DE102016225994A1 - Projection device for a motor vehicle and method for displaying a virtual image for a driver of a motor vehicle - Google Patents

Abstract

The invention relates to a projection device (1) for a motor vehicle having an image generation unit (2) for generating an image representation in an interior space (17) of the projection device (1), with imaging optics (14, 15) for aligning light of the image representation in the direction of a the interior (17) of the projection device (1) final cover (20), characterized in that on the cover plate (20) a hologram for deflecting the light on a reflective surface (10) in the motor vehicle outside the projection device (1) is provided ,

Description

State of the art

From the US 8,934,159 B2 is a head-up display is known in which a projection is made on a arranged on a windshield volume hologram. The volume hologram redirects the projected light toward a driver of a vehicle such that at a virtual position in front of the vehicle for the viewer, the projected image appears to float.

From the US 2008/0192358 A1 For example, a display device for a vehicle for projecting a virtual image is known. A projection device is arranged in an instrument panel of a vehicle. An interior of the projection device is closed by a cover plate, wherein the cover plate is wedge-shaped. On the one hand, the wedge-shaped design ensures that light can be projected onto a windshield of the vehicle such that a virtual image is visible to a driver. On the other hand, the wedge is arranged such that sunlight impinging on the wedge-shaped cover disk from the outside is deflected in the direction of a light trap, which is arranged adjacent to the wedge-shaped cover disk.

Disclosure of the invention

Advantages of the invention

The projection device according to the invention with the features of the independent claim has the advantage that a space reduction for a projection device in the vehicle can be achieved. Thus, it is either possible for a given virtual image distance in which an object is to float in front of a vehicle for a larger eyebox or a larger field of view of the driver or for a larger field of view of a head-up display a smaller volume of the projection device realize or with a constant volume of the projection device to realize a larger virtual image distance or a larger field of view or a larger eyebox or a larger field of view. This is achieved by integrating a hologram in a cover plate of the projection device. The absorber surface, and in particular the shape of the cover glass, prevents light rays from the sun from reaching the eyebox and thus the driver's eyes via the cover glass and the windscreen. In a hologram cover plate according to the invention also prevents sunlight that is mirrored at the bottom of the coverslip hologram element stack-air transition, the hologram reconstructed according to its optical function and passes through the windshield in the driver's eyes.

Furthermore, it is possible with the invention to replace corresponding alternative deflection elements, such as a mirror, to save space through the hologram. In addition, since the hologram is arranged on the cover disk, no additional component or carrier is required. In addition to a saving of construction volume for the optical element such as a mirror, it is also possible to save space required for the lighting itself also. Because the beam path can be compressed by deflecting. Since the deflection function for the hologram can be selected substantially freely, it is also possible to ensure a greater variability in the arrangement of other optical elements, such as further mirrors or the projection device in an interior of the projection device. Thus, an available volume can optionally be better utilized.

For use in motor vehicles, it is important to reduce the volume, in particular at that reflection surface, which specifies in which direction light exits from the projection device. Because at the point at which such a reflector is otherwise arranged, usually space-limiting elements such as a steering column or a steering column suspension are arranged in the vehicle. The position of these elements is usually predetermined and not very variable. By using a hologram on the cover plate of the projection device, however, a necessary variability in the representation of the optical elements and thus in the required volume can be achieved.

Further advantages of the invention will become apparent from the features specified in the dependent claims. Thus, it is advantageous to form the cover plate from a first plastic material and to form the hologram in a plastic film which is applied to the first plastic material. In a preferred embodiment, the first plastic material is polycarbonate, which can act as a carrier due to its stability. In this case, polycarbonate can be easily displayed in a desired shape via an injection molding representation. The second plastic material can then be applied in particular to the first plastic material acting as a carrier. Advantageously, the second plastic material is formed as a photopolymer film, in which the hologram can be easily structured by exposure.

In a further embodiment, the hologram is designed such that from the outside with respect to an interior of the projection device on the hologram incident light is led away from an interior of the projection device. As a result, stray light can be reduced, in particular sunlight or the light of street lamps, which enters an interior of the projection device and disturbs image formation that takes place in the interior of the projection device. In a further embodiment, it is advantageously provided that the light impinging on the cover disk from the outside is guided by the structuring of the hologram onto a light absorption surface, for example a black surface, adjacent to the projection apparatus. This avoids that this light is deflected in the direction of an observer and this could interfere.

In a further embodiment, the cover plate is curved. In this way, it is advantageously achieved that light incident from outside on the cover pane is led away by a viewer. Thus, incident sunlight is not mirrored on the windshield in the eyebox and thus in the driver's eyes. In this case, the hologram is advantageously arranged on a side facing the interior of the projection device. In such an embodiment, it can be achieved by the curved design of the cover disk that undesired scattering on the structures of the volume hologram is avoided, which function similar to a Bragg grating, by not even from the outside to the projection device incident light such as sunlight can reach the arranged on the inside of the cover disk hologram.

Advantageously, the hologram is designed to be easy to implement as a transmission volume hologram.

To further avoid the effects of stray light, a retarder and / or a polarizing film can additionally be arranged on the cover side.

A deflection by the hologram, which is particularly suitable for use in the vehicle, is achieved in particular when the light intended for transmission to a reflecting surface impinges on the hologram at an angle of 30 ° to 50 °, in particular from 35 ° to 45 ° to the normal , Incidence and diffraction angles of the hologram are defined when the hologram is picked up. These angles are to be selected according to the requirements for the representation and the installation position in the vehicle. At these angles, the diffraction efficiency of the hologram is then particularly high during reproduction. A transfer to other angle configurations is possible.

Corresponding advantages result for a method for displaying a virtual image.

list of figures

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

• 1 ein erstes Ausführungsbeispiel für eine erfindungsgemäße Ausführung einer Projektionsvorrichtung,
• 2 ein Ausführungsbeispiel für eine Ausführung einer Deckscheibe im Detail,
• 3 eine Darstellung für eine Beugungseffizienz eines Hologramms mit beispielhaften Einfallswinkel bei einer definierten Wellenlänge abhängig von einem Winkel auftreffender Lichtstrahlen,
• 4 ein zweites Ausführungsbeispiel für eine Projektionsvorrichtung.

Show it

• 1 a first embodiment of an inventive embodiment of a projection device,
• 2 an embodiment of an embodiment of a cover plate in detail,
• 3 a representation for a diffraction efficiency of a hologram with exemplary incident angle at a defined wavelength depending on an angle of incident light rays,
• 4 A second embodiment of a projection device.

Embodiments of the invention

In the 1 is a projection device 1 represented, which is arranged in particular in an instrument panel of a motor vehicle. In the projection device 1 is an image forming unit 2 arranged, which represents a real image, in particular in matrix form. The image generation unit 2 is designed, for example, as a liquid crystal display. Advantageously, the light of the image-forming unit has a narrow-band design, for example (+/- 0.5-1 nm) FWHM per color, for example in the case of RGB. Thus, the image source or a backlight unit can have LED or be laser-based.

Image signals stored in the imaging unit 2 are represented, the image forming unit 2 from a drive unit 3 transmitted. This is over a data connection 4 with a computing unit arranged in particular outside the projection device 5 connected. The arithmetic unit 5 in turn accesses via a vehicle data bus 6 on sensor units 7 . 8th back, which detect a vehicle condition or information from a vehicle environment, such as a speed sensor, an acceleration sensor or a distance sensor to a vehicle in front. In particular, indications of critical driving situations, but also status information of the vehicle can thus by means of the image generation unit 2 being represented. For a viewer in an interior of the vehicle, however, is an image representation of the image forming unit 2 not directly visible in direct optical connection. That of the imaging unit 2 outgoing light 9 is rather an optical deflection on a reflective surface 10 redirected in the vehicle. The reflective surface may, for example, the Windscreen, be applied to the windshield reflector or a reflective surface, which is well visible in the vehicle interior in front of the windshield of the vehicle. From the reflective surface 10 the light will be in the direction of the driver 11 diverted. When viewing the reflective surface 10 that seems to be from the imaging unit 2 illustrated picture 13 in front of the windshield 12 to float the vehicle. The picture 13 is therefore considered a virtual picture 13 designated.

That of the imaging unit 2 outgoing light 9 is deflected several times, with a beam path is folded. In the embodiment shown here, the light initially strikes a first mirror 14 and a second mirror 15 , The mirror 14 . 15 may be flat, spherical, aspherical or free-formed. From the second mirror 15 the light is on a cover disk 20 the projection device 1 diverted. The cover disk 20 is part of a housing 16 the projection device 1 , where the case 16 an interior 17 encloses, in particular, the image forming unit 2 is arranged.

The cover disk 20 in this case has a hologram, which of the second mirror 15 on the cover disk 20 occurring light 9 starting from the image forming unit 2 is deflected by the imaging function of the hologram depending on location such that the light in the direction of the reflective surface 10 is diverted. The cover disk 20 on the one hand fulfills a function of closing the interior 17 as part of the housing 16 the projection device, on the other hand, the function of a light deflector in which namely the light reflected from the second mirror light is deflected in a desired manner so that a driver by reflection on the reflecting surface 10 can perceive as a virtual image.

In the 2 is an embodiment of a cover plate 20 shown in detail. The cover disk 20 is here executed curved, the curvature convex in the interior 17 the projection device 1 intervenes. On a side facing the interior is a cover sheet substrate 21 provided, which is made for example of a polycarbonate. On the interior repellent side of the substrate 21 is a photopolymer layer 22 on the substrate 21 applied. In the photopolymer layer 22 a transmission volume hologram is imprinted.

In a further embodiment, the image generation device is embodied as a laser projection device in which a real image is imaged onto an imager surface. The use of a laser projection here has the advantage that laser light sources are narrowband. This ensures that light deflection through the hologram avoids any ambiguity in the image representation which could possibly result from a wavelength dependence of the light deflection function of the hologram.

To protect the photopolymer layer 22 Can on the the interior 17 opposite side of the photopolymer layer 22 a protective layer 23 be arranged, for. B. a so-called hard coating layer.

The photopolymer layer, which has a thickness of 6 μm to 200 μm, is coated on an optically transparent substrate, e.g. made of glass, polycarbonate, polyamide or TAC, applied with a particular material-dependent thickness of more than 60 microns or it is located between two optically transparent supports. To protect against scratches and wear, an optically transparent hard coating layer can additionally be applied to the resulting composite.

This results, for example, a following structure. Order is: polycarbonate cover glass - holographic element - polycarbonate substrate and optionally a hard-coating layer.

Further, by integrating the hologram in the cover disk, it is possible to adapt to various arrangements of the reflective surface by selecting a hologram. In particular, when using a windshield as a reflective surface, it is possible to make a simple way for the projection device to adapt to different types of vehicles, where usually the arrangement of the windshield with respect to the projection device is different. Thus, the otherwise same executed projection device can be used with different cover plate and thus with different hologram in different vehicle types. An adaptation of optical elements within the projection device itself is then no longer necessary.

In the 3 is the diffraction efficiency for a wavelength of visible light on a Y-axis 40 versus an angle of incidence to the normal of the hologram 41 plotted on the x-axis. This example shows a maximum at 40 ° and quite high values from 35 ° to 50 °. However, the diffraction efficiency at this wavelength is much lower for other angles. It is thus achieved that, on the one hand, light striking the cover disk at a desired angle and a defined wavelength is deflected efficiently. On the other hand, incident light at another angle, So stray light, not deflected in a similar way, but is lost. In particular, there is a reflection on the cover glass, so that disturbing light is not in the interior 17 the projection device 1 can reach and thus disturb a picture. If, however, light passes through, then due to the spectral dependence of the diffraction efficiency, this light is fanned out and therefore can only interfere with it to a limited extent. Because the fact that the cover glass spectrally fills in incident sunlight, it is achieved that not the complete, incident spectrum reaches an image-generating device.

In a further embodiment, it is also possible to form the diffraction function such that light striking the hologram from the outside is deflected in a preferred direction. In the 4 For this purpose, an example is shown, in the incident disturbing light, in particular sunlight, substantially unchanged by the windshield 12 passes through and onto the cover disk 20 a projection device 30 meets. In particular by means of the curved design of the cover plate 20 , the diffraction effects and in a further embodiment also by a prismatic configuration of the cover disk 20 , is formed by the so-called "glare trap" of cover plate and adjacent absorber 32 prevents the hologram from being reconstructed by incident sunlight reflected at the bottom of the stack, and can be distracting or even dazzling.

Furthermore, it is also possible that in a comparable arrangement of a reflective surface, a different position of the projection device is selected in the vehicle.

In a further embodiment, a cover plate can be combined with a hologram during manufacture with a polarization and / or a retarder film. So it is z. Example, possible to apply a film composite of the holographic film with a polarizing film on a glass or plastic carrier. This makes it possible to further suppress incident sunlight.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 8934159 B2 [0001]
• US 2008/0192358 A1 [0002]

Claims (9)

Projection device (1) for a motor vehicle with an image generation unit (2) for generating an image representation in an interior (17) of the projection device (1), with imaging optics (14, 15) for aligning light of the image representation in the direction of the interior (17 ) of the projection device (1) final cover plate (20), characterized in that on the cover plate (20) a hologram for deflecting the light on a reflective surface (10) in the motor vehicle outside the projection device (1) is provided. Projection device according to Claim 1 , characterized in that the cover plate (20) comprises a substrate (21) made of a first plastic material, in particular polycarbonate, and that the hologram is formed in a plastic film (22) made of a second plastic material, in particular a photopolymer. Projection device according to one of the preceding claims, characterized in that the hologram is formed such that in a predetermined direction from an outside of the projection device (1) incident on the hologram light is deflected such that it from the interior (17) of the projection device ( 1) is led away. Projection device according to Claim 3 characterized by a light absorbing surface (32) for absorbing the redirected light incident on the hologram in a predetermined direction from an outside of the projection device (1). Projection device according to one of the preceding claims, characterized in that the cover disc (20) is curved. Projection device according to one of the preceding claims, characterized in that the hologram is designed as a transmission volume hologram. Projection device according to one of the preceding claims, characterized in that a retarder and / or a polarizing film is arranged on the hologram and / or on the cover disk (20). Projection device according to one of the preceding claims, characterized in that the construction of imaging optics and cover plate is selected, the light for transmission to the reflective surface at an angle of 30 ° -50 °, in particular from 35 ° to 45 °, to the normal the hologram hits. Method for displaying a virtual image for a driver of a motor vehicle, wherein an image is generated in an interior space (17) of a projection device (1) and this image is directed by imaging optics (14, 15) in the direction of a cover plate (20) of the projection device (1). is deflected, wherein the light from a arranged on the cover plate (20) hologram is deflected in its direction onto a reflective surface (10) outside an interior of the projection device (1) in the vehicle.

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