Lighting system, specific use of a lighting system, illumination method and observation system

Abstract

Lighting system (1) for adaptively illuminating an object (7) located in an object plane (8) with a lighting beam path (6), wherein the lighting system (1) is intended for use with an imaging system (18) and wherein the lighting system (1) comprises: - a light source (2) as the starting point of the illumination beam path (6), - a collector optic (3) for collecting light rays emanating from the light source (2), and - a condensation optic (4) for illuminating the object plane (8), characterized in that the condensation optic (4) comprises two microlens arrays (5a, 5b), - wherein their axial distance (23) to each other is adjustable along an optical axis (21) by means of an adjustment means (11) in the form of an electronically controllable actuator (16) and / or - wherein at least one of the two microlens arrays (5a, 5b) is designed to be optically tunable.

Description

[0001] The invention relates to a lighting system designed for the adaptive illumination of an object located in an object plane. The lighting system can be used in conjunction with an imaging system and / or be integrated into an imaging system. The lighting system comprises, or forms, an illumination beam path and includes: a light source as the starting point of the illumination beam path; a collector optic for collecting light rays emanating from the light source; and a condensation optic for illuminating the object plane.

[0002] The invention further relates to a specific use of such a lighting system for illuminating an object plane that is observed simultaneously with an imaging visualization system.

[0003] The invention also relates to a method for illuminating a cavity, such as a body cavity, without shadowing, wherein the cavity is observed with a visualization system and wherein illumination light emanating from a light source is first collimated at least approximately by means of a collector optic.

[0004] Finally, the invention relates to an observation system, which is particularly suitable for medical applications, and which comprises an illumination system according to the invention as well as an imaging visualization system which offers a variable optical zoom.

[0005] In the prior art, such lighting systems are already used in medical procedures to illuminate an object field which is observed by a surgeon with a video camera and appropriate imaging optics.

[0006] The scientific article “Super-resolution imaging of multiple cells by optimised flat-field epi-illumination” by DOUGLAS KM [et al.], published in Nat Photonics, Vol. 10, 2016, No. 11, pp. 705–708. – ISSN 1749-4893, describes an illumination system comprising two microlens arrays arranged at a fixed distance corresponding to the focal length of the microlenses in each array. The size of the illumination field can be initially preset, albeit relatively coarsely.

[0007] The further article “Design of zoom homogenizer to control size of illumination field” by KIM, T. [et al.], published in: Opt. Eng., Vol. 57, 2018, No. 3, pp. 1-5. - ISSN 0091-3286, describes an illumination system called a “zoom homogenizer” which has three microlens arrays, whereby the size of the illuminated illumination field can be adjusted by changing the distance between the microlens arrays.

[0008] Based on this technical background, the invention aims to enable improved handling and performance of the overall system, particularly in such applications. Specifically, it seeks to provide a highly compact, lightweight, and energy-efficient lighting system for such applications, which can be freely moved in space on a robot arm together with the imaging system.

[0009] To solve this problem, the features of claim 1 are provided according to the invention for a lighting system. In particular, it is thus proposed according to the invention, to solve the problem in a lighting system of the type mentioned at the outset, that the condensation optics comprise two microlens arrays.

[0010] Furthermore, it is provided that the axial distance between the two microlens arrays is adjustable along an optical axis by means of an adjustment device in the form of an electronically controllable actuator. Alternatively or additionally to the aforementioned feature, it may also be provided that at least one of the two microlens arrays is optically tunable.

[0011] In other words, according to the invention, variable adjustment / adaptation of an illumination field lit by the lighting system can be achieved by adjusting the axial distance between the two microlens arrays of the condensation optics and / or by optically detuning at least one of the two microlens arrays. The use of microlens arrays results in an extremely compact design and also offers numerous other technical advantages, which will be explained in more detail below.

[0012] According to the invention, the problem can also be solved by further advantageous embodiments according to the dependent claims.

[0013] For example, the optical focal length of the condensation optics can be tuned by adjusting the axial distance between the two microlens arrays or by detuning at least one of the two microlens arrays.

[0014] The illumination system can further be designed such that the size of an illumination field (of the aforementioned) in the object plane, which is supplied with illumination light by the condensation optics, can be adjusted by i) changing the axial distance between the two microlens arrays and / or by ii) detuning at least one of the two microlens arrays. Such an adjustment can, for example, be made while maintaining a constant working distance between the object plane and the condensation optics; however, the adjustment can also be made in response to an adjustment of the working distance.

[0015] By adjusting the focal length of the condensation optics, for example by changing the axial distance, it is possible to create a kind of zoom effect with respect to the size of the illumination field lit by the condensation optics. Such an adjustment of the illumination field size by changing the focal length of the condensation optics (achieved by moving one of the microlens arrays along the optical axis) can be particularly advantageous if the working distance has changed and, for example, the associated visualization system is adjusted to a different focus distance (= adjustment of the focus of the imaging system).

[0016] The lighting system can also include a field diaphragm inserted into the illumination beam path, for example, arranged between the collector optics and the condenser optics, or in the illumination beam path after the condenser optics or before the collector optics. This field diaphragm is preferably arranged such that its aperture is always completely illuminated by the illumination beam path. In such a case, the field diaphragm can thus block a portion of the light rays emanating from the collector optics. Preferably, however, only a minimal portion of the illumination beam path is blocked, so that virtually all of the light from the light source actually reaches the object plane.

[0017] The condensation optics can thus be configured to project an image of the field diaphragm at different magnifications onto the object plane (which in this application typically remains at the same working distance). This creates a sharp image of the field diaphragm in the object plane, with this image defining, i.e., specifying, the illumination field.

[0018] In this case, the light source can preferably be arranged relative to the collector optics such that the collector optics image the light source to infinity. This allows for the realization of so-called Köhler illumination with the lighting system, whereby the light source no longer interferes with the imaging in the object plane.

[0019] The adjustment of the illumination field size can preferably be designed such that the aspect ratio (height to width) of the illumination field remains constant and / or without requiring any change in aperture size. This can be achieved, for example, if the condensation optics project a fixed field aperture with a fixed aspect ratio onto the object plane at different magnifications, depending on the degree of adjustment of the condensation optics. Such a design of the illumination system allows for the implementation of variable or adaptive Köhler illumination, particularly without the use of a variable field aperture. This type of illumination makes it possible to adjust the axial position and / or size of the illuminated field by adjusting the condensation optics.

[0020] The distance between the object plane and the condensation optics, in particular the rear microlens array, can be understood here as a working distance of the illumination system. If this working distance is kept constant when using the illumination system, the size of the illumination field can be adjusted, in particular without changing the position and / or size of a field diaphragm, namely by moving one of the two microlens arrays.

[0021] In its simplest form, the collector optics can be formed by a single fixed optical lens, particularly an aspherical or plano-convex lens. However, the collector optics can also be more complex and then, for example, comprise several optical lenses, especially two plano-convex lenses.

[0022] The invention offers the advantage of more efficient light utilization, allowing for a reduction in the light output and thus the electrical power consumption of the light source. Furthermore, this enables better adaptation of the individual components to the lower power range. The increased efficiency also leads to lower power losses and therefore less heating of the lighting system, particularly at light coupling points. Since the light source can be designed with lower power, a lower safety class can be maintained, especially at the coupling points of a light guide used as the light source of the lighting system, which supplies light from a primary light source to the collector optics. This offers advantages for the user.

[0023] According to an advantageous embodiment, the two microlens arrays can shape an incident beam from the illumination beam path into an outgoing beam, resulting in a rectangular illumination field, preferably with an aspect ratio of 16:9. The light source can provide a non-rectangular, for example, approximately rotationally symmetric, intensity distribution, which is the case for many conventional light sources. In other words, the beam emitted by the two microlens arrays can thus have a rectangular beam cross-section.

[0024] A significant advantage of the invention lies in the fact that the two microlens arrays can optically homogenize the intensity distribution within the rectangular illumination field, compared to the (original) intensity distribution of the light source of the illumination system. The two microlens arrays thus perform the optical functions of beam homogenization and beam shaping with respect to the illumination beam path emanating from the condensation optics.

[0025] It can be particularly advantageous if both microlens arrays have microlenses on both sides (i.e., on their respective front and back sides).

[0026] The two microlens arrays can each, for example, have microlenses on their front and / or rear sides that have a rectangular shape and / or a rectangular optical aperture. Furthermore, configurations are possible in which the microlenses of the two microlens arrays are arranged in a periodic pattern. This allows a flat-top intensity profile with a ripple of less than 15% to be achieved in the illumination field.

[0027] Furthermore, at least one of the two microlens arrays can have microlenses with an aspherical contour.

[0028] For example, it may also be provided that at least one of the two microlens arrays has cylindrical lenses. In this case, at least one of the two microlens arrays can have cylindrical lenses on both sides, with one orientation of these cylindrical lenses being rotated by 90° between a front and a back surface. Alternatively or additionally, the cylindrical lenses of one microlens array can also be rotated by 90° relative to the cylindrical lenses of the other microlens array.

[0029] Such designs make it possible to achieve a beam transformation from a circular to a rectangular illumination pattern. This requires deflecting the originally circular beam of light by different amounts along two perpendicular axes. This can be achieved by using microlenses with different radii of curvature, although these do not necessarily have to be designed differently; for example, a rectangular illumination pattern can also be achieved simply by rotating the front and rear microlenses by 90° as described above.

[0030] The radii of curvature of the microlenses do not necessarily have to be different. Rather, the rectangular illumination shape can be achieved by rotating the lenses of the two microlens arrays or by rotating the front and rear lenses of one of the two microlens arrays relative to each other, as already mentioned above.

[0031] The two microlens arrays (MLAs) can also be made of fused silica to enable illumination across a broad wavelength range, extending into the UV region. However, MLAs can be manufactured from a wide variety of materials. Glass pressing can also be used for their production, in which case glasses with low melting points are preferable.

[0032] As mentioned at the outset, the illumination system includes an adjustment device with which the axial distance between the two microlens arrays can be adjusted. While such an adjustment device could also be manual, the embodiment according to the invention, in which the adjustment device is designed as an electronically controlled actuator, is particularly advantageous for demanding applications where frequent and rapid adjustment of the illumination field is required. Such an actuator can be implemented, for example, with a motor, in particular a stepper motor, or a driven cam disk / cam tube, by means of an electromagnetic drive, or by means of a linear drive. With such electronic solutions, the size of the illumination field can be adjusted very quickly depending on the current size of the field of view of the imaging system.This ability to quickly adjust the lighting field to the size of the field of view depending on the situation is a key aspect of the present invention.

[0033] In particular, the illumination system can be designed to automatically adjust the size of the illumination field in response to a change in the size of the field of view of the imaging system. For this purpose, the illumination system can have an (electronic) controller that, in response to an input signal (which can be provided by the illumination system or by a user), adjusts the size of the illumination field (namely, by changing the axial distance between the two microlens arrays). The controller can achieve this by actuating the adjustment mechanism of the condensation optics. As mentioned, in such a case, the adjustment mechanism can include an actuator, preferably electronically controlled and / or electrically designed, with which the desired change in the distance between the two microlens arrays (i.e.,The actuator can effect at least a displacement of at least one of the two microlens arrays. Alternatively, it can also be designed to detune at least one of the two microlens arrays.

[0034] Such designs make it particularly effective to ensure that the size of the illumination field can be adjusted quickly and precisely at a specific, especially fixed, working distance. The illumination system can preferably be designed (by appropriately dimensioning lenses, apertures, and positioning these elements along the illumination beam path) so that, across the entire adjustment range of the condensation optics, almost all of the illumination light incident on the front of the two microlens arrays can be used to illuminate the illumination field.

[0035] Unlike previous systems, where the size of the illumination field is reduced by stronger glare reduction, i.e., by decreasing the aperture of a field diaphragm, this solution according to the invention reduces losses in the illumination beam path, so that almost all the light can be used to illuminate the field of view. Thus, almost the entire amount of light is always available to illuminate the field, regardless of the current adjustment of the condensation optics and therefore independent of the size of the illumination field. Consequently, hardly any illumination light is lost, and excessive heating of the illumination system during operation can be avoided, since the light rays emanating from the collector optics are used almost entirely for illumination and therefore do not need to be significantly glare-free.As a result, this leads to an increase in efficiency and, accordingly, the total required light output of the lighting system can be reduced.

[0036] It can therefore be provided that, in at least two different adjustments of the condensation optics, a quantity of light supplied by the light source in the illumination beam path, which exits the collector optics, completely passes through the two microlens arrays and / or is completely available for illuminating the illumination field. It is understood that unavoidable light losses, such as those due to scattering by particles, etc., are neglected in this consideration.

[0037] It is therefore possible to design the condensation optics so that the size of the illumination field can be adjusted within a certain range, without changing the amount of light energy incident on that field. The adjusted size of the illumination field will then result in a correspondingly adjusted intensity / irradiance. Such a design can be achieved by appropriately sizing the collector and condensation optics.

[0038] Therefore, it can also be provided that an entire beam of light emitted by the collector optics emerges from the rear of the two microlens arrays as a shaped beam of light in all adjustable relative positions of the two microlens arrays.

[0039] If the total amount of light falling on the illumination area is to be reduced, this can be achieved by reducing the amount of light emitted by the light source, i.e., the luminous flux of the light source can be reduced accordingly. Therefore, it is also preferred if the light source of the lighting system is designed to have electrically adjustable luminous flux.

[0040] The light source mentioned so far can also be formed by the end face of an optical fiber. In such a configuration, the collector optics can be operated directly on the optical fiber. In this case, only the optical fiber needs to be supplied with light from a suitable primary light source for the lighting system to function. The optical fiber and the corresponding light coupling into it can preferably be selected such that the end face emits light with a maximum beam angle of less than 40°, preferably less than 20°. This makes it possible to keep the diameter of the first collector lens, and thus also the subsequent components of the lighting system, small, and therefore the entire system extremely compact. This is particularly advantageous if the system is to be moved in space by a robotic arm.The aforementioned light guide can, for example, be formed using a bundle of light guides.

[0041] To solve the problem, the features of the dependent use claim are also provided; this proposes a specific use of a lighting system as described above, which is, of course, preferably designed according to the invention. In this use, it is provided that, in response to i) an adjustment of an optical zoom, particularly with a constant working distance between the object plane and the condensation optics, and / or ii) an adjustment of a spatial position of a focal plane of the visualization system (with which the said lighting system is used), the size of the illumination field in the object plane (which is illuminated by the lighting system) is adjusted by adjusting the condensation optics.For this purpose, the condensation optics can be detuned, for example, and / or, in particular, the axial distance between the two microlens arrays of the illumination system can be adjusted.

[0042] As a result of misalignment or adjustment of the condensation optics, it can happen that a field aperture of the illumination system is only projected indistinctly onto the object plane by the condensation optics. However, this is not critical for many applications and merely leads to a less abrupt drop in light intensity at the edge of the illumination field. The illumination field may therefore exhibit blurred edges, so that the light intensity at the edge no longer drops abruptly, but gradually. This appears to be unproblematic, especially when zooming out, if the surgeon is only checking the positioning of the surgical instruments with the visualization system and then zooming back into the surgical field (possibly in conjunction with reducing the working distance) to outline a potential application.

[0043] The invention thus recognizes that it makes sense to adjust the optical zoom of the Köhler illumination accordingly in response to changes in both of the above input variables (optical zoom / set working distance, i.e., position of the focal plane), i.e., to adjust / tune the condensation optics of the illumination system accordingly. This ensures that, on the one hand, the entire field of view is always illuminated, and on the other hand, that as little light as possible outside this field of view is directed into the observed object plane / working plane, since this light would inevitably be lost for imaging and would only lead to heating of the surrounding tissue, which must be avoided. At the same time, this increases the overall efficiency of the illumination system, or rather, the amount of light provided by the illumination system is used optimally.

[0044] The visualization system, which is used together with the lighting system, can be designed, for example, as a microscope, an exoscope, or an endoscope.

[0045] Furthermore, the visualization system, together with the lighting system, can be positioned by a robot arm in space at a predefined working distance to the object being observed. For this purpose, the lighting system and the visualization system can be mounted on the robot arm; furthermore, as already mentioned, the lighting system can also be integrated into the visualization system.

[0046] A preferred use or embodiment involves implementing an electronic control loop between the lighting system and the visualization system, such that the lighting system automatically and independently adjusts the size of the illuminated area as soon as a user or other instance (such as a controller) of the visualization system changes its optical zoom or the spatial position of the visualization system's focal plane. This allows the size of the illuminated area to automatically decrease and / or the illumination intensity to automatically increase when the visualization system zooms in.Depending on the set optical zoom of the visualization system, the light output of the light source of the lighting system can also be automatically adjusted, especially additionally, to enable optimal lighting.

[0047] For example, if a user or an (electronic) controller focuses the visualization system on a new working distance by changing the spatial position of the visualization system's focal plane and / or performs a zoom-in or zoom-out using the visualization system's optical zoom, the lighting system automatically adjusts the size of the illumination field accordingly, preferably by changing the axial distance between the two microlens arrays or by tuning the condensation optics. This can be implemented, for example, such that when the working distance is reduced, i.e.,At shorter distances between the system and the focal plane, and / or when zooming in with the visualization system, the opening angle of the illumination cone emanating from the lighting system is automatically reduced; this also reduces the size of the illuminated field. Conversely, at maximum working distance and / or maximum zoom-out, the opening angle of the illumination cone can be set to its maximum to fully illuminate the (then enlarged) field of view of the visualization system.

[0048] In such a use, an intersection point between an optical axis of the lighting system and an optical axis of the visualization system can lie within a viewing area of ​​the visualization system, with the visualization system providing a sharp image within the viewing area.

[0049] To solve the aforementioned problem, the features of independent method claim 12 are provided according to the invention. In particular, to solve the problem in an illumination method of the type described above, which is especially suitable for shadow-free illumination of a cavity, it is proposed according to the invention that the illumination light is subsequently (i.e., after passing through the collector optics) guided through two successive microlens arrays (in the illumination beam path) which perform beam shaping and beam homogenization; and that finally the illumination light is guided through at least two, preferably stationary, imaging lenses of an imaging optic of the visualization system to an object plane observed by the visualization system, which, for example, lies within the cavity. An illumination system according to the invention is used to carry out this method.

[0050] An advantage of this method is that the illumination light can fall on the object plane at almost the same angle as an optical axis of the visualization system strikes the object plane (this corresponds to the viewing angle that the visualization system achieves with respect to the object plane). This prevents shadowing in the relevant viewing direction.

[0051] To solve the problem, the features of dependent claim 13, which relates to an observation system, are further provided. In particular, to solve the problem in an observation system of the type mentioned at the outset, it is proposed that the at least one illumination system and the visualization system are each configured for use as described above and / or according to one of the claims directed to a use and / or for carrying out the method described above. The observation system can also be characterized in that the illumination beam path of the illumination system is guided through at least one, preferably several, imaging lens(es) of the visualization system.

[0052] In such a configuration, a portion of the visualization system's optical lens can be used to jointly form the imaging beam path of the visualization system and to shape the illumination beam path. In other words, the condensation optics of the illumination system then comprise not only the two microlens arrays, but also those imaging lenses of the visualization system that help shape the illumination beam path. The illumination beam path then emerges from the last imaging lens of the visualization system.

[0053] This approach has the significant technical advantage that the parallax angle between the optical axes of the illumination and imaging beam paths can be almost completely eliminated. This is advantageous for achieving virtually shadow-free illumination and simultaneous observation of the cavity.

[0054] The inventive approach further has the advantage that – unlike a classic “fly’s eye condenser” based on a microlens array – no separate Fourier lens is required in the illumination system, because the imaging lenses, which shape the illumination beam path, take over the function of the Fourier lens. Therefore, the combined use of lenses in conjunction with the use of microlens arrays in the condensation optics of the illumination system appears particularly innovative, because it allows lenses to perform a dual optical function (imaging and Fourier transformation).

[0055] It should also be noted that in an observation system designed according to the invention, it is not absolutely necessary for the illumination system and the imaging system to share a common optical element. Depending on the application, this can even have disadvantages with regard to the problem of stray light.

[0056] In addition to the features described above, the observation system according to claim 13 also provides that it is mounted on a movable robot arm, with which the observation system can be arranged in space in different positions and / or in different viewing directions.

[0057] In addition to or as an alternative to the aforementioned feature, the observation system may also be configured such that at least one optical axis of the at least one illumination system and one optical axis of the visualization system are arranged relative to each other at a parallax angle, in particular, a specific parallax angle. In such a configuration, the visualization system and the illumination system may share optical elements; however, the opposite is also possible. Furthermore, particularly when using two microlens arrays as described above in the illumination system, the parallax angle may be adjustable / changeable, for example, by means of a suitable adjustment mechanism.

[0058] For example, if two adaptive lighting systems designed according to the invention are used in the west and east with respect to the optical axis of the visualization system, two parallax angles of equal size, symmetrically aligned to the latter axis, can be designed.

[0059] If the visualization system has a sensor-detected field of view in landscape orientation (e.g., in a 16:9 format), it is preferable to position the two lighting systems at the ends of the longer side of the field of view. Using two lighting systems, one to the west and one to the east of the visualization system's optical axis, is particularly advantageous when the visualization system is used to observe a body cavity. This is because using only one lighting system could result in vignetting along the axis (east-west axis) along which the lighting system is laterally offset from the visualization system.

[0060] The use of at least one shared optical element in the imaging and illumination beam path, however, has the significant advantage that it may then suffice to implement only adaptive Köhler illumination using the two microlens arrays, with only one illumination system illuminating the field of view from one side. Given the resulting small parallax angles, the minimal vignetting may still be acceptable in a surgical setting. This reduces complexity.

[0061] It can also be provided that the illumination beam path passes through an axially displaceable imaging lens of the visualization system. In this case, axial displacement of this imaging lens allows for a change, preferably simultaneously, in the size of an illuminated field along with a change in the field of view and / or the working distance of the visualization system. This displaceable imaging lens can, in particular, be designed as an entire lens group as part of a focusing optic. The working distance of the visualization system can be understood here as the distance between the first lens surface of the visualization system and a focal plane that is sharply imaged by the visualization system.

[0062] The goal of axially shifting the shared lenses of the visualization and lighting systems is to change the illumination field simultaneously with changes in the field of view or working distance, without requiring explicit adjustment of the illumination field by changing the distance between the two microlenses. However, by further adjusting the distance between the two microlenses, the size of the illumination field can be adjusted even more precisely. This allows for a functional separation between changes in the illumination field resulting from changes in the working distance and changes in the zoom of the visualization system.An axial displacement of the shared lenses of the visualization system and the lighting system may also lead to a lateral displacement of the lighting field, although this is then merely a parasitic effect.

[0063] Another embodiment provides that the described parallax angle is variable. For this purpose, in particular, the optical axis of the lighting system and / or the optical axis of the visualization system can be designed to be tiltable.

[0064] Additionally or alternatively, a conversion mechanism can be designed, preferably such that an adjustment of a focusing optic of the visualization system, which serves to adjust the spatial position of the focal plane (preferably purely mechanically), can be converted into a corresponding tilting of the optical axis of the illumination system. This makes it possible, in particular, to ensure that the parallax angle can be automatically adjusted depending on the current position of the focal plane.

[0065] It is also possible for the optical axis of the lighting system to be designed to be tiltable. This can be the case, for example, because a condenser lens of the condensation optics is designed to be movable and / or tiltable transversely to this optical axis, or because the entire lighting system is designed to be tiltable relative to the visualization system.

[0066] In such designs, a deflecting prism is not necessarily required; however, a deflecting prism or other deflecting element can be additionally inserted into the beam path to achieve a deflection of the illumination beam path and thus to achieve a different arrangement of the illumination within the system, for example to improve the compactness of the system.

[0067] The laterally movable condenser lens, sometimes also called a projector lens, can preferably follow the two microlens arrays in the beam path. The adjustment of the parallax angle can therefore be achieved by laterally moving such a projector lens, preferably placing this laterally movable projector lens downstream of the two microlens arrays in the beam path.

[0068] Using the conversion mechanism, which can optionally include actuators, the desired tilt of the lighting system's optical axis can be automatically adjusted, depending on the current focus distance of the visualization system. If the working distance is small (short distance between the focal plane and the visualization system), the parallax angle between the two optical axes must be relatively large to ensure complete illumination of the field of view. Conversely, with a larger working distance and / or increasing zoom-in, the parallax angle can be progressively smaller. The relationship between the current working distance in mm and the selected parallax angle in degrees can preferably be non-linear.

[0069] Autofluorescence, which typically occurs at certain wavelengths, e.g., in the near-UV range, often leads to a reduction in illumination intensity in the excitation wavelength range, but also to an additional illumination intensity due to the wavelengths generated by the autofluorescence. This can lead to undesirable interference effects. To improve this, the invention provides that the materials used in the observation system are selected to prevent such autofluorescence. For example, fused silica exhibits very low autofluorescence in the near-UV range and is therefore a suitable material for preventing autofluorescence. It should also be noted that the materials for the two MLAs can generally be selected differently.

[0070] The invention will now be described in more detail with reference to exemplary embodiments, but is not limited to these embodiments. Further embodiments of the invention can be derived from the following description of a preferred embodiment in conjunction with the general description, the claims, and the drawings.

[0071] In the following description of various preferred embodiments of the invention, elements that are identical in function are given identical reference numerals even if they differ in design or shape.

[0072] It shows: Fig. 1 a side view of a lighting system designed according to the invention as part of an observation system which also includes an imaging system, Fig. 2 the observation system of Fig. 1 in a frontal view, Fig. 3 another example of a lighting system designed according to the invention, Fig. 4 a top view and two respective side views on a microlens array, which is in the illumination system according to Fig. 3 is used, Fig. 5 a 3D view of further microlens arrays that could be used in an illumination system according to the invention, Fig. 6 and Fig. 7: an application in which two lighting systems designed according to the invention are used together with an imaging system and finally Fig. Figure 8 illustrates a typical application in which the invention, more precisely a lighting system designed according to the invention, can be advantageously used.

[0073] The Fig. Figure 3 shows a first example of a lighting system 1, which (for example, as in Fig. Figure 1 illustrates that this lighting system can be used for the adaptive illumination of an object 7 located in an object plane 8. This lighting system 1 is intended for use with an imaging system 18 (see Figure 1). Fig. 1) and forms an illumination beam path 6, wherein illumination light from a light source 2 as the starting point of an illumination beam path 6 is first coupled into an optical fiber 40, then deflected by means of a deflecting element 30 in the form of a prism and then initially, as in Fig. As can be seen in Figure 3, a collector optic 3 passes through, which collects the light rays emanating from the end surface of the light guide 40. Thus, the end surface of the light guide 40 forms in the Fig. 3 is the actual light source 2, while the illumination light is provided by the additional primary light source 2. The collector optics 3 collimate the illumination light as much as possible before it falls onto the subsequent condensation optics 4, which is formed by two parallel and spaced-apart microlens arrays 5a and 5b.

[0074] As indicated by reference numeral 23 in Fig. As indicated in Figure 3, the axial distance 23 between the two microlens arrays 5a and 5b can be varied to adjust the optical focal length of the condensation optics 4. For this purpose, the illumination system 1 has an adjustment device 11 in the form of an electronically controllable actuator 16, which is connected to a controller 38 via a control line and is controlled by the latter. If the axial distance 23 is adjusted using the actuator 16, the size of an illumination field 9 in the object plane 8 changes (see Figure 3). Fig. 1), which is supplied with illumination light by the condensation optics 4. This adaptive adjustment of the illumination field 9 by adjusting the axial distance 23 can occur either when a working distance between the object plane 8 and the condensation optics 4 is unchanged or has changed, for example, because the entire illumination system 1 is positioned at a greater distance from the object 7.

[0075] Not shown in the figures, but technically equivalent, would be a configuration of the illumination system 1 in which the distance between the two microlens arrays 5a and 5b remains constant, but at least one of the two microlens arrays 5a and 5b is tuned, for example by changing the focal length of the microlenses 28 of the affected microlens array 5a / 5b, whereby a suitable actuator could of course also be used for this purpose. For example, it would be conceivable to use optofluidic microlenses 28 with variable focal length in the respective microlens array 5a and / or 5b.

[0076] As with lighting system 1 according to Fig. 3 can also be recognized in the one who Fig. 1, that, originating from the collector optics 3, a beam 24 of the illumination beam path 6 is incident on the first of the two microlens arrays 5a. This incident beam 24 is transformed by the two microlens arrays 5a and 5b into an outgoing beam 25, which has a rectangular radiation cross-section. This can be seen in particular from the two intensity profiles 41a and 41b at the left edge of the Fig. Figure 3 illustrates that the intensity profile of the primary light source 2, as well as the end face of the optical fiber 40, exhibits a rotationally symmetric intensity distribution 41a. The two microlens arrays 5a and 5b convert this intensity distribution 41a into the rectangular intensity distribution 41b shown, which can, for example, have a 16:9 aspect ratio. This is advantageous, for instance, if an image sensor of the same format is used in the associated imaging system 18.

[0077] Furthermore, the use of the two microlens arrays 5a and 5b offers the technical advantage that the said intensity distribution 41b is homogenized, so that ultimately a rectangular illumination field 9 can be obtained with a homogeneous intensity distribution in the object plane 8.

[0078] The Fig. Figure 4 shows an example of a single-sided microlens array 5, which could be used in condensation optics 4. Numerous microlenses 28, each with a consistent lens shape, are arranged on a regular grating. Furthermore, the rectangular aperture of each lens is evident. Since the microlenses 28 are arranged in the periodic pattern shown, an intensity profile with very low ripple can be obtained in the illumination field 9, so that the profile resembles a so-called "flattop".

[0079] The Fig. Figure 5 shows a perspective view of another microlens array 5, with the front side 35 of the microlens array 5 visible in the left half of the figure, while the back side 36 is visible on the right. In this embodiment, the microlenses 28 are each configured as cylindrical lenses. Furthermore, it can be seen that these cylindrical lenses are aligned along the x-axis on the front side 35, while they are aligned orthogonally to this along the y-axis on the back side 36. In other words, the microlens 28 in the front side 35 is oriented in a different way. Fig. 5 Microlens array shown 5 double-sided cylindrical lenses whose orientation between the front 35 and the back 36 is rotated by exactly 90°.

[0080] Based on the frontal view of the Fig. 2 can be seen that this observation system 19 designed according to the invention has, in addition to the imaging visualization system 18 shown, two lighting systems 1a and 1b each designed according to the invention, wherein in the side view of the Fig. Figure 1 illustrates only the left illumination system 1a together with the visualization system 18. The visualization system 18 comprises an imaging optic 26, which is formed by the multi-lens objective 31 shown and two further imaging lenses 27, the latter imaging the object 7 onto the image sensor 32 shown. In addition to the two fixed lenses 13 and 15, the objective 31 includes a further lens 14, which is designed to be axially displaceable along the optical axis 22, thus creating a movable focusing optic. With the aid of this focusing optic, different working distances 37 can be achieved (see the example of the Fig. 6 and Fig. 7) be set so that objects 7 can be focused at different distances from the visualization system 18.

[0081] The visualization system 18 also features a tunable focus optic 12, enabling it to deliver a sharp image at varying working distances. Furthermore, the visualization system 18 also includes a zoom optic 17, allowing the zoom level to be adjusted (see Figure 18). Fig. 1).

[0082] If a surgeon using the visualization system 18 during a medical procedure performs a zoom-out while maintaining a constant working distance, the field of view projected onto the image sensor 32 increases. This can be useful, for example, to gain an overview of the surgical area. The surgeon can then perform a zoom-in, which reduces the field of view but reveals more detail in the image. In such situations, the two illumination systems 1a and 1b can each be adjusted so that, in response to the optical zoom adjustment (where the working distance may remain constant), the size of the respective illumination field 9a, 9b (see Figure 1) is determined. Fig. 2) is adjusted by adjusting the respective condensation optics 4a / 4b. For this purpose, the axial distance 23 between the respective two microlens arrays 5a and 5b is adjusted. This can be simplified as follows: the condensation optics 4 also perform an optical zoom, but with respect to the illumination field 9, which results in the object plane 8. This adjustment of the illumination field can be automated by an electronic controller 38 (as, for example, in Fig. 3 shown), a respective adjusting means 11 for adjusting the condensation optics 4a, 4b.

[0083] As the Fig. As illustrated in Figure 8, an illumination system 1 according to the invention, together with an associated visualization system 18 in the form of a surgical microscope, can be arranged on a robot arm 20 so that they can be positioned together in space relative to the patient 34. Thus, the invention can be advantageously used, in particular, in a medical robotics system. The surgeon can view a live image, which is recorded by the visualization system 18, on the monitor 33 and operate / control both the robot arm 20 and the focusing unit and the optical zoom 12 of the visualization system 18 via a remote control. The illumination system then automatically adjusts the size of the illumination field 9 in response to an adjustment of the focal plane or a change in the optical zoom by adjusting the condensation optics 4, as described above.

[0084] Such an adjustment of the condensation optics 4 can therefore be made in particular in response to an adjustment of the spatial position of a focal plane of the visualization system 18, i.e., when the working distance 37 of the visualization system 18 is adjusted using the described focusing optics, for example, by the operator. In such a case, the illumination field 9 can also be adjusted in size in a new object plane 8 by adjusting the axial distance 23 between the two microlens arrays 5a and 5b. This ensures that the entire field of view, which is currently being observed with the visualization system 18 and displayed on the monitor 33, is always sufficiently illuminated by the illumination beam path 6.

[0085] In the Fig. In the overall system shown in Figure 8, an electronic control loop between the lighting system 1 and the visualization system 18 is implemented such that the lighting system 1 automatically and independently adjusts the size of the generated illumination field 9 as soon as an optical zoom of the visualization system 18 or a spatial position of the focal plane of the visualization system 18 is changed. For example, if the operator zooms in with the visualization system 18, the size of the illumination field 9 automatically decreases. Since the illumination intensity in the illumination field 9 also increases in this case, it can additionally be implemented that the light output of the light source 2 is automatically adjusted to avoid excessive illumination of the object plane 8.

[0086] One can also recognize in Fig. 8, that the optical axis 21 of the lighting system 1 and the optical axis 22 of the visualization system 18 are arranged at a parallax angle to each other.

[0087] In Fig. Figure 1 clearly shows that the illumination beam path 6 passes through both the described axially movable focusing optics, realized by the axially displaceable imaging lens 42, and through the two fixed lenses 13 and 15 of the objective 31. However, other configurations are also conceivable: For example, the third lens 15 would not necessarily have to be fixed; several optical lenses of the objective 31 could also be displaceable. For example, an observation system 19 according to the invention can also be constructed such that the illumination beam path 6 of the illumination system 1 passes under the imaging beam path 39 of the imaging system 18 through two shared lens groups; in this case, for example, one of the lens groups can be fixed and the other axially displaceable.

[0088] In the example of the Fig. 1 and Fig. 2. Thus, the illumination light emitted by the respective illumination systems 1a and 1b is, after collimation by the corresponding collector optics 3 and passing through the two microlens arrays 5a and 5b, which perform beam shaping and homogenization, guided through two stationary imaging lenses 27 of the imaging optics 26 of the visualization system 18, namely the two lenses 13 and 15. The illumination light ultimately reaches the object plane 8 observed by the visualization system 18 to illuminate the respective illustrated illumination fields 9a and 9b. This approach has the significant advantage that narrow cavities, such as body cavities, observed by the visualization system 18, can be illuminated with the two illumination systems 1a and 1b with virtually no shadowing.

[0089] If the observation system 19 is used according to the Fig. 1 and Fig. 2 If the movable imaging lens 42 of the visualization system 18 is moved axially along the optical axis 21, not only does the field of view and a working distance 37 of the visualization system 18 change, but the size of the illuminated illumination field 9 also changes, because the illumination beam path 6 also passes through this imaging lens 42.

[0090] The Fig. 6 and Fig. Figure 7 illustrates that in an observation system 19 according to the invention, the respective optical axes 21a, 21b of the two illumination systems 1a and 1b used can be designed to be tiltable, so that the parallax angle, which exists between the respective optical axis 21 and the optical axis 22 of the visualization system 18, can be adjusted depending on the current position of the focal plane or working distance 37. However, it is not absolutely necessary for this to involve the entire illumination system 1 as shown in Figure 7. Fig. 6 and Fig. Figure 7 illustrates that the optical axis 21 can be tilted; rather, for example, a condenser lens of the condensation optics 4 can also be shifted transversely to the optical axis 21 to achieve the desired tilt of the optical axis 21. Accordingly, the illumination system 1 can therefore include such a condenser lens that is shiftable transversely to the optical axis 21.

[0091] In summary, to improve the luminous efficiency and compactness of an illumination system 1, which can be used together with an imaging visualization system 18, it is proposed that the illumination system 1 comprise two microlens arrays 5a and 5b, which are either displaceable relative to each other along an optical axis, or wherein at least one of the two microlens arrays 5a, 5b is optically tunable, such that the effective focal length of the condensation optics 4 formed by these microlens arrays 5a and 5b can be changed. This approach has the advantage that the size of an illumination field 9 lit by the condensation optics 4 can be adjusted situationally and extremely quickly, particularly when a focal plane observed with the visualization system 18 shifts or when, for example, an optical zoom 12 of the visualization system 18 is changed.This ensures optimal illumination of the respective field of view at all times, especially without having to more or less strongly obscure part of the illumination beam path 6 of the lighting system 1 (cf. . Fig. 1). Reference symbol list 1 Lighting system 2 light sources 3 Collector optics (for collecting light rays emanating from 2) 4 Condensation optics, in particular designed as a condensation lens group 5 microlens array 6. Illumination beam path (originates from 2, is limited by 5) 7 objects 8. Object level (this is where the object to be observed / illuminated is located) 9 Lighting area (defined by 5 / 4) 10 Aperture (defined by 5 / 29) 11 Adjustment devices (for adjusting 4) 12 Focus Optics 13 first lens 14 second lens 15 third lens 16 Actuator 17 Zoom optics 18 Imaging system, in particular designed as a medical visualization system (e.g. as a microscope, exoscope or endoscope) 19 Observation system 20 robot arms 21 optical axis (of 1) 22 optical axis (out of 18) 23 axial distance (between 5a and 5b) 24 incident beam of rays (originating from 3, incident on 4) 25 outgoing beam of rays (emitted from 4) 26 Imaging optics (may also include zoom optics) 27 (optical) imaging lenses 28 microlenses 29 Light field aperture 30 Deflection element (e.g. designed as a prism or mirror) 31 lenses (out of 18) 32 image sensor 33" Monitor 34 patients 35 Front 36 Back 37 Working distance 38 controllers 39 Image beam path (of 26 / 18) 40 fiber optic cables 41 Intensity profile or intensity distribution 42 axially movable imaging lenses

Claims

[1] Illumination system (1) for adaptively illuminating an object (7) located in an object plane (8), with an illumination beam path (6), wherein the illumination system (1) is intended for use with an imaging system (18) and wherein the illumination system (1) comprises: - a light source (2) as the starting point of the illumination beam path (6), - a collector optic (3) for collecting light rays emanating from the light source (2), and - a condensation optic (4) for illuminating the object plane (8), characterized by that the condensation optics (4) comprises two microlens arrays (5a, 5b), - wherein their axial distance (23) from one another along an optical axis (21) is adjustable by means of an adjusting means (11) in the form of an electronically controllable actuator (16) and / or - wherein at least one of the two microlens arrays (5a, 5b) is designed to be optically tunable. [2] Illumination system (1) according to claim 1, wherein an optical focal length of the condensing optics (4) is - Adjusting the axial distance (23) between the two microlens arrays (5a, 5b) and / or - is tunable by detuning at least one of the two microlens arrays (5a, 5b), and / or - wherein a size of an illumination field (9) in the object plane (8) which is supplied with illumination light by the condensation optics (4), - in particular, it is adaptable either at a constant working distance between the object plane (8) and the condensing optics (4), by adjusting the axial distance (23) between the two microlens arrays (5a, 5b) and / or by detuning at least one of the two microlens arrays (5a, 5b). [3] Illumination system (1) according to one of the preceding claims, wherein the two microlens arrays (5a, 5b) form an incident beam (24) of the illumination beam path (6) into an outgoing beam (25) which results in a rectangular format, preferably of 16:9, of the illumination field (9), - in particular wherein the light source (2) provides a non-rectangular, for example approximately rotationally symmetric, intensity distribution (41a). [4] Illumination system (1) according to the preceding claim, wherein the two microlens arrays (5a, 5b) effect an optical homogenization of an intensity distribution (41b) within the rectangular illumination field (9), in comparison to an intensity distribution of the light source (2) of the illumination system (1) and / or - wherein both microlens arrays (5a, 5b) each have microlenses (28) on both sides. [5] Illumination system (1) according to one of the preceding claims, wherein the two microlens arrays (5a, 5b) each have, in particular on the front and / or rear side, microlenses (28) which have a rectangular basic shape and / or optical aperture and / or - wherein microlenses (28) of the two microlens arrays (5a, 5b) are arranged in a respective periodic pattern, preferably so that a flattop intensity profile with a waviness of less than 15% is achieved in the illumination field (9), - and / or wherein at least one of the two microlens arrays (5a, 5b) provides microlenses (28) with an aspherical contour and / or - wherein at least one of the two microlens arrays (5a, 5b) comprises cylindrical lenses, - in particular wherein at least one of the two microlens arrays (5a, 5b) has cylindrical lenses on both sides, wherein an alignment of these cylindrical lenses between a front side (35) and a rear side (36) is rotated by 90°. [6] Illumination system (1) according to one of the preceding claims, wherein in at least two different adjustments of the condensation optics (4) a quantity of light of the illumination beam path (6) provided by the light source (2) and leaving the collector optics (3) - completely passes through the two microlens arrays (5a, 5b) and / or - can be fully used to illuminate the lighting field (9). [7] Illumination system (1) according to one of the preceding claims, wherein an entire light beam emitted by the collector optics (3) emerges from the rear of the two microlens arrays (5b) as a shaped beam in all adjustable relative positions of the two microlens arrays (5a, 5b). [8] Lighting system (1) according to one of the preceding claims, wherein the light source (2) is formed by the end face of a light guide (40), - in particular wherein the end face emits light with a maximum beam angle of less than 40°, preferably less than 20°. [9] Use of an illumination system (1) according to one of the preceding claims for illuminating an object plane (8) which is simultaneously observed with an imaging visualization system (18), - where, in response to - an adjustment of an optical zoom, in particular with a constant working distance (37) between the object plane (8) and the condensation optics (4), and / or - an adjustment of a spatial position of a focal plane of the visualization system (18), a size of the illumination field (9) in the object plane (8) is adjusted by detuning the condensation optics (4) and / or adjusting the axial distance (23) between the two microlens arrays (5a, 5b), - in particular, wherein a luminous field diaphragm (29) of the illumination system (1) is only imaged in an out-of-focus manner by the condensation optics (4) into the object plane (8). [10] Use according to the preceding claim, - wherein the visualization system (18) is designed as a microscope, an exoscope or an endoscope and / or is positioned together with the illumination system (1) by a robot arm (20) in space at a predeterminable working distance from the object (7) to be observed, in particular wherein for this purpose the illumination system (1) and the visualization system (18) are mounted on the robot arm (20). [11] Use according to one of the two preceding claims, - wherein an electronic control loop is implemented between the illumination system (1) and the visualization system (18), so that the illumination system (1) automatically and independently adjusts the size of the illumination field (9) as soon as a user of the visualization system (18) changes its optical zoom or the spatial position of the focal plane of the visualization system (18), - preferably so that when zooming in with the visualization system (18), the size of the illumination field (9) is automatically reduced and / or the illumination intensity in the illumination field (9) is increased, - in particular wherein, depending on the set optical zoom of the visualization system (18), a light output of the light source (2) of the illumination system (1) is additionally automatically adjusted. [12] Method for shadow-free illumination of a cavity, in particular a body cavity, which is observed with a visualization system (18), - wherein illumination light emanating from a light source (2) is first at least approximately collimated by means of a collector optic (3), characterized by , - that the illumination light is subsequently guided through two successive microlens arrays (5a, 5b) which carry out beam shaping and beam homogenisation, and - finally, through at least two, preferably immobile or stationary, imaging lenses (27) of an imaging optics (26) of the visualization system (18) into an object plane (8) observed with the visualization system (18), which lies, for example, within the cavity, and - wherein a lighting system (1) according to one of claims 1 to 8 is used to carry out this method. [13] Observation system (19), in particular for medical applications, comprising - at least one lighting system (1) according to one of claims 1 to 8 and - an imaging visualization system (18) which provides a variable optical zoom, characterized by , - that the at least one lighting system (1) and the visualization system (18) are each set up for use according to one of claims 9 to 11 or for carrying out the method according to claim 12 and - that the observation system (19) is mounted on a movable robot arm (20) with which the observation system (19) can be arranged in space in different positions and / or in different viewing directions and / or - that at least one optical axis (21) of the at least one illumination system (1) and one optical axis (22) of the visualization system (18) are arranged at a, in particular respective, parallax angle to one another. [14] Observation system (19) according to claim 13, - wherein the illumination beam path (6) passes through an axially displaceable imaging lens (42) of the visualization system (18), - in particular so that by axially displacing this imaging lens (42) a, preferably simultaneous, change in the size of an illumination field (9) illuminated by the illumination beam path (6) can be achieved together with a change in a field of view and / or a working distance (37) of the visualization system (18). [15] Observation system (19) according to one of claims 13 or 14, wherein the parallax angle is designed to be variable, in particular wherein for this purpose the optical axis (21) of the illumination system (1) and / or the optical axis (22) of the visualization system (18) are designed to be tiltable, and / or - wherein a conversion mechanism is designed so that an adjustment of a focusing optics of the visualization system (18), which serves to adapt the spatial position of the focal plane, can be converted, preferably purely mechanically, into a corresponding tilting of the optical axis (21) of the illumination system (1), - in particular so that the parallax angle can be automatically adjusted depending on the current position of the focal plane - or wherein the optical axis (21) of the lighting system (1) is tiltable, - because a condenser lens of the condensation optics (4) is designed to be displaceable and / or tiltable transversely to this optical axis (21) or - because the entire lighting system (1) is designed to be tiltable with respect to the visualization system (18).

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