PROJECTION ASSEMBLY FOR A VEHICLE, COMPRISING A SIDE PANE

Abstract

A projection assembly for a vehicle, includes a vehicle side pane, which is equipped with a reflective coating, and a projector, which is directed at a region of the vehicle side pane, wherein the radiation of the projector is predominately p-polarized and wherein the reflective coating is suitable for reflecting p-polarized radiation. The projection assembly is provided for displaying entertainment content such as films for the rear vehicle occupants.

Claims

1. A projection assembly for a vehicle, comprising: a vehicle side pane, which is equipped with a reflective coating, and a projector, which is directed at a region of the vehicle side pane, wherein a radiation of the projector is predominately p-polarized and wherein the reflective coating is suitable for reflecting p-polarized radiation.

2. The projection assembly according to claim 1, wherein the vehicle side pane with the reflective coating has, in the spectral range from 400 nm to 650 nm, average reflectance relative to p-polarized radiation of at least 15%.

3. The projection assembly according to claim 2, wherein, in the spectral range from 450 nm to 600 nm, the difference between the maximum occurring reflectance and the mean value and the difference between the minimum occurring reflectance and the mean value is at most 3%.

4. The projection assembly according to claim 1, wherein the radiation of the projector is essentially purely p-polarized.

5. The projection assembly according to claim 1, wherein the radiation of the projector strikes the vehicle side pane with an angle of incidence of 45° to 70°.

6. The projection assembly according to claim 1, wherein the reflective coating includes, alternatingly, optically high-refractive layers with a refractive index greater than 1.8 and optically low-refractive layers with a refractive index less than 1.8.

7. The projection assembly according to claim 6, wherein the optically high-refractive layers and the optically low-refractive layers are implemented as dielectric layers.

8. The projection assembly according to claim 6, wherein at least one of the optically low-refractive layers is implemented as an electrically conductive layer, while the optically high-refractive layers and the remaining optically low-refractive layers are implemented as dielectric layers.

9. The projection assembly according to claim 7, wherein the dielectric optically high-refractive layers are based on silicon nitride, tin zinc oxide, silicon zirconium nitride, or titanium oxide and wherein the dielectric optically low-refractive layers are based on silicon oxide.

10. The projection assembly according to claim 8, wherein the electrically conductive layer is based on silver.

11. The projection assembly according to claim 8, wherein the reflective coating comprises the following layers: a first optically high-refractive layer based on silicon nitride, tin zinc oxide, silicon zirconium nitride, or titanium oxide with a thickness of 260 nm to 280 nm, above that, a first optically low-refractive layer based on silicon dioxide with a thickness of 110 nm to 130 nm, above that, a second optically high-refractive layer based on silicon nitride, tin zinc oxide, silicon zirconium nitride, or titanium oxide, with a thickness of 80 nm to 100 nm, above that, a second optically low-refractive layer based on silver with a thickness of 5 nm to 15 nm, above that, a third optically high-refractive layer based on silicon nitride, tin zinc oxide, silicon zirconium nitride, or titanium oxide, with a thickness of 230 nm to 250 nm, above that, a third optically low-refractive layer based on silicon dioxide with a thickness of 190 nm to 210 nm, above that, a fourth optically high-refractive layer based on silicon nitride, tin zinc oxide, silicon zirconium nitride, or titanium oxide, with a thickness of 120 nm to 140 nm.

12. The projection assembly according to claim 1, wherein the vehicle side pane is designed as a composite pane, comprising an outer pane and an inner pane that are joined to one another via a thermoplastic intermediate layer, and wherein the reflective coating is arranged on the surface of the outer pane or of the inner pane facing the intermediate layer or within the intermediate layer

13. The projection assembly according to claim 12, wherein the external surfaces of the vehicle side pane are arranged substantially parallel to one another.

14. A method comprising utilizing a vehicle side pane, which is equipped with a reflective coating, which is suitable for reflecting p-polarized radiation, as a projection surface for a projector, whose radiation is predominately p-polarized.

15. A method comprising utilizing according to claim 14, wherein, with the projector, entertainment content, are displayed for the rear vehicle occupants.

16. The projection assembly according to claim 2, wherein the vehicle side pane with the reflective coating has, in the spectral range from 400 nm to 650 nm, average reflectance relative to p-polarized radiation of at least 20%.

17. The projection assembly according to claim 11, wherein the thickness of the first optically high-refractive layer is from 268 nm to 271 nm.

18. The projection assembly according to claim 11, wherein the thickness of the first optically low-refractive layer based on silicon dioxide with a thickness of 121 nm to 124 nm.

19. The projection assembly according to claim 11, wherein the thickness of the second optically high-refractive layer is from 89 nm to 92 nm.

20. The projection assembly according to claim 11, wherein the thickness of the second optically low-refractive layer based on silver is from 8 nm to 10 nm.

Description

[0083] in the following, the invention is explained in detail with reference to drawings and exemplary embodiments. The drawings are a schematic representation and not to scale. The drawings in no way restrict the invention.

[0084] They depict:

[0085] FIG. 1 a schematic representation of an embodiment of the projection assembly according to the invention,

[0086] FIG. 2 a cross-section through an embodiment of a vehicle side pane as a component of the projection assembly according to the invention,

[0087] FIG. 3 a cross-section through a first embodiment of the reflective coating according to the invention,

[0088] FIG. 4 a cross-section through a second embodiment of the reflective coating according to the invention,

[0089] FIG. 5 reflection spectra of composite panes of composite panes that are equipped with the coatings of FIGS. 3 and 4.

[0090] FIG. 1 depicts, by way of example, a projection assembly according to the invention. The projection assembly comprises a projector 4, which is attached in the region of a vehicle roof 6. The projector is a dual film projector that emits p-polarized radiation (indicated by dashed arrows). The projection assembly further comprises the two rear side panes 10 of the vehicle, which serve as a projection surface for the projector 4. The side panes 10 are provided with a reflective coating (not shown specifically), which is suitable for reflecting the p-polarized radiation of the projector 4. By means of the reflection of the radiation of the projector 4 on the side panes 10, virtual images 7 are generated, which the viewers 5—the rear vehicle occupants—perceive on the sides of the side panes 10 facing away from them. A film, which appears, as it were, behind the panes in the surrounding landscape, can thus be displayed by the projector 4.

[0091] The projector 4 irradiates the side panes 10 with an angle of incidence of, for example, approx. 65°, which is close to Brewster's angle. Consequently, the p-polarized radiation is hardly reflected by the external pane surfaces. Instead, the reflection occurs almost exclusively on the reflective coating as the only reflection surface. Ghost images, such as would be caused by the use of s-polarized radiation by the reflection on both external surfaces of the side pane 10, can thus be avoided.

[0092] FIG. 2 depicts the structure of an embodiment of the vehicle side pane 10. The side pane 10 is implemented as a composite pane and is composed of an outer pane 1 and an inner pane 2, which are joined to one another via a thermoplastic intermediate layer 3. In the installed position, the outer pane 1 faces the external environment; the inner pane 2, the vehicle interior. The outer pane 1 has an exterior-side surface I, which, in the installed position, faces the external environment; and an interior-side surface II, which, in the installed position, faces the interior. Likewise, the inner pane 2 has an exterior-side surface III, which, in the installed position, faces the external environment; and an interior-side surface IV, which, in the installed position, faces the interior. Applied on the exterior-side surface III of the inner pane 2 is a reflective coating 20 that is suitable for reflecting p-polarized radiation. The outer pane 1 and the inner pane 2 are made, for example, of soda lime glass. The outer pane 1 has, for example, a thickness of 2.1 mm; the inner pane 2, a thickness of 1.6 mm. The intermediate layer 3 is, for example, formed from a PVB-film with a thickness of 0.76 mm.

[0093] FIG. 3 depicts the layer sequence of an advantageous embodiment of the reflective coating 20 according to the invention. The coating 20 is a stack of thin layers, wherein a total of six dielectric, optically high-refractive layers 21 (21.1, 21.2, 21.3, 21.4, 21.5, 21.6) and five dielectric, optically low-refractive layers 22 (22.1, 22.2, 22.3, 22.4, 22.5) are deposited alternatingly on the substrate (inner pane 2). The optically high-refractive layers 21.1, 21.2, 21.3, 21.4, 21.5, 21.6 are based on silicon nitride (SiN) with a refractive index of 2.04. The optically low-refractive layers 22.1, 22.2, 22.3, 22.4, 22.5 are based on silicon oxide (SiO) with a refractive index of 1.47.

[0094] The layer sequence is shown schematically in the figure. The layer sequence of a side pane 10 implemented as a composite pane with the coating 20 on the exterior-side surface III of the inner pane 2 is also presented in Table 1, together with the materials and layer thicknesses of the individual layers.

TABLE-US-00001 TABLE 1 Reference Layer Material character thickness Soda lime 1 2.1 mm glass PVB 3 0.76 mm SiN 20 21.6 212.8 nm SiO 22.5 61.8 nm SiN 21.5 41.7 nm SiO 22.4 108.8 nm SiN 21.4 69.7 nm SiO 22.3 113.2 nm SiN 21.3 68.6 nm SiO 22.2 107.4 nm SiN 21.2 127.4 nm SiO 22.1 51.3 nm SiN 21.1 93.1 nm Soda lime 2 1.6 mm glass

[0095] FIG. 4 depicts the layer sequence of another advantageous embodiment of the reflective coating 20 according to the invention. The coating 20 is a stack of thin layers, wherein a total of four dielectric, optically high-refractive layers 21 (21.1, 21.2, 21.3, 21.4) and three optically low-refractive layers 22 (22.1, 22.2, 22.3) are deposited, alternatingly, on the substrate (inner pane 2). Here, as well, the optically high-refractive layers 21.1, 21.2, 21.3, 21.4 are based on silicon nitride (SiN). The middle optically low-refractive layer 22.2 is implemented as an electrically conductive layer based on silver (Ag), while the remaining optically low-refractive layers 22.1, 22.3 are dielectric layers based on silicon oxide (SiO).

[0096] The layer sequence is shown schematically in the figure. The layer sequence of a side pane 10 implemented as a composite pane with the coating 20 on the exterior-side surface III of the inner pane 2 is also presented in Table 2, together with the materials and layer thicknesses of the individual layers.

TABLE-US-00002 TABLE 2 Reference Layer Material character thickness Soda lime 1 2.1 mm glass PVB 3 0.76 mm SiN 20 21.4 134.0 nm SiO 22.3 198.1 nm SiN 21.3 237.8 nm Ag 22.2 9.1 nm SiN 21.2 90.4 nm SiO 22.1 122.1 nm SiN 21.1 269.7 nm Soda lime 2 1.6 mm glass

[0097] FIG. 5 depicts reflection spectra of a composite pane 10 as in FIG. 2, in each case with a layer structure in accordance with Table 1 and Table 2. The reflection spectrum was recorded with a light source that emits p-polarized radiation of uniform intensity in the spectral range considered, with irradiation via the inner pane (the so-called “interior-side reflection”) at an angle of incidence of 65° relative to the interior-side surface normal. The reflection measurement thus approximates the situation in the projection assembly.

[0098] The purely dielectric layer structure in accordance with Table 1 results, in the spectral range from 400 nm to 650 nm, in an average reflectance of 27%; the layer structure with the silver layer in accordance with Table 2, in an average reflectance of 27%. Thus, both reflective coatings 20 are suitable, in the spectral range of typical film projectors, for effectively reflecting their p-polarized radiation and, consequently, for generating the desired projection image.

[0099] It is discernible that the silver layer of the reflective coating in accordance with Table 2 results in a significant smoothing of the reflection spectrum. In the spectral range from 450 nm to 600 nm, the mean value for the dielectric layer structure in accordance with Table 1 is 28%; the minimum, 23% and the maximum, 32%. The difference between the maximum occurring reflectance and the mean value is thus 4%; the difference between the minimum occurring reflectance and the mean value, 5%. In contrast, the mean value for the layer structure in accordance with Table 2 is 30%; the minimum, 28% and the maximum, 32%.% [sic]. The difference between the maximum occurring reflectance and the mean value is thus 2%; the difference between the minimum occurring reflectance and the mean value is likewise 2%. In the spectral range from 420 nm to 600 nm, the mean value for the dielectric layer structure in accordance with Table 1 is 29%; the minimum, 23% and the maximum, 32%. The difference between the maximum occurring reflectance and the mean value is thus 3%; the difference between the minimum occurring reflectance and the mean value, 6%. In contrast, the mean value for the layer structure in accordance with Table 2 is 30%; the minimum, 28% and the maximum, 32%.% [sic]. The difference between the maximum occurring reflectance and the mean value is thus 2%; the difference between the minimum occurring reflectance and the mean value is likewise 2%. The smoothing of the reflections by the silver layer results in more color neutral reproduction of the projector image.

[0100] Table 3 indicates some optical values of coated side panes that are familiar to the person skilled in the art and are customarily used to characterize vehicle windows. Here, RL stands for the integrated light reflection and TL for the integrated light transmittance (per ISO 9050). The information after RL or TL indicates the light source used, A representing the light source A and HUD representing an HUD projector with radiation wavelengths of 473 nm, 550 nm, and 630 nm (RGB), used here as an exemplary model for a film projector. The angle specification after the light type indicates the angle of incidence of the radiation relative to the exterior-side surface normal. Angles of incidence less than 90° therefore indicate exterior-side irradiation; and angles of incidence greater than 90°, interior-side irradiation. The specified angle of incidence of 115° corresponds to an angle of incidence relative to the interior-side surface normal of 65°(=180°−115°) and simulates the irradiation with the projector according to the invention. When determining the integral reflection values RL, the observation angle is 2°. In each case, below the reflection values are the associated color values a* and b*in the L*a*b* color space, followed by the indication of the light source used (light source D65 and HUD projector) and the indication of the observation angle (angle at which the light beam in the eye strikes the retina).

[0101] TTS ISO 13837 represents the total irradiated solar energy, measured per ISO 13837, and is a measure of thermal comfort.

[0102] The panes have relatively low light transmittance and a distinct color cast with exterior-side reflection. This plays a subordinate role in the case of rear side panes because, here, the requirements for transmittance and color neutrality are less pronounced than in the case of windshields and front side panes. For the projector image displayed (RL HUD p-pol. 115°), good reflection values and good color neutrality are achieved. The TTS value is advantageously low for both coatings, with a further reduction in the irradiated solar energy being achievable with the layer structure according to Table 2 as a result of the silver layer, despite a lower total number of layers.

TABLE-US-00003 TABLE 3 Layer Structure Layer Structure Table 1 Table 2 RL A 8° /% 58.3 40.2 a* (D65 / 10°) −5.6 −15.9 b* (D65 / 10°) 36.4 22.3 RL A 60° /% 53.5 43.0 a* (D65 / 10°) −4.2 0.4 b* (D65 / 10°) 3.1 −0.5 RL HUD p-pol. 115° /% 28.7 29.7 a* (HUD / 10°) −3.5 −0.4 b* (HUD / 10°) 1.5 −0.1 TL A 0° /% 38.7 56.1 TTS ISO 13837 /% 57.3 55.7

LIST OF REFERENCE CHARACTERS

[0103] (10) vehicle side pane [0104] (1) outer pane [0105] (2) inner pane [0106] (3) thermoplastic intermediate layer [0107] (4) projector [0108] (5) viewer [0109] (6) vehicle roof [0110] (7) virtual image [0111] (20) reflective coating [0112] (21) optically high-refractive layer [0113] (21.1), (21.2), (21.3), (21.4), (21.5), (21.6) 1st, 2nd, 3rd, 4th, 5th, 6th optically high-refractive layer [0114] (22) optically low-refractive layer [0115] (22.1), (22.2), (22.3), (22.4), (22.5) 1st, 2nd, 3rd, 4th, 5th optically low-refractive layer [0116] (I) exterior-side surface of the outer pane 1 facing away from the intermediate layer 3 [0117] (II) interior-side surface of the outer pane 1 facing the intermediate layer 3 [0118] (III) exterior-side surface of the inner pane 2 facing the intermediate layer 3 [0119] (IV) interior-side surface of the inner pane 2 facing away from the intermediate layer 3