Abstract
A mirror for a head-up display, in particular for a head-up display for transportation is disclosed. A head-up display comprising such a mirror is also disclosed. The mirror has a base body with a planar region and a rib arranged at a periphery of the planar region. A mirror layer is arranged on the planar region wherein the rib has an anti-reflective structure.
Claims
1. A mirror for a head-up display, comprising: a base body with a planar region and a rib arranged at a periphery of the planar region; and a mirror layer arranged on the planar region, wherein the rib has an anti-reflective structure.
2. The mirror as claimed in claim 1, wherein the rib is designed as a circumferential rib.
3. The mirror as claimed in claim 1, wherein the rib is inclined relative to a mirror axis of the mirror.
4. The mirror as claimed in claim 1, wherein the anti-reflective structure is manufactured by laser structuring or sandblasting.
5. The mirror as claimed in claim 1, wherein the mirror layer is formed by a coating applied to the base body r by a mirror element placed onto the base body.
6. The mirror as claimed in claim 1, wherein a thickness of the planar region or of the rib is less than 3.5 mm.
7. The mirror as claimed in claim 1, wherein the base body is manufactured by means of injection molding or injection compression molding with a hot runner film gate.
8. The mirror as claimed in claim 7, wherein a compression ram used in injection molding has in the region of a transition between the planar region and the rib a geometry which is designed to compensate for a shape deviation due to volume loss during cooling of the base body.
9. A head-up display for transportation, comprising a mirror comprising: a base body with a planar region and a rib arranged at a periphery of the planar region; and a mirror layer arranged on the planar region, wherein the rib has an anti-reflective structure.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Further features of the present disclosure will be evident from the following description and the appended claims in conjunction with the figures, wherein:
[0022] FIG. 1 schematically shows a head-up display according to the prior art for a motor vehicle;
[0023] FIG. 2 schematically shows a mirror according to the prior art for a head-up display;
[0024] FIG. 3 schematically shows a mirror according to the disclosure for a head-up display;
[0025] FIG. 4 illustrates the production of a mirror according to the disclosure by injection compression molding;
[0026] FIG. 5 schematically shows a pre-deformation of a compression ram for compensating shape changes; and
[0027] FIG. 6 schematically shows an anti-reflective structure introduced into a rib of the mirror.
DETAILED DESCRIPTION
[0028] For a better understanding of the principles of the present disclosure, embodiments of the disclosure will be explained in more detail below with the aid of the figures. The same references are used in the figures for identical or functionally identical elements and are not necessarily described again for each figure. It is understood that the disclosure is not limited to the illustrated embodiments and that the described features may also be combined or modified without departing from the scope of protection of the disclosure as defined in the appended claims.
[0029] FIG. 1 shows a schematic diagram of a conventional head-up display for a motor vehicle. The head-up display has a display apparatus 1 with a picture generating unit 10 and an optical unit 12. A beam SB1 emanates from a display element 11 and is reflected by a folding mirror 21 onto a curved mirror 22 that reflects it in the direction of a mirror unit 2. The mirror unit 2 is illustrated here as a windshield 20 of the motor vehicle. From there, the beam SB2 travels in the direction of an eye of a viewer 3.
[0030] The viewer 3 sees a virtual image VB that is located outside the motor vehicle, above the engine hood or even in front of the motor vehicle. Due to the interaction between the optical unit 12 and the mirror unit 2, the virtual image VB is an enlarged representation of the image displayed by the display element 11. A speed limit, the current vehicle speed and navigation instructions are symbolically represented here. As long as the eye of the viewer 3 is located within an eyebox 4, indicated by a rectangle, all elements of the virtual image VB are visible to the user 3. If the eye of the viewer 3 is located outside of the eyebox 4, the virtual image VB is only partially visible to the user 3 or not at all. The larger the eyebox 4 is, the less restricted the viewer is when choosing their seating position.
[0031] The curvature of the curved mirror 22 is adapted to the curvature of the windshield 20 and ensures that the image distortion is stable over the entire eyebox 4. The curved mirror 22 is rotatably mounted by a bearing 23. The rotation of the curved mirror 22 that this allows makes it possible to shift the eyebox 4 and thus to adapt the position of the eyebox 4 to the position of the viewer 3. The folding mirror 21 serves to ensure that the path traveled by the beam SB1 between the display element 11 and the curved mirror 22 is long and, at the same time, that the optical unit 12 is nevertheless compact. The picture generating unit 10 and the optical unit 12 are separated from the environment by a housing 13 having a transparent cover plate 24. The optical elements of the optical unit 12 are thus protected, for example against dust inside the vehicle. An optical film or a polarizer 25 may furthermore be located on the cover plate 24. The display element 11 is typically polarized, and the mirror unit 2 acts like an analyzer. The purpose of the polarizer 25 is therefore to influence the polarization in order to achieve uniform visibility of the useful light. A cover arrangement 26 arranged on the cover plate 24 serves to reliably absorb the light reflected via the interface of the cover plate 24 so that the viewer is not dazzled. In addition to sunlight SL, the light from another stray light source 5 may also reach the display element 11. In combination with a polarization filter, the polarizer 25 may additionally also be used to reduce incident sunlight SL.
[0032] FIG. 2 schematically shows a mirror 22 according to the prior art for a head-up display. FIG. 2a) shows a side view, and FIG. 2b) shows a top view. The mirror 22 has a base body 220, which comprises merely a planar region 221. A mirror layer 224 is arranged on the planar region 221. The mirror 22 is thus designed in the form of a substantially flat plate having a large curvature corresponding to the desired optical function. For example, the mirror 22 may be produced by injection molding or injection compression molding a transparent thermoplastic, e.g., COC (cyclic olefin copolymer). To ensure sufficient flexural rigidity, currently used mirrors 22 have a thickness of greater than or equal to 5 mm. This results in extended cycle times and high material costs. In addition, the components are filled via a wide sprue, which must then be milled off. This requires an additional work step.
[0033] FIG. 3 schematically shows a mirror 22 according to the disclosure for a head-up display. FIG. 3a) shows a side view, and FIG. 3b) shows a top view. The mirror 23 has a base body 220, which has a rib 223 in addition to a planar region 221. The rib 223 is arranged at a periphery 222 of the planar region 221. In the example shown, the rib 223 is designed to extend around the planar region 221, i.e., the base body 220 is designed like a pan or a trough. However, it is likewise possible that the base body 220 has a rib 223 only at some of its periphery. For example, in a rectangular mirror 22, a rib 223 may be formed only on each of the long sides. This rib 223 causes an increased flexural rigidity, so that the mirror 22 becomes much less sensitive to mechanical influences. This allows the material thickness to be reduced and thus also the material costs and the required cycle time. Preferably, the thickness of the planar region 221 is less than or equal to 3.5 mm. The rib 223 can also be made with this thickness.
[0034] On the base body 220, a mirror layer 224 is again arranged. The latter may be formed by a coating applied to the base body 220 or by a mirror element that has been placed onto the base body 220. In FIG. 3, the mirror layer is arranged on the side of the base body 220 facing away from the rib 223. In principle, however, it may also be arranged on the side of the base body 220 facing the rib 223. In the embodiment in FIG. 3, the rib 223 is inclined relative to a mirror axis 225 of the mirror 22. The mirror axis 225 refers to the normal on the mirror layer 224 in the center of the mirror layer 224. This allows microstructures to be introduced into the rib 223, which extend up to the lower edge of the mirror layer 224. The inclination of the rib 223 relative to the mirror axis 225 may be in the order of 15?, for example.
[0035] FIG. 4 illustrates the production of a mirror 22 according to the disclosure by injection compression molding. It shows a section through the nozzle side DS and the ejector side AS of an injection compression molding tool. A compression ram P is used to shape the base body 220. The material thickness of the base body 220 may be adjusted by a variation of the compression ram P. Preferably, a hot runner film gate is used in the production of the base body 220. The film gate 227 is indicated in FIG. 4 laterally at the rib 223. The use of a film gate 227 in conjunction with hot runner technology has the advantage that there is no need to separate the base body 220 by milling after the injection molding or injection compression molding procedure. This prevents the formation of chips and eliminates the risk of stress cracks. Overall, this approach reduces waste in production. If the mirror layer is arranged on the side of the base body facing away from the rib, the compression ram P may be produced cost-effectively, since it does not require on its surface the precision or polish of the mirror.
[0036] FIG. 5 schematically shows a pre-deformation of a compression ram P for compensating shape changes. An enlarged section of the transition from the rib 223 to the planar region 221 is shown. Due to the relatively large amount of material at this point and the associated corresponding volume shrinkage during cooling, there is a risk of a small shape deviation in this region. This shape deviation may be reduced or entirely prevented by a counteracting adaptation of the geometry of the compression ram P. The required pre-deformation of the compression ram P may be ascertained, for example, by simulations or tests.
[0037] FIG. 6 schematically shows an anti-reflective structure 226 introduced into a rib 223 of the mirror 22. There is a risk of light reflection on the side surfaces of the mirror 22. This may be avoided by an anti-reflective structure 226. For example, a microstructure may be introduced into the rib 223 as an anti-reflective structure 226. For a sufficiently large inclination of the rib 223 relative to the mirror axis, there is the possibility of introducing into the rib 223 by laser structuring a microstructure which extends up to the lower edge of the mirror layer 224. Alternatively, sandblasting or similar technologies may be used to introduce into the rib 223 a microstructure that has a smaller depth. In this case, the angle of the rib 223 relative to the mirror axis may be reduced.
