Wavefront manipulator with total reflection and reflection hologram

Abstract

The invention relates to a wavefront manipulator (1) which comprises a holographic assembly (2) and an optical element (3). The optical element (3) comprises at least one surface (5), which is totally reflective for an ascertained range of incidence angles, for emitting light waves onto the holographic assembly (2), and the holographic assembly (2) comprises at least one reflection hologram for reflecting light waves emtted onto the holographic assembly (2) by means of the optical element (3). The optical element (3) comprises a coupling device (7) for coupling light waves into the wavefront manipulator (1), said coupling device comprising at least one prism.

Description

[0001] Wavefront manipulator with total internal reflection and reflection hologram

[0002] The present invention relates to a wavefront manipulator, for example, for placement in the beam path of a head-up display (HUD) between a projection lens and a projection surface, in particular a curved projection surface. The invention further relates to an optical arrangement and a head-up display.

[0003] Head-up displays are now used in a wide variety of applications, including vehicle viewing windows, such as car windshields, windscreens, or aircraft viewing windows. These viewing windows, and especially windshields, typically have a curved surface, which is used as a projection surface for head-up displays.

[0004] A head-up display typically comprises an imaging unit (PGU) or a projector, a projection surface, an eyebox, and an image plane of the virtual image. An image is generated using the imaging unit or projector. The image is projected onto the projection surface and from there into the eyebox. The eyebox is a plane or spatial area in which the projected image is perceivable by a viewer as a virtual image. The image plane of the virtual image, i.e., the plane on or in which the virtual image is generated, is located on or behind the projection surface.The curvature of the projection surface and compact arrangements in a small installation space, with potentially significant tilts of individual components relative to one another and correspondingly complex folded beam paths, lead to imaging errors or aberrations. A windshield can generally be described as an optical freeform surface. If a head-up display is used in conjunction with a curved windshield or a curved viewing window, it is desirable to correct imaging errors caused by the curvature, the aforementioned imaging errors that may occur due to installation space constraints, and any imaging errors in the optical beam path caused by the imaging unit. The imaging errors or aberrations that can occur in this case include distortion, defocus, tilt, astigmatism, curvature of the image plane, spherical aberrations, higher astigmatism, and coma.In the context of head-up displays, especially for automotive applications, the largest possible field of view, the largest possible eyebox, and a uniform, bright, and multicolored image, preferably multicolored at every pixel, are also desirable. Similar requirements must also be met in the context of other optical applications and implemented using suitable wavefront manipulators.

[0005] Documents DE 10 2007 022 247 A1, DE 10 2015 101 687 A1, DE 10 2017 212 451 A1, and DE 10 2017 222 621 A1 describe holographic imaging optics for head-up displays, particularly in connection with windshields. In connection with head-up displays and other optical applications, in addition to high imaging quality, it is often desirable for the components used to be permanently installed or arranged in a fixed manner relative to one another, particularly to reduce costs and maintain system stability.

[0006] Documents JP 2020-34602 A and JP 2008-158203 A disclose head-up displays for motor vehicles. Document US 2006 / 0132914 A1 describes the display of an image against a background, particularly in the context of a head-mounted display.

[0007] Against this background, the object of the present invention is to provide an advantageous wavefront manipulator. Further objects include providing an advantageous optical arrangement and an advantageous head-up display.

[0008] The first object is achieved by a wavefront manipulator according to claim 1. The further objects are achieved by an optical arrangement according to claim 17 and by a head-up display according to claim 19. The dependent claims contain further advantageous embodiments of the invention.

[0009] The wavefront manipulator according to the invention comprises a holographic arrangement and an optical element, for example, a waveguide. The optical element comprises at least one totally reflecting surface for a defined angle of incidence range for radiating light waves onto the holographic arrangement. The totally reflecting surface can be a surface. The holographic arrangement comprises at least one reflection hologram for reflecting light waves radiated onto the holographic arrangement by means of the optical element. The optical element comprises a coupling device for coupling light waves into the wavefront manipulator, in particular in the direction of the totally reflecting surface. The coupling device comprises at least one prism.

[0010] The prism is preferably designed as a separate component from the optical element, in particular the waveguide. The prism can be arranged directly on the optical element and / or directly on the holographic arrangement. Advantageously, in this variant, the interface between the prism and the optical element and / or the holographic arrangement does not exhibit a jump in the refractive index. At the very least, a change in the refractive index at the interface should be as small as possible, for example, less than 0.1, preferably less than 0.05.

[0011] The optical element, in particular the waveguide, can have a top side and a bottom side, which are designed for the total internal reflection of light waves between them. The top side and the bottom side can be connected to one another by side surfaces. In the context of the present invention, the prism is preferably arranged on the top side or the bottom side, in other words not on one of the side surfaces. In the case of a one-piece design of optical element, in particular waveguide, and prism, in other words a design in which the prism is an integral part of the optical element, in particular the waveguide, the prism can be arranged or designed such that it protrudes from the respective side on the top side or the bottom side, in other words it protrudes geometrically on the top side or the bottom side.Due to the described configurations, an enlarged coupling area and a larger angular range for the coupling can be realized compared to a coupling on one of the side surfaces.

[0012] The wavefront manipulator according to the invention has the advantage that it enables the use of reflection holograms with a reduced number of holograms required. Typically, transmitting holographic components using reflection holograms are realized by two consecutively arranged reflection holograms (so-called z-holograms), with each hologram being efficient for a specific wavelength. For a multi-color application, for example, using wavelengths from three colors or wavelengths of a fixed color space (e.g., RGB applications), six holograms are required. Integrating the holograms into a hologram stack is generally very complex. Due to the very complex stack structure and the use of a large number of holograms, the transmittance is significantly reduced, among other things due to material absorption.In addition, the holograms can filter each other. To overcome these disadvantages, the wavefront manipulator according to the invention enables a reduction in the number of holograms without compromising the functionality of the wavefront manipulator. Rather, the reduced filter effects result in improved functionality.

[0013] The totally reflecting surface of the optical element enables beam deflection, which is conventionally achieved by a reflection hologram. By arranging the optical element in the beam path such that light totally reflected by the optical element is irradiated into the holographic arrangement for reflection by the latter, the invention makes it possible to eliminate half the number of holograms otherwise required by utilizing total reflection. This significantly reduces costs. Furthermore, the smaller number of components reduces potential filter effects and aberrations. Preferably, at least one of the holograms, in particular a majority of the holograms or all of the holograms, is designed for aberration correction. For this purpose, at least one of the holograms can be recorded or written with freeform construction wavefronts, i.e., with light waves whose wavefronts form freeform surfaces.

[0014] In the wavefront manipulator according to the invention, the holographic arrangement is designed to efficiently diffract a wave that is totally reflected before it hits the hologram. Preferably, at least one hologram is designed to be efficient when reconstructed with the exposure wavelength for at least one angle that is greater than the critical angle of total reflection of the totally reflecting surface of the optical element.

[0015] Advantageously, the holographic arrangement is arranged downstream of the optical element in the beam path. Alternatively, the holographic arrangement can be arranged in the beam path such that it transmits light waves in the beam path immediately behind the coupling device, i.e., before a first total internal reflection and / or before a second total internal reflection within the optical element, and reflects them in the beam path behind the totally reflecting surface. In other words, the holographic arrangement can be arranged geometrically and in the beam path between the coupling device and the totally reflecting surface, but as an element that merely transmits light waves in this beam direction without exhibiting any diffraction efficiency.Optionally, after the first total internal reflection, light waves can be transmitted again through the holographic arrangement, preferably toward a prism surface designed, for example, for aberration correction, in particular a reflective surface, and only reflected from the totally reflecting surface after a second total internal reflection. The prism surface designed for aberration correction can be designed as a freeform surface and / or comprise at least one hologram. This configuration offers the advantages of reduced installation space and improved correction of aberrations.

[0016] Preferably, the wavefront manipulator is designed as a transmission component, in particular with refractive power. This provides the advantages of a reflection hologram with a half-reduction in the number of holograms. Previously, a transmission component with reflection holograms for one wavelength required two holograms.

[0017] The coupling device can comprise a plurality of prisms. The prisms can be arranged in a row or as a grating on a coupling surface. They can be designed, for example, as a prism array, in particular as a microprism array. The dimensions of the individual prisms can be in the micrometer range. The lateral or perpendicular extent of the individual prisms can be between 5 micrometers and 1 millimeter, for example between 5 pm and 50 pm, between 50 pm and 200 pm, between 200 pm and 500 pm, or between 500 pm and 1 mm. The use of a plurality of prisms has the advantage that the individual prisms can be designed to be wavelength-specific and / or angle-of-incidence-specific and can thus contribute to beam expansion on the one hand and aberration correction on the other. In addition, the surfaces and / or elements of the prism can, for example, be designed for aberration correction, in particular in transmission and / or reflection.For this purpose, at least one surface arranged in the beam path and / or an element of the prism can be designed as a freeform surface. Furthermore, several surfaces and / or elements of the prism can interact to correct aberrations. Advantageously, the prism and the holographic arrangement can be designed to interact to correct aberrations. For example, the coupling surface and / or a reflective element of the prism and / or the holographic arrangement can be designed to interact to correct aberrations.

[0018] The optical element can comprise a first side, e.g. in the form of a top side, and a second side opposite the first side, e.g. in the form of a bottom side. The coupling device and the holographic arrangement can be arranged on the first side. The totally reflecting surface can be arranged on the second side. This makes it possible to realize a very compact arrangement which only requires total reflection within the optical element for beam deflection in the direction of the holographic arrangement. The surfaces of the first side (top side) and the second side (bottom side) do not run parallel to one another in the region of the coupling device due to the at least one prism.

[0019] In the case of a transmission element configuration, the coupling device and a coupling region formed thereby, as well as a coupling-out region designed to couple light waves out of the wavefront manipulator, are arranged on opposite sides of the wavefront manipulator. The coupling-in and coupling-out regions can also be arranged on the same side. Preferably, the totally reflecting surface includes a coupling-out region. The totally reflecting surface thus at least partially forms a coupling-out surface for light waves diffracted by the holographic arrangement.

[0020] In a further variant, the wavefront manipulator can have a coupling-out region which at least partially encompasses the totally reflecting surface, wherein the coupling device and the coupling-out region overlap at least partially in a direction perpendicular to a surface normal of the totally reflecting surface.

[0021] The optical element can comprise glass or plastic. It can comprise at least one of the following materials: polycarbonate (PC), polymethyl methacrylate (PMMA), cyclic olefin polymer (COP), cycloolefin copolymers (COC), triacetate (TAC), a transparent adhesive layer (OCA - Optically Clear Adhesive), borosilicate glass, one or more of the glass types B270, N-BK7, N-SF2, P-SF68, P-SK57Q1, P-SK58A and P-BK7 or comparable glasses. These materials are particularly well suited for a transparent optical waveguide, which has good optical properties such as high transparency and homogeneity, for example with regard to the refractive index, and is inexpensive and easy to produce. Some of the listed materials have a high refractive index compared to the environment, for example compared to air under standard conditions.

[0022] The optical element can be designed, particularly geometrically, such that light waves between the coupling device and the holographic arrangement undergo or pass through a specified number n of total resections within the optical element. Preferably, n is less than 5 (n<5), ideally equal to 1 (n=1).

[0023] In an advantageous variant, the holographic arrangement comprises at least one reflection hologram, which is designed to reflect a plurality of wavelengths or frequencies, i.e., in particular, light of a defined color space or for multicolored images, and is diffraction-efficient for these (multiplex hologram). Alternatively, the holographic arrangement can comprise a plurality of reflection holograms, each of which is designed, i.e., efficient, for at least one wavelength or frequency, in particular, a defined wavelength or frequency range, of light of one color of a color space. The color space can be, for example, an RGB color space (RGB - Red Green Blue) or a CMY color space (CMY - Cyan Magenta Yellow).

[0024] The individual holograms can be arranged as a hologram stack. The aforementioned holograms are each designed for at least one defined angle of incidence, thus being efficient. The holographic arrangement can be arranged directly on the optical element or integrated into the optical element. For example, the holographic arrangement can comprise at least one reflection hologram, which is arranged on a surface of the optical element opposite the totally reflecting surface and which reflects light waves at an angle of incidence greater than the critical angle of total reflection of the totally reflecting surface.

[0025] The at least one prism can have a coupling surface for coupling light waves into the prism, which can be configured as a flat surface, a curved surface, an aspherical surface, or a freeform surface. This has the advantage of ensuring a fixed arrangement of the individual components, thus eliminating the need for further adjustment and thus reducing the susceptibility to errors associated with assembly.

[0026] In a further variant, the wavefront manipulator can comprise a further optical element. The further optical element can be a component of the at least one prism or can be arranged freestanding in the beam path. It can be transmissive or reflective, e.g., as a freeform mirror. The at least one prism can have a coupling surface for coupling light waves into the prism, and the further optical element can be designed as a reflective layer on a surface of the prism in the beam path between the coupling surface of the prism and the totally reflecting surface.

[0027] Preferably, the optical element, the holographic arrangement, and the at least one prism are formed integrally as a monolithic component or are firmly connected to one another to form a single component. The resulting fixed geometric arrangement of the individual components relative to one another has the advantages already mentioned.

[0028] The wavefront manipulator according to the invention can be designed for a head-up display, particularly for placement in the beam path between an imaging unit and a projection surface. Further application options include data glasses, cameras, and projectors.

[0029] The optical arrangement according to the invention, e.g., for a head-up display on a projection surface, comprises an imaging unit and a previously described wavefront manipulator. The imaging unit can be arranged directly on a surface of the at least one prism. The imaging unit advantageously comprises an object plane, i.e., is spatially extended, wherein the object plane is designed to emit light within a defined radiation angle range and with a defined maximum bandwidth with respect to the wavelengths of the emitted light. The imaging unit is preferably designed to generate a multicolor image.

[0030] For example, each light-emitting point in the object plane emits light in the form of a scattering lobe or within a defined angular range. This can be achieved, for example, by using a diffuser. Preferably, the imaging unit is designed to emit laser light, in particular laser beams. Advantageously, the imaging unit is designed to emit laser light in at least two, preferably at least three, different wavelengths. These are preferably three different wavelengths of a defined color space, for example, red, green, and blue or cyan, magenta, and yellow. Since the holographic elements are more sensitive to the bandwidth of each wavelength than other optical components, such as mirrors and lenses, it is advantageous if the imaging unit is designed as a laser scanner with a sharp bandwidth for each color.

[0031] The optical arrangement according to the invention preferably has a volume of less than 10 liters, in other words, it occupies a space of less than 10 liters. The optical arrangement according to the invention has the features and advantages already mentioned above in connection with the wavefront manipulator according to the invention. In particular, it offers a very compact arrangement, which therefore occupies only a small amount of space while simultaneously ensuring very high imaging quality.

[0032] Both the wavefront manipulator according to the invention and the optical arrangement according to the invention are suitable for retrofitting in connection with head-up displays in, for example, motor vehicles, aircraft or VR arrangements, for example VR glasses.

[0033] The head-up display according to the invention comprises a projection surface and a previously described optical arrangement according to the invention. The curved projection surface, for example, can be a windshield of a vehicle, for example a motor vehicle, an aircraft, or a ship. However, the projection surface can also be another viewing window, for example a viewing window of VR glasses. The curved projection surface can, for example, be viewed as a freeform surface. By means of the wavefront manipulator according to the invention, imaging errors or aberrations caused thereby are compensated and, in addition, a tilted image plane of a virtual image is generated. The invention is explained in more detail below using exemplary embodiments with reference to the attached figures.Although the invention is illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0034] The figures are not necessarily detailed or to scale and may be enlarged or reduced to provide a better overview. Therefore, the functional details disclosed herein are not to be interpreted in a limiting sense, but merely as an illustrative basis for teaching one skilled in the art how to variously employ the present invention.

[0035] As used herein, the term "and / or," when used in a series of two or more elements, means that any of the listed elements may be used alone, or any combination of two or more of the listed elements may be used. For example, if a composition is described containing components A, B, and / or C, the composition may contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0036] Figure 1 shows schematically the beam path through a wavefront manipulator according to the invention in a side view.

[0037] Figure 2 schematically shows a first variant of a head-up display according to the invention with a wavefront manipulator according to the invention. Figure 3 schematically shows a first variant of a head-up display according to the invention with a wavefront manipulator according to the invention.

[0038] Figure 4 shows schematically a head-up display according to the invention with a wavefront manipulator according to the invention in a second variant.

[0039] Figure 5 schematically shows a head-up display according to the invention with a wavefront manipulator according to the invention in an alternative second variant.

[0040] Figure 6 shows schematically a head-up display according to the invention with a wavefront manipulator according to the invention in a third variant.

[0041] Figure ? shows schematically a head-up display according to the invention with a wavefront manipulator according to the invention in an alternative third variant.

[0042] Figure 8 schematically shows a head-up display according to the invention with a wavefront manipulator according to the invention in a fourth variant.

[0043] Figure 9 schematically shows a head-up display according to the invention with a wavefront manipulator according to the invention in an alternative fourth variant.

[0044] Figure 10 schematically shows a fifth variant of a head-up display according to the invention with a wavefront manipulator according to the invention. Figure 11 schematically shows a fifth variant of a head-up display according to the invention with a wavefront manipulator according to the invention.

[0045] Figure 12 shows schematically an optical arrangement according to the invention with a wavefront manipulator according to the invention in the form of a block diagram.

[0046] Figure 1 schematically shows the beam path through a wavefront manipulator according to the invention in a side view. The wavefront manipulator 1 comprises a holographic arrangement 2 and an optical element 3. The optical element 3 has a first side 4, which forms the underside in the figure shown, and a second side 5, which forms the top side in the figure shown. In the variant shown, the holographic arrangement 2 is arranged on the first side 4, i.e., the underside. In the region in which light rays 6 are coupled into the optical element 3 on the first side 4, the optical element 3 has a coupling device 7. The coupling device 7, not shown in detail in Figure 1, comprises at least one prism and is designed to enable the light 6 to be coupled at an angle such that the coupled light rays can be totally reflected on the second side 5 of the optical element 3.

[0047] The holographic arrangement 2 is arranged in Figure 1 next to the coupling device 7. The light beams 6 totally reflected on the second side 5 strike the holographic arrangement 2 at an angle of incidence for which the holographic arrangement 2 is diffraction-efficient. The holographic arrangement 2 comprises at least one reflection hologram. The light reflected or diffracted by the holographic arrangement 2 is refracted at the second side 5 of the optical element 2 and coupled out of the wavefront manipulator 1. The second side 5 thus comprises an output region. The wavefront manipulator is thus designed as a transmission component with refractive power. The holographic arrangement 2 comprises at least one hologram which, when exposed to its exposure wavelength, is diffraction-efficient for at least one specified angle, which is greater than the critical angle of total reflection of the optical element 3.

[0048] The holographic arrangement 2 can comprise at least one hologram that is diffraction-efficient for a plurality of wavelengths of a defined color space. The holographic arrangement 2 can also comprise a plurality of holograms, each of which is diffraction-efficient for at least one wavelength of a defined color space and at least one defined irradiation angle range. The plurality of holograms can be arranged side by side or in the form of a hologram stack, i.e., stacked on top of one another.

[0049] Compared to conventional hologram arrays formed from reflection holograms, the wavefront manipulator 1 according to the invention has the advantage that only half the number of holograms is required to utilize the advantages of reflection holograms. This reduces costs and simultaneously improves accuracy, since imaging errors that can arise from the arrangement of the holograms on top of one another are avoided.

[0050] In principle, the optical element 3 can be designed as a substrate or waveguide. However, an additional substrate can also be present, and the optical element 3 can be designed as a film or layer. In principle, the optical element 3 can comprise glass or plastic or be made of these materials. The material of the optical element can comprise at least one of the materials already listed above.

[0051] The potentially undesirable zeroth order of diffraction, which forms stray light, remains in the optical element 3 and / or an additional substrate due to total internal reflection and can be suitably guided to a side surface or edge into a beam dump. This is particularly advantageous because the zeroth order light is generally not used and therefore represents stray light. In principle, the wavefront manipulator shown in Figure 1 can be used, for example, in a head-up display. This application is used below for various exemplary embodiments. This does not exclude other applications, for example, in other optical arrangements or optical systems.

[0052] Figure 2 schematically shows a head-up display according to the invention. The head-up display 22 comprises an optical arrangement 10 according to the invention and a projection surface in the form of a windshield 11. A viewer or eyebox 12 indicates the area from which a virtual image projected by the head-up display 22 behind the projection surface 11 is perceivable by a viewer.

[0053] The optical arrangement 10 according to the invention comprises an imaging unit 21 and a wavefront manipulator 1 according to the invention. In addition to the wavefront manipulator 1 already described with reference to Figure 1 with regard to its basic structure, the wavefront manipulator 1 according to the invention comprises a further optical element 23, which is arranged in the beam path between the imaging unit 21 and the coupling device 7. In the variant shown, the further optical element 23 is designed as a freeform mirror. It is designed for beam deflection and aberration correction. Further aberration corrections can be carried out using the prisms of the coupling device 7 and the holographic arrangement 2.

[0054] In the variant shown, the coupling device 7 is designed as an arrangement of a plurality of prisms, in particular as a microprism array. The prisms cause light waves to be coupled into the first side 4 of the optical element 2 at an angle that enables total reflection on the second side 5. In contrast to the variant shown in Figure 1, the holographic arrangement 2 is integrated into the optical element 3 and extends over the entire first side 4 or forms it. Light coming from the further optical element 23, which was previously reflected from the imaging unit 21 at the further optical element 23, is coupled via the coupling device 7, i.e. the microprism array, in the direction of the second side 5 into the optical element

[0055] 3. The light initially transmits through the holographic arrangement 2, preferably without any filtering effects occurring. Since the holographic arrangement 2 is designed as a reflection hologram and is only diffractively efficient for light coming from the direction of the second side 5, no diffraction occurs during transmission, but only for light coming from the second side 5. The light diffracted by the holographic arrangement 2 then strikes the second side 5, is refracted there, and is coupled out of the wavefront manipulator in the direction of the projection surface 11, for example the windshield.

[0056] The alternative variant shown in Figure 3 differs from the variant shown in Figure 2 only in the direction of the arrangement of the coupling device 7, the further optical element 23 and the imaging unit 1 in relation to the projection surface 11. The arrangement is mirror-symmetrical to the variant shown in Figure 2. While in Figure 2 the imaging unit 1 emits light to the left and the coupling device is arranged in the left area of ​​the first side 4, in Figure 3 the imaging unit 21 emits light to the right in the direction of the further optical element 23 arranged on the right in this variant, and is reflected by it in the direction of a projection surface 11 in the right area of ​​the first side

[0057] 4 arranged coupling device 7.

[0058] Figures 4 to 9 show three further embodiments, each in two alternatives, in which, instead of a plurality of prisms, a monolithic or a single prism is used as the coupling device 7. In all embodiments shown, the optical element 3 with the coupling device 7 and the holographic arrangement 2 are formed as a monolithic component, i.e., in one piece. Alternatively, the aforementioned components can be firmly connected to one another. However, a monolithic design has the advantage that a precise arrangement of the aforementioned components relative to one another can be ensured during production, thus making them robust with regard to their further installation as part of an optical component or optical arrangement. No additional adjustment is required, and no additional production-related aberrations occur.

[0059] In the variant shown in Figure 4, a prism 7 is arranged on the first side 4 or surrounded by it. The prism 7 has a coupling surface 8. The coupling surface 8 is designed to couple light, for example from an imaging unit 21, into the wavefront manipulator 1. For this purpose, the coupling surface 8 is preferably in the form of a transmissive freeform surface. Aberrations can be corrected by means of the freeform surface 8. The coupling surface 8 can be curved, in particular convexly curved. Light coupled in via the coupling surface 8 transmits the holographic arrangement 2 after passing through the prism 7, is totally reflected at the second side 5 of the optical element 3 and is then diffracted by the holographic arrangement 2 in the direction of the second side 5, as already explained with reference to Figures 1-3.

[0060] The variant shown in Figure 5 differs from the variant shown in Figure 4 only in the geometric arrangement of the prism 7 and the imaging unit 21, i.e., the optical arrangement 1 according to the invention, in relation to the projection surface 11. While in Figure 4 the imaging unit 21 and the prism 7 are arranged to the left below the holographic arrangement 2, in Figure 5 the prism 7 and the imaging unit 21 are arranged to the right below the holographic arrangement 2.

[0061] In the variant shown in Figure 6, the prism 7 has, in addition to a curved coupling surface 8, for example, designed as a freeform surface, a reflective element 9 in the form of a reflective layer 9. The reflective layer 9 can be designed as an optical element arranged directly on a surface of the prism 7 or can be integrated into the prism 7. The reflective element 9 can be flat, i.e., as a planar reflective surface, or as a freeform surface. The coupling surface 8 and the reflective surface 9 are arranged on the prism 7 in such a way that light coupled in through the coupling surface 8 is reflected by the reflective surface 9 such that the holographic arrangement 2 transmits it toward the second side 5 at an angle of incidence that is greater than the critical angle of total internal reflection on the second side 5.As a coupling device, prism 7 ensures, on the one hand, the coupling of light at an angle that enables total internal reflection on the second side 5. It also provides two surfaces, namely the coupling surface 8 and the reflective surface 9, for aberration correction. Unlike the variant shown in Figures 4 and 5, the coupling surface 8 is concavely curved.

[0062] The variant shown in Figure 7 differs from the variant shown in Figure 6 only in the geometric arrangement of the imaging unit 21 and the prism 7 in relation to the projection surface 11. While in Figure 6 light is coupled into the prism 7 from the right and reflected at a reflection surface 9 arranged on the left, in Figure 7 light is coupled into the prism from the left through the coupling surface 8 by the imaging unit 21 and reflected at a reflective surface 9 arranged on the right.

[0063] In the embodiments shown in Figures 8 and 9, the imaging unit 21 is arranged directly on a coupling surface 8 of the prism 7. In other words, no further optically effective component or element is arranged between the imaging unit 21 and the coupling surface 8 of the prism 7. In this variant, the coupling surface 8 can be designed as a flat surface. Opposite the coupling surface 8, the prism 7 has a reflective surface 9, for example in the form of a layer. This reflective surface 9 is designed, analogous to the embodiments shown in Figures 6 and 7, to guide a coupled light into the prism 7 in the direction of the second side 5 for total reflection there. In contrast to the embodiments shown in Figure

[0064] In contrast to the variants shown in Figures 6 and 7, in Figures 8 and 9 the reflective surface 9 is curved, for example, as a curved freeform surface. While in Figure 8 the imaging unit 21 radiates light coming from the right into the prism 7 and is reflected from the left by the reflective surface 9 toward the second surface 5, in Figure 9 the imaging unit 21 couples light to the right into the prism 7 and reflects it to the left by the reflective surface 9 toward the second surface 5.

[0065] In the examples shown, the light undergoes one total reflection within the optical element 3. In principle, multiple total reflections within the optical element are also possible. However, only one total reflection has the advantage that the simple beam deflection does not cause any further aberrations.

[0066] In the following, alternative design variants to the examples shown in Figures 6 and 7 are described with reference to Figures 10 and 11. In contrast to the examples in Figures 6 and 7, the light beams coupled in via the coupling surface 8 are transmitted by the holographic arrangement 2 in the direction of the reflective element 9 after the first total reflection on the second side 5, reflected by the latter, then transmitted by the holographic arrangement 2 in the direction of the second side 5 and, after a second total reflection on the second side 5, reflected by the holographic arrangement 2. The coupling surface 8 and / or the reflective element 9 can be designed for aberration correction. They are preferably designed such that they interact for aberration correction. For example, they can be designed as freeform surfaces and / or comprise at least one hologram.This design offers the advantages of reduced installation space and improved correction of imaging errors.

[0067] In all previously described examples and variants, multiple surfaces and / or elements of the prism can be designed to cooperate for aberration correction. Furthermore, the prism and the holographic arrangement can be designed to cooperate for aberration correction. For example, the coupling surface and / or a reflective element of the prism and / or the holographic arrangement can be designed to cooperate for aberration correction.

[0068] Figure 12 schematically shows an optical arrangement 10 according to the invention with a wavefront manipulator 1 according to the invention in the form of a block diagram. The optical arrangement 10 according to the invention comprises an imaging unit 21 and a wavefront manipulator 1 according to the invention, which are arranged one behind the other in a beam path 6. The wavefront manipulator 1 comprises a previously described holographic arrangement 2 and an optical element 3 having a coupling device 7.

[0069] List of reference symbols:

[0070] 1 wavefront manipulator

[0071] 2 holographic arrangement

[0072] 3 optical element

[0073] 4 first page / subpage

[0074] 5 second side / top

[0075] 6 Beam path

[0076] 7 Coupling device

[0077] 8 Coupling area

[0078] 9 reflective element

[0079] 10 optical arrangement

[0080] 11 Projection screen

[0081] 12 Eyebox

[0082] 21 imaging unit

[0083] 22 Head-up display

[0084] 23 additional optical element

Claims

Patent claims 1. Wavefront manipulator (1) comprising a holographic arrangement (2) and an optical element (3), characterized in that the optical element (3) comprises at least one totally reflecting surface (5) for a defined angle of incidence range for illuminating light waves onto the holographic arrangement (2) and wherein the holographic arrangement (2) comprises at least one reflection hologram for reflecting light waves incident on the holographic arrangement (2) by means of the optical element (3), wherein the optical element (3) comprises a coupling device (7) for coupling light waves into the wavefront manipulator (1), which comprises at least one prism.

2. Wavefront manipulator (1 ) according to claim 1 , characterized in that the holographic arrangement (2) is arranged downstream of the optical element (3) in the beam path (6) or is arranged in the beam path (6) such that it transmits light waves in the beam path (6) immediately behind the coupling device (7) and reflects them behind the totally reflective surface (5).

3. Wavefront manipulator (1 ) according to claim 1 or claim 2, characterized in that the wavefront manipulator (1 ) is designed as a transmission component.

4. Wavefront manipulator (1 ) according to one of claims 1 to 3, characterized in that the coupling device (7) comprises a plurality of prisms.

5. Wavefront manipulator (1) according to claim 4, characterized in that The majority of prisms are arranged as a microprism array.

6. Wavefront manipulator (1 ) according to one of claims 1 to 5, characterized in that the optical element (3) comprises a first side (4) and a second side (5) opposite the first side (4), wherein the coupling device (7) and the holographic arrangement (2) are arranged on the first side (4) and the totally reflecting surface is arranged on the second side (5).

7. Wavefront manipulator (1 ) according to one of claims 1 to 6, characterized in that the totally reflective surface (5) comprises an output coupling area.

8. Wavefront manipulator (1 ) according to one of claims 1 to 7, characterized in that the wavefront manipulator (1 ) has an output coupling area which at least partially comprises the totally reflective surface (5), wherein the input coupling device (7) and the output coupling area overlap at least partially in a direction perpendicular to a surface normal of the totally reflective surface (5).

9. Wavefront manipulator (1 ) according to one of claims 1 to 8, characterized in that the optical element (3) is designed such that light waves between the coupling device (7) and the holographic arrangement (2) undergo a defined number n of total internal reflections within the optical element (3).

10. Wavefront manipulator (1) according to one of claims 1 to 9, characterized in that holographic arrangement (2) comprises at least one reflection hologram designed to reflect a plurality of wavelengths, or comprises a plurality of reflection holograms, each of which are designed for at least one wavelength of light of a color within a color space.

11. Wavefront manipulator (1 ) according to one of claims 1 to 10, characterized in that the holographic arrangement (3) is arranged directly on the optical element (2) or is integrated into the optical element (2).

12. Wavefront manipulator (1 ) according to one of claims 1 to 11 , characterized in that the holographic arrangement (3) comprises at least one reflection hologram which is arranged on a surface (4) of the optical element (3) opposite the totally reflective surface (5) and which reflects light waves at an angle of incidence which is greater than the critical angle of total reflection of the totally reflective surface (5).

13. Wavefront manipulator (1 ) according to one of claims 1 to 12, characterized in that the at least one prism (7) has a coupling surface (8) for coupling light waves into the prism (7), which is designed as a planar surface or curved surface or aspherical surface or as a freeform surface.

14. Wavefront manipulator (1 ) according to one of claims 1 to 13, characterized in that the wavefront manipulator (1 ) comprises a further optical element (23, 9).

15. Wavefront manipulator (1) according to claim 14, characterized in that the at least one prism (7) has a coupling surface (8) for coupling light waves into the prism (7) and the further optical element (9) is a reflective layer on a surface of the prism (7) in the beam path (6) is formed between the coupling surface (8) of the primas (7) and the totally reflecting surface (5).

16. Wavefront manipulator (1 ) according to one of claims 1 to 15, characterized in that the optical element (3), the holographic arrangement (2) and the at least one prism (7) are formed in one piece as a monolithic component or are firmly connected together to form one component.

17. Optical arrangement (10) comprising an imaging unit (21) characterized in that the optical arrangement (10) comprises a wavefront manipulator (1) according to any one of claims 1 to 16.

18. Optical arrangement (10) according to claim 17, characterized in that the imaging unit (21 ) is arranged directly on a surface (8) of the at least one prism (7).

19. Head-up display (22) comprising a projection surface (11) characterized in that the head-up display (22) comprises an optical arrangement (10) according to one of claims 17 or 18.

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