REFLECTIVE OPTICAL SYSTEM WITH ADJUSTABLE EFFECTIVE FOCAL LENGTH AND OPTICAL STRUCTURE

Abstract

The invention relates to a reflective optical system with adjustable effective focal length, the use of such a reflective optical system, and a method for calculating the mirror surfaces for such an optical system.

Description

[0001] The invention relates to a reflective optical system with adjustable effective focal length, the use of such a reflective optical system, and a method for calculating the mirror surfaces for such an optical system.

[0002] Optical systems with adjustable focal length can be used in both illumination and imaging systems. The former enables the application of the solution for beam-shaping tasks, for example, for shaping laser beams in laser material processing. In imaging optical systems, optical systems with adjustable focal length can be used to image at least two different object fields in two states onto a common, fixed image plane.

[0003] Refractive optical systems with adjustable focal lengths are particularly well known in the prior art. For example, US Pat. Nos. 3,507,565 A and 3,305,294 A describe lens systems with a variable focal length. In these solutions, consisting of a pair of lenses, a variation in the focal length is achieved through opposing lateral movements of equal magnitude.

[0004] However, refractive systems exhibit low transmission, high chromatic dependence of aberrations and physical limitations of surface complexity, for example due to total internal reflection.

[0005] The document DE 10 201 008 342 A1 describes an imaging system for imaging an object onto an image sensor, which has a front side facing the object and a rear side facing away from the object, which rear side is arranged behind the front side when viewed from the object. Furthermore, the imaging system has a light entry device on the front side, through which light coming from the object can enter the imaging system. The light passes through the beam path between the object and the image sensor. Likewise described are a first and a second optical element, which are arranged on the rear side in such a way that they can influence the beam path. The light entry device has an electrically switchable liquid crystal element, which deflects the beam path at least at a first angle and a second angle different from the first, depending on the electrical circuit state.This electrically induced change in the beam path enables a discretely switchable change in focal length.

[0006] The document US 2018 / 0164573 A1 discloses an anastigmat telescope with three aspherical mirrors, which has means for linearly moving the third mirror along the optical axis of the telescope in order to change the focal length of the telescope to a plurality of focal lengths between at least a minimum focal length and a maximum focal length.

[0007] Furthermore, the document US 2015 / 0234153 A1 describes a reflective varifocal lens configured to change a focal length using an electrical signal, the lens comprising a first conductive electrode layer, an electrically active polymer layer formed on the first electrode layer, a second conductive electrode layer formed on the electrically active polymer layer, and a reflective layer configured to reflect incident light toward the first electrode layer or the second electrode layer, wherein a shape of the electrically active polymer layer is changed by the electrical signal applied to the first electrode layer and the second electrode layer, and when the shape of the electrically active polymer layer changes, a shape of the reflective layer changes, thereby changing a focal length of reflected light.

[0008] The object of the invention is therefore to provide an optical system which eliminates the disadvantages of such systems in the prior art and enables low chromatic aberrations.

[0009] This object is achieved by the reflective optical system having the features of claim 1 and an optical structure having the features of claim 13. The features of the dependent claims show further developments according to the invention.

[0010] The concept of adjustable effective focal lengths is transferred to a reflective application, which allows both a continuously adjustable and a discretely adjustable focal length.

[0011] According to the invention, a reflective optical system with an adjustable effective focal length is proposed. The reflective optical system has at least two movable mirror surfaces arranged off-axis and one after the other along a beam path of the optical system. The movable mirror surfaces can each be moved from a first displacement position, hereinafter also referred to simply as the first position, to at least one second displacement position, hereinafter also referred to as the second position.

[0012] In the first position, first functional regions of the movable mirror surfaces are arranged in the beam path. According to the invention, the first functional regions are designed such that they jointly produce a first finite focal length.

[0013] In the second position, second functional areas of the movable mirror surfaces are arranged in the beam path. The second functional areas are designed such that together they produce a second, different, finite focal length. As a result, the effective focal length of the optical system with the movable mirror surfaces in the first position differs from the effective focal length of the optical system with the movable mirror surfaces in the second position.

[0014] According to the invention, the mirror surfaces are arranged in every position such that the object- and image-side sections of the optical axis of the optical system are fixed regardless of the position. This means that the beam position at the input and output of the optical system is constant regardless of the position of the mirrors. In other words, the optical system has exactly one input / output channel through which light rays to be imaged can enter / exit. The position of the object- and image-side sections of the optical axis of the optical system are not changed by shifting the movable mirror surfaces from the first position to the second position.

[0015] This can be achieved, for example, by compensating for a change in the beam position within the optical system due to a shift and / or tilt of one of the movable mirror surfaces by appropriately shifting and / or tilting the other movable mirror surface. It is also possible to shift each of the movable mirrors in such a way that the beam position remains unchanged even within the optical system.

[0016] The optical system according to the invention can, in particular, be designed such that it has a plurality of positions. The mirror surfaces can, in particular, be designed such that they allow for equally discrete or continuous adjustment of the effective focal lengths.

[0017] The application is not limited to specific wavelength ranges and conceptually enables use from the UV to the IR wavelength range. It can be used for both terrestrial and extraterrestrial applications. According to the invention, it is also conceivable to use it in simple microscope optics for imaging with different focal lengths as a continuous or discrete system. Unlike the state of the art, the solution presented does not represent a complete telescope, but can be coupled with various types of telescopes. In general, an independent application of the beam-shaping assembly without additional telescopes is also conceivable. It can be arranged as a relay system or downstream of the telescope.

[0018] In an advantageous embodiment of the optical system, displaceable mirror surfaces, the functional areas of which together produce a focal length, are preferably arranged together on a single substrate, wherein the substrate is displaceable relative to the beam path.

[0019] In a further advantageous embodiment of the optical system, the mirror surfaces are shaped and arranged such that two light rays which pass through an object point in an object plane spaced from the object-side section of the optical axis and immediately thereafter pass through the optical system with mirror surfaces in the first position have an intersection point at a first image point in an image plane; and two light rays which pass through the same object point in the object plane spaced from the object-side section of the optical axis and immediately thereafter pass through the optical system with mirror surfaces in the second position have an intersection point at a second image point in the image plane.In other words, the movable mirror surfaces and their functional areas are designed and arranged such that an object arranged in an object plane is imaged onto a single image plane. The magnification factor of an image produced by the optical system with mirror surfaces in the first position differs from the magnification factor of the image produced by the optical system with mirror surfaces in the second position.

[0020] In a particularly advantageous embodiment of the optical system, the system has four or more, advantageously an even number, movable mirror surfaces. The larger number of movable mirror surfaces, each with at least two functional areas, enables several finite focal lengths, which are caused by the functional areas arranged in the beam path, to be specifically coordinated with one another. In particular, the focal lengths caused in the different positions can be coordinated with one another in such a way that the object and image planes are fixed at different magnification factors. Such a structure can therefore, for example, simplify the realization of the above-described fixed object and image planes at different magnifications. The first and fourth movable mirror surfaces can be arranged together on a first substrate.Independently of this, the second and third movable mirror surfaces can be arranged together on a second substrate. Furthermore, a beam deflection unit can be provided in such a configuration. A beam deflection unit can be considered any element that deflects a light beam by a specific angle. Beam deflection units designed as retroreflectors and capable of deflecting the light beam by 180° are particularly advantageous.

[0021] Preferably, the first movable mirror surface, the second movable mirror surface, the beam deflection unit, the third movable mirror surface, and the fourth movable mirror surface are arranged one after the other in the beam path. The mirror surfaces are configured such that the first and fourth movable mirror surfaces have functional areas that jointly achieve specific focal lengths, and the second and third movable mirror surfaces have functional areas that jointly achieve specific focal lengths.

[0022] In particularly advantageous embodiments of the invention, at least one, preferably two, and particularly preferably each of the movable mirror surfaces forms an angle of 45° with the optical axis. This can mean, in particular, that the vertices of the movable mirror surfaces form an angle of 45° with the optical axis. It is particularly advantageous if the beam path is deflected by 45° by reflection from the mirror surfaces.

[0023] In further advantageous embodiments of the invention, the optical system has a displacement path along which a displaceable mirror surface can be displaced from the first to the second position. The displacement path is advantageously linear and preferably runs along a direction that lies within the displaceable mirror surface that can be displaced along the displacement path and / or is orthogonal to the optical axis. This makes it particularly easy to ensure that the beam position is not changed by a displacement of the mirror surfaces along the displacement path.

[0024] It can be particularly advantageous if displacement paths along which two displaceable mirror surfaces, whose functional surface together effect a focal length, can be displaced from the first to the second position, are rectified and / or of equal magnitude.

[0025] In particularly advantageous embodiments of the invention, at least one of the mirror surfaces is designed as a freeform, which can be described by a basic description with higher-order terms. The basic description can be, in particular, spherical, elliptical, aspherical, parabolic, or hyperbolic. The higher-order terms can advantageously be Zernike polynomials. The freeform is designed in particular to form the functional areas of the mirror surfaces described above.

[0026] The production of free-form mirrors also enables precise referencing through optical subapertures and mechanical contact structures on the monolithic optics, which can be manufactured in one step with the optical mirror surface, thus simplifying adjustment and enabling it to be carried out with high accuracy.

[0027] In further advantageous embodiments, at least one of the mirror surfaces has an aperture that can be used as a reference for monitoring the position and orientation of the mirror surfaces relative to each other. The aperture can be formed as a region in the freeform shape of the mirror surface. Advantageously, an additional reflective surface can be integrated into one of the mirror surfaces, with the additional reflective surface assuming the task of monitoring the position and orientation. This can also be integrated into the freeform shape accordingly.

[0028] Embodiments of the invention are also possible in which at least one optical reference is arranged on the optical components, such as the mirror surfaces or the substrates of the mirror surfaces. Furthermore, in advantageous embodiments of the invention, mechanical references and / or mechanical support structures can be arranged in an assembled or machined manner on at least one of the optical components.

[0029] In a further embodiment of the invention, at least one refractive element is arranged in the beam path of the optical system. This can be particularly useful for applications with a narrow wavelength range in which chromatic aberrations play a less significant role.

[0030] In particularly advantageous embodiments, the reflectivity of the mirror surfaces at a wavelength greater than or equal to 900 nm and / or a wavelength between 300 nm and 900 nm and / or a wavelength less than or equal to 300 nm is greater than 90%, preferably greater than 95%. Embodiments in which the mirror surfaces reflect light in the visible range, i.e. at wavelengths between 400 nm and 800 nm, are particularly advantageous. The reflectivity of the mirror surfaces for light with a wavelength in a wavelength range between 400 nm and 800 nm is advantageously greater than 50%, particularly advantageously greater than 75%, most particularly advantageously greater than 90%.The reflectivity can be greater than 50%, particularly advantageously greater than 75%, very particularly advantageously greater than 90% in the entire range between 400 nm and 800 nm, or only in a 5 nm, advantageously 50 nm, particularly advantageously 100 nm wide sub-range between 400 nm and 800 nm.

[0031] According to the invention, an optical assembly is proposed, comprising a previously described optical system and at least one imaging optical system, in particular a telescope optical system or a microscope optical system, wherein the optical system is integrated into the imaging optical system or is arranged upstream or downstream of the imaging optical system. By shifting the mirror surfaces into the various shift positions, the magnification factor of the overall system can be changed.

[0032] According to the invention, a method for calculating surface shapes of the movable mirror surfaces for the optical system described above with two effective focal lengths is also provided, comprising the steps: Defining an optimization parameter / goal (e.g. wavefront criterion, RMS spot radius, MTF) for the system Defining the geometric boundary conditions: o Defining distances and angles between the mirror surfaces, whereby the distances are defined in the direction of the beam path as well as lateral to the beam path, o Defining the displacement path of the movable mirror surfaces, Defining the diameter of the mirror surfaces Defining the optical boundary conditions: o Defining the application wavelength(s) o Defining the effective focal length and / or achievable magnification factors of the optical system and the resulting definition of the object and image field(s) as well as the numerical apertures for both configurations, Defining the pupil position and size, Defining the basic description and the associated core properties (e.g.Surface curvature, conic constant, aspheric coefficients), ∘ Determination of the mathematical description to be used for the freeform surfaces, ∘ Determination of the power distribution for the mirror surfaces (converging, diverging) ∘ If necessary, more precise definition of the relative surface position of the freeforms (e.g. the surface vertices).

[0033] Such a procedure can be performed using available optical design and / or optimization tools. Of course, the procedure described above can be extended to any number of effective focal lengths or achievable magnifications with a fixed object and image plane.

[0034] The following figures and examples are intended to explain the subject matter of the invention in more detail without wishing to restrict it to the embodiments shown herein.

[0035] It shows: Figure 1 shows a schematic representation of an embodiment of an optical system according to the invention in two positions. Figure 2 shows a substrate with two mirror surfaces of an optical system according to the invention. Figure 3 shows a perspective view of a further embodiment of the optical system according to the invention. Figure 4 shows the embodiment of the optical system according to the invention of the Figure 3 in two positions. Figure 5 shows the embodiment of the optical system according to the invention of Figure 3 in side view. Figure 6 shows a schematic representation of another embodiment of an optical system according to the invention in two positions.

[0036] Figure 1shows a schematic representation of a first embodiment of an optical system 1 according to the invention. The optical system 1 has a first displaceable mirror surface 2 and a second displaceable mirror surface 8. Both mirror surfaces 2, 8 each enclose an angle with the beam path 15 and are arranged one after the other along the beam path 15. Figure 1 shows the optical system 1 according to the invention in two different states: In Figure 1a ) both movable mirror surfaces 2, 8 are each in a first position. In Figure 1b ) both movable mirror surfaces 2, 8 are each arranged in a second position.

[0037] Each of the movable mirror surfaces 2, 8 has two functional areas: The first movable mirror surface 2 has a first functional area 3 and a second functional area 4. The second movable mirror surface 8 has a first functional area 9 and a second functional area 10.

[0038] If the first mirror surface 2 is in the first position, the first functional area 3 is arranged in the beam path 15 of the optical system. If the first mirror surface 2 is in the second position, the second functional area 4 of the first movable mirror is arranged in the beam path 15 of the optical system. If the second mirror surface 8 is in the first position, the first functional area 9 of the second mirror surface is arranged in the beam path 15 of the optical system. If the second mirror surface 8 is in the second position, the second functional area 10 is arranged in the beam path 15 of the optical system.

[0039] The functional areas of the movable mirror surfaces are each designed such that together they produce a finite focal length. In other words, light rays that are incident parallel to the optical axis, subsequently reflected by the first functional area 3 of the first movable mirror surface 2, and subsequently reflected by the first functional area 9 of the second movable mirror surface 8, are focused onto a first focus located on the image-side portion of the optical axis. Light rays that are incident parallel to the optical axis, subsequently reflected by the second functional area 4 of the first movable mirror surface 2, and subsequently reflected by the second functional area 10 of the second movable mirror surface 8, are focused onto a second focus located on the image-side portion of the optical axis.In principle, more than two functional areas per mirror surface are possible, so that more than two finite focal lengths can be achieved.

[0040] According to the invention, the movable mirror surfaces 2, 8 can be moved from their respective first position to their respective second position. A displacement path, i.e. the path or route along which one of the movable mirror surfaces can be guided from its first position to the second position, can be straight, for example. Embodiments are also possible in which the movable mirror surfaces 2, 8 can each be moved to more than two positions or even continuously. Such additional positions can, for example, be arranged at different points along the displacement path between the first and second positions. At least one or all of the movable mirror surfaces 2, 8 can be guided, for example, on a linear guide or a joint mechanism / solid-state mechanism.

[0041] According to the invention, the mirror surfaces are arranged in each position such that the beam position at the input and output of the optical system remains unchanged. This means that the mirror surfaces are arranged in the first and second positions such that the object-side sections of the optical axis 16 and the image-side sections of the optical axis 17 are fixed.

[0042] In the embodiment of the Figure 1This is achieved, for example, by arranging the mirror surfaces in such a way that both the point in the beam path at which the beam path strikes a movable mirror surface or one of the functional areas of the mirror surface, as well as the angle between the incident and emerging beam paths, are the same in every position. Embodiments are also conceivable in which deviations from the previously described rules can be made. Since, according to the invention, two movable mirror surfaces are provided, a positional deviation caused by a displacement or tilting of one mirror can be compensated for by a corresponding displacement or tilting of the other mirror.

[0043] For example, embodiments are possible in which the location in the beam path at which a movable mirror surface is arranged differs between the first and second positions. Such an embodiment is shown, for example, in Figure 6 shown. In this embodiment, however, the resulting offset of the beam path can be compensated by the second movable mirror surface.

[0044] Figure 1b shows, by way of example, a first displacement direction 25a, which indicates the direction in which both movable mirror surfaces 2, 8 can be moved from their respective first to their respective second positions. Alternatively or additionally, the movable mirror surfaces can also be moved in a second displacement direction 25b. The second displacement direction is in Figure 1bperpendicular to the drawing plane. The direction of movement can be, for example, within the mirror plane or perpendicular to the normal of the mirror surface.

[0045] An optical system according to the invention may comprise, in addition to the at least two movable mirror surfaces 2, 8, further mirror surfaces or other optical elements. Each of the further mirror surfaces or each of the other optical elements may be movable or fixed. In the embodiment of the Figure 1 The optical system includes a deflecting mirror 36. The deflecting mirror 36 is arranged immovably. The deflecting mirror 36 is arranged in the beam path between the first movable mirror surface 2 and the second movable mirror surface 8.

[0046] Furthermore, it is possible to combine several of the arrangements described above, each with two movable mirror surfaces. As an example, a combination of two arrangements, each with two movable mirror surfaces, is shown below. It is also possible to combine the arrangement described above with any number of movable mirror surfaces.

[0047] Figure 2shows a perspective view of a single substrate 20 on which two movable mirror surfaces 2, 8 are arranged, whose functional regions each jointly produce a finite focal length. As a result, movements of the two movable mirror surfaces 2, 8 are necessarily mechanically coupled to one another. In particular, the functional regions can be arranged within the movable mirror surfaces 2, 8 such that the first and second functional regions of the mirror surfaces 2, 8 are spaced apart from one another by the same direction and amount. This can ensure, for example, that when the substrate is moved, first functional regions are arranged in the beam path or second functional regions are arranged in the beam path. This can make the optical arrangement more robust against external disturbances. Likewise, the structure of the overall system can be simplified.

[0048] Figure 3shows a perspective view of an optical system with four movable mirror surfaces 2, 5, 7, 8 and a deflection unit 6. The deflection unit 6 has two mirror surfaces. The four movable mirror surfaces and the beam deflection unit 6 are arranged in the beam path 15 such that a first movable mirror surface 2, a second movable mirror surface 5, the beam deflection unit 6, a third movable mirror surface 7, and a fourth movable mirror surface 8 are arranged in the beam path.

[0049] Each of the four movable mirror surfaces 2, 5, 7, 8 has at least two functional areas. For example, the first mirror surface 2 has a first functional area 3 and a second functional area 4. The fourth movable mirror surface, for example, has a first functional area 9 and a second functional area 10. The functional areas 3, 4, 9, 10 of the first 2 and fourth movable mirror surfaces 8 are designed such that they each jointly produce a specific finite focal length. The functional areas of the second 5 and third movable mirror surfaces 7 are designed such that they each jointly produce a specific finite focal length.

[0050] The functional areas can be designed in such a way that an image plane and an object plane are constant, regardless of whether the first functional areas or the second functional areas are arranged in the beam path.

[0051] It is also possible to realize the optical structure with the properties described above without a deflection unit 6 or with a differently designed deflection unit.

[0052] Figure 4 shows the structure of the Figure 3 in a frontal view. The object-side 16 and image-side sections 17 of the optical axis are perpendicular to the viewing plane. Figure 4a the structure with the four movable mirror surfaces 2, 5, 7, 8 is shown in the first position in each case, in which the first functional areas 3, 9 are arranged in the beam path 15. Figure 4bshows the structure with the four movable mirror surfaces 2, 5, 7, 8 in the respective second positions in which the respective second functional areas 4, 10 are arranged in the beam path 15. The displacement from the respective first to the respective second displacement position takes place for the first and fourth movable mirror surfaces 2, 8 with the same amount along a first direction 25. The displacement from the respective first to the respective second position takes place for the second and third movable mirror surfaces 5, 7 with the same amount along a second direction 26. In Figure 4The first direction 25 and the second direction 26 are opposite. Furthermore, the position of the object-side portion of the optical axis 16, i.e., the distance 32 from an origin 33 of a global coordinate system, remains constant regardless of the position. Furthermore, the position of the image-side portion of the optical axis 17, i.e., the distance 31 from the origin 33 of a global coordinate system, remains constant regardless of the position.

[0053] Figure 5 shows the structure of the Figure 3 and 4 in a side view. List of reference symbols:

[0054] 1 optical system 2 first movable mirror surface 3 first functional area of ​​the first movable mirror surface 4 second functional area of ​​the first movable mirror surface 5 second movable mirror surface 6 beam deflection unit 7 third movable mirror surface 8 fourth movable mirror surface 9 first functional area of ​​the fourth movable mirror surface 10 second functional area of ​​the fourth movable mirror surface 11 object plane 12 image plane 15 beam path 16 object-side section of the optical axis 17 image-side section of the optical axis 20 (first) substrate 21 second substrate 25 displacement path 25 a first displacement direction 25 b second displacement direction 25 c third displacement direction 26 displacement path 31 position of the image-side optical axis 32 position of the object-side optical axis 33 origin of a coordinate system 35 angle between optical axis and mirror surface 36Deflection mirrors

Claims

1. A reflective optical system (1) with an adjustable effective focal length, comprising at least two displaceable mirror surfaces (2, 8) arranged off-axis and one after the other along a beam path (15) of the optical system (1) and each displaceable from a first displacement position to a second displacement position, wherein - in the first displacement position, first functional regions (3, 9) of the displaceable mirror surfaces (2, 8) are arranged in the beam path (15), and the first functional regions (3, 9) are designed such that they jointly produce a first finite focal length; and - in the second displacement position, second functional regions (4, 10) of the displaceable mirror surfaces (2, 8) are arranged in the beam path (15), and the second functional regions (4, 10) are designed such that they jointly produce a second finite focal length;wherein the mirror surfaces (2, 8) are arranged in each displacement position such that object-side and image-side sections (16, 17) of the optical axis of the optical system are each fixed independently of the displacement position; 2. Optical system (1) according to the preceding claim, wherein displaceable mirror surfaces (2, 8), whose functional regions (3, 4, 9, 10) together effect a focal length, are arranged together on a single substrate (20), wherein the substrate (20) is displaceable relative to the beam path.

3. Optical system (1) according to one of the preceding claims, wherein the mirror surfaces (2, 5, 7, 8) are shaped and arranged such that two light beams which pass through an object point in an object plane (11) spaced from the object-side section of the optical axis (16), and immediately thereafter pass through the optical system (1) with mirror surfaces in the first displacement position, have a point of intersection at a first image point in an image plane (12); and two light beams which pass through the same object point in the object plane (11) spaced from the object-side section of the optical axis (16), and immediately thereafter pass through the optical system (1) with mirror surfaces in the second displacement position, have a point of intersection at a second image point in the image plane (12).

4. Optical system (1) according to one of the preceding claims, comprising four displaceable mirror surfaces (2, 5, 7, 8) and a beam deflection unit (6), wherein the first (2) and the fourth displaceable mirror surface (8) are arranged jointly on a first substrate (20), and the second (5) and the third displaceable mirror surface (7) are arranged jointly on a second substrate (21), wherein the first displaceable mirror surface (2), the second displaceable mirror surface (5), the beam deflection unit (6), the third displaceable mirror surface (7) and the fourth displaceable mirror surface (9) are arranged one after the other in the beam path (15), wherein the first (2) and the fourth displaceable mirror surface (8) have functional regions (3, 4, 9, 10) which each jointly effect certain focal lengths, and the second (5) and the third displaceable mirror surface (7) have functional regions which each together produce certain focal lengths.

5. Optical system (1) according to one of the preceding claims, wherein each mirror surface encloses an angle of 45° with the optical axis.

6. Optical system according to one of the preceding claims, wherein a displacement path along which a displaceable mirror surface is displaceable from the first to the second displacement position is linear and preferably along a direction lying within that displaceable mirror surface and / or is orthogonal to the optical axis.

7. Optical system according to one of the preceding claims, wherein displacement paths along which two displaceable mirror surfaces, which together effect a focal length, can be displaced from the first to the second displacement position, are rectified and / or of equal magnitude.

8. Optical system according to one of the preceding claims, wherein at least one of the mirror surfaces is designed as a freeform which can be described by a basic description, in particular spherical, elliptical, aspherical, parabolic or hyperbolic, with higher-order terms, in particular Zernike polynomials.

9. Optical system according to one of the preceding claims, wherein at least one of the mirror surfaces has an aperture which can be used as a reference for checking the position and orientation of the mirror surfaces relative to one another.

10. Optical system according to one of the preceding claims, wherein at least one optical reference is arranged on at least one of the displaceable mirror surfaces or at least one substrate.

11. Optical system according to one of the preceding claims, wherein a mechanical reference and / or contact structure is arranged in an assembled or machined manner on at least one of the displaceable mirror surfaces or at least one substrate.

12. Optical system according to one of the preceding claims, wherein the reflectivity of the mirror surfaces for light having a wavelength between 400 nm and 800 nm is greater than 50%, particularly advantageously greater than 75%, most advantageously greater than 90%.

13. Optical structure, comprising an optical system according to the preceding claims and at least one imaging optical system, in particular a telescope or a microscope, wherein the optical system is integrated into the imaging optical system or is connected upstream or downstream of the imaging optical system.