Optical target for checking the calibration of a medical imaging device

Abstract

The invention relates to an optical target (20, 20', 20'') for checking a stereoscopic 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 formed as a light-outcoupling structure which is configured to couple light out of the target body in an amplified manner. The invention further relates to an optical calibration system (12) and a medical system (10).

Description

The present application relates to an optical target for geometric calibration of a medical imaging device, in particular for geometric calibration of a stereo endoscope or a stereo endoscope.In medical geometric imaging, stereo endoscopes and stereo endoscopes belong to the prior art, by means of which magnification representations of an examination region can be generated. In the case of stereo endoscopes or stereo endoscopes, a 3D image is generated and displayed on a monitor. In this case, disparity must be set in such a way that the zero plane (i.e. disparity=0, lies in the zero plane, the two individual images directly one on top of the other) lies at the working distance r. All objects in this null plane appear to the viewer as if they were directly in the monitor plane. Objects viewed at a closer working distance appear to the viewer in front of the monitor. Objects that are viewed farther than the working distance appear to the viewer in front of the monitor. Objects farther than the working distance of the zero plane appear to the viewer to be at the depth behind the monitor.Furthermore, by means of fluorescence imaging methods, different slices, for example organs and / or blood vessels and / or other tissue, can be spatially visualized again more precisely at different depths below the skin and / or below the organs into which the endoscope is introduced. For this purpose, the patient is administered a medicament with florescences, which deposits in one of the different layers. That is to say that one of the different layers can additionally have fluorescence properties during medical imaging, which can be identified by the stereo endoscope and / or stereo endoscope. Furthermore, multimodal medical imaging methods can also be used. For this purpose, the patient is administered a plurality of medicaments using different fluorescence imaging methods which each mark different slices with different fluorescences.In summary, surgeons obtain very accurate spatial information through medical geometric imaging and can therefore more intuitively estimate and / or track individual actions via a screen.In order to realize reliable medical geometric imaging, it is important to calibrate the stereo zero plane and the fluorescence imaging method of the stereo endoscopes and / or stereo endoscopes.In the prior art, fluorinating test beads with a calibration pattern are used for this purpose. However, the fluorinating test rats bleach out by photobleaching over time and therefore cannot ensure constant test conditions over a longer time. In order to visualize constant test conditions over a longer time, optical matted glass panes with LEDs are also used, which emit light at a different wavelength. Such systems are not suitable for the end user, for example for surgical personnel for calibrating the stereo endoscopes and stereo endoscopes directly in the surgical room, since the function of all LEDs would have to be checked before the calibration in a complicated error-prone manner.Furthermore, the above arrangement does not allow to simulate more complex test setups that are urgent to require for a multimodal medical imaging method and that replicate different fluorescence at different penetration depths.Proceeding from the prior art, the object of the invention is to calibrate an image acquisition unit in a simple manner.This object is achieved according to the invention by an optical target and a medical system as described herein and defined in the claims.The present invention provides an optical target for checking a 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 decoupling structure which is configured to couple light out of the target body in an amplified manner.The features according to the invention allow simple calibration of an image acquisition unit. The optical target can be used for stereoscopic calibration of the medical imaging device and / or for calibration of the fluorescence imaging methods of the medical imaging device. In particular, the stereo zero plane of the stereoscopic imaging of the medical imaging device can be calibrated by the optical target.The medical imaging device can be, in particular, an exoscope. Alternatively or additionally, the imaging device can be an endoscope, for example. The medical imaging device can be configured to record images of an examination region. In some embodiments, the imaging device may be configured to generate magnification representations of the examination region. The representation may be observed during the performance of a medical procedure and / or during a diagnostic action. The medical imaging device can be mobile and / or movable. It can be provided that the imaging device is movable, for example, in an operating room. If a user requires support by imaging, for example, the imaging device can be movable to the place of use, that is to say, for example, to a patient. The imaging device may also be movable in itself. The image acquisition unit can comprise a movable holding arm, for example, and / or the image acquisition unit can be arranged on the movable holding arm.The target body defines in particular at least one outer surface of the optical target. At least from one spatial direction, light can be coupled or introduced through the target body into the optical target. Preferably, light can be coupled or introduced into the optical target from all spatial directions through the target body. For example, light is coupled or introduced into the optical target at least through an outer surface of the target body, preferably from all outer surfaces of the target body.The calibration pattern can be applied to the target body and / or introduced into the target body. The calibration pattern can thus be its own structure which is applied to the target body. The calibration pattern can be bonded to the target body, for example, and / or be applied additive to the target body, for example, by a 3D printing method. Furthermore, the calibration pattern can be introduced into the target body and therefore represent, for example, a depression in the target body.Due to the configuration according to the invention, daylight and / or an external light source, which is likewise provided for illuminating the room, may already be sufficient for the optical target to be illuminated sufficiently for calibration of the medical imaging device.In particular, the features according to the invention can provide an optical target which has comparable properties over an increased period of time, can be handled in a user-friendly manner and cannot be adversely influenced by user errors.In order to improve the detection of the calibration pattern by the medical imaging device, the calibration pattern can diffusely scatter the light.The calibration pattern can furthermore comprise at least one line and / or a cross or be designed in the form of a line and / or a cross. The line and / or the cross may also include isolated elements, such as dots, bars, or other objects, arranged on a line and / or a cross, in some embodiments, thereby forming the line and / or the cross. The line and / or the cross can be easily recognized in the calibration image. Furthermore, it is particularly well suited to checking the optical calibration. A cross may preferably be provided. The optical calibration can be checked in two spatial directions in a simple manner by means of the cross.In order to apply the calibration pattern to the target body at low cost 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 scribe and / or at least one gap, in an outer surface of the target body.In particular, the calibration pattern can be formed by a surface treatment, preferably by sandblasting, for cost-effective production. For example, partial regions of an outer surface of the target body can be sand blasted to form the calibration pattern.In particular for calibrating the fluorescence imaging method of the medical imaging device, for example in cooperation with the stereoscopic imaging of the medical imaging device and / or stereoscopic imaging of the medical imaging device, the optical target can in particular comprise at least one conversion region which is configured to convert light having a first wavelength at least partially into second light having a second wavelength different from the first wavelength. In particular, for this purpose, conversion region can have luminescent properties. For example, the conversion region can be configured to convert light having the first wavelength at least partially into the second illumination light having the second wavelength different from the first wavelength by means of the luminescent properties.Furthermore, the conversion region can be partially transmissive for light having the first wavelength. For example, the conversion region can be configured to convert 10%-100%, in particular 30%-80%, preferably 40%-60%, of the amount of light and / or of the luminous flux of the light having the first wavelength into light having the second wavelength. In addition, the conversion region can be configured to convert light into narrow spectral bands according to the remaining features. Eng can mean that the converted spectral band is, for example, up to 200 nm, in particular 100 nm, preferably 50 nm, particularly preferably 20 nm wide. The conversion region can be configured in particular to emit light having the second wavelength. The emitted light can be used for illuminating the optical target. Alternatively or additionally, light with the first wavelength can be used to illuminate the optical target. For example, the conversion region can be configured to convert light and transmit light alternately in time.The conversion region can comprise filters configured for light conversion. The conversion region can be configured in particular to absorb light with the first wavelength and to emit light with the second wavelength. Further, in some embodiments, alternatively or additionally, the wavelength of the light having the first wavelength may be bisected by means of the conversion, for example by second harmonic generation (SHG) and / or frequency multiplication by means of nonlinear 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 comprise quantum dots.The conversion region may comprise a light-transmissive or a light-partially transmissive plate. The conversion region may alternatively or additionally comprise a transluminescent plate. Furthermore, the conversion region can comprise a coating which acts in such a way that a greater amount of light and / or a greater luminous flux with the second wavelength can be emitted. Alternatively or additionally, the conversion region can comprise a film, in particular a matted film, and / or be laminated. The optional plate of the conversion region can be covered, for example, on one side and / or on both sides with the film. On one side and / or two sides, reference can be made in particular to the sides to which the light having the first wavelength can be guided or from which light having the second wavelength can be emitted.For example, the at least one conversion region has a rectangular and / or round shape and / or the shape of an anatomical vessel such as, for example, blood vessels. The shape of the conversion region can be simulated to a blood vessel. For example, the conversion region can be cylindrical and / or tubular. As a result, it is possible to use optical targets during the calibration of the medical imaging device, which reset realistic structures or, if appropriate, reset simplified, but realistic structures, which are recorded by the optical target during an operation, for example.To form more complex, realistic structures, the optical target can further comprise at least two conversion regions. Furthermore, the first and / or second wavelengths of the two conversion regions may be different. For example, a first conversion structure can be configured to convert light having a first wavelength at least partially into second light having a second wavelength different from the first wavelength. Furthermore, a second conversion structure can be configured to convert light having a third wavelength at least partially into second light having a fourth wavelength different from the third wavelength. In this case, the first wavelength can differ from the third wavelength. Alternatively or additionally, the second wavelength may be different from the fourth wavelength.In order to ensure that the medical imaging device has the desired penetration depth, for example the penetration depth required for the operation, the optical target can have a plurality of conversion regions which are arranged one above the other and / or next to one another.In order to realize an even more realistic calibration of the medical imaging device, a blood vessel and / or organ and / or a body part can be at least partially simulated by at least two conversion regions. Furthermore, in order to simulate an organ and / or to simulate different marker / fluorescent solutions which are dissolved in different parts / layers of the organs or vessels of the organs, the optical target can have a plurality of conversion regions with different conversion properties of wavelengths.In a particularly simple and cost-effective configuration of the optical target, a conversion region can fill the target body at least substantially completely and in particular completely. The target body can be manufactured, in particular completely, from a material which is configured to convert light having a first wavelength at least partially into second light having a second wavelength different from the first wavelength.Furthermore, the target body can be formed from acrylic gas so that light can be easily introduced into the optical target.In particular, the optical target is produced by a generative manufacturing method, in particular a 3D printing method. As a result, the optical target can be manufactured cost-effectively. Furthermore, the 3D printing method can be used to realize a conformal and exact production of the optical target. Furthermore, the optical target can be manufactured by the 3D printing method in such a way that it simulates realistic conditions.Generative manufacturing or "additive manufacturing" describes in particular a method with which an object is built up layer by layer, for example a 3D printing method. Starting materials for generative production are, in particular, molding sands, polymer gypsums, acrylic resins, plastics, metals and / or acrylic glass. Preferably, acrylic glass is used for additive manufacturing in the present invention.Furthermore, an optical calibration system can be provided. The optical calibration system comprises a target according to the invention and a holder which is provided to make the optical target couplable to the stereoscopic medical imaging device to be examined. By means of the holder, it can be achieved that the checking of the geometric calibration can be carried out reproducibly. Furthermore, the calibration system can be easily operated by the holder, in particular in that the calibration system can be aligned efficiently, easily and / or easily with respect to the imaging device.The fixture may also include a spacer that defines a distance between the medical imaging device under test and the target. The distance can correspond, for example, approximately to the distance that the imaging apparatus, in particular an image acquisition unit and / or input optics of the imaging device, can usually have during operation to an object to be examined. In addition, the distance may be specifically tunable with the optical target and / or with the imaging device. The distance can correspond at least substantially to a focal length of a first image capturing device and / or a focal length of a second image capturing device of the medical imaging apparatus. 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. Reproducibility of the inspection can be increased. Furthermore, the check can be standardizable.In addition, the holder can be configured to bear the dead weight of the calibration system in a state coupled to the medical imaging device to be calibrated. This can mean that the calibration system can be coupled to the imaging device in such a way that the calibration system is not standing on the ground. That is, the calibration system does not need to comprise a stand leg and / or the like. The system comprising the calibration system and the imaging device can thus be more dynamically couplable. Advantageously, fewer oscillations and / or a lower oscillation energy can be transmitted to the calibration system via the ground. Accuracy of the inspection can be improved. Furthermore, the calibration system can be made more compact.The holder can also have openings through which ambient light can reach the target body or in order to ensure that the ambient light falls onto the target body. For example, mirrors may be further mounted on the mount to increase a portion of the ambient light that falls onto the target body.The holder can also comprise a coupling section for coupling to the medical imaging device to be examined, wherein the coupling section comprises a protrusion which is configured to hold the calibration system by engaging behind it. The imaging device may also include a holding portion to which the holder is couplable. For example, the projection can at least partially engage behind the holding section. Furthermore, the projection can be configured to hold during the coupling of the calibration system by engaging behind, in particular at least in sections, the holding section. The calibration system can be rotated about the projection, for example during the coupling, in particular while the latter partially engages behind the holding section. The protrusion may be rotatably supported in the holding portion. The calibration system, in particular the coupling section and / or the projection, and the imaging device, in particular the holding section, can together form a connection. The connection may comprise, for example, a dovetail connection. As a result, a compact and / or efficient calibration system can be provided.The coupling section can further comprise a movable holding element which is configured to selectively fix the holder to the medical imaging device to be tested or to release it therefrom. For example, the holder can be clampable to the imaging device by means of the holding element. Alternatively or additionally, the movable holding element can be configured to engage behind the imaging device, in particular the holding section, in sections. The movable holding element can comprise, for example, a clampable holding element, in particular a clamping spring, an adjusting spring and / or the like, a screw and / or a latching nose. As a result, the calibration system can be selectively fixable to the imaging device and / or detachable therefrom in a simple manner. Coupling can take place in a short time and / or flexibly.In particular, sections and / or points of the calibration pattern of the optical target that are spaced apart by the holder can have different distances from the stereoscopic medical imaging device to be examined. That is to say that the optical target can be arranged obliquely and / or at an angle to the stereoscopic medical imaging device to be examined by the holder. Preferably, the optical target is arranged obliquely and / or at an angle with respect to the stereoscopic medical imaging device to be examined only in one direction of the optical target. More specifically, 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°.In particular, spaced-apart sections and / or points of the calibration pattern have different distances from the stereoscopic medical imaging device to be examined. Spaced-apart sections and / or points of an imaginary line, which is perpendicular to the line of the calibration pattern, can in particular have substantially equal distances to the stereoscopic medical imaging device to be examined. If the calibration pattern is configured as a cross, for example, spaced sections and / or points of a line have different distances from the stereoscopic medical imaging device to be examined, and spaced sections and / or points of a further line have substantially equal distances from the stereoscopic medical imaging device to be examined.Preferably, the calibration pattern does not lie in a plane with the stereoscopic medical imaging device to be examined. Then, when superimposed on the left eye perception image and the right eye perception image, the reproduction of the calibration pattern in the left eye perception image intersects the reproduction of the calibration pattern in the right eye perception image. The position of the intersection indicates the position of the zero plane of the stereoscopic medical imaging device to be examined. The determination of the position of the intersection or the position of the intersection point can be carried out automatically, in particular by the stereoscopic medical imaging device.Furthermore, the stereoscopic medical imaging device to be checked is located 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 in a plane orthogonal to the main viewing direction of the stereoscopic medical imaging device.In particular, the distance between the stereoscopic medical imaging device to be examined and the target body and / or the distances of the various points and / or the spaced sections of the calibration pattern of the optical target between the stereoscopic medical imaging device to be examined and the target body can be adjustable.In particular, the distance between the stereoscopic medical imaging device to be examined and the target body and / or the distances of the various points of the calibration pattern of the optical target between the stereoscopic medical imaging device to be examined and the target body can be adjustable by the holder and / or a robot arm in which the holder is clamped, for example. The robot arm and / or holder arm can be movable by motor, in particular by stepping motors. The holder arm and / or the robot arm can have in particular position sensors for detecting positions of its degrees of freedom and can comprise, for example, a position control system in order to be able to move to defined positions.The invention further comprises a medical system having a medical imaging device and an optical target for checking a stereoscopic calibration of the medical imaging device. Furthermore, the medical imaging device to be examined can have a fluorescence channel and / or a plurality of fluorescence channels and / or a white light channel.The present invention is described below by way of example with reference to the attached figures. The drawings, specification and claims contain numerous features in combination. The person skilled in the art will also expediently consider the features individually and use them in combination within the scope of the claims.If more than one instance is present from a particular object, only one of them may be provided with a reference sign in the figures and in the description. The description of this instance can be transferred to the other instances from the object accordingly. If objects are designated in particular by means of numerical words, such as first, second, third objects, etc., these are used for designating and / or assigning objects. Accordingly, for example, a first object and a third object, but no second object, can be included. However, a number and / or an order of objects could also be derived additionally on the basis of numerical words.The following are shown: FIG. 1 shows an exemplary embodiment of an optical target according to the invention; FIG. 2 shows a further exemplary embodiment of an optical target according to the invention; FIG. 3 shows an exemplary embodiment of a medical system according to the invention having a medical imaging device and an optical target according to the invention for checking a stereoscopic calibration of the medical imaging device.FIG. 1 shows an exemplary embodiment of an optical target 20 having a target body 40 and a calibration pattern 50. the calibration pattern 50 is designed as a line, for example, but can also be designed as a cross or have a different shape, for example. The target body 40 can be formed from glass and / or acrylic glass, for example. The calibration pattern 50 can be a depression in the target body 40 and / or can be applied to the target body 40.FIG. 2 shows a further exemplary embodiment of an optical target 20' with a target body 40' and a calibration pattern 50'. The calibration pattern 50 is configured as a cross by way of example, but can also be configured as a line or have a different shape by way of example. The target body 40' can be formed from glass and / or acrylic glass, for example. The calibration pattern 50' can be a depression in the target body 40 and / or can be applied to the target body 40. Furthermore, a conversation region 60 and a conversion region 60' are provided in the target body 40'. The conversion regions 60 and 60' are, for example, round and arranged next to one another. The conversion regions 60 and 60' can also be arranged one below the other. Further conversion regions can also be introduced into the target body 40'. Furthermore, the conversion regions can also have further shapes than those illustrated, in order to be able to simulate partial regions of organs, for example.FIG. 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 formed as a cross, for example. The optical target 20" is part of an optical calibration system 12. In the present 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 plugged onto the opposite end of the spacer 80 which is connected to the receptacle 72. A distance 90 can be realized between the target body 40" and the medical imaging device 30 by means of the spacer 80. The spacer 80 further has holes 85, so that more ambient light can strike the target body 40'' or so that a shadow is prevented on the target body 40''.The distance 90 may be variable by the spacer 80 and / or the bracket 70 and / or a robotic arm (not shown) into which the bracket 70 is clamped.The target body 40" can be introduced obliquely and / or tilted (not shown) into the receptacle 71 and / or attached to the receptacle 72. That is, when the target body 40" is placed obliquely and / or tilted in the receptacle 71, different points or spaced-apart sections of the calibration pattern 50" of the target body 40" are at a different distance from the medical imaging device 30. The oblique placement of the target body 40", i.e., an angle at which the target body 40" is placed relative to and / or on the imaging device 30 to be inspected, may be variable. The angle can be changed, for example, by the receptacle 72 and / or the holder 70 and / or a robot arm into which the holder 70 is clamped and / or on which the holder 70 is arranged.The medical imaging apparatus 30 can comprise a first image capturing device and a second image capturing device, which are each light-sensitive in the first spectral range. Furthermore, the medical imaging apparatus 30 can comprise a third image capturing device and fourth image capturing device, which are each light-sensitive in the further spectral range. By means of the first image capturing device and the third image capturing device, stereo image capturing in the first spectral range can be carried out, for example. By means of the second image capturing device and the fourth image capturing device, stereo image capturing in the second spectral range can be carried out, for example. In particular, the second spectral range lies in the near infrared range. As a result, a fluorescence stereo image acquisition can be carried out by means of the second image acquisition device and the fourth image acquisition device.In order to enable fluorescence imaging, the image capturing devices can further comprise image sensors which are light-sensitive in different spectral ranges. The first image capturing device and the second image capturing device can each comprise a first image sensor which is light-sensitive at least predominantly in the first spectral range, which is associated in particular with the visible light. That is, image acquisition in the wavelength range of visible light can be carried out by means of the first image sensor. This corresponds approximately to the current image acquisition. By means of the second image sensor, image acquisition in the wavelength range of the near infrared light can be carried out.The second image capturing device and the fourth image capturing device can each comprise a second image sensor. The second image sensor can be light-sensitive at least predominantly in the second spectral range, in particular light-insensitive in the wavelength range of visible light. For calibrating such a medical imaging device 30, the optical target 20" can provide light in both spectral ranges through, for example, a plurality of, in particular two, conversion regions in order to be able to check the geometric calibration of the medical imaging device 30. To check the geometric calibration, the medical imaging device 30 records the target 20 or the target body 40" with the calibration pattern 50". In particular, each of the image capturing devices captures at least one image of the target body 40" with calibration pattern 50". On the basis of the images of the target body 40" with calibration pattern 50", the user can check the geometric calibration of the image acquisition unit 64, for example.List of reference characters10 Medical system 12 Optical calibration system 20, 20', 20" Optical target 30 Medical imaging device 40, 40', 40" Target body 50, 50', 50" Calibration pattern 60, 60' Conversion region 70 Holder 72 Holder 80 Spacer 85 Openings 90 Distance

Claims

An optical target (20, 20', 20") for checking a 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 formed as a light decoupling structure which is configured to decouple light amplified from the target body.The optical target (20, 20', 20") of claim 1, wherein the calibration pattern (50, 50', 50") diffusely scatters the light.The optical target (20, 20', 20") according to any one of the preceding claims, wherein the calibration pattern (50, 50', 50") is formed in the shape of a line or a cross.The optical target (20, 20', 20") according to any one of the preceding claims, wherein the calibration pattern (50, 50', 50") is a depression, preferably in the form of at least one scribe and / or at least one gap, in an outer surface of the target body (40, 40', 40").The optical target (20, 20', 20") according to any one of the preceding claims, wherein the calibration pattern (50, 50', 50") is formed by a surface treatment, preferably by sandblasting.The optical target (20, 20', 20") according to any one of the preceding claims, further comprising: at least one conversion region (60) configured to at least partially convert light having a first wavelength into second light having a second wavelength different from the first wavelength.The optical target (20, 20', 20") according to claim 6, wherein the conversion region (60) has luminescent properties, wherein the conversion region (60) is configured to convert light having the first wavelength at least partially into the second illumination light having the second wavelength different from the first wavelength on the basis of the luminescent properties.The optical target (20, 20', 20") according to any one of claims 6 or 7, wherein the at least one conversion region (60) has a rectangular and / or round shape and / or the shape of a blood vessel.The optical target (20, 20', 20") according to any one of claims 6 to 8, further comprising: at least two conversion regions (60),The optical target (20, 20', 20") according to claim 9, wherein the first and / or second wavelengths of the two conversion regions (60, 60') are different.Optical target (20, 20', 20") according to one of Claims 6 to 10, wherein a plurality of conversion regions (60) are arranged one above the other and / or next to one another.Optical target (20, 20', 20") according to one of Claims 6 to 11, wherein a blood vessel and / or organ and / or a body part is at least partially simulated by at least two conversion regions (60).The optical target (20, 20', 20") according to any one of claims 6 to 8, comprising: a conversion region (60) which at least substantially completely fills the target body (40, 40', 40").The optical target (20, 20', 20") of any preceding claim, wherein the target body (40, 40', 40") is formed of acrylic gas.Optical target (20, 20', 20") according to one of the preceding claims, which is produced generatively, in particular by means of a 3D printing method.An optical calibration system (12) comprising: an optical target (20, 20', 20") according to any preceding claim; and a holder (70) provided to make the optical target (20, 20', 20") couplable to the stereoscopic medical imaging device (30) to be inspected.The calibration optical system (12) of claim 16, wherein the holder (70) comprises a spacer (80) defining a distance (90) between the stereoscopic medical imaging device (30) to be examined and the target body (40, 40', 40").The optical calibration system of claim 17, wherein different points and / or spaced apart portions of the calibration pattern of the optical target (20, 20', 20") are at different distances from the stereoscopic medical imaging device (30) to be examined.The optical calibration system according to claim 16 or 17, wherein the distance (90) between the stereoscopic medical imaging device (30) to be examined 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 examined and the target body (40, 40', 40") are adjustable.A medical system (10) comprising: a medical imaging device (30); and an optical target (20, 20', 20") for checking 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.The medical system (10) according to claim 20a, wherein the medical imaging device (30) to be examined comprises a fluorescence channel and / or a plurality of fluorescence channels and / or a white light channel.

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