Surgical microscope

Abstract

Surgical microscope (2, 48) for viewing an eye (77), having a main objective (5) and a fundus imaging system (71) which can be positioned in the beam path (7) between the eye (77) and the main objective (5), said system comprising an ophthalmoscopy magnifying glass (73), characterized in that the main objective (5) has a focal length in the range between 90 mm and 160 mm, and the fundus imaging system (71) comprises an optical group (81) whose dispersion properties are adapted to the dispersion properties of the ophthalmoscopy magnifying glass (73) in such a way that the optical group (81) compensates for a chromatic aberration of the ophthalmoscopy magnifying glass (73).

Description

[0001] The present invention relates to a surgical microscope for observing an eye and, more particularly, to a surgical microscope for retinal surgery.

[0002] Surgical microscopes for retinal surgery are typically used in conjunction with ophthalmoscopic loupes, which allow the fundus of the eye to be viewed with the surgical microscope. Ophthalmoscopic loupes provide a wide-angle view, projecting the fundus or retina onto an intermediate image, which is then viewed with the surgical microscope. Without the ophthalmoscopic loupe, a wide-angle view of the fundus or retina would not be possible. Ophthalmoscopic loupes are often mounted on swivel devices that connect them to the surgical microscope so that they can be pivoted into the viewing beam path of the surgical microscope.Ophthalmoscopy magnifiers and surgical microscopes with ophthalmoscopy magnifiers are described, for example, in DE 35 39 009 A1, DE 10 2006 047 459 A1, DE 10 2008 011 608 A1, DE 10 2010 001 853 A1, EP 2 316 330 B1, US 4 786 161 A, US 5 321 447 A, US 5 706 073 A, US 2003 / 0214629 A1, US 2005 / 0012992 A1 and WO 2016 / 033952 A1.

[0003] DE 10 2008 041 284 A1 describes a surgical microscope with a pivoting ophthalmoscopy magnifier and a main objective with a variable focal length. By varying the focal length of the main objective, the working distance can be adjusted within a range of 200 mm to 500 mm.

[0004] DE 602 20 630 T2 describes the use of a stereoscopic surgical microscope for examining the fundus of the eye with the aid of a contact prism or a contact lens held against the cornea. To compensate for any chromatic aberration that may occur, an optical element is arranged in each stereoscopic partial beam path between the main objective and the zoom system of the respective partial beam path.

[0005] In DE 10 2010 001 853 A1 and US 5 321 447 A, the ophthalmoscopy magnifiers are integrated into an attachment module for a surgical microscope. In addition to the ophthalmoscopy magnifier, the attachment module includes a lens that can be moved along the optical axis and is located between the intermediate image and the main objective of the surgical microscope when the attachment module is attached to the surgical microscope. The movable lens allows for focusing on different areas of the eye.

[0006] In DE 35 39 009 A1, the ophthalmoscopy magnifier is also part of an attachment module for a surgical microscope. In addition to the ophthalmoscopy magnifier, the attachment module also includes an additional lens positioned between the intermediate image and the main objective of the surgical microscope. This lens, located near the intermediate image, adjusts the aperture to the aperture of the main objective of the surgical microscope.

[0007] The described combinations of surgical microscope and ophthalmoscopy loupe often have the disadvantage of suboptimal image quality. This suboptimal image quality results from the fact that the image quickly reaches the diffraction limit. Another reason for the suboptimal image quality is that ophthalmoscopy loupes with high refractive power are often designed as single lenses, which lead to significant image aberrations.

[0008] In view of this prior art, it is therefore an object of the present invention to provide a surgical microscope with a fundus imaging system comprising an ophthalmoscopy magnifier, with which a high image quality can be achieved.

[0009] This object is achieved by a surgical microscope according to claim 1. The dependent claims contain advantageous embodiments of the invention.

[0010] A surgical microscope according to the invention for viewing an eye comprises a main objective and a fundus imaging system positionable in the beam path between the eye and the main objective. The fundus imaging system is equipped with an ophthalmoscopy magnifier. In the surgical microscope according to the invention, the main objective has a focal length in the range between 90 and 160 mm, in particular between 100 and 150 mm, and further in particular between 100 and 135 mm.

[0011] By reducing the focal length of the main objective to a focal length in the range between 90 and 160 mm, in particular between 100 and 150 mm and further in particular between 100 and 135 mm, this is reduced compared to the usual focal length of a main objective of 200 mm by a factor in the range between approximately 1.25 and 2.2, in particular between 1.3 and 2 and further in particular between 1.5 and 2. This increases the image scale with which the aperture diaphragms or the optical elements acting as aperture diaphragms in the stereoscopic partial beam paths are imaged onto the plane of the pupil of the eye to be examined. The images of the aperture diaphragms or the optical elements acting as aperture diaphragms in the plane of the pupil of the eye to be examined are imaged.The optical elements acting as aperture diaphragms define the entrance pupil for the optical system consisting of the crystalline lens, fundus imaging system, and main objective. This entrance pupil, in turn, determines the aperture angle of a beam of rays emanating from the retina being viewed, thus contributing to the numerical aperture of the aforementioned optical system. Enlarging the entrance pupil increases the numerical aperture of the optical system consisting of the crystalline lens, fundus imaging system, and surgical microscope, thus increasing the resolving power of this system. This increase in resolving power prevents the system from reaching the diffraction limit as quickly, thus improving the optical quality of the image.

[0012] The surgical microscope can be designed, in particular, as a digital surgical microscope with at least one digital image sensor, which allows for a smaller overall height of the microscope. The surgical microscope can then be equipped with a software or hardware module for digitally magnifying the image captured by the image sensor. Because the image captured with the digital image sensor has a higher resolution than that of a surgical microscope with a standard main objective with a focal length of 200 mm, the image captured with the digital image sensor offers more scope for digital magnification.

[0013] In addition, the fundus imaging system of the surgical microscope according to the invention comprises an optical group whose dispersion properties are adapted to the dispersion properties of the ophthalmoscopy magnifier in such a way that they compensate for chromatic aberration, in particular the transverse chromatic aberration (lateral chromatic aberration), of the ophthalmoscopy magnifier. The ophthalmoscopy magnifier typically consists of only one type of glass, the dispersion properties of which cause the chromatic aberration. This results in both longitudinal chromatic aberration (longitudinal chromatic aberration), which is caused by different focal lengths for different wavelengths, and transverse chromatic aberration, which is attributable to a different image scale of the ophthalmoscopy magnifier for different wavelengths.Transverse chromatic aberration causes images at different wavelengths in the intermediate image plane to have different sizes, with this effect increasing with increasing distance from the optical axis in the image field. Transverse chromatic aberration is also partly a result of longitudinal chromatic aberration, which increases with increasing pupil size. Chromatic aberration, and in particular transverse chromatic aberration, can therefore partially counteract the increase in image quality achieved by enlarging the entrance pupil. The full benefit of the larger entrance pupil can therefore only be achieved in conjunction with the optical group that compensates for chromatic aberration. But even without enlarging the entrance pupil, compensating for chromatic aberration, especially transverse chromatic aberration, improves image quality.

[0014] The ophthalmoscopy magnifier forms an intermediate image located between the ophthalmoscopy magnifier and the main objective. The optical group is particularly effective at compensating for chromatic aberration when positioned between the intermediate image and the main objective, especially when positioned closer to the intermediate image than to the main objective. Preferably, the distance of the optical group from the main objective corresponds to at least 1.5 times, and in particular at least 2.5 times, the distance of the optical group from the intermediate image.

[0015] In a particular embodiment of the surgical microscope according to the invention, the main objective can be a varioscope objective whose focal length can be varied between 90 and 160 mm, in particular between 100 and 150 mm, and more particularly between 100 mm and 135 mm. The use of a varioscope objective as the main objective enables focusing on a wide range of different positions of the intermediate images. For example, in the case of nearsighted and farsighted patient eyes, but also in the case of severely detuned patient eyes, for example in patient eyes filled with viscoelastic or air for application reasons, the position of the intermediate image varies compared to a normal, non-ametropiacal eye. Using the varioscope objective, the surgical microscope can be focused on the different positions of the intermediate images, so that a sharp fundus image can be generated in every situation.Furthermore, this design of the surgical microscope allows the fundus imaging system to be equipped with at least two interchangeable ophthalmoscopic loupes. Different ophthalmoscopic loupes typically have different intermediate image lengths, which can be focused on by adjusting the varioscope lens.

[0016] In a further embodiment of the surgical microscope according to the invention, it can comprise an OCT path (OCT: optical coherence tomography). Particularly when the surgical microscope is designed as a digital surgical microscope, additional depth information on the observed structures can be obtained with the help of the OCT path and added to the image. Furthermore, the OCT path can be used to optimally maintain or optimally adjust the distance between the patient's eye and the optics. For this purpose, the fundus imaging system can comprise a distance adjustment system for adjusting the distance of the ophthalmoscopy magnifier. This distance adjustment system can be a manual distance adjustment system. However, if the distance adjustment system comprises a motor for motor-controlled adjustment of the distance of the ophthalmoscopy magnifier from the eye, a control unit connected to the motor and the OCT path can be present.This is then designed to determine the distance of the surgical microscope from the fundus from an OCT signal obtained using the OCT path and to adjust the distance of the ophthalmoscopy loupe from the eye based on the determined distance of the surgical microscope from the fundus. This allows for automatic adjustment of the appropriate distance of the ophthalmoscopy loupe from the eye. Furthermore, the optimal distance can be maintained within the framework of a control system. Setting and / or maintaining the optimal distance ensures that image quality is not compromised due to an incorrectly adjusted distance.

[0017] Further features, properties and advantages of the present invention will become apparent from the following description of embodiments with reference to the accompanying figures. Fig. 1 shows the structure of a surgical microscope with an optical view in a schematic representation. Fig. Figure 2 shows schematically the basic structure of a varioscope lens. Fig. 3 shows a digital surgical microscope in a schematic representation. Fig. 4 shows a surgical microscope with fundus imaging system. Fig. 5 shows the optical components of the surgical microscope and the fundus imaging system from Fig. 4. Fig. 6 shows the optical components of Fig. 5 with an additional OCT section.

[0018] The following is based on the Fig. 1 the basic structure of the surgical microscope 2 is explained.

[0019] The Fig. The surgical microscope 2 shown in Figure 1 comprises, as essential components, an objective lens 5 directed toward an object field 3, which can be configured, in particular, as an achromatic or apochromatic objective lens. In the present exemplary embodiment, the objective lens 5 consists of two cemented-together partial lenses that form an achromatic objective lens. The object field 3 is arranged in the focal plane of the objective lens 5, so that it is imaged by the objective lens 5 toward infinity. In other words, a divergent beam 7 emanating from the object field 3 is converted into a parallel beam 9 as it passes through the objective lens 5.

[0020] On the observer side of the objective 5, a magnification changer 11 is arranged, which can be designed either as a zoom system for continuously changing the magnification factor, as in the illustrated embodiment, or as a so-called Galilean changer for stepwise changing the magnification factor. In a zoom system consisting, for example, of a lens combination with three lenses, the two object-side lenses can be moved to vary the magnification factor. In reality, however, the zoom system can also have more than three lenses, for example four or more lenses, in which case the outer lenses can also be fixedly arranged. In a Galilean changer, on the other hand, there are several fixed lens combinations that represent different magnification factors and can be alternately inserted into the beam path.Both a zoom system and a Galilean changer convert a parallel beam of rays on the object side into a parallel beam of rays on the observer side with a different beam diameter. In the present embodiment, the magnification changer 11 is already part of the binocular beam path of the surgical microscope 1, i.e., it has a separate lens combination for each stereoscopic partial beam path 9A, 9B of the surgical microscope 1. In the present embodiment, the magnification factor is set by means of the magnification changer 11 via a motor-driven actuator, which, together with the magnification changer 11, is part of a magnification change unit for setting the magnification factor.

[0021] In the present example, an interface arrangement 13A, 13B is connected to the magnification changer 11 on the observer side. This interface arrangement can be used to connect external devices to the surgical microscope 1 and, in the present embodiment, includes beam splitter prisms 15A, 15B. However, other types of beam splitters can also be used, for example, semi-transparent mirrors. In the present embodiment, the interfaces 13A, 13B serve to decouple a beam of rays from the beam path of the surgical microscope 2 (beam splitter prism 15B) or to couple a beam of rays into the beam path of the surgical microscope 2 (beam splitter prism 15A).

[0022] In the present embodiment, the beam splitter prism 15A in the partial beam path 9A serves to reflect information or data for a viewer into the partial beam path 9A of the surgical microscope 1 via the beam splitter prism 15A with the aid of a display 37, e.g., a digital mirror device (DMD) or an LCD display, and associated optics 39. In the other partial beam path 9B, a camera adapter 19 with a camera 21 attached thereto is arranged at the interface 13B. The camera adapter 19 is equipped with an electronic image sensor 23, e.g., a CCD sensor or a CMOS sensor. An electronic and, in particular, a digital image of the tissue region 3 can be recorded by means of the camera 21. A hyperspectral sensor, in particular, can also be used as the image sensor, in which not only three spectral channels (e.g., red, green, and blue) are present, but rather a plurality of spectral channels.

[0023] In the present example, a binocular tube 27 is connected to the interface 13 on the observer side. This tube has two tube lenses 29A, 29B, which focus the respective parallel beams 9A, 9B onto an intermediate image plane 31, thus imaging the object under observation 3 onto the respective intermediate image plane 31A, 31B. The intermediate images located in the intermediate image planes 31A, 31B are then imaged to infinity by eyepiece lenses 35A, 35B, so that an observer can view the intermediate image with a relaxed eye. Furthermore, the distance between the two partial beams 9A, 9B is increased in the binocular tube by means of a mirror system or prisms 33A, 33B in order to adapt it to the observer's interpupillary distance. The mirror system or prisms 33A, 33B also erect the image.

[0024] The surgical microscope 2 is also equipped with an illumination device with which the object field 3 can be illuminated with broadband illumination light. For this purpose, the illumination device in the present example comprises a white light source 41, such as a halogen lamp or a gas discharge lamp. The light emitted by the white light source 41 is directed toward the object field 3 via a deflecting mirror 43 or a deflecting prism in order to illuminate it. The illumination device also includes an illumination optics 45, which ensures uniform illumination of the entire observed object field 3.

[0025] It should be noted that the Fig. 1 is highly schematic and does not necessarily reflect the actual course of the illumination beam path. In principle, the illumination beam path can be designed as so-called oblique illumination, which corresponds to the schematic representation in Fig. 1. In such an oblique illumination, the beam path runs at a relatively large angle (6° or more) to the optical axis of the lens 5 and can, as in Fig. 1, run completely outside the lens. Alternatively, however, it is also possible to have the illumination beam path of the oblique illumination run through an edge region of the lens 5. Another possible arrangement for the illumination beam path is the so-called 0° illumination, in which the illumination beam path runs through the lens 5 and is coupled into the lens between the two partial beam paths 9A, 9B along the optical axis of the lens 5 in the direction of the object field 3. Finally, it is also possible to implement the illumination beam path as so-called coaxial illumination, in which a first and a second partial illumination beam path are present.The illumination partial beam paths are coupled into the surgical microscope via one or more beam splitters parallel to the optical axes of the observation partial beam paths 9A, 9B, so that the illumination runs coaxially to the two observation partial beam paths.

[0026] In the Fig. In the embodiment of the surgical microscope 2 shown in Figure 1, the objective lens 5 consists solely of a fixed-focal-length achromatic lens. However, an objective lens system comprising multiple lenses can also be used, in particular a so-called varioscope objective lens, with which the working distance of the surgical microscope 2, i.e., the distance of the object-side focal plane from the vertex of the first object-side lens surface of the objective lens 5, also called the object back focal length, can be varied. The object field 3 arranged in the focal plane is also imaged toward infinity by the varioscope objective lens 50, so that a parallel beam of rays is present on the observer side.

[0027] An example of a varioscope lens is shown schematically in Fig. 2. The varioscope lens 50 comprises a positive element 51, i.e. an optical element with positive refractive power, which Fig. 2 is schematically shown as a convex lens. In addition, the varioscope lens 50 comprises a negative element 52, i.e. an optical element with negative refractive power, which Fig. 2 is shown schematically as a concave lens. The negative element 52 is located between the positive element 51 and the object field 3. In the varioscope lens 50 shown, the negative element 52 is fixed, whereas the positive element 51 is arranged to be displaceable along the optical axis OA as indicated by the double arrow 53. When the positive element 51 is moved into the Fig. 2 is moved, the focal length is extended, so that the working distance of the surgical microscope 2 from the object field 3 changes.

[0028] Although in Fig. 2, the positive element 51 is designed to be movable, it is also possible in principle to arrange the negative element 52 instead of the positive element 51 so that it can be moved along the optical axis OA. However, the negative element 52 often forms the end lens of the varioscope objective 50. A fixed negative element 52 therefore offers the advantage that the interior of the surgical microscope 2 can be more easily sealed against external influences. Furthermore, it should be noted that, although the positive element 51 and the negative element 52 in Fig. 2 are shown only as individual lenses, each of these elements can be realized in the form of a lens group or a cemented element instead of in the form of an individual lens, for example in order to make the varioscope lens achromatic or apochromatic.

[0029] Fig. Figure 3 shows an example of a digital surgical microscope 48 in a schematic representation. In this surgical microscope, the main objective 5, the magnification changer 11 and the illumination system 41, 43, 45 do not differ from the one shown in Fig. 1 shown surgical microscope 2 with optical view. The difference is that the Fig. 3 does not include an optical binocular tube. Instead of the tube lenses 29A, 29B from Fig. 1 comprises the surgical microscope 48 from Fig. 3 focusing lenses 49A, 49B with which the binocular observation beam paths 9A, 9B are imaged onto digital image sensors 61A, 61B. The digital image sensors 61A, 61B can be, for example, CCD sensors or CMOS sensors. The images captured by the image sensors 61A, 61B are digitally sent to digital displays 63A, 63B, which can be designed as LED displays, LCD displays, or displays based on organic light-emitting diodes (OLEDs). As in the present example, the displays 63A, 63B can be assigned eyepiece lenses 65A, 65B, with which the images shown on the displays 63A, 63B are imaged to infinity, so that a viewer can view them with relaxed eyes. The displays 63A, 63B and the eyepiece lenses 65A, 65B can be part of a digital binocular tube, but they can also be part of a head-mounted display (HMD) such as data glasses.

[0030] Although in Fig. 3 as in Fig. 1 only shows an achromatic lens 5 with a fixed focal length, this can be Fig. 3 shown surgical microscope 48 like the one in Fig. 1, the surgical microscope 2 may comprise a varioscope lens instead of the objective lens 5. Furthermore, Fig. 3 shows a transmission of the images captured by the image sensors 61A, 61B to the displays 63A, 63B via cables 67A, 67B. However, instead of wired, the images can also be transmitted wirelessly to the displays 63A, 63B, especially if the displays 63A, 63B are part of a head-mounted display.

[0031] Fig. 4 shows a surgical microscope 2, 48 on which a fundus imaging system 71 is arranged. The surgical microscope 2, 48 can be designed as a surgical microscope 2 with optical viewing or as a surgical microscope 48 with digital viewing.

[0032] The fundus imaging system comprises an ophthalmoscopy magnifying glass 73, with which the fundus 75 of an eye 77 is imaged into an intermediate image plane 79. The fundus imaging system 71 further comprises an optical group 81, which is arranged between the intermediate image plane 79 and the main objective 5 of the surgical microscope. In the present exemplary embodiment, the distance of the optical group 81 from the main objective 5 is greater than the distance of the optical group 81 from the intermediate image plane 79, so that the optical group 81 is positioned closer to the intermediate image 79 than to the main objective 5. The distance of the optical group 81 from the main objective 5 can in particular correspond to at least 1.5 times and preferably at least 2.5 times the distance of the optical group 81 from the intermediate image plane 79.

[0033] The fundus imaging system 71 is attached to the surgical microscope 2, 48 by means of a fastening system. In the present exemplary embodiment, this comprises a fixing element 83 for fixing the fundus imaging system 71 to the main body 85 of the surgical microscope 2, 48, as well as a pivoting system 87 for pivoting the ophthalmoscopy magnifying glass 73 and the optics group 81 into the observation beam path between the eye 77 and the main objective 5. In the present exemplary embodiment, the pivoting system comprises a shaft 89 or a shaft-like structure that can be rotated about a rotation axis RA by means of a motor 82 arranged in the fixing element 83. By means of the rotation, the ophthalmoscopy magnifying glass 73 or the optics group 81, which are attached to the shaft 89 by means of an ophthalmoscopy magnifying glass holder 91 and an optics group holder 93, can be pivoted into or out of the observation beam path. The pivoting process is Fig. 4 by the double arrow 95. Furthermore, the fixation 83 in the present embodiment comprises a further motor 86, with which the shaft or shaft-like structure 89 can be moved along the optical axis RA in order to position the ophthalmoscopy magnifier 73 such that a suitably focused intermediate image is produced. The movement of the shaft or shaft-like structure 89 with the ophthalmoscopy magnifier 73 attached thereto and the optics group 81, which is also attached to the shaft or shaft-like structure 89, is shown in Fig. 4 indicated by the double arrow 97.

[0034] The main lens of the Fig. The surgical microscope 2, 48 shown in Figure 4 has a focal length reduced by a factor of 1.5 to 2 compared to a standard main objective. With a usual focal length of 200 mm for the main objective 5, the surgical microscope 2, 48 made of Fig. 4 thus has a focal length in the range between 100 mm and approximately 135 mm. If the main lens 5 is a varioscope lens, its focal length can be varied between 100 mm and 135 mm. In variants other than the one shown, the focal length can be in the range between 100 mm and 150 mm or even between 90 and 160 mm.

[0035] By reducing the focal length of the main objective 5, the entrance pupil, i.e. the object-side image of the aperture diaphragm or of the optical element of the surgical microscope 2, 48 acting as an aperture diaphragm, increases by the same factor by which the focal length has been reduced compared to the usual focal values. Thus, with a focal length reduction by a factor of 2, the diameter of the entrance pupil also increases by a factor of 2, and with a focal length reduction by a factor of 1.5, the diameter of the entrance pupil increases by a factor of 1.5. Since, when using the surgical microscope 2, 48 equipped with the fundus imaging system 71, the entrance pupil is located in the area of ​​the eye pupil 99, and the eye pupil 99 represents the first lens for the optical system for imaging the fundus 75, the numerical aperture of the beam entering the eye lens 99 determines the resolution of the system.Increasing the pupil diameter increases the numerical aperture, which is associated with increased resolution. By reducing the focal length of the main objective 5 of the surgical microscope 2.48 and the resulting increase in the diameter of the entrance pupil, the resolution of the fundus image is improved to such an extent that, when viewing the fundus at magnification, the diffraction limit of the system is not reached as quickly as when using a surgical microscope with a main objective 5 with the standard focal length.

[0036] By enlarging the entrance pupil, the diameter of the beam passing through the ophthalmoscopy magnifier 73 also increases. However, the ophthalmoscopy magnifier 73 is often made of only a single glass material (mineral or organic), so that its image is subject to a corresponding error. This results in longitudinal chromatic aberration and transverse chromatic aberration. With the enlargement of the entrance pupil and the associated enlargement of the beam entering the ophthalmoscopy magnifier 73, the longitudinal chromatic aberration increases, which also leads to an increase in the transverse chromatic aberration. The increased longitudinal chromatic aberration and, in particular, the increased transverse chromatic aberration degrade the image quality and thus negate part of the image quality gained through the increased resolution.The optical group 81 serves to compensate for the increased chromatic aberration, in particular the increased transverse chromatic aberration. For this purpose, it is advantageous if the optical group 81 is arranged near the intermediate image plane 79, as in the present embodiment, but not in the intermediate image plane 79. In this way, the diameter of the optical group can be kept small, which, on the one hand, reduces manufacturing costs and, on the other hand, helps prevent the introduction of further aberrations.

[0037] Fig. 5 shows the optical components of a specific embodiment of a digital surgical microscope 48 with a fundus imaging system 71 according to the invention. In this specific embodiment, the surgical microscope itself comprises only the main objective 5 and a camera objective, which serves as a focusing lens 49 for focusing the beam path onto the digital image sensor 61. A magnification changer is not included in this example. Instead, in the present embodiment, digital magnification of the digital image can be easily achieved due to the increased resolution. In this embodiment, the main objective 5 is designed as an apochromatic lens with a cemented element and a single lens to ensure color purity of the main objective. In the present embodiment, the camera objective is designed with two lenses, with each of the lenses consisting of a two-part cemented element.The optics group 81 of the fundus imaging system is also designed as a cemented element, and the ophthalmoscopy magnifier 29 is a rotationally symmetrical aspheric single lens in which the aspheric surface faces away from the eye 77. Also in . Fig. 5 shows the entrance pupil 103, which, as already mentioned, represents the object-side image of the aperture diaphragm 105, which in the present embodiment is designed as a physical diaphragm. The optics group 81 serves only to correct the imaging errors and not to change the aperture of the observation beam passing through it.

[0038] The optical parameters of the Fig. The areas F1 to F18 shown in Figure 5 are summarized in the table below. Oberfläche Radius[mm] Dicke[mm] Öffnungs-radius[mm] Glass Brechzahlbeiλ = 546,074 nm Abbe-Zahlbeiλ = 546,074 nm F1 inf 66,35 5 AIR F2 -11,8 2 6 N-LAK8 1,71616 53,61 F3 -14,2 3,1 8 S-FPL51 1,49845 81,51 F4 -14,2 7,97 8 AIR F5 220 1,8 8 N-KZFS4 1,61664 44,27 F6 34,43 4 8 S-FPL51 1,49845 81,51 F7 -40 2 8 AIR F8 182,3 4 20 S-FPL51 1,49845 81,51 F9 -182,3 0,2 20 AIR F10 67 6 20 S-FPL51 1,49845 81,51 F11 -200 3 20 S-NBH8 1,72538 34,47 F12 200 99,635833 20 AIR F13 -22 2,5 10 N-SK5 1,59142 61 F14 19 7,5 10 N-SF1 1,72308 29,39 F15 -22 5,824031 10 AIR F16 inf 7,9 7 AIR F17 7,311244 7 8 N-SK5 1,59142 61 F18 -20,097 5,848164 8 AIR

[0039] The surface F17 is a rotationally symmetric aspherical surface with the following coefficients: CC 0 AS2 -1,94E-04 AS3 4,50E-07 AS4 -1,35E-08 AS5 9,02E-11

[0040] To ensure the optical quality of the fundus image, the distance between the patient's eye and the optics should be maintained at an optimal level. For this purpose, the surgical microscope according to the invention, in an advantageous development, has an OCT path with which very precise distance determination is possible. This OCT path includes, among other things, the main objective 5, the optics group 81 and the ophthalmoscopy magnifier 73, which are shared with the observation beam path. In addition, the OCT path includes the exit end of an optical fiber 107 as a light source, a collimator optic 109, a scanning mirror 111, a beam expander optic 113 and a deflection mirror 115. White light emerges from the exit end of the optical fiber 107, which is generated by a white light source (not shown) and guided by the optical fiber to the OCT path.The collimator optics 109 forms a parallel (collimated) beam from the divergent beam emerging from the exit end of the optical fiber 107, which is subsequently expanded by the beam expander optics 113 and deflected by the deflection mirror 115 in the direction of the main objective 5. The main objective then focuses the beam onto the intermediate image plane 79. The scanning mirror 111, arranged between the collimator optics 109 and the beam expander optics 113, can be used to shift the position of the focal point in the intermediate image plane 79. In the present embodiment, the scanning mirror 111 is designed as a MEMS mirror, i.e., a mirror that can be rotated about an axis located in the mirror plane by means of an MEMS oscillator (MEMS: Micro Electro-Mechanical System).If two-dimensional scanning is to be realized, a second MEMS oscillator can be installed, allowing the scanning mirror to rotate around a second rotation axis, also located within the mirror plane. The two rotation axes are not parallel and preferably extend at an angle of 90° to each other.

[0041] The OCT path can be used to regulate the distance of the optics from the fundus with a control unit 84 (cf. Fig. 4), which adjusts this distance to the optimal distance using motor 86 in the fixing element. This ensures consistently good image quality.

[0042] In contrast to the Fig. The OCT path shown in Figure 6 can be provided with optical elements that can be moved along the optical axis of the path in order to be able to vary the focal length of the path.

[0043] In addition to maintaining the optimal distance for fundus imaging, the OCT path can also be used intraoperatively to generate depth information of the fundus structures under consideration.

[0044] A surgical microscope 2, 48 according to the invention with a fundus imaging system 71, as described with reference to the exemplary embodiments, can be used, for example, in the context of a retinal operation. During preparation for the operation, the system can then be focused on a plane in the region of the anterior segment of the patient's eye 77 instead of on the fundus 75 by removing (in the present exemplary embodiment by pivoting out) the ophthalmoscopy magnifying glass 73 and the intermediate image optics group 81 from the beam path. The main objective 5 is then focused on the anterior segment of the eye 77. If the main objective 5 is a varioscope objective, focusing can be achieved by means of internal focusing, i.e., focusing is achieved by moving the lenses of the varioscope objective relative to one another. If the objective is a fixed focal length objective, focusing can be achieved by means of external focusing, i.e.,the entire surgical microscope 2, 48 is moved along the optical axis of the main objective 5 for focusing.

[0045] In the described embodiments of the surgical microscope 2, 48 with fundus imaging system 71, only one ophthalmoscopy magnifier 73 was present in each case. However, it can sometimes be advantageous to be able to switch between ophthalmoscopy magnifiers with different properties. For this purpose, the fundus imaging system 71 can comprise at least two ophthalmoscopy magnifiers that can be interchanged. In this case, the holder 91 for the ophthalmoscopy magnifier is equipped with an interchangeable mechanism that allows the existing ophthalmoscopy magnifiers to be interchanged.

[0046] The surgical microscope according to the invention enables high-quality imaging of the fundus. The improved image quality is primarily due to the improved resolution achieved by enlarging the entrance pupil. Furthermore, the correction of chromatic aberration, particularly transverse chromatic aberration, using the near-intermediate optical group makes an important contribution to ensuring high image quality. The OCT path can also be helpful in ensuring high image quality, as it allows the distance to the observed structure to be precisely determined, thus facilitating the setting and, if necessary, maintenance of the exact focus distance.

[0047] The present invention has been described in detail using exemplary embodiments for illustrative purposes. However, a person skilled in the art will recognize that deviations from the described exemplary embodiments are possible. Some possible deviations have already been indicated in the exemplary embodiments. However, further deviations are possible. For example, a sterile (often plane-parallel) optically transparent element (often made of plastic) can be present between the eye pupil 99 and the ophthalmoscopy magnifier 73. This element can be, for example, a sterile cover glass of a drape. The sterile optically transparent element can be composed of one or more optical elements and can have no refractive power or a refractive power other than zero. It can, for example, be attached to the holder 91 for the ophthalmoscopy magnifier.Furthermore, it is possible to provide a device for digitally magnifying the digital image of the fundus to make details more visible. The present invention is therefore not intended to be limited to the specific embodiments, but solely by the appended claims. List of reference symbols 49A,B Focusing lens 61A,B digital image sensor 63A,B digital display 65A,B eyepiece lens 67A,B cable 71 Fundus imaging system 73 Ophthalmoscopy magnifier 75 Fundus 77 Eye 79 Intermediate image plane 81 Optics group 82 engine 83 Fixing element 84 Control unit 85 main body 86 engine 87 Swivel system 89 Wave 91 Bracket 93 Bracket 95 Double Arrow 97 Double arrow 99 Eye pupil 101 Digital 103 Entrance pupil 105 aperture diaphragm 107 optical fiber 109 Collimator optics 111 Scanning mirror 113 Beam expander optics 115 deflection mirrors 117 MEMS oscillator RA rotation axis

Claims

[1] Surgical microscope (2, 48) for viewing an eye (77) with a main objective (5) and a fundus imaging system (71) positionable in the beam path (7) between the eye (77) and the main objective (5), which comprises an ophthalmoscopy magnifying glass (73), characterized by that the main objective (5) has a focal length in the range between 90 mm and 160 mm and the fundus imaging system (71) comprises an optical group (81) whose dispersion properties are adapted to the dispersion properties of the ophthalmoscopy magnifier (73) in such a way that the optical group (81) compensates for a chromatic aberration of the ophthalmoscopy magnifier (73). [2] Surgical microscope (2, 48) according to claim 1, characterized by that the ophthalmoscopy magnifier (73) forms an intermediate image in an intermediate image plane (79) located between the ophthalmoscopy magnifier (73) and the main objective (5) and the optical group (81) is arranged between the intermediate image plane (79) and the main objective (5). [3] Surgical microscope (2, 48) according to claim 2, characterized by that the optical group (18) is arranged closer to the intermediate image plane (79) than to the main objective (5). [4] Surgical microscope (2, 48) according to claim 3, characterized by that the distance of the optical group (81) from the main objective (5) corresponds to at least one and a half times the distance of the optical group (81) from the intermediate image plane (79). [5] Surgical microscope (2, 48) according to one of claims 1 to 4, characterized by that the main lens (5) is a varioscope lens (50) whose focal length can be varied between 90 mm and 160 mm. [6] Surgical microscope (2, 48) according to claim 5, characterized by that the fundus imaging system (71) comprises at least two interchangeable ophthalmoscopy magnifiers. [7] Surgical microscope (2, 48) according to one of claims 1 to 6, characterized bythat it is designed as a digital surgical microscope (48) with at least one digital image sensor (61). [8] Surgical microscope (2, 48) according to claim 7, characterized by a software or hardware module for digitally magnifying the image captured by the image sensor (61). [9] Surgical microscope (2, 48) according to one of claims 1 to 8, characterized by that it includes an OCT section. [10] Surgical microscope (2, 48) according to one of claims 1 to 9, characterized by that the fundus imaging system (71) comprises a distance adjustment system for adjusting the distance of the ophthalmoscopy magnifier (73) from the eye (77). [11] Surgical microscope (2, 48) according to claim 9 and claim 10, characterized byin that the distance adjustment system comprises a motor (86) for motor-controlled adjustment of the distance of the ophthalmoscopy magnifying glass (73) from the eye (77) and a control unit (84) connected to the OCT path and the motor (86), which control unit is designed to determine the distance of the surgical microscope (2, 48) from the fundus (75) from an OCT signal obtained with the aid of the OCT path and to adjust the distance of the ophthalmoscopy magnifying glass (73) from the eye on the basis of the determined distance of the surgical microscope (2, 48) from the fundus (75).

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