Holographic display device with two displays for widescreen display

Abstract

The invention relates to a display device (1) comprising a display arrangement (10), a lens (2) and a projection element (9) with a display area, the projection element (9) comprising holographic optical elements. The display arrangement (10) comprises at least two displays (11, 12) which are arranged radially offset with respect to one another in relation to an optical axis (14) of the display device (1) in the beam path (3, 4) between the display arrangement (10) and the lens (2), wherein the beam paths (3, 4) starting from the at least two displays (11, 12) extend jointly through the lens (2) and generate a composite image on the display area from at least two partial images arranged partially next to one another.

Description

[0001] Holographic display device with two widescreen displays

[0002] The present invention relates to a display device, a use of the display device, and a vehicle. The display device comprises a projection element which includes holographic optical elements.

[0003] In everyday life, especially in public infrastructure, digital display devices are state of the art and indispensable. Furthermore, the number of display devices is constantly increasing. The associated resource and energy requirements are considerable. Therefore, there is a drive to utilize previously unused glass surfaces as display devices. Suitable methods for functionalizing glass panes using volume holographic optical elements are already known and in use. State-of-the-art technology in this area is disclosed, for example, in DE 10 2021 105 830 A1 and DE 10 2015 101 687 A1.

[0004] Several challenges arise during the development of a transparent, widescreen holographic display device for applications such as automotive, based on DLP (Digital Light Processing) projection systems. DLP projection technology generates images by modulating a digital image onto a light beam, which is then broken down into pixels, for example, using a Digital Micromirror Device (DMD). Currently available DMD systems are limited in size, resolution, and aspect ratio. Furthermore, there are additional limitations regarding the availability of automotive-approved DMD systems. Typically, such systems are limited in their resolution, and therefore their performance.Consequently, beyond a certain required display width or width of the display area, it becomes necessary to use multiple projection systems to assemble the individual fields into a single large field (keyword: "image stitching"). In typical applications, several systems are used, which increases costs and resource consumption.

[0005] Against this background, the object of the present invention is to provide an advantageous display device. Further objects are to provide an advantageous use of the display device and an advantageous vehicle.

[0006] The aforementioned problems are solved by the features of the independent claims. The dependent claims contain further advantageous embodiments of the invention.

[0007] The display device according to the invention, e.g., an image display device or projection device, comprises a display arrangement, a lens, preferably only a single lens, and a projection element or display element, e.g., in the form of a screen, with a display area, preferably a display surface. The projection element or display element, in particular the display area or the display surface, comprises holographic optical elements. The holographic optical elements preferably act as diffusers, but can also be designed for guiding light beams and / or for correcting aberrations.

[0008] The display arrangement comprises at least two displays, which are arranged radially offset from each other (i.e., "off-axis") with respect to an optical axis of the display device in the beam path between the display arrangement and the lens. Furthermore, the beam paths from the at least two displays pass together through the lens and generate a composite image in the display area from at least two partially adjacent partial images. The beam paths from the at least two displays can pass together through the lens in such a way that the beam paths intersect and / or are radially offset (off-axis) with respect to the optical axis of the lens.

[0009] The composite image can be generated in a so-called image field. The image field can be arranged in an eyebox or on the display surface. In other words, using the display device according to the invention, beams of light from a first display (or at least two displays) are projected, at least partially, onto a display surface alongside beams of light from a second display (or at least two displays) and combined to form a single image. With a transparent display area, the image field typically lies on the holographic display surface and can be viewed with the eye or a camera system. However, it is possible to design the holographic optical elements of the display surface in such a way that the image projected onto the display surface can only be viewed from specific solid angle areas. These areas are called "eyeboxes."

[0010] The display device according to the invention has the advantage of providing a high-quality widescreen display in a simple and cost-effective manner. By using two displays in conjunction with only one lens, fewer resources are required compared to using several separate projectors, and the aberrations typically occurring in widescreen imaging are significantly reduced compared to using only one display. The display device according to the invention can be used in many contexts, for example in the home technology sector and in public infrastructure, such as on facades, preferably glass facades, of buildings, in the transport sector, i.e., on and in vehicles of all kinds, and generally in connection with windows, partition walls, doors, display boards, etc.In a preferred embodiment, the display device for folding and / or aligning the beam paths for each display comprises at least one optical arrangement, e.g., in the form of a mirror or reflection arrangement, which is arranged in the respective beam path between the lens and the projection element and which includes at least one reflective optical element. In other words, the display device thus comprises a total of at least two optical arrangements for folding and / or aligning the beam path, wherein a first optical arrangement is arranged in the beam path of a first display of the at least two displays, and a second optical arrangement is arranged in the beam path of a second display of the at least two displays.The described optical arrangements enable, on the one hand, individual beam guidance of a plurality of beam paths offset from each other, in particular radially offset with respect to an optical axis of the lens, arranged or running with possible correction of aberrations, and on the other hand, a targeted and precise joining of the partial images to form a complete image with widescreen format.

[0011] Preferably, the optical arrangement for folding and / or aligning the beam path comprises at least one reflective optical element having a curvature. This curvature can be aspherical and / or cylindrical. The corresponding curvatures enable targeted beam guidance and shaping, as well as aberration correction. In particular, the light paths or beam paths can be shortened, and a larger angle of projection onto the image plane is possible.

[0012] At least one display can be designed as a DMD display and / or at least one display can be designed as an LCoS display or liquid crystal on silicon display (LCoS - Liquid Crystal on Silicon).

[0013] The at least two displays can be positioned and / or aligned independently of each other. In particular, the at least two displays can be designed to tilt independently of each other with respect to an optical axis of the lens and / or be arranged at a tilt. This allows the use of the so-called Scheimpflug principle. Thus, a tilted image plane or image field can be created by tilting the display. This is particularly advantageous in connection with applications on curved and / or tilted projection surfaces, such as windshields.

[0014] The Scheimpflug condition for producing a sharp image of an inclined object plane requires that the image plane be inclined such that its line of intersection with the image-side principal plane is at the same distance from the optical axis as the line of intersection between the object plane and the object-side principal plane. This means that the object plane, the objective plane, and the image plane must intersect approximately in a straight line.

[0015] For example, the at least two displays can each have a radiating surface with a surface normal, and the mean radiating direction of each display can form a tilt angle with the surface normal. This tilt angle can be greater than 5 degrees, for example. The tilt angle can be selected appropriately depending on the requirements of the specific application.

[0016] In a preferred version, the projection element comprising the holographic optical elements is designed to be at least partially transparent. This enables diverse applications in the transportation sector, specifically in connection with viewing windows of all kinds, and in public infrastructure.

[0017] The projection element, in particular the display surface or display area, can be curved. For example, the projection element can be a viewing window, such as a vehicle windshield. In this context, the display device according to the invention provides aberration-reduced or aberration-free imaging on the curved surface. Preferably, the beam paths are designed such that all principal beams, i.e., the principal beams of the at least two displays, have the same exit pupil position, meaning they originate from the same exit pupil or from superimposed exit pupils. This allows the holographic optical elements (HOEs) to be constructed with a simple structure. This, in turn, is advantageous in terms of cost and resources.

[0018] In another variant, the display device can be designed to partially superimpose the partial images in a target field or image field, e.g. in the display area or on the display surface, by mechanical means, i.e. by suitable positioning and / or calibration and / or adjustment of the optical components in the beam path, e.g. by suitable tilting of the displays relative to each other, and / or by optical means, e.g. additional lenses in the beam path.

[0019] The display device can be designed to align the partial images in an area where they overlap using digital image processing. This has the advantage that the transition between the partial images is invisible to the user, thus creating a high-quality widescreen image.

[0020] Preferably, the display device is designed to generate an image composed of the partial images, i.e., a complete image, with an aspect ratio of at least 18:5.

[0021] The vehicle according to the invention comprises a previously described display device according to the invention. The vehicle according to the invention has the features and advantages described in connection with the display device according to the invention. The vehicle can be a motor vehicle, ship, aircraft, or rail vehicle. The motor vehicle can be a passenger car, truck, bus, minibus, motorcycle, or moped. The aircraft can be an airplane or a helicopter.

[0022] In the context of the use according to the invention, a display device according to the invention is used as a head-up display and / or as a component of a facade and / or a window and / or a door and / or a wall of a building and / or a public infrastructure object, or generally in connection with a glass pane as a display. The use according to the invention has the advantages already described above in connection with the display device according to the invention.

[0023] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying figures. Although the invention is illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived from them by a person skilled in the art without departing from the scope of protection of the invention.

[0024] The figures are not necessarily detailed or to scale and may be enlarged or reduced to provide a better overview. Therefore, the functional details disclosed here are not to be understood as limiting, but merely as an illustrative basis to guide those skilled in this field of technology in using the present invention in a variety of ways.

[0025] The expression "and / or" used here, when used in a series of two or more elements, means that each of the listed elements can be used alone, or any combination of two or more of the listed elements can be used. For example, when describing a composition containing the components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0026] Fig. 1 schematically shows a first part of the beam path through a display device according to the invention in a perspective view.

[0027] Fig. 2 schematically shows a second part of the beam path through a display device according to the invention in a perspective view.

[0028] Fig. 3 schematically shows the beam path through a display device according to the invention in a perspective view.

[0029] Fig. 4 schematically shows the beam path through a display device according to the invention in a further variant in a side view.

[0030] Fig. 5 schematically shows the beam path through a display device according to the invention in a further variant in a side view.

[0031] Fig. 6 schematically shows the beam path through a display device according to the invention in a further variant in a top view.

[0032] Fig. 7 schematically shows a vehicle according to the invention in the form of a block diagram.

[0033] The structure of a display device 1 according to the invention is explained below with reference to Figures 1 to 3. Figure 1 shows a first part or a first channel of the beam path 3, Figure 2 shows a second part or a second channel of the beam path 4, and Figure 3 shows the entire beam path 3, 4.

[0034] The display device 1 according to the invention comprises a display arrangement 10, a lens 2, and a projection element 9. The display arrangement 10 includes a first display 11 and a second display 12. The first display 11 and the second display 12 are radially offset from each other with respect to an optical axis 14 of the lens 2, i.e., arranged side by side or off-axis to each other. The first display 11 and / or the second display 12 can be configured as a DMD display or an LCoS display. For each display 11 or 12, an individual position adjustment with respect to a tilt angle with respect to the optical axis 14 can be provided. By tilting the displays 11 and 12 accordingly, a "Scheimpflug correction," i.e., beam guidance according to the Scheimpflug principle, can be achieved.

[0035] Between the lens 2 and the projection element 9 is in the

[0036] Beam path 3 starting from the first display 11 an optical

[0037] Arrangement 5 is arranged for folding and / or shaping the beam path 3. Between the lens 2 and the projection element 9, in the

[0038] Beam path 4 starting from the second display 12 an optical

[0039] Arrangement 6 is arranged for folding and / or shaping the beam path 3 and is identical in design to optical arrangement 5. Optical arrangements 5 and 6 are arranged radially offset from each other with respect to the optical axis 14, for example, with respect to the display 11 or 12 belonging to the respective beam path on the opposite side of the optical axis 14. Optical arrangements 5 and 6 each comprise two reflective optical elements 7 and 8, for example, mirrors, which are arranged one behind the other in beam path 3 or 4. The folding mirrors 7 and 8 not only fold beam path 3 or 4, but also simultaneously align the two individual fields. Thus, a "large" composite image of the two individual channels is produced in the target field.Using the display device 1 according to the invention, a widescreen image, for example with an aspect ratio of 18:5 or more, can be projected onto the projection element 9. The projection element 9 comprises a display surface. The projection element 9 also includes holographic optical elements which can act as diffusers. The projection element 9, in particular the display surface, can be at least partially transparent. This opens up a wide range of applications, e.g., in the transport sector or in public infrastructure, as already described in detail above.

[0040] In the area of ​​projection element 9 where beam paths 3 and 4 partially overlap, the image data can be aligned to create a seamless image without a visible transition between the two partial images. For this purpose, each display 11 or 12 is individually integrated into the display device 1 with its own orientation and position to achieve optimal imaging. The final alignment of the projected individual fields to create a "seamless" overall image is performed, for example, digitally through image preprocessing. This means that the image data can be pre-processed, i.e., adjusted for brightness and / or contrast and positionally corrected, before being transmitted.

[0041] Figures 4 and 5 show further variations of beam paths through a display device according to the invention. The variations shown differ in the design of the reflective optical elements 7 and 8 of the optical arrangements 5 and 6, respectively. In the variation shown in Figure 4, the optical elements 7 and 8 are designed as plane mirrors, while in the variation shown in Figure 5 they have a curvature, for example, a spherical, aspherical, or cylindrical curvature. This improves the image quality. Furthermore, the angle of incidence of the light onto the projection element 9 or into the image plane can be increased.

[0042] Figure 6 shows a variant of a beam path of a display device 1 according to the invention for an application in connection with a curved viewing window, for example, a windshield 9. In connection with the HOE of the projection element 9, in the example shown a windshield, it is always advantageous if all principal rays originate from the same exit pupil position 13. This allows the HOE to be constructed with a simple structure. If the two displays 11 and 12 use the same lens, they also have the same exit pupil. This is the case, for example, in the variants shown in Figures 1 to 5.

[0043] When the HOE is integrated into a curved disk 9, e.g., a vehicle windshield, the curvature of the projection element 9 can be compensated by tilting the displays 11 and 12 relative to each other and with respect to the optical axis 14 of the lens, as shown by way of example in Figure 6. This tilting can be achieved by exploiting the Scheimpflug principle, in particular the Scheimpflug condition, in combination with aberration correction, e.g., by adjusting the Petzval field curvature. Even simple components such as spherical lenses and plane mirrors can be used to effectively compensate for a complex curvature of the projection element 9.

[0044] Figure 15 schematically shows a vehicle according to the invention in the form of a block diagram. The vehicle 15 comprises a display device 1 according to the invention, for example, a display device 1 as previously described with reference to Figures 1 to 6. As already described, the vehicle 15 can be a motor vehicle, an aircraft, a rail vehicle, or a ship. The present invention offers a high-quality and robust widescreen display for these applications, for example, also in the form of a head-up display. List of reference numerals:

[0045] 1 Display device

[0046] 2 Objective 3 Beam path

[0047] 4 Beam path

[0048] 5 optical arrangement

[0049] 6 optical arrangement

[0050] 7 reflective optical element 8 reflective optical element

[0051] 9 Projection element

[0052] 10 Display arrangement

[0053] 11 Display

[0054] 12 Display 13 Exit pupil

[0055] 14 optical axis of the lens

[0056] 15 vehicles

Claims

Patent claims 1. Display device (1) comprising a display arrangement (10), a lens (2) and a projection element (9) with a display surface, wherein the projection element (9) comprises holographic optical elements, characterized in that the display arrangement (10) comprises at least two displays (11, 12) which are arranged radially offset from each other in the beam path (3, 4) between the display arrangement (10) and the lens (2) with respect to an optical axis (14) of the display device (1), and wherein the beam paths (3, 4) originating from the at least two displays (11, 12) pass together through the lens (2) and generate a composite image on the display surface from at least two partially adjacent partial images.

2. Display device (1 ) according to claim 1 , characterized in that the display device (1 ) for folding and / or aligning the beam paths (3, 4) per display (11 , 12) comprises at least one optical arrangement (5, 6) which is arranged in the respective beam path (3, 4) between the lens (2) and the projection element (9) and which comprises at least one reflective optical element (7, 8).

3. Display device (1 ) according to claim 2, characterized in that the optical arrangement (5, 6) for folding and / or aligning the beam path (3, 4) comprises at least one reflective optical element (7, 8) which has a curvature.

4. Display device (1 ) according to one of claims 1 to 3, characterized in that at least one display (11 , 12) is designed as a DMD display and / or at least one display (11 , 12) is designed as an LCoS display.

5. Display device (1 ) according to one of claims 1 to 4, characterized in that the at least two displays (11 , 12) are arranged to be positioned and / or aligned independently of each other.

6. Display device (1 ) according to claim 5, characterized in that the at least two displays (11 , 12) are designed to be tiltable and / or tilted independently of each other with respect to an optical axis (14) of the lens (2).

7. Display device (1) according to one of claims 1 to 6, characterized in that the at least two displays (11, 12) each have a radiating surface with a surface normal and the mean radiating direction of the respective display (11, 12) includes a tilting angle with the surface normal.

8. Display device (1 ) according to one of claims 1 to 7, characterized in that the projection element (9) is designed to be at least partially transparent.

9. Display device (1 ) according to one of claims 1 to 8, characterized in that the projection element (9) is curved.

10. Display device (1 ) according to one of claims 1 to 9, characterized in that the beam paths (3, 4) are designed such that all main beams have the same exit pupil position (13).

11. Display device (1 ) according to one of claims 1 to 10, characterized in that the display device (1 ) is designed to partially superimpose the partial images in a target field by mechanical and / or optical means.

12. Display device (1 ) according to one of claims 1 to 11 , characterized in that the display device (1 ) is designed to align the partial images in an area where the partial images overlap by means of digital image processing.

13. Display device (1 ) according to one of claims 1 to 12, characterized in that the display device (1 ) is configured to generate an image composed of the partial images with an aspect ratio of at least 18:

5.

14. Vehicle (15) comprising a display device (1) according to any one of claims 1 to 13.

15. Use of a display device (1) according to any one of claims 1 to 13 as a head-up display and / or component of a facade and / or a window and / or a door and / or a wall of a building and / or a public infrastructure object.

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