Device with interference light suppressing function

Abstract

The invention relates to a device having an optical unit (3) having at least one inner wall (35) provided with a surface structure (351). The surface structure (351) has cavities (352). Such a device is advantageous for use in head-up displays with suppression of disturbing light.

Description

Technical Field

[0001] This invention relates to a device with interference light suppression function, and more particularly to a head-up display (HUD) for generating virtual images on the windshield of a motor vehicle. A head-up display (HUD) is a display system in which an observer can keep their gaze directed towards the direction of travel because the content to be displayed is brought into their field of vision. Such systems, due to their complexity and cost, were initially used primarily in the aviation field, but are now also being mass-produced and installed in the automotive sector. Background Technology

[0002] Head-up displays (HUDs) typically consist of an imaging unit or image generating unit (PGU), an optical unit, and a mirror unit. The imaging unit generates an image using at least one display element. Modern HUDs generally use matrix displays or scanning imagers to generate images. The display can be, for example, an LC display (Liquid Crystal), a µ-LED display (Light Emitting Diode), an LCoS display (Liquid Crystal on Silicon), or a DMD system (Digital Micromirror Device). The scanning system is, for example, a laser scanning system. The optical unit guides the image onto the mirror unit. The mirror unit is a partially reflective, transparent glass. Thus, the observer sees the content displayed by the imaging unit as a virtual image and simultaneously sees the real world behind the glass. In the automotive industry, the windshield can also be used as a mirror unit, its curved shape being taken into account during the display, for example, through pre-distortion correction of the image displayed by the imaging unit. Through the coordinated action of the optical unit and the mirror unit, the virtual image is a magnified and distorted image of the image generated by the imaging unit.

[0003] Viewers can only view the virtual image on the head-up display from the so-called eye-tracking range. The eye-tracking range refers to the area within which the eye's position, both in height and width, allows the viewer to see the HUD image. As long as one eye is within the eye-tracking range, that eye can see all elements of the virtual image. If one or both eyes are outside the eye-tracking range, the virtual image can only be partially seen or not seen at all by the viewer. Therefore, the larger the eye-tracking range, the fewer restrictions the viewer faces in choosing their viewing position, which is in turn influenced by their seating position.

[0004] The optical unit of a head-up display typically includes multiple mirrors to achieve optical imaging at a desired virtual distance, together with additional mirror elements on the windshield. Light emitted from the imaging unit is reflected by folded mirrors (which can be flat or curved) onto a curved primary mirror, which then reflects it toward the windshield. Currently used curved mirrors are implemented as essentially flat plates with a large curvature, depending on the desired optical function. Such curved mirrors are manufactured, for example, by injection molding or compression molding of plastics, or by gravity bending or extrusion bending of glass.

[0005] Light reflections (interference light) in a display system can be superimposed on the light (useful light) emitted by the display, thus affecting its readability. Interference light reflection is caused by one or more deflections of uncontrollable interference light (such as sunlight, which is particularly bright and may cause interference). Here, deflection can occur not only through specular reflection (where the angle of exit equals the angle of incidence) but also through diffuse reflection (where the angle of exit is independent of the angle of incidence).

[0006] Known methods to avoid interfering with light reflection include:

[0007] A) Geometric reflection suppression: By using surface tilt or curvature, reflections are redirected, preventing them from reaching the viewer's field of vision or eye movement range.

[0008] B) Reflection suppression through extinction: Here, extinction is performed on the surface by an appropriate method, wherein enhanced absorption combined with diffuse diffusion reduces the intensity of interfering reflections.

[0009] C) Reflection suppression through a transparent interference layer:

[0010] Here, the reflection of the incident beam is suppressed by destructive interference through the stacking of thin layers on a transparent material.

[0011] D) Reflection suppression through a transparent micro-optical layer: Here, a planar cover glass with a partially transparent micro-optical structure is provided on the backlight display, which redistributes interfering light through light refraction.

[0012] A known implementation of method A) is a curved cover glass for a display (e.g., a dashboard or head-up display). However, so-called jalousie-Folien films also utilize geometric suppression of interfering light associated with the useful light.

[0013] There are many known implementations of method B), and all types of absorbent and / or rough surfaces are known here. Black-coated surfaces function primarily through absorption, as are moth-eye structures and other textured surfaces.

[0014] Method C) is known to be used in display systems, for example as an anti-reflective coating on TFT displays, and is also well known from commercially available visual aids, camera lenses, and telescopes.

[0015] In addition, there are combined applications of methods A) and B), such as ribbed, additionally coated, or textured baffles. Roughened and matte Venetian blind films (privacy films) are also common, and methods A) and B) are used. For transparent surfaces, methods A) and B) are sometimes combined with C).

[0016] The problems with existing technologies include: A) Geometric reflection suppression: If only partially effective in diffuse surfaces, surface orientation is required, necessitating additional mounting space. Furthermore, the spatial arrangement may limit display functionality (e.g., viewing angle). B) Reflection suppression through extinction: Either only partially effective or extremely complex, resulting in high cost. C) Reflection suppression through transparent interference layers: Complex to manufacture, with costs increasing with the required quality; applications are limited to specific material surfaces. D) Transparent optical microstructures on displays must be manufactured with high precision, thus requiring complexity, to avoid interfering side effects (e.g., moiré fringes).

[0017] US Patent document US 2020 / 0371352 A1 relates to reflection reduction in HUDs and mentions surface structures on the faces inside the HUD. The prismatic ribs and pyramids (also described in the text as structures with polygonal bases) mentioned therein have mutually inclined planes. Disadvantageously, because they act as a "mirror" for the specular reflection component in scattered light, a bright surface can be created as long as the planes between the interfering light source and the observer are at a suitable angle.

[0018] Patent document US 2011 / 0051251 A1 relates to an optical element with anti-reflective properties and shows a structure with a spherical or even flat surface as a surface structure, which is disadvantageous because they act as a “mirror” for the specular reflection component of scattered light, thus forming a bright surface as long as the surface between the interfering light source and the observer is at the right angle.

[0019] The limitation of existing solutions lies in the fact that true reflection is composed of both diffuse and specular reflection, resulting in poor reflection reduction effects from the geometry designed for the specular portion. Additional coatings reduce all components, so in principle, this doesn't change anything. This geometry primarily works under conditions of gentle light incidence. Furthermore, the upper edges of the ridges additionally backscatter light, while the valleys absorb more light, creating an intrusive pattern of light and dark stripes. Improvements are desired, particularly to avoid the side effect of "striped patterns appearing in the field of view." Summary of the Invention

[0020] The purpose of this invention is to modify the surface of the opaque component built into the mirror optical system of a head-up display (HUD) so that diffuse backscattering of sunlight does not cause interfering glare in the driver's field of vision. To this end, it is necessary to manufacture a housing component with a surface that does not reflect any scattered light and therefore appears deep black. This housing component can be used not only for displays but also in any application where effective suppression of interfering light is required.

[0021] The device according to the invention has an optical unit having at least one internal wall with a surface structure, characterized in that the surface structure has a cavity / chamber / recess. According to the invention, a planar structure is proposed that effectively suppresses real scattered light composed of specular scattered light and diffuse scattered light. Advantageously, the planar structure has a cavity into which interfering light can enter.

[0022] Advantageously, pins or strips are arranged between these cavities. Thus, the cavities are formed by pins and / or strips. The pins and / or strips form the upper side of the component, which is opposite to the wall, interrupted by the cavity, and faces the interfering light. When there are many cavities per unit area, this upper side has an approximately uniform appearance.

[0023] Advantageously, the pins and / or strips are arranged on the wall on one hand, and on the other hand, their upper side facing away from the wall does not have a plane parallel to the wall. This minimizes the possibility of interfering light being mirror-reflected towards the observer from the upper side of the component.

[0024] Advantageously, the cavity formed by the pins and / or strips has an upper opening parallel to the wall and a height perpendicular to the wall, wherein the ratio of height to average opening width is 1:2 or greater. This ensures that the sides of the pins and / or strips are inclined at an average angle greater than 45° relative to the wall or upper side. For example, when the ratio of height to opening width is 1:1, the average inclination of the sides relative to the surface normal is 27°. This "steep" side minimizes the possibility of interfering light being reflected back towards the observer at these sides in the manner of single specular reflection or diffuse reflection.

[0025] Advantageously, the cavity has an irregularly shaped cross-section. This largely prevents interfering light, which enters the cavity at an angle through the upper opening, from being reflected back by the mirror and immediately re-emitted. Instead, the interfering light is scattered preferentially away from the incident direction on the irregular sides of the cavity.

[0026] Advantageously, the sides of the cavity and / or the pins and / or strips have uneven boundary surfaces. These uneven boundary surfaces can preferably be produced using a 3D printing process, which automatically forms the uneven boundary surfaces due to the minimum possible size of the 3D printing material volume. The random unevenness of the boundary surfaces further reduces the probability that interfering light will leave the cavity towards the observer after only a few specular and / or diffuse reflections. Here, "random unevenness" refers to a structural dimension that is several times the wavelength of the light contained in the interfering light spectrum.

[0027] Advantageously, the sides and / or pins and / or strips of the cavity have broadband light-absorbing surfaces. The higher the degree of broadband spectral absorption of the interfering light, the faster the intensity of the interfering light component that is repeatedly specularly or diffusely reflected within the cavity attenuates.

[0028] Advantageous design options that can be used individually or in combination include:

[0029] a) The cavity has a variable cross-section.

[0030] b) The sides of the cavity have no smooth boundary surfaces.

[0031] c) The pin or strip does not have a plane on its upper side that is parallel to the bottom surface.

[0032] d) Pins or strips and a bottom surface with a wide-bandgap light-absorbing surface.

[0033] e) The ratio of the structural height of the cavity to the average width of its upper opening is at least 1:2.

[0034] Advantageously, the pin is configured as a pointed cone with a circular base. The problem of a surface acting as a "mirror" for the specular reflection component of interfering light and thus producing a bright surface when the interfering light source and the observer are at the appropriate angle does not exist in the pointed cone with a circular base according to the invention.

[0035] Preferably, the pin has a checkerboard-shaped cone shape with a pointed tip. The checkerboard cone here does not have a spherical apex, but rather a pointed tip. The pointed shape reduces specular reflection. The recess between the lower part of the tip and the neck of the checkerboard cone increases the likelihood that upward-pointing light will be absorbed at the recess, thereby improving the suppression of interfering light. Towards the lower part, adjacent cones gradually narrow the cavity in such a way that the lower wall between the closely arranged cones has only a plane with a minimum normal pointing towards the upper opening of the cavity. Also advantageously, the remaining plane between the cones is curved to suppress direct reflection in the case of perpendicular incident interfering light.

[0036] Advantageously, the pins or strips are made of rigid materials. This has the advantage that they are not easily bent or otherwise deformed, thus maintaining their light-absorbing properties even under adverse conditions. Suitable materials include plastics such as polycarbonate (typical values: elastic modulus 2.4 GPa and tensile strength 65 MPa) or polyamide (typical values: elastic modulus 1.9 GPa and tensile strength 50 MPa).

[0037] Advantageously, the pins and / or strips are made of materials that can be introduced via additive manufacturing, where the smallest possible volumetric units formed additively do not combine to form a smooth surface, but rather further contribute to surface roughness. For example, in some 3D printing processes, polyamides are used to form fine granular structures on a surface by stacking the smallest volumetric units.

[0038] The head-up display according to the invention has a structured wall in the device according to the invention. This achieves effective suppression of interfering light.

[0039] The interference light suppression method according to the present invention is significantly superior to coated and / or textured surfaces in terms of interference light absorption. The gloss is particularly low, and the surface implemented according to the present invention presents a deep black color. Even under bright sunlight as interference light, a completely matte (dull) and color-neutral dark (almost black) appearance can be achieved.

[0040] This invention also relates to the suppression of interfering light in all types of lighting equipment or rooms. Attached Figure Description

[0041] Other advantages and design schemes of the present invention will be further described below with reference to the accompanying drawings. Wherein:

[0042] Figure 1 A head-up display for a vehicle is shown;

[0043] Figure 2 This shows a view taken from inside a motor vehicle, looking out through the windshield.

[0044] Figure 3 The walls of the optical unit are shown in cross-section;

[0045] Figure 4 This illustrates the relationship between actual reflection, specular reflection, and diffuse reflection.

[0046] Figure 5 This shows a magnified section of a textured wall;

[0047] Figure 6 Several surface structures according to the present invention are shown;

[0048] Figure 7Different pin examples are shown in different side views and cross-sectional views;

[0049] Figure 8 An example of a mesh with tubular elements is shown; and

[0050] Figure 9-15 Other advantageous surface structures are shown. Detailed Implementation

[0051] To better understand the principles of the present invention, embodiments thereof are described in more detail below with the aid of the accompanying drawings. The same reference numerals are used in the drawings for the same or equivalent elements, and it is not necessary to re-describe each drawing. It should be understood that the present invention is not limited to the illustrated embodiments, and the described features may be combined or modified without departing from the scope of protection defined in the appended claims.

[0052] Figure 1 A head-up display (HUD) is schematically shown as an example of an image generation system 1 for a vehicle. The HUD has an imaging unit 2, an optical unit 3, and a mirror unit 4. A beam SB1 is emitted from a projection surface 21 and reflected by a first mirror 31 onto a curved mirror 32, which reflects the beam toward the mirror unit 4. The mirror unit 4 is shown here as the windshield 41 of a motor vehicle. A beam SB2 is transmitted from the mirror unit toward the observer's eye 61.

[0053] An observer sees a virtual image VB, located above the hood of the vehicle or even in front of it. Through the combined action of optical and mirror units, the virtual image is a magnified view of the image from projection surface 21. Speed ​​limits, current vehicle speed, and navigation instructions are symbolically indicated here. All elements of the virtual image can be seen by eye 61 as long as it is within the eye movement range 62, indicated by the rectangle. If eye 61 is outside the eye movement range 62, the virtual image VB is only partially visible or even invisible to the observer. The larger the eye movement range 62, the fewer restrictions the observer faces when choosing their seating position. The curvature of the curved mirror 32 matches the curvature of the windshield 41, ensuring maximum stability of image distortion across the entire eye movement range 62. The curved mirror 32 is rotatably supported by a support 321. This rotation of the curved mirror 32 allows the eye movement range 62 to be moved, thereby aligning the position of the eye movement range 62 with the position of the eye 61. The first mirror 31 is used to make the path of the beam SB1 between the projection surface 21 and the curved mirror 32 long, while the optical unit 3 remains compact. A transparent cover 33 isolates the optical unit 3 from the surrounding environment. This protects the optical elements of the optical unit 3 from dust, for example, within the interior space of the vehicle. A light shield 34 reliably absorbs light reflected from the boundary surface of the cover 33, thus preventing glare for the observer. Light from other interfering light sources 16, besides sunlight SL, may also be transmitted to the projection surface 11. The optical unit 3 has at least one wall 35 with a surface structure 351. The position, size, and shape of the wall 35 are shown schematically as an example only. Interfering light SL' (which does not enter the optical unit 3 within the angular range of the beam SB1 but still causes visible interference reflections) is affected by the surface structure 351, making these interference reflections as inconspicuous as possible, and ideally even completely avoidable. If the interference light SL' is located outside the position shown in the figure, it may originate from the sun or other interfering light sources 64.

[0054] Figure 2The view seen from inside the vehicle through the windshield 41 is shown. A black printed area 411 is visible in the lower part of the windshield. A cover 42 is located between the windshield 41 and the observer. The lower part of the left A-pillar 43 is visible on the far left. A rearview mirror 421 is arranged in the upper part of the windshield. The observer and eye movement range 62 are visible in its reflection. Through the windshield, the observer can see the road and surrounding environment in front of the vehicle. The virtual image VB appears to be located on the road. An interference reflection SR is schematically marked above the virtual image VB. It has a striped structure caused by the ribbed surface structure 351 of the wall 35 of the optical unit 3. Even though the interference reflection SR shown here is located above the road, it can still cause distraction to the observer. If the interference reflection is located inside or near the virtual image VB, it is even more distracting.

[0055] Figure 3 One implementation of method A) + B) is shown in cross-sectional view: Here, wall 35 is the inner baffle of the HUD. Wall 35 is designed as a component with linear ridges and a black coating. Therefore, the surface structure 351 consists of linear ridges arranged substantially parallel to each other. This improves diffuse backscattering from the inner baffle into the observer's field of view. As interferometric reflections SR, only slight linear textures are visible as bright and dark fringes, and they hardly constitute interference in the edge regions of the virtual image VB visible to the observer. It is desirable to obtain a surface of wall 35 (inner baffle) whose suppression of diffuse backscattering is comparable to that of texture, but does not produce perceptible interfering reflections in the regions of the virtual image VB in the case of solar incidence or other strong interfering light SL'.

[0056] Figure 4 The actual reflection R is schematically shown. real R by mirror reflection spek and diffuse reflection R diff Composition. In specular reflection R spek In the middle, the interfering light SL' from the interfering light source 64 reaches the surface 350 and is reflected there according to the rule that "the angle of incidence equals the angle of reflection". The specularly reflected light is almost entirely the specularly reflected interfering light SL. spek Transmitted to the observer's eye 61. In diffuse reflection R diff In the process, the interfering light SL' from the interfering light source 64 is transmitted to surface 350 and diffusely scattered there. The diffusely reflected light is distributed in almost all solid angle directions. Only a small portion of it serves as diffuse interfering light SL. diff Transmitted to the viewer's eyes 61. Actual interference light SL real The angular distribution WV is affected by the interfering light SL due to mirror reflection. spek and diffuse interference light SL diffThe angular distribution is as shown on the right side of the figure. The angular distribution WV depends on the specular and diffuse reflection characteristics of the surface at 35°.

[0057] Figure 5 Showing from Figure 3 A magnified partial view of the wall 35, whose surface structure 351 is textured. Interference light SL', incident relatively steeply from the upper right, is visible and reflected on surface 350. The actual angular distribution WV of the reflected light is also shown. It can be seen that the peak of the angular distribution WV strikes the adjacent surface roughly perpendicularly, with part of it being absorbed and another part reflected in non-critical directions. A portion of the angular distribution strikes the curve of surface 350 and is reflected in many different directions. A portion of this results in the undesirable interference reflection SR.

[0058] The reason for the light and dark stripes in the interfering reflection SR caused by texture is that, for a given solar incidence (direction), each linear raised structure (ridge) produces light reflection (bright stripes) along the ridges of surface structure 351 and higher light absorption (dark stripes) along the valleys between them. This stripe arrangement (light and dark stripes) is clearly perceptible as interfering light / interfering reflection SR and is undesirable.

[0059] Figure 6Multiple surface structures 351 according to the present invention are shown. A surface with a cone-pin surface structure is visible in the upper left corner. Multiple cones 50 of different sizes are arranged as a type of pin 5 on the surface 350 of the wall 35. For simplicity, the cones 50 are shown here in a two-dimensional manner. However, in reality, three-dimensional cones 50 are involved here. The space between the cones 50 forms a cavity 352 in which light is reflected multiple times and its intensity is reduced due to absorption at each reflection. It can be seen that the cones 50 do not have a plane parallel to the wall 35. It can also be seen that the cavity 352 has a varying cross-section when approached perpendicularly to the wall 35. A surface with a checkerboard-shaped pin surface structure is visible in the upper right corner. Multiple checkerboard-shaped pins 51 are arranged as a type of pin 5 on the surface 350 of the wall 35. Here, for simplicity, they are also shown in a two-dimensional manner. Furthermore, the checkerboard-shaped pins 51 are only fully shown at the edges of the shown surface 350, and only the heads 511 of the pins 51 are shown in the middle of the shown surface. Here, the space between the checkerboard-shaped pins 51 also forms cavities 352, in which light is attenuated. A mesh grid is visible in the lower part of the diagram. In the lower left, an irregular surface structure 351 with spatially arranged horizontal bars 70 (which are a type of bar 7) can be seen. Cavities 352 are also visible between the horizontal bars 70 of the surface structure 351. Due to the irregular surface structure 351, these cavities 352 have irregular sizes and shapes. The surface structure 351 does not have a plane, and therefore there is no plane parallel to the wall 35 (not shown). In the lower right, a regular surface structure 351 composed of spatially interwoven tubular elements 71 (which are another type of bar 7) can be seen. Cavities 352 are also visible between the tubular elements 71 of the surface structure 351.

[0060] The effect of these alternatives according to the invention is that they effectively suppress actual scattered light (= specular reflection + diffuse scattering) in planar structures. They have:

[0061] a) Cavity 352, interfering light can enter it;

[0062] b) Pins 5 or strips 7 located between these cavities 352.

[0063] at the same time

[0064] a) Cavity 352 has a varying cross-section, and / or

[0065] b) Cavity 352 does not have any flat boundary surfaces on its sides, and / or

[0066] c) Pin 5 or strip 7 does not have any plane on its upper side parallel to the bottom surface of wall 35, and / or

[0067] d) The bottom surface of pin 5 or strip 7 and wall 35 has a broadband light-absorbing surface 350, and / or

[0068] e) The ratio of the average structural height to the average opening width of cavity 352 is 1:2 or greater.

[0069] It has been proven that the planar arrangement of the rounded top pins 511, also known as checkerboard pin plate, in which checkerboard pins 51 are arranged on surface 350, and if the surface is painted black with low-cost acrylic, the light absorption effect obtained is comparable to that of components painted with high-strength, expensive black dye. If the checkerboard pins 51 are replaced with pointed cones 50, the brightness of the scattered light will be further reduced significantly.

[0070] The present invention proposes a cavity 352 with a varying cross-section. A key feature is the presence of one or more contractions where the cross-section of the cavity 352 has a minimum value along its vertical extension. For example, in an arrangement of checkerboard pins, one contraction is located between the top 511s, while a second contraction is located at the bottom of the checkerboard pins 51. Furthermore, where adjacent checkerboard pins contact each other, the cavity narrows sharply towards the wall. Where adjacent checkerboard pins do not directly contact each other, the cavity is defined by the wall with the remaining flat surface. However, it can also be advantageously designed in a curved manner to further suppress interfering light that is vertically incident and re-emitted.

[0071] The grid does not have to be a square; it can also be a rectangle or a more complex woven structure. Figure 6 The lower regular and irregular mesh grids also have cavities 352 with constricted sections. Due to the tubular shape, the upper side (i.e., the side facing the scattered light) is less likely to experience specular reflection than the upper side of a sphere.

[0072] All mesh grids are characterized by varying cavities 352 formed from long-fiber fabrics, such as crossbars 70 or tubular elements 71. It should also be noted that spatial grid structures such as nickel foam (used for battery electrodes) also meet these characteristics (cavities 352, variable cross-sections, contractions, etc.), and they function well when implemented in black.

[0073] Figure 7 Various examples of pin 5 are shown in side and sectional (top) views. In the side view, from left to right, the top row of R1 shows: a large checker-shaped pin 51, a small checker-shaped pin 51, a large cone 50, a small cone 50, a checker-shaped pin 512 with a pointed top, stacked cones 520 and 521 (which form a Christmas tree 52 with multiple layers), and arrow 53 (similar to a Christmas tree with a trunk). Below this are the corresponding cross-sectional variations: the second row of R2 from the top is "circular", the third row of R3 from the top is "elliptical", and the bottom row of R4 is "free-form cross-section".

[0074] The drawback of the checkerboard pin 51 is the spherical upper side of the head 511. Here, light from the diffused light source will always be reflected directly to the observer by specular reflection, although it will only appear as a small area or point. This can be avoided by using a checkerboard pin 51 with an added "pointed tip" 512. Here, the "Christmas tree" 52 and the arrow tip 53, i.e., the pointed cone on the trunk (or the second / third pointed cones 520, 521, 52n), are also solutions to meet the requirement of "a cavity 352 with one or more contractions".

[0075] As can be seen, in all the structures shown (pin 5 in this case), the structural width STB is less than its structural height STH. This structural height is also the height of the cavity formed between these structures. When the structures are arranged closely together, the opening width of these cavities is as follows: Figure 6 The values ​​shown are within the range of the structural width STB. The ratio of the structural height STH to the structural width STB (equal to the opening width when the cavities are closely arranged) satisfies STH / STB > 1.5. In the example shown here, this ratio is approximately 2.

[0076] Figure 8 An exemplary grid with tubular elements 71 in row R1 is shown above in a top oblique top view. Different cross-sections of the tubular elements 71 are shown below: circular in row R2, elliptical in row R3, and free-form curve in row R4. It can also be seen here that the ratio of structural height STH to structural width STB is STH / STB > 1.5.

[0077] Figure 9 Other advantageous surface structures with different examples of pins 5 are shown in cross-sectional view. In the upper left corner, checkerboard-shaped pins 51 with finials 512 are arranged adjacent to each other at different sizes. Above and in the center is a Christmas tree 52 with three layers of cones 520, 521, and 522, arranged adjacent to each other at different sizes. In the upper right corner, cones 50 of different sizes are arranged adjacent to each other.

[0078] Figure 10 An example is shown with three checkerboard-shaped pins 51, each with a pointed top 512. They have the same structural width STB and structural height STH. The cavity 352 formed between them has an opening width OW, which approximately corresponds to the structural width STB. In this figure, the ratio of structural height STH to opening width OW is approximately 2:1.

[0079] Figure 11An example is shown of three checkerboard-shaped pins 51 with apexes 512, identical to those in the previous figure. They have the same structural width STB and structural height STH. The cavity 352 formed between them has an opening width OW, which approximately corresponds to the structural width STB. In this figure, the ratio of structural height STH to opening width OW is approximately 3:1. It can be seen that the sides 5121 of the apexes 512 are quite steep. Therefore, most of the light incident from the outside of the cavity 352 is reflected into the cavity. Thus, only a very small portion of the light incident from the outside via the opening width will leave the cavity 352 directly or after only a few reflections.

[0080] Figure 12 Three checkerboard-shaped pins 51 with pointed tops 512, identical to those in the previous figure, are shown as an example. The ratio of the structural height STH to the opening width OW in this figure is approximately 1:1. It can be seen that the sides 5121 of the pointed tops 512 are gentler than those in the previous figure. Nevertheless, only a small amount of light incident from the outside through the opening width will leave the corresponding cavity directly or after only a few reflections.

[0081] Figure 13 Three checkerboard-shaped pins 51 with pointed tops 512, identical to those in the previous figure, are shown as an example. In this figure, the ratio of the structural height STH to the opening width OW is approximately 1:2. It can be seen that the sides of the pointed tops are gentler than those in the previous figure. Nevertheless, only a relatively small amount of light incident from the outside through the opening width will leave the corresponding cavity directly or after only a few reflections.

[0082] Figure 14 Three checkerboard-shaped pins 51 with pointed tops 512, identical to those in the previous figure, are shown as an example. Here, the checkerboard-shaped pins are spaced apart in their bottom regions. Therefore, the opening width OW has a larger value than the structural width STB. As can be seen in the dashed area, there is a flat region on the upper side of the wall 35. Most of the light that shines directly onto these regions is reflected back to the wall region of the cavity 352, and thus is mostly absorbed inside the cavity.

[0083] Figure 15 Three checkerboard-shaped pins 51 with pointed tops 512, identical to those in the previous figure, are shown. Here, these checkerboard-shaped pins are spaced apart in their bottom regions. However, the checkerboard-shaped pins 51 have rounded bases 513. Therefore, the opening width OW again has approximately the same value as the structural width STB. As can be seen in the area marked by the dashed line, there is no planar area on the upper side of the wall 35. Therefore, less light incident from the outside through the opening width OW leaves the corresponding cavity directly or after only a few reflections.

[0084] According to the present invention, instead of using "pins" 5 of only a single size in a regular arrangement, multiple sizes of "pins" are placed in a mixed arrangement. This ensures the variable cavity 352 and the contraction section.

[0085] exist Figure 9 The lower region shows a possible scheme for the branching structure 54, namely a multi-level "pin" 5 with branches 541 and 542. The final result is a "forest" composed of the "pins" 5 and the "cavities" 352 located between them, which function similarly to a real forest of trees, "swallowing" light as much as possible.

[0086] The proposed arrangement of cavity 352 refers to a volumetric / three-dimensional spatial structure, which necessarily has a certain thickness. However, its thickness may decrease as the dimensions of each structure (pin 5, strip 7, etc.) decrease. This is initially disadvantageous for "thin" coatings (such as embossing or painting). However, when the scale is reduced and the number of structures per unit area is increased, a practical material thickness can be achieved.

[0087] Before the advent of additive manufacturing, the arrangement of the cavity 352 according to the present invention was very complex to manufacture because it could not be demolded from a linearly moving mold (one-time molds were extremely expensive). The inventors discovered that these could be achieved more easily in the future using additive manufacturing processes.

[0088] The solution according to the invention takes into account the fact that the reflection of scattered light has both diffuse and specular reflection. According to the invention, direct specular reflection as well as multi-level, randomly ordered specular and diffuse reflection towards the observer can be prevented. The cavity 352 with a contraction section according to the invention is superior in this respect to all linearly demoldable surfaces.

[0089] The cavity 352 with the contraction section functions similarly to a fish trap: light can easily enter but not easily escape. Even if the substrate surface is not particularly matte on a microscopic scale, a simple coating or coloring can achieve an extremely effective "light-absorbing" effect.

[0090] The results show that a better blackness can actually be achieved. Even the checkerboard pin 51, coated with a light matte finish (such as acrylic black paint from the building materials market), achieves a result comparable to various high-performance matte paints or textured surfaces. Measurements also show that the cone 50, Christmas tree 52, and arrowhead 53 are even "darker".

[0091] Another advantage of the solution of this invention lies in its appearance. The proposed structure appears "homogeneous" when viewed macroscopically (at a certain distance), which contrasts with the prism-shaped ribs (which, as coarse light traps, produce a striped image in the field of view).

[0092] Planar geometries such as prismatic ribs and pyramids are geometrically easy to design and manufacture, but they have drawbacks due to the direct specular reflection they produce. These structures are primarily suitable for arrangements where the geometry of the interfering light source is fixed relative to the observer. However, in the application of head-up display housings, the sun as the primary interfering light source does not fit this scenario. The sun shines here and there, vehicles are in motion, and the sun moves throughout the day; both are viewed from the fixed reference system of Earth.

[0093] Furthermore, the sun is an exceptionally bright source of interference. Under favorable weather / daytime conditions, its brightness can reach 1.6 Giga cd / m². 2 Therefore, it is very difficult to make the surface appear extremely dark under sunlight. The light provided by the sun is so intense that even with multiple levels of specular reflection and / or diffuse reflection, it can still appear as very glaring interference light relative to the useful light. The inventors point out that if the cavity 352 according to the invention is provided, good results can still be obtained despite the presence of specular reflection and / or diffuse reflection.

Claims

1. A device having an optical unit (3), said optical unit having at least one internal wall (35) having a surface structure (351), characterized in that, The surface structure (351) has a cavity (352).

2. The apparatus according to claim 1, characterized in that, The cavity (352) is formed by pins (5, 50, 51, 52, 53) and / or strips (7, 70, 71).

3. The apparatus according to claim 2, characterized in that, The pins (5, 50, 51, 52, 53) and / or strips (7, 70, 71) are arranged on the wall (35) on one hand, and on the other hand, they do not have a plane parallel to the wall on their upper side away from the wall (35).

4. The apparatus according to any one of claims 2 to 3, characterized in that, The cavity (352) formed by the pins (5, 50, 51, 52, 53) and / or strips (7, 70, 71) has an average opening width (OW) parallel to the surface of the wall (35) and a height (STH) perpendicular to the surface of the wall (35), the ratio of height (STH) to opening width (OW) having a value of 0.5 or greater.

5. The apparatus according to any one of the preceding claims, characterized in that, The cavity (352) has an irregularly shaped cross-section.

6. The apparatus according to any one of the preceding claims, characterized in that, The sides of the cavity (352) and / or pins (5, 50, 51, 52, 53) and / or strips (7, 70, 71) have uneven boundary surfaces.

7. The apparatus according to any one of the preceding claims, characterized in that, The sides of the cavity (352) and / or pins (5, 50, 51, 52, 53) and / or strips (7, 70, 71) have broadband light-absorbing surfaces.

8. The apparatus according to any one of the preceding claims, characterized in that, The cavity (352) has no flat surface at its deepest point facing the wall (35).

9. The apparatus according to any one of claims 2 to 8, characterized in that, The pin is a pointed cone (50) with a circular base.

10. The apparatus according to any one of claims 2 to 8, characterized in that, The pin has the shape of a checkerboard pin (51) with a pointed tip (512).

11. The apparatus according to any one of claims 2 to 10, characterized in that, The pins (5, 50, 51, 52, 53) and / or the strips (7, 70, 71) are made of rigid material.

12. The apparatus according to any one of claims 2 to 11, characterized in that, The pins (5, 50, 51, 52, 53) and / or the strips (7, 70, 71) are made of materials that can be applied by an additive process, wherein the smallest possible volume units formed by additive processing do not combine to form a smooth surface, but further form a surface roughness.

13. A head-up display comprising the means according to any one of the preceding claims.

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