WO2014128065A1

WO2014128065A1 - Device for changing a beam profile of an incident light beam, more particularly beam expander

Info

Publication number: WO2014128065A1
Application number: PCT/EP2014/052967
Authority: WO
Inventors: Martin Berz
Original assignee: Martin Berz
Priority date: 2013-02-25
Filing date: 2014-02-14
Publication date: 2014-08-28
Also published as: DE102013101856B4; DE102013101856A1

Abstract

The invention relates to a device for changing a beam profile of an incident light beam, more particularly a beam expander, comprising: a first D‑mirror; and an element for changing an optical anisotropy of the light beam, wherein the first D‑mirror and the element for changing an optical anisotropy of the light beam are arranged such that either the incident light beam firstly impinges on the first D‑mirror and is then directed from the first D‑mirror onto the element for changing an optical anisotropy of the light beam or the incident light beam firstly impinges on the element for changing an optical anisotropy of the light beam and is then directed from the element for changing an optical anisotropy of the light beam onto the first D‑mirror.

Description

Device for changing a beam profile of an incident light beam,

in particular beam expander

The invention relates to a device for changing a beam profile of an incident light beam, in particular a beam expander (English: beam expander). By a beam expander, for example, one can understand an optical device which serves to increase the diameter of a parallel incident light beam. If the beam expander is used in the reverse direction, a beam reduction takes place. The term beam expander is therefore used both for beam expansion and for beam reduction. Telescopes, for example, also fall under the concept of beam expander.

The change of the beam profile of an incident light beam to be effected by the device can in particular cause an enlargement or reduction of the beam diameter or the beam waist. This may be, for example, a change in the beam waist along a spatial direction. Further, this may also be, for example, a change in the beam waist along two orthogonal spatial directions, i. a change in the entire beam waist. Preferably, the change can also be that an optical anisotropy of the incident light beam is changed. The optical anisotropy of the incident light beam may be, for example, an optical anisotropic distribution of the light intensity around an optical axis. For example, a change in the optical anisotropy of the incident light beam may be a rotation of the distribution of light intensity about an optical axis.

The known in the art beam expander generally have a comparatively long length compared to the beam diameter used. Furthermore, high quality and therefore expensive optics are usually used. At the same time, prior art beam expanders typically do not use specular elements.

It is therefore an object of the present invention to provide a device for changing a beam profile, in particular a beam expander, which is inexpensive to manufacture and has a compact construction. The invention relates to a device for changing a beam profile of an incident light beam, in particular a beam weiterweiter, comprising: a first D mirror; and an optical anisotropy element of the light beam, wherein the first D mirror and the optical anisotropy changing element of the light beam are arranged such that either the incident light beam first strikes the first D mirror and then from the first D Mirror is directed to the element for changing an optical anisotropy of the light beam or the incident light beam first strikes the element for changing an optical anisotropy of the light beam and is then directed by the element for changing an optical anisotropy of the light beam to the first D mirror ,

For example, a D-mirror may be understood as a dispersive mirror, that is, an optical device having at least one reflective element and at least one dispersive element, such as a dielectric medium.

In the following an example is considered which should illustrate a simple variant of a D-mirror. For this purpose, it is assumed that the D mirror has mirror elements arranged side by side in a dielectric medium. It should be emphasized that the invention has contributed to the knowledge that, in particular for vertical incidence of the light beam on the D mirror, the shading between adjacent mirror elements of the D mirror is substantially reduced if between an incident surface of the D mirror and the Mirror elements is a non-air dielectric, or in other words, if the beam path of the light beam between the entrance to the D mirror and the exit from the D mirror in a non-air-dielectric. This will be illustrated with reference to FIG.

For this purpose, it is assumed that the light beam is perpendicular to a horizontal light entrance surface of the D-mirror and that the mirror elements are identical plane and oblong mirrors, whose longitudinal axes are horizontal, i. perpendicular to the plane of the drawing of Figure 1, and seen vertically, i. along the top-bottom direction of the drawing plane, at the same height.

First, the case illustrated in FIG. 1A is explained, in which a D mirror without dielectric is depicted. In this case, since there is no boundary layer between air and the dielectric, the air-dielectric barrier layer shown in FIG If viewed as the light incident surface 1 01 of the case shown in Figure 1 A case. To illustrate this difference of Figure 1 A and Figure 1 B, the light incident surface 0101 in Figure 1 A is shown by dashed lines.

A first light beam 1 03 hits in this case vertically, that is at an angle γ of 90 °, on the light incident surface 1 O l, then strikes a first mirror element 1 05, is then reflected by this first mirror element 1 05 and in an expiring Direction directed. Here, the light beam forms 1 03 with the light incident surface 1 01 an angle ε and the mirror surface of the first mirror element 1 05 with the light incident surface 1 01 an angle of

A second mirror element 1 07, whose mirror surface is parallel to the mirror surface of the first mirror element 1 05, is arranged at a given distance from the first mirror element 1 05 to the outgoing direction. A second beam 1 09, which in comparison to the first beam 1 03 continues to the outgoing direction to the first mirror element 1 05 hits, as well as the first beam 1 03 at the same angle ε directed in the outgoing direction. This second beam 1 09 hits at landing point 1 1 1 of the boundary beam on the first mirror element 1 05. He is a so-called boundary beam, i. that this beam is still directed in the outgoing direction and is not blocked by the second mirror element 1 07, but that each beam that strikes farther to the right of the impingement point 1 1 1 on the first mirror element 1 05, is blocked by the second mirror element 1 07 or in the event that this beam hits neither the first mirror element 1 05 nor the second mirror element 1 07, is lost between the mirror elements. Thus, all the light rays which lie between the impact point 1 1 1 and the left edge of the second mirror element 1 07, shadowed, i. they are either blocked by the second mirror element 1 07 or they do not meet at all on a mirror element. The ratio of the shaded light to the light incident on the solar collector may be determined geometrically by the ratio of the length from the left edge of the first mirror element 105 to the point of impact 1100 to the length from the left edge of the first mirror element 105 a projection point 1 1 3, at which an exactly on the left edge of the second mirror element 1 07 vorbeifallender beam would fall on a fictitious vertical extension of the first mirror element 1 05, are calculated.

In contrast, the constellation shown in Figure 1 B with a Dielectric, in particular a liquid dielectric, significant advantages. In each case the situations with identical incidence and angle of departure are compared. In this case, with dielectric, a first beam 1 03 hits perpendicular to the light incident surface 01, where it is not broken due to the vertical incidence and then strikes the first mirror element 1 05. On both sides of the light incident surface 01 01 shown in this case as a solid line the respective refractive index of the medium is shown in FIG. 1B. Above the light incident surface 1 01, the medium in which the incident beam passes has a refractive index n _η . In the case of air, the value of the refractive index n _{η is} almost equal to 1. Below the light incident surface 1 01, the medium has a refractive index n ₂ greater than 1.

The first beam 1 03 is reflected back to the reflection of the first mirror element 1 05 to the air-dielectric interface, where the light is refracted and directed in the outgoing direction. Due to the refraction at the air-dielectric interface after the reflection at the mirror this can be made much flatter than in the case without dielectric, ie, that the angle δ ₂ between the first mirror element 1 05 and the light incident surface 1 01 smaller than the corresponding angle of the case shown in Figure 1A. The second beam 1 09 is a boundary beam as in FIG. 1A. It can be clearly seen that the impact point 1 1 1 is substantially closer to the right edge of the first mirror element 1 05 than in the case of Figure 1 A. This means that the shading in the case shown in Figure 1 B is much lower than in the case of Figure 1 A.

In summary, it should be noted that, for the case of identical mirror elements arranged parallel to one another with identical lateral spacing and equal angles of incidence and reflection, a D mirror with mirror elements located in a dielectric has significantly reduced shading. Typical shading values for the dielectric and dielectric case are 90% and 25%, respectively. For these values, the D-mirror with dielectric has a shading factor reduced by a factor of 3.6. This corresponds to a factor of 7.5 higher transmission.

For example, a D mirror may include a dielectric medium having a light incident surface. The dielectric medium may have a refractive index greater than 1.05. The refractive index of the dielectric medium may be, for example, greater than 1.2. For example, the refractive index of the dielectric medium may be greater than 1 .3 be. For example, the refractive index of the dielectric medium may be greater than

1 .32. For example, the refractive index of the dielectric medium may be greater than

1 .33. For example, the refractive index of the dielectric medium may be greater than

1 .4. If the refractive index differs only slightly from 1, this leads to a small reduction of shading. If the refractive index differs more than 1, this leads to a greater reduction in shading.

By the expression that a medium has a refractive index greater than a certain value, it can be understood, for example, that the medium has a refractive index greater than the predetermined value at each point of its matter and in each direction at that point. In general, normal pressure is assumed here.

A dielectric or a dielectric medium is used to denote a dielectric other than air.

The dielectric medium may consist of a liquid, a gel and / or a solid. Furthermore, the dielectric medium may comprise at least one liquid, a gel and / or a solid.

In this case, the medium may have a solid in which a plurality of adjacently arranged cavities or tubes are arranged, in which elongated mirror elements are rotatably mounted or arranged either in a liquid, in a gel or in another solid, in particular with a cylindrical shape. The cylinder shapes may be laterally connected to motorized rotary devices.

Furthermore, the interface between the solid and the further solid to avoid or reduce reflection losses may be filled with a particular liquid or gel-like bridging dielectric. It is preferred that in this case both solids have an identical or similar refractive index as the bridging dielectric. The medium here is formed in total by the solid, the bridging dielectric as well as the liquid, the gel or the further solid. The intermediate medium is designed such that it can also be used as a lubricant for the mirror cylinder. A thickness of a thin intermediate layer may, for example, be between 0.2 and 20 μm, preferably between 0.5 and 10 μm / m, so that differences in the refractive index do not lead to reflection losses. For both solids, the synthetic, glass-like thermoplastic polymethylmethacrylate is preferred here, which is colloquially called acrylic glass or Plexiglas and is referred to by the abbreviation PMMA.

A general advantage of solids is that some solid bodies are almost perfectly transparent in the infrared and in the UV, in contrast to liquid, dielectric materials.

The rotatable cylinder contains in the spatial diagonal flat mirror for reflecting the incident light beam. The cylinder is rotatable and the tubes can be used for the mirror mount.

The dielectric medium may comprise at least one of the following materials: an optically isotropic material, an optically anisotropic material, an optically nonlinear material, or a birefringent material. The birefringent material in particular has the Pockels effect or the linear electro-optical effect, in which the refractive index changes linearly with an applied electric field.

In this case, the refractive index can be, for example, a location-dependent and / or direction-dependent refractive index. The refractive index can be, for example, a location-independent and / or direction-independent refractive index. In the case of nonmagnetic materials, the square of the refractive index n is equal to the permittivity number or dielectric constant £ _r .

The advantage of a locally variable refractive index is that the incident light beam is variable in many ways, for example, the beam path or the polarization can be changed. Further, an antireflection layer may be mounted on or in the dielectric medium. Furthermore, it can be achieved by nanostructuring of the dielectric medium that the dielectric medium experiences an optical anisotropy, so that the incident or emergent light is preferably directed in this direction. The advantage of the locally invariable refractive index is the ease of manufacture.

The dielectric medium may have a location-dependent and / or direction-dependent refractive index. The medium may have a location-independent and / or direction-independent refractive index. For example, the medium may be discontinuous and / or inhomogeneous. For example, the medium may be contiguous and / or be homogeneous. An inhomogeneous medium may, for example, be understood as meaning a medium which has different phases of the same substance or material or different states of matter of the same or different substances or materials.

The dielectric medium may for example comprise at least one of the following substances: water, carbon disulfide, polymethyl methacrylate, benzene, xylene, toluene, BTX, cellulose acetate butyrate or at least one substance of the following groups: organic solvents, alkanes, silicones, silicone oils, polycarbonates, transparent polymers, in particular cellulose butyrates, acrylates, glycol-modified polyethylene terephthalates, glasses, in particular optical glasses.

The advantage of water is its abundance and wide distribution, its transmission in the sensitivity range of conventional photovoltaic converters, its chemical resistance, especially with long-term increased solar radiation and its low procurement costs.

Carbon disulfide is a colorless liquid with a suitable refractive index and good optical stability, which can be used well in combination with glass.

Also, the substances benzene, xylene, toluene, BTX are readily available and have good optical properties, i. E. also high refractive indices. Depending on which other materials are used, the refractive index can be adjusted by the choice of materials.

Particularly preferred is polymethyl methacrylate, which has as an advantage a high dielectric constant, a high optical transmission, and an exact machinability or good dimensional stability.

Also beneficial is the use of organic polymers for the dielectric medium or portions thereof. As already mentioned, polymethylmethacrylate with n = 1, 492 is preferred. It is a lightweight material and good in various forms. Surprisingly, this makes it possible to produce very good mirror cylinders, which can be guided in a PMMA solid. Lightweight materials can be readjusted energy-efficient. These cylinders can be easily replaced in the cavities in case of damage or color formation. In addition, the production is simplified. By storage in the cavities, the mirrors are well managed and do not require a complex mount or guide mechanism.

In addition to the high refractive index, PMMA is also good temperature-resistant and proves to be particularly advantageous in outdoor applications due to high weather resistance.

In addition, the chromatic aberration of PMMA caused by dispersion is smaller than that of water (see Abbe number).

Thus, the dielectric medium is particularly preferably a polymeric thermoplastic, in particular PMMA and / or polycarbonate.

In these hard and stable polymers, the mirror surfaces can be easily installed in the cylinder body, or reshape. It is also possible vapor deposition of a thin mirror surface (for example, aluminum, silver, etc.) on a half-cylinder, which is then complemented by closed adhesion of the second half. This works well with thermoplastics with a relatively low glass transition temperature, which should, however, be above 1 00 ° C in order to avoid thermal deformation in strong sunlight.

Also preferred are polycarbonates because of their high strength. These are particularly weather and radiation stable. With a refractive index of 1.855, these easily moldable thermoplastics have excellent refractive indices and are inherently colorless and transparent in the relevant or interesting wavelength range.

Finally, it is also possible to use other transparent solids such as glass, in particular optical glass, for the structures of the medium. Glasses are preferred because of their high robustness and weather resistance. Glasses can be well combined with the aforementioned liquids, which can be used, for example, as cylinder lubricants.

In one development of the invention, a cover layer, in particular a cover glass, is arranged above the dielectric medium. This has the advantage that the particular optical effects can be divided between the cover layer and the underlying dielectric medium. Furthermore, such a separation simplifies the manufacture of such a D-mirror. Furthermore, advantageously, for example, worn by sand or other environmental influences cover layer easy be replaced. According to one embodiment, the refractive index of the cover layer is identical or similar to the refractive index of the dielectric medium or the boundary layer of the dielectric medium adjoining the cover layer.

The light incident surface of the D-mirror may be uneven, for example. In this case, for example, the light incident surface of the D mirror may be such that a maximum intersection angle between every two tangent planes of the set of tangent planes at each point of the light incident surface is smaller than 60 °. Preferably, this maximum cutting angle is less than 40 °. This maximum cutting angle is preferably less than 20 °. Preferably, this maximum cutting angle is less than 10 °. This maximum cutting angle is preferably less than 5 °. Most preferably, this maximum cutting angle is less than 2 °.

Further, the light incident surface of the D mirror may have a concave or convex shape. The concave or convex shape may be spherical concave or convex. Furthermore, this shape can only be concave or convex along a first spatial direction, while it can be translation-invariant in a second spatial direction perpendicular to the first spatial direction. The shape may also be such that it is concave or convex along two orthogonal spatial directions, the light incident surface having different radii of curvature in the two spatial directions.

The light incident surface of the D-mirror may, for example, be a plane, in particular a horizontal plane.

For example, the light incident surface of the D-mirror may have at least two planar portions. Here, the light incident surface may have at least one intermediate step. In the case where the incident light beam is perpendicular to the D mirror and the outgoing light beam is at an angle to the plane light incident surface and in a certain direction, for example, that plane portion having the highest level on the light incident surface in one Be region which is remote from the direction of the outgoing light beam. In the case of a plurality of steps lying between the planar sections, the planar sections may be arranged such that the planes are arranged higher in each case along one direction.

For example, the light incident surface of the D-mirror may have at least two sections with at least one intermediate step, the sections not being planar are. In this case, the sections may for example each have a concave or convex shape. The concave or convex shape may be spherical concave or convex. Furthermore, this shape can only be concave or convex along a first spatial direction, while it can be translation-invariant in a second spatial direction perpendicular to the first spatial direction. The shape may also be such that it is concave or convex along two orthogonal spatial directions, the light incident surface having different radii of curvature in the two spatial directions. For example, that portion having the highest level on the light incident surface in a region remote from the direction of the outgoing light beam. In the case of a plurality of steps lying between the planar sections, the planar sections may be arranged such that the planes are arranged higher in each case along one direction.

Furthermore, the D mirror can, for example, have at least two mirror elements disposed downstream of the light incident surface for deflecting the light beam into a light beam that emerges. The number of mirror elements may be greater than 3, for example. The number of mirror elements may be greater than 4, for example. For example, the term "downstream" may mean that an incident light beam first passes through the light incident surface and then strikes at least one mirror element The mirror elements may reflect such light rays, and such reflected beam may be from the other, for example Page through the light incident surface, after which he leaves the D-mirror and thus fails.

The mirror elements can each be arranged adjacent to each other. The mirror elements of the D-mirror can be designed identically, for example.

The mirror elements may, for example, each have a reflective surface. The reflective surface of the mirror elements may be flat, for example.

For example, the dielectric medium may completely fill a space between the reflective surfaces of the mirror elements and the light incident surface. This leads to a greater deflection or refraction of the light rays and thus to a greater reduction of shading compared to the case in which this space is only partially filled. Further, this will increase the variation in beam diameter from incoming to outgoing beam. The mirror elements may have an extension greater than 0, 1 mm. The term expansion of a mirror element may, for example, be understood to mean the smallest length along one of the three spatial directions. The mirror elements may have an extension greater than 0.2 mm. The mirror elements can have an extension greater than 0.5 mm. The mirror elements can have an extension greater than 1 mm. The mirror elements can have an extension greater than 10 mm. The mirror elements can be mechanically movable.

Above the dielectric medium of a D-mirror, for example, a cover layer, in particular a cover glass, can be arranged. The dielectric medium of a D-mirror or the cover layer may have an antireflection coating, in particular on the cover layer. This has u.a. the advantage that the incident on the D-mirror light is not reflected directly at the light incident surface and thus more light can penetrate into the dielectric medium of the D-mirror, whereby more light is directed in the desired direction of failure of the D-mirror. The anti-reflection coating can be broadband, for example in a range between 400 and 800 nm.

The antireflection coating may comprise at least one of the following materials: a material with a low refractive index, a nano-structured material, in particular a porous nano-structured material, a sol-gel-deposited material or an angle-dependent deposition (OAD) manufactured material. Here, a low refractive index is understood to mean a refractive index of less than 1.25, which can not be produced with conventional dielectric materials, and in particular the range of 1.05 to 1.25. Materials with such refractive indices can be produced, for example, by new technologies, in particular by nanostructuring. The term nanostructuring is understood to mean a structure having a structuring period which is less than the smallest intended use wavelength, for example, when used for visible radiation less than 400 nm. A nanostructure with a structuring period smaller than 400 nm thus does not result in any specular, ie. Reflecting reflection, even with deviations from the perfect periodicity.

This can be used for optimizing the antireflection layer for the conditions of use of the D mirror, ie when the incident or emergent light beam is nearly parallel to the cover layer with a cornering angle of approximately 85 °. For such angle is the Transmission is very low and vanishes completely for further increasing angles to 90 °, so that in this case there is a 1 00% reflection. Therefore, the antireflection layer is of particular importance in the D mirror. In this case, the input and output angles are measured with respect to the solder perpendicular to the D-mirror, ie vertical incident of the sunlight on the D-mirror corresponds to an angle of incidence of 0 °. With conventional dielectric materials, which typically have a refractive index greater than 1.25, perfect antireflection is not possible. Required would be materials with a refractive index in the range of 1.05 to 1.25. One solution is nano-structured dielectrics, for example dielectric needles with a base diameter of 50 nm and a height or length of 500 nm, which are perpendicular to the surface and arranged with a period of 350 nm in the two dimensions of the surface. Furthermore, other structurings, for example dielectric filaments or nano-porous structures, are possible. For the application, a low, volume-related dielectric fill level of, for example, less than 10%, is important. The optical properties of such structures are expressed by an effective average refractive index. Such a structuring of the cover layer can achieve a hundred percent transmission through the cover layer for each angle of incidence and both polarizations, ie for s and p polarization. A conventional antireflection coating can not afford this

According to one embodiment, the mirror elements may be fixed, i. not be mobile. According to a further embodiment, at least one mirror element of a D-mirror can be rotatable. The at least one mirror element can in particular be rotatable about the longitudinal axis. The mirror elements of a D-mirror can be rotatable, in particular about its longitudinal axis.

The antireflection coating may have a refractive index between 1. 03 and 1.25. The antireflection coating preferably has a refractive index between 1.05 and 1.2. The antireflection coating preferably has a refractive index between 1.05 and 1.55.

The planar reflecting surfaces of the mirror elements may be parallel to each other. This has the advantage that at the same angle of inclination of the mirror elements, the light beams are deflected in each case in the same direction. The mirror elements may, for example, be elongate, in particular rectangular. These shapes have the advantage that the mirror elements can be arranged next to one another.

The longitudinal axes of the mirror elements may be parallel to each other. The longitudinal axes of the mirror elements may be parallel to the light incident surface or the planar portions of the light incident surface.

For example, the mirror elements of a D-mirror may lie in one plane. This can mean that in particular the centers of the mirror elements can lie in one plane. For example, such a plane in which the mirror elements of the D-mirror are located may have a slope relative to the light incident surface. This may mean that such a plane includes a cut angle with the light incident surface. The D-mirror may thus have a flat outer shape.

In such a case it can be provided that the individual mirror elements are displaceably arranged along a direction to the light incident surface. The respective displacement distance may, for example, be less than one wavelength of the radiation used. If a wide range of wavelengths is used, a suitable wavelength can be used here. As a result, for example, the light field reflected or radiated by the mirror elements can be adjusted or changed within wide limits. The interference image of the rays is changed starting from the mirror elements by the mirror shift.

The reflecting surface of a mirror element of a D-mirror can be nanostructured. This has the advantage that a dispersion of the overall optical system can be compensated or compensated. Under the total optical system, the entirety of all components that act on the light beam between the entrance of the light beam in the D mirror to the exit from the D mirror understood. For most transparent substances or media, there is the so-called normal dispersion, in which the refractive index increases with increasing frequency. Thus, the cover layer and also the refraction at the interface between the cover layer and air has a normal dispersion. This normal dispersion can be compensated in particular by means of a nanostructuring of a surface of a mirror element. Furthermore, this compensation can be done with a diffraction grating with blazing or a blaze grating be achieved. A blazed grating is a special reflection grating in optics optimized for diffracting a particular combination of wavelength and diffraction order. Compensation of the dispersion results in the overall system mapping each wavelength in the compensated range to the same point.

For example, the plane of the mirror elements of a D-mirror may be parallel to the light incident surface of the respective D-mirror or the planar portions of the light incident surface of the respective D-mirror.

For example, a D-mirror may be rotatable about the central perpendicular axis perpendicular to the light incident surface or an axis parallel thereto.

For example, a solder standing on the light incident surface of the first D mirror can form an angle of 70 ° to 110 ° with a solder standing on the light incident surface of the second D mirror. Preferably, this angle is between 80 ° and 1 00 °. It is further preferred that this angle is between 85 ° and 95 °. It is further preferred that this angle is between 87 ° and 93 °, in particular exactly 90 °.

For example, the longitudinal axes of the mirror elements of the first D-mirror may form an angle between 20 ° and -20 ° with the solder standing on the light incident surface of the second D mirror, and the longitudinal axes of the mirror elements of the second D mirror may be perpendicular to the longitudinal axes of the second D mirror Be mirror elements of the first D-mirror. The longitudinal axes of the mirror elements of the first D mirror can form, for example, an angle between 1 0 ° and -10 ° with the solder standing on the light incident surface of the second D mirror. The longitudinal axes of the mirror elements of the first D mirror can form an angle between 5 ° and -5 °, for example, with the solder standing on the light incident surface of the second D mirror. The longitudinal axes of the mirror elements of the first D mirror can form an angle between 3 ° and -3 °, for example, with the solder standing on the light incident surface of the second D mirror.

An optical axis of the element for changing the optical anisotropy of the light beam may, for example, form an angle between 70 ° and 110 ° with the longitudinal axes of the mirror elements. This angle can be between 80 ° and 100 °, for example. This angle can be between 85 ° and 95 °, for example. This angle can be for example 90 °. For example, the first D mirror and the optical anisotropy changing element of the light beam may be arranged such that the light beam emitted from the first D mirror is interposed between the first D mirror and the optical anisotropy element of the light beam with the light incident surface forms an angle between 80 ° by 1 00 °. This angle can be between 85 and 95 °, for example. This angle can be for example 90 °.

The element for changing an optical anisotropy of the light beam may, for example, be a lens, in particular an aspherical lens or a cylindrical lens, a mirror, in particular an aspherical mirror or a cylindrical mirror, or a second D mirror.

In the event that the element for changing an optical anisotropy of the light beam is a second D-mirror, z. B. the incident light beam from the first D mirror are directed to the second D-mirror and the light beam after passing through the second D-mirror become a failing light beam.

If the optical anisotropy changing element is a lens or a mirror, the light beam irradiated on the optical anisotropy element changing arrangement and the first D mirror may be such that the beam-covered area of the lens or the mirror in a parallel direction of a line of intersection of a continued lens or mirror plane and the light incident surface has at least twice as large extent as in a direction perpendicular thereto.

For example, an angle of incidence of a light beam incident on a D mirror or an angle of reflection of a light beam emitted by a D mirror may be greater than 70 °. In this case, the respective angle of incidence or failure can be measured between the incoming or outgoing light beam and the solder on the respective light incident surface. In this case, the incoming or outgoing light beam can be projected into a specific plane, in particular a sagittal plane or a meridional plane. For example, an incident angle of a light beam incident on a D mirror or an angle of reflection of a light beam emitted from a D mirror may be greater than 75 °. For example, an angle of incidence of a light beam incident on a D mirror or an angle of reflection of a light beam emitted by a D mirror may be greater than 80 °. An angle of incidence of a light beam incident on a D mirror or an angle of reflection of a light beam emitted by a D mirror may be, for example, greater than 85 °. For example, an angle of incidence of a light beam incident on a D mirror or an angle of reflection of a light beam emitted by a D mirror may be greater than 87 °.

A D-mirror, which has a flat light incident surface and has identical, level and juxtaposed mirror elements with the same angular position, which lie in a plane parallel to the light incident surface, has no geometrical aberration. This means that parallel incident rays are imaged exactly in parallel outgoing rays.

A D-mirror as described herein can also function without a further optical element as a beam expander or as a device for changing a beam profile of an incident light beam.

A D-mirror, as described herein, offers a variety of applications. A D-mirror can be used for example in solar technology, in particular photovoltaic or solar thermal, as a flat heliostat, which can be placed flat on the ground. Due to the reduced mutual shading of the mirror elements, which is due to the presence of the dielectric medium, this results in an increased light output compared to conventional heliostats.

Furthermore, the D-mirror can be used to guide natural sunlight from outside to a location in a building that has no direct access to the outside. The market is very interested in such use because natural light in a building is perceived as more pleasant than artificial light. A D-mirror is very well suited for such an application because it has a compact design and perpendicularly deflects simple light at an angle of almost 90 °. A D-mirror has higher efficiency for this application than prior art devices. Furthermore, the dispersive properties of the D-mirror can be used to set the interior lighting to a certain color or intended atmosphere.

For example, a D mirror can also be used as a light source for parallel light. This is used, for example, in the lighting of buildings or public places. For example, a D mirror can generate parallel light. Since different light wavelengths or light colors are imaged on different locations due to the chromatic dispersion, different colors can also be superimposed on the illuminated object.

Alternatively, the chromatic dispersion can be corrected by micro or nanostructuring of the mirror. Furthermore, in this case, an optical delay line can also be used to correct the dispersion. This can be achieved by means of a constellation with 2 D mirrors whose light incident surfaces enclose an angle smaller than 20 °.

Further, a D-mirror can be used as a laser beam scanning or laser scanning device or for long-range light focusing. For a Gaussian beam, the size of the focus or the beam waist is determined by the ratio of the aperture to the focal length. If the object is far away, therefore, a large aperture is needed. This can be achieved by a continuous beam and a lens arranged further ahead of the beam. Furthermore, this can be achieved by an arrangement as shown in FIG. 3. In this case, if a lens is placed in the incident light beam, the emergent light beam may have a focus. The quality of this focus can be determined by the diameter of the second D-mirror. In the present case, the second D-mirror has a comparatively large diameter. The quality of the focus can be optimized according to the theory of Gaussian rays.

The present invention will now be further explained with reference to individual examples and figures. These examples and figures are merely illustrative of the general inventive concept, without the examples and figures being construed as limiting the invention in any way.

FIG. 2 illustrates the entrance and exit angles of a D-mirror. FIG. 3 shows an arrangement of two D mirrors.

Figure 4 shows an arrangement of a D-mirror with a conventional mirror.

Figure 5 shows an arrangement of a D-shaped mirror having a stepped light incident surface and a condenser lens. FIG. 2 illustrates a light beam incident on a D mirror 1 00 and a light beam emerging from a D mirror. FIG. 2 shows a D mirror 1 00 with a light incident surface 1101. A first dielectric medium 1 1 5, in which the incident light beam 1 1 7 extends, has a value of the refractive index of n _η and is shown in Figure 2 above the light incident surface 01. Below the light incident surface 01 01, a second dielectric medium 1 1 9 is shown, in which the refracted light beam 1 21 extends and whose refractive index has the value n ₂ . The incident light beam 1 1 7 has an angle of incidence Οί ^, which is measured against a on the light incident surface 1 01 perpendicular incident slot 1 23. In this case, angles which are measured to the left by the upwardly facing incident slot 1 23 have positive values and angles, which are measured to the right by the incident slot 1 23, negative values. In Figure 2, therefore, the angle of incidence has a positive value and the angle and β ₂ negative values.

At the light incident surface 1 01 of the incident light beam 1 1 7 is broken according to the Snell's law of refraction. This is as follows: sin = n ₂ sin a ₂ . Thus, a positive angle a _{2 of} the refracted light beam 1 21 results from a positive angle of incidence 0. In typical D-mirror applications, Οί ^ is very small or nearly 0 °, which means that a _{2 is also} close to 0 °.

In the embodiment of FIG. 2, the refracted beam 1 21 strikes a planar mirror element 1 25 after refraction. A plurality of mirror elements 1 25 are arranged on a straight line parallel to the light incidence surface 11 01 and distributed uniformly along a horizontal line. Furthermore, the mirror elements 1 to 25 Einfallslot 1 23 to the same angle. A standing on a flat mirror surface of the mirror element 1 25, to which the refracted light beam 1 21, standing Lot 1 27 has over the entrance slot 1 23 an angle 9 _m , which in the present case is negative, since he from Einfallslot 1 23 seen from the right is measured.

The refracted light beam 1 21 is reflected on the plane mirror surface of the mirror element 1 25 according to the law of reflection and then passes from the side of the second dielectric medium 1 1 9 coming on the light incident surface 1 01 to. The reflected on the mirror surface of the mirror element 1 25, refracted light beam 1 21 is referred to as a reflected refracted light beam 1 29. The reflected refracted light beam 1 29 has the entrance slot 1 23 an angle of ß ₂ . From Figure 2 it can be seen that The following angular relationship between the angle of incidence a _{] (} the angle 9 _m and the angle ß ₂ applies: ß ₂ = 2 9 _m - a,. The reflected refracted light beam 1 29 at the light incident surface 1 01 at the passage of the second dielectric medium 1 1 . 1 1 9 again refracted into the first dielectric medium according to the Snell's law, and then falls from the D-mirror 1 00 as an emergent beam 1 31. in this case, reads it as follows:. sin = n ₂ sin ß ₂ ß ₂ can in this case be interpreted as the angle of the outgoing light beam 1 31 of the D mirror 1 00.

It is understood that for certain angles of Οί ^ and 9 _m, the light beam does not re-enter the first dielectric medium 1 1 5, but may not even reflected in the direction of the light incident surface 01 01 or is totally reflected at the light incident surface 01.

By inserting the angular relationship in the latter Snell's law of refraction, solving the equation obtained for sin βϊ and differentiating on the angle of incidence, one obtains the angular dependence of the outgoing light beam 1 31 as a function of the angle of incidence of the incident light beam 1 1 7. This angle dependence can be expressed as follows: dss _y _ cos /? ₂ · cos _t

(1 )

άα _γ cos?! · Cosa ₂

For many D-mirror applications, the angles ΐ and a _{2 are} nearly 0 ° and the

Failure angle βτ almost 90 °. Equation (1) can thus be approximated to: dß _y cos /? ₂

(2)

άα _γ cos?!

FIGS. 3A and 3B show an embodiment of a beam expander according to the invention. The beam weiterweiter 1 32 of Figure 3 has a first D-mirror 1 33 and a second D-mirror 1 35 on. The view of Figure 3A shows the Strahlaufweiter 1 32 from the side and the view of Figure 3B shows the Strahlaufweiter 1 32 from above. To illustrate the spatial relationships, a Cartesian coordinate system with the axes x, y and z is shown next to each figure. Both the first D mirror 1 33 and the second D mirror 1 35 may each be a D mirror 1 00, as described above. Figure 3 is a schematic drawing whose dimensions and angles do not match a true embodiment of a beam expander. An incident light beam 1 37, which runs in air, first strikes the first D mirror 1 33 and that on the light incident surface 1 39 of the first D-mirror 1 33. The incident light beam 1 37 may be shaped so that the light incident surface 39 of the first D-mirror 1 33 as well as possible covered or illuminated. In FIG. 3A, three different sub-beams 1 38 of the incident light beam 1 37 are shown, which run parallel to one another and have a different height along the z-axis.

In the view of Figure 3B, the same three incident partial beams 1 38 are shown, which fall on the first D-mirror 1 33. The incident partial beams 1 38 of FIG. 3B are offset along the y-axis. The incident partial beams 1 38 hit, after they have passed through the light incident surface 1 39 of the first D mirror 1 33, on mirror elements 1 41st

The angle of incidence of the incident partial beams 1 38 on the light incident surface 1 39 of the first D mirror 1 33 may be 85 °, for example, and the angle of incidence in FIGS. 3A or 3B can not be read correctly since the views of FIGS. 3A or 3B are projections are. The incident light beam 1 37 is reflected by the first D mirror 1 33. This light beam 1 43 reflected by the first D mirror 333 then strikes a light incident surface 455 of the second D mirror 1 35. The parameters of the first D mirror 1 33 and of the incident light beam 1 37 and the dimensions of the second D mirror 1 35 can be selected so that the light beam 1 43 reflected from the first D mirror 1 33 as well as possible covers or illuminates the light incident surface 1 45 of the second D-mirror 1 35.

It is shown in the view of FIG. 3A that the three different reflected partial beams 1 44 strike the light incident surface 45 of the second D mirror 1 35 at different points along the x-axis. The three different reflected partial beams 1 44 are parallel to each other. After the partial beams 1 44 have passed through the light incident surface 1 45 of the second D-mirror 1 35, they meet mirror elements 1 47 of the second D-mirror 1 35, are from the mirror elements 1 47 of the second D-mirror 1 35 in the direction of Reflected light incident surface 1 45 of the second D-mirror 1 35, then pass through the light incident surface 1 45 second D-mirror 1 35 and thus leave the second D-mirror 1 35. The reflected light from the second D-mirror 1 35 light beam 1 49 leaves the Strah weiterweiter 1 32 as outgoing light beam. The Partial beams 1 50 of the second D-mirror 1 35 reflected light beam 1 49 are parallel to each other and perpendicular to the light incident surface 1 45 of the second D-mirror 1 35.

In the view of FIG. 3B, it can be seen that the three parallel partial beams 1 38 of the incident light beam 1 37 strike the light incident surface 1 39 of the first D mirror 1 33 at different points along the y axis. Since the sub-beam 1 38, which is shown at the top in FIG. 3B, also has the largest z-coordinate, as can be seen in FIG. 3A, it strikes the light incidence surface of the three sub-beams 1 38 as partial beam 1 44 at one location 1 45 of the second D-mirror 1 35, which has the largest x-coordinate. After this partial beam 1 44 has been reflected by the second D-mirror 1 35, it leaves the second D-mirror 1 35 along the z-axis. This is shown symbolically in FIG. 3B with a point with a circle around it. This symbol means that the beam goes out of the drawing plane towards the viewer.

The angle of incidence of the light beam 1 43 reflected from the first D mirror 1 33 on the light incident surface 1 45 of the second D mirror 1 35 may also be 85 °, for example. The emanating from the beam expander 1 32 light beam has compared to the incident light beam 1 37 a significantly larger diameter. For an incident angle of 85 °, typical values for increasing the beam diameter are in the order of magnitude of 1. The beam expander 1 32 has a very compact construction compared to beam expander, which use exclusively calculating lenses.

The second D-mirror 1 45 may, for example along the x-axis have a length of 1 m, along which 1 00 mirror elements 1 47 are arranged side by side.

For a compact construction, it is advantageous if, in the view of FIG. 3A, a lower part of the light incidence surface 1 39 of the first D mirror 1 33 has a small distance to a left part of the light entrance surface 1 45 of the second D mirror 1 35. The mirror elements 1 41 of the first D-mirror 1 33 are perpendicular to the mirror elements 1 47 of the second D-mirror 1 35. This causes in connection with the vertical arrangement of the D-mirror, that a round incident light beam 1 37 also as a round beam of light leaves the beam expander.

Figure 4 shows an arrangement of a D-mirror with a conventional mirror. This arrangement can function as a beam expander, in particular as a large aperture imaging system used, for example, as a telescope in astronomy can. Furthermore, the arrangement of FIG. 4 can be used, for example, for an imaging detection of weak signals, in particular as a night vision device or for spectroscopic applications.

The view of Figure 4A shows the beam farther from the side and the view of Figure 4 B shows the beam running farther from above. To illustrate the spatial relationships, a Cartesian coordinate system with the axes x, y and z is shown next to each figure.

In the view of FIG. 4A, it can be seen that an incident light beam 1 37 initially strikes a light incident surface 1 39 of a first D mirror 1 33. This situation is similar to the embodiment of FIG. 3, but in the embodiment of FIG. 4 the incident light beam 1 37 strikes the incident light surface 1 39 of the first D-mirror 1 33 perpendicularly or nearly perpendicularly, whereas in the beam expander 1 32 of FIG 3 of the first D mirror 1 33 reflected light beam 1 43 almost perpendicular to the light incident surface 1 39 of the first D mirror 1 33 runs. It should also be noted here that in the embodiment of FIG. 3 the light beam 1 49 reflected by the second D mirror 1 35 extends perpendicular to the light incident surface 45 of the second D mirror 1 35. In the case of the first D mirror 1 33 in FIG. 4, there is thus a type of beam reversal in comparison with the embodiment of FIG. Accordingly, the first D mirror 1 33 of FIG. 4 acts as a beam reducer, while the D mirrors 1 33, 1 35 of FIG. 3 each function as a beam expander.

In the embodiment of Figure 4, the first D mirror 1 33, a mirror 1 51 is connected downstream. The mirror 1 51 of the embodiment of Figure 4 is a spherical mirror, which reflects the reflected from the first D mirror 1 33 light beam 1 43. The mirror 1 51 is arranged in the view of Figure 4A with a small distance above the first D-mirror 1 33 and at its left end. At this position, the reflecting surface of the mirror 51 is substantially along the z-axis.

The parallel before this reflection light rays of the first D mirror 1 33 reflected light beam 1 43 are focused by the mirror 1 51 on a focal point F. In the embodiment of FIG. 4, the light beam 1 53 reflected by the mirror 1 51 runs symmetrically with respect to the x-axis, which extends parallel to the light incident surface 1 39 and perpendicular to the mirror elements 1 41 of the first D mirror 1 33. The focal point F is located just outside the x-axis The position of the focal point F is along the z-axis viewed above the light incident surface 1 39 at a distance which is about twice as large as the extension of the mirror 1 51 along the z-axis.

Figure 5 shows an arrangement of a first D-mirror 1 33 and a lens 1 55. An incident light beam 1 37 strikes a light incident surface 1 39, which is step-shaped. The light incident surface 1 39 has planar sections 1 57 with intermediate stages. To simplify the illustration, the light incident surface 1 39 only three stages 1 57 on. Here, the planar portions 1 57 increase continuously from one side of the first D mirror 1 33 to the other. The planar sections 1 57 are each offset from an adjacent step by an amount S. In this case, the planar portions 1 57 is shifted farthest in the direction of the incident light beam 1 37, ie along the z-axis, which is on the light incident surface 1 39 farthest from the lens 1 55 away. The adjacent planar section 1 57 is offset by the amount S in the direction of the incident light beam 1 37, ie in the negative z-direction. The planar sections 1 57 each have an identical length along the x-axis. Under each flat portion 1 57, a corresponding mirror element 1 41 is arranged centrally with respect to the x-axis, which are arranged offset in the same manner as the flat portions 1 57 along the z-direction. The mirror elements 1 41 are identical and have the same angle of inclination relative to the flat sections 1 57. Parallel to the first D-mirror 1 33 incident partial beams 1 38 of the incident light beam 1 37 are reflected by the first D mirror 1 33 in parallel partial beams 1 44 of the first D mirror 1 33 reflected light beam 1 43. However, adjacent sub-beams 1 44 are farther apart than in the case of a D-mirror without stepped light incident surface 1 39. The reflected from the first D mirror 1 33 light beam 1 43 then strikes a lens 1 55, which the parallel sub-beam 1 44 on a Focal point F focused. Since the view of Figure 5 is translationally invariant with respect to the y axis perpendicular to the x and z axes, the lens 1 55 is a cylindrical lens and the focal point F is a line focus.

For example, the device shown in Figure 5 can be used to create a laser focus in a scanner or for an imaging system from distant, but not necessarily infinitely distant, pixels. The step-shaped light incident surface 1 39 of the first D mirror 1 33 causes an incident light beam 1 37, which is slightly divergent, can be imaged onto a point. Here, the object point of the first D-mirror 1 33 be far away, the object. However, should not be infinitely far away from the first D mirror 1 33.

Reference number list

1 00 D mirror

1 01 light incident surface

1 03 first light beam

1 05 first mirror element

1 07 second mirror element

1 09 second light beam

1 1 1 Impact point of the boundary beam

1 1 3 projection point

1 1 5 first dielectric medium

1 1 7 incident light beam

1 1 9 second dielectric medium

1 21 broken light beam

1 23 incidence slot

1 25 mirror element

1 27 lot

1 29 Reflected, refracted light beam

1 31 outgoing light beam

1 32 beam expander

1 33 first D mirror

1 35 second D mirror

1 37 incident light beam

1 38 partial beam of the incident light beam

1 39 Light incident surface of the first D-mirror 1 41 Mirror element of the first D-mirror

1 43 light beam reflected from the first D mirror

1 44 partial beams

1 45 light incident surface of the second D-mirror

1 47 mirror elements of the second D-mirror

1 49 light beam reflected by the second D mirror

1 50 partial beams

1 51 mirrors

1 53 light beam reflected by the mirror lens

level sections

Claims

claims

1 . Device for modifying a beam profile of an incident light beam, in particular beam expander, comprising: a first D mirror; and an optical anisotropy element of the light beam, wherein the first D mirror and the optical anisotropy changing element of the light beam are arranged such that either the incident light beam first strikes the first D mirror and then from the first D Mirror is directed to the element for changing an optical anisotropy of the light beam or the incident light beam first strikes the element for changing an optical anisotropy of the light beam and is then directed by the element for changing an optical anisotropy of the light beam to the first D mirror ,

2. Device according to claim 1, characterized in that the element for

Changing an optical anisotropy of the light beam is a lens, in particular an aspherical lens or a cylindrical lens, a mirror, in particular an aspherical mirror or a cylindrical mirror, or a second D-mirror.

3. Apparatus according to claim 1 or 2, characterized in that the first and / or the second D-mirror each comprising: a dielectric medium having a light incident surface and a refractive index greater than 1, 3, and at least two of the light incident surface downstream mirror elements for deflection of the light beam into a light beam emerging from the first or second D mirror, wherein the mirror elements are each disposed adjacent to each other, wherein the mirror elements each have a flat reflective surface, wherein the dielectric medium completely fills a space between the reflective surfaces of the mirror elements and the light incident surface, and wherein the mirror elements have an extension greater than 0, 1 mm ,

4. Apparatus according to claim 3, characterized in that above the dielectric medium, a cover layer, in particular a cover glass, is arranged.

5. Apparatus according to claim 3 or 4, characterized in that the dielectric medium or the cover layer has an antireflection coating, in particular on the cover layer.

6. Apparatus according to claim 5, characterized in that a refractive index of the antireflection coating has a refractive index between 1, 03 and 1, 25.

7. Device according to one of claims 3 to 6, characterized in that the

Light incident surface of the first and / or second D-mirror is a plane.

8. Device according to one of claims 3 to 7, characterized in that the

Light incident surface of the first and / or second D-mirror has at least two planar sections with at least one intermediate stage.

9. Device according to one of claims 3 to 8, characterized in that the planar reflecting surfaces of the mirror elements are parallel to each other.

1 0. Device according to one of claims 3 to 9, characterized in that in the first and / or second D-mirror, the mirror elements are elongated, and

Longitudinal axes of the mirror elements are parallel to each other. 1 1. Apparatus according to claim 1 0, characterized in that the longitudinal axes of Mirror elements parallel to the light incident surface or the flat portions of the light incident surface. 2. Device according to one of claims 3 to 1 1, characterized in that the mirror elements of the first and / or second D-mirror lie in a plane. 3. Apparatus according to claim 1 2, characterized in that the plane of

Mirror elements of the first and / or second D-mirror is parallel to the light incident surface of the first and / or second D-mirror or the planar portions of the light incident surface of the first and / or second D-mirror. 4. Device according to one of claims 7 to 1 3, characterized in that a standing on the light incident surface of the first D mirror solder forms an angle of 70 ° to 1 1 0 ° with a standing on the light incident surface of the second D mirror solder , 5. Apparatus according to claim 1 4, characterized in that the longitudinal axes of

Mirror elements of the first D-mirror with the standing on the light incident surface of the second D mirror perpendicular angle between -20 ° and 20 ° and the longitudinal axes of the mirror elements of the second D mirror are perpendicular to the longitudinal axes of the mirror elements of the first D mirror , 6. Device according to one of claims 1 0 to 1 5, characterized in that an optical axis of the element for changing the optical anisotropy of the light beam with the longitudinal axes of the mirror elements of the first D-mirror forms an angle between 70 ° and 1 1 0 ° , 7. Device according to one of claims 3 to 1 6, characterized in that the first D-mirror and the element for changing the optical anisotropy of the light beam are arranged so that the light beam emitted by the first D mirror between the first D-mirror and the element for changing the optical anisotropy of the light beam with the light incident surface forms an angle between 80 ° and 1 00 °. 8. Device according to one of the preceding claims, characterized in that an angle of incidence of an incident on the first or second D-mirror Light beam or an angle of reflection of a light beam from the first or second D mirror is greater than 70 °.

1 9. Device according to one of claims 3 to 1 8, characterized in that at least one mirror element of the first and / or second D-mirror is rotatable, in particular about the longitudinal axis of the at least one mirror element.

20. Device according to one of the preceding claims, characterized in that the device is used to change an optical anisotropy and / or a beam diameter of the incident light beam.