DISPLAY DEVICE AND METHOD FOR PROJECTING DISPLAY INFORMATION IN A VEHICLE

Abstract

A display apparatus (10) configured to project display information in the field of view of a user (1) of a vehicle (80) with a dashboard (81) and a front window (82), comprising an imaging device (20) adapted to generate a light field (2) carrying the display information, a hologram device (30), which, in an arrangement below the field of view (4) of the user (1), is adapted for deflecting the light field (2) to the front window (82) and for generating a virtual image (3) of the display information in the field of view (4) of the user (1), and a control device (40) for controlling the imaging device (20), said hologram device (30) being configured for generating said virtual image (3) when said imaging device (20) is disposed above of the hologram device (30) and on a side of the hologram device (30) facing the field of view (4) of the user (1). A method for projecting display information in the field of view of a user (1) of a vehicle (80) is also described.

Claims

1. Display apparatus configured to project display information in the field of view of a user of a vehicle with a dashboard and a front window, comprising: an imaging device adapted to generate a light field carrying the display information, a hologram device which, in an arrangement below the field of view of the user, is adapted for deflecting the light field to the front window and for generating a virtual image of the display information in the field of view of the user, and a control device adapted to control the imaging device, wherein the hologram device is configured for generating the virtual image when the imaging device is arranged above the hologram device and on a side of the hologram device facing the field of view of the user.

2. Display apparatus according to claim 1, wherein the hologram device is configured for generating the virtual image with an arrangement of the imaging device above the dashboard of the vehicle.

3. Display apparatus according to claim 1, wherein the hologram device is configured for generating the virtual image with an arrangement of the imaging device on a rear-view mirror unit of the vehicle.

4. Display apparatus according to claim 1, wherein the imaging device includes a projector device with a projector arranged to generate the light field and with an intermediate screen configured to generate a real intermediate image of the light field emitted by the projector.

5. Display apparatus according to claim 4, wherein the intermediate screen includes a hologram formed for directionally directing the light field from the projector device to the hologram device.

6. Display apparatus according to claim 1, wherein the imaging device includes a liquid crystal screen adapted to generate the light field, said liquid crystal screen being provided with narrow band backlighting.

7. Display apparatus according to claim 1, wherein the hologram device includes a reflective holographic optical element forming a tilted off-axis mirror.

8. Display apparatus according to claim 7, wherein the hologram device includes at least one phase volume hologram representing the off-axis mirror.

9. Display apparatus according to claim 1, wherein the hologram device includes a broadband RGB hologram or a stack of multiple narrowband holograms adapted for different wavelengths.

10. Display apparatus according to claim 1, wherein the hologram device is configured for an exposed arrangement on a surface of the dashboard of the vehicle.

11. Display apparatus according to claim 10, wherein the hologram device is configured for an arrangement directly on the dashboard of the vehicle.

12. Display apparatus according to claim 1, wherein the hologram device has an anti-reflective surface.

13. Display apparatus according to claim 1, further comprising a temperature sensor device which is adapted to detect the temperature of the hologram device and is coupled to the control device, the control device being adapted to control the imaging device in dependency on the detected temperature of the hologram device in such a way that the light field generated by the imaging device is at least one of shifted and deformed in dependency on the detected temperature and a temperature-dependent change in the virtual image of the display information is compensated.

14. Display apparatus according to claim 13, wherein the temperature sensor device is adapted to detect the temperature in dependency on at least one diffraction feature of the hologram device.

15. Display apparatus according to claim 1, further comprising a wavelength sensor device which is adapted for detecting at least one emission wavelength of the imaging device and is coupled with the control device, wherein the control device is adapted to control the imaging device in dependency on the detected at least one emission wavelength of the imaging device in such a way that the light field generated by the imaging device is at least one of displaced and deformed in dependency on the detected at least one emission wavelength and a wavelength-dependent change in the diffraction direction of the hologram device is compensated.

16. Display apparatus according to claim 1, further comprising an image height adjustment device which is provided for adapting the position of the virtual image to the head height of the user.

17. Display for projecting display information in the field of view of a user of a vehicle, comprising the steps of: generating a light field carrying said display information with an imaging device, and deflecting the light field to a front window of the vehicle in the field of view of the user and generating a virtual image of the display information on the side of the front window facing away from the user with a hologram device which is arranged in a region below the field of view of the user, wherein the imaging device is disposed above the hologram device and on a side of the hologram device facing the field of view of the user.

18. Display according to claim 17, further comprising the steps of recording the temperature of the hologram device, and controlling the imaging device in dependency on the detected temperature of the hologram device.

19. Display according to claim 17, further comprising the steps of detecting at least one emission wavelength of the imaging device, and controlling the imaging device in dependency on the detected at least one emission wavelength of the projector device.

20. Display provided with a display apparatus according to claim 1.

Description

[0032] Further details of the invention are described below with reference to the attached drawings, which show in:

[0033] FIG. 1: a schematic perspective view of a preferred embodiment of the display apparatus in accordance with the invention from the vehicle driver's point of view;

[0034] FIG. 2: a schematic side view with an illustration of the beam path of a preferred embodiment of the inventive display apparatus; and

[0035] FIG. 3: a schematic cross-sectional view of a conventional display apparatus (prior art).

[0036] The invention is described in the following with exemplary reference to the application in a motor vehicle, wherein display information is presented to the driver of the motor vehicle with in his field of view, using the display apparatus. The invention is not limited to use in a motor vehicle, but can also be used in an aircraft or ship, for example. Features of the invention are described here in particular with reference to the arrangement of the hologram device and the imaging device and the beam path for generating the virtual image of the display information. Details of the fabrication of the hologram device and the generation of the hologram are not described, as these are known per se from prior art.

[0037] According to FIGS. 1 and 2, the preferred embodiment of the inventive display apparatus 10 comprises the imaging device 20 and the hologram device 30, which are arranged in the driver's compartment of a vehicle 80. The imaging device 20 is connected to a control device 40 which comprises, for example, a computer circuit and/or is integrated into the vehicle electronics. FIGS. 1 and 2 show schematically a part of the dashboard 81 and the front window 82 as well as the steering wheel 83 of the vehicle 80.

[0038] For the projection of display information in the field of view 2 of the driver 1, the light field 2, which carries the display information, is directed with the imaging device 20 from above onto the hologram device 30 and deflected with it to the front window 82 in the field of view 2 of the driver 1 so that the virtual image 3 of the display information is generated on the outside of the front window 82.

[0039] The imaging device 20 comprises, as shown schematically in FIG. 1, a laser projector 21, such as an RGB laser projector (e.g. of the type Pico-Projector), which contains laser sources, in particular laser diodes, with three different emission wavelengths in the red, green and blue spectral range. The laser sources are controlled by the control unit 40 in such a way that the light field 2 generated by the laser projector 21 represents the information to be displayed, e.g. a colour image and/or text content. The laser projector 21 is connected to the control device which provides the display information for the image to be displayed.

[0040] Furthermore, the imaging device 20 comprises an intermediate screen 22, e.g. in the form of a transmission hologram, the intermediate screen 22 directing the light field 2 in a directed manner from above onto the hologram device 30. The transmission hologram of the intermediate screen 22 is e.g. a broadband RGB hologram or a stack of several narrowband holograms designed for the respective emission wavelengths in the red, green and blue spectral range.

[0041] According to an alternative embodiment of the invention, the imaging device comprises a liquid crystal screen adapted to generate the light field 2 with a narrow band backlight source (not shown). In this embodiment, the projector 21 is replaced by the backlight source and the intermediate screen 22 is replaced by the liquid crystal screen. In this case, the liquid crystal screen receives the display information for the image to be displayed from the controller.

[0042] The hologram device 30 is arranged on the upper side of the dashboard 81, and it comprises a stacked structure, e.g. with a film carrier as carrier layer, a hologram layer containing the phase-volume hologram for deflecting the light field and for generating the virtual image 3, and a cover layer serving to protect and as antireflection coating of the hologram device. The individual layers can, for example, be made of transparent plastic and/or glass. The hologram layer is typically a plastic layer in which the hologram is inscribed.

[0043] The hologram layer of the hologram device 30 comprises a reflection hologram. This has the task of imaging the intermediate image of the imaging device 20 on the intermediate screen 22 on the windscreen in such a way that it is reflected exactly in the direction of the eyes of the driver 1. However, the light should only be emitted in the direction of the head in order to get by with as little light as possible. Therefore, the hologram geometry depends on the position of the imaging device, the head of the driver and the geometry of the windscreen. The position of the head of the driver 1 is presented by the “eye box” 5 (area where the eyes of the driver 1 with an average body height are located). Based on these parameters, the diffraction grating geometry of the reflection hologram is calculated using a procedure known per se. In order to generate the calculated grating structure in the hologram layer, a holographic film material is exposed with coherent and geometrically correspondingly shaped wave fronts with lasers of predetermined wavelengths. Exposure takes place in a manner known per se, preferably on a vibration-free optical table.

[0044] The size of the hologram device 30 determines the size of the virtual image 3 in the field of view of the driver 1 and is selected accordingly depending on the concrete application of the invention. The shape of the hologram device 30 can be convex or flat, whereby optionally a support is provided between the surface of the dashboard 81 and the hologram device 30 to adapt to the shape of the surface of the dashboard 81. In addition, as shown schematically in FIG. 2, the hologram device 30 can be provided with an opaque blocking screen 31 arranged between the hologram device 30 and the inside of the front window 82. The blocking screen 31 is configured to avoid unwanted direct reflections from the hologram device 30 to the front window 82.

[0045] The hologram of the hologram device 30 is configured in such a way that the virtual image 3 is generated on the outside of the front window 82 in the field of view 4 of the user 1. In order to avoid image errors due to variations in the temperature of the hologram device 30 and/or the operating temperature of the imaging device 20, the inventive display apparatus 10 is provided with a temperature sensor device 50 and/or a wavelength sensor device 60 (shown schematically in FIG. 1). The temperature sensor device 50, e.g. a thermocouple, measures the temperature of the hologram device 30. Based on an output signal of the temperature sensor device 50, the control device 40 controls the imaging device 20 in such a way that temperature-dependent displacements of the virtual image 3 are compensated.

[0046] The wavelength sensor device 60 comprises a CCD chip which is arranged downstream of the intermediate screen 22 and with which a part of the light field 2, such as a single pixel in the real intermediate image, is detected on the transmission hologram of the intermediate screen 22. With the control device 40, the light field 2 of the imaging device 20 is shifted in such a way that the considered pixel is detected with the CCD chip at a desired target position.

[0047] FIG. 2 further schematically illustrates an optional image height adjustment device 70 to which the imaging device 20 is coupled. With the image height adjustment device 70, the imaging device 20 can be shifted in such a way that the virtual image 3 is presented at the desired viewing height in the field of view 4 of the driver 1 (corresponding to his “eye box” 5). The adjustment of the image height is achieved, for example, by shifting the imaging device 20. The imaging device 20 may, for example, be displaceable on a rail on the rear-view mirror unit 84 and the image height adjustment device 70 may be designed for manual displacement of the imaging device 20 on the rail.

[0048] The features of the invention disclosed in the above description, drawings and claims may be relevant to the realisation of the invention in its various forms, either individually or in combination or subcombination.