adjusting and / or calibrating and / or monitoring the focus value of a surgical microscope (1, 40), the surgical microscope comprising at least one objective lens (2, 3), an image capture device (5), and a zoom system (8), wherein: The surgical microscope (1, 40) is designed to operate in at least two different zoom positions. It is characterized in that The method comprises the following steps: (21) capturing at least one image of a given object (41) by means of the image capture device (5) in at least two different zoom positions, (22) determining a plurality of contrast values ​​depending on the focus value with the aid of at least one captured image, (23) determining at least one desired value of at least one parameter for adjusting and / or calibrating a focus value of the surgical microscope (1, 40) with the aid of the determined contrast values ​​for the at least two zoom positions.

2. The method according to claim 1, It is characterized in that At least one correction value for the relative position of the at least one objective (2, 3) and / or the image capture device (5) within the surgical microscope (1, 40) with respect to the beam path is determined based on the at least one expected value.

3. The method according to claim 1 or 2, It is characterized in that The at least one expected value for each of the at least two zoom positions is determined and / or specified separately, and / or the at least one expected value for the at least two zoom positions is determined and / or specified in such a way that for the at least two zoom positions, the difference between the focus values ​​when the contrast value is maximum is less than a specified threshold value (24).

4. The method according to any one of claims 1 to 3, It is characterized in that As part of capturing (21) at least one image of a specified object, at least one image (18) of a planar surface (42) of the specified object (41) is captured, wherein the planar surface (42) has a surface normal (43) that encloses an angle (44) between 5 degrees and 85 degrees with the optical axis (7) of the objective lens (2, 3).

5. The method according to any one of claims 1 to 4, It is characterized in that For each of the at least two zoom positions, an image (18) of the designated object (41) is captured at a plurality of focus values.

6. The method according to claim 5, It is characterized in that These focus values ​​are set using a programmable focus system.

7. The method according to any one of claims 1 to 6, It is characterized in that The focus value of the surgical microscope (1, 40) for each of the at least two zoom positions is separately adjusted and / or calibrated (24) so ​​that the contrast value for each of the at least two zoom positions is maximized, and / or The focus values ​​of the surgical microscope (1, 40) for the at least two zoom positions are adjusted and / or calibrated (24) so ​​that for the at least two zoom positions the difference between the focus values ​​at which the contrast value is maximum is less than a specified threshold.

8. The method according to any one of claims 1 to 7, It is characterized in that The focus value of the surgical microscope (1, 40) is adjusted and / or calibrated by: Adjusting the distance between the object plane (4) and the objective lens (2, 3) and / or Adapting the distance between the objective lens (2, 3) and the image plane of the image capture device (5) and / or By displacing a first optical element of the at least one objective (2, 3) relative to a second optical element of the at least one objective (2, 3).

9. The method according to any one of claims 1 to 8, It is characterized in that These zoom positions and / or focus values ​​are set automatically.

10. The method according to any one of claims 1 to 9, It is characterized in that At the at least two different zoom positions, at least one image of a specified calibration object with known features is captured in each case, so that high contrast areas can be identified in the image representation and / or only contrast values ​​in a specified area in the center of the image are determined and / or evaluated.

11. The method according to any one of claims 1 to 10, It is characterized in that The surgical microscope has a stereo optical system, wherein the stereo optical system has a first optical path and at least one further optical path, and at least one desired value and / or calibration data of the first optical path is determined and transferred to the at least one further optical path.

12. The method according to any one of claims 1 to 11, It is characterized in that The focus value (22) is a relative focus value or a focus value difference.

13. The method according to any one of claims 1 to 12, It is characterized in that Determination of the expected value comprises determination of a change value of the focus of the surgical microscope, wherein determination of the expected value and / or the change value is based on an evaluation of a gradient of at least one curve mapping a dependency of the focus value or a captured focus change relative to a reference variable according to the zoom position, wherein a functional relationship between the gradient and the focus setting of the surgical microscope is used.

14. The method according to any one of claims 1 to 13, It is characterized in that The expected value is calculated and / or provided in the form of a target focus line or a target focus area in the captured image of the specified object.

15. A control device (13) for adjusting and / or calibrating and / or monitoring the focus value of a surgical microscope (1, 40), the surgical microscope comprising at least one objective lens (2, 3), an image capture device (5) and a zoom system (8), wherein: The surgical microscope (1, 40) is designed to operate in at least two different zoom positions. It is characterized in that The control device (13) is designed to carry out the method according to any one of claims 1 to 14.

16. A surgical microscope (1, 40), comprising at least one objective lens (2, 3), an image capture device (5), and a zoom system (8), wherein: The surgical microscope (1, 40) is designed to operate in at least two different zoom positions. It is characterized in that The surgical microscope (1, 40) is designed to carry out the method according to any one of claims 1 to 14, or the surgical microscope (1, 40) comprises a control device (13) according to claim 15.

17. The surgical microscope (1, 40) according to claim 16, It is characterized in that The surgical microscope (1, 40) has a stereoscopic optical system.

18. A computer-implemented method comprising instructions which, when the program is executed by a computer, cause the computer to perform the method as claimed in any one of claims 1 to 14.

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