SCREEN WITH A TRANSPARENT BASE BODY

Description

[0001] The present invention relates to a functionalized waveguide for a detector system.

[0002] Functionalized waveguides according to the prior art are disclosed in WO 2015 / 139761 A1, which discloses an imaging system suitable for providing an image of a surface portion of an object, comprising a light source arranged to provide a light beam, at least one first optical waveguide having a first surface and a second surface opposite the first surface, wherein the first surface comprises an input coupling surface, the optical waveguide comprises an output coupling surface and a first diffraction grating arranged on the optical waveguide.

[0003] Transparent surfaces made of glass or plastic, such as windows or windshields in cars, have a transparent base body and are generally used only to protect people or objects from environmental influences such as wind, temperature, particles or radiation.

[0004] There is increasing interest in providing such a transparent base body that provides additional optical functionality.

[0005] It is therefore an object of the invention to provide a transparent base body with additional optical functionality.

[0006] The invention is defined in the independent claims. Advantageous embodiments are specified in the dependent claims.

[0007] The functionalized waveguide described below is designed as a screen with a transparent base body.

[0008] In the functionalized waveguide, a partially transparent coupling region and an output region spaced from it in a first direction are provided or formed in the transparent base body. The partially transparent coupling region can have a diffractive structure with which the transparency of the coupling region is maintained under normal viewing conditions over a wide angular and wavelength range. Thus, only a portion of the radiation impinging on a front side of the transparent base body can be deflected by the transparent coupling region in such a way that the deflected portion propagates as coupled radiation into the base body by reflection to the output region and impinges on the output region.

[0009] The transparency of the coupling region depends on the efficiency of the radiation coupling. As the coupling efficiency increases, the transparency in the coupling region of the functionalized waveguide also decreases. To achieve the greatest possible transparency, the radiation coupling through, for example, the diffractive structure (in particular the at least one volume hologram) can be just efficient enough to ensure that sufficient radiation power reaches the coupling-out region. The partially transparent coupling region can be designed such that the coupling efficiency is, for example, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%. In particular, the coupling efficiency can be in the range of 2% - 50%, so that the transparency of the coupling region is in the range of 50% - 98%. The coupling region(s) of the further exemplary embodiments can also have such coupling efficiencies or such transmissive properties.

[0010] The transparent coupling region is preferably designed such that the deflection of the deflected part of the radiation striking the front side of the transparent base body takes place as a pure deflection, which is free from an imaging optical function (e.g. free from a focusing effect).

[0011] The reflections can, in particular, be total internal reflections on the front and / or back of the transparent base body. However, it is also possible that reflective layers or coatings, or partially reflective layers or coatings, are provided for this purpose.

[0012] The front and back of the semi-transparent body can be designed as flat surfaces. For example, the semi-transparent base body can be designed as a plane-parallel plate.

[0013] However, it is also possible that the front and / or the back are curved.

[0014] The semi-transparent base body can be made of glass and / or plastic. It can be a single piece or have a multi-layer structure.

[0015] In particular, the transparent base body can be transparent to radiation or light in the visible wavelength range. Furthermore, it can be transparent to the near infrared and / or infrared range.

[0016] The output region of the transparent base body can deflect at least a portion of the coupled radiation impinging on it such that the deflected portion exits the base body. This preferably occurs via the front or back of the transparent base body.

[0017] The coupling-out region can be partially transparent. In particular, the coupling-out efficiency of the coupling-out region can be, for example, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. In particular, the coupling-out efficiency of the coupling-out region can be in the range of 2% - 50%, so that the transparency of the coupling-out region is in the range of 50% - 98%. The coupling-out region(s) of the further embodiments can also have such coupling efficiencies or such transmissive properties.

[0018] The partially transparent design is advantageous, for example, when the input and output regions are designed as diffractive structures (e.g., volume holograms). In this case, the input and output regions can be formed, for example, in a single film, which is advantageous from a manufacturing perspective.

[0019] However, it is also possible for the output coupling area to have maximum output efficiency. This can be achieved, for example, by mirroring (preferably complete mirroring).

[0020] The input coupling region and the output coupling region can be designed such that they do not perform any optical imaging function in addition to deflection. However, it is also possible for the input coupling region and / or the output coupling region to provide an optical imaging function in addition to deflection and thus perform optical imaging. For example, the optical imaging function can implement the function of a converging lens or diverging lens, a concave or convex mirror, whereby the curved surfaces (centered or decentered) can be spherically curved or aspherically curved.

[0021] The diffractive structure of the coupling region can be realized as a buried diffractive structure, as a diffractive structure between two substrates or as a diffractive structure formed on the front or back side.

[0022] Furthermore, the coupling-out region can have a diffractive structure. The diffractive structure of the coupling-out region can be formed as a buried diffractive structure or as a diffractive structure on the front or back side.

[0023] A reflective or transmissive volume hologram can be provided as the diffractive structure of the input or output region. Furthermore, the diffractive structure of the input or output region can be a transmissive or reflective relief grating.

[0024] The output coupling region may further comprise a mirror surface, a prism, and / or a reflective or transmissive Fresnel structure. These variants can be provided as an alternative to the diffractive structure or in addition to the diffractive structure of the output coupling region.

[0025] The screen can be referred to as a detector system, which will also be referred to as a detection system below, since the portion of the radiation deflected by the output coupling area hits the image sensor. The image sensor can be connected to the front or back of the base body. In particular, a direct connection can be provided. The image sensor can be a digital image sensor (e.g., a CCD sensor or a CMOS sensor).

[0026] Furthermore, the detector system can be designed such that at least one optically imaging element is arranged in the region between the image sensor and the front or back side. The at least one optically imaging element can be designed, for example, as a lens, as a refractive lens, or as a refractive camera lens. It is also possible for the region between the image sensor and the front or back side to be free of imaging optical elements. In other words, the radiation coupled out by the coupling-out region thus strikes the image sensor without having passed through further optically imaging elements. In this case, it is advantageous if the coupling-out region has an optically imaging property in addition to deflection.

[0027] The functionalized waveguide can be designed to perform an infinity-to-infinity mapping. However, it is also possible for it to perform a finite-to-infinite mapping, an infinite-to-finite mapping, or a finite-to-finite mapping.

[0028] The detector system can, of course, also be designed such that at least one optically imaging element is arranged between the image sensor and the front or rear side. The at least one optically imaging element serves in particular to guide the portion of the radiation deflected by the output region and can be designed, for example, as a lens.

[0029] The at least one optically imaging element can be designed, for example, as a lens, as a refractive lens or as a refractive camera lens.

[0030] In the functionalized waveguide, the extent of the coupling region in a second direction perpendicular to the first direction can be greater than the extent of the coupling-out region in the second direction. The extent (or, for example, width) of the coupling region is understood here to mean, in particular, the extent effectively used as intended or the optically used extent. This is, for example, the extent of that section of the coupling region from which the deflected radiation strikes the detector system. The extent (or, for example, width) of the coupling-out region is understood here to mean, in particular, the extent effectively used as intended or the optically used extent. This is, for example, the extent of that section of the coupling-out region from which the deflected radiation strikes the detector system.

[0031] Furthermore, the coupling region and the coupling-out region can be arranged centered relative to one another in the second direction.

[0032] However, it is also possible that the coupling-in region and the coupling-out region are arranged decentered to each other in the second direction.

[0033] Several coupling-out regions can be provided, arranged side by side in the second direction. At least one of the coupling-out regions can additionally have the function of deflection transverse to the first direction.

[0034] The field of view (hereinafter referred to as "field of view" or "FoV") of the functionalized waveguide can be adjusted to the FoV of the image sensor (or of the image sensor with the at least one optically imaging element, e.g., a lens). This can be achieved, in particular, by adjusting the distance between the coupling region and the coupling-out region along the first direction and the extent of the coupling region transverse to the first direction and the extent of the coupling-out region transverse to the first direction. Adjusting the FoV of the image sensor (or of the image sensor with the at least one optically imaging element) to the FoV of the functionalized waveguide can be achieved by adjusting the lens focal length and / or the size of the image sensor. Preferably, the FoV of the functionalized waveguide corresponds to the FoV of the image sensor (or of the image sensor with the at least one optically imaging element).This can be achieved by a targeted adjustment of the FoV of the functionalized waveguide and / or a targeted adjustment of the FoV of the image sensor (or the image sensor with the at least one optically imaging element).

[0035] In the functionalized waveguide of the detector system, the input coupling region can comprise at least two volume holograms, each of which deflects only a portion of the radiation coming from an object to be detected and striking the front side in such a way that the deflected portion propagates as coupled-in radiation in the base body by reflection to the output coupling region and strikes the output coupling region. The volume holograms of the input coupling region can differ in that their deflection function has different spectral angular properties. This allows different wavelengths to be deflected at the same angle of incidence. The output coupling region deflects at least a portion of the coupled-in radiation striking it in such a way that the deflected portion exits the base body (preferably via the front or back) to strike the detector system.

[0036] With such a waveguide, more colors can be transmitted because the volume holograms of the coupling area have different spectral angle properties and thus, at the same angle of incidence, redirect different wavelengths so that they become part of the coupled radiation in the base body.

[0037] The volume holograms of the coupling region can be arranged adjacently (with or without spacing from one another), in particular they can be arranged adjacently in the first direction. However, it is also possible for the volume holograms of the coupling region to be arranged one above the other or on top of the other (i.e. preferably in a stacking direction that is transverse to the first direction and transverse to the second direction), so that a layer stack of volume holograms is essentially present. Alternatively or additionally, the functions of some or all of the volume holograms of the coupling region can be implemented in a single volume hologram. Such an implementation is also called multiplexing. These possible configurations of the coupling region can be provided in all of the described embodiments.

[0038] The output region can have an associated volume hologram for each volume hologram of the input region, which provides the same spectral angle properties during deflection as the corresponding volume hologram of the input region. This allows the dispersion of the volume holograms of the input region to be compensated.

[0039] The volume holograms of the output region can be arranged adjacently (with or without spacing from one another), in particular they can be arranged adjacently in the first direction. However, it is also possible for the volume holograms of the output region to be arranged one above the other or on top of the other (i.e. preferably in a stacking direction that is transverse to the first direction and transverse to the second direction), so that a layer stack of volume holograms is essentially present. Alternatively or additionally, the functions of some or all of the volume holograms of the output region can be implemented in a single volume hologram. Such an implementation is also called multiplexing. These possible configurations of the output region can be provided in all described embodiments.

[0040] The volume holograms of the input region can be designed as reflective or transmissive volume holograms. The same applies to the volume holograms of the output region.

[0041] The coupling region can have at least or exactly 2, 3, 4, 5, 6, 7, 8, 9, 10, up to 40, up to 50 or up to 100 (or any value between 1 and 100) volume holograms.

[0042] In the functionalized waveguide of the detector system, the coupling region may have a plurality of diffractive coupling structures that are adjacent in the first direction and differ in that they have different horizontal fields of view in a plane spanned by a normal to the front side and a second direction transverse to the first direction, so that they redirect radiation from the different horizontal fields of view towards the coupling-out region.

[0043] This allows a larger horizontal field of view to be captured and directed to a detector.

[0044] The diffractive coupling structures can be designed to redirect the radiation from the different horizontal fields of view towards the coupling-out area.

[0045] This allows a larger horizontal field of view to be captured and directed to a detector.

[0046] The diffractive coupling structures can be designed in such a way that they encode the radiation from the different horizontal fields of view when deflected by different deflected wavelengths, so that the coupling out and / or detection is possible selectively for the different horizontal fields of view.

[0047] The coupling-out region can have an associated diffractive coupling-out structure for the diffractive coupling-in structure, which selectively deflects radiation with wavelengths of the associated diffractive coupling-in structure.

[0048] The diffractive coupling structures can redirect the radiation from the associated coupling structures so that they hit spatially different areas of a detector system.

[0049] A color filter can be provided for at least one spatially different area of ​​the detector, which only directs the corresponding wavelength range to the detector.

[0050] The diffractive coupling structures can be designed to encode the radiation from the different deflection angle ranges, so that the coupling and / or detection is possible selectively for the different horizontal fields of view.

[0051] The coupling region may have a shading aperture with a louvre structure in front of each diffractive coupling structure, which defines a different vertical field of view for each diffractive coupling structure in a plane spanned by a perpendicular to the front side and the first direction.

[0052] The coupling-out region can have an associated diffractive coupling-out structure for each diffractive coupling structure, which selectively deflects radiation from the different deflection angle ranges of the associated diffractive coupling structures. The diffractive coupling-out structures can be arranged adjacent to the first direction.

[0053] The diffractive output structures can be designed as reflective or transmissive volume holograms.

[0054] The functionalized waveguide of the detector system can be designed or further developed such that the coupling region along the second direction has at least two different diffractive coupling structures which differ in that they have a different deflection component in the second direction.

[0055] This results in greater efficiency in the utilization of the coupled radiation.

[0056] The deflection component in the second direction can be selected for each of the diffractive coupling structures that are offset along the second direction to the coupling-out region such that the existing offset is compensated for the coupled-in radiation.

[0057] The coupling-out region can be designed in such a way that it deflects the radiation coupled in by the different diffractive coupling structures into the same angular range.

[0058] The functionalized waveguide of the detector system can be designed or further developed such that the coupling region comprises an input coupling relief grating and the output coupling region comprises an output coupling relief grating.

[0059] In particular, the input coupling relief grating and the output coupling relief grating can have the same grating period.

[0060] The screen may, for example, be the screen of a portable device (such as a smartphone or a laptop), a stationary screen or another screen installed, for example, in a motor vehicle.

[0061] The coupling-out region can be arranged closer to the edge of the base body along the first direction than the coupling-in region.

[0062] Furthermore, the coupling area can be arranged on the rear side.

[0063] The coupling region can be arranged between the base body and the light-emitting layer.

[0064] The image sensor may be arranged on the rear side of the base body in an area that serves as the display area of ​​the screen and that is darkened during recording by means of the image sensor.

[0065] The screen may have an additional camera that captures the object, with the camera's image being used to colorize a picture of the object using the image sensor.

[0066] The screen according to the invention has a light-emitting layer arranged on the back of the base body, which generates a real image. For this purpose, the light-emitting layer can, for example, have light-emitting pixels. In this case, the real image is generated in the plane of the pixels. The pixels can each have a radiation angle of at least 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, or less than 180°.

[0067] Since this pixelated light-emitting layer is arranged on the back of the base body, the light emitted by the pixels is transmitted through the base body and reaches a viewer.

[0068] To prevent light emitted by the light-emitting layer from being diffracted by the diffractive structure of the coupling region and thus not reaching the viewer, the diffractive structure of the coupling region can be designed so that only light with a specific polarization is diffracted and thus guided in the base body (or waveguide). The light emitted by the light-emitting layer can then have a polarization that is inefficient for the diffractive structure of the coupling region and transmit undisturbed through the diffractive structure of the coupling region. This means that the light-emitting layer no longer represents a source of stray light, and it is no longer necessary to darken or omit the pixelated light-emitting layer in the coupling region during recording using the image sensor to prevent the coupling of stray light.

[0069] Possibilities for a defined polarization would include LCD displays or the application of a polarizing film between the light-emitting layer and the base body.

[0070] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

[0071] The invention is explained in more detail below using exemplary embodiments with reference to the accompanying drawings, which also disclose features essential to the invention. These exemplary embodiments are for illustrative purposes only and are not to be interpreted as restrictive. For example, a description of an embodiment with a large number of elements or components should not be interpreted to mean that all of these elements or components are necessary for implementation. Rather, other embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different exemplary embodiments may be combined with one another unless otherwise stated. Modifications and variations described for one of the exemplary embodiments may also be applicable to other exemplary embodiments.To avoid repetition, identical or corresponding elements in different figures are designated by the same reference numerals and are not explained more than once. Figuren 29 - 32 Examples of embodiments of the screen according to the invention are shown. The functionalized waveguide used (also in connection with non-inventive embodiments) is shown in Figuren 1 - 28 described). The figures show: Fig. 1 is a side view of an embodiment of a detector system not according to the invention; Fig. 2 is a plan view of the waveguide 1 of Fig. 1 ; Fig. 3 a top view of the waveguide 1; Fig. 4 a schematic representation of the spectrally resolved, angle-dependent deflection efficiency of the reflective volume hologram of the input coupling region 4; Fig. 5 a schematic representation of the deflection efficiency for three different angles of incidence as a function of the wavelength; Fig. 6 an enlarged detail of a side view to explain the averaging effected by the detector pixels over a defined angular range; Figs. 7A-7C top views of the waveguide to explain different width ratios between the input coupling and output coupling regions; Fig. 7D a top view to explain the possible restriction of the horizontal field of view in a detector system 2 with objective 1; Figs. 8A and 8B further embodiments of the functionalized waveguide 1; Fig.8C shows an enlarged side view of the coupling-out region of the waveguide 1 to explain a possible reduction of the vertical field of view; Figs. 9A and 9B show illustrations to explain the production of a volume hologram for the coupling-in region; Fig. 10 shows a plan view of the waveguide according to a further embodiment; Figs. 11A-F show side views of the coupling-in region of the waveguide of . Fig. 10 ; Fig. 12 a schematic representation of the spectrally resolved, angle-dependent deflection efficiency of the coupling region according to Fig. 10 ; Fig. 13A-13C schematically shows the deflection efficiency of different angles of incidence as a function of the wavelength; Fig. 14A-F schematic side views to explain the coupling-out region of the waveguide according to Fig. 10 ; Fig. 15 schematic representation of the spectrally resolved, angle-dependent deflection efficiency for the coupling region of a waveguide with 40 different volume holograms; Fig. 16 a plan view of a waveguide not according to the invention according to a further embodiment; Fig. 17 a view from above of the waveguide of Fig. 16 ; Fig. 18A, 18B Side views of the coupling area to explain the operation of the waveguide according to Figuren 16 und 17 ; Fig. 19A-19C shows schematically the angle of incidence and spectrally dependent efficiency of the laterally offset coupling volume holograms of the waveguide according to Fig. 16 ; Fig. 20 shows schematically the spectral angle-dependent spectrum of the output holograms of the embodiment according to Fig. 16 including spectral filtering; Figs. 21 and 22 show plan views of two different waveguides 1 to explain a further embodiment; Fig. 23 shows a side view of a further embodiment of the waveguide not according to the invention; Fig. 24 shows a schematic representation of the geometric transmission spectrum of the waveguide according to Fig. 23 ; Fig. 25 an enlarged side view of the output coupling area of ​​the waveguide of Fig. 23 ; Fig. 26 a schematic representation of the geometric transmission spectrum with vignetting through the entrance pupil of the detector system; Fig. 27 schematically shows a simulated cross-section through a grating period of the buried coupling grating of the waveguide according to Fig. 23 ; Fig. 28 shows schematically the diffraction efficiency of the relief grating as a function of wavelength; Fig. 29 shows the top view of an embodiment according to the invention; Fig. 30 shows a side view of the embodiment of Fig. 29 ; Fig. 31 shows a further embodiment of the invention, and Fig. 32 shows the side view of Fig. 31 .

[0072] The views according to Fig. 1 bis 3 show an embodiment of a functionalized waveguide 1 together with a detector system 2 to realize a camera 3.

[0073] The waveguide 1 comprises a coupling region 4 and a coupling region 5 spaced therefrom and can, as in Fig. 1 bis 3 shown, be formed on a plane-parallel plate 6 with a flat front side 7 and a flat back side 8. The plane-parallel plate 6, which can also be referred to as the base body 6, is formed from a transparent material, such as glass or plastic.

[0074] The detector system 2 and the lower part of the plate 6 with the coupling-out area 5 can be Fig. 1 schematically illustrated housing G, so that it is not immediately apparent to a user that it is a camera 3. With the camera 3, an object 9 can be imaged in such a way that light beams L1, L2, L3 emanating from the object 9 enter the plate 6 via the front side 7 and are deflected by the coupling area 4 such that they strike the front side 7 at an angle such that total internal reflection occurs. Thus, the light beams L1, L2, and L3 are guided by total internal reflection at the front side 7 and rear side 8 to the coupling-out area 5, which causes a deflection in the direction of the front side 7, so that the light beams L1 - L3 exit the plate via the front side 7. The light beams L1 - L3 thus propagate in the waveguide 1 along a first direction R1 (here the y-direction) from the coupling-in to the coupling-out area 4, 5.

[0075] By means of an objective lens 10 of the detector system 2, the light beams L1 - L3 are then focused onto a detector 11 of the detector system 2, so that the desired image of the object 9 can be recorded by means of the detector 11.

[0076] The coupling area 4 is designed as a reflective volume hologram which has an angle-dependent wavelength selectivity, so that it has a high transparency for a large angle and wavelength range (as indicated by the transmitted light beam L1' in Fig. 1 is indicated; other transmitted light beams are not shown to simplify the illustration). This means that only a portion of the light beams L1 - L3 emanating from object 9 and striking the coupling region 4 are deflected in the manner described. Other light beams from object 9 propagate through the coupling region 4 and exit the plate 6 via the rear side 8. Thus, the coupling region 4 can be described as partially transparent.

[0077] In Fig. 4 The spectrally resolved, angle-dependent deflection efficiency for the reflective volume hologram of the coupling region 4 is shown schematically as a function of the angle of incidence of the corresponding light beam, with the wavelength in µm being plotted along the x-axis and the angle of incidence in ° being plotted along the y-axis. Fig. 5 The deflection efficiency is shown for the angles of incidence + 20°, 0° and - 20°, with the wavelength in nm plotted along the x-axis and the efficiency along the y-axis.

[0078] Out of Fig. 4 und 5 It can be seen that the reflective volume hologram of the coupling region 4 deflects radiation from the spectral range from 392 nm to 398 nm (λ central = 395 nm ± 3 nm) with high efficiency for an angle of incidence of -20° and thus couples it into the plane-parallel plate 6. For an angle of incidence of 0°, the high efficiency is present for the spectral range from 528 nm to 536 nm (λ central = 532 nm ± 4 nm) and for the angle of incidence of +20°, there is a high coupling efficiency for the spectral range from 600 nm to 610 nm (λ central = 605 nm ± 5 nm).

[0079] Since the waveguide 1 according to Fig. 1 bis 3 is designed such that neither the coupling region 4 nor the output region 5 has an imaging function, an infinity-infinity configuration of the waveguide 1 is present. One can also say that the waveguide 1 performs an infinity-infinity imaging. Thus, the spectral and angle-dependent deflection efficiency of the reflective volume hologram of the coupling region 4 results in each field angle (and thus each point of the imaged object 9) after coupling by means of the coupling region 4 only consisting of a small spectral range, as described with reference to Fig. 4 und 5 This results in a spectrally resolved angular distribution, which ultimately leads to an image with a spectral gradient (or color gradient) on the detector 11. The light beams L1 - L3 coupled out by means of the coupling-out region 5 are thus coupled out with an angular spectrum, which is converted into a spatial distribution on the detector 11 by means of the lens 10. The detector 11 can be, for example, a CCD detector or a CMOS detector.

[0080] Since the coupling region 4 has the reflective volume hologram, coupling via the reflective volume hologram results in dispersion within the coupled spectral range for every angle. If the output coupling region 5 has a reflective volume hologram designed in the same way as the coupling region 4, the dispersion caused by the coupling region 4 is compensated, and all spectral components are deflected back to the corresponding angle.

[0081] As an alternative to the described infinity-to-infinity configuration of the waveguide 1, the coupling region 4 and / or the output coupling region 5 can, for example, have an imaging function in the form of a lens function or concave mirror function. This allows finite-to-infinity, infinity-to-finite, or finite-to-finite imaging configurations to be realized using the waveguide 1. In the coupling region 4, this can be used, for example, to record an object 9 that is positioned so close to the waveguide 1 that it can no longer be optically assumed to be an infinitely distant object. In the output coupling region 5, implementing such a lens or concave mirror function makes it possible to immediately convert the output angular spectrum into a spatial distribution in the focal plane of this implemented lens or mirror function. In this case, the objective lens 9 can, for example, be omitted.In this case, one can say that the detector system 2 has the detector 11 as well as the lens and / or concave mirror function of the output coupling region 5. Since the objective 10 can be omitted, the detector 11 can, for example, be positioned and / or attached directly to the front side 7 of the waveguide 1, whereby a very high degree of integration, minimal volume and high robustness can be achieved. As already explained, the angular distribution spectrally resolved after the output coupling by means of the output coupling region 5 is converted into a spatial distribution on the detector 11 using the objective 10 or an imaging function integrated into the output coupling region 5. Such a detector 11 has a discretization in the form of pixels. As shown in . Fig. 6 , in which the unfolded waveguide system is shown on the detector side, each pixel PX averages over a defined angular range which is given by the pixel size PG, its distance from the optical axis AP and the focal length F AK of the objective 10 or the imaging function of the output coupling area 5.

[0082] According to the illustrations in Fig. 4 und 5 The acquisition of an angular range also involves integration over a spectral range. The spectral bandwidth is defined by the maximum (α 2 , Fig. 4 ) and the minimum recorded angle (α 1 , Fig. 4 ) which can be calculated as follows: α 1 , n = atan PG ⋅ 0,5 + n − 1 ⋅ PG f α 2 , n = atan PG ⋅ 0,5 + n ⋅ PG f , where n is the number of the respective pixel (0 → on the optical axis, n < 0 → below the optical axis, n > 0 → above the optical axis), PG is the pixel size and f is the focal length of the optical system.

[0083] Using these critical angles, the bandwidth over which each pixel integrates can be calculated, for example, based on Kogelnik's coupled-wave theory. Thus, the total spectrum detected by a pixel is composed of the spectra within the detected angular range, which leads to the Fig. 5 shown broadenings in the displayed spectra. In the limiting case where detector 11 consists of only one pixel, to which all angular ranges are transmitted, image information with all spectral components would be recorded.

[0084] While the position of the pupil (beam-limiting aperture or location where the main rays of all field angles intersect) in the infinity-infinity configuration of the waveguide 1 depends on the ratio of the width B1 (extension transverse to the first direction R1 along a second direction R2, which here corresponds to the x-direction) of the coupling region 4 ( Fig. 2 ) to the width B2 of the coupling-out region 5, the field of view of the waveguide 1 in the direction R2 is additionally dependent on the distance D of the coupling-in region 4 from the coupling-out region 5 along the propagation direction R1 or the first direction R1 in the waveguide 1.

[0085] Of course, the dimensions of the coupling area 4 and the coupling area 5 can be restricted by apertures. The optically used dimensions or widths are always used here. These are also referred to as effective widths.

[0086] In the Fig. 7A, 7B und 7C Three fundamentally different width ratios of the input and output coupling areas 4 and 5 are shown. When analyzing the pupil position, only non-vignetted field angles are considered.

[0087] Out of Fig. 7A It can be seen that for the ratio B1 / B2 > 1, the output coupling region 5 of the waveguide 1 acts as a pupil. Thus, all angles are present at every location in the output coupling region 5.

[0088] In the special case B1 / B2 = 1 ( Fig. 7B ) only the central field angle propagates unvignetted through the waveguide 1. In this case, both the input coupling region 4 and the output coupling region 5 form the pupil.

[0089] With a ratio of B1 / B2 < 1 ( Fig. 7C ) the coupling region 4 is the pupil of the waveguide 1, so that at each location in the coupling region 5 different angular ranges are present and coupled out.

[0090] Furthermore, a fundamental distinction can be made between a field of view (hereinafter also referred to as FoV) of the waveguide 1 and a field of view (hereinafter also referred to as FoV) of the detector system 2. The smaller of the two fields of view (or the two FoVs) determines the field of view of the entire system.

[0091] The horizontal FoV (in the x-direction) captured and re-coupled by waveguide 1 in the infinity-to-infinity configuration of waveguide 1 is determined by the widths B1, B2 of the input coupling region 4 and the output coupling region 5, as well as their distance D from each other (regardless of whether the pupil lies on the input coupling region 4 and / or the output coupling region 5). The FoV of detector system 2 is determined, to a first approximation, by the focal length of objective 10 (or the lens function contained in the output coupling region 5) and by the size of detector 11 in the direction of the horizontal FoV.

[0092] Ideally, the FoV of waveguide 1 and detector system 2 are identical. This results in optimal resolution across the entire FoV of waveguide 1. As long as the FoV of detector system 2 is larger than the FoV of waveguide 1, the horizontal FoV of the overall system is determined by the width of the input coupling region 4, the width of the output coupling region 5, and the distance D from input coupling region 4 to output coupling region 5. This advantageously records the entire FoV. However, the resolution is reduced. If the horizontal FoV of detector system 2 is smaller than the FoV of waveguide 1, the FoV of the overall system is limited by the FoV of the detector system. This results in the advantage of increased resolution, although only a portion of the FoV of waveguide 1 is recorded.When using the lens 10, it may happen that the distance of the detector system 2 from the waveguide 1 limits the FoV, since outer angular ranges can no longer be recorded by the lens 10, as in . Fig. 7D is indicated.

[0093] A desired adjustment of the FoV of waveguide 1 to the FoV of detector system 2 can be achieved by adjusting B1, B2, and D. A desired adjustment of the FoV of detector system 2 to the FoV of waveguide 1 can be achieved by adjusting the lens focal length and / or the size of the detector.

[0094] As already explained, the pupil position of the waveguide 1 is determined by the ratio of the width B1 of the input coupling region 4 to the width B2 of the output coupling region 5. As a result, the shape of the angular distribution at the output coupling region 5 changes. This results in advantageous properties for certain arrangements and applications.

[0095] If B1 / B2 > 1, the output coupling region 5 forms the pupil of the waveguide 1. When viewing all non-vignetted beams, all field angles are present at every location in the output coupling region 5. As a result, all field angles, i.e., the complete FoV of the waveguide 1, can be recorded with only one detector system 2 with a sufficiently large FoV and a sufficiently large entrance pupil. To achieve a large FoV of the waveguide 1, it is therefore advantageous to make the input coupling region 4 wider than the output coupling region 5. A short distance between the input coupling region 4 and the output coupling region 5 is also advantageous.

[0096] In the representation according to Fig. 7A It was assumed that a horizontally symmetrical arrangement of coupling region 4 and coupling region 5 exists, resulting in a symmetrical FoV of the waveguide 1. However, it is possible to offset the coupling region 5 laterally (in the x-direction), as in Fig. 8A is indicated. This also results in an offset of the horizontal FoV. Without a corresponding correction of the output coupling region 5, this angular distribution with the corresponding offset will also be shifted on the detector 11 due to the shifting. This could result in the FoV of the detector system 2 being exceeded and thus the overall FoV being restricted. This can be changed by implementing an additional deflection function (such as a prism, a tilted mirror, a linear grating, etc.) in the output coupling region 5. This can compensate for (or symmetrize) the offset of the output angular spectrum and adjust the output FoV to the FoV of the detector system 2 again. Alternatively, it is also possible to tilt the detector system 2 according to the angular offset.If not only one shifted coupling-out region 5 is provided, but several coupling-out regions 5 1 , 5 2 next to each other, including a corresponding compensation and an adapted detection system 2, an enlarged horizontal FoV composed of several individual FoVs can be generated (. Fig. 8B ).

[0097] With this design, the limiting case can be achieved where the width of all output regions 5 together is equal to the width of the input region 4. However, it is essential that each individual output region 5 is considered separately in relation to the input region 4. As long as the ratio of the width B1 / B2 > 1 for each individual output region 5, each output region 5 remains the pupil of the system, so that the described relationships continue to apply.

[0098] The relationships described using the example of the horizontal pupil position and the horizontal FoV can also be applied to the vertical pupil position and the vertical FoV, whereby the folding of the beam path in this direction must be taken into account. However, the following special features arise in the vertical direction, where vignetted beams are also considered.

[0099] The vertical FoV absorbed by a hypothetical infinitely extended waveguide system and forwarded to the output coupling area is given, in the infinity-to-infinity configuration of waveguide 1, by the critical angle of total internal reflection within waveguide 1 and the propagation angle of less than 90° relative to the normal of the waveguide interface or the front side 7 and the back side 8. However, for finitely extended, realistic waveguides 1, a propagation angle of less than 80° relative to the normal of the front side 7 or the back side 8 must be realized to ensure that beams L1 - L3 propagate from a large angular range to the output coupling area 5 and not past it. For a typical refractive index of 1.5, an angular range between 40° and 80° relative to the normal of the front side 7 or back side 8 propagates in waveguide 1 and is output again from the output coupling area 5.

[0100] Just like the horizontal FoV, the vertical FoV of the entire system (waveguide 1 together with detector system 2) can also be limited by the vertical FoV of detector system 2. Due to the spectrally divided angular range of the coupled and uncoupled beams, the spectral sensitivity of detector 11 can also limit the vertical FoV. If, for example, detector 11 is not particularly sensitive to long-wave and / or short-wave radiation, the effective extent of detector 11 and thus the vertical FoV of detector system 2 ( Fig. 8C ).

[0101] In the described embodiments, the image on the detector has the described color gradient, so that no full-color image can be transmitted and recorded by means of the waveguide 1.

[0102] The described reflective volume holograms for the coupling-in region 4 and the coupling-out region 5 can, for example, be produced in such a way that a photosensitive volume holographic material 12, which is integrated into the waveguide 1, is exposed to a reference wave 13 with a wavelength of 532 nm, which is incident on the front side 7 at an angle of incidence of 0°, and a signal wave 14 with the same wavelength, which is incident on the back side 8 at an angle of incidence of 60°, as in Fig. 9A is shown, wherein the reference wave 13 and the signal wave 14 originate from the same laser, so that an interference field or interference volume is created over the photosensitive volume holographic material and corresponding refractive index modifications can form there.

[0103] Photosensitive glasses, dichromate gelatins, or photopolymers can be used as photosensitive volume holographic materials. These can, for example, be applied to a PC film (polycarbonate film) and exposed there accordingly. The film can then be laminated to a substrate for the waveguide 1 to produce the waveguide 1. The film can, for example, be laminated only in the area of ​​the input coupling region 4 and the output coupling region 5. Alternatively, full-surface lamination over the entire waveguide surface is possible, with the corresponding input and output coupling functions only being exposed in the input and output coupling regions. To protect the volume holograms, it is advisable to apply another substrate to the laminated volume hologram. This creates a layer stack with the following basic structure: transparent substrate, putty or adhesive layer, volume hologram, putty or adhesive layer.Adhesive layer, transparent substrate.

[0104] Due to the spectral angle dependence already described, an incident plane wave W1 ( Fig. 9B ), which strikes the reflective volume hologram in the material at an angle of + 20°, the spectral range of 605 nm ± 5 nm is deflected towards the front side 7 in such a way that the deflected wave W1 strikes the front side 7 at an angle of β 1 of approximately 40°. For the remaining wavelengths of the plane wave W1, the reflective volume hologram of the coupling region 4 is transparent.

[0105] For a plane wave W2 that strikes the reflective volume hologram at an angle of 0°, the wavelengths from the range of 532 nm ± 4 nm are reflected so that they strike the front side 7 at an angle β 2 of approximately 60°. The remaining wavelengths of the plane wave W2 pass through the reflective volume hologram, so that the reflective volume hologram is transparent to these wavelengths of the plane wave W2.

[0106] From a plane wave W3, which strikes the reflective volume hologram at an angle of -20° in the material, the wavelengths of 395 nm ± 3 nm are reflected to the front side so that they strike the front side at an angle of β 3 of approximately 80°. The remaining wavelengths of the plane wave W3 pass through the reflective volume hologram, so that the reflective volume hologram is transparent for these wavelengths.

[0107] In order to realize the transmission of angular information (image information from infinity) through the waveguide 1 in the largest possible spectral range, the Fig. 4 The angle-dependent spectrum shown can be improved by the coupling region 4 not only having a reflective volume hologram, but having several reflective volume holograms 4 1 , 4 2 , 4 s, 4 4 and 4 5 arranged one below the other, as shown in Fig. 10 and Fig. 11A-F The volume holograms 4 1 - 4 5 differ in that they have different spectral angular selectivities, whereby different wavelengths are reflected by the volume holograms 4 1 - 4 s at the same angle of incidence. Due to this angular selectivity, radiation that is coupled, for example, from the volume hologram 4 1 into the waveguide 1 by reflection toward the front side 7 is not influenced (or only slightly influenced) by the underlying holograms 4 2 - 4 s, so that the coupled radiation can propagate (largely) unaffected to the output coupling region 5.

[0108] The volume holograms 41 - 4s can also be arranged one above the other in the z-direction, creating a layer stack on the waveguide. Furthermore, the implementation of the functions of all five holograms into a single hologram (or volume hologram), also known as multiplexing, is possible.

[0109] The different spectral angle properties can be achieved, for example, by using the same angle setting as in Fig. 9A Different wavelengths are used for the reference wave 12 and the signal wave 13. Alternatively, it is possible to use the same wavelengths for all volume holograms 41 - 4s, whereby the angle of incidence of the reference wave 12 and the signal wave 13 is varied as appropriate.

[0110] The reflective volume holograms 4 1 - 4s were recorded with the exposure configuration according to Fig. 9A at different wavelengths. The exposure wavelength for volume hologram 4 was 1,900 nm (black), for volume hologram 4,2,660 nm (red), for volume hologram 4s,532 nm (green), for volume hologram 4,400 nm (blue), and for volume hologram 4,5,370 nm (violet).

[0111] In Fig. 11B-11F The coupling of the angular range is schematically represented by the minimum angle of -20°, the maximum angle of +20°, and the central angle of incidence of 0° for each of the volume holograms 4 1 - 4s. Below 0°, each reflective volume hologram 4 1 - 4s deflects and couples in the spectral range around the central wavelength with which the respective reflective volume hologram 4 1 - 4s was exposed.

[0112] In Fig. 12 is in the same way as in Fig. 4 The simulated overall spectrum coupled into waveguide 1 by the five reflective volume holograms 4 1 - 4s is shown. Accordingly, each reflective volume hologram 4 1 - 4s contributes a different spectral range at each angle of incidence. When considering the entirety of all reflective volume holograms 4 1 - 4 5, the spectral bandwidth at the individual angles is increased, ultimately ensuring a broadband image across all angles of incidence.

[0113] Furthermore, Fig. 12 the shift of the coupled spectrum towards shorter wavelengths with increasing angle of incidence and the shift of the coupled spectrum towards longer wavelengths for decreasing angle of incidence.

[0114] Fig. 13A shows an example of the spectrum coupled with an angle of incidence of 0°. Fig. 13B shows the corresponding spectrum for the angle of incidence of + 20° and the coupled spectrum for the angle of incidence of -20° is in Fig. 13C In all representations according to Fig. 13A - 13C The wavelength in µm is shown along the x-axis and the coupling efficiency in the range from 0 (no coupling) to 1 (complete coupling) is shown along the y-axis. A comparison with the representation according to Fig. 5 shows that, compared to a single reflective volume hologram, there is a significantly improved sampling of the coupled spectrum due to the use of a higher number (five reflective volume holograms compared to one reflective volume hologram) of specifically recorded volume holograms.

[0115] In Fig. 14 The corresponding reflective volume holograms 5 1 - 5 s are shown for coupling out. The total height of the reflective volume holograms 5 1 - 5 5 is preferably chosen to be similar to the entrance pupil 14 of the detector system 2 in order to detect as much light as possible.

[0116] As with the input holograms, the volume holograms 51 - 5s can also be arranged one above the other in the z-direction for output coupling, creating a layer stack on the waveguide. Furthermore, the implementation of the functions of all five holograms into one hologram or volume hologram, also known as multiplexing, is possible.

[0117] For example, in order to couple a nearly continuous spectrum into waveguide 1 at any angle, thereby ensuring the transmission of full-color image information, forty specifically exposed reflective volume holograms can be arranged one above the other. A corresponding simulation of the angle-dependent coupling spectrum is described in Fig. 15 The exposure wavelengths for recording the individual reflective volume holograms according to the exposure configuration in Fig. 9A can be selected, for example, as follows, where the wavelength is given in nm: 358, 368, 378, 389, 400, 411, 421, 432, 443, 454, 464, 474, 487, 498, 509, 519, 532, 544, 556, 568, 583, 598, 613, 629, 645, 662, 679, 696, 715, 735, 755, 775, 795, 815, 835, 855, 875, 896, 917 and 940.

[0118] Alternatively, the reflective volume holograms can also be recorded at one wavelength and adjusted exposure angles of the reference and signal waves 12, 13.

[0119] After propagation of the radiation in waveguide 1 to the coupling-out region 5, all angles and the complete spectrum are generally present at every location in this extended coupling-out region 5 over a relatively large area. The coupling-out can then be carried out, as previously described, using appropriate reflective volume holograms. Preferably, the same 40 volume holograms are generated as those present in the coupling-in region 4.

[0120] Since the output coupling region 5 often does not need to be transparent, any other type of output coupling of the radiation propagated to the output coupling region 5 is also possible. For example, a tilted mirror surface, a prism, mirrored gratings, transmission gratings, and / or multi-order Fresnel structures can be used in transmission or reflection. At this point of the waveguide 1, the use of non-transparent optical surfaces is possible, since a non-transparent detector 11 is provided anyway.

[0121] This possibility of forming the coupling-out region 5 naturally also applies to the embodiments already described and to the embodiments still to be described.

[0122] The tilted mirror surface and the multi-order Fresnel structure in reflection or transmission advantageously exhibit high efficiency and do not introduce additional dispersion during deflection. However, they also do not provide dispersion compensation. Mirrored gratings and transmission gratings for output coupling can implement the desired dispersion correction, but they have lower efficiency. A prism exhibits high efficiency but can disadvantageously increase dispersion. The desired dispersion correction is advantageously achieved when forming reflective volume holograms, since each wavelength channel is output via a separate reflective volume hologram. However, the efficiency is relatively low because the area of ​​the output coupling region 5 must be divided by the number of individual reflective volume holograms.

[0123] In Figuren 16 bis 18B An embodiment of waveguide 1 is shown in which the horizontal FoV (i.e., the FoV in the xz plane) is enlarged. It is assumed that the FoV of detector system 2 does not limit the FoV of waveguide 1.

[0124] The coupling area 4 comprises three equally wide reflective volume holograms 4 1 , 4 2 and 4s, which are arranged one above the other (in the y-direction) and which cover different angular ranges in the xz-plane and thus different horizontal fields of view, as can be seen in particular in the view from above in Fig. 17 is represented in angular space.

[0125] As an alternative to arranging holograms 4 1 , 4 2 , and 4 3 one above the other in the y-direction, they can also be arranged one above the other in the z-direction, creating a layer stack on the waveguide. Furthermore, the implementation of the individual hologram functions of all three holograms into one hologram (or volume hologram), also called multiplexing, is possible.

[0126] For example, the second reflective volume hologram 4 2 can cover the angular range γ 0 ± γ 1 in the xz plane and thus a central field of view for γ 0 = 0. The central field of view is given, for example, by the width of the second volume hologram 4 2 , the width of the correspondingly assigned second output hologram 5 2 , and the distance between the two volume holograms 4 2 , 5 2 .

[0127] Compared to the second reflective volume hologram 4 2 , the first reflective volume hologram 4 1 has an additional one-dimensional deflection function in the horizontal direction (in the xz plane). The horizontal field of view assigned to the first volume hologram 4 1 is thus shifted in the angular range by the amount of the imposed deflection function (angular offset) and amounts to γ ​​0 - 2 • γ 1 ± γ 1 . A corresponding imposed deflection function for the third reflective volume hologram 4s ​​leads to a horizontal field of view of γ 0 + 2 • γ 1 + γ 1 . Thus, with each volume hologram 4 1 - 4s in combination with the corresponding volume hologram 5 1 - 5 3 for coupling out, a different horizontal FoV can be transmitted. The amount and direction of the applied deflection function (angle offset) can be used to specifically influence the overall FoV.For example, symmetrical or asymmetrical total FoV as well as FoV with overlapping partial FoV or gaps between the partial FoV can be created.

[0128] In order to achieve the largest possible, symmetrical and gapless horizontal FoV according to Fig. 17 To achieve this, the implemented deflection functions must be selected according to the specification in the previous section in such a way that the angular ranges are adjacent to each other and overlap as little as possible.

[0129] In the embodiment described here, all horizontal angle ranges propagate after coupling in the same horizontal channel, as in Fig. 16 This is also necessary to ensure detection with only one detection system 2. If all coupling holograms 4 1 -4s are recorded identically except for the deflection function, Fig. 18A also for superimposition in the vertical direction. After coupling out, all horizontal FoVs would be superimposed on the detector 11. To differentiate the individual horizontal angle ranges, the embodiment described here provides for coding of the horizontal angle ranges in a corresponding number of vertical angle ranges according to Fig. 18B Care was taken here to ensure that the coupling region 4 remains transparent under normal viewing over a wide angular and wavelength range. The coding of the horizontal angular ranges into vertical angular ranges can be achieved by designing the reflective volume holograms 4 1 to 4s to deflect into different vertical propagation angle ranges within the waveguide 1. For this purpose, reflective volume holograms with appropriate deflection properties can be used. Alternatively, a lamellar structure (webs) (not shown) can be attached in front of each reflective volume hologram 4 1 - 4s to restrict the respective vertical FoV. However, this significantly limits the transparency in the coupling region 4.

[0130] With this differentiation of the different vertical propagation angle ranges, the radiation from each coupling volume hologram 4 1 - 4s, and thus also each horizontal FoV, propagates into a different vertical FoV. After coupling out, the different vertical FoVs are then transferred to detector 11 in laterally superimposed, adjacent spatial distributions. This allows an enlarged horizontal FoV to be recorded, with the vertical FoV being reduced by the magnification factor of the horizontal FoV.

[0131] In an alternative variant, the detector-side spectral and angle-dependent separation of the horizontal FoV encoded in the vertical FoV can be used, as explained in more detail below.

[0132] If each horizontal FoV is coupled with an identically designed volume hologram except for the deflection function (angle offset), each horizontal FoV propagates in the same vertical angular range and spectral range through the waveguide 1. For each horizontal FoV, the approximate value is, for example, Fig. 4 The angle-dependent spectrum shown is then no longer possible. Separation on the detector side is then no longer possible.

[0133] Alternatively, however, each horizontal FoV can be coupled with a special volume hologram in different directions in the waveguide 1, with each volume hologram 4 1 -4s being recorded in a different configuration (exposure angle and / or wavelength).

[0134] In Fig. 19A, 19B und 19C are the angle-of-incidence and spectral-dependent efficiencies of the laterally offset coupling volume holograms 4 1 , 4 2 and 4 3 ( Fig. 18B ). The following discussion assumes that the vertically coupled angular range is limited to ± 20° due to total internal reflection in the waveguide. Furthermore, detector 11 only has a spectral sensitivity of 400 nm to 700 nm. This procedure is, of course, also transferable to other vertical angular ranges and detector sensitivities.

[0135] According to the presentation in Fig. 19B The first volume hologram 41 couples an angle of incidence range between 6.67° and 20° in a spectral range between 400 nm and 440 nm into the waveguide 1. In contrast to the first volume hologram 41, the second volume hologram 42 couples radiation from the entire angle of incidence range across a spectrum from 400 nm to 650 nm into the waveguide 1. The third volume hologram 4s ​​will couple the angle of incidence range between -6.67° and -20° in a spectral range from 565 nm to 700 nm into the waveguide 1. Thus, each horizontal field of view is coupled into the waveguide 1 by a special volume hologram 41-4s with different properties. These properties are used after coupling to separate the horizontal FoV.

[0136] Holograms 4 1 , 4 2 , and 4 3 can also be arranged one above the other in the z-direction, creating a layer stack on the waveguide. Furthermore, the implementation of the individual hologram functions of all three holograms into one hologram (or volume hologram), also called multiplexing, is possible.

[0137] In the output region 5, it can be expected that the spectral angular spectrum coupled in by all coupling volume holograms 4 1 - 4 3 is present at every location. In the output region 5, volume holograms 5 1 , 5 2 , 5 3 are arranged laterally offset one above the other with a behavior identical to the vertical coupling. Each of these holograms 5 1 - 5s then ensures the coupling out of the radiation coupled in by the corresponding coupling volume hologram 4 1 - 4s with the corresponding Fig. 19A - 19C spectral angular distribution shown.

[0138] As in the coupling region, the holograms 5 1 , 5 2 , 5 s can alternatively be arranged one above the other in the z-direction, creating a layer stack on the waveguide. Furthermore, the implementation of the individual hologram functions of all three holograms into one hologram (or volume hologram), also called multiplexing, is possible.

[0139] After decoupling, the total field is separated so that the different horizontal FoVs can be detected individually. For this purpose, the detector surface of detector 11 is first divided vertically. Each surface portion corresponds to a vertical angular range. The number of surface portions (vertical angular ranges) is identical to the number of different horizontal FoVs. Normally, the detector surface (total vertical angular range) is divided into equal-sized surface portions (a subdivision into different sized surface portions is also possible). Accordingly Fig. 19C However, due to the typical behavior in reflection volume holograms, spectral superposition occurs within the individual angular ranges, so that ultimately different horizontal FoVs would be superimposed with the same vertical FoVs. To avoid this, spectral filters can be provided for each sub-area of ​​the detector 11, i.e., for each vertical sub-angular range, which suppress unintended spectral components for a corresponding angular range. As a result, the different horizontal FoVs can be clearly assigned to different areas on the detector (i.e., vertical angular ranges / FoV). As a result, a clear assignment of the different horizontal FoVs to different vertical FoVs is achieved accordingly. Fig. 18b realized.

[0140] As an alternative to the use of spectral filters, it is also possible to use special output volume holograms, which only realize output in the required spectral range.

[0141] After applying the spectral filters or using the spectrally adapted output volume holograms, the result is Fig. 20 displayed angle-dependent spectrum. This eliminates overlaps between different horizontal FoVs, allowing a clear assignment of the horizontal FoV to the corresponding vertical FoV.

[0142] This increases the detectable horizontal FoV. However, it also reduces the vertical FoV.

[0143] The advantage of the described spectral coding of the horizontal FoV in the vertical FoV compared to the angular coding of the horizontal FoV in the vertical FoV is primarily the higher transparency in a large angular and spectral range with normal viewing through the coupling area 4.

[0144] A disadvantage of spectral coding is that each horizontal FoV records a different spectral band, which can lead to information loss if, for example, no or only a small amount of radiation is present in a specific horizontal FoV in the corresponding spectral range. This deficit can be compensated for by installing multiple output coupling areas with correspondingly spectrally shifted input spectra for the different horizontal FoVs. However, this also requires a corresponding number of detector systems.

[0145] The following aspects must be considered in the general design of the overall waveguide 1 system and the design of the input and output volume holograms in particular: To realize n different horizontal FoVs, n different input and output volume holograms as well as n angular ranges (detector ranges) are required, including corresponding band or edge filter functions. N horizontal angular ranges are converted into n vertical angular ranges.

[0146] The individual efficiency curves of the volume holograms must not exhibit any spectral overlap within the same angular range, as otherwise spectral separation of the vertical FoV and thus also the horizontal FoV would no longer be possible. Despite spectral filtering, radiation components from different horizontal FoVs would overlap.

[0147] In order to absorb as much radiation power as possible, each volume hologram must be designed to cover the largest possible spectral range within the respective angular range. However, the spectral sensitivity of the detector must also be taken into account. When comparing the angle- and wavelength-dependent efficiency curves in Fig. 19B und 19C It becomes clear that in the angular range between +6.67° and +20°, a radiation bandwidth of only 40 nm is used. A correspondingly optimized design of the volume hologram would allow an increase in this bandwidth and thus the coupling of a potentially higher radiation output. In contrast to the angular range between +6.67° and +20°, a spectral range of 135 nm is coupled in the angular range between -6.67° and -20°.

[0148] The subdivision of the horizontal FoV is linked to the spectral properties of the volume hologram. Typically, all vertical FoVs are the same size. However, depending on the application, different vertical FoV sizes can be realized for the different horizontal FoVs. This requires an appropriate design of the volume holograms in combination with filtering in front of the individual detector areas.

[0149] In Fig. 21 An embodiment of the waveguide 1 is shown in which the coupling region 4 is wider than the coupling region 5 and the coupling region 4 is realized by a reflective volume hologram. The coupling region 5 can also have a reflective volume hologram. The FoV is determined by the size of these areas and their distance from each other. In the case of the Fig. 22 In the embodiment described, it is assumed that the FoV of the detector system 2 does not limit the FoV of the waveguide 11.

[0150] The approach according to Fig. 22 To increase the detection efficiency, the coupling area 4 is divided vertically (along the second direction) into three sub-coupling surfaces 4 1 , 4 2 and 4 3 . While the central coupling area (or the central reflective volume hologram 4 1 ) only contains a function for deflecting the radiation in the first direction (only in the y-direction without x-component) to the coupling-out area 5, a horizontal deflection function (or an x-component of the deflection) along the second direction (towards the central volume hologram 4 1 ) is additionally integrated into the right sub-coupling area 4 2 , as in Fig. 22 is indicated schematically. A corresponding horizontal deflection function along the second direction (toward the central volume hologram 41) is also integrated into the left sub-coupling surface 4s.

[0151] Without this deflection function, the FoV for the input surface 42 and the output region 5 would be determined by the sizes of the surfaces, their distance, and the decentering (along the second direction) of the input surface 42 relative to the output region 5 (the same would apply to the combination of the left input surface 4s and the output region). This FoV has an angular offset relative to the central FoV (given by the central input surface 41 and the output surface 5). The total results in an enlarged FoV, which is determined by the total width of the two input surfaces.

[0152] By integrating the described deflection function into the two lateral coupling surfaces 4 2 and 4 3 , the described angular offset can be compensated. The decentered coupling volume hologram 4 2 , 4s then, in combination with the coupling-out volume hologram 5, covers the same FoV as the central coupling-out volume hologram 4 1 . However, the radiation emanating from the decentered coupling volume hologram 4 2 , 4s then propagates horizontally in the waveguide with a horizontal angular offset and is coupled out of the waveguide 1 with this angular offset. Thus, the same FoV is present next to each other after coupling-out. Using a detector system 2 with a sufficiently large FoV, these adjacent identical FoVs can be recorded. This increases the detected radiation power for the horizontal FoV, but not the power density relevant for the signal-to-noise ratio.

[0153] In order to achieve this, the coupling-out surface 5 is designed with the aid of volume holograms in such a way that it couples out the radiation coupled in by the central coupling-in volume hologram 4 1 and the radiation coupled in by the decentered coupling-in volume holograms 4 2 , 4s into the same angular range.

[0154] This is achieved by having the output coupling region 5 have different exposed output coupling functions. Each output coupling function is only effective for the radiation of the corresponding input coupling volume hologram 4 1 - 4 3 (angle selectivity of the volume hologram), so that the radiation propagating from different directions to the output coupling region 5 is ultimately output by the corresponding output coupling function into the identical angular range. The strength of the angular selectivity can be adjusted via the thickness and refractive index modulation of the volume holographic material and the exposure configuration.

[0155] One of these functions corresponds to the original output coupling function and only ensures the vertical output of the radiation. All other implemented functions have a special, adapted angular selectivity, so that they are only effective for a horizontal angular range around the respective horizontal angular offset, which propagates from the corresponding decentered input coupling surface 4 2 , 4s in the direction of the output coupling surface 5. In addition to the vertical output coupling function, this output coupling function includes compensation for the horizontal angular offset, so that the FoV generated by the decentered input coupling surfaces 4 2 , 4s is superimposed on the FoV generated by the centered input coupling surface 4 1 . As a result, the power density within the FoV is increased and the signal-to-noise ratio is improved.

[0156] The process described here can also be referred to as pupil reduction in the optical sense (cf. pupil replication or pupil expansion in imaging = reversed light path). In this way, power can be collected over a large area in the input region 4 and output over a small area in the output region 5.

[0157] This makes it possible to create a coupling area 4 with very low efficiency and thus high transmission. This enables the acquisition of high-intensity image information via a coupling surface 4 with the highest possible transmission.

[0158] On the other hand, the coupling region can also be designed with a transmission that is just acceptable, i.e., with a high coupling efficiency, in order to concentrate as much radiant power as possible into a very small coupling region. A very small solar cell could then be mounted at the coupling region to convert the radiant energy into electrical energy. It is also possible for the coupling to occur on a detector array.

[0159] The implementation of different output functions is possible with sufficiently thick volume holographic material with a sufficiently high refractive index modification. This implementation of different functions in a single holographic surface is also referred to as function multiplexing. Alternatively, the individual output functions can also be imprinted on several volume holographic foils stacked on top of each other.

[0160] It should be noted that, just as in the vertical direction, this also results in angle-dependent spectral coupling in the horizontal direction, thus also resulting in an angle-dependent spectral gradient in the horizontal direction. However, since spectral information is lost anyway due to the spectral distribution in the vertical direction, this color gradient does not represent a significant disadvantage of the method.

[0161] As from Fig. 22 As can be seen, the increase in efficiency when vertically dividing the coupling area 4 while maintaining the same width of the coupling area is associated with a reduction in the horizontal FoV. This disadvantage can be overcome by combining it with the variant according to Fig. 16 bis 18 be compensated, which however results in a reduction of the vertical FoV.

[0162] If, however, a horizontal subdivision of the coupling area of Fig. 21 according to Fig. 16 performed, the original FoV can be determined from only one coupling volume hologram ( Fig. 21 ). However, if the coupling volume hologram area remains constant, no overall increase in the coupled radiation power is achieved. However, if the area of ​​each coupling volume hologram is increased, the efficiency of the system can be improved using the procedure described above.

[0163] In principle, the coupling volume holograms can be freely distributed on the waveguide 1. Then, the effect on the respective FoV with respect to the coupling volume hologram as well as a correspondingly adjusted correction of outcoupled angular ranges must be taken into account.

[0164] In Fig. 23 An embodiment is shown in which a relief grating is formed in both the input coupling region 4 and the output coupling region 5. The rules for determining the grating period are essentially the same as for a volume hologram. A diffraction angle is required for which total internal reflection in the waveguide 1 is guaranteed. Furthermore, symmetrical gratings are advantageously used for input and output coupling. Furthermore, if desired, an imaging function can optionally be applied to the input coupling grating and / or the output coupling grating. This allows even objects that are, for example, only 50 cm away from the waveguide 1 to be sharply imaged.

[0165] The advantage of designing the input and output gratings as relief structures compared to volume holograms is the lower angle and wavelength selectivity. As already described, when using volume holograms, an observation angle is linked to a limited wavelength range. Without a corresponding design, Fig. 11 Gaps in the illuminating spectrum lead to blind vertical observation angles. The higher wavelength and angular acceptance of relief structures can prevent these failures.

[0166] The coupling grating 20 can be applied, for example, by means of an epoxy resin or a UV-curing polymer to the right surface 21 of the left plate 22 with the thickness d 1 in Fig. 23 Typical polymers have refractive indices n of approximately 1.5.

[0167] The coupling grating 20 is then coated with a thin, high-index dielectric layer 23. Typical refractive indices for this are n > 2.0. Values ​​between 10 and 100 nm, for example, can be used as the thickness for the layer 23. It is particularly advantageous to coat not only the coupling grating 20, but the entire left plate 22 with the thin, high-index layer 23 in order to achieve a uniform transmission impression across the entire surface.

[0168] Subsequently, the second plate 24 (with a thickness d 2 ) is bonded to the coupling grating 20 and the associated plate 22 with a thickness d 1 using an epoxy resin or a UV-curing polymer. The coupling relief grating 20 is thus buried in the substrate formed by the two plates 22 and 24 and, due to its thin, highly refractive layer, acts as a reflection grating 20 with diffraction efficiencies between 5% and 20%.

[0169] For the output grating 25, a grating with the same line number (grating period) is used, which, however, is molded onto the outer surface 7 of the left plate 22 or onto the outer surface 8 of the second plate 24. In the Fig. 23 In the embodiment shown, the output coupling grating 25 is molded onto the front side 7. After molding, this grating 25 is vapor-deposited with aluminum to achieve high output coupling efficiency. Efficiency values ​​of around 50% are achievable over a broad wavelength and angle spectrum.

[0170] The waveguide 1 with the input grating 20 and the output grating 25 has two apertures, since the edges of the input grating 20 and the edges of the output grating 25 each act as apertures that cut off the beam path. In the illustration according to Fig. 23 Only one beam of rays for exactly one wavelength is shown. Other wavelengths emanating from the same object point are redirected by the coupling grating 20 to different angles in waveguide 1. This relationship between wavelength and propagation angle in waveguide 1 is continuous, although not linear.

[0171] Thus, for long waveguides 1 with many (e.g., 10, 20, etc.) reflections, it is possible that the surface of the input grating 20 (viewed in vertical section) falls exactly on the output grating 25. In this case, a large amount of light is transmitted. However, it can also happen that the aperture of the input grating 20 is imaged just below and once above the output grating 25, so that no light is output in the output grating 25.

[0172] The transmitted spectrum is thus divided into efficient and inefficient areas, which alternate almost periodically. Such a purely geometrically determined transmission spectrum is Fig. 24 , with the wavelength in nm plotted along the x-axis and the transmission efficiency between 0 (no transmission of the light falling on the input grating 20) and 1 (all of the light falling on the input grating 20 is coupled out via the output grating 25, neglecting the grating diffraction efficiency) plotted along the y-axis. This transmission efficiency is shown for an angle of incidence of -15°, which covers the wavelength range from 400 to 530 nm (dashed line), for an angle of incidence of 0°, which covers a wavelength range from 440 to 645 nm (solid line), and for an angle of incidence of +15°, which covers a wavelength range from 555 nm to 690 nm (dotted line).The spectral limitations result, on the one hand, from the condition for total internal reflection and, on the other hand, from the deflection angle after the input coupling at which the output grating is just hit (without total internal reflection at the output surfaces). This shows that the transmitted spectral interval shifts with the angle of incidence. The transmitted spectral interval increases with increasing refractive index of the waveguide.

[0173] In Fig. 25 The vignetting caused by the entrance pupil EP of the detector system 2 is shown schematically. Thus, a part of the coupled-out beams cannot reach the detector 11, which leads to a geometrically determined transmission spectrum, as shown in Fig. 26 is shown schematically. The representation in Fig. 26 corresponds to the representation in Fig. 24 As expected, this vignetting results in poorer transmission spectra for the angles of incidence -15° and +15°.

[0174] The coupling grating 20 can be designed as a sawtooth grating, ie the profile shape of each grating period follows at least approximately a sawtooth shape. Fig. 27 shows a simulated cross-section through one grating period of the buried coupling grating, assuming a slight profile rounding. The lateral extent from 0 to 430 nm is plotted along the x-axis, and the profile section in the range from 0 to 300 nm is plotted along the y-axis, resulting in a layer thickness of approximately 60 nm with a blaze depth of approximately 120 nm. Using such a structure, it is possible to couple a wide wavelength range into the waveguide 1 with approximately 10 to 15% efficiency. The resulting diffraction efficiency (reflection coefficient) is Fig. 28 for the wavelength range from 400 to 650 nm (plotted along the x-axis). Curves RE0 and RM0 show the reflectance for zero-order reflection for the s-polarized field (RE) and the p-polarized field (RM). Curves RM1 and RE1 show the reflectance for the minus first diffraction order for the s-polarized field (RE) and the p-polarized field (RM).

[0175] For the coupling-out grating 25, a profile shape similar to that shown in Fig. 27 However, instead of the high-index dielectric, a metal coating is used.

[0176] In Fig. 29 und 30 An embodiment is shown in which the waveguide 1 is integrated into a display 30. The display 30 can be a display of a mobile consumer device (such as a mobile phone or a laptop). It can also be a display of a stationary computer.

[0177] As in the depictions of Fig. 29 und 30 As can be seen, the coupling area 4 with the reflective volume hologram is formed on the back 8, which causes a beam deflection such that the deflected rays are guided within the display by, for example, internal total reflection until they hit the coupling-out area 5 with the coupling-out volume hologram, which causes a deflection in the direction of the camera sensor 11. The image recorded in this way is essentially a frontal view of the user B, who is looking at the coupling area 4. The image therefore corresponds to a recording with a camera sensor that is positioned in the area of ​​the coupling area 4. One can therefore use the solution according to Fig. 29 und 30 a transparent image sensor that is integrated into the display without impairing the display's display function. It can be used to capture images or image sequences at the location of the display 30, thus creating a frontal view of the scene to be imaged.

[0178] This feature can be used advantageously for applications such as video telephony or taking self-portraits (so-called selfies), as the line of sight of user B towards the display coincides with the center of the image captured by the camera. This allows both conversation partners to maintain eye contact during video telephony, for example, something that was previously impossible because the corresponding cameras were always installed at the edge of the display. This eye contact leads to a more natural and immersive conversation experience. When taking self-portraits, for example, the user can follow the live preview of the image being captured without having to look away from the camera and towards the display.

[0179] In addition to the deflecting function, the output grating 5, for example, can have an imaging function, so that no additional optics are required in front of the camera sensor 11. This allows the degree of integration of the camera into the display 30 to be maximized.

[0180] Due to the pronounced wavelength and angle selectivity of the diffraction efficiency typical of volume holograms and the ability to tailor the diffraction efficiency, the part of the display 30 covered by the coupling grating appears largely transparent, and the content shown on the display remains visible to the viewer. To achieve this, the efficiency of the coupling grating 4 must, on the one hand, be large enough to enable the camera sensor 11 to capture the image. On the other hand, the efficiency of the coupling grating must be low enough to maintain transparency and prevent any disturbing effects for the viewer. The resulting transparency of the applied volume hologram in the coupling area therefore also depends on the light sensitivity of the camera sensor 11 used.

[0181] In the simplest construction of the coupling area 4 and the coupling area 5 according to the embodiment of Fig. 1 bis 3 For each angle, a different wavelength range is transmitted to the detector 11 or camera sensor 11, creating an image with a vertical color gradient. This image can then be converted into a monochrome image. For example, to obtain a natural multicolored image, the monochrome image can be colorized in real time using image information captured by another front camera. In this way, a natural image can be provided via the volume holographically implemented camera function with the aforementioned advantage of the frontal view.

[0182] Alternatively, the color functionality of the volume holographically implemented camera function according to the embodiment of Fig. 10 bis 15 This would eliminate the need for an additional front camera and post-coloring.

[0183] In the Fig. 29 und 30 In the embodiment shown, it was assumed that the output coupling region 5 and the camera sensor 11 are located below a non-displaying region 31 of the display 30, since otherwise the light emitted by the display would also fall on the camera sensor 11. This would interfere with the recording of the image.

[0184] However, if a display 30 is used which is transparent when inactive, the camera sensor can also be arranged below the area actually used by the display, as in the embodiment according to Fig. 31 und 32 is shown.

[0185] When an image is captured, the relevant area of ​​the display 30 is dimmed, so that only the light coming from the output region 5 falls onto the camera sensor 11. This allows the display 30 to be used entirely for display purposes when the camera function is not activated. If the camera function is activated, only a portion of the display 30 is dimmed. The display area is thus only restricted when necessary, and only near the edge.

Claims

1. A screen with a transparent base body (6) which has a front side (7) and a rear side (8), and an image sensor (11), wherein the base body (6) comprises an input coupling region (4) and an output coupling region (5) spaced apart therefrom in a first direction (R1), wherein the input coupling region (4) comprises a diffractive structure which deflects only a portion of radiation coming from an object to be detected and impinging on the front side (7), such that the deflected portion propagates as coupled-in radiation in the base body (6) as far as the output coupling region (5) by means of reflections and impinges on the output coupling region (5), wherein the output coupling region (5) deflects at least one portion of the coupled-in radiation impinging on it, such that the deflected portion emerges from the base body (6) via the front side (7) or the rear side (8) in order to impinge on the image sensor (11), wherein the screen comprises a light-emitting layer arranged on the rear side (8) of the base body (6), said light-emitting layer generating a real image.

2. The screen as claimed in claim 1, wherein the output coupling region (5) is arranged closer to the edge of the base body (6) than the input coupling region (4) along the first direction.

3. The screen as claimed in claim 1 or 2, wherein the input coupling region (4) is arranged at the rear side (8).

4. The screen as claimed in any of the preceding claims, wherein the input coupling region is arranged between the base body (6) and the light-emitting layer.

5. The screen as claimed in any of the preceding claims, wherein the image sensor (11) is arranged at the rear side of the base body (6) in a region which serves as a displaying region of the screen and which is blanked during the recording by means of the image sensor (11).

6. The screen as claimed in any of the preceding claims, wherein the screen comprises an additional camera, which records the object, wherein the recording effected by the camera is used for subsequently coloring a recording of the object by means of the image sensor (11).

7. The screen as claimed in any of the preceding claims, wherein the extent of the input coupling region (4) in a second direction (R2) transverse to the first direction (R1) is greater than the extent of the output coupling region (5) in the second direction (R2).

8. The screen as claimed in any of the preceding claims, wherein the diffractive structure of the input coupling region (4) is embodied as a reflective volume hologram, a transmissive volume hologram, a reflective relief grating or a transmissive relief grating.

9. The screen as claimed in any of the preceding claims, wherein the output coupling region (5) comprises a reflective volume hologram, a transmissive volume hologram, a reflective relief grating, a transmissive relief grating, a mirror surface or a prism.

10. The screen as claimed in any of the preceding claims, wherein the output coupling region (5) comprises a reflective or transmissive Fresnel structure.

11. The screen as claimed in any of the preceding claims, wherein the input coupling region (4) and / or the output coupling region (5) also comprises an imaging optical function in addition to the beam deflection.

12. The screen as claimed in any of the preceding claims, in which the image sensor (11) is connected to the front or rear side (7, 8) of the base body (6).

13. The screen as claimed in claim 12, wherein no separate imaging optical element is arranged between the image sensor (11) and the front and / or rear side (7, 8).