Waveguide-based imaging system

Abstract

An imaging system comprises a waveguide and at least two diffraction-based coupling-in elements, the at least two coupling-in elements being configured to deflect at least some of the light incident on the coupling-in elements within the waveguide, the at least two coupling-in elements being tilted relative to one another at a tilt angle that is not equal to 0°.

Description

[0001] WAVEGUIDE-BASED IMAGING SYSTEM

[0002] 1. Technical area

[0003] The present invention relates to waveguide-based imaging systems, e.g., for RGB holocams. Examples of the invention are imaging systems based on diffraction-based coupling elements for coupling light incident on the coupling elements into a waveguide.

[0004] 2. State of the art

[0005] Diffraction-based optical elements, such as gratings or holograms, are preferably used to redirect light incident on waveguides within the waveguide. This allows, for example, customized imaging systems to be created.

[0006] Although the waveguide can be designed in a variety of ways, for some applications it can be in the form of one or more panes, or integrated into them. The example of multiple panes can include laminated glass, which can comprise at least two glass panes, which can each be connected to one another, for example by an intermediate layer, e.g. made of plastic, cast resin and / or a composite film. For example, light incident on the waveguide (e.g. a pane) at a first position can be guided internally via the waveguide to a different, second position on the waveguide (e.g. the pane), from where it can then be directed, for example, onto a camera and / or an image sensor. In this way, the camera, for example, can be arranged in a position that is different from the first position and where it is not visible from the outside, for example.

[0007] Diffraction-based optical elements can exhibit an angle dependence in the spectral distribution of the redirected light. If diffraction-based elements are used to collect light in imaging systems, a true-color image of the imaging system can therefore sometimes only be achieved in a small area of ​​the theoretically available field of view (FOV) of the diffraction-based elements. At light incidence angles that lie outside this FOV range, angle-dependent blue or red shifts can occur: Diffraction-based optical elements typically have an FOV that encompasses the solid angle range from which incident light can be collected and / or redirected by the optical element. This can work well at essentially one wavelength. For example,Monochromatic holograms are designed to redirect light of a specific wavelength at a specific angle when it comes from a predetermined direction, e.g., along a central direction of the FOV. If the direction of incidence of the light deviates from the predetermined direction, in the example of a hologram, a different color can be redirected along the predetermined direction instead of the actual color to which the hologram is aligned. If such a diffraction-based element is used in imaging systems, unwanted spectral angle dependencies can arise: Depending on the angle, only part of the complete spectrum can be imaged, meaning that spectral ranges are missing. As a result, different colors than desired can be imaged in images. With RGB optical elements, this effect can create a white light image in part of the FOV.The complete spectrum may be present, but there may be stronger red or blue shifts at the edges of the FOV.

[0008] The present invention is therefore based on the object of at least partially improving corresponding imaging systems, systems and associated methods.

[0009] 3. Summary of the invention

[0010] This task is at least partially solved by the aspects described herein.

[0011] A first aspect relates to an imaging system comprising a waveguide and at least two diffraction-based coupling elements (EE). The at least two EEs are configured to at least partially redirect light incident on the EE within the waveguide, wherein the at least two EEs are tilted relative to one another at a tilt angle of not equal to 0°. The imaging system with multiple EEs, each with an FOV, has an enlarged FOV compared to imaging systems with only one EE and also decouples the spectral angular dependence of the redirected light of the mutually tilted EEs at least partially, as described herein. This allows the color quality and fidelity of the images that can be recorded by the imaging system to be improved. The usable range of the FOV of the imaging system can thus be expanded.

[0012] The general principle will be explained using the following figures 1a-d and 2a-b.

[0013] Figures la - id concern an imaging system io with only one EE 20 and serve to illustrate the underlying problem.

[0014] Fig. 1a schematically shows a view of the imaging system 10 with the EE 20 and an output coupling element, AE, 40 in the xz plane. The imaging system 10 further comprises a waveguide 30 with a cross-section in the xz plane in the form of a rectangle elongated in the z direction and a detection system 50, which may include, for example, a sensor and a lens. The EE 20 is located at the upper end of the waveguide 30 on the left side of the waveguide 30, and the AE 40 is located at the lower end of the waveguide 30 on the right side of the waveguide 30.

[0015] The EE 20 has a vertical field of view, v-FOV. The light incident from the v-FOV is deflected by the EE 20 into the waveguide 30, as schematically illustrated by the black arrows. Within the waveguide, the deflected light reaches the AE 40 via total internal reflection. In other embodiments, the light can, for example, also reach the AE 40 with more, fewer, or even no reflections within the waveguide 30. The EE 20, the waveguide 30, and the AE 40 are coordinated in their respective shape, extent, relative position, and / or relative orientation such that the deflected light from the EE 20 reaches the AE 40 as efficiently as possible, from where the deflected light is at least partially coupled out to the detection system 50, as schematically illustrated by the black arrows. The v-FOV has an aperture angle ct v , where ct v= o in the example of Fig. 1a describes a light incidence perpendicular to the surface of the waveguide 30.

[0016] In principle, the deflection of the light by the EE 20 and the AE 40 can depend on the angle of incidence of the incoming light, e.g. in that the deflection angle and / or the spectral distribution of the deflected light depends on the angle of incidence and / or only a part of the light reaches the AE 40.

[0017] Fig. 1b schematically shows a cross-sectional view of the imaging system 10 from Fig. 1a in the xy plane, so that in particular the horizontal field of view, h-FOV, of the EE 10 can be displayed. Fig. 2b shows the horizontal coupling to the EE 20 and the horizontal coupling from the AE 40 to the detection system 50, while Fig. 1a best illustrates the vertical components.

[0018] Fig. 1c schematically shows a cross-sectional view of the imaging system 10 from Figs. 1a and 1b in the yz-plane. It can be seen that the EE 20 is elongated in one direction, in this example along the y-axis, and has a shorter length in the direction perpendicular thereto, in this example along the z-axis, in the plane of the waveguide 30. The EE cross-section in the form of an elongated rectangle defines the region in which light incident on the EE 20 is at least partially redirected within the waveguide 30. Since the area of ​​the AE 40 in the plane of the waveguide 30 is smaller than that of the EE 20, all paths along which the light is redirected from the EE 20 to the AE 40 run, in the projection in the yz-plane, within the light gray trapezoidal region between the EE 20 and the AE 40.Light that extends at least partially outside this trapezoid does not come from the EE 20 and / or does not strike the AE 40 and therefore does not play a decisive role in the imaging of the imaging system 10.

[0019] Imaging systems as described in Figs. 1a to 1c are sometimes modified in the prior art to use multiple parallel holograms as EEs and / or to use RGB holograms as EEs instead of simple monochromatic holograms. However, even in such imaging systems, the problem of spectral angle dependence still exists, as described below as an example:

[0020] Fig. id schematically shows the spectral distribution of the deflected light of three parallel holograms H3 (red), H2 (green), and Hi (blue) across the entire FOV of the three holograms Hi, H2, and H3. The underlying arrangement of the holograms Hi, H2, and H3 can, for example, comprise parallel holograms Hi, H2, and H3 that are shifted parallel to each other along an axis, e.g., perpendicular to the extension of the holograms Hi, H2, and H3.

[0021] Holograms H1, H2, and H3 are monochromatic holograms. Hologram H1 was exposed to blue light and is designed to emit blue light at an angle of ct v = o strikes the hologram Hl at a given deflection angle. As can be seen from Fig. 1a, ct v = o in this example a light incidence perpendicular to the surface of the waveguide and the EE. If the angle of incidence deviates from ct v = o, green or red light (for ct v> o) or ultraviolet light (ct v < o) along the direction of the specified deflection angle. This is a direct consequence of the fact that the EEs are diffraction-based elements, where such angle-dependent spectral shifts can occur.

[0022] The same applies to the holograms H2 for green light and H3 for red light. The light deflected along a specific direction undergoes a v > o a redshift and for ct v < o a blueshift. The angle ct v represents the vertical angle of the FOV of the holograms and is plotted along a vertical axis in Fig. id.

[0023] The three individual holograms Hi, H2, and H3 can also be written into a common RGB hologram S, which exhibits the same spectral angle dependence. Furthermore, S schematically represents the interaction of the holograms Hi, H2, and H3:

[0024] The spectral superposition S of the deflected light of all three holograms Hi, H2, H3 (or a corresponding RGB hologram) follows directly from the spectral angle dependence described here: For the history field in the range ct v > o the blue spectral range is missing and for ct v < o the red spectral range. The FOV can be described in Cartesian coordinates in addition to angular coordinates, e.g., to determine a position within the FOV by a position / distance. Conventionally, the direction of the vertical Cartesian axis in Fig. id would be opposite to the direction of the angle ct. v in Fig. id.

[0025] Fig. id thus represents the problem underlying the invention: If holograms Hi, H2, H3 are used for imaging purposes, a true-color image is obtained over the full spectral range with deviations of ct v = o as difficult.

[0026] With respect to the imaging system 10 of Fig. 1a - 1c, this may mean that the EE 20 may be configured to detect light of a particular color which strikes the EE at a particular angle of incidence (e.g. a v = o), to divert to the AE 40.

[0027] If the angle of incidence deviates from ct v = o, the EE 20 may no longer be able to redirect the light of this wavelength to the AE 40. Instead, light of a different wavelength may meet the spectral conditions to be redirected from the EE 20 to the AE. This relationship results in the angle-dependent red or blue shift of the image generated by the imaging system described here. As a result, areas of the imaging system's FOV may not be imaged in the desired color but rather red- or blue-shifted.

[0028] The inventors have recognized this problem and at least partially remedied it with the aspects described herein, as described by way of example in Figs. 2a and 2b:

[0029] Fig. 2a shows an exemplary imaging system 10 with three mutually tilted EE 21, 22, 23, which can at least partially solve the above-mentioned problem. The relative tilt results in the following situation: If light falls at an angle ct v * o to one of the EEs 21, 22, 23, the spectral shift of the deflected light from the other two EEs can be smaller or, at some angles, even opposite, so that the spectral shifts of the different EEs can be reduced or even cancel each other out. Overall, the size of the FOV and the portion of the FOV in which images with reduced spectral shifts are possible can be increased.

[0030] The three EEs 21, 22, and 23 each have a rectangular FOV due to their rectangular cross-section, similar to that shown in Fig. 1c. They are each tilted by 60° relative to each other. The superposition of the three FOVs can thus be described as a hexagonal FOV (see Fig. 2b).

[0031] Fig. 2b schematically shows the spectral distribution of the deflected light from three holograms Hi, H2, H3, each tilted by 60° to each other, across the entire FOV of the three holograms. The three differently colored stripes in the left view of the FOV represent the spectral distribution within the FOV of the individual RGB holograms described in relation to Fig. 1d. Each of the holograms has a rectangular FOV. The superposition of the three FOVs tilted by 60° relative to each other results in the hexagonal FOV in Fig. 2b. The different areas of the hexagonal FOV correspond to different directions from which light falls on the holograms Hi, H2, H3. Due to the different directions of the incident light, different red and / or blue shifts occur due to the deflection by the holograms Hi, H2, H3. In contrast to the diagram in Fig.id does not result in a color shift in all three holograms Hi, H2, H3, but the following color reproduction results over the hexagonal FOV:.

[0032] Due to the tilt, the spectral superposition S of the deflected light from all three holograms H1, H2, and H3 not only has a central stripe (as in Fig. id) containing all three colors, and thus white light, but also three stripes tilted by 60° to each other, covering a large area of ​​the FOV, over which all three colors (red, green, blue) are deflected according to the exposure of the holograms along the direction of the specified deflection angle. Only in the corners of the hexagonal FOV are there zones where color aberrations are present:

[0033] The dashed diamond-shaped areas in the corners on the left and right sides of the hexagon represent areas where red and blue, but not green, light is deflected. However, these areas can then be recalibrated using white balance. White balance can, for example, involve a post-capture (e.g., digital) image processing process that determines which measured values ​​correspond to neutral white and / or gray, thereby avoiding unwanted color casts, for example.

[0034] The areas of the FOV directly above represent the areas from which incident light is imaged redshifted, and the areas directly below represent the areas from which incident light is imaged blueshifted.

[0035] If light enters at an angle corresponding to the bottom corner of the hexagonal FOV, the image here undergoes a redshift. If light enters at an angle corresponding to the top corner of the hexagonal FOV, the image here undergoes a blueshift.

[0036] In general, by tilting the holograms Hi, H2, H3, the area in which all colors are suitably deflected can be greatly increased compared to the parallel arrangement in Fig. 1a - 1d.

[0037] In some examples, the tilt of the holograms may be associated with the fact that the ray paths (e.g., the central rays) between two EEs and the respective corresponding AE are not parallel. The tilt can therefore also refer to a tilt, for example, of a central ray from a first EE to an AE relative to a central ray from a second EE to the AE (or to another AE). In some examples, the central rays may be tilted, but still essentially lie in the same plane.

[0038] Diffraction-based EEs can generally be designed to at least partially redirect light that strikes the EE, e.g. emitted by an object to be imaged, into the waveguide, where it can be transmitted, e.g. via (total) reflection. The redirection can comprise a pure change in the direction of the light and / or, e.g., focusing, collimating and / or scattering of the incident light. This influencing of the light can be achieved as a whole by one element of an EE, or an EE can comprise several components, each of which determines one of the influences. The EE can comprise, e.g., a transmissive or reflective diffractive structure, a transmissive or reflective volume hologram, a mirror surface, a prism and / or a transmissive or reflective relief grating.

[0039] The EEs can, for example, be mounted on an outer surface of the waveguide, be integrated into the waveguide, etc. The EEs can be mounted on different sides or on the same side of the waveguide. Furthermore, a protective layer for the EEs can be applied to the side of the EE facing away from the waveguide. Such a protective layer can, for example, cover essentially the entire surface of the waveguide, only parts of it, or only the EEs themselves. The EEs can have an at least partially overlapping FOV, which allows them to be considered components of a (single) imaging system.

[0040] The waveguide can comprise any medium that is fundamentally suitable for transmitting light of at least one wavelength. It can, for example, serve other functions, such as a screen, window, vehicle windshield, etc. The waveguide can thus provide a substantially transparent base body to which the EE can be attached. The waveguide can be made of glass or plastic, for example.

[0041] There are various, equivalent in various exemplary embodiments, ways to define a tilt angle of two EE relative to each other:

[0042] The tilt of the EE relative to each other, as described herein, can refer to the EE being tilted in a plane of the waveguide surface. This can, for example, include a tilt about a rotation axis, where the rotation axis is perpendicular to the waveguide surface at the position of the respective EE and / or perpendicular to the surface of the corresponding EE. This definition of the tilt angle can, for example, be sufficient for planar waveguides.

[0043] In some examples, it is also conceivable that the tilt can be defined via the functionality of the EE, e.g. in the case of curved, irregular and / or thickness-variable waveguides: If the EE, as described here, has a hologram that is written, for example, by two exposures from two different directions, the first exposure defines a first direction: If light from this first direction hits the EE, it is deflected by the EE along the direction of the second exposure. These two directions span a spatial plane, which allows a characteristic axis to be defined for the EE that is perpendicular to the plane in which the first and second exposures of the EE hologram lie.The tilt of two EE can then be measured in the relative tilt of the two axes to each other: For two characteristic axes dj and a2 the tilt angle θ is defined by cos(θ) = a^ / Clfiil l^ l)- Thus the tilt angle between two EE can also be defined for arbitrarily shaped waveguides, e.g. also for arbitrarily shaped, curved and / or bent EE.

[0044] Another possible aspect of the tilt angle can be linked to the common field of view of the EE of the imaging system. For example, an effective viewing direction of the EE can be defined. The tilt of the EE can then, for example, exhibit a rotation angle around the effective viewing direction.

[0045] Additionally or alternatively, a longitudinal axis can be defined for typical EEs based on their geometry, e.g., for EEs that have the shape of an elongated rectangle. The tilt can then correspond, for example, to the angle between the longitudinal axes.

[0046] In an exemplary embodiment, the tilt may comprise a tilt about a rotation axis, which may be perpendicular to a waveguide surface.

[0047] This advantageously ensures that the directions along which the red and / or blue shifts occur most strongly, as described, for example, in relation to Fig. 2b, are not parallel. Thus, the unwanted influence of red and / or blue shifts can be reduced.

[0048] For example, the EEs can each have a longitudinal axis. For example, the tilt angle can correspond to an angle between the longitudinal axes. Thus, the advantages described here can be achieved by simple tilting (e.g., with the same EEs).

[0049] In one example, the EEs may each have a longitudinal axis as described herein, wherein the EEs may be configured to redirect the light incident thereon substantially equally relative to the respective longitudinal axis.

[0050] A substantially identical deflection allows the use of compatible EEs that can compensate for mutual angle-dependent spectral shifts within their respective FOVs. Furthermore, this allows for a substantially symmetrical and / or uniform arrangement of the EEs within the imaging system, enabling approximately consistent image quality across a larger portion of the imaging system's FOV.

[0051] This deflection can take place spatially, for example, as follows: If a longitudinal axis, as described herein, is defined for a rectangular EE in this example (in this example along a y-axis), the EE can, for example, have a first length along this longitudinal axis and a shorter second length along a second axis (in this example along a z-axis, where the y and z axes are perpendicular to one another). If light now falls on the EE, for example along the x-axis, which is perpendicular to the yz plane, the EE can be configured to deflect the light at least partially in the z-direction, for example so that it is effectively transmitted along the z-direction by internal reflection in the waveguide.

[0052] In one example, at least one of the EEs may comprise a hologram. Holograms are particularly well-suited as EEs because they are efficient in redirecting the incident light, can be present as thin layers, and are thus space-saving. Furthermore, holograms can be adapted to their specific use in the respective imaging system by appropriately writing / exposing them as described herein.

[0053] The holograms described herein may include, for example, a transmission hologram, a reflection hologram, a (transmission- or reflection-based) volume hologram, etc. Various exposure methods can be used to create, for example, Denisj uk holograms, image plane holograms, rainbow holograms, color holograms, multiplex holograms, computer-generated holograms, and / or digital holograms. The same applies to the AE of exemplary embodiments described below.

[0054] In the context of the imaging system according to the invention, a hologram can thus be used as a component of an imaging optics whose function is to deflect incident light into the waveguide.

[0055] To record / expose a hologram, for example, two (coherent) light sources can be used: a first exposure and a second exposure are superimposed on a medium and interfere there, so that the intensity distribution of the two superimposed waves is a function of the phase difference between the two waves. This creates an interference pattern corresponding to the phase information. The medium can, for example, comprise a photographic plate which reacts chemically to the intensity distribution / interference pattern on the photographic plate resulting from the interference of the first and second exposure, e.g. by blackening, so that the interference pattern is inscribed in the photographic plate, creating a hologram. For example, blackening can occur at locations of constructive interference, while no blackening occurs at locations of destructive interference.

[0056] If the hologram thus inscribed is illuminated with a reference wave identical to the first exposure, the original wave field is reconstructed from the interference pattern stored in the hologram, i.e. the pattern written into the medium diffracts the light of the reference wave so that its beam direction corresponds to the direction of the light from the second exposure.

[0057] The EE can, for example, be configured to redirect incident light of at least two wavelengths, e.g. for an angle and / or point of the FOV and / or an object, at least partially within the waveguide.

[0058] While EEs can in principle be configured to redirect only a specific wavelength, the EEs in this embodiment can specifically redirect at least one additional wavelength into the waveguide, e.g., if the EE comprises a hologram exposed at two wavelengths. This has the advantage that more colors can be imaged, which can improve the color diversity and quality of the image.

[0059] As described herein, holograms can be exposed not only monochromatically, but also, for example, with a plurality of wavelengths to write the hologram, so that it is configured to redirect multiple wavelengths (according to the exposure).

[0060] In one example, at least one of the EEs may comprise a three- or multi-color (e.g., four or more) hologram, preferably an RGB hologram.

[0061] Multicolored holograms can be particularly suitable for enabling images across a wide color range and producing images in (almost) original color. RGB holograms, in particular, which offer a favorable choice of exposure colors for writing the hologram, can enable images with good color reproduction.

[0062] EE can, for example, comprise holograms. These holograms can be inscribed into suitable media, e.g., photographic plates, using monochromatic light, as described herein. If, instead of a monochromatic first and second exposure (as described herein), multicolored (coherent) light is used, e.g., a red, a green, and a blue exposure can be superimposed in the first and second exposures to write so-called RGB holograms. In this case, two, three, or more beams of different wavelengths can be spatially superimposed, e.g., using dichroic mirrors. Wavelengths designated as red can, for example, encompass the spectral range from 650 nm to 750 nm. Wavelengths designated as green can, for example, encompass the spectral range from 490 nm to 575 nm. Wavelengths designated as blue can, for example, encompass the spectral range from 420 nm to 490 nm. An exemplary combination can, for example,a first and second exposure at 450 nm, 540 nm, and 650 nm, respectively. Alternatively or additionally, exposures in other wavelength ranges, e.g., ultraviolet (less than 380 nm), violet (380 nm to 420 nm), yellow (575 nm to 585 nm), orange (585 nm to 650 nm), or infrared (more than 750 nm), can also be used. Instead of multicolor exposure, two or more single-color exposed holograms can also be combined to form hologram stacks, e.g., with suitable exposure, to form an RGB stack.

[0063] If a hologram is written with multiple colors as described herein, the hologram redirects incident light of multiple wavelengths according to the exposure.

[0064] The hologram can be written into a thin layer, e.g. a photographic emulsion coated on the surface of a photographic plate, and / or photopolymers (photosensitive polymers containing one or more light-sensitive molecular groups that react to light exposure such that a photo-induced rearrangement of functional groups leads, for example, to a change in the optical and / or mechanical properties). The thin layer can comprise, for example, a carrier medium such as gelatin with embedded light-sensitive halides such as silver chloride, silver bromide or silver iodide. The impact of photons can lead to a chemical reaction of the halides, forming metallic silver. This reaction can optionally be promoted by coating the halides with dye molecules. Thus, exposure of such a film can lead to permanent inscription of the hologram by means of exposure as described herein.

[0065] In exemplary imaging systems, the tilt angle can be between 50° and 70°. As described herein, the tilt can refer to a tilt within the waveguide material or in the plane of the waveguide surface.

[0066] A tilt in the range of approximately 60° with a deviation of 10° in either direction has proven particularly advantageous when, for example, three EEs are combined. In such embodiments, the spectral angle dependence of the EEs used can be well compensated with little effort and a relatively small number of EEs, allowing images in the desired color over a relatively large area of ​​the combined FOV. Furthermore, the size of the FOV can be maximized by spanning a hexagonal overall FOV.

[0067] Likewise, more or fewer than three EEs may alternatively be used. For example, if six EEs are used, they may be arranged substantially circularly around a central AE region, as described herein.

[0068] The imaging system may, for example, further comprise at least one diffraction-based AE, wherein the at least one AE may be configured to at least partially couple the deflected light out of the waveguide.

[0069] If at least one diffraction-based AE is used in combination with the diffraction-based EE, the EE and AE can be optimally matched, for example, if they are manufactured in a similar or identical manner. This can, for example, have a positive effect on the efficiency of light deflection in the entire imaging system.

[0070] The at least one AE can, for example, be mounted on an outer side of the waveguide, be integrated into the waveguide, etc. AEs can be mounted on different sides or on the same side of the waveguide. Furthermore, a protective layer for protecting the at least one AE can be mounted on the side of the AE facing away from the waveguide. Such a protective layer can, for example, cover essentially the entire surface of the waveguide, only parts of it, or only the at least one AE.

[0071] The at least one AE may comprise, for example, a transmissive or reflective diffractive structure, a transmissive or reflective volume hologram, a mirror surface, a prism and / or a transmissive or reflective relief grating.

[0072] In one example, the EE may be configured to at least partially redirect the light incident on the EE to at least one AE.

[0073] In this exemplary embodiment, the EE and the at least one AE cooperate efficiently, ensuring efficient coupling and decoupling of light, so that the largest possible portion of the light collected by the EE is available after coupling through the AE(s), for example, to a sensor. This can have a positive effect on the image quality (e.g., contrast, sharpness, color quality, etc.) of the image.

[0074] The at least one AE can be positioned and / or oriented on the waveguide and relative to the waveguide and the EE such that the light deflected by the EE into the waveguide impinges on the at least one AE and is then coupled out of the waveguide by the at least one AE, e.g. in a direction substantially perpendicular to the waveguide surface at the location of the corresponding AE.

[0075] The at least one AE may, for example, comprise a hologram.

[0076] Holograms are particularly well-suited as optical enhancement devices because they are efficient in coupling the incident light, can be present as thin layers, and are thus space-saving. Furthermore, holograms can be adapted to their specific use in the respective imaging system and to the employed optical enhancement devices through appropriate inscription / exposure as described herein.

[0077] In principle, all functionalities described herein with regard to the EE can be transferred analogously to the AE(s). If they include a hologram, the AE can be exposed or written analogously and, in principle, exhibit the same properties.

[0078] The EE can be configured to at least partially redirect incident light of at least two wavelengths to at least one AE.

[0079] In order to achieve the highest possible color quality of the image generated by the imaging system, it may be advantageous to use EEs that are not only suitable for precisely redirecting a wavelength to at least one AE, e.g., directly or via reflection within the waveguide. This can ensure that at least two colors are well reproduced in at least part of the FOV. If, for example, holograms are used as EEs, this feature can be achieved by writing the EE, as described herein, using at least two exposures of different wavelengths to generate the hologram. Likewise, the at least one AE can be configured to at least partially couple incident light of at least two wavelengths out of the waveguide along a suitable direction, e.g., to a detection system and / or a sensor, e.g.by writing it using at least two exposures of different wavelengths, as described herein. Alternatively, stacks of monochromatic holograms can be used to perform the same or similar function as EE and / or AE, as described herein.

[0080] In exemplary imaging systems with at least two AE, one EE and one AE can form a pair.

[0081] A paired arrangement can represent a simple and efficient arrangement in which each EE has an associated AE with which it forms a pair. The imaging system can comprise several essentially identical pairs tilted relative to each other and / or different pairs that can be adjusted, for example, in their size, position, and / or orientation according to their intended function, thus optimizing the overall efficiency of the entire imaging system.

[0082] For example, a paired arrangement makes it possible to carry out a first internal optimization of the interaction of the EE and the AE of the pair and separately to coordinate the pairs of the imaging system in their interaction in image generation, e.g. with regard to the color quality of the image over the largest possible area of ​​the FOV.

[0083] For example, the EEs of a pair, as described herein, can be configured to redirect at least a portion of the light incident on the EE of the pair to the AE of the pair. When an EE and an AE are used as a pair, the EE of the pair can be configured to redirect light specifically to the respective AE of the pair, and the AE can be configured to decouple the incoming redirected light from the waveguide. This allows for precise tuning of the EE of the pair to the AE of the pair and vice versa, which can positively impact the efficiency of light coupling, redirection, and decouplement within the imaging system.

[0084] For example, the AE of a pair can be arranged substantially parallel to the EE of the pair. For this purpose, and overall, the orientation or tilt of an AE can be defined as described herein for the EE.

[0085] A parallel arrangement can achieve particularly efficient light deflection, e.g. by allowing the AE to oppose the light deflected by the EE with the largest possible area perpendicular to its effective beam path.

[0086] If, in one example, the EE and AE of a pair comprise a hologram, a characteristic axis can be defined perpendicular to the first and second exposure directions by means of which the hologram is written, as described herein. A longitudinal axis can also be defined geometrically for typical EE and / or AE, e.g., for EE and / or AE that have the shape of an elongated rectangle, the perpendicular bisector along the longitudinal extent of the rectangle.

[0087] For example, in the case of parallel EE and AE, these characteristic axes and / or longitudinal axes can be parallel. This principle can be applied equally to all other possible axes that can be defined equally for the EE and AE of a pair.

[0088] The EE and AE of a pair can, for example, be designed in such a way that the beam path between EE and AE is essentially axisymmetric.

[0089] Such an axisymmetric beam path from the EE to the AE can enable more uniform light deflection efficiency across the entire imaging area than, for example, asymmetric beam paths, since absorption losses along the beam path occur approximately equally for all paths taken by the light. This can, for example, optimize the uniformity of the image across the imaged FOV.

[0090] In exemplary embodiments, the EE and the AE can be arranged such that the EE and AE each have an axis of symmetry within them and can also be positioned and oriented relative to each other such that the pair of EE and AE have a common axis of symmetry. In such configurations, the path of the redirected light from the EE to the AE, for example, through the waveguide can run approximately in a trapezoidal region between the EE and AE. The axis of symmetry of this trapezoid can define the effective beam path of the redirected light from the EE to the AE, which in this example is then axisymmetric.

[0091] In examples where the imaging system comprises n pairs, the tilt angle can be in the range of (i8o° / n - io°) to (i8o° / n + io°).

[0092] If the n pairs are arranged according to this rule, they can cover the angular range of 180° as evenly as possible, which leads to a particularly advantageous mutual compensation of the spectral angular dependence of the individual pairs in the deflection of light from different directions of their FOV.

[0093] For example, two pairs can be arranged at approximately a 90° angle to each other, three pairs at 60° angles to each other, four pairs at 45 0 angles to each other, etc.

[0094] Furthermore, if the AEs are placed as close to each other as possible, as in the preferred embodiments described herein, the EEs can form approximately a semicircle around the position of the AEs. The more pairs used, the more finely such a semicircle can be populated with individual EEs.

[0095] Likewise, the EEs can be arranged in a circle around the position of the AE: In the example of three pairs, the AEs can be arranged directly next to each other, with an EE tilted by 0° located below the AE, an EE tilted by 60° to the right above the AE, and an EE tilted by -60° to the left above the AE. For example, the imaging system can be configured so that the EE and at least one AE are arranged substantially axially symmetrically around an axis of symmetry.

[0096] In principle, it can be advantageous to arrange the imaging system symmetrically as a whole, since in many applications this allows for the most uniform image quality possible across the FOV. Exemplary preferred symmetrical embodiments are described herein.

[0097] For example, at least one AE may have a smaller surface area than one of the EE.

[0098] Large EEs can generally be larger than AEs to collect as much light as possible, which can have a positive impact on image quality and the size of the FOV. The light collected in this way can then be redirected to comparatively small AEs, which, due to their small size, can concentrate the light, for example, to a sensor.

[0099] The size of an EE and / or AE can be measured, for example, by its area, volume, and / or extension along a characteristic axis.

[0100] In exemplary imaging systems comprising at least two AEs, a distance between a first AEs and a second AEs may be smaller than a distance between the first AEs and an EEs.

[0101] The spacing of the EE from the AEs allows the location of the input coupling and the location of the output coupling, i.e., the detection system, to be positioned appropriately depending on the imaging system's application, e.g., in windows, windshields, screens, etc., to ensure ideal functionality of both components. Furthermore, the AEs can be arranged close to each other to couple light from all AEs into the same detection system with the smallest possible aperture. The distances mentioned here can, for example, be the distances between the geometric centers of gravity of the EE and / or AEs.

[0102] In one example, a geometric center of gravity of the EE may be spaced from a geometric center of gravity of the AE, preferably by at least 10% of the minimum distance between an EE and the at least one AE.

[0103] In such exemplary configurations, the AEs can be located close together at a location where, for example, the sensor or detection system can be conveniently positioned. For example, if the imaging system is built into a screen, the AEs can be placed within the screen area and the AEs outside the usable area of ​​the screen, for example, to conceal the otherwise visible detection system within the screen frame.

[0104] The distances may refer to the distances of the geometric centers of gravity of the individual EE and / or AE as described herein and / or to the distances of other characteristic features of the EE and / or AE.

[0105] In contrast, in a circular arrangement of the EE around equally circularly arranged AE, the geometric center of gravity of the EE could be congruent with the geometric center of gravity of the AE.

[0106] For example, the waveguide may have a first and a second surface opposite the first, which are separated from each other by a substantially constant layer thickness.

[0107] Such waveguides can therefore be particularly well suited to guide the deflected light from the EE to the AE in a controlled manner by total internal reflection and with low losses, which can have a positive effect on the efficiency and image quality of the imaging system.

[0108] In an exemplary imaging system, at least one of the EEs can be arranged substantially on the first surface of the waveguide and / or the at least one AE can be arranged substantially on the second surface of the waveguide, i.e., on opposite sides of the waveguide. In another exemplary imaging system, alternatively, at least one of the EEs and / or the at least one AE can be arranged substantially on the same (first or second) surface of the waveguide.

[0109] If the EE and AE are arranged on opposite sides of the waveguide, the redirection of light from the EE to the AE is possible without reflection or by reflection within the waveguide.

[0110] In such exemplary embodiments, the EE and AE can be positioned and oriented relative to each other in the waveguide plane to optimize the redirection from the EE to the AE.

[0111] The EE and AE can be mounted on an outer side of the waveguide, integrated into the waveguide, etc.

[0112] All holograms in examples where the EE and / or the AE comprise holograms can be a transmission or reflection hologram and can also be embedded in the pane or between two panes (e.g. laminated glass).

[0113] A further aspect of the invention relates to a system comprising an imaging system as described herein and a sensor, wherein the imaging system has at least one AE configured to at least partially couple the deflected light to the sensor.

[0114] The sensor can be a suitable component directly integrated with the imaging system, enabling digital recording of the image created by the imaging system. This can enable digital post-processing and / or merging of the light contributions collected and redirected by the various EEs.

[0115] The superposition of identical and / or similar points in the images based on the light coming from different EEs on the sensor can be digitally processed and, if necessary, used to create the final image with post-image corrections. For example, shifts, distortions, different scaling, etc., can be compensated for using such digital processing, thus creating a coherent combined image.

[0116] The system may, for example, further comprise a lens, wherein the lens may be configured to at least partially couple light coupled out by the at least one AE into the sensor.

[0117] A lens can compensate for the aberration of the image and thus improve the image quality.

[0118] The function of the lens can also be at least partially integrated, for example, into the at least one AE, e.g., by the AE not only redirecting the light by changing the direction of the redirected light so that it is coupled to the sensor, but by the AE also having a focusing and / or dispersing function, for example, so that the AE, alone or in combination with a lens, applies the light appropriately to the sensor. In exemplary embodiments, the same can apply analogously to at least one of the EEs.

[0119] For example, the AE may define an AE aperture and the lens may have a lens aperture whose area may substantially correspond to the area of ​​the AE aperture.

[0120] By adjusting this way, the lens aperture can be kept small.

[0121] The AE aperture may, for example, be defined as described herein with respect to the preferred embodiments and may substantially comprise the region in which the AEs are attached to the waveguide.

[0122] In general, it is advantageous to find a compromise between sensor aperture size, waveguide thickness, EE and / or AE size and FOV in order to optimize the imaging system, for example with regard to the planned images, installation space requirements, etc. A further aspect of the invention relates to a method for producing an imaging system, which has the following steps: providing a waveguide, and generating at least two diffraction-based EE on the waveguide, preferably by means of holographic exposure, which are configured to redirect light incident on the EE at least partially within the waveguide, wherein the generation takes place in such a way that the at least two EE are tilted relative to one another at a tilt angle not equal to 0°.

[0123] The method may, for example, further comprise generating at least one diffraction-based AE on the waveguide, preferably by means of holographic exposure, wherein the at least one AE may be configured to at least partially couple out light deflected by the at least two EE from the waveguide.

[0124] Such a method can provide an imaging system according to the invention, which can thus bring about the advantages mentioned above.

[0125] The generation of at least two diffraction-based EE and / or at least one AE on the waveguide may, for example, comprise a direct generation at the final location of the EE and / or AE and / or a separate generation of the EE and / or AE and an attachment of the EE and / or AE to the waveguide.

[0126] 4. Description of the characters

[0127] Fig. ta shows a schematic view of an imaging system with an input coupling element and an output coupling element in the xz plane.

[0128] Fig. ib shows a schematic view of an imaging system with an input coupling element and an output coupling element in the xy plane.

[0129] Fig. ic shows a schematic view of an imaging system with an input coupling element and an output coupling element in the yz plane. Fig. id schematically shows the spectral distribution of the deflected light of three parallel holograms (red, green, blue) across the entire field of view of the three holograms.

[0130] Fig. 2a shows an exemplary imaging system with three coupling elements tilted relative to each other.

[0131] Fig. 2b shows schematically the spectral distribution of the deflected light of three holograms tilted by 60° to each other over the entire field of view of the three holograms.

[0132] Fig. 3a shows a schematic view of a first exemplary configuration of an imaging system with three input coupling elements and three output coupling elements in the waveguide plane.

[0133] Fig. 3b shows a schematic view of a second exemplary configuration of an imaging system with three input coupling elements and three output coupling elements in the waveguide plane.

[0134] Fig. 3c shows a schematic view of a third exemplary configuration of an imaging system with three input coupling elements and three output coupling elements in the waveguide plane.

[0135] Fig. 3d shows a schematic view of a fourth exemplary configuration of an imaging system with three input coupling elements and three output coupling elements in the waveguide plane.

[0136] Fig. 3e shows a schematic view of a fifth exemplary configuration of an imaging system with three input coupling elements and three output coupling elements in the waveguide plane.

[0137] Fig. 4a shows a schematic view of an exemplary configuration of an imaging system with three input coupling elements and a common output coupling element in the waveguide plane. Fig. 4b shows a schematic view of an exemplary exposure process of the

[0138] Output coupling element of the imaging system from Fig. 4a through a prism.

[0139] Fig. 5 shows a schematic view of an exemplary configuration of an imaging system with two input coupling elements and two output coupling elements in the waveguide plane.

[0140] Fig. 6a shows a schematic view of an imaging system with an input coupling element, an output coupling element and a waveguide with a wedge-shaped cross-section in the xz-plane.

[0141] Fig. 6b shows a schematic view of an imaging system with an input coupling element, an output coupling element and a waveguide curved in the xz plane.

[0142] 5. Detailed description of preferred embodiments

[0143] Figs. 3a to 3e show sections of various exemplary embodiments of imaging systems 10, each with three EEs 21, 22, 23 and three AEs 41, 42, 43. For the sake of clarity, only the EEs 21, 22, 23 and AEs 41, 42, 43 are shown. The imaging systems 10 may further comprise, for example, a waveguide (not shown) and optionally a detection system (not shown), as described herein, for example, with reference to Figs. 1a-1c, 6a and 6b. The imaging systems of Figs. 3a to 3e each comprise three pairs, each comprising an EE and an AE: Pair 1 with EE 21 and AE 41, Pair 2 with EE 22 and AE 42, and Pair 3 with EE 23 and AE 43. The EE 21, 22, 23 of each pair can always be configured to redirect the incident light at least partially through the waveguide to the respective AE 41, 42, 43 of the pair, as schematically illustrated by the light gray trapezoids. The viewing direction in Figs. 3a to 3e corresponds to that of Fig. 1c.In the following, the waveguide plane is to be understood (for cuboid waveguides) as the yz-plane from Fig. 1c. The tilt angles of the EE and AE herein refer to a relative tilt of the EE with respect to each other and / or the AE with respect to each other, e.g. with respect to their longitudinal axes (in the waveguide plane and / or in a projection plane (e.g. for curved waveguides and / or waveguides with non-parallel surfaces)). For each EE, an effective direction results along which it redirects light to the corresponding AE. This can, for example, be defined geometrically as the axis passing through the geometric center of gravity of the EE and the geometric center of gravity of the AE. The relative tilt can therefore also include a relative tilt of the axes through the respective geometric centers of gravity (marked as dashed lines in Fig. 3a).If an EE and an AE are arranged axially symmetrically to each other, the axis can coincide with the axis of symmetry of the pair consisting of EE and AE and pass through the center of the trapezoid which, as described herein, is covered by all rays from the EE to the AE.

[0144] Fig. 3a schematically shows a view of a first exemplary configuration of an imaging system 10 with three EEs 21, 22, 23 and three AEs 41, 42, 43 in the waveguide plane. All three pairs in Fig. 3a comprise the same EEs 21, 22, 23 and AEs 41, 42, 43, differing only in their relative positioning and orientation. The first pair 21, 41 is tilted by -60° in the waveguide plane relative to the second pair 22, 42, and the third pair 23, 43 is tilted by +60° in the waveguide plane relative to the second pair 22, 42. The AE 41, 42, 43 are arranged in such a way that their corners pointing in the direction of the EE 21, 22, 23 of the respective pair lie approximately on a common circular path (dotted circular path in Fig. 3a) and each touches (or lies close to) a corner of adjacent AE (AE 41 and AE 42 as well as AE 42 and AE 43).

[0145] The first pair 21, 41 has the symmetry axis Si, the second pair 22, 42 the symmetry axis S2, and the third pair 23, 43 the symmetry axis S3. In each pair, the EE 21, 22, 23 and AE 41, 42, 43 are designed such that the trapezoid (in light gray) spanned by the beam path between EE 21, 22, 23 and AE 41, 42, 43 is essentially axially symmetrical relative to the respective symmetry axis Si, S2, S3 of the pair described herein. Due to the symmetrical arrangement of the three pairs, the axis S2 also represents an axis of symmetry for the entire imaging system io.

[0146] The AEs 41, 42, 43 can define an AE aperture, e.g., the area within the dotted circular path in Fig. 3a. Other definitions of the AE aperture are also possible, e.g., the smallest possible circle, the smallest possible hexagon, pentagon, quadrilateral, triangle, and / or other possible geometric shape and / or construction that can be drawn around the AE in the waveguide plane. In principle, an optional detection system (not shown, see, for example, Figs. 1a and 1b) can have an objective aperture. Its area can essentially correspond to the area of ​​the AE aperture to ensure mutual coordination of the components of the system. The following Figs. 3b to 3e show exemplary embodiments that, among other things, reduce the area of ​​the AE aperture compared to the embodiment of Fig. 3a.

[0147] Fig. 3b schematically shows a second exemplary configuration of an imaging system 10 with three EEs 21, 22, 23 and three AEs 41, 42, 43 in the waveguide plane. Pair 1 with EEs 21 and AE 41 and pair 3 with EEs 23 and AE 43 are positioned closer together compared to the corresponding elements in Fig. 3a, so that the corners of AEs 41 and AE 43 closest to the center of the imaging system 10 touch (or nearly touch). Otherwise, pairs 1 and 3 have the same size and relative positioning as in the imaging system 10 in Fig. 3a.

[0148] In addition, the imaging system of Fig. 3b has a second pair with EE 22 and AE 42. The AE 42 is moved downwards so that its two upper corners each touch (or almost touch) a corner of the AE 41 and the AE 43. Thus, the AE aperture (dashed circular path) is smaller than that in Fig. 3a (see dotted circular path for comparison). The EE 22 of the second pair, like the AE 42 of the second pair, is moved downwards in relation to its position in Fig. 3a and its longitudinal extent is also reduced (see the dotted rectangle the size of the EE 22 from Fig. 3a for comparison). This size reduction is necessary to ensure that the EE 22 does not lie within the trapezoidal area in which light is deflected from the EE 21 to the AE 41 or from the EE 23 to the AE 43 within the wave rider. Otherwise, the deflected light could hit the EE 22 and be unintentionally deflected from there and thus be lost for the image.

[0149] In the imaging system io of Fig. 3b, all three pairs as well as the imaging system 10 as a whole are axially symmetric.

[0150] Thus, the imaging system 10 of Fig. 3b has large EE 21, 22, 23 and AE 41, 42, 43 relative to the AE aperture compared to the one in Fig. 3a, which has a beneficial effect on image contrast and vignetting (the darkening of the image at the edges of the FOV). However, since a reduction in the size of the EE 22 is necessary, the FOV and / or the color information of the EE 22 and thus of the imaging system 10 as a whole is reduced.

[0151] Fig. 3c schematically shows a third exemplary configuration of an imaging system 10 with three EEs 21, 22, 23 and three AEs 41, 42, 43 in the waveguide plane. The AEs 41, 42, 43 are arranged exactly as in Fig. 3b. However, the EEs 21, 22, 23 differ from those in the imaging system 10 of Fig. 3b: The EE 22 has its full size, as in Fig. 3a, for example, while the longitudinal extent of the EEs 21, 23 is reduced on the side facing the EE 22 (see dotted rectangles in the size of the EEs 21, 23 from Fig. 3a). This size reduction is necessary to ensure that the EE 22 does not lie within the trapezoidal regions where light is deflected from the EE 21 or EE 23 to the AE 41 or AE 43 within the wave rider, and represents an alternative approach to the length reductions of the EE 22 described with reference to Fig. 3b. Otherwise, the deflected light could hit the EE 22 and be unintentionally deflected from there, thus being lost for imaging.

[0152] As a result, in the imaging system 10 of Fig. 3c, the two outer pairs 121, 41 and 3 23, 43 are not axially symmetric, but the inner pair 2 22, 42 and the imaging system 10 as a whole are axially symmetric.

[0153] This results in similar advantages and disadvantages for the imaging system 10 of Fig. 3c (compared to that of Fig. 3a) as for the imaging system 10 of Fig. 3b. Fig. 3d schematically shows a fourth exemplary configuration of an imaging system 10 with three EE 21, 22, 23 and three AE 41, 42, 43 in the waveguide plane.

[0154] The AEs 41, 42, 43 are arranged relative to one another in such a way that the two corners on one of the short side edges each touch (or almost touch) a corner on one of the short side edges of the two adjacent AEs. The EEs 21, 22, 23 are spaced from the respective AEs 41, 42, 43 of the respective pair in the same way as in Figs. 3a to 3c. To prevent overlap of the EEs 22 and 23, both are reduced in their longitudinal extent (see dotted rectangles the size of the EEs 22, 23 from Fig. 3a for comparison). As a result, neither the imaging system 10 as a whole nor the pairs 22, 42 and 32, 43 are inherently symmetrical. Only the pair 121, 41 is axially symmetrical.

[0155] Fig. 3e schematically shows a fifth exemplary configuration of an imaging system 10 with three EE 21, 22, 23 and three AE 41, 42, 43 in the waveguide plane.

[0156] The AE 21, 23 are slightly reduced in size compared to Fig. 3a to 3d, so that the AE 41, 42, 43 are arranged in a compact arrangement within the dashed circle (the AE aperture) without a size reduction of any of the EE 21, 22, 23 being necessary.

[0157] Thus, the configuration of the imaging system 10 shown in Fig. 3e manages to keep the AE aperture small while simultaneously keeping the size of the AEs 21, 22, and 23 large. The size reduction of the AEs 41 and 43 only negatively affects the color information, the contrast, and, with regard to vignetting, the image quality.

[0158] Fig. 4a shows a schematic view of an exemplary configuration of an imaging system with three EEs 21, 22, 23 and a common AE 40, which can be arranged, for example, in a waveguide plane. The EEs 21, 22, 23 are configured to redirect light incident on the EEs 21, 22, 23 at least partially within the waveguide to the AE 40. The one AE 40 is then configured to at least partially couple the redirected light coming from the three EEs 21, 22, 23 out of the waveguide to the detection system (not shown). If the AE 40 comprises, for example, a hologram, this can be described by its exposure in such a way that it can fulfill this function. One possibility for carrying out such an exposure is described in detail in Fig. 4b.

[0159] Essentially, the AE 40 from Fig. 4a fulfills the functions of the three AEs from Figs. 3a to 3e simultaneously. By suitable manufacture of the AE 40 (as shown by way of example in Fig. 4b), filtering effects can be avoided that would otherwise occur if several AEs were arranged one before the other in the direction of the output of the deflected light. Thus, the AE aperture of the imaging system 10 from Fig. 4a is particularly small (dashed circle), for example, compared to the AE aperture of the imaging system 10 from Fig. 3a (see dotted circle for comparison), and the size of the EEs 21, 22, 23 does not have to be reduced, for example to avoid possible overlaps of the EEs 21, 22, 23 with each other and / or with the beam path of neighboring EEs 21, 22, 23.

[0160] Fig. 4b schematically shows an exemplary exposure process of the AE 40 of the imaging system 10 from Fig. 4a through a prism 60. For this purpose, three first exposures B1-1, B1-2, B1-3, as described herein, are combined and applied to the AE 40 by exposure through a prism 60 in order to write a hologram there. In addition, a second exposure B2-1, B2-2, B2-3 for all three first exposures B1-1, B1-2, B1-3 is also directed onto the AE 40, so that interference occurs there and the functions that were distributed across three AEs in Figs. 3a to 3e are written into a common AE 40. A hologram produced in this way can be configured to couple out / redirect deflected light from three different directions (the directions of the first exposures B1-1, B1-2, B1-3) into a common direction (the direction of the second exposures B2-1, B2-2, B2-3).The first exposures B1-1, B1-2, B1-3 and / or the second exposure B2-1, B2-2, B2-3 may be, for example, monochromatic or multi-color (e.g., RGB) as described herein.

[0161] In addition to imaging systems with three EEs (as shown in Fig. 3a to 4a), imaging systems with more or fewer EEs are also possible. Fig. 5 schematically shows an exemplary configuration of an imaging system io with two EEs 21, 22 and two AEs 41, 42 in the waveguide plane:

[0162] The two EEs 21, 22 are tilted by 90° relative to each other in the plane of the waveguide (not shown). The same applies to the AEs 41, 42. The imaging system 10 essentially comprises two pairs: Pair 1 comprising EEs 21 and AEs 41, and Pair 2 comprising EEs 22 and AEs 42.

[0163] While in Figs. 1a to 1c imaging systems with waveguides with essentially cuboidal waveguides are shown for the sake of simplicity, other waveguide shapes are also possible:

[0164] For example, Fig. 6a shows a view of an imaging system 10 with an EE 20, an AE 40, and a waveguide 30 with a wedge-shaped cross-section in the xz plane. The two side surfaces of the waveguide 30, to which either the EE 20 or the AE 40 is attached, are not parallel to each other. The AE 40 couples the deflected light to the detection system 50 as described herein.

[0165] Fig. 6b schematically shows a view of an imaging system 10 with an EE 20, an AE 40, and a waveguide 30 curved in the xz plane. The exemplary waveguide 30 has a constant thickness and a curvature in the xz plane. Additionally or alternatively, the waveguide 30 could also have a curvature in the xy and / or yz plane. The respective curvature could be uniform or non-uniform on different sections of the waveguide 30, up to and including completely irregular curvatures. The AE 40 couples the redirected light to the detection system 50 as described herein.

[0166] Neither the relative inclination of the two side surfaces of the waveguide 30 from Fig. 6a nor the curvature of the waveguide from Fig. 6b represent an obstacle to the functionality of the imaging system 10. The functionalities described herein can be transferred to the imaging system 10 from Figs. 6a and 6b and the coupling to the respective detection system 50 takes place as described herein.

Claims

CLAIMS 1. An imaging system (io) comprising: a waveguide (30); and at least two diffraction-based coupling elements, EE (21, 22, 23); wherein the at least two EE (21, 22, 23) are configured to redirect light incident on the EE (21, 22, 23) at least partially within the waveguide (30); wherein the at least two EE (21, 22, 23) are tilted relative to one another at a tilt angle of not equal to 0°.

2. The imaging system (10) of claim 1, wherein the tilt comprises a tilt about a rotation axis perpendicular to a waveguide surface.

3. Imaging system (10) according to claim 1 or 2, wherein the EE (21, 22, 23) each have a longitudinal axis, and the tilt angle corresponds to an angle between the longitudinal axes.

4. Imaging system (10) according to one of claims 1 - 3, wherein the EE (21, 22, 23) each have a longitudinal axis, and wherein the EE (21, 22, 23) are configured to deflect the light incident on them substantially equally relative to the respective longitudinal axis.

5. Imaging system (10) according to one of claims 1 - 4, wherein at least one of the EE (21, 22, 23) comprises a hologram.

6. Imaging system (10) according to one of claims 1 - 5, wherein the EE (21, 22, 23) are configured to redirect incident light of at least two wavelengths at least partially within the waveguide (30). 7- Imaging system (io) according to one of claims 1 - 6, wherein at least one of the EE (21, 22, 23) comprises a three- or multi-color hologram, preferably an RGB hologram.

8. Imaging system (10) according to one of claims 1 - 7, wherein the tilt angle is between 50° and 70°.

9. Imaging system (10) according to one of claims 1 - 8, further comprising at least one diffraction-based coupling-out element, AE (41, 42, 43), wherein the at least one AE (41, 42, 43) is configured to at least partially couple the deflected light out of the waveguide (30).

10. Imaging system (10) according to claim 9, wherein the EE (21, 22, 23) are configured to at least partially redirect the light incident on the EE (21, 22, 23) to at least one AE (41, 42, 43).

11. Imaging system (10) according to one of claims 9 or 10, wherein the at least one AE (41, 42, 43) comprises a hologram.

12. Imaging system (10) according to one of claims 9 - 11, wherein the EE (21, 22, 23) are configured to at least partially redirect incident light of at least two wavelengths to at least one AE (41, 42, 43).

13. Imaging system (10) according to one of claims 9 - 12 with at least two AE (41, 42, 43), wherein in each case one EE (21, 22, 23) and in each case one AE (41, 42, 43) form a pair.

14. Imaging system (10) according to claim 13, wherein the EE (21, 22, 23) of a pair are arranged to redirect at least a portion of the light incident on the EE (21, 22, 23) of the pair to the AE (41, 42, 43) of the pair.

15. Imaging system (10) according to one of claims 13 or 14, wherein the AE (41, 42, 43) of a pair is arranged substantially parallel to the EE (21, 22, 23) of the pair.

16. Imaging system (io) according to one of claims 13 - 15, wherein the EE (21, 22, 23) and AE (41, 42, 43) of a pair are designed such that the beam path between EE (21, 22, 23) and AE (41, 42, 43) is substantially axially symmetrical.

17. Imaging system (10) according to one of claims 13 - 16, wherein the imaging system (10) comprises n pairs and the tilt angle is in the range of (i8o° / n - io°) to (i8o° / n + io°).

18. Imaging system (10) according to one of claims 9 - 17, wherein the EE (21, 22, 23) and the at least one AE (41, 42, 43) are arranged substantially axially symmetrically about an axis of symmetry.

19. Imaging system (10) according to one of claims 9 - 18, wherein the at least one AE (41, 42, 43) has a smaller surface area than one of the EE (21, 22, 23).

20. Imaging system (10) according to one of claims 9 - 19, comprising at least two AE (41, 42, 43), wherein a distance between a first AE (41, 42, 43) and a second AE (41, 42, 43) is smaller than a distance between the first AE (41, 42, 43) and an EE (21, 22, 23).

21. Imaging system (10) according to one of claims 9 - 20, wherein a geometric center of gravity of the EE (21, 22, 23) is spaced from a geometric center of gravity of the AE (41, 42, 43), preferably by at least 10% of the minimum distance between an EE (21, 22, 23) and the at least one AE (41, 42, 43).

22. Imaging system (10) according to one of claims 1 - 21, wherein the waveguide (30) has a first and a second surface opposite the first, which are separated from each other by a substantially constant layer thickness. 23- Imaging system (io) according to claim 22, dependent on any one of claims 9-21, wherein at least one of the EE (21, 22, 23) is arranged substantially on the first surface of the waveguide (30); and / or the at least one AE (41, 42, 43) is arranged substantially on the second surface of the waveguide (30).

24. A system comprising: an imaging system (10) according to any one of claims 1-23; and a sensor; wherein the imaging system (10) has at least one diffraction-based coupling element, AE (41, 42, 43), configured to at least partially couple the deflected light to the sensor.

25. The system of claim 24, further comprising a lens, wherein the lens is configured to at least partially couple light coupled out by the at least one AE (41, 42, 43) into the sensor (50).

26. The system of claim 25, wherein the AE (41, 42, 43) define an AE aperture; and wherein the objective has an objective aperture whose area substantially corresponds to the area of ​​the AE aperture.

27. A method for manufacturing an imaging system (10) comprising the following steps: Providing a waveguide (30); and Generating at least two diffraction-based coupling elements, EE (21, 22, 23), on the waveguide (30), preferably by means of holographic exposure, which are configured to redirect light incident on the EE (21, 22, 23) at least partially within the waveguide (30); wherein the generation takes place such that the at least two EE (21, 22, 23) are tilted relative to one another at a tilt angle not equal to 0°.

28. The method of claim 27, further comprising: Generating at least one diffraction-based coupling-out element, AE (41, 42, 43), on the waveguide (30), preferably by means of holographic exposure; wherein the at least one AE (41, 42, 43) is configured to at least partially couple out light deflected by the at least two EE (21, 22, 23) from the waveguide (30).

Images