Reflective optical system with adjustable effective focal length and optical design

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

The invention relates to a reflective optical system with adjustable effective focal length, to the use of such a reflective optical system, and to a method for calculating the mirror surfaces for such an optical system.Adjustable focal length optical systems can be used in both illumination and imaging systems. The former enables the solution to be used for beam shaping tasks, for example for shaping laser beams in laser material processing. In imaging optical systems, variable focal length optical systems can be used such that at least two different object fields are imaged in two states onto a common, fixed image plane.In the prior art, refractive optical systems with adjustable focal length are known in particular. The publications U.S. Pat. No. 3,507,565 A and U.S. Pat. No. 3,305,294 A describe, for example, lens systems having a variable focal length. In these solutions, consisting of a lens pair, a variation of the focal length is achieved by an opposing lateral but equal-amount movement.Refractive systems, however, have low transmission, high chromatic dependence of aberrations and physical limitation of surface complexity, for example by total internal reflections.The publication DE 10 2010 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 as 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, a first and a second optical element are described, 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 at least a first angle and a second angle different from the first depending on the electrical circuit state. This electrically effected change in the beam path realizes a discretely switchable focal length change.US 2018 / 0164573 A1 discloses an anastigmat telescope having three aspherical mirrors, comprising means for linearly moving the third mirror along the optical axis of the telescope 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.In addition, US 2015 / 0234153 A1 describes a varifocal reflective lens configured to change a focal length using an electric signal, the lens including 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, a shape of the electrically active polymer layer is changed by the electric 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 a reflected light.It is therefore an object of the invention to provide an optical system which eliminates the disadvantages of such prior art systems and enables low chromatic aberrations.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 developments according to the invention.The concept of adjustable effective focal lengths is transferred to a reflective application which, in addition to a continuous focal length, also permits a discretely adjustable focal length.According to the invention, a reflective optical system with adjustable effective focal length is proposed. The reflective optical system has at least two displaceable mirror surfaces which are arranged off-axis and one after the other along an optical path of the optical system. The displaceable mirror surfaces can each be displaced from a first displacement position, hereinafter also referred to merely as first position, into at least one second displacement position, hereinafter also referred to as second position.In the first position, first functional regions of the displaceable mirror surfaces are arranged in the beam path. The first functional regions are designed according to the invention such that they together bring about a first finite focal length.In the second position, second functional regions of the displaceable mirror surfaces are arranged in the beam path. The second functional regions are designed such that they together bring about a second, deviating, finite focal length. Thereby, the effective focal length of the optical system having the displaceable mirror surfaces in the first position is different from the effective focal length of the optical system having the displaceable mirror surfaces in the second position.According to the invention, the mirror surfaces are arranged in any position in such a way that object- and image-side sections of the optical axis of the optical system are fixed independently of the position. This means that the beam position at the input and output of the optical system is constant irrespective of the position of the mirrors. In other words, the optical system has exactly one input / output channel through which light beams 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 as a result by a displacement of the displaceable mirror surfaces from the first position into the second position.This can be achieved, for example, by compensating a changed beam position, which occurs within the optical system as a result of a displacement and / or tilting of one of the displaceable mirror surfaces, by a suitable displacement and / or tilting of the other displaceable mirror surface. It is also possible to shift each of the displaceable mirrors in such a way that the beam position does not change even within the optical system.The optical system according to the invention can be designed in particular such that it has a plurality of positions. The mirror surfaces can be designed in particular such that they allow the effective focal lengths to be adjusted in an equally discrete or continuous manner.The application is not limited to specific wavelength ranges and conceptually allows an application from the UV to the IR wavelength range. An application can be made for terrestrial as well as for extra-terrestrial applications. An application in simple microscope optics is also conceivable according to the invention for imaging with different focal lengths as a continuous or discrete system. Compared to the prior art, the solution presented does not represent the complete telescope, but can be correspondingly coupled to different types of telescope. In general, an independent application of the beam-forming assembly without additional telescope is also conceivable. The arrangement as a relay system and also downstream of the telescope is possible.In an advantageous embodiment of the optical system, displaceable mirror surfaces, the functional regions of which together effect a focal length, are preferably arranged jointly on a single substrate, wherein the substrate is displaceable with respect to the beam path.In a further advantageous configuration of the optical system, the mirror surfaces are shaped and arranged in such a way that two light beams which pass through an object point in an object plane which is spaced apart from the object-side section of the optical axis and directly follow the optical system with mirror surfaces in the first position have an intersection point in a first image point in an image plane; and two light beams which pass through the same object point in the object plane which is spaced apart from the object-side section of the optical axis and directly follow the optical system with mirror surfaces in the second position have an intersection point in a second image point in the image plane. In other words, the displaceable mirror surfaces and their functional regions are designed and arranged in such a way that an object which is arranged in an object plane is imaged onto a single image plane. Here, the magnification factor of an image caused by the optical system having mirror surfaces in the first position is different from the magnification factor of the image caused by the optical system having mirror surfaces in the second position.In a particularly advantageous embodiment of the optical system, the system has four or more displaceable mirror surfaces, advantageously an even number. The larger number of displaceable mirror surfaces each having at least two functional regions enables a plurality of finite focal lengths, which are effected by the functional regions arranged in the beam path, to be coordinated with one another in a targeted manner. In this case, in particular the focal lengths which are effected in the different positions can be matched to one another in such a way that the object and image planes are fixed at different magnification factors. Such a construction can therefore simplify, for example, the realization of the above-described fixed object and image planes at different magnifications. In this case, the first and the fourth displaceable mirror surfaces can be arranged jointly on a first substrate. Independently, the second and third displaceable mirror surfaces can be arranged jointly on a second substrate. In addition, a beam deflection unit can be provided in such a structure. Under a beam deflection unit, each element can be viewed that deflects a light beam by a specific angle. Particularly advantageous are beam deflection units which are designed as retroreflectors and can deflect the light beam by 180°.Preferably, the first displaceable mirror surface, the second displaceable mirror surface, the beam deflection unit, the third displaceable mirror surface and the fourth displaceable mirror surface are arranged one after the other in the beam path. The mirror surfaces are configured such that the first and the fourth displaceable mirror surfaces have functional regions which each jointly effect specific focal lengths, and the second and the third displaceable mirror surfaces have functional regions which each jointly effect specific focal lengths.In particularly advantageous embodiments of the invention, at least one, preferably two, particularly preferably each of the displaceable mirror surfaces encloses an angle of 45° with the optical axis. This can mean, in particular, that the vertices of the displaceable mirror surfaces enclose an angle of 45° with the optical axis. It is very particularly advantageous if the beam path is deflected by 45° by reflection on the mirror surfaces.In further advantageous embodiments of the invention, the optical system has a displacement path along which a displaceable mirror surface is displaceable from the first into the second position. The displacement path is advantageously linear and preferably extends along a direction which lies within that displaceable mirror surface which is displaceable along the displacement path and / or is orthogonal to the optical axis. This makes it possible in a particularly simple manner to ensure that the beam position is not changed by a displacement of the mirror surfaces along the displacement path.It can be particularly advantageous if displacement paths along which two displaceable mirror surfaces, the functional surfaces of which together effect a focal length, can be displaced from the first into the second position are in the same direction and / or have the same amount.In very particularly advantageous embodiments of the invention, at least one of the mirror surfaces is designed as a free form which can be described by a basic description with terms of higher order. The basic description can be spherical, elliptical, aspherical, parabolic or hyperbolic in particular. The higher order terms may advantageously be Zernike polynomials. The free form is in particular configured in such a way that it forms the above-described functional regions of the mirror surfaces.The production of free-formed mirrors also enables the exact referencing by optical sub-apertures and mechanical contact structures on the monolithic optical unit, which can be produced with the optical mirror surface in one working step and thus simplifies an adjustment and enables it with high accuracy.In further advantageous configurations, at least one of the mirror surfaces has an aperture which can be used as a reference for checking the position and position of the mirror surfaces with respect to one another. The aperture can be formed as a region in the free shape of the mirror surface. Advantageously, an additional reflective surface can be integrated on one of the mirror surfaces, wherein the additional reflective surface takes over the task of controlling the position and position. This can also be correspondingly integrated into the free form.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. In addition, in advantageous embodiments of the invention, mechanical references and / or mechanical contact structures can be arranged in an assembled or machined manner on at least one of the optical components.In a further embodiment of the invention, at least one refractive element is arranged in the beam path of the optical system. This may be particularly useful for applications with a narrow wavelength range in which chromatic aberrations do not play a great role.In particularly advantageous configurations, the reflectivity of the mirror surfaces is greater than 90%, preferably greater than 95%, at a wavelength which is greater than or equal to 900 nm and / or a wavelength which is between 300 nm and 900 nm and / or a wavelength which is less than or equal to 300 nm. 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. Advantageously, the reflectivity of the mirror surfaces for light having a wavelength in a wavelength range between 400 nm and 800 nm is greater than 50%, particularly advantageously greater than 75%, very particularly advantageously greater than 90%. The reflectivity in the entire range between 400 nm and 800 nm, or even only in a partial range between 400 nm and 800 nm that is 5 nm, advantageously 50 nm, particularly advantageously 100 nm wide, can be greater than 50%, particularly advantageously greater than 75%, very particularly advantageously greater than 90%.According to the invention, an optical structure is proposed, comprising an optical system described above and at least one imaging optical system, in particular a telescopic optical unit or a microscope optical unit, wherein the optical system is integrated into the imaging optical system or is connected upstream or downstream of the imaging optical system. By displacing the mirror surfaces into the different displacement positions, in particular the magnification factor of the overall system can be changed.According to the invention, a method for calculating surface shapes of the displaceable mirror surfaces for the optical system with two effective focal lengths as described above is likewise provided, comprising the steps:defining an optimization parameter / target (for example. Wavefront Criterion, RMS Spot Radius, MTF) for the systemdefining the geometric boundary conditions:defining distances and angles between the mirror surfaces, the distances being defined in the direction of the beam path as well as laterally to the beam path,◯ defining the displacement path of the displaceable mirror surfaces,• Defining the diameter of the mirror surfacesdefining the optical boundary conditions:◯ Defining Application Wavelength(s) defining the effective focal length and / or achievable magnification factors of the optical system and the consequent definition of object and image field(s) and numerical apertures for both configurations,• defining the pupil position and size,• Defining the basic description and the associated core properties (for example. Surface curvature, conic constant, aspherical coefficients),defining the mathematical description to be used for the free-form surfaces,setting the power distribution for the mirror surfaces (converging, diverging)Optionally more accurate definition of the relative surface position of the free forms (for example of the surface vertices).Such a method may be performed with available optics design and / or optimization tools. Of course, the method described above can be extended to any number of effective focal lengths or achievable magnifications with a fixed object and image plane.The subject matter according to the invention is intended to be explained in more detail on the basis of the following figures and examples without wishing to restrict it to the embodiments shown herein.It shows: FIG. 1 shows a schematic illustration of an embodiment of an optical system according to the invention in two positions. FIG. 2 shows a substrate with two mirror surfaces of an optical system according to the invention. FIG. 3 shows a perspective view of a further embodiment of the optical system according to the invention. FIG. 4 shows the embodiment of the optical system according to the invention of FIG. 3 in two positions. FIG. 5 shows the embodiment of the optical system according to the invention from FIG. 3 in a side view. FIG. 6 shows a schematic illustration of a further embodiment of an optical system according to the invention in two positions.FIG. 1 shows a schematic illustration 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 form an angle with the beam path 15 and are arranged one after the other along the beam path 15. FIG. 1 shows the optical system 1 according to the invention in two different states: in FIG. 1 a) both displaceable mirror surfaces 2, 8 are each in a first position. In FIG. 1 b), both displaceable mirror surfaces 2, 8 are each arranged in a second position.Each of the displaceable mirror surfaces 2, 8 has two respective functional regions: the first displaceable mirror surface 2 has a first functional region 3 and a second functional region 4. The second displaceable mirror surface 8 has a first functional region 9 and a second functional region 10.If the first mirror surface 2 is in the first position, the first functional region 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 region 4 of the first displaceable 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 region 9 of the second mirror surface is arranged in the beam path 15 of the optical system. In the second position of the second mirror surface 8, the second functional region 10 is arranged in the beam path 15 of the optical system.The functional regions of the displaceable mirror surfaces are each designed such that they together bring about a finite focal length. In other words, light beams incident parallel to the optical axis are subsequently reflected by the first functional region 3 of the first displaceable mirror surface 2 and are subsequently reflected by the first functional region 9 of the second displaceable mirror surface 8, focused on a first focus located on the image-side portion of the optical axis. Light rays incident parallel to the optical axis, then reflected by the second function region 4 of the first displaceable mirror surface 2 and then reflected by the second function region 10 of the second displaceable mirror surface 8, are focused on a second focus located on the image-side portion of the optical axis. In principle, more than two functional regions per mirror surface are possible, so that more than two finite focal lengths can be effected.According to the invention, the displaceable mirror surfaces 2, 8 are displaceable from their respective first position into their respective second position. A displacement path, i.e. the path along which one of the displaceable mirror surfaces can be guided from its first position into the second position, can be straight, for example. Embodiments are also possible in which the displaceable mirror surfaces 2, 8 are each displaceable in more than two positions or continuously. Such further positions can be arranged, for example, at different locations along the displacement path between the first and second positions. At least one or all of the displaceable mirror surfaces 2, 8 can / can be guided, for example, on a linear guide or a joint mechanism / solid state mechanism.According to the invention, the mirror surfaces are arranged in any position in such a way that a beam position at the input and output of the optical system remains unchanged. That is, the mirror surfaces are arranged at the first and second positions so that object-side optical axis portions 16 and image-side optical axis portions 17 are fixed.In the embodiment of FIG. 1, this is achieved, for example, by the mirror surfaces being arranged in such a way that both the point in the beam path at which the beam path impinges on a displaceable mirror surface or one of the functional regions of the mirror surface and the angle between the incident and the emerging beam path are the same in each position. Embodiments are also conceivable in which the rules described above can be deviated. Since two displaceable mirror surfaces are provided according to the invention, a positional deviation, which is generated by a displacement or else a tilting of one mirror, can be compensated by a corresponding displacement or else tilting of the other mirror.Embodiments are possible, for example, in which the location in the beam path at which a displaceable mirror surface is arranged differs between the first and second positions. Such an embodiment is shown, for example, in FIG. 6. In this embodiment, however, the offset of the beam path resulting therefrom can be compensated by the second displaceable mirror surface.FIG. 1 bshows, by way of example, a first displacement direction 25 awhich indicates the direction in which both displaceable mirror surfaces 2, 8 can be displaceable from their respective first into the respective second position. Alternatively or additionally, the displaceable mirror surfaces can also be displaceable in the direction of a second displacement direction 25 b. The second displacement direction is perpendicular to the plane of the drawing in FIG. 1 b. The displacement direction can be effected, for example, within the mirror plane or perpendicular to the perpendicular of the mirror surface.An optical system according to the invention can have, in addition to the at least two displaceable mirror surfaces 2, 8, also further mirror surfaces or other optical elements. Each of the further mirror surfaces or each of the other optical elements can be arranged displaceably or else fixedly. In the embodiment of FIG. 1, the optical system has a deflection mirror 36. The deflecting mirror 36 is arranged immovably. The deflecting mirror 36 is arranged in the beam path between the first displaceable mirror surface 2 and the second displaceable mirror surface 8.In addition, it is possible to combine a plurality of the arrangements described above, each having two displaceable mirror surfaces, with one another. By way of example, a combination of two arrangements with in each case two displaceable mirror surfaces is illustrated below. It is also possible to combine the arrangement described above with any desired number of displaceable mirror surfaces.FIG. 2 shows a perspective view of a single substrate 20 on which two displaceable mirror surfaces 2, 8, the functional regions of which in each case jointly bring about a finite focal length, are arranged. As a result, movements of the two displaceable mirror surfaces 2, 8 are necessarily mechanically coupled to one another. In particular, the functional regions can be arranged within the displaceable mirror surfaces 2, 8 in such a way that in each case first and second functional regions of the mirror surfaces 2, 8 are spaced apart from one another in the same direction and amount. In this way, it can be ensured, for example, that, in the event of a displacement of the substrate, first functional regions are arranged in the beam path in each case or second functional regions are arranged in the beam path in each case. This can make the optical arrangement more robust with respect to external disturbances. The construction of the overall system can likewise be simpler.FIG. 3 shows a perspective view of an optical system having four displaceable mirror surfaces 2, 5, 7, 8 and a deflection unit 6. The four displaceable mirror surface and the beam deflection unit 6 are arranged in the beam path 15 in such a way that a first displaceable mirror surface 2, a second displaceable mirror surface 5, the beam deflection unit 6, a third displaceable mirror surface 7 and a fourth displaceable mirror surface 8 are arranged in succession in the beam path.Each of the four displaceable mirror surfaces 2, 5, 7, 8 has at least two functional regions. For example, the first mirror surface 2 has a first functional region 3 and a second functional region 4. The fourth displaceable mirror surface has, for example, a first functional region 9 and a second functional region 10. The functional regions 3, 4, 9, 10 of the first 2 and fourth displaceable mirror surfaces 8 are configured such that they each together bring about a specific finite focal length. The functional regions of the second 5 and third displaceable mirror surfaces 7 are configured such that they each together effect a specific finite focal length.The functional regions can be designed in such a way that an image plane and an object plane are constant irrespective of whether the respective first functional regions or the respective second functional regions are arranged in the beam path.It is also possible to realize the optical structure having the above-described properties without a deflection unit 6 or with a deflection unit of a different configuration.FIG. 4 shows the structure of FIG. 3 in a front view. The object-side 16 or image-side sections 17 of the optical axis are perpendicular to the plane of view. FIG. 4 ashows the structure with the four displaceable mirror surfaces 2, 5, 7, 8 in the respective first position, in which the respective first functional regions 3, 9 are arranged in the beam path 15. FIG. 4 bshows the structure with the four displaceable mirror surfaces 2, 5, 7, 8 in the respective second positions in which the respective second functional regions 4, 10 are arranged in the beam path 15. The displacement from the respective first to the respective second displacement positions takes place here in the same amount along a first direction 25 for the first and fourth displaceable mirror surfaces 2, 8, The displacement from the respective first to the respective second position takes place here in the same amount along a second direction 26 for the second and third displaceable mirror surfaces 5, 7. Furthermore, the position of the object-side section of the optical axis 16, i.e. the distance 32 from an origin 33 of a global coordinate system, remains constant independently of the position. In addition, the position of the image-side section of the optical axis 17, i.e. the distance 31 from the origin 33 of a global coordinate system, remains constant independently of the position.FIG. 5 shows the structure of FIGS. 3 and 4 in a side view.List of reference numbers:1 Optical system 2 First displaceable mirror surface 3 First functional region of the first displaceable mirror surface 4 Second functional region of the first displaceable mirror surface 5 Second displaceable mirror surface 6 Beam deflection unit 7 Third displaceable mirror surface 8 Fourth displaceable mirror surface 9 First functional region of the fourth displaceable mirror surface 10 Second functional region of the fourth displaceable 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 aFirst displacement direction 25 bSecond displacement direction 25 cThird 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 36 Deflection mirror

Claims

Reflective optical system (1) with adjustable effective focal length, having at least two displaceable mirror surfaces (2, 8) which are arranged off-axis and one after the other along an optical path (15) of the optical system (1) and are each displaceable from a first displacement position into a second displacement position, wherein - in the first displacement position, in each case first functional regions (3, 9) of the displaceable mirror surfaces (2, 8) are arranged in the optical path (15), and the first functional regions (3, 9) are designed such that they jointly bring about a first finite focal length; and - in the second displacement position, in each case second functional regions (4, 10) of the displaceable mirror surfaces (2, 8) are arranged in the optical path (15), and the second functional regions (4, 10) are designed such that they jointly bring about 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.Optical system (1) according to the preceding claim, wherein displaceable mirror surfaces (2, 8), the functional regions (3, 4, 9, 10) of which together effect a focal length, are arranged jointly on a single substrate (20), wherein the substrate (20) is displaceable with respect to the beam path.The optical system (1) according to any 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 subsequently pass through the optical system (1) with mirror surfaces in the first displacement position have an intersection point in 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 subsequently pass through the optical system (1) with mirror surfaces in the second displacement position have an intersection point in a second image point in the image plane (12).Optical system (1) according to one of the preceding claims, having 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 successively in the beam path (15), wherein the first (2) and the fourth displaceable mirror surface (8) have functional regions (3, 4, 9, 10) which respectively effect jointly determined focal lengths, and the second (5) and the third displaceable mirror surface (7) have functional regions which respectively effect jointly determined focal lengths.The optical system (1) according to any of the preceding claims, wherein each mirror surface includes an angle of 45° with the optical axis.The optical system according to any of the preceding claims, wherein a displacement path along which a displaceable mirror surface is displaceable from the first to the second displacement position extends linearly and preferably along a direction lying within that displaceable mirror surface and / or is orthogonal to the optical axis.Optical system according to one of the preceding claims, wherein displacement paths along which two displaceable mirror surfaces which together effect a focal length are displaceable from the first into the second displacement position are the same in direction and / or amount.Optical system according to one of the preceding claims, wherein at least one of the mirror surfaces is designed as a free form which can be described by a basic description, in particular spherical, elliptical, aspherical, parabolic or hyperbolic, with terms of higher order, in particular Zernike polynomials.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 position of the mirror surfaces with respect to one another.The optical system according to any 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.Optical system according to one of the preceding claims, wherein a mechanical reference and / or bearing structure is arranged on at least one of the displaceable mirror surfaces or at least one substrate in a mounted or worked manner.Optical system according to one of the preceding claims, wherein the reflectivity of the mirror surfaces for light with a wavelength between 400 nm and 800 nm is greater than 50%, particularly advantageously greater than 75%, very particularly advantageously greater than 90%.Optical assembly, 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.

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