Head-up display with liquid crystal lens for specifically inclining an image plane

Abstract

One aspect of the invention relates to a head-up display (5) for a vehicle (1), having an image generator (6) and an optical device (10) by means of which an image generated by the image generator (6) can be projected in an image plane, and having an image plane inclination device (7), by means of which the image plane (8) can be inclined, wherein the image plane inclination device (7) has a liquid crystal lens (9), which is arranged in the optical path (13) between the image generator (6) and an optical element (11, 12) of the optical device (10), and having a control unit (14) for controlling the liquid crystal lens (9) in order to change the refractive index of the liquid crystals of the liquid crystal lens (9) such that light beams (15, 16, 17) of an image of the image generator (6) have different optical path lengths, such that the image plane (8) can thereby be individually inclined.

Description

[0001] Head-up display with liquid crystal lens for specific inclination of an image plane

[0002] One aspect of the invention relates to a head-up display for a vehicle. The head-up display has an image generator and an optical device with which the image generated by the image generator can be projected onto an image plane. The head-up display furthermore has an image plane tilting device with which the image plane can be defined relative to a reference plane and tilted as desired. An image plane in which the image from the image generator is sharply displayed for a viewer can be tilted by an image plane tilting device. This is known, for example, in head-up displays with augmented reality, so-called AR head-up displays. This makes the contact-analogous representation of an image appear even more accurate and realistic compared to the also perceivable reality.

[0003] However, with known image plane tilt devices, the inclination of the image plane is fixed. This limits the realistic representation of an image in a reality also perceived by an observer.

[0004] It is an object of the present invention to provide a head-up display in which a more needs-based representation of the image in an image plane is achieved in comparison to the surrounding reality.

[0005] This object is achieved by a head-up display having the features of claim 1.

[0006] One aspect of the invention relates to a head-up display for a vehicle. The head-up display has an image generator and an optical device with which the image generated by the image generator can be projected onto an image plane. The head-up display furthermore has an image plane tilting device with which the image plane is defined relative to a reference plane and can be tilted as desired. An image plane in which the image generator's image is sharply displayed for a viewer can be tilted using an image plane tilting device. This is known, for example, in head-up displays with augmented reality, so-called AR head-up displays. This makes the contact-analog representation of an image appear even more accurate and realistic compared to the also perceivable reality. The image plane tilting device is designed in particular to dynamically change the inclination of the image plane. This advantageously allows the inclination of the image plane to be individually changed.In particular, the tilt is not only possible in various discrete steps or angles. Rather, it advantageously allows the image plane to be continuously changed, especially dynamically.

[0007] In particular, the image plane tilting device is provided with at least one liquid crystal lens. Such a component enables highly variable, rapid, and flexible changes in the inclination of the image plane. This enables a particularly needs-based and situation-adapted tilted positioning of the image plane. This achieves particularly precise adaptation to the respective environment, which an observer can also perceive together with the image. The realistic display scenario with the projected image and the surroundings is thus made even more realistic.

[0008] The liquid crystal lens is arranged in an optical path between the imager and an optical element of the optical device. Furthermore, the head-up display, in particular the image plane tilting device, has a control unit configured to control the liquid crystal lens to change the refractive index of the liquid crystals of the liquid crystal lens such that light rays from the imager have different optical path lengths, allowing the image plane to be individually tilted. It is precisely this type of embodiment of an image plane tilting device with at least one individual liquid crystal lens controllable by a control unit that allows highly dynamic and thus very rapid changes in the image plane and its tilt to be generated.This allows a very advantageous and dynamic adaptation of the image plane, particularly to the surroundings that are also being perceived, even when the environment changes quickly while the vehicle is moving.

[0009] In one embodiment, the liquid crystal lens is a matrix lens. This has several lens cells arranged in a matrix. By constructing the liquid crystal lens in this way, several lens cells are arranged directly next to one another in an ordered pattern. By constructing the liquid crystal lens in this way as a matrix lens, the individual lens cells can be controlled individually, thus further increasing the flexibility and situation-adapted adjustment of the inclination of the image plane. In one embodiment, the lens cells can be individually controlled using the control unit to change the refractive index. Thus, virtually each lens cell can be individually controlled by the control unit, and thus each lens cell can individually change its refractive index.

[0010] In the embodiment in which the liquid crystal lens is a matrix lens and whose lens cells are at least partially individually controllable, it is particularly advantageous that separate regions of the matrix can have different refractive indices. This advantageously results in different regions or elements to be displayed in the projected image of the head-up display, such as arrows or symbols, being able to have different projection distances or inclinations and preferably being able to be changed dynamically. This significantly improves the information presentation for the user.

[0011] In one embodiment, the matrix can have at least 4 x 4 lens cells. However, it is also possible for the number of rows and / or columns of this matrix arrangement to have more, in particular significantly more, than four lens cells. In particular, any configuration of a matrix arrangement is disclosed in which, starting from four lens cells, the number of lenses is increased by at least one additional lens cell. In this context, asymmetric ratios of the number of rows and columns can also be realized.

[0012] In one embodiment, the liquid crystal lens has a multilayer structure. This structure is configured such that at least two electrical voltages can be tapped from this multilayer structure, so that the refractive index of the liquid crystal lens can be changed by adjusting the electrical voltages and / or the voltage ratio between the two voltages. In particular, this is the case for each lens cell in an embodiment in which the liquid crystal lens is designed as a matrix lens.

[0013] By arranging the liquid crystal lens in this way, in which at least two different electrical voltages can be adjusted and tapped, the operation of the liquid crystal lens for adjusting the inclination of the image plane can be very advantageously configured. This also enables very flexible and dynamic adjustments, leading to very diverse and specific refractive index profiles of the liquid crystal lens.

[0014] Preferably, a structure of a liquid crystal lens can be designed such that, viewed in the vertical direction of the head-up display, it is delimited in the upper region of the layer stack and / or in the lower region of the layer stack by a closure element, for example a glass element, in particular glass plates. In between, a structure can be provided which, starting from a glass plate, has an electrode, such as an indium tin oxide electrode (ITO electrode). An insulation layer can be formed subsequently, in which case a second electrode, for example an indium tin oxide electrode, can be formed subsequently. It is possible for a buffer layer to be formed subsequently in the further layer structure. An alignment layer can be formed subsequent to this buffer layer. Furthermore, a polymer layer or polymer layer can then be formed.Preferably, at least one liquid crystal unit can be formed in the layer stack following this polymer layer. It is also possible for a layer of thermoplastic, for example, polyvinyl alcohol, to be formed following the liquid crystal unit. An electrode, for example, an indium tin oxide electrode, can be formed following such a possibly present layer of thermoplastic, and the aforementioned second final layer, in particular the glass plate, can then be formed following this.

[0015] In one embodiment, the liquid crystal lens is arranged separately from the imager. It is arranged in the optical path between the imager and a folding mirror of the optical device, which forms an optical element. Thus, the liquid crystal lens is arranged directly in a first section of the optical path, starting from the imager. This allows the image generated by the imager to be particularly advantageously influenced by this liquid crystal lens, particularly with regard to the inclination of the image plane.

[0016] In another embodiment, the imager and the liquid crystal lens can be arranged in a common imaging unit. For example, such an imaging unit can be a digital image projector. In such an embodiment, the imager and the liquid crystal lens are then integrally formed and arranged in such an image projector. In one embodiment, the reference plane is oriented relative to an object arranged externally to the head-up display. In particular, this externally arranged object is a road surface to which the reference plane is specifically oriented. The road surface is, in particular, the surface on which a vehicle having the head-up display is moving.Such an assignment of the reference plane is particularly advantageous when the inclination of the image plane needs to be adjusted and oriented as needed in relation to the also perceived real environment. This is because this relationship of the reference plane to precisely this specific road surface allows a particularly precise inclination of the image plane to be set, adapted to the situation. This means that the then specific inclination of the image plane allows the observer's overall perception of the image and the additional real environment to be perceived as a single unit of information, and the image is recognized as being present in the actual environment in a particularly realistic way, or is perceived accordingly.

[0017] In one embodiment, the reference plane is a plane oriented relative to a road surface. In particular, it is a plane oriented perpendicular to the road surface on which a vehicle having the head-up display is currently located.

[0018] In one embodiment, the angle of inclination of the image plane relative to the reference plane is adjustable between greater than 0° and less than or equal to 80°. This also allows for a highly dynamic and continuous large angular interval within which the image plane can be tilted. This is made possible in particular by the liquid crystal lens. The quickly and diversely adjustable refractive indices, particularly of the individual lens cells of the liquid crystal lens, allow the aforementioned angles to be precisely adjusted across the entire angular interval.

[0019] In one exemplary embodiment, an angle of inclination of the image plane relative to the reference plane can be dynamically adjusted depending on at least one environmental parameter of the area surrounding the head-up display and / or depending on a vehicle parameter of the vehicle having the head-up display, and / or depending on the image to be displayed and / or depending on a traffic situation occurring in the area surrounding the vehicle having the head-up display. These parameters in particular allow the image plane to be quickly and accurately adapted to the actually perceivable environment, resulting in a particularly realistic representation of the image relative to the also perceived environment. This is particularly advantageous for head-up displays with augmented reality, which display the image in a contact-analog manner.

[0020] In one embodiment, a refractive index profile is set or provided by the control unit to adjust the inclination of the image plane, wherein the refractive index is lower in an upper region of the liquid crystal lens than in a lower region, viewed in the vertical direction of the head-up display. This is a further very advantageous embodiment, as it ensures that, viewed in the vertical direction, this upper region of the image is further away from the reference plane than the lower region. This allows the image plane to be tilted away from the observer, starting from a lower region and ending in an upper region. In this regard, the image plane can be embedded or inserted into the also perceived environment in a particularly advantageous and needs-based manner.In particular, it is possible for horizontal rows of lens cells, for example, to be controlled equally, so that they each produce the same refractive index. With respect to the columns of this matrix arrangement of lens cells of the liquid crystal lenses, this refractive index can vary from top to bottom.

[0021] In one embodiment, the refractive index profile has at least one non-linear characteristic curve. In particular, this allows a lower refractive index to be set in the upper region of the liquid crystal lens than in the lower region, with respect to the vertical direction of the head-up display, whereby this is predetermined by the non-linear characteristic curve. This allows the aforementioned advantages to be achieved to a particularly high degree.

[0022] It is also possible for the refractive index profile to have different characteristics, particularly different non-linear characteristics, for different eye boxes. This also allows for the fact that, despite different eye boxes and thus different observer orientations, a particularly suitable and appropriate inclination of the image plane can be adjusted to meet specific needs.

[0023] In one embodiment, the control unit is configured to control the liquid crystal lens to generate a refractive index profile such that optical aberrations, in particular astigmatism, of the optical device can be reduced, in particular compensated. As a result, the head-up display is functionally enhanced by the liquid crystal lens. Not only the inclination of the image plane, but also aberrations can be corrected. This enables the accuracy of the image display and a particularly realistic projection into the surroundings, which are also perceived by an observer.

[0024] In one embodiment, the head-up display is an augmented reality head-up display. This may also be referred to as an AR head-up display.

[0025] A further aspect of the invention relates to a vehicle with a head-up display according to the above-mentioned aspect or an advantageous embodiment thereof.

[0026] The liquid crystal unit of the liquid crystal lens preferably has semantic crystals. It is precisely the liquid crystal lens that makes it possible to generate a wide variety of refractive index profiles in a particularly defined and finely structured manner. These can be the same or different with regard to the respective local refractive index at a point on the liquid crystal lens. This can, for example, make it possible to generate a refractive index profile which has a higher refractive index in the center than at the edge. It is also particularly advantageous in this context that a wide variety of refractive index profiles can be set precisely through the structure of the liquid crystal lens, in particular also of the liquid crystal unit, in particular also with regard to the thickness and / or the number of liquid crystal units, in particular layers or layers.It is therefore also possible for a lens with a specific index profile to be adjustable from bottom to top, in particular with a refractive index that varies from bottom to top. This enables the individual inclination of the image plane in a particularly efficient and effective manner. By changing the refractive index of the liquid crystal lens using control signals, in particular the electrical voltage applied to the liquid crystal lens via control signals from the control unit, real-time changes to the inclination of the image plane can also be made. It is also possible to create different discrete image planes at different distances in this way. Furthermore, this also enables a gradual optical path in one direction to achieve this inclination of the image plane.

[0027] Embodiments of the invention are explained in more detail below with reference to schematic drawings. In the drawings: Fig. 1 shows a schematic representation of an embodiment of a head-up display according to the invention as a schematic representation in an embodiment of a vehicle according to the invention shown in partial components;

[0028] Fig. 2 is a schematic representation of an embodiment of a liquid crystal lens as may be part of a head-up display according to Fig. 1;

[0029] Fig. 3 is a schematic representation of a structure of a liquid crystal lens or a lens cell of a matrix-like liquid crystal lens;

[0030] Fig. 4 shows an embodiment of a diagram in which a characteristic curve of a refractive index is shown that can be adjusted with the head-up display; and

[0031] Fig. 5 is a diagram according to Fig. 4, in which several different characteristic curves for refractive indices are shown depending on different eye boxes.

[0032] In the figures, identical or functionally identical elements are provided with the same reference symbols.

[0033] Fig. 1 shows a schematic representation of a vehicle 1 in partial components. The vehicle 1 has a windshield 2. An eye 3 of a vehicle occupant, in particular a driver of the vehicle 1, is shown schematically. In this regard, an eye box is thus also characterized. With the eye 3, the surroundings 4 of the vehicle 1, in particular in front of the vehicle 1, are perceived through the windshield 2. Fig. 1 also shows a schematic representation of an embodiment of a head-up display 5. The head-up display 5 is arranged in the vehicle 1. The head-up display 5 has an image generator 6. The image generator 6 generates an image which is perceivable in an eye box by the observer with the eye 3. The head-up display 5 also has an image plane inclination device 7.This image plane inclination device 7 is designed to individually incline an image plane 8 of the image generated by the image generator 6, as intended, in terms of time and / or type, depending on the situation. In the exemplary embodiment, the image plane inclination device 7 has at least one liquid crystal lens 8. In addition, the head-up display 5 has an optical device 10. The optical device 10 is intended to project the image generated by the image generator 6 into the image plane 8. In the exemplary embodiment, this optical device 10 has a first mirror 11. This first mirror 11 is a folding mirror. In addition, the optical device 10 preferably has a separate second mirror 12. This is in particular an aspherical mirror. As can be seen, the folding mirror is arranged in front of the further mirror 12 in the optical path 13 between the image generator 6 and the image plane 8.Furthermore, it can also be seen that in the exemplary embodiment the liquid crystal lens 9 is arranged in this optical path 13 between the image generator 6 and the first mirror 11, in particular the folding mirror.

[0034] In addition, the head-up display 5 preferably has a control unit 14 which is designed to control the liquid crystal lens 9 to change the refractive index of the liquid crystal lens 9 in such a way that light rays of an image of the image generator 6 have different optical path lengths, so that the image plane can be individually tilted.

[0035] In the schematic representation in Fig. 1, this is symbolically represented by light beams 15, 16, and 17. As can be seen, light beam 15 has a shorter optical path than light beams 16 and 17. Light beam 16, in turn, has a shorter optical path than light beam 17. Provision can be made for the liquid crystal lens 9 to be arranged directly on the image generator 6. In Fig. 1, it can also be seen that in the vertical direction and thus in the height direction H, the image generator 6, as the lower light beam 17 in the height direction H, has the longest optical path. In contrast, the light beam emerging from the image generator 6 in the height direction as the upper light beam 15 has the shortest optical path. In particular, this refers to an inclination of the image plane 8 with respect to a reference plane 18.

[0036] In this regard, an angle a is shown in particular, which represents the angle of inclination of the image plane 8 to this reference plane 18. In particular, the reference plane 18 is oriented with respect to an external object to the head-up display 5, in particular to an external object of the vehicle 1. This external object is in particular a road surface 19 on a roadway on which the vehicle 1 is moving. In particular, this reference plane 18 is oriented perpendicular to this road surface 19. It is possible for an angle of inclination a of the image plane 8 to be adjustable, which is between greater than 0° and less than or equal to 80°.It is preferably provided that this angle of inclination a of the image plane 8 to the reference plane 18 can be adjusted dynamically depending on at least one environmental parameter of the environment 4 of the head-up display 5, in particular of the vehicle 1, and / or depending on a vehicle parameter of the vehicle 1, and / or depending on the image to be displayed, which is generated with the image generator 6, and / or depending on a traffic situation in the environment 4 of the vehicle 1.

[0037] In particular, the Head-up Display 5 is an AR head-up display.

[0038] Fig. 2 shows a schematic representation of an embodiment of the liquid crystal lens 9. This is embodied as a matrix lens. It has several lens cells, only some of which are designated by reference numeral 20. The number of lens cells 20, as well as the columns and rows, are merely exemplary and by no means exhaustive.

[0039] Fig. 3 shows a schematic representation of an exemplary structure of a liquid crystal lens 9, in particular a lens cell 20. This multilayer structure can be closed by a closure element 21 and another closure element 22. The closure elements 21 and 22 can be glass plates, for example.

[0040] An electrode 23 can preferably be formed downstream of the termination element 21. A layer 24, which can be an electrical insulation layer, can be provided downstream of this layer, which forms the electrode 23. An electrode 25 is then formed again. Following the electrode 25, a buffer layer 26 can be provided as a further layer. In one embodiment, a polymer layer 27 can be provided downstream of this buffer layer 26. It is possible for an alignment layer to be arranged between the polymer layer 27 and the buffer layer 26.

[0041] A liquid crystal unit 28 can be arranged following the polymer layer 27. In one embodiment, it is possible for a further layer 29 to be formed on the liquid crystal layer or liquid crystal unit 28. This layer can be made of thermoplastic material. A further electrode is provided as a further layer 30. As can be seen in Fig. 3, this liquid crystal lens 9, in particular the lens cell 20, is designed such that two electrical voltages V1 and V2 can occur and be tapped between the aforementioned electrodes 23, 25, 30.

[0042] In particular, it is possible for a refractive index profile to be set or adjustable using the control unit 14 to adjust the inclination of the image plane 8, in which profile the refractive index, viewed in the height direction H of the head-up display 5, is greater in an upper region 9a (Fig. 1) of the liquid crystal lens 9 than in a lower region 9b. Fig. 4 shows an example diagram of a non-linear characteristic curve 31 for a refractive index profile. For this purpose, the refractive index is plotted along the vertical axis, and the height of the liquid crystal lens 9 along the horizontal axis. For this purpose, t denotes the upper region of the liquid crystal lens 9 in the height direction H, and b denotes the lower region of the liquid crystal lens 9b. Thus, in the example in Fig. 4, it can be seen that a non-linear change in the refractive index occurs, and this increases, starting from the upper region t down to the lower region b of the liquid crystal lens 9.

[0043] In this context, a corresponding diagram is shown in Fig. 5, in which three different non-linear characteristic curves 32, 33 and 34 are shown by way of example. These are different. Each of these characteristic curves 32 to 34 is assigned to a specific eye box in the exemplary embodiment. This means that the refractive index can also be changed depending on the eye box. As a result, virtually the same perception of the projected image can be achieved for each eye box, in particular the same inclination of the image plane 8 can be generated. Thus, for example, an individual non-linear characteristic curve can be generated and provided for an upper, a middle and a lower eye box, as viewed in the height direction H, in order to find the same inclination of the image plane 8 for all of these eye boxes.

[0044] With different eye boxes, different angles of incidence or viewing angles to the inclined front panel 2 can occur. This is independent of the liquid crystal lens 9. However, with such a liquid crystal lens 9, these influences can be counteracted and pre-compensation for these image distance shifts can be performed. For example, if an observer changes the optical device 10, in particular a mirror 11 and / or 12, in order to move this eye box up or down, the liquid crystal lens 9 can be changed or adjusted accordingly based on the electronic adjustment in order to compensate for this shift. This is made possible in particular by this diagram in Fig. 5 with the various characteristic curves 32 to 34.

Claims

Patent claims 1. A head-up display (5) for a vehicle (1), comprising an image generator (6) and an optical device (10) with which an image generated by the image generator (6) can be projected into an image plane (8), and comprising an image plane inclination device (7) with which the image plane (8) can be tilted, characterized in that the image plane inclination device (7) has a liquid crystal lens (9) arranged in the optical path (13) between the image generator (6) and an optical element (11, 12) of the optical device (10), and comprising a control unit (14) for controlling the liquid crystal lens (9) to change the refractive index of the liquid crystals of the liquid crystal lens (9) such that light rays (15, 16, 17) of an image of the image generator (6) have different optical path lengths, so that the image plane (8) can be individually tilted.

2. Head-up display (5) according to claim 1, characterized in that the liquid crystal lens (9) is a matrix lens having a plurality of lens cells (20) arranged in a matrix-like manner.

3. Head-up display (5) according to claim 2, characterized in that the lens cells (20) for changing the refractive index can be individually controlled by the control unit (14).

4. Head-up display (5) according to one of the preceding claims, characterized in that the liquid crystal lens (9) has a multi-layer structure at which two electrical voltages (V1, V2) can be generated, so that the refractive index can be changed by adjusting the electrical voltages (V1, V2) and / or the voltage ratio between the two voltages (V1, V2).

5. Head-up display (5) according to one of the preceding claims, characterized in that the liquid crystal lens (9) is arranged separately from the image generator (6) and is arranged in the optical path (13) between the image generator (6) and a folding mirror (11) of the optical device (13), which forms an optical element.

6. Head-up display (5) according to one of the preceding claims 1 to 5, characterized in that the image generator (6) and the liquid crystal lens (9) are arranged in a digital image projector.

7. Head-up display (5) according to one of the preceding claims, characterized in that the image plane (8) is inclinable with respect to a reference plane (18).

8. Head-up display (5) according to claim 7, characterized in that the reference plane (18) is oriented in relation to an object arranged externally to the head-up display (5), in particular the reference plane (18) is a plane oriented in relation to a road surface (19), in particular is oriented perpendicular thereto, on which a vehicle (1) having the head-up display (5) is located.

9. Head-up display (5) according to claim 7 or 8, characterized in that an angle of inclination (a) of the image plane (8) to the reference plane (18) is adjustable between greater than 0° and less than or equal to 80°.

10. Head-up display (5) according to one of the preceding claims 7 to 9, characterized in that an angle of inclination (a) of the image plane (8) to the reference plane (18) is dynamically dependent on at least one environmental parameter of the environment (4) of the head-up display (5) and / or dependent on a vehicle parameter of the vehicle (1) which has the head-up display (5), and / or dependent on the image to be displayed and / or depending on a traffic situation in the surroundings (4) of the vehicle (1).

11. Head-up display (5) according to one of the preceding claims, characterized in that for adjusting the inclination of the image plane (8) a refractive index profile can be set with the control unit (14), in which, viewed in the height direction (H) of the head-up display (5), the refractive index is smaller at an upper region (9a) of the liquid crystal lens (9) than in a lower region (9b).

12. Head-up display (5) according to claim 1 1, characterized in that the refractive index profile has at least one non-linear characteristic curve (31, 32, 33, 34), in particular the refractive index profile has different characteristics (32, 33, 34) for different eye boxes.

13. Head-up display (5) according to one of the preceding claims, characterized in that the control unit (14) is designed to control the liquid crystal lens (9) to generate a refractive index profile such that optical imaging errors, in particular astigmatism, of the optical device (13) can be reduced, in particular compensated.

14. Head-up display (5) according to one of the preceding claims, characterized in that the head-up display (5) is an AR head-up display.

15. Vehicle (1) with a head-up display (5) according to one of the preceding claims.

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