Method and control apparatus for adjusting and / or calibrating and / or monitoring the focal value of an optical instrument with a zoom function.

Abstract

The present invention relates to a method for adjusting and / or calibrating and / or monitoring the 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 be operated in at least two different zoom positions. The method comprises the steps of: capturing (21) at least one respective image of a fixed object (41) by means of the image capture device (5) at at least two different zoom settings; determining (22) a plurality of contrast values ​​based on the focus value using the at least one detected image; and determining (23) at least one target value of at least one parameter for adjusting and / or calibrating the focus value of the surgical microscope (1, 40) using the determined contrast values ​​for the at least two zoom settings.

Description

[Technical Field]

[0001] The present invention relates to a method for adjusting and / or calibrating a focus value of a surgical microscope, a control device for adjusting and / or calibrating a 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] For optical instruments, focus adjustment and calibration usually play an important role. Adjustment shall be understood to mean, for example, a one-time setting of the instrument during inspection, repair or assembly, and calibration shall be understood to mean the adaptation of one or more parameters during repair, inspection, assembly or operation of the instrument. For calibration, a control curve can for example be saved, which is applied later.

[0003] For the adjustment and calibration of video modules, so-called optical reference instruments are usually used, which can be used in both analog and digital forms. These optical reference instruments intend to represent both the optical center of the main observation unit and the focal position of the main observation unit by means of a strict mechanical tolerance chain, for example the specified positioning of the optical unit relative to a dovetail interface to which the optical reference instrument is attached. The main observation unit has already been pre-adjusted. The main observation unit is therefore used together with the optical reference instrument as a reference, in particular with regard to the position in the image plane (x-y plane), the focal position, and the rotation. When adjusting the focus, it is intended that the focus value at which the contrast value becomes maximum differs only slightly or not at all at different zoom positions. [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In view of this background, the object of the present invention is to provide an advantageous method for adjusting and / or calibrating the focal value of a surgical microscope, an advantageous control device for calibrating the focal value of a surgical microscope, an advantageous surgical microscope, a computer implementation method, a computer program product, a computer-readable data carrier, and a data carrier signal. [Means for solving the problem]

[0005] The objects described above are characterized by the method for adjusting and / or calibrating the focal value of a surgical microscope as described in claim 1, the control device for adjusting and / or calibrating the focal value of a surgical microscope as described in claim 15, the surgical microscope as described in claim 16, the computer implementation method as described in claim 18, 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. Dependent claims include yet another advantageous configuration of the present invention.

[0006] A surgical microscope comprising at least one objective lens, an imaging device in the form of, for example, a camera chip, and a zoom system, wherein the optical device is designed to operate at at least two different zoom positions, i.e., mutually offset zoom positions, a method according to the present invention for adjusting and / or calibrating and / or monitoring the focal value of a surgical microscope, comprising the following steps: If there are at least two different zoom positions, at least one image, i.e., one image representation, of a given object is taken by the imaging device. Thereafter, from at least one taken image, a plurality of contrast values ​​are identified depending on the focal value. Each of at least one contrast value can be identified in a plurality of images taken at different focal values. However, a plurality of contrast values ​​can also be identified in a single taken image. This is possible for images of tilted objects.

[0007] The focal value can be a relative focal value or a focal value difference. Typically, a surgical microscope outputs a focal value that depends solely on the position of the optical elements of the primary objective lens. In this case, a flat or planar calibration object positioned perpendicular to the optical axis can be used. For surgical microscopes with a constant focal length, the use of a flat calibration object tilted relative to the optical axis is advantageous. For example, a relative focal value can be identified, e.g., calculated, in the form of a change in focus or a shift in focus depending on the zoom setting. The terms zoom position and zoom setting are used synonymously herein.

[0008] The contrast value can preferably be determined by image evaluation. Image evaluation can be performed digitally and / or automatically and / or visually. Here, a specified image point or image segment or image section can be evaluated. In another step, at least one desired value for at least one parameter for adjusting and / or calibrating the focal value of the surgical microscope is determined by a predetermined contrast value for at least two zoom positions. For this purpose, the focal value for which the contrast value is maximum for each zoom position can be determined. The parameter for adjusting and / or calibrating the focal value of the surgical microscope should be understood to mean a variable value that can be changed in adjusting and / or calibrating the focal value, such as the distance between at least one objective lens and the imaging device or the distance between individual lenses or lens groups of a material-resistant lens.

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

[0010] Identifying the desired value may involve identifying the value of the change in focal position of a surgical microscope, particularly a value independent of zoom. Identifying the desired value, particularly the change value, may be based on the evaluation of the slope of at least one curve, e.g., a straight line, which maps the dependence of the detected focal change on the zoom position with respect to the focal value, or reference variable. The focal change can be expressed with respect to, for example, the position of the zoom center or other specified object-side reference points, e.g., object marks on an object (calibration object). The focal change can be expressed in any unit, which can be defined, for example, by the element imaged onto the object.

[0011] The functional relationship between the gradient and the focal position or focus setting of the surgical microscope, such as a linear dependence, can be inferred or determined by appropriate measurements. From this functional relationship, for example, the gradient of the corresponding line, the desired value and / or change can be directly calculated using the contrast values ​​specified for at least two different zoom positions, or the resulting absolute or relative focal value at which the contrast is maximized. The desired value can be calculated and / or provided and / or displayed and / or monitored, for example, in the form of a target focal line or target focal area in an image of a specified object at a particular zoom setting. This allows the technician to adjust and / or calibrate accordingly. The adjustment and / or calibration can be performed at a preset zoom setting or at any zoom setting.

[0012] The image acquisition device can be a camera such as a video camera. This may include a camera chip. The surgical microscope may have a stereoscopic optical system.

[0013] The present invention offers the advantage of enabling a surgical microscope equipped with a mechanical zoom system to focus independently of the main observation unit and optical reference instrument. Therefore, an optical reference instrument is not required for focus adjustment and / or calibration. The deviation from an ideal instrument pre-calibrated to infinity—that is, so that the light beams within the magnification system are parallel when focused on an object—can be quantified, for example, by the deviation of the focal value at which the contrast value is maximized. Focusing is also independent of the main observation unit, and therefore independent of the absence of an observer or subjective evaluation. Another advantage is that the use of measured calibration objects may also be unnecessary, as only relative focal values ​​are required for adjustment and / or calibration.

[0014] In a preferred variant, the surgical microscope includes, for example, at least one first objective lens in the form of a primary objective lens, and a second objective lens in the form of, for example, a video objective lens, wherein the second objective lens is positioned in the beam path between the first objective lens and the imaging device.

[0015] In an advantageous variant, at least one correction value for the relative position of at least one objective lens, e.g., a second objective lens and / or a first objective lens, and / or an imaging device, with respect to the beam path in the surgical microscope can be determined based on at least one desired value.

[0016] At least one desired value can be separately identified and / or specified for each of at least two zoom positions. At least one desired value can be identified and / or specified such that, for at least two beam positions, the difference between the focal values ​​at which the contrast value is maximized is less than a specified threshold for at least two zoom positions. This has the advantage that when the zoom position changes, if the difference is zero, the focal value changes only slightly or does not change at all.

[0017] For example, based on a determined focal value where the contrast value is maximum for each zoom setting, at least one desired value for at least one parameter for adjusting and / or calibrating the focal value of the surgical microscope can be identified and / or specified. As part of the adjustment, a second objective lens, i.e., a video objective lens, is preferably displaced so that a corresponding desired value for positioning and / or displacement can be identified and / or specified. At least one desired value for each of at least two zoom positions can be identified and / or specified at one of the two zoom positions or at the other zoom position. If the check shows that the surgical microscope has been properly adjusted, the desired value is equal to the actual value or within tolerance. This also enables monitoring or remote monitoring of the surgical microscope.

[0018] In a favorable modification, at least one image of the planar surface of a specified object can be captured, and the plane normal of this planar surface forms an angle with the optical axis of the objective lens between 0 and 90 degrees, particularly between 85 and 5 degrees, for example, 20 degrees. In other words, in the above example, the planar surface forms an angle with the optical axis of the objective lens between 90 and 0 degrees, particularly between 85 and 5 degrees, for example, 70 degrees. The use of a planar surface has the advantage that the distance of the object point from the objective lens can be easily determined, and therefore image evaluation is simplified.

[0019] Preferably, the object used is a known calibration object. This may have a defined pattern, such as a chessboard pattern. Therefore, an advantage is that at least one image of the specified calibration object is captured at each of at least two different zoom positions, and since this has known features, high-contrast regions can be recognized in the image representation. Knowing the geometric shape of the calibration object allows for the prediction of high-contrast regions in the image. These can be identified and evaluated in terms of contrast. This reduces computation time. For example, the calibration object could be a ChArUco board. The above-described variation facilitates the identification of contrast values ​​and provides a robust solution against errors due to potential noise. For example, only the contrast values ​​within a defined central region of the image can be identified and / or evaluated. This facilitates and speeds up adjustment and / or calibration.

[0020] An advantage is that the dimensions of the pattern, particularly the dimensions of the pattern elements, are known or predetermined, or these dimensions are measured. The dimensions can be known or predetermined, or measured, in units of length, e.g., millimeters. Preferably, an imaging scale, in the form of the relationship between the respective dimensions of at least one element of the calibration object, e.g., in millimeters, and the camera chip, e.g., in units of length, e.g., pixels, is known, predetermined, or measured. If the tilt of the calibration object is known or predetermined, or set or identified in a defined manner, the focal value can be identified, in particular, calculated, using the dimensions and / or imaging scale, relative to a point in the image representation, e.g., the zoom center where the contrast value is maximum. For example, the tilt of the calibration object can be identified using pose estimation. In addition, the tilt can be identified by the camera evaluating the geometric deformation that occurs when there is tilt in the captured image representation of the calibration object, e.g., the resulting trapezoid. The above configuration has the advantage that the focal value where the contrast value is maximum and the dependency between the contrast value and the focal value can be easily, quickly, and reliably identified.

[0021] At each of at least two zoom positions, an image of the specified object can be captured at multiple focal values. The focal value can be adjusted by a configurable focusing system. Unlike the aforementioned variant, where different focal values ​​are obtained due to the tilted placement of the calibration object in the image representation, the normal to the planar surface of the calibration object can form a 0-degree angle with the optical axis. For this purpose, the surgical microscope must be equipped with an objective lens having a variable focal length. By automatable corresponding focusing, a numerical table and / or curve mapping contrast values ​​to focal values ​​can be identified for each of at least two zoom positions. The focal value of the surgical microscope can be fitted using the contrast value curve. Alternatively, the calibration object can be moved along the optical axis.

[0022] In a favorable variant, the focal values ​​of the surgical microscope for each of at least two zoom positions are adjusted and / or calibrated separately, i.e., individually for each zoom position, thereby maximizing the contrast value for each of the at least two zoom positions. In other words, when the zoom position changes, the focal values ​​are readjusted or reset, for example, by stored data, and these are then permanently used to set or correct the focal values ​​accordingly during operation. In addition, or alternatively, in another favorable variant, the focal values ​​of the surgical microscope at at least two beam positions can be adjusted and / or calibrated such that the difference between the focal values ​​that maximize the contrast value for at least two zoom positions is less than a specified threshold.

[0023] The focal length of a surgical microscope can be adjusted and / or calibrated in several ways. For example, the focal length of a surgical microscope can be adjusted and / or calibrated by matching the distance between the object plane, e.g., a designated object, and at least one objective lens, e.g., a first objective lens, e.g., a primary objective lens, and / or a second objective lens, e.g., a video objective lens. Thus, in this variation, the focal length is matched by displacing at least one objective lens and / or the object relative to each other along the optical axis of this at least one objective lens.

[0024] In addition to, or as an alternative to, the focal value of the surgical microscope can be adjusted and / or calibrated by matching the distance between the objective lenses, for example, the first and / or second objective lenses, and the image plane of the imaging device. Thus, in this modification, at least one objective lens and the imaging device can be moved relative to each other in the direction of or along the optical axis of the objective lens, and in doing so, the objective lens and / or the imaging device can be moved.

[0025] At least one objective lens, for example the first and / or second objective lens, may comprise a first optical element and a second optical element. In addition to or as an alternative to the two variants described above, the focus value of a 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. It should be understood that an optical element refers to one or more optical components positioned relative to each other. For example, an optical element may comprise only one lens or a plurality of lenses. Therefore, in this variant, inner focusing is performed in each objective lens, for example in a main objective lens or a video objective lens. In particular, the optical apparatus may comprise a first objective lens, for example a main objective lens, and a second objective lens, for example a video objective lens, wherein the first objective lens is arranged in the beam path between the object plane and the second objective lens. 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 the focus value are set automatically. This facilitates adjustment and / or calibration and reduces the time required for adjustment and / or calibration.

[0027] The surgical microscope may comprise a stereoscopic optical system, which has or defines a first optical path and at least one further optical path. At least one desired value and / or calibration data relating to the first optical path can be determined and transmitted to the at least one further optical path. It should be understood that an optical path refers to the path of light from an object through the optical system to the image plane. The above-described variant has the advantage that only one of the plurality of optical paths needs to be adjusted and / or calibrated, the result of this process can be immediately used for at least one other optical path, and the latter does not need to be separately adjusted and / or calibrated. This reduces the time required to adjust and / or calibrate the stereoscopic optical system.

[0028] A control device according to the present invention for adjusting and / or calibrating and / or monitoring a focus value of a surgical microscope, the surgical microscope including at least one objective lens, an image capturing device and a zoom system and being designed to be operated at at least two different zoom positions, is designed to perform the aforementioned method according to the present invention. The control device has the features and advantages already described.

[0029] A surgical microscope according to the present invention includes at least one objective lens, an image capturing device such as a camera, particularly a video camera, and a zoom system. The surgical microscope is designed to be operated at at least two different zoom positions. The surgical microscope is also designed to perform the method according to the present invention already described above. The surgical microscope may include the control device according to the present invention described above. The surgical microscope according to the present invention has the features and advantages already described. It preferably comprises a stereoscopic optical system.

[0030] A computer-implemented method according to the present invention includes instructions that, when the program is executed by a computer, cause the computer to perform the above-described method according to the present invention. A computer program product according to the present invention includes instructions that, when the program is executed by a computer, cause the computer to perform the above-described method according to the present invention. The computer program product according to the present invention is stored on a computer-readable data carrier according to the present invention. A 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 aforementioned features and advantages.

[0031] The present invention will be described below based on exemplary embodiments with reference to the accompanying drawings. The present invention will be more specifically illustrated and described in detail by preferred exemplary embodiments, but nevertheless, the present invention is not limited by the examples disclosed, and those skilled in the art can devise other variations therefrom without departing from the scope of protection of the present invention.

[0032] The drawings are not necessarily accurate in all details and scale, and may be enlarged or reduced for clarity. Therefore, the functional details disclosed herein should be understood to be illustrative, not limiting, and intended to provide guidance to those skilled in the art for various uses of the invention.

[0033] In this specification, when the expression "and / or" is used in a list of two or more elements, it means that any of the listed elements may be used individually, or any combination of two or more of the listed elements may be used. For example, if a structure is described as containing components A, B, and / or C, that structure may include A only, B only, C only, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C. [Brief explanation of the drawing]

[0034] [Figure 1] The beam paths through the surgical microscope for the two beam positions are schematically shown. [Figure 2] The method according to the present invention is schematically shown in the form of a flowchart. [Figure 3] A schematic diagram of the contrast value curves corresponding to the focal value for two zoom positions is shown. [Figure 4] A schematic diagram of the contrast value curves corresponding to the focal value for four zoom positions is shown. [Figure 5] The surgical microscope and calibration object to be calibrated are shown schematically. [Figure 6] Two schematic images of the calibration object, taken at different zoom levels, are shown. [Figure 7] The changes in focal value depending on the zoom position for three different adjustment or calibration states are schematically shown in the form of a diagram. [Figure 8] This diagram schematically shows the contrast line (actual focus line) and the desired focus line in the captured image of the calibration object. [Figure 9] A schematic diagram shows a first variant of the surgical microscope according to the present invention, which has a control device according to the present invention. [Figure 10] A schematic diagram shows a second variant of the surgical microscope according to the present invention, which has a control device according to the present invention. [Modes for carrying out the invention]

[0035] The background of the present invention will be explained in more detail below with reference to Figure 1. Figure 1 schematically shows the beam path 10 in a surgical microscope at two zoom positions. In the upper part of Figure 1, a first zoom position with a low zoom value is set, and in the lower part of Figure 1, 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 not smaller than the zoom value of the beam path shown in the lower part.

[0036] The surgical microscope 1 includes a first objective lens 3 in the form of a primary objective lens and a second objective lens 2 in the form of a video objective lens, each containing at least one lens or lens group. The second objective lens 2 is positioned in the beam path between the first objective lens 3 and the imaging device 5. In Figure 1, the beam path 10 is shown upstream of the surgical microscope 1 on the left and downstream on the right. Therefore, the beam direction in Figure 1 extends from left to right. Starting from the object plane 4, the object point is imaged onto the image plane of the imaging device 5, for example, onto the camera tip. In the example shown, the first beam 11 and the second beam 12 each image the object point onto the camera tip 5. Beams 11 and 12 first pass through the first objective lens 3. The beam paths downstream of the first objective lens 3 and upstream of the second objective lens 2 are afocal. The regions where afocal radiation beams occur are indicated by reference numeral 6, respectively. Therefore, there are parallel beam paths in region 6.

[0037] When adjusting and / or calibrating the surgical microscope 1, at least one lens, the lens group of the video objective lens 2, or the camera tip 5 is moved along the optical axis 7, i.e., horizontally in Figure 1. When the video objective lens 2 is properly focused as shown in Figure 1, the beams forming the axial beam, i.e., the second beam 12 in this case, converge to a point on the camera tip 5, regardless of the zoom position, and therefore this point is neither in front of nor behind the camera tip 5.

[0038] An example of a method according to the present invention for adjusting and / or calibrating the focal value of a surgical microscope will be described in more detail below with reference to Figures 2-6. The surgical microscope includes at least one objective lens, for example, a first objective lens 3 in the form of a primary objective lens, a second objective lens 2 in the form of a video objective lens, an imaging device 5, and a zoom system, and is designed to be operated at at least two different zoom positions. The video objective lens 2 is positioned in the beam path 10 between the primary objective lens 3 and the imaging device 5.

[0039] Figure 2 schematically illustrates the method according to the present invention in the form of a flowchart. In the first step 21, at least one image or image representation of a designated object, preferably a known calibration object, is captured by the image acquisition device 5 at at least two different zoom positions. In the second step 22, one or more contrast values ​​are identified from at least one captured image, depending on the focal value. This is preferably done by appropriate image evaluation software, which is configured, for example, to quantify the black-and-white transition of the image with respect to contrast. In the third step 23, at least one desired value and optionally a correction value for at least one parameter for adjusting and / or calibrating the focal value of the surgical microscope are identified by the contrast values ​​identified for at least two zoom positions. In this regard, the focal value at which the contrast value is maximum for each zoom position can be identified. An example of the implementation of step 23 is described in more detail below with reference to Figures 6-8.

[0040] The specified focal values ​​with the maximum contrast value for each zoom position can be used in the optional step 24 to adjust and / or calibrate the surgical microscope, for example, by adjusting and / or calibrating it in such a way that the focal position, in particular the focal position of video objective lens 2, is fitted so that the maximum value of the contrast curve, i.e., the maximum value of at least two contrast curves, appears at the same focal value or with a focal difference smaller than an explicitly stated threshold. As soon as the desired focal difference is reached, the surgical microscope, in particular the video objective lens, is correctly adjusted and / or calibrated at the focal point. When the focal difference is zero, the surgical microscope, in particular the objective lens, is adjusted to infinity.

[0041] Alternatively, or in addition, in step 24, the identified focal values ​​that maximize the contrast value for each zoom position can be saved to control the surgical microscope and used when using individual zoom positions to adjust and / or calibrate the focal values. For example, after setting up and adjusting the surgical microscope, contrast value curves for various zoom positions can be recorded and saved to the instrument. Thus, if the zoom setting changes, new operating values ​​for the focus system can be identified and set from the saved curves. This ensures that sharp images are obtained. Therefore, only coarse adjustments may be necessary, or in some cases, no adjustments may be required. This digital calibration can be performed in the primary objective lens, in the video objective lens, or by displacing the camera chip. Thus, it is not necessary to perfectly fit the magnification system to infinity. However, other image errors may occur, which can be corrected digitally.

[0042] Figure 3 schematically shows the contrast value curves corresponding to the focal value for two zoom positions. Figure 4 schematically shows the contrast value curves corresponding to the focal value for four zoom positions. The x-axis plots the focal value f in millimeters, and the y-axis plots the contrast value normalized to 1. In Figure 3, contrast value curve 31 is identified at the zoom position with a zoom value of 1.0 and has a maximum value at a focal value of 211.6 mm. Contrast value curve 32 is identified at the zoom position with a zoom value of 2.4 and has a maximum value at a focal value of 211.4 mm. The focal values ​​of maximum contrast are relatively close to each other here, thereby allowing for the omission of further adjustments and / or calibrations if appropriate. In Figure 4, contrast value curves 33 at the zoom position with a zoom value of 1.0, 34 at the zoom position with a zoom value of 1.5, 35 at the zoom position with a zoom value of 2.0, and 36 at the zoom position with a zoom value of 2.4 are identified. Since the focal points for maximum contrast are relatively far apart, the adjustment and / or calibration of the surgical microscope can be performed using the contrast value curve.

[0043] There are several options for performing step 22, that is, for identifying multiple contrast values ​​depending on the focal value from the captured images. If the surgical microscope has a focusing system, i.e., can automatically set the focal value, the curves shown in Figures 3 and 4 can be acquired automatically. Thus, focusing can be performed automatically, and each image of the calibration object can be captured for individual focal values ​​and evaluated in terms of contrast. If an automatic zoom system is also available, individual zoom settings can also be set automatically.

[0044] If the focal value cannot be set automatically, the difference in focal length obtained from two zoom positions using a target positioned obliquely as an object can be visually read, or preferably identified by the image evaluation already described above. The difference in focal length allows for the necessary setting of the focal position of the optical instrument, particularly the video objective lens. A variation of this is described below with reference to Figures 5 and 6.

[0045] Figure 5 schematically shows the surgical microscope 40 and calibration object 41 to be adjusted and / or calibrated. The calibration object 41 is securely connectable to or can be securely connected to the surgical microscope 40.

[0046] A calibration object 41 having a planar surface 42 preferably with a known pattern, preferably a ChArUco pattern, is positioned obliquely to the optical axis 7. In this case, the surface normal 43 of the surface 42 of the calibration object 41 may form an angle of 5 to 85 degrees, for example, 20 degrees, with respect to the optical axis 7. This corresponds to an angle 45 of 85 to 5 degrees, for example, 70 degrees, between the surface 42 and the optical axis 7. For a tilted calibration object 41, the contrast value can be calculated for multiple focal values ​​in a given image.

[0047] An advantage is that the dimensions of the pattern, particularly the dimensions of the elements of the pattern, are known or predetermined, or these dimensions are measured. The dimensions can be known or predetermined, or measured, for example, in units of length, such as millimeters. Preferably, the imaging scale, in the form of relationships between the respective dimensions of at least one element of the pattern, for example, in pixels and in units of length, is known, predetermined, or measured. If the tilt of the calibration object 41 is known or predetermined, or set or identified in a predetermined manner, for example by pose estimation, the focal value at which the contrast value is maximized can be identified, in particular, calculated, using the dimensions and / or imaging scale. This configuration has the advantage that the focal value at which the contrast value is maximized, and the dependency between the contrast value and the focal value, can be easily, quickly, and reliably identified.

[0048] The modified version using the tilted calibration object 41 also offers the advantage that optical systems with a constant focal length, particularly surgical microscopes, can also be adjusted and / or calibrated. For this purpose, contrast value curves for at least two zoom positions are first identified, and then a desired focal position for at least one zoom position can be calculated and / or provided and / or displayed, thereby allowing the technician to adjust and / or calibrate the optical system using the displayed desired focal position (see, for example, Figure 8 below).

[0049] Figure 6 schematically shows two images 18 of the calibration object 41 taken at different zoom positions. The zoom center is located at, and preferably placed at, the center of the image. If the zoom center is not at the center of the image, it is beneficial to place the coordinate origin of the object-side coordinate system used at the object point of the zoom center (projection of the zoom center onto the object). In particular, the zoom center is a point in the captured image representation that does not move between different magnification levels. The zoom center can be seen in particular as the optical center of the observer's beam path. Camera systems are typically designed and / or adjusted so that the object point imaged at the center of the camera tip does not move within the image representation during zooming. In this case, the optical axis defined by the zoom system intersects the center of the camera tip. The calibration object 41 is tilted so that the focal value in Figure 6 changes from left to right. The image shown on the left was taken at the first zoom position, and the image shown on the right was taken at the second zoom position. The highest contrast line, i.e., the vertical line, in the images of the figure is indicated by reference numeral 46. The contrast line 46 in the second zoom position, i.e., the depiction shown on the right side of Figure 6, appears to the right of the calibration object 41 in the image, relative to the object mark 17 on the calibration object 41, compared to the contrast line 46 in the first zoom position shown on the left side of the figure. In other words, the contrast line 46 is approximately three squares to the left of the chessboard pattern (white or black squares) of the object mark 17 in the depiction shown on the left side of Figure 6, and approximately two squares to the left of the chessboard pattern of the object mark 17 in the depiction shown on the right side of Figure 6. Therefore, the contrast line 46 shifts relative to the calibration object 41 or the object mark 17. This means that when switching between the two zoom positions, the focal plane moves, or in other words, shifts, along the optical axis 7. If the contrast line 46 were always in the same position on the object, the difference in focal value would be zero. The object mark 17 can be placed anywhere on the object. The relative change or movement of the contrast line 46 remains the same. However, it is preferable to select an object point that coincides with the zoom center and therefore with the optical axis of the zoom system.

[0050] The horizontal displacement of the contrast line 46 from the first zoom position (see the left-hand depiction in Figure 6) to the second zoom position (see the right-hand depiction in Figure 6) on the calibration object 41, converted into a vertical difference, i.e., a difference in the direction of the optical axis 7, corresponds to the difference in focal value. This difference in focal value can be calculated from the displacement of the contrast line 46, the geometric shape and scale of the experimental arrangement, for example, the size of the ChArUco marks on the planar surface 42 of the calibration object 41. Typically, the focal plane is spherical, and therefore the contrast line 46 in the figure represents an approximation of the contrast curve. If the curvature of the contrast curve, i.e., the deviation of the contrast line 46 (straight line) in the figure from the actual contrast curve, is small, then the approximation as a line is valid. Otherwise, the actual contrast curve must be taken into account.

[0051] In all variations, it is advantageous to use a known calibration object, such as a chessboard or ChArUco board. This facilitates contrast detection and evaluation.

[0052] The change in the contrast line shown in Figure 6 indicates the shift or change in the focal value in response to the zoom position. This is schematically shown in the form of a chart in Figure 7. The zoom position Z is plotted on the x-axis, and the focal value F is plotted on the y-axis. The focal value can be expressed in millimeters, pixels, or any unit that characterizes the shift in focus relative to the calibration object 41, for example, the shift relative to the object mark 17 on the calibration object 41. The dimensions of the geometric shape or structure imaged on the calibration object 41 can be used as a scale. For example, in the example shown in Figure 6, the width of one of the imaged rectangles can be used as a scale. The procedure according to the present invention, which will be described in detail below, has the advantage that adjustment and / or calibration can be performed on any calibration object 41, since only the relative focal value, i.e., the deviation of the specified focal value from or from a reference point, is required. Therefore, a measured calibration object is not required.

[0053] Figure 7 shows the results of three measurements. For example, the focal value F was determined for zoom positions Z1 and Z2. Preferably, the focal value F is determined for three or more zoom positions Z. The function of the focal value is F = f(Z), which can be determined from the measured values ​​corresponding to the zoom position. Preferably, the gradient g(F~g * It can be assumed that the line is a straight line in Z). The shift in the focal value relative to the calibration object is represented by the gradient g. In adjustment and / or calibration, the absolute value of the gradient g should be small, preferably close to zero or set near zero. In other words, the line should preferably extend parallel to the x-axis in the result of adjustment and / or calibration.

[0054] In Figure 7, during the first measurement, the focal value F1 was identified at zoom value Z1, and the focal value F2 was identified at zoom value Z2. From these, a line 25 with a gradient g = (F2-F1) / (Z2-Z1) was identified. Subsequently, the focal value of the surgical microscope was increased or decreased by ΔF, and the second measurement was performed in the same manner as the first measurement. The increase or decrease can be performed at any zoom position. Here, a line 26 with a smaller gradient than line 25 was identified. Then, the focal value of the surgical microscope was further increased or decreased, and the third measurement was performed in the same manner as the first two measurements. In this case, a line 27 with a negative gradient was identified.

[0055] Based on the dependence between the change in the focal value ΔF of the surgical microscope and the gradient g (g=f(ΔF)) thus identified, the focal value of the surgical microscope can be adjusted or calibrated to obtain a gradient g of zero, or close to zero considering a given tolerance. Typically, there is a linear dependence that does not depend on the zoom (g~m*(ΔF), where m represents the increment), and it has been found that two measurements, for example, a first measurement with an inclined gradient object at a first zoom position and a second measurement with an inclined calibration object at a second zoom position, are basically sufficient to identify the numerical value by which the current focal value of the surgical microscope must be increased or decreased in order to change the desired or target value for adjustment and / or calibration, in particular the absolute value of the gradient g, as desired. Therefore, on the one hand, the dependence between the change in the focal value ΔF of the surgical microscope and the gradient g can be identified and assumed to be known in the method of the present invention described herein. In the latter case, the surgical microscope can be adjusted and / or calibrated based on the identification of only one gradient. The required change in the focal value can be specified, for example, in millimeters.

[0056] With regard to adjustment and / or calibration, specified desired or target values ​​can be displayed to the technician, for example, in the form of a tolerance bar, a tolerance strip, or a straight or curved line extending parallel to a specified contrast curve or contrast line 46. Figure 8 illustrates this schematically. In the example in the figure, the calibration object 41 is tilted so that the focus changes from top to bottom. In Figure 8, in the captured image 18 of the calibration object 41, the desired line is indicated by reference numeral 29, and the line with the highest contrast at the moment, i.e., the current contrast line, is indicated by reference numeral 28.

[0057] There are various options for adjusting and / or calibrating the focal value of the surgical microscope 1 for individual or all zoom positions, which can be applied individually or in combination with each other. The first variation involves changing the focal length, i.e., the distance between the object or object surface 4 and at least one of the objective lenses 2, 3. In a surgical microscope including a primary objective lens 3 and a video objective lens 2, in this case the primary objective lens 3 can be moved relative to the object or object surface 4. The second variation involves changing the distance between the objective lens 2 and the image plane 5 of the surgical microscope 1. In this case, the imaging equipment 5, i.e., a camera or camera tip, or the second objective lens 2 can be moved, i.e., displaced relative to each other.

[0058] A third variation involves using objective lenses 2, 3 that are capable of inner focusing and therefore include at least one first optical element and at least one second optical element, wherein the first and second optical elements are displaceable relative to each other. This means that at least one of the optical elements can be displaced while the other optical element remains fixed. In the case of a surgical microscope, the main objective lens 3 may be designed as an objective lens with a variable focal length. In addition to, or alternatively, a video objective lens 2 may be capable of performing appropriate inner focusing.

[0059] Figure 9 schematically shows a first variant of the surgical microscope 40 according to the present invention. The surgical microscope 40 includes a control device 13 according to the present invention, which is designed to perform a variation of the method according to the present invention, for example, the method described above with respect to Figures 2-8. The illustrated surgical microscope 40 includes a first objective lens 2, for example in the form of a video objective lens 2; a second objective lens 3, for example in the form of a main objective lens 3; a zoom system 8 for changing the zoom position; and an image acquisition device 5, for example a camera 5. The first objective lens 2 and / or the second objective lens 3 may be designed as objective lenses having variable focal lengths, and therefore each includes at least two lenses or lens groups that are displaceable relative to each other.

[0060] The first objective lens 3, the zoom system 8, the second objective lens 2, and the image acquisition device 5 are optically interconnected in this order, i.e., arranged continuously within the beam path 10. The control device 13 is connected to the aforementioned components 2, 3, 5, and 8 for signal transmission 15, and in particular controls the zoom system 8.

[0061] Figure 10 schematically shows a surgical microscope 40 according to the present invention, which is a second variation of the stereoscopic configuration. Unlike the variation shown in Figure 9, there are two video objective lenses 2 and an image acquisition device 5, particularly a camera chip, arranged in parallel with each other within the beam path 10. The zoom system 8 may have its own elements for each beam path, i.e., the first and second beam paths (separate beam paths or optical paths). The same, simultaneous displacement of the lenses can be achieved by mechanical, electronic, or electromechanical coupling. With respect to the method according to the present invention, at least one desired value and / or calibration data for the first optical path can be identified and transferred to the second optical path.

[0062] If a stereoscopic system calibration (e.g., in the form of a camera matrix and / or distortion coefficient) exists, a topography can be created during operation. The plane or sphere of the topography has the highest contrast and intersects the topography. This contrast evaluation can be performed on one camera image and / or both camera images. In the image representation, the point with the highest contrast can be indicated by a free curve in the camera image. If the focal value of the surgical microscope is set correctly, this free curve moves with the object in the camera image when the zoom setting is changed. This focal shift can then be calculated as a function of zoom (the slope of the line in Figure 7). If this is not the case, or if the relative shift in the topography is too large, a service technician can be notified for readjustment purposes, and / or the user can be informed. Alternatively, the user can be asked to perform this monitoring periodically. Thus, this method also allows for on-site monitoring of the focal value. [Explanation of Symbols]

[0063] 1 Surgical microscope 2. Second objective lens, video objective lens 3. First objective lens, primary objective lens 4 Object plane 5. Image capture device, camera chip, image plane 6 Afocal beam 7 Optical axis 8 Zoom System 10 Beam paths 11. The First Beam 12. The Second Beam 13 Control equipment 15 Signal Transmission 17 Object Mark 18. Image of the surface of the calibration object. 21. Take at least one image of the specified object at each of at least two different zoom positions. 22. Identify one or more contrast values ​​depending on the focal value from at least one captured image. 23 Using the contrast values ​​identified for at least two zoom positions, identify at least one desired value for at least one parameter for adjusting and / or calibrating the focal value. 24. Adjust and / or calibrate the surgical microscope. 25 First Measurement 26 Second Measurement 27 Third Measurement 28 Actual Focus Line 29. Target Focus Line 31. Contrast Value Curve 32 Contrast Value Curve 33. Contrast Value Curve 34. Contrast Value Curve 35 Contrast Value Curve 36. Contrast Value Curve 40 Surgical microscope 41 Calibration Objects 42 Planar surface 43 Surface normal 44 angle 45 angle 46 Contrast Lines f focus

Claims

1. A method for adjusting and / or calibrating and / or monitoring the focal value of a surgical microscope (1, 40) which includes at least one objective lens (2, 3), an imaging device (5), and a zoom system (8), and is designed to be operated at at least two different zoom positions, The following steps, namely, - Step (21) of capturing at least one image of the designated object (41) by the image capturing device (5) at at least two different zoom positions, - A step (22) of identifying a plurality of contrast values ​​according to the focal value using the at least one captured image, - Step (23) of identifying at least one desired value of at least one variable value that can be changed in adjusting and / or calibrating the focal value of the surgical microscope (1, 40) based on the contrast values ​​identified for at least two zoom positions, - Step (24) in which the at least one desired value for each of the at least two zoom positions is separately identified and / or specified and / or specified such that the at least one desired value for the at least two zoom positions is identified and / or specified such that the difference between the focal values ​​where the contrast value is greatest is less than a specified threshold for the at least two zoom positions, A method characterized by including the following.

2. At least one correction value for the relative position of the at least one objective lens (2, 3) and / or the imaging device (5) with respect to the beam path within the surgical microscope (1, 40) is determined based on the at least one desired value. Characterized by, The method according to claim 1.

3. As part of capturing an image of at least one of the designated object (41), an image (18) of the planar surface (42) of the designated object (41) is captured, wherein the planar surface (42) has a surface normal 43 that forms an angle (44) between 5 and 85 degrees with the optical axis (7) of the objective lenses (2, 3). Characterized by, The method according to claim 1 or 2.

4. For each of the at least two zoom positions, the image (18) of the designated object (41) is captured at multiple focal values. Characterized by, The method according to claim 1 or 2.

5. The aforementioned focus value is set using a configurable focus system. Characterized by, The method according to claim 4.

6. The focal values ​​of the surgical microscope (1, 40) for each of the at least two zoom positions are separately adjusted and / or calibrated (24) such that the contrast value for each of the at least two zoom positions is maximized. and / or The focal values ​​of the surgical microscope (1, 40) for at least two zoom positions are adjusted and / or calibrated such that the difference between the focal values ​​at which the contrast value is maximum is less than an explicitly stated threshold for at least two zoom positions (24). Characterized by, The method according to claim 1 or 2.

7. The focal value of the surgical microscope (1, 40) is To adjust the distance between the object surface (4) and the objective lenses (2, 3), and / or By adjusting the distance between the objective lenses (2, 3) and the image plane of the image capture device (5), and / or By displacing the first optical element of the at least one objective lens (2, 3) relative to the second optical element of the at least one objective lens (2, 3) Adjusted and / or calibrated Characterized by, The method according to claim 1 or 2.

8. The zoom position and / or focal value are set automatically. Characterized by, The method according to claim 1 or 2.

9. At each of the two different zoom positions, at least one image of a designated calibration object having known characteristics is captured such that high-contrast regions are recognizable within the image representation, and / or only the contrast values ​​in a designated central region of the image are identified and / or evaluated. Characterized by, The method according to claim 1 or 2.

10. The surgical microscope has a stereoscopic optics system, which has a first optical path and at least one other optical path, wherein at least one desired value and / or calibration data for the first optical path is identified and transferred to the at least one other optical path. Characterized by, The method according to claim 1 or 2.

11. The aforementioned focal value is a relative focal value in the form of a change in focus or a shift in focus according to the zoom setting. Characterized by, The method according to claim 1 or 2.

12. The identification of the desired value includes identifying a value of the change in focal position that is independent of the zoom of the surgical microscope, and the identification of the desired value and / or the change value is based on an evaluation of the slope of at least one curve mapping the dependence of the captured focus change on the focal value or a reference variable value from the zoom position, and a functional relationship between the slope and the focusing of the surgical microscope is used. Characterized by, The method according to claim 1 or 2.

13. The desired value is calculated and / or provided in the form of a target focal line or target focal region in a captured image of the specified object. Characterized by, The method according to claim 1 or 2.

14. A control device (13) for adjusting and / or calibrating and / or monitoring a surgical microscope (1, 40) which includes at least one objective lens (2, 3), an imaging device (5), and a zoom system (8), and is designed to be operated at at least two different zoom positions, The control device (13) is characterized in that it is designed to perform the method described in claim 1 or 2.

15. A surgical microscope (1, 40) comprising at least one objective lens (2, 3), an imaging device (5), and a zoom system (8), and designed to be operated at at least two different zoom positions, Designed to perform the method described in claim 1 or 2, and comprising the control device (13) described in claim 14. A surgical microscope characterized by (1, 40).

16. Features a stereoscopic viewing system Characterized by, The surgical microscope (1, 40) according to claim 15.

17. A computer implementation method that includes an instruction causing a computer to execute the method according to claim 1 or 2 when the program is executed by the computer.

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