Optical target for verifying the calibration of a medical imaging device

Abstract

Optical target (20, 20', 20'') for verifying the calibration of a medical imaging device (30) comprising: a target body (40, 40', 40'') into which light can be coupled; and a calibration pattern (50, 50', 50'') for calibrating a stereo zero plane of the medical imaging device (30), wherein the calibration pattern is formed in and / or on the target body, and wherein the calibration pattern (50, 50', 50'') is configured as a light-extracting structure which is designed to extract light from the target body in an enhanced manner.

Description

[0001] The present application relates to an optical target for the geometric calibration of a medical imaging device, in particular for the geometric calibration of a stereoendoscope or a stereoexoscope.

[0002] In medical geometric imaging, stereoendoscopes and stereoexoscopes are state-of-the-art devices used to generate magnified images of an examination area. With stereoendoscopes and stereoexoscopes, a 3D image is generated and displayed on a monitor. The disparity must be adjusted so that the zero plane (i.e., disparity = 0, where the two individual images lie directly on top of each other) is located at the working distance r. All objects in this zero plane appear to the viewer as if they were lying directly in the monitor plane. Objects viewed at a closer working distance appear to the viewer in front of the monitor. Objects viewed further away than the working distance also appear to the viewer in front of the monitor. Objects located further away than the working distance of the zero plane appear to the viewer to be in the depth behind the monitor.

[0003] Furthermore, fluorescence imaging techniques allow for more precise spatial visualization of different layers, such as organs, blood vessels, and / or other tissues, at varying depths beneath the skin and / or under the organs into which the endoscope is inserted. For this purpose, the patient is administered a fluorescing medication that accumulates in one of the different layers. This means that one of the layers can exhibit additional fluorescence properties during the medical imaging procedure, which can be identified by the stereoendoscope and / or stereoexoscope. Multimodal medical imaging techniques can also be used. In this approach, the patient is administered several medications with different fluorescence imaging techniques, each of which highlights different layers with distinct fluorescence patterns.

[0004] In summary, medical geometric imaging provides surgeons with very accurate spatial information, allowing them to assess and / or track their own actions more intuitively via a screen.

[0005] To achieve reliable medical geometric imaging, it is necessary to calibrate the stereo zero plane and the fluorescence imaging method of the stereoendoscopes and / or stereoexoscopes.

[0006] In the current art, fluorescent test cards with a calibration pattern are used for this purpose. However, these fluorescent test cards fade over time due to photobleaching and therefore cannot guarantee consistent test conditions over extended periods. To visualize consistent test conditions over longer periods, optically frosted glass plates with LEDs emitting light at different wavelengths are used. Such systems are not suitable for end users, such as operating room personnel calibrating stereoendoscopes and stereoexoscopes directly in the operating room, because the functionality of all LEDs would first have to be checked in a time-consuming and error-prone manner before calibration.

[0007] Further documents relating to this are known from the prior art: FR 2 921 479 A1, DE 10 2020 201 806 A1, WO 2023 / 148 225 A1.

[0008] Furthermore, the above arrangement does not make it possible to simulate more complex test setups, which are urgently needed for a multimodal medical imaging procedure and which replicate different fluorescence at different penetration depths.

[0009] Based on the prior art, the invention aims to easily calibrate an image acquisition unit.

[0010] This problem is solved according to the invention by an optical target and a medical system as described herein and defined in the claims.

[0011] The present invention provides for an optical target for verifying the calibration of a medical imaging device. The optical target comprises a target body into which light can be coupled; and a calibration pattern for calibrating a stereo zero plane of the medical imaging device. The calibration pattern is formed in and / or on the target body. Furthermore, the calibration pattern is designed as a light-extracting structure configured to extract light from the target body in an amplified manner.

[0012] The features according to the invention allow for simple calibration of an image acquisition unit. The optical target can be used for stereoscopic calibration of the medical imaging device and / or for calibrating the fluorescence imaging methods of the medical imaging device. In particular, the optical target can be used to calibrate the stereo zero plane of the stereoscopic imaging of the medical imaging device.

[0013] The medical imaging device can be, in particular, an exoscope. Alternatively or additionally, the imaging device can be, for example, an endoscope. The medical imaging device can be configured to acquire images of an examination area. In some embodiments, the imaging device can be configured to generate magnified images of the examination area. The image can be viewed during a medical procedure and / or during a diagnostic procedure. The medical imaging device can be mobile and / or movable. It can be designed, for example, to be movable within an operating room. If a user requires imaging support, the imaging device can be moved to the point of use, such as a patient. The imaging device can also be movable within itself.The image acquisition unit may, for example, include a movable support arm and / or the image acquisition unit may be arranged on the movable support arm.

[0014] The target body defines, in particular, at least one outer surface of the optical target. Light can be coupled or introduced into the optical target through the target body from at least one spatial direction. Preferably, light can be coupled or introduced into the optical target through the target body from all spatial directions. For example, light is coupled or introduced into the optical target through at least one outer surface of the target body, preferably from all outer surfaces of the target body.

[0015] The calibration pattern can be applied to the target body and / or embedded within it. The calibration pattern can therefore be a separate structure applied to the target body. For example, the calibration pattern can be glued to the target body and / or additively applied to it, such as through a 3D printing process. Furthermore, the calibration pattern can be embedded within the target body and thus, for example, represent a recess in the target body.

[0016] According to the invention, daylight and / or an external light source, which is also provided for illuminating the room, can be sufficient to illuminate the optical target adequately for calibrating the medical imaging device.

[0017] In particular, the features according to the invention can provide an optical target that exhibits comparable properties over an extended period, is user-friendly and cannot be negatively affected by user errors.

[0018] To improve the detection of the calibration pattern by the medical imaging device, the calibration pattern can diffusely scatter the light.

[0019] The calibration pattern can further comprise at least one line and / or a cross, or be designed in the form of a line and / or a cross. In some embodiments, the line and / or cross can also include isolated elements such as dots, dashes, or other objects arranged on a line and / or a cross, thereby forming the line and / or the cross. The line and / or cross is easily recognizable in the calibration pattern. Furthermore, it is particularly well suited for verifying the optical calibration. A cross is preferentially provided. Using the cross, the optical calibration can be easily verified in two spatial directions.

[0020] In order to apply the calibration pattern to the target body cost-effectively and to further improve the recognition of the calibration pattern by the medical imaging device, the calibration pattern can be a depression, preferably in the form of at least one slit and / or at least one gap, in an outer surface of the target body.

[0021] In particular, the calibration pattern can be formed cost-effectively by a surface treatment, preferably by sandblasting. For example, to form the calibration pattern, sections of an outer surface of the target body can be sandblasted.

[0022] Particularly for calibrating the fluorescence imaging method of the medical imaging device, for example in conjunction with stereoscopic imaging, the optical target can, in particular, comprise at least one conversion region configured to convert light with a first wavelength at least partially into second light with a second wavelength different from the first. In particular, the conversion region can exhibit luminescent properties. For example, the conversion region can be configured to use its luminescent properties to convert light with the first wavelength at least partially into the second illumination light with a second wavelength different from the first.

[0023] Furthermore, the conversion region can be partially transparent to light of the first wavelength. For example, the conversion region can be configured to convert 10% to 100%, in particular 30% to 80%, preferably 40% to 60% of the amount of light and / or the luminous flux of the light of the first wavelength into light of the second wavelength. In addition, the conversion region can be configured to convert light into narrow spectral bands, according to the other features. "Narrow" can mean that the converted spectral band is, for example, up to 200 nm, in particular 100 nm, preferably 50 nm, and particularly preferably 20 nm wide. The conversion region can, in particular, be configured to emit light of the second wavelength. The emitted light can be used to illuminate the optical target. Alternatively or additionally, light of the first wavelength can be used to illuminate the optical target.For example, the conversion area can be set up to alternately convert and allow light to pass through over time.

[0024] The conversion region can include filters configured for light conversion. In particular, the conversion region can be configured to absorb light of the first wavelength and emit light of the second wavelength. Furthermore, in some embodiments, the wavelength of the light of the first wavelength can alternatively or additionally be halved by means of the conversion, for example, by frequency doubling (second harmonic generation, SHG) and / or frequency multiplication using non-linear optical processes. For example, the second wavelength can be a wavelength from the ultraviolet range. Furthermore, quantum dots can be provided for light conversion, or the conversion region can include quantum dots.

[0025] The conversion area can comprise a translucent or semi-translucent panel. Alternatively or additionally, the conversion area can comprise a translucent panel. Furthermore, the conversion area can comprise a coating that allows a greater amount and / or luminous flux of the second wavelength to be emitted. Alternatively or additionally, the conversion area can comprise a film, in particular a frosted film, and / or be laminated. The optional panel of the conversion area can, for example, be covered with the film on one side and / or both sides. "One side and / or two sides" can refer in particular to the sides onto which the light of the first wavelength can be directed or from which the light of the second wavelength can be emitted.

[0026] For example, at least one conversion area has a rectangular and / or round shape and / or the shape of an anatomical vessel, such as a blood vessel. The shape of the conversion area can be modeled on a blood vessel. For example, the conversion area can be cylindrical and / or tubular. This allows the use of optical targets during the calibration of the medical imaging device that replicate realistic structures or, if necessary, simplified but realistic structures that might be recorded by the optical target during surgery.

[0027] To create more complex, realistic structures, the optical target can have at least two conversion regions. Furthermore, the first and / or second wavelengths of the two conversion regions can be different. For example, a first conversion structure can be configured to convert light with a first wavelength, at least partially, into light with a second wavelength that differs from the first. A second conversion structure can be configured to convert light with a third wavelength, at least partially, into light with a fourth wavelength that differs from the third. In this case, the first wavelength can differ from the third wavelength. Alternatively or additionally, the second wavelength can differ from the fourth wavelength.

[0028] To ensure that the medical imaging device has the desired penetration depth, for example, the penetration depth required for surgery, the optical target can have multiple conversion areas arranged one above the other and / or next to each other.

[0029] To achieve a more realistic calibration of the medical imaging device, at least two conversion regions can be used to at least partially simulate a blood vessel and / or organ and / or body part. Furthermore, to simulate an organ and / or to replicate different markers / fluorescence solutions dissolved in different parts / layers of the organs or vessels, the optical target can have multiple conversion regions with different wavelength conversion properties.

[0030] In a particularly simple and cost-effective embodiment of the optical target, a conversion region can fill the target body at least substantially, and in particular completely. The target body can be made, in particular completely, of a material designed to convert light with a first wavelength, at least partially, into a second light with a second wavelength different from the first.

[0031] Furthermore, the target body can be made of acrylic gas so that light can easily be introduced into the optical target.

[0032] In particular, the optical target is manufactured using an additive manufacturing process, specifically 3D printing. This allows for cost-effective production of the optical target. Furthermore, 3D printing enables the optical target to be manufactured with high dimensional accuracy and precision. Additionally, 3D printing allows the optical target to be manufactured in such a way that it closely replicates realistic conditions.

[0033] Additive manufacturing describes, in particular, a process by which an object is built up layer by layer, for example, a 3D printing process. Starting materials for additive manufacturing include, in particular, molding sands, polymer gypsum, acrylic resins, plastics, metals, and / or acrylic glass. Preferably, acrylic glass is used for additive manufacturing in the present invention.

[0034] Furthermore, an optical calibration system can be provided. The optical calibration system comprises a target according to the invention and a holder designed to allow the optical target to be coupled to the stereoscopic medical imaging device under test. The holder enables the geometric calibration to be checked reproducibly. Moreover, the calibration system is easy to operate thanks to the holder, in particular because the calibration system can be aligned efficiently, easily, and / or simply with respect to the imaging device.

[0035] The mount may also include a spacer that defines a distance between the medical imaging device under test and the target. This distance may, for example, correspond approximately to the distance that the imaging device, in particular an image acquisition unit and / or the input optics of the imaging device, would typically have in operation relative to an object under examination. Furthermore, the distance may be specifically tunable with the optical target and / or with the imaging device. The distance may correspond at least substantially to a focal length of a first image acquisition unit and / or a focal length of a second image acquisition unit of the medical imaging device. In some embodiments, the distance may be at least 5 cm, at least 10 cm, or at least 20, 20', 20" cm and / or at most 100 cm, at most 80 cm, or at most 50, 50', 50" cm.The reproducibility of the inspection can be increased. Furthermore, the inspection can be standardized.

[0036] Furthermore, the mounting can be designed to support the weight of the calibration system when coupled to the medical imaging device being calibrated. This means that the calibration system can be coupled to the imaging device in such a way that it does not rest on the floor. In other words, the calibration system does not need to include a stand or similar support. This allows for a more dynamically efficient coupling of the system, particularly between the calibration system and the imaging device. Advantageously, fewer vibrations and / or less vibrational energy can be transmitted to the calibration system via the floor. This can improve the accuracy of the verification. Additionally, the calibration system can be designed more compactly.

[0037] The mount may also have openings through which ambient light can reach the target body, or to ensure that the ambient light falls on the target body. For example, additional mirrors may be attached to the mount to increase the proportion of ambient light that falls on the target body.

[0038] The mount can also include a coupling section for connecting to the medical imaging device under test, wherein the coupling section includes a projection configured to hold the calibration system by engaging behind it. The imaging device can also include a holding section to which the mount can be coupled. For example, the projection can engage behind the holding section, at least partially. Furthermore, the projection can be configured to hold the calibration system during coupling by engaging behind it, in particular at least partially behind the holding section. The calibration system can be rotated about the projection during coupling, particularly while the projection is partially engaging behind the holding section. The projection can be rotatably mounted in the holding section.The calibration system, in particular the coupling section and / or the projection, and the imaging device, in particular the holding section, can jointly form a connection. The connection can, for example, include a dovetail joint. This can result in a compact and / or efficient calibration system.

[0039] The coupling section can further comprise a movable retaining element designed to selectively fix the holder to or detach it from the medical imaging device under test. For example, the retaining element can clamp the holder to the imaging device. Alternatively or additionally, the movable retaining element can be designed to engage the imaging device, particularly the holding section, section by section. The movable retaining element can include, for example, a tensionable retaining element, in particular a clamping spring, a spring adjuster, and / or the like, a screw, and / or a locking lug. This allows the calibration system to be easily and selectively fixed to and / or detached from the imaging device. Coupling can be performed quickly and / or flexibly.

[0040] In particular, sections and / or points of the optical target's calibration pattern spaced apart by the mount can have different distances to the stereoscopic medical imaging device under test. This means that the mount allows the optical target to be positioned obliquely and / or at an angle to the stereoscopic medical imaging device under test. Preferably, the optical target is positioned obliquely and / or at an angle to the stereoscopic medical imaging device under test only in one direction. In particular, the angle is at most 80°, 70°, 50°, or 40° and is not less than 20°, 40°, or 50°. Preferably, the angle is at most 70° and is not less than 20°.

[0041] In particular, spaced sections and / or points of the calibration pattern have different distances to the stereoscopic medical imaging device under test. Spaced sections and / or points of an imaginary line perpendicular to the line of the calibration pattern may, in particular, have substantially equal distances to the stereoscopic medical imaging device under test. If the calibration pattern is in the form of a cross, for example, spaced sections and / or points of one line have different distances to the stereoscopic medical imaging device under test, and spaced sections and / or points of another line have substantially equal distances to the stereoscopic medical imaging device under test.

[0042] Preferably, the calibration pattern is not in the same plane as the stereoscopic medical imaging device under test. When the images intended for left-eye perception and right-eye perception are superimposed, the reproduction of the calibration pattern in the left-eye image intersects or overlaps the reproduction of the calibration pattern in the right-eye image. The position of the intersection or the point of overlap indicates the position of the zero plane of the stereoscopic medical imaging device under test. Determining the position of the intersection or the point of overlap can be automated, particularly by the stereoscopic medical imaging device itself.

[0043] Furthermore, the stereoscopic medical imaging device to be tested is positioned by the holder, for example, at a predetermined position and in a predetermined orientation relative to the calibration pattern of the optical target. When the optical target is clamped in the holder, the calibration pattern of the optical target is preferably not located in a plane orthogonal to the main viewing direction of the stereoscopic medical imaging device.

[0044] In particular, the distance between the stereoscopic medical imaging device under test and the target body and / or the distances between the different points and / or the spaced sections of the calibration pattern of the optical target between the stereoscopic medical imaging device under test and the target body can be adjustable.

[0045] In particular, the distance between the stereoscopic medical imaging device under test and the target body, and / or the distances between the various points of the optical target's calibration pattern between the stereoscopic medical imaging device under test and the target body, can be adjusted by the mount and / or a robot arm into which, for example, the mount is clamped. The robot arm and / or mount arm can be motorized, in particular by stepper motors. The mount arm and / or the robot arm can, in particular, have position sensors for detecting the positions of its degrees of freedom and can, for example, include a position control system to enable it to move to defined positions.

[0046] The invention further comprises a medical system with a medical imaging device and an optical target for verifying the stereoscopic calibration of the medical imaging device. The medical imaging device to be tested may further comprise one or more fluorescence channels and / or a white light channel.

[0047] The present invention is described below by way of example with reference to the accompanying figures. The drawing, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and use them meaningfully in combination within the scope of the claims.

[0048] If more than one instance of a particular object exists, only one of them may be identified with a reference symbol in the figures and description. The description of this instance can then be applied to the other instances of the object. If objects are named using numerical terms, such as first, second, third object, etc., these serve to identify and / or classify objects. Thus, for example, a first object and a third object, but not a second object, may be included. However, numerical terms could also indicate a number and / or sequence of objects.

[0049] They show: Fig. 1 an exemplary embodiment of an optical target according to the invention; Fig. 2 another exemplary embodiment of an optical target according to the invention; Fig. 3 an exemplary embodiment of a medical system according to the invention comprising a medical imaging device and an optical target according to the invention for verifying a stereoscopic calibration of the medical imaging device.

[0050] Fig. Figure 1 shows an exemplary embodiment of an optical target 20 with a target body 40 and a calibration pattern 50. The calibration pattern 50 is shown as a line, but could also be a cross or have another shape. The target body 40 could be made of glass and / or acrylic glass, for example. The calibration pattern 50 could be a recess in the target body 40 and / or could be applied to the target body 40.

[0051] Fig. Figure 2 shows another exemplary embodiment of an optical target 20' with a target body 40' and a calibration pattern 50'. The calibration pattern 50 is shown as a cross, but can also be a line or have another shape. The target body 40' can be made of glass and / or acrylic glass, for example. The calibration pattern 50' can be a recess in the target body 40 and / or applied to the target body 40. Furthermore, a conversion area 60 and a conversion region 60' are incorporated into the target body 40'. The conversion regions 60 and 60' are shown as round and arranged side by side. The conversion regions 60 and 60' can also be arranged one above the other. Additional conversion regions can also be incorporated into the target body 40'.Furthermore, the conversion areas can also have other shapes than those shown, for example to recreate parts of organs.

[0052] Fig.Figure 3 shows a schematic representation of a medical system 10 with a medical imaging device 30 and an optical target 20''. The optical target 20'' comprises a target body 40'' and a calibration pattern 40'', which is exemplarily designed as a cross. The optical target 20'' is part of an optical calibration system 12. The optical calibration system 12 further comprises a holder 70 into which the target body 40'' can be inserted. In this case, the holder 70 has a receptacle 72 for the optical target 20''. One end of a spacer 80 is attached to the receptacle 72. The medical imaging device 30 is attached to the opposite end of the spacer 80, which is connected to the receptacle 72. The spacer 80 allows a distance 90° to be established between the target body 40'' and the medical imaging device 30.The spacer 80 has further holes 85 to allow more ambient light to hit the target body 40'' or to prevent shadows from being cast on the target body 40''.

[0053] The distance 90 can be varied by means of the spacer 80 and / or the bracket 70 and / or a robot arm (not shown) into which the bracket 70 is clamped.

[0054] The target body 40'' can be inserted into the receptacle 71 and / or attached to the receptacle 72 at an angle and / or tilt (not shown). This means that if the target body 40'' is inserted at an angle and / or tilt in the receptacle 71, different points or defective sections of the calibration pattern 50'' of the target body 40'' will have different distances from the medical imaging device 30. The angled insertion of the target body 40'', i.e., the angle at which the target body 40'' is inserted relative to and / or attached to the imaging device 30 under test, can be variable. The angle can be changed, for example, by the receptacle 72 and / or the mount 70 and / or a robotic arm into which the mount 70 is clamped and / or on which the mount 70 is attached.

[0055] The medical imaging device 30 can comprise a first image acquisition unit and a second image acquisition unit, each of which is light-sensitive in the first spectral range. Furthermore, the medical imaging device 30 can comprise a third image acquisition unit and a fourth image acquisition unit, each of which is light-sensitive in the wider spectral range. For example, stereo imaging in the first spectral range can be performed using the first and third image acquisition units. Stereo imaging in the second spectral range can be performed using the second and fourth image acquisition units. In particular, the second spectral range lies in the near-infrared range.This makes it possible to perform fluorescence stereo image acquisition using the second image acquisition device and the fourth image acquisition device.

[0056] To enable fluorescence imaging, the image acquisition devices can include further image sensors that are light-sensitive in different spectral ranges. The first and second image acquisition devices can each include a first image sensor that is light-sensitive, at least predominantly, in the first spectral range, which is primarily associated with visible light. This means that image acquisition in the wavelength range of visible light is possible using the first image sensor. This corresponds approximately to conventional image acquisition. Image acquisition in the wavelength range of near-infrared light is possible using the second image sensor.

[0057] The second and fourth image acquisition devices can each comprise a second image sensor. The second image sensor can be light-sensitive, at least predominantly, in the second spectral range, and in particular light-insensitive in the wavelength range of visible light. For the calibration of such a medical imaging device 30, the optical target 20'' can provide light in both spectral ranges, for example, through several, and in particular two, conversion areas, in order to verify the geometric calibration of the medical imaging device 30. To verify the geometric calibration, the medical imaging device 30 captures the target 20 or the target body 40'' with the calibration pattern 50''. In particular, each of the image acquisition devices captures at least one image of the target body 40'' with the calibration pattern 50''.For example, the user can check the geometric calibration of the image acquisition unit 64 using the images of the target body 40'' with calibration pattern 50''. Reference symbol list 10 medical system 12 optical calibration system 20, 20', 20'' optical target 30 medical imaging devices 40, 40', 40'' Target body 50, 50', 50'' Calibration pattern 60, 60' conversion area 70 bracket 72 recording 80 spacers 85 openings 90 distance

Claims

[1] Optical target (20, 20', 20'') for verifying the calibration of a medical imaging device (30) comprising: a target body (40, 40', 40'') into which light can be coupled; and a calibration pattern (50, 50', 50'') for calibrating a stereo zero plane of the medical imaging device (30), wherein the calibration pattern is formed in and / or on the target body, and wherein the calibration pattern (50, 50', 50'') is configured as a light-extracting structure which is designed to extract light from the target body in an enhanced manner. [2] Optical target (20, 20', 20'') according to claim 1, wherein the calibration pattern (50, 50', 50'') diffusely scatters the light. [3] Optical target (20, 20', 20'') according to any of the preceding claims, wherein the calibration pattern (50, 50', 50'') is formed in the form of a line or a cross. [4] Optical target (20, 20', 20'') according to any of the preceding claims, wherein the calibration pattern (50, 50', 50'') is a depression, preferably in the form of at least one slit and / or at least one gap, in an outer surface of the target body (40, 40', 40''). [5] Optical target (20, 20', 20'') according to one of the preceding claims, wherein the calibration pattern (50, 50', 50'') is formed by a surface treatment, preferably by sandblasting. [6] Optical target (20, 20', 20'') according to any one of the preceding claims, further comprising: at least one conversion area (60) which is set up to convert light of a first wavelength at least partially into second light of a second wavelength different from the first wavelength. [7] Optical target (20, 20', 20'') according to claim 6, wherein the conversion area (60) exhibits luminescent properties, wherein the conversion area (60) is designed to convert light with the first wavelength, at least partially, into the second illumination light with the second wavelength different from the first wavelength, due to the luminescent properties. [8] Optical target (20, 20', 20'') according to one of claims 6 or 7, wherein the at least one conversion area (60) has a rectangular and / or round shape and / or the shape of a blood vessel. [9] Optical target (20, 20', 20'') according to any one of claims 6 to 8, further comprising: at least two conversion areas (60), [10] Optical target (20, 20', 20'') according to claim 9, wherein the first and / or second wavelengths of the two conversion ranges (60, 60') are different. [11] Optical target (20, 20', 20'') according to any one of claims 6 to 10, wherein several conversion areas (60) are arranged one above the other and / or next to each other. [12] Optical target (20, 20', 20'') according to any one of claims 6 to 11, wherein at least two conversion areas (60) at least partially replicate a blood vessel and / or organ and / or a body part. [13] Optical target (20, 20', 20'') according to any one of claims 6 to 8, comprising: a conversion area (60) that at least substantially fills the target body (40, 40', 40''). [14] Optical target (20, 20', 20'') according to any of the preceding claims, wherein the target body (40, 40', 40'') is formed from acrylic gas. [15] Optical target (20, 20', 20'') according to any of the preceding claims, which is produced additively, in particular by means of a 3D printing process. [16] Optical calibration system (12), comprising: an optical target (20, 20', 20'') according to any one of the preceding claims; and a holder (70) designed to allow the optical target (20, 20', 20'') to be coupled to the stereoscopic medical imaging device (30) to be tested. [17] Optical calibration system (12) according to claim 16, wherein the holder (70) comprises a spacer (80) which defines a distance (90) between the stereoscopic medical imaging device (30) to be tested and the target body (40, 40', 40''). [18] Optical calibration system according to claim 17, wherein different points and / or spaced-apart sections of the calibration pattern of the optical target (20, 20', 20'') have different distances to the stereoscopic medical imaging device (30) to be tested. [19] Optical calibration system according to claim 16 or 17, wherein the distance (90) between the stereoscopic medical imaging device (30) to be tested and the target body (40, 40', 40'') and / or the distances of the different points of the calibration pattern of the optical target (20, 20', 20'') between the stereoscopic medical imaging device (30) to be tested and the target body (40, 40', 40'') are adjustable. [20] Medical system (10), comprising: a medical imaging device (30); and an optical target (20, 20', 20'') for verifying a stereoscopic calibration of the medical imaging device (30) according to any one of claims 1 to 15 and / or an optical calibration system according to claims 16 to 19. [21] Medical system (10) according to claim 20, wherein the medical imaging device (30) to be tested has a fluorescence channel and / or several fluorescence channels and / or a white light channel.

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