HEAD-UP-DISPLAY

Description

[0001] The present invention relates to a head-up display having a projection system.

[0002] US 2016 / 0335959 A1 shows a head-up display with a display element, a projection system, a lens, and a mirror element. A disadvantage of this known head-up display is that stray light falling onto the lens from outside toward the projection system is reflected by the surface of the lens in directions where it can reach the viewer's eye via the optical system, thus causing irritation to the viewer.

[0003] From US 2015 / 253469 A1 a head-up display according to the preamble of claim 1 is known.

[0004] A head-up display that causes less irritation from incoming stray light is desirable.

[0005] This is achieved by the measures specified in the independent claims. According to the invention, the focusing elements are arranged irregularly on the surface of the diffuser. This has, among other advantages, the suppression of moiré patterns.

[0006] According to the invention, in a head-up display having an intermediate image generation unit consisting of a display element and a projection system, a diffuser, and a mirror element, it is proposed that the diffuser have focusing elements on its side facing the projection system and a light-blocking mask on its side facing away from the projection system. This has the advantage that the mask blocks stray light, which thus does not reach the projection system or the intermediate image plane and cannot create interfering reflections or the like there. The focusing elements focus the light coming from the projection system onto openings in the mask, so that almost all of the light emitted by the projection system also reaches the mirror element and thus towards the viewer. Due to the focusing elements, the light is directed into an angular range that is useful for the viewer.Likewise, interference reflections generated in the scattering element by total internal reflection, also known as TIR, are effectively reduced by the arrangement according to the invention.

[0007] The display element can be a self-luminous display element, for example an OLED display based on organic light-emitting diodes, a backlit display element, for example a liquid crystal LCD display, or a reflective display element, for example a DMD display based on digital micromirrors. The projection system projects the image of the display element and enlarges it. A reduced projection can also be useful under certain circumstances. The diffuser is arranged in an intermediate image plane of the projection system. The image on the diffuser is transformed into a virtual image by a virtualization system and superimposed on the surroundings by means of the mirror element. In many cases, the windshield of the vehicle or a so-called combiner arranged between it and the viewer serves as the mirror element.Instead of the diffuser, a different, non-disc-shaped diffuser element can also be used effectively. For example, a combination of a folding mirror and a concave mirror is used as a virtualization system.

[0008] The light-blocking mask is preferably made of a light-absorbing material. This has the advantage that stray light incident toward the projection system is absorbed by the mask. Stray light passing through the mask's openings, which is reflected by the focusing elements, largely reaches the rear part of the mask, where it is absorbed. Only a tiny fraction passes back through the mask's openings a second time or is not reflected by the focusing elements onto the mask, thus reaching the viewer's eye as stray light. In this way, stray light, such as sunlight entering the head-up display, is effectively reduced.

[0009] The focusing elements are envisaged to be formed by a microlens field, also referred to as a microlens array. This has the advantage that such a microlens array can be manufactured cost-effectively.

[0010] According to the invention, the microlenses of the microlens array are arranged at an angle. Depending on their distance from the optical axis, the microlenses are tilted so that outgoing light beams passing through the opening of the mask exhibit the best possible adaptation to the virtualization system. This has the advantage that all areas of the diffuser are perceived evenly by the viewer in the virtual image. Such a tilt is easily achieved by arranging the individual microlenses at different distances from the openings of the mask. The resulting incidence of light more or less outside the respective optical axis of the individual microlenses has an effect corresponding to a tilt. A pure displacement compared to a tilt facilitates the manufacture of the microlens array.

[0011] Advantageously, the diffusion screen has a further surface structure on the side of the light-blocking mask facing away from the projection system or the intermediate image generation unit. This has the advantage that it enables further light shaping without having to arrange an additional component in the beam path. This saves installation space. The surface structure is formed, for example, by a large number of lens surfaces arranged next to one another, whereby the number can also be quite small; in extreme cases, a single lens surface is provided as the surface structure. Alternatively, the mask itself can have a surface structure. This is designed, for example, as a Fresnel lens, as a diffuser or as a structure enabling another desired effect. If such a surface structure is provided on the side facing away from the projection system or the intermediate image generation unit,If the mask is arranged on the side of the mask facing the intermediate image generation unit, this has the advantage that, due to the function of the mask, hardly any back reflections occur when stray light is incident from above.

[0012] According to the invention, the additional surface structure is one that implements a field lens function. This has the advantage that a field lens, which is already required in the head-up display, is integrated into the diffuser. For this purpose, the surface structure is designed, for example, as a Fresnel lens structure. If a microlens arrangement is provided as the surface structure, this implements the field lens function in combination with the microlens array. A suitable field lens effect is achieved by skillfully selecting the distances between the lenses of the two microlens arrangements.

[0013] Advantageously, the mask's openings occupy less than 5% of the mask's surface area. This has the advantage that, ideally, more than 95% of stray light is eliminated the first time it hits the mask. The small opening area means that the light focused by the focusing elements exits the mask's openings with an aperture angle of approximately 30°, which is well suited for a head-up display.

[0014] A variant of the head-up display according to the invention has, instead of a display element and a projection system, another intermediate image generation unit, preferably a phase modulator or a laser scanning system. Even with such an intermediate image generation unit, the diffuser according to the invention can effectively reduce annoying reflections.

[0015] An even better suppression of moiré patterns is achieved when the focusing elements themselves have irregular shapes.

[0016] Alternatively or additionally, the focusing elements are designed to have a common structure size. Thus, no significantly larger or significantly smaller structures occur than the average. This prevents large-scale, perceptible variations in illumination.

[0017] According to the invention, the focusing elements have a round shape and / or an elongated shape and / or an irregular shape. A combination of these shapes, in particular, results in particularly good suppression of moiré patterns.

[0018] An optical unit according to the invention for a head-up display comprises a display element, a projection system, and a lens as described above. The optical unit is suitable for forming a head-up display according to the invention when combined with a mirror element and has the advantages mentioned for the above-mentioned inventive head-up displays. Often, the optical unit is the cost-effective unit that forms a head-up display only when installed in a vehicle with the mirror element located therein, in particular the windshield.

[0019] In a method according to the invention for producing a head-up display, focusing elements are first produced on a first side of a carrier of a diffuser. This is done, for example, using a correspondingly designed injection mold, by means of which the diffuser element is produced. A coating is applied to the second side opposite the first side. This coating can be light-blocking, and in this case both absorbent on both sides, absorbent towards the diffuser and reflective on the side facing away from the diffuser. Instead of a light-blocking coating, another coating can also be provided, for example a photoresist. The first side is then exposed to a beam of rays with defined properties, with an intensity and duration, etc., that is suitable for creating openings in the coating.If necessary, a combination with etching medium or other suitable measures can be carried out here. The diffuser is then combined with a projection system capable of generating a beam of rays with the aforementioned defined properties, as well as with a display element. This has the advantage of ensuring that the diffuser and mask are optimally adapted to the projection system. Alternatively, the diffuser and projection system are first combined, and the exposure then takes place through the projection system combined with the diffuser. This also ensures that the diffuser and projection system are optimally adapted to one another. A process consisting of application, exposure, etching, and bonding can also be used here. Pulse scanning or other suitable methods can also be used effectively.

[0020] In a process according to one aspect of the invention, also known as a "lift-off process," a photoresist is applied to the back of the lens array. This photoresist is exposed through the lens array and remains in the exposed areas, i.e., where the openings will later be located. Subsequently, an opaque coating is applied. The remaining photoresist is then dissolved, thereby also removing the coating above it. This creates the openings of the mask.

[0021] In a manufacturing method according to the invention, an adhesive is applied to the second side of the diffuser prior to combining, to which a microlens array is applied, which is then adjusted with respect to the focusing elements, and the adhesive is subsequently cured. This represents an efficient way of producing the diffuser with a microlens array. Purely adhesive bonding, clamps, or a non-curable adhesive can also be used effectively here.

[0022] These and other variants and advantages of the invention are set forth in the following description of exemplary embodiments and can be gathered from them and from the figures. They show: Fig.1Head-Up-Display in schematic representation Fig.2Diffuser Fig.3Variant of a diffusion screen Fig.4Variant of a Head-Up-Display Fig.5Exemplary microlens array Fig.6 Fig.10Exemplary microlens array Fig.7Manufacturing process Fig.8Flow diagram of a manufacturing process Fig.9Enlarged section from Fig.2 Variant of a head-up display

[0023] Fig.1 shows a head-up display according to the invention with a display element 1, a projection system 2, a lens 3, and a mirror element 4. The mirror element 4 is designed here as the windshield 41 of a motor vehicle. The display element 1 is illuminated by a light source 11. The light coming from the light source 11 is reflected by the display element 1 in the direction of the projection system 2. This projects and enlarges or, if designed accordingly, reduces the image of the display element onto the lens 3. From there, it is reflected by a folding mirror 44 onto a concave mirror 45, which in turn enlarges it and transforms it into a virtual image. The light coming from the concave mirror 45 is reflected by the mirror element 4, the windshield 41, into the viewer's eye 42.It is superimposed on the image of the surroundings visible through the windshield 41 and appears as a virtual image VB in the direction of travel in front of the windshield above the hood of the vehicle or even in front of the vehicle.

[0024] It can be seen that the diffuser 3 has focusing elements 31 on its lower side in the figure. According to the invention, these are arranged irregularly on the surface of the diffuser 3, even if this may not always be clearly visible due to the size ratios in this and some of the following figures. A clearly visible example is shown below. Fig.11 described. The focusing elements 31 face the projection system 2. On the side of the diffusion screen 3 facing away from the projection system 2 is a light-blocking mask 32. The light-blocking mask 32 has openings 321 through which light coming from the projection system 2 and focused by the focusing elements 31 passes and reaches the folding mirror 44.

[0025] In the following illustrations, reference numerals are used for identical or equivalent elements as previously described. Individual elements are not necessarily described again unless this is deemed necessary for further understanding.

[0026] Fig.2 shows a diffuser 3 according to the invention in an enlarged view. Light coming from a lens 21 of the projection system 2 can be seen, which is focused by the focusing elements 31 onto openings 321 of the light-blocking mask 32. The corresponding light beams are shown by solid lines, and the direction of propagation is indicated by arrows. Also visible is stray light LS, indicated by dashed lines, which comes from the top right and falls onto the diffuser 3. This is, in particular, sunlight, which, under unfavorable conditions, shines into the head-up display and typically reaches the diffuser 3 via a virtualization system, which here is formed by the folding mirror 44 and the concave mirror 45.The left part of the figure shows stray light LS1, which passes through one of the openings 321 of the light-blocking mask 32, is reflected at the interface of one of the focusing elements 31, and strikes the light-blocking mask 32 from below. See also the . Fig.9 , in which the dashed area 9 is shown enlarged. The mask 32 is absorbent on its side facing the focusing elements 31, so that the stray light LS1 reaching it from below is absorbed there. On the right-hand side, stray light LS2 is shown, which is reflected at the top side of the light-blocking mask 32. According to a variant of the invention, the light-blocking mask 32 is also designed to be absorbent on its top side, so that the stray light LS2 is also absorbed by the light-blocking mask 32 and cannot cause irritation. The focusing elements 31 are microlenses 311 arranged as a microlens array. In the left-hand part of the figure, the individual microlenses 312, 313, 314 are arranged tilted with respect to the other microlenses 311. This means that their axis of symmetry is not perpendicular to the plane of the diffuser 3, but is inclined at different angles depending on the distance from the center.This serves to distribute the light incident toward the edge of the diffusion plate 3 as optimally as possible. The tilted microlenses 312-314 are shown here only as examples; the tilt angle is not necessarily shown to scale, but is intended to illustrate the principle. The openings 321 can also be formed, for example, as transparent areas of a mask 32 realized as photographic film.

[0027] The useful light, coming from the projection system 2, passes through the focusing elements 31 or any additional components of the diffuser 3, and then passes through the openings 321 of the light-blocking mask 32, which acts as an aperture mask. If the radiation direction is to be further controlled, the microlenses 311-314 are tilted in a suitable manner, and the position of the openings is adjusted. The stray light LS, LS1, LS2, when it strikes the light-blocking mask 32, is blocked on the sun-facing side (here, the upper side) if the mask 32 is of an absorbent design. If the sun-facing side of the mask 32 is of a reflective design, it is reflected, as shown for stray light LS2. This is typically combined with a tilt of the diffuser 3, see Fig.4 In this way, the stray light LS2 is guided from the beam path into a light trap. With a reflective sun-facing side, the upper side in the illustration, better stray light suppression can generally be expected than with an absorbent sun-facing side, since good absorbers are not the norm. However, a tilt or a similar measure is then required to prevent reflection back into the driver's eye 42. On the projector-facing side, the lower side in the illustration, an absorbent layer is provided, as shown. Otherwise, there is a risk that light will run uncontrolled within the lens 3 and thus cause a reduction in contrast.

[0028] Fig.3 shows a further variant of a diffuser 3 according to the invention. In this case, in the illustration, a further surface structure 33 is arranged above the light-blocking mask 32. This also consists of many microlenses 331 arranged next to one another, which are designed such that, in combination with the lower focusing elements 31, they realize a field lens function. The microlenses 331 above and the microlenses 311 below the mask 32 are not shifted relative to one another in the central region of the diffuser 3, so that light in the central region is almost not deflected. The further away from the central region the microlenses 331, 311 are located, the more they are shifted relative to one another, so that light in the outer region is tilted more towards the optical axis the further away from the optical axis it passes through the diffuser 3.Thus, a field lens effect is achieved by the different grating spacings of the microlenses 331 and the microlenses 311. The light traveling from the diffusion screen 3 toward the mirror element 4 has an aperture angle and an orientation that are predetermined by the design of the surface structure 33. A stray light beam LS2 can be seen here, which strikes the light-blocking mask 32 through the microlenses 331 and is absorbed there. The mask 32, which is shown in . Fig.3 is shown, is designed to be absorbent on both sides. The second surface structure 33 serves to further shape the useful light. One advantage lies in the possibility of integrating a field lens function with uniform lens arrays. A design with a reflective side facing the sun is an option that can be used sensibly under suitable conditions. In area 10, on the left-hand side, as an alternative variant, a surface structure 34 of the diffuser plate 3, which is arranged above the mask 32, is shown schematically and by way of example. This is provided instead of the surface structure 33, which is applied as a separate layer. On the right-hand side of area 10, a surface structure 35 of the diffuser plate 3 is shown, which is arranged below the mask 32, shown schematically and by way of example. This surface structure 35 has a microstructure that produces Fresnel effects.For example, one can see a slope under the openings of the mask 32. An advantage of the arrangement of the surface structure 35 below the mask 32 is that, due to the function of the mask 32, hardly any back reflections occur when stray light is incident from above.

[0029] Fig.4 shows a variant of a head-up display according to the invention. The optical elements are arranged essentially as in Fig.1 described. One difference is that the diffuser 3 is tilted relative to the optical axis of the light coming from the virtualization system, here the folding mirror 44 and the concave mirror 45. The tilt angle is not necessarily shown to scale here, but is exaggerated to illustrate the principle. It can be seen that the stray light LS coming from the sun 40, shown in dashed lines, after passing through the windshield 41, travels at the same angle as the light coming from the concave mirror 45, shown in solid lines, but in the opposite direction. The stray light LS then reaches the head-up display. It is reflected by the concave mirror 45 and the folding mirror 44 and strikes the light-blocking mask 32 of the diffuser 3.The light-blocking mask 32 shown here has a reflective surface on its side facing away from the focusing elements 31, so that the stray light LS is reflected. Due to the tilt of the diffuser 3, the stray light LS is directed outward through an opening 51 of a housing 5 of the head-up display, where it does not re-enter the viewer's eye 42 and thus does not cause irritation.

[0030] Fig.5 shows a section of a regular microlens array 310 consisting of microlenses 311 or a microlens arrangement 330 consisting of microlenses 331, which do not fall within the scope of the claims. The microlens array 310 and the microlens arrangement 330 can, in principle, be constructed similarly; the sizes of the microlenses 311, 331, their curvature, and other optical properties differ according to their function. Here, the microlenses 311, 331 each cover a rectangular area and merge seamlessly into one another. In an alternative part of the illustrated microlens array 310 or the microlens arrangement 330, non-transparent regions 319 are located between the microlenses 311, 331. These serve to block any undefined light refracted between the individual microlenses 311, 331 due to manufacturing inaccuracies in the surface, thus avoiding potential irritation to the viewer.

[0031] Fig.6 shows another microlens array 310 or another microlens arrangement 330 which does not fall within the scope of the claims. In these, the microlenses 311, 331 are regularly arranged according to the hexagonal closest packing. Between the microlenses 311, 331 are regions 319. These are advantageously designed to be non-transparent. Light incident there would only be correctly refracted onto one of the openings 51 associated with the adjacent microlenses 311 by a surface geometry that would require disproportionate effort to produce, or light coming from the openings 51 would only be correctly refracted by one of the corresponding microlenses 331 by a surface geometry that would require disproportionate effort to produce. The regions 319 are therefore non-transparent and shade the light incident on them.

[0032] Fig.9 shows an enlarged section of area 9 of the Fig.2 . The stray light LS1 incident from outside can be seen, which passes through an opening 321 of the light-blocking mask 32, is reflected at a boundary layer of one of the focusing elements 31, and then falls from below onto the light-blocking mask 32. A disturbing reflection is thus avoided. This advantage is also achieved when the light-blocking mask 32 is designed to be reflective on its upper side and absorbent on its underside.

[0033] Fig.10 shows a part of a head-up display corresponding to the lower right part of the Fig.1 , in which, instead of the display element 1 and the projection system 2, a phase modulator 12 is arranged between the light source 11 and the diffusion plate 3 as an intermediate image generation unit. The beam path following the folding mirror 44 corresponds to that to Fig.1 shown, and is therefore not shown again here. The phase modulator 12 is shown here in transmission, but is often also used in reflection. It generally also has one or more lenses and possibly other optical elements that are not visible in this simplified representation.

[0034] Fig.11 shows an example of focusing elements 31, 315, 316, 317 arranged irregularly on the surface of the diffuser plate 3 according to the invention. In this exemplary embodiment, the diffuser plate 3 is a diffuser produced by interference lithography. The focusing elements 31, 315, 316, 317 also have irregular shapes. What they have in common is the structure size. Thus, there are no significantly larger or significantly smaller structures. There are focusing elements 315 with a nearly round shape. These have similar optical properties to the microlenses described above, for example, they focus on a point or almost on a point. There are focusing elements 316 with a more elongated shape. These have a more elongated focus, a focus line. There are also focusing elements 317 with an irregular shape. This leads to a rather irregular focus geometry.The mask produced by exposure according to a method according to the invention accordingly has an irregular distribution of irregularly shaped openings that are optimally adapted to the diffuser 3, which has irregularly arranged and shaped focusing elements 31, 315, 316, 317. This variant exhibits very good suppression of moiré patterns.

[0035] Fig.7 shows a manufacturing method according to the invention. In a step S1, an arrangement 310 of focusing elements 31 is applied to a carrier 3', which may already have the scattering property of the diffusion plate 3, wherein the focusing elements 31, 315, 316, 317 are arranged irregularly on the surface of the diffusion plate 3. The application is indicated by an arrow. In a step S2, a light-blocking coating 320 is applied to the opposite side of the carrier 3'. In a step S3, the side of the carrier 3' provided with the focusing elements 31 is exposed to a beam SB of defined geometric properties with a wavelength, an intensity, and a duration suitable for creating openings 321 in the coating. Such openings 321 are shown in the preceding figures. In a step S4, the carrier 3' is combined with a projection system 2 and a display element 1.The projection system 2 is capable of generating a beam SB with the aforementioned defined geometric properties, which, however, generally differs in wavelength, intensity, and / or duration from the beam used to create the openings. Such a combination is described, for example, in . Fig.1 and Fig.4 shown.

[0036] To produce an extended diffuser 3, an adhesive 333 is applied to the second side of the diffuser 3, which is provided with the light-blocking mask 32, in a step S31. In a subsequent step S32, a microlens array 330 is applied to the adhesive 333 and then, in a step S33, adjusted with respect to the focusing elements 31. After adjustment, the adhesive 333 is cured in a step S34. For this purpose, an adhesive 333 curable by UV radiation is used, for example. Exposure to UV light preferably occurs from the side facing away from the focusing elements 31. Fig.8 shows a corresponding flow chart in which the optional steps S31 to S34 are shown in dashed lines.

[0037] In the manufacturing process, it is advisable to perform the exposure through the lens array from the direction of the projection system 2. The openings in the mask 32 are then applied in an optimally aligned manner by laser ablation or other interactions of the light with the unstructured mask, the light-blocking coating 320. This is achieved, for example, by improving solubility at the exposed areas.

[0038] In projector-based windshield head-up displays, where the driver sees the virtual image VB in an area where they can see outward through the windshield 41, there is a path through which sunlight LS can strike the diffusion screen 3 located in the intermediate image plane, onto which the image is projected for the further imaging stage to form a virtual image VB. This sunlight LS is also partially focused to a greater or lesser extent by the imaging stage. Located in the intermediate image plane is the diffusion screen 3 or another type of diffusion screen, which makes the image visible via the so-called eyebox. Due to this function, the diffusion screen 3 is often also referred to as an exit pupil expander.The lens 3 also reflects a portion of the sunlight LS, which can reduce the image contrast, or cause this light to become visible to the driver in the form of unwanted and / or disturbing reflections or brightening. The present invention significantly reduces reflections from the lens 3 or redirects them in directions where they can no longer be perceived from the eyebox.

[0039] The eyebox is the spatial area in which the viewer's eye 42 must be located in order to perceive the virtual image VB completely, i.e. without cropping. If the viewer's eye 42 is located outside the eyebox, the virtual image VB is only partially perceptible or not perceptible at all. If the stray light LS is directed into a spatial area that lies outside the eyebox, it at least does not have an irritating effect on the virtual image VB generated by the head-up display. Disturbing reflections are also largely avoided in the larger, extended eyebox with the help of the invention. The extended eyebox is understood to be the area in which the driver's eye can also be located, but from which area the head-up display is not or only partially visible.

[0040] According to the invention, a diffusion screen 3 is constructed with focusing elements 31, for example, with a microlens array 310. The entrance apertures of the microlenses 311 are directed toward the projection system 2. In the basic embodiment, a light-blocking mask 32 is located on the side of the sunlight incidence, which is designed such that the light coming from the projection system 2 can pass through it, but most other light is blocked. The incident sunlight LS can only pass through the mask 32 through its openings 321; the rest is absorbed or, in the case of a reflective mask 32, directed into a light trap. Thus, only residually reflected light and light scattered at the openings 321 or at the mask 32 returns from the surface.The sunlight that nevertheless passes through and is reflected, possibly totally reflected, from the side of the structure facing the projection system 2 must again pass through the mask 32 to exhibit a disturbing effect. Overall, this approach significantly reduces the tendency of the diffusion screen 3, which acts as an eye-pupil expander, to reflect back.

[0041] According to the invention, the function of an exit pupil expander, which is fulfilled here by the diffusion screen 3, is supplemented by a special mask 32 that allows for stray light filtering. In further variants, a light trap is additionally used or further beam shaping is carried out. In addition to the basic design, the following variants are mentioned, among others: a fully absorbent mask is used, a fully reflective mask, a mask that is reflective on one side and absorbent on one side. Further variants comprise a combination with a second structured surface 33 for further beam shaping. The mask 32 is preferably created by exposure through the structure itself, for example in conjunction with short-pulse lasers.

[0042] It is within the skill of the art to modify one or more of the aforementioned measures or to use them in a different combination, even if they are not explicitly described here. The invention is defined in the independent claims.

Claims

1. Head-up display comprising either a display element (1) and a projection system (2) or an intermediate image generation unit, in which an image is only created in an intermediate image plane, and a light source (11), a diffusing plate (3) and a mirror element (4, 41), wherein the projection system (2) or the intermediate image generation unit is arranged between the light source (11) and the diffusing plate (3), and wherein the diffusing plate (3) comprises focusing elements (31, 315, 316, 317) on its side facing the projection system (2) or intermediate image generation unit and a light-blocking mask (32) on its side facing away from the projection system (2) or intermediate image generation unit, wherein the focusing elements (31, 315, 316, 317) are configured to focus light coming from the projection system (2) or intermediate image generation unit on openings in the light-blocking mask (32), characterized in that the focusing elements (31, 315, 316, 317) are arranged irregularly on the surface area of the diffusing plate (3).

2. Head-up display according to Claim 1, wherein the light-blocking mask (32) consists of a light-absorbing material.

3. Head-up display according to either of the preceding claims, wherein the focusing elements (31) are formed by a microlens array (310).

4. Head-up display according to Claim 3, wherein the microlenses (312-314) of the microlens array (310) are arranged in tilted fashion.

5. Head-up display according to any of the preceding claims, wherein the diffusing plate (3) comprises a further surface structure (33, 34) on the side of the light-blocking mask (32) facing away from the projection system (2) or intermediate image generation unit.

6. Head-up display according to any of Claims 1 to 4, wherein the diffusing plate (3) comprises a further surface structure (35) on the side of the light-blocking mask (32) facing the projection system (2) or intermediate image generation unit.

7. Head-up display according to either of Claims 5 and 6, wherein the surface structure (33) is a surface structure that realizes a field lens function.

8. Head-up display according to any of the preceding claims, wherein the openings (51) in the mask (32) make up less than 5% of the surface area of the mask (32).

9. Head-up display according to any of the preceding claims, wherein the intermediate image generation unit is a phase modulator (12) or a laser scanning system.

10. Head-up display according to any of the preceding claims, wherein the focusing elements (31, 315, 316, 317) have irregular shapes.

11. Head-up display according to Claim 10, wherein the focusing elements (31, 315, 316, 317) have a common structure size.

12. Head-up display according to either of Claims 10 and 11, wherein the focusing elements (31, 315, 316, 317) have at least one of a round shape, an elongate shape and an irregular shape.

13. Optical unit for a head-up display according to any of the preceding claims comprising the optical unit and a mirror element (4, 41), wherein the optical unit comprises a display element (1), a projection system (2) and a diffusing plate (3), wherein the diffusing plate (3) comprises focusing elements (31, 315, 316, 317) on its side facing the projection system (2) and a light-blocking mask (32) on its side facing away from the projection system (2), wherein the focusing elements (31, 315, 316, 317) are configured to focus light coming from the projection system (2) on openings in the light-blocking mask (32), characterized in that the focusing elements (31, 315, 316, 317) are arranged irregularly on the surface area of the diffusing plate (3).

14. Method for producing a head-up display, including the steps of: - creating (S1) focusing elements (31, 315, 316, 317) on a first side of a diffusing plate (3), wherein the focusing elements (31, 315, 316, 317) are arranged irregularly on the surface area of the diffusing plate (3); - applying (S2) a light-blocking coating (320) to the second side of the diffusing plate (3) that lies opposite the first side; - exposing (S3) the first side to a beam (SB) having defined geometric properties with a wavelength, an intensity and a duration suitable for creating openings (321) in the coating (320); - applying the openings (321) by laser ablation or other interactions of the light with the coating (320); - combining (S4) the diffusing plate (3) with a projection system (2) that is able to create a beam having the stated defined geometric properties and with a display element (1).

15. Method according to Claim 14, including the steps of: - applying (S31) an adhesive (333) to the second side of the diffusing plate (3); - applying (S32) a microlens arrangement (330) to the second side that has been provided with the adhesive (333); - aligning (S33) the microlens arrangement (330) relative to the focusing elements (31); - curing (S34) the adhesive (333).