WO2021139992A1

WO2021139992A1 - Glass vehicle roof with projection transparent screen

Info

Publication number: WO2021139992A1
Application number: PCT/EP2020/086749
Authority: WO
Inventors: Michele CAPPUCCILLI; Johannes Wolf; Cecile Ozanam; Patrick Gayout
Original assignee: Saint-Gobain Glass France
Priority date: 2020-01-06
Filing date: 2020-12-17
Publication date: 2021-07-15
Also published as: CN113383262A

Abstract

The invention concerns a vehicle glazing and display system (1) comprising a vehicle compound glazing unit (10; 10'; 10'', 10''', 10^iv) comprising a layer or surface (12a; 12b; 14) which diffusely reflects incident light directed to the glazing unit from the interior of the vehicle (2) and having a maximum gain in the range of 0.1 to 0.8, preferably between 0.3 and 0.6 and an intrinsic viewing angle α for a real image element generated within the glazing surface of more than 60°, in a first direction and of more than 30°, in a second direction, perpendicular to the first direction, and/or a cover unit and at least two projectors (4) for projecting an image to the vehicle glazing unit or the cover unit to generate a real image in the plane of the glazing unit or the cover unit and wherein the vehicle compound glazing unit (10; 10'; 10'', 10''', 10^iv) is a glass roof.

Description

Glass vehicle roof with projection transparent screen

Field of the Invention

The invention is in the field of displaying information on a glazing element of a vehicle or a cover unit. More specifically, the invention is in the automotive field, but it is not restricted to this field but can be implemented in buses, railway cars, boats, airplanes or other vehicles. More specifically, the invention is related to a vehicle glazing and display system, comprising a vehicle compound glazing unit and a projector for projecting an image to the glazing unit.

Background / Prior Art

In this technical field, there are many patents or patent applications which are, to a certain extent, background art to the present invention.

US 7 157 133 discloses the basic concept of diffuse reflection with embedded diffusing surface.

EP 2 185 966 discloses an element with a diffusing surface on which a reflective layer is deposited, the whole being in an envelope of the same refractive index as the diffusing element. The assembly is designated as a numerical aperture expander working in reflection, which seems functionally close to a diffuser and a transparent element in transmission. In this patent, the integration of such an element in a head-up display (HUD) projection system for generating virtual images is mentioned.

US 8 519 362 B2 to Saint-Gobain describes an HUD system assembled into a car. It is based on a laminated windshield where the HUD function comes from a layer of luminophore material. US 7 230 767 B2 describes a display system in a car glass pane using a light emitting material projecting the image to the driver. The image is a virtual image, focused meters away from the eyes of the driver and from the windshield.

A preparation process of an HUD system integrated into a laminated glass pane is described in the Saint-Gobain owned patent EP 2 883 693.

Regarding the general concept of transparent glazing units which have a certain degree of diffuse reflection, there are several patent publications of Saint-Gobain, e.g. EP 2 670 594, EP 2 856 256, EP 2 856 533, EP 2 872 328, EP 3 063 002, WO 2012 104 547, WO 2018 015 702, and FR 3 054 17. In these patent documents, it is, inter alia, disclosed that such diffusely reflective glazing can contain a rough internal surface and a coating provided thereon and that such glazing can be used for OLED display solutions or for projection-based display solutions.

EP 3 395 908 A1 discloses a transmission type screen as head-up-display for automotive applications, in which the screen is particle based.

In EP 3 151 062 A1 a video projection structure for integration into an automotive window is presented, wherein the window contains a reflection film applied on a surface having random irregularities.

JP 2016 9271 A discloses a video display system, which is equipped with detection means to detect a movement of the observer, wherein display system can be operated by the movement of the observer.

DE 10 2004 051 607 A1 discloses a device and a method for displaying a digital image onto a geometrical and photometrical non-trivial surface. In particular, the document discloses to project an image with one or more projectors onto a non-planar surface. The projection method comprises in particular a calibration with a camera connected to a control system which is adapted to control the one or more projectors for adjusting the projection of the image for each displayed pixel of the image.

In US 2014 168608 A1 an image projecting system for a road vehicle is disclosed, which projects a motion picture on an interior surface of the vehicle. An area of the window glass of the vehicle is changeable from transparent to the screen for image projection either by a change in a property of the window glass or covering the area of the window glass by an image reflecting surface.

In US 2019 0351654 A1 a luminescent display system is described, which shall display information at a predetermined luminance over a wide area. The luminescent display system includes a luminescent resin film containing a thermoplastic resin and a luminescent material.

US 2010 0253594 A1 discloses a method to selectively project graphical images upon a transparent windscreen head up display of a vehicle based upon visual information present in a peripheral zone of vision.

A head-up display device with a transmission type screen is disclosed in US 2018 0348512 A1. The transmission type screen comprises a first surface, and a second surface opposed to the first surface, wherein the first surface is equipped with a microlens array including a plurality of microlenses and the second surface is equipped with a light diffusion surface.

CN 108312975 A discloses a vehicle with a sunroof as display screen, wherein the sunroof comprises an electrochromic layer and wherein two projection devices are embedded into the B-pillars of the vehicle. The projection devices can be flipped from the corresponding B-pillars to project an image onto the sunroof. The sunroof with electrochromic layer is electrically switchable from a transparent state with a visible light transmission of at least 70% to an opaque state with a visible light transmission of maximum 8%. The opaque state is used within projection mode. Thus, during projection the outside of the vehicle is not visible for the passengers.

It is an object of the present invention, to provide a vehicle glazing and display system and corresponding vehicle compound glazing unit, which are adapted for a broad range of applications in future mobility solutions. More specifically, it is an object to provide a system which makes it possible to display rich content to basically all persons which use a vehicle or at least to all those persons, which sit close to a respective glazing unit. Furthermore, a solution is required which can be implemented, to a far extent, on the basis of available technologies and which is safe, reliable and cost-efficient.

These, and further, objects are solved by a vehicle glazing and display system according to claim 1. Preferred embodiments of the invention are subject of the respective dependent claims.

The vehicle glazing and display system according to the invention comprise a vehicle compound glazing unit comprising a layer or surface which diffusely reflects incident light directed to the glazing unit from the interior of the vehicle and at least two projectors for projecting an image to the vehicle glazing unit to generate a real image in the plane of the glazing unit. Optionally the vehicle compound glazing unit can comprise additionally a cover unit. If this is the case the image can additionally also be projected to the cover unit and the vehicle compound glazing unit comprises a layer or surface which diffusely reflects incident light directed to the glazing unit from the interior of the cover unit and the at least two projectors for projecting an image to the cover unit generate a real image in the plane of the cover unit. The compound glazing unit is a glass roof of the vehicle. The cover unit might be a cover to obscure or shade the glass roof or a lining of the vehicle ceiling, particular a lining comprising a plastic layer or a textile lining. The cover unit might comprise a textile curtain or textile lining, in particular having a light color. The vehicle glazing with display system shows a maximum gain (also referred to as peak gain) in the range of 0.1 to 0.8, preferably between 0.3 and 0.6. The vehicle compound glazing unit comprises an inner glass or plastic pane, an outer glass or plastic pane and a diffusely reflective plastic sheet laminated between the inner and outer glass or plastic panes and. The diffusely reflective sheet is an adhesive sheet or is embedded between two adhesive films or layers, for bonding the inner glass or plastic pane to the outer glass or plastic pane. The intrinsic viewing angle a for a real image element generated within the plane of glazing is larger than 40°, preferably larger than 60° and more preferably larger than 70° or more in a first direction and larger than 20°, preferably larger than 30° in a second direction, which is perpendicular to the first direction. When using these intrinsic viewing angles within practical application at standard environment conditions, a practical viewing angle of larger than 60°, preferably larger than 90° and more preferably larger than 120° or more in a first direction and larger than 30°, preferably larger than 45° in a second direction, which is perpendicular to the first direction, can be achieved. The practical viewing angle is dependent of both the luminous environment and the used projector. Nevertheless, the practical viewing angle is a commonly used feature for screen specification and can be determined for chosen environment conditions related to a particular use case. For standard environmental conditions and projector specification the following values could be used:

External illuminance 2200 Lux (outside the car); internal illuminance 100 Lux (inside the car); flux from projector 3500 Lumen; Projection surface: 16:9 screen with 9“ diagonal (20 cm width); the practical view angle can then be extracted from gain curve via a mathematical formula.

The practical viewing angle is studied on the basis of the contrast of the screen. The contrast of a screen is commonly defined as the luminance ratio between a white and a black picture, wherein a minimum ratio of 4.5: 1 (white picture to black picture) is considered as necessary for information reading. Based on this, the practical viewing angle can be derived as the observation angle Q within the position where at least the minimum contrast of 4.5: 1 is achieved.

The intrinsic viewing angle a of a projection screen is measured at the full width half maximum (FWHM) of the peak around the maximum value of the gain, independent of the value of the observation angle Q at the peak center. The Q =0° reference for the gain curve measurement corresponds to the specular reflection direction. Thus, the intrinsic viewing angle a is a property of the screen and not dependent on environmental luminance and projector specification. Thus, as the maximum of the gain curve often occurs at q=0°, the intrinsic view angle can also be defined in this case as twice the observation angle Q at the position of the gain curve where the half maximum width of the gain curve is achieved.

The viewing angle (intrinsic and practical) shall be maximized as large viewing angles are necessary to ensure that all passengers of a vehicle can clearly see the projected content at the same time independent of the seat occupied by a person. However, with a given screen total reflectivity, a compromise between a high peak gain and a large viewing angle has to be found. The vehicle glazing according to the invention provides such a good compromise between peak gain and viewing angle.

In a preferred embodiment of the invention, the transparent screen of the vehicle glazing has a maximum gain between 0.1 and 0.8 and a practical viewing angle superior to 60° in one direction and larger than 30° in the other one. Typically, for the practical viewing angle values between 120° to 150° in horizontal plane and between 30 and 180° in vertical plane are derived. Within the intrinsic angle definition an intrinsic viewing angle superior to 40°, more preferably superior to 60°, even more preferably between 70° and 150°, in horizontal plane and between 20° and 180°, preferably between 30° and 180°, in vertical plane is derived. Vertical plane and horizontal plane are defined within the assembly situation of the vehicle glazing within the car body.

Thanks to the mentioned practical and intrinsic viewing angles, all the occupants in the vehicle can see the display when the projector is on. According to a further aspect of the invention, the displayed image is a real image. A real image differs from a virtual image concerning the plane of focus. For virtual images, the plane of focus has a certain distance to the projection screen, e.g. one meter or up to several meters. In contrast to this for real images the plane of focus is near to the screen. Preferably, the plane of focus for a real image according to the invention has a maximum distance of 30 cm to the projection screen.

When the projector is off, the glazing is optically similar to a traditional glazing, maintaining transparency with a slightly higher haze value. A typical haze value for such a glazing is between 1 % and 6 %, preferably between 2.5 % and 4.5 % measured according to the standard ASTM D 1003. The haze measures the fraction of transmitted light that is deviated from the straight path with an angle larger than 2.5°. High haze values correspond to a loss of contrast of the image projected on the screen. Within the given range of low haze values, a good transparency of the screen is obtained.

According to a further preferred aspect, the reflective layer or surface within the glazing unit has a transmission of visible light of higher than 60 %, preferably of 70 % or more, for example 80 % or more. These transmission values (also referred to as global luminous transmission TL) quantify the ability of the reflective layer or surface to transmit light of wavelength between 400 nm to 800 nm, which is the range of the spectrum visible to human eye. For those measurements, no distinction between diffused light and non- diffused light has to be made. Nevertheless, the technology according to the invention is also applicable to glazing in which a lower light transmission is desired. The screen ensemble of the invention is to be used in glass roofs for vehicles, which usually comprise tinted glass or plastic components and have an overall transmission of visible light below 30 %. Such an application is of particular interest in combination with autonomous driving technology. In this case, the roof could for example be used as entertainment screen.

To measure the gain and determine suitable viewing angles of a transparent screen, one has to measure the luminance of the screen as a function of the observation angle with a projector illuminating the screen with a normal incidence (0°). The luminance of an ideal screen (Lambertian reference called Spectralon) is measured under the same conditions. An ideal screen is defined as a screen whose luminance does not depend on the projection or observation angle and whose reflectivity is 100%. The Lambertian reference screen is a surface perfectly obeying Lambert’s cosine law saying that the luminous intensity observed from an ideal diffusely reflecting surface is directly proportional to the cosine of the angle between the direction of the incident light and the surface normal. The human eye can only recognize the luminance, which is a measure of luminous intensity per unit area of light travelling in a given direction, and describes the amount of light that is reflected from a particular area. Thus, a Lambertian surface with ideal diffuse reflection is seen by the human eye as showing the same luminance and brightness independent of the observation angle from which it is viewed. Experimentally an ideal Lambertian diffuser is accessible by commercially available reference materials known as “Spectralon”, which is made of sintered polytetrafluoroethylene (PTFE). To retrieve the gain of the screen at each observation angle, the ratio between the screen luminance and the ideal screen luminance is calculated. The peak gain of the screen is the maximum gain value reachable for the screen. The maximum gain (also referred to as peak gain) is often measured at 0° but some specifically designed screen may have their maximum gain at other observation angle. It is to be noted that for a transparent screen, the value at 0° may not be measureable because of the hotspot (specular reflection of projector light on the external flat glazing surface) and is therefore extrapolated from gain at small angle.

Preferred intrinsic viewing angles are defined from the gain as being within the full width half maximum of the gain curve (see Figure 2). This definition is an intrinsic one. The gain denotes the luminance of the projection screen relative to the luminance of an ideal screen, which is a perfect Lambertian diffuser.

An alternative, more practical, definition of the viewing angle would be to define a practical viewing angle as the observation angle where the contrast is lower than 4.5:1 , but such definition depends on observation and illumination conditions and projector. Thus, the intrinsic definition of viewing angles, being within the full width half maximum of the gain curve, is preferred. The gain curve can be determined as already described and has for example the shape of a Gaussian curve.

The inventors detected that that not only observation angles inferior to the half of the intrinsic view angle (i.e. within the full width half maximum of the gain curve) are suitable for practical application of the transparent screens. Adequate observation results can be achieved under observation angles inferior to the half of a practical view angle in the range of 120° to 180° within horizontal plane, preferably 120° to 150° within horizontal plane, and 30° to 180° within vertical plane.

To achieve a sufficient contrast, the projector should have an output flux higher than 1000 Lumen, better higher than 3000, ideally between 2000 and 10Ό00. The best projector flux values have to be chosen depending on the environmental conditions.

The projection screen size can be big, depending by the projector brightness; position and screen gain and viewing angle. A typical image size, in operation of the system, is larger than 10” (25 cm), usually between 10” (25 cm) and 60” (152 cm), with preference between 30” (76 cm) and 50” (127 cm) for one projector. The image size is measured as diagonal size in the unit inch as it is common within the field of screen technology. Using two or more projectors for a glass roof, the glazing unit for displaying the image may have a size of at least 1 ,5 m x 1 , 5 m, more preferably at least 2 m x2 m, more preferably 2 m x4 m. In the case of public transport even size around 2 to 4 m x 10 to 50 m are possible.

As the available distance between the projector and the glazing, in the orthogonal direction to the glass surface (projection distance), is usually between 2 cm and 60 cm, preferably between 7 cm and 40 cm, a preferential option is to use a short-throw projector. The throw ratio (size of the image/distance between projector and screen) is usually larger for short-throw projectors. In a short-throw projector, there is often a folding optics so that the projector image can be displayed in a plane that is perpendicular to the output lens. The projector may be a projector having a conventional lamp, a LED or a LASER as illumination means.

In the present case the projector is preferably arranged in or at a frame element, which is preferably arranged along a side edge of the roof. In an alternative embodiment, the projector might be arranged at the pillar body of the vehicle body, in particular under a lining of such a pillar. In order to reduce a dazzling of vehicle occupants the projectors are arranged along the side edge of the roof, which is essentially parallel to the driving direction of the vehicle. In an advantage embodiment, the projectors are arranged along both side edges parallel to the driving direction of the vehicle. The system may comprise three, four, five, six, seven, eight or more projectors. In case of an even number of projectors the projectors are preferably arranged in pairs facing each other. In case of an uneven number of projectors, the projectors are preferably arranged alternatingly on one side and the other. In a preferred embodiment, the projectors are arranged uniformly along the side edge to have equal distances between neighboring projectors.

The projectors are preferentially connected with a projector control unit which controls the projectors such that a combined image is displayed for the two or more projectors. In particular, the projector control unit comprises a camera for the calibration of the combined image such that a single image seems to be projected. The projector control unit is as well adapted to correct the projection of the image for a curvature of the roof. The projector control unit, in particular with the camera, might be as well adapted to calibrate the image projected to a textured surface, in particular a cover unit with a textile lining.

The above-referenced generation of hot spots in the glazing unit can, to a certain extent, be suppressed by a suitable arrangement of the respective (inner and outer) surfaces of the glazing unit and, in particular, of the diffuse reflective sheet coating or surface, respectively. In a preferred embodiment, the projectors are arranged such that a possible hot spot is located above a frame in which the projectors are arranged. By such an arrangement, a possible generated hotspot is not visible from a seating position inside the vehicle. As an additional means for suppressing the hot spots at least one local blind can be arranged close to the output lens of the projector, in a suitably pre-defined position.

Additionally or alternatively, if the incident light at the glazing unit is polarized, in particular p-polarized, it can be suppressed when the incident angle is near to the Brewster angle.

The image projected on the transparent screen is due to diffuse reflection. The reflection of a glazing is defined as diffuse reflection when incident radiation on the glazing with a given angle of incidence is reflected in a plurality of directions. Specular reflection occurs when incident radiation on the glazing with a given angle of incidence is reflected with an angle of reflection equal to the angle of incidence. Likewise, transmission is defined as specular when incident radiation with a given angle of incidence is transmitted with an angle of transmission equal to the angle of incidence. However, to keep transparency on the whole glazing, the inner face and outer face of the glazing are flat and therefore induce specular reflection from the projector beam. To achieve the experience, the light reaching the eye of the vehicle passengers should be given by the “diffuse reflection” of the projected image on the glass. The specular reflection on the inner and outer face of the glazing should be avoided. The specular reflection is also referred to as “hot-spot”, which glares the observer when it is directed to the viewer. The direction of the hot-spot is available via the law of reflection saying that the angle of reflection equals the incidence angle. To avoid glaring the viewer by the hot-spot, the hot-spot and the observation direction of all passengers of the vehicle show preferably an angle distance of at least 5°, more preferably at least 10°, most preferably at least 20°.

Regarding the configuration of the vehicle compound glazing unit, according to a first aspect of the invention, the glazing unit comprises an inner glass or plastic pane, an outer glass or plastic pane and a diffusely reflective plastic sheet laminated between the inner and outer glass or plastic panes.

In an embodiment of this aspect, the diffusely reflective sheet is an adhesive sheet or is embedded between two adhesive films or layers, for bonding the inner glass or plastic pane to the outer glass or plastic pane. According to another aspect of the invention, the glazing unit comprises an inner glass or plastic pane, an outer glass or plastic pane and an adhesive film or layer for bonding the inner glass or plastic pane to the outer glass or plastic pane. Herein, the inner surface of the inner or outer glass or plastic pane, contacting the adhesive film or layer, respectively, comprises a diffusely reflective coating or is treated to make the surface a diffuse reflector, e.g. by use of textured glass. In other words, a glass, which is structured on one side, may be laminated with the structured surface against a flat glass by an adhesive film or layer. Hence, according to this aspect, no separate diffusely reflective sheet is laminated into the compound glazing unit, but the diffuse reflexivity is imposed unto one of the basic components of the glazing unit, i.e. on one of the glass (or plastic) panes. Due to the low number of necessary layers, production costs and the number of productions steps are reduced.

In embodiments according to both aspects, the diffusely reflective plastic sheet or diffusely reflective coating of the coated glass or plastic pane comprises nanoparticles or microparticles within transparent substrate. More specifically, the nanoparticles or microparticles are silica or polymer or liquid crystal particles. Metal or metal oxide particles can also be used. More specifically, the nanoparticles or microparticles can have spherical shape and/or are transparent or translucent.

Plastic sheets with a diffusely reflective coating comprising titanium oxides TiO_x particles or silver particles as well as plastic sheets with an organic diffusely reflective coating comprising cholesteric liquid crystals have turned out to be especially suitable for the screen applications according to the invention. Most preferably the diffusely reflective plastic sheet contains liquid crystal particles, which are oriented within a matrix.

In another embodiment, one surface of the diffusely reflective plastic sheet comprises a random nanostructure or microstructure and, in particular, the other surface is polished.

Preferably the diffusely reflective plastic sheet comprises a polyethylene (PE), polyethylene terephthalate (PET), poly methyl methacrylate (PMMA), polyvinyl butyral (PVB), triacetyl cellulose (TAC) or polycarbonate sheet. Such sheets are basically commercially available or can be manufactured upon request of the manufacturer of the vehicle compound glazing unit, tailored to the specific optical requirements according to the invention. From a manufacturing point of view, less material is needed as the interlayer used for windshield lamination is responsible for the transparency and no specific planarization layer protected by a counter-film is needed.

Furthermore, with some texturation techniques (e.g. embossing), the random texture can be chosen so that the view angle is large enough. Even the random texture of the transparent screen has some statistical parameters (according to norm ISO 4287), wherein a good choice of these parameters, in particular of the mean square slope of textured layers, enables to tailor the intrinsic viewing angle.

Compared to solutions with particles embedded in a transparent matrix, the use of a rough plastic film with textured layers yields good values for clarity and haze on the one hand and gain on the other hand. With particle embedded solutions a compromise between those is always necessary. Concerning an index matching of the refractive indices of the sheets, the non-coated plastic sheet has to be taken into account. As described in WO 2012/104547, thin layers coated on a textured surface need to have different refractive indices to achieve reflective properties, but as long the outer layers (here plastic sheet and interlayer) have the same refractive index and all the textured interfaces are parallel, transparency is obtained.

Diffusive reflective plastic sheets have the advantage that they can be inserted only at the screen location and thus more easily tailored.

In an alternative embodiment, a rough glass sheet can be used instead of the rough plastic film. This has the advantage that a glass sheet can be integrated in standard lamination processes.

At least in embodiments, the system of the invention results in significant advantages which open a wide range of applications in future mobility concepts, including driver- driven or autonomous cars, buses, train or subway cars, boats, airplanes and aerocabs.

In the framework of such concepts, the users will require that a broad range of information be displayed to all of them (not only a driver) in a convenient and flexible way, and big size displays implemented by means of the invention will be highly attractive in this regard. On the other hand, the glazing which is used for the display of information is still fully transparent, and the projection of light to outside the vehicle - which might disturb persons outside or even be dangerous - can be directed outside the expected eye boxes of other road users. The main application of the invention is to display contents on glass in a vehicle (also autonomous vehicles, buses, taxicabs, trains, tractors, airplanes). This can be used to provide information internally for the driver and vehicle passengers. Also we can think of an infotainment system integrated into the glass enabling for a mixed reality environment: this means that the occupant’s eye will see the image of the outer environment combined with the image projected on the glazing. This is kind of “augmented-reality”.

In the same way, safety information, touristic information, divertissement, like videos, and advertisement can be shown on the glass panes. This can lead to a usage of the glazing surface of the vehicle as an advertisement surface, while maintaining transparency.

Some safety features can be introduced by this technology: the image being surprisingly visible from inside and outside the vehicle, some information can be displayed to inside or outside users, depending on the need. It is to be noted that such an image visible from outside the vehicle corresponds to diffuse light and therefore not glaring the other road users and thus not contradictory with inventions requirements.

In the context of public transport, we can think of information on routes, transport purpose, next stop, final destination on the windows of buses, trains, etc.

Likewise, it will be of huge interest for the advertisement industry regarding customer targeting and context enhancement.

The invention can be combined with other technologies as e.g. HUD, any specific coating, Smart-WS etc. It is possible to include this technology (transparent display in glazing) in other more complex system, for example integrating a camera for interaction with the vehicle occupants (e.g. skype call with call partner projected on glass).

In the following some preferred embodiments of the invention are described.

The vehicle glazing and display system comprises a vehicle compound glazing unit comprising a layer or surface which diffusely reflects incident light directed to the glazing unit from the interior of the vehicle and having a maximum gain in the range of 0.1 to 0.8, preferably between 0.3 and 0.6 and a viewing angle for a real image element generated within the glazing surface of more than 60°, preferably more than 90° and more preferably of 120° or more, in a first direction and of more than 30°, preferably more than 45°, in a second direction, perpendicular to the first direction, and/or a cover unit, and at least two projector for projecting an image to the vehicle glazing unit or the cover unit to generate a real image in the plane of the glazing unit or the cover unit. The glazing surface of the glazing unit being the glass roof. This glass roof may in particular be a curved or convex glass roof. Therefore, the glazing surface may be plane or curved.

Preferably, the cover unit is arranged in a retractable way under the glass roof, having a retracted state, where the cover unit does not cover the vehicle compound glazing unit, and a covering state, where the cover unit covers the vehicle compound glazing unit. There might be intermediate states between the retracted state and the covering state. The cover unit might be a conventional sunblind for a vehicle glass roof.

Preferably, the glazing unit has a typical haze value in the range of 1 % to 6 %, preferably between 2.5 % and 4.5 %, and/or the reflective layer or surface within the glazing unit has a transmission of visible light of higher than 70 %, preferably of 80 % or more.

Preferably, the vehicle glazing and display system is adapted as a roof head-up display, HUD, in a car, boat or airplane/aerocab.

Preferably, the vehicle glazing and display system further comprises a projector control unit connected to the at least two projectors adapted to calibrate the projection of the image on a pixel base. The projector control unit may comprise a camera.

Preferably, the projector is adapted to be arranged at two opposite sides of the roof, in particular in a frame arranged at least partially in a circumferential direction under an outer area of the roof.

Preferably, at least one local blind is arranged close to the output lens of the projector, such that the generation of hot spots in the glazing surface of the glazing unit is avoided.

Preferably, the projector is adapted to provide an output flux of at least 1 ,000 Lumen, preferably of 3000 Lumen or more. Preferably, the vehicle glazing and display system is adapted to generate, in its assembled state, a real image in the glazing surface with a horizontal extension of at least 25 cm, preferably between 40 cm and 60 cm.

Preferably, at least three projectors, preferably four projectors, preferably six or eight projectors are arranged in two rows along both longitudinal sides of the roof.

Preferably, the glazing unit comprises an inner glass or plastic pane, an outer glass or plastic pane and a diffusely reflective plastic sheet laminated between the inner and outer glass or plastic panes.

Preferably, the diffusely reflective sheet is an adhesive sheet or is embedded between two adhesive films or layers, for bonding the inner glass or plastic pane to the outer glass or plastic pane.

Preferably, the glazing unit comprises an inner glass or plastic pane, an outer glass or plastic pane and an adhesive film or layer for bonding the inner glass or plastic pane to the outer glass or plastic pane, wherein the inner surface of the inner or outer glass or plastic pane, contacting the adhesive film or layer, respectively, comprises a diffusely reflective coating or is treated to make the surface a diffuse reflector.

Preferably, the diffusely reflective plastic sheet or diffusely reflective coating of the coated glass or plastic pane comprises nanoparticles or microparticles within transparent substrate.

Preferably, the nanoparticles or microparticles are silica or polymer or liquid crystal particles.

Preferably, the nanoparticles or microparticles have spherical shape and/or are transparent or translucent.

Preferably, one surface of the diffusely reflective plastic sheet comprises a random nanostructure or microstructure and, in particular, the other surface is polished.

Preferably, the diffusely reflective plastic sheet comprises a PE, PET, TAC, PVB, PMMA or polycarbonate sheet. Preferably, the vehicle glazing and display system is integrated into a vehicle.

Embodiments and aspects of the invention are illustrated in the drawing. In the drawing shows

Fig. 1 a schematic cross-section of a vehicle glazing and display system according to an embodiment of the invention,

Fig. 2 an illustration for explaining definitions of the term “gain” in the context of the invention,

Fig. 3 schematic view of possible arrangements of the vehicle glazing and display system,

Fig. 4 schematic cross-sectional illustration of embodiments of vehicle compound glazing unit, and

Fig. 5A to 5E schematic view of a vehicle glazing and display unit.

Fig. 1 shows an exemplary arrangement of a vehicle glazing and display system 1 within a car 2, for projecting images onto a glass roof 3 of the car by means of a first projector 4a and a second projector 4b which are arranged within a frame of the vehicle (not shown). The glazing surface is as depicted not necessarily a flat plane but may be as in the depicted embodiment curved.

In an exemplary geometrical configuration, the projector can be a commercially available short-throw lamp projector which has a brightness of 3500 Lumen and a contrast ratio of 13Ό00: 1 and which is arranged inside the frame structure of the vehicle at or under the roof. The two projectors 4a, 4b are arranged facing each other. The first projector 4a is arranged on the left side of the vehicle as seen from behind. The second projector 4b is arranged on the right side of the vehicle. The first projector 4a mainly projects to the right side of the roof, wherein the second projector mainly projects to the left side of the roof. In the middle of the roof, the projections of both projectors overlap. By calibration of the projectors it is possible, to render the image to a single image projected by both of the projectors. The image is shown to be visible as much to a sitting vehicle occupant 20a as to a partially lying occupant 20b of the vehicle. In principal, any intended position of the vehicle seats or in case of public transport vehicles standing occupants 20 is suitable viewing the image on the glass roof.

An exemplary structure of the glass roof 3 is: 2.1 mm clear glass, thin PVB (0.38 mm), transparent diffuse reflective screen foil (0.045 mm), very thin PVB (0.05 mm), 2.1 mm green glass. The glass roof may have the following parameters:

Transparency: above 70% TL-A

Hazemeter measurement: light transmission 81.3%; haze 3.4% (measured according to norm ISO 14782); clarity 99.7% (measured with hazemeter HazeGuard Plus from Byk- Gardner)

Screen properties: The intrinsic viewing angle is 70° with a maximum gain of 0.27. In practice, a “usable” practical viewing angle of ca 170° can be observed in the horizontal plane (see previous definition of gain and viewing angle).

It is also possible to project the screen only on a part of the glass pane, using an optical element, directly controlling the light from the source (projector) or changing the projector features. The invention can include the use of a darker interlayer foil or any darker element that would help to increase the contrast by lowering the transmission while keeping transparency.

The required brightness and flux of light to be sent by the projector varies, depending on the projection direction.

In case the system has to be integrated in an existing car, due to packaging and space constraints, it is sometimes impossible to avoid hot-spot, and therefore it is needed to recur to other methods to avoid the hot-spot for the passengers.

As the hotspot is caused by the specular reflection of the light projected by the projector and reaching the eyes of the occupants, one way to eliminate the hot-spot, is to interfere in some light rays come from the projector, for example placing an opaque, non-reflecting obstacle, which partially reduces or traps the projected surface on the glass. The hotspot can also be avoided by reducing the image size, so that the angular area where the observer can hit a specular reflection is reduced.

In an embodiment, the elimination of the hot-spot is performed identifying the hot-spot positions for all the occupants, and then placing a non-reflecting optical surface (piece of dark paper or of dark material) between the projector and the portion of the glass roof where the hotspot is appearing.

Fig. 2 shows diagrams for explaining the important parameter “gain” with respect to a screen, e.g. the glass roof 3 in Fig. 1 , referring to the explanations further above. The gain measurements were carried out using a luminance meter, and a video projector. The luminance is measured at various observation angles for a given incidence angle of the projected light. The projection angle was set as close as possible to 0° (normal to the screen). When the projection angle is held fixed, the gain depends only on the observation angle Q. The luminance meter position is consequently adjusted so that when the observation angle is set to 0° in the horizontal plane, the luminance meter is aligned with specular reflection; the observation angle is therefore really equal to 0° as the specular direction is taken as the reference for observation angle measurement. Luminance measurements were carried out every five degrees 5° to 75° (measured in the horizontal plane) in an unlit environment isolated from any light source other than the video projector. A Spectralon measured under the same conditions was used to standardize the luminance measurements and to extract the gain therefrom. The intrinsic viewing angle a can be derived from these measurements as the full width half maximum of the gain curve and depicts the angular width for which the gain is superior to half the peak gain.

Fig. 3 shows an exemplary arrangement of six projectors for a glass roof of a vehicle. Three of the projectors 4 are placed on a left side of the vehicle under the roof and three other projectors 4 are placed on the opposite right side of the vehicle under the glass roof within the vehicle interior. The projectors are arranged in pairs facing each other. A projector on the left side projects to the right side of the roof wherein a projector on the right side projects on the left side of the roof. The projections of projectors arranged facing each other overlap in a first area. The projections of projectors arranged at the same side next to each other overlap in a second area. The entirety of the projectors are calibrated to form one image in such a way, that it appears to be an uniform image. For such a calibration, the six projectors are connected to a projector control unit (not shown) which renders the projected image. The projector control unit may preferably comprise a camera or is connectable to a camera. Such a camera may be a mobile camera or adapted to be installed facing the glass roof. An image generated by the projector in the glazing surface of the vehicle compound glazing unit 10 being integrated in the roof is shown and designated with numeral 6.

The image projected on the transparent screen is due to diffuse reflection. However, to keep transparency on the whole glazing, the inner face (face IV) and outer face (face I) of the glazing are smooth and therefore induce specular reflection from the projector beam. In this context a smooth surface is a surface without 3-dimensional structuring. Of course, the outer pane and the inner pane show a 3-dimensional bending as typical for the roof. To achieve the experience, the light reaching the eye of the vehicle passengers should be given by the “diffuse reflection” of the projected image on the glass and the specular reflection (on the inner and outer face of the glazing) should be avoided. Depending on the embodiment of the transparent screen, the inner faces of the glazing (face II and face III) can be textured or smooth, wherein smooth surfaces induce specular reflection and structured surfaces lead to diffuse reflection, which is in more detail explained within fig. 5A to 5E.

Fig. 4 shows an exemplary placement of two projectors 4 in respect of the roof. A first projector 4a of the projectors 4 is placed on the left side of the figure, which is supposed to be as well the left side of the vehicle in driving direction. Projector 4a is arranged at the edge of the roof with a projection direction mainly towards a middle and right side of the roof. A beam emitted from the projector 4a is transmitted through an inner face of the glazing and display unit and might be slightly deviated in its direction by entering the first layer of the glazing and display unit which is in particular an inner glass. Continuing in propagation to the glazing layer the beam is reflected at the glazing layer. The glazing layer has a structured surface, having various local surface normal. The beam of projector 4a is reflected at a point of the glazing layer having a local surface normal NL2 towards an eye of the occupant 20.

A second projector 4b of the projectors 4 is placed on the right side of the figure, which is supposed to be as well the right side of the vehicle in driving direction. A beam emitted from the projector 4b is transmitted through an inner face of the glazing and display unit 10 and might be slightly deviated in its direction by entering the first layer of the glazing and display unit 10 which is in particular an inner glass. Continuing in propagation to the glazing layer the beam is reflected at the glazing layer. The beam of projector 4b is reflected at a point of the glazing layer having a local surface normal NL1 towards an eye of the occupant 20.

Fig. 5A-5E show exemplary embodiments of the vehicle compound glazing unit (or: laminated glazing unit) according to the invention.

Fig. 5A shows a glazing unit 10 which basically has a conventional structure, i.e. consists of an inner glass pane 11 and an outer glass pane 12 which are bonded together by means of a thermoplastic interlayer 13, preferably a thin PVB sheet. The outer glass pane 12 comprises an outer surface (also denoted as face I) and an inner surface (also denoted as face II). The outer glass may be a clear glass or a tinted glass as well as the inner glass may be a clear glass or a tinted glass. The inner glass pane 11 also comprises an inner surface (face III) and an outer surface (face IV). The inner surface (face II) of the outer glass pane 12 and the inner surface (face III) of the inner glass pane 11 are bound to each other by the thermoplastic interlayer 13. The inner surface 12a (face II) of the outer glass pane 12 comprises a random nanostructure or microstructure, respectively, which is adapted to provide an angle of view and a sufficient diffuse reflection according to the specifications of the invention, at the same time maintaining a sufficiently high transmission. The structured inner surface 12a is provided with a thin reflective coating (not shown). To achieve a high transparency of the glazing an index-matching of the refractive indices between glass and interlayer is necessary. These two dielectric materials should have substantially the same refractive index, or their refractive indices should be substantially equal, which is defined as the absolute value of the difference between their refractive indices at 550 nm being less than or equal to 0.15. Preferably the absolute value of the difference in refractive index at 550 nm between the constituent materials of the two layers is less than 0.05, more preferably less than 0.015. This applies not only for the specific embodiment of fig. 5A with PVB as interlayer and a structured glass surface as diffusive layer, but also to other embodiments analog to this.

Fig. 5B shows a glazing unit 10’ which, corresponding to a conventional laminated glazing unit, comprises an inner glass pane 11 and an outer glass pane 12 and an intermediate layer bonding the glass panes 11 , 12 together. However, different from the arrangement of Fig. 5A, the intermediate layer 13 is a multilayer comprising a first thermoplastic interlayer 13.1 , preferably a PVB sheet, and a second thermoplastic interlayer 13.2, preferably a PVB sheet and, embedded between the two thermoplastic interlayers (PVB sheets), e.g. a diffusely reflective sheet 14 of PET or PMMA. The reflectivity of the sheet 14 is due to transparent or semi-transparent nanoparticles or microparticles which are randomly distributed in the material of the sheet. These can e.g. be silica or glass beads or polymer or liquid crystal particles. In a modified embodiment, the sheet 14 can be a clear sheet but have one of its surfaces provided with a nanostructure or microstructure, similar to the surface 12a of the outer glass pane 12 in Fig. 5A and is also, as mentioned for surface 12a coated with a thin reflective coating.

Fig. 5C shows a further exemplary laminated glazing unit 10”, comprising an inner glass pane 11 and an outer glass 12 laminated to each other by means of a thin PVB sheet as thermoplastic interlayer 13. In this example, the inner surface 12a of the outer glass pane 12 has a diffusely reflective coating 12b. Such coating can contain nanoparticles or microparticles, as mentioned above with respect to Fig. 5B in a clear matrix.

Fig. 5D shows a further exemplary laminated glazing unit 10’”, comprising an inner glass plane 11 and an outer glass 12 which are bonded together by means of a thermoplastic interlayer 13, preferably a thin PVB sheet. In comparison with fig 5a, a thin reflective coating at the inner surface 12a is depicted as layer 15. Layer 15 might be a metallic coating.

Fig. 5E shows a further exemplary glazing unit 10^iv which, corresponding to a conventional laminated glazing unit, comprises an inner glass pane 11 and an outer glass pane 12 and an intermediate layer bonding the glass panes 11 , 12 together. Inner glass pane 11 and outer glass pane 12 may be clear glass or tinted glass. As in Fig. 5B the intermediate layer 13 is a multilayer comprising a first thermoplastic interlayer 13.1 , preferably a PVB sheet, and a second thermoplastic interlayer 13.2, preferably a PVB sheet and, embedded between the two thermoplastic interlayers (PVB sheets), e.g. a diffusely reflective sheet 14 of PET or PMMA. The diffusely reflective sheet 14 has a structured outer surface, which is coated with a thin reflective coating 15. The second thermoplastic interlayer 13.2 has a structured inner surface adhered to the reflective coating 15. Reference numerals

1 Vehicle glazing and display system

2 Vehicle

3 Roof 4, 4a, 4b Projector

6 Image on glazing unit

10; 10’; 10”, 10’”, 10^iv Vehicle compound glazing unit

11 Inner glass pane

12 Outer glass pane 12a Inner surface of outer glass pane

12b Coating on outer glass pane

13; 13.1 , 13.2 thermoplastic interlayers, preferably PVB sheets

14 Diffuse reflective sheet

15 Reflective coating 20, 20a, 20b Occupant

Claims

1. Vehicle glazing and display system (1) comprising a vehicle compound glazing unit (10; 10’; 10”, 10’”, 10^iv) comprising at least one layer or surface (12a; 12b; 14) which diffusely reflects incident light directed to the glazing unit from the interior of the vehicle (2) and having a maximum gain in the range of 0.1 to 0.8, preferably between 0.3 and 0.6 and an intrinsic viewing angle a for a real image element generated within the glazing surface of more than 60°, in a first direction and of more than 30°, in a second direction, perpendicular to the first direction, optionally a cover unit and at least two projectors (4, 4a, 4b) for projecting an image to the vehicle glazing unit or the cover unit to generate a real image in the plane of the glazing unit or the cover unit and wherein the vehicle compound glazing unit (10; 10’; 10”, 10”’, 10^iv) is a glass roof, wherein the vehicle compound glazing unit (10; 10’; 10”, 10”’, 10^iv) comprises an inner glass or plastic pane (11), an outer glass or plastic pane (12) and a diffusely reflective plastic sheet (14) laminated between the inner and outer glass or plastic panes and, wherein the diffusely reflective sheet (14) is an adhesive sheet or is embedded between two adhesive films (13.1 , 13.2) or layers, for bonding the inner glass or plastic pane (11) to the outer glass or plastic pane (12).

2. Vehicle glazing and display system (1) of claim 1 , further comprising a projector control unit connected to the at least two projectors and adapted to calibrate the projection of the image on a pixel base.

3. Vehicle glazing and display system (1) of claim 1 or 2, wherein the at least two projectors (4, 4a, 4b) are adapted to be arranged at opposite sides of the roof (3).

4. Vehicle glazing and display system (1) of claims 1 to 3, wherein the projection distance given as orthogonal direction to the glass surface, is between 2 cm and 60 cm.

5. Vehicle glazing and display system (1) of one of the preceding claims, wherein the at least three projectors (4), preferably four projectors (4), preferably six or eight projectors (4) are arranged in two rows along both longitudinal sides of the roof glazing surface.

6. Vehicle glazing and display system (1) of one of the preceding claims, wherein the projector (4) is adapted to provide an output flux of at least 1000 Lumen, preferably of 3000 Lumen or more.

7. Vehicle glazing and display system (1) of one of the preceding claims, adapted to generate, in its assembled state, a real image in the glazing surface with a horizontal extension of at least 25 cm, preferably between 40 cm and 60 cm.

8. Vehicle glazing and display system (1) of one of the preceding claims, the glazing unit comprising an inner glass or plastic pane (11), an outer glass or plastic pane (12) and an adhesive film (13) or layer for bonding the inner glass or plastic pane to the outer glass or plastic pane, wherein the inner surface (12a) of the inner or outer glass or plastic pane, contacting the adhesive film or layer, respectively, comprises a diffusely reflective coating (12b) or is treated to make the surface a diffuse reflector.

9. Vehicle glazing and display system (1) of one of the preceding claims, wherein the vehicle compound glazing unit (10; 10’; 10”, 10’”, 10^iv) comprises a diffusely reflective plastic sheet (14) comprising nanoparticles or microparticles within transparent substrate or wherein the inner surface (12a) of the inner or outer glass or plastic pane, contacting the adhesive film or layer, respectively, comprises a diffusely reflective coating (12b) and the coated glass or plastic pane (12) comprises nanoparticles or microparticles within a transparent substrate.

10. Vehicle glazing and display system (1) of claim 9, wherein the nanoparticles or microparticles are silica or polymer or liquid crystal particles.

11. Vehicle glazing and display system (1) of claim 10, wherein the nanoparticles or microparticles have spherical shape and/or are transparent or translucent.

12. Vehicle glazing and display system (1) of one of the preceding claims, wherein one surface of the diffusely reflective plastic sheet (14) comprises a random nanostructure or microstructure and, in particular, the other surface is polished.

13. Vehicle glazing and display system (1) of one of the preceding claims, wherein the diffusely reflective plastic sheet (14) comprises a PE, PET, TAC, PVB, PMMA or polycarbonate sheet.