Display device with diffuser

Abstract

The invention relates to a display device (1) having a lighting unit (2), a diffuser (3) and a display panel (4). The diffuser (3) has a microlens array (30) with a plurality of microlenses (31). Here, the geometry of the microlenses (31) varies over the surface of the microlens array (30) such that the microlens array (30) has a diffuser function and a high-level lens function.

Description

Technical Field

[0001] The present invention relates to a display device having a lighting unit, a diffuser and a display panel. Background Art

[0002] Microlens arrays are used as optical elements in many applications. In this case, the microlenses are usually arranged in a regular grid and follow the same lens geometry at each position of the grid. If a structured light beam passes through such a microlens array, a customized light distribution similar to the light distribution of a diffuser film can be generated on the geometry of the microlens surface.

[0003] For example, DE 196 30 736 B4 describes a projection screen for a rear-projection television, which comprises: a Fresnel lens with circular partitions for focusing incident image light to the center of the optical axis of the projection screen; and an optical diffuser component with lens grid segments for diffusing the image light received from the Fresnel lens.

[0004] US2018 / 0 149 860A1 describes an optical scanning control device. The optical scanning control device includes: a scanning unit configured to scan light emitted by a laser; and a screen on which the light scanned by the scanning unit forms an image. A plurality of microlenses are arranged in an array on the surface of at least one of the light incident side and the light exit side of the screen. Here, the microlenses are arranged so that the center distance is random in at least one of a first direction and a second direction orthogonal to the first direction.

[0005] In head-up displays, in addition to the diffuser properties, a global lens function is often required. This is usually achieved by means of lenses on additional surfaces. The lenses can be implemented as thick lenses or even as Fresnel lenses. However, the challenge of this approach is that not every system has a corresponding number of surfaces available, so additional components must be introduced with corresponding additional costs and efficiency losses.

[0006] Another solution is to combine a microlens array with a thick lens by arranging the structure of the microlens array on the thick lens and following the surface curvature of the lens. However, thick lenses are complex to manufacture, which is accompanied by increased costs.

[0007] US 2012 / 0 262 646 A1 describes a film which, in addition to polarization selectivity, also has diffusion properties. The film may include a plurality of microlenses. The film may be used in a display device.

[0008] WO 2019 / 238 842A1 describes an apparatus for generating a virtual image by scanning image generation. The apparatus has at least one light source for generating a light beam, an imaging unit for generating an image, and an optical fiber for expanding an exit pupil. An optical component is arranged in front of the coupling region of the optical fiber to achieve an aperture related to a field point. The optical component can have a locally resolved diffuser function and a lens function.

[0009] JP 2021-135 472A describes a display device having a light source, a scanner for deflecting light emitted by the light source, and an optical element having a plurality of micro-optical elements arranged in an array. The optical element scatters the projected light by means of the micro-optical elements. The propagation direction of the scattered light changes according to the incident angle of the light emitted from the scanner to the optical element. Summary of the invention

[0010] The object of the present invention is to provide an alternative solution for a display device having a diffuser, wherein the diffuser has a lens function in addition to the diffuser properties.

[0011] This object is achieved by a display device having the features of claim 1. Preferred embodiments of the invention are the subject matter of the dependent claims.

[0012] According to one aspect of the present invention, a display device has an illumination unit, a diffuser, and a display panel. The diffuser has a microlens array with a plurality of microlenses. Here, the microlens is a local part of a lens, and the geometry of the microlens varies on the surface of the microlens array, so that by varying the corresponding position of the local part relative to the center of the lens on the surface of the microlens array, the microlens array has a diffuser function and an advanced / overall lens function.

[0013] In the solution according to the invention, a diffuser is used which combines a diffuser function and a global lens function on a preferably flat surface. The basis of the diffuser is a microlens array with a plurality of microlenses. By selecting the geometry of the microlenses, the desired extension of the light distribution is generated for the incident light. The global lens function is achieved by locally varying the geometry of the microlenses, i.e. depending on the position of the respective microlenses in the microlens array. Since both functions are combined in one component, an optimization of the display device in terms of complexity and cost is achieved. By appropriately selecting the geometry of the individual microlenses, almost any global lens can be generated. Here, the idea is that for any geometry of the surface of the global lens, a local two-dimensional gradient / slope at the aperture center point defined by the associated microlenses is correspondingly derived, and the geometry of the respective microlenses is selected according to the derived gradient. In this way, it can be said that the global lens is influenced by the light distribution of the microlens array.

[0014] According to the invention, the microlenses are local parts of the lens, and the global lens function is achieved by varying the corresponding positions of the local parts relative to the center of the lens on the surface of the microlens array.

[0015] The lens can, for example, have the form of a spherical lens. The microlenses can constitute local portions of the lens. Here, the corresponding position of the local portions relative to the center of the lens changes on the surface of the microlens array. At the center of the microlens array, for example at a certain microlens, the local portions can be symmetrical around the center of the lens (for example, the vertex), while at the edge of the microlens array, the corresponding local portions at these microlenses are offset relative to the center of the lens. Therefore, the light passing through these microlenses, in addition to the expansion corresponding to the diffuser function, also undergoes a deflection corresponding to the global lens. By correspondingly adapting the local displacements of the individual microlenses, an almost arbitrary global lens can be generated.

[0016] According to one aspect of the invention, the microlenses are arranged in a regular grid / grid. Arranging the microlenses in a regular grid has the advantage that the generated light distribution can be controlled very accurately.

[0017] According to one aspect of the present invention, the microlenses have a rectangular aperture. This can be understood as: in a top view, each microlens has a rectangular base surface. This makes the distribution of the output light beam have an approximately rectangular cross section. Such a cross section is usually desired, for example, for illuminating the eyebox in a head-up display. However, in principle, the base surface of the microlens can also have other shapes, such as circular, hexagonal, etc.

[0018] According to one aspect of the invention, the microlens array has the function of a cylindrical lens. Such a cylindrical lens can be used, for example, to correct aberrations or to adapt the light provided by the illumination unit to the display panel. However, in principle, other global lens functions can also be realized, such as a spherical or aspherical converging lens or a scattering lens.

[0019] According to one aspect of the invention, the display device is a component of a head-up display. The use of the display device according to the invention for head-up displays is particularly advantageous, since in these head-up displays a global lens function is often required in addition to the diffuser properties.

[0020] According to one aspect of the invention, the lighting unit provides collimated light. The solution according to the invention is particularly suitable for collimated light, since in this case there is a very accurately defined angular distribution of the input light. The angular distribution of the output light is therefore also very accurately determined.

[0021] According to one aspect of the invention, the lighting unit has a light source array and a collimator array. The light source array consists of a component with a plurality of light sources, the light of which is collimated by a plurality of collimators constituting the collimator array. In this way, a large-area lighting unit can be realized, which ensures a uniform illumination of the display panel. However, in principle, the described solution can be implemented in display devices with any type of illumination optics.

[0022] Preferably, the display device according to the invention is used in a vehicle, which may be, for example, a motor vehicle, but alternatively may also be an aircraft, a rail vehicle or a ship.

[0023] Other features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematically illustrates a head-up display for a motor vehicle according to the prior art;

[0025] Figure 2 schematically illustrates a display device of a head-up display;

[0026] Figure 3 The display device of the present invention of a head-up display is schematically shown;

[0027] Figure 4 Demonstrate the working principle of a diffuser with a rough surface;

[0028] Figure 5 Demonstrate the working principle of microlens array as a diffuser;

[0029] Figure 6Schematically showing a first region of a diffuser of a display device of the present invention;

[0030] Figure 7 Schematically showing a second region of a diffuser of a display device of the present invention;

[0031] Figure 8 Demonstrating the implementation of microlenses of a microlens array as local portions of a lens; and

[0032] Fig. 9 A vehicle using the display device according to the present invention is schematically shown. DETAILED DESCRIPTION

[0033] In order to better understand the principles of the present invention, the embodiments of the present invention are described in more detail below with the aid of the accompanying drawings. The same reference numerals are used for the same or the same functioning elements in the accompanying drawings, and it is not necessary to re-describe each of the drawings. It should be understood that the present invention is not limited to the embodiments shown, and the features described may also be combined or modified without departing from the scope of protection of the present invention as defined in the appended claims.

[0034] Figure 1 A schematic diagram of the principle of a head-up display for a motor vehicle according to the prior art is shown. The head-up display has a display device 1, an optical unit 6 and a mirror unit 7. A beam SB1 is emitted from a display panel 4 of the display device 1, which is reflected by a first mirror 60 onto a curved mirror 61, which reflects the beam in the direction of the mirror unit 7. The mirror unit 7 is shown here as a windshield 70 of a motor vehicle. From there, the beam SB2 is emitted to the eye 8 of the observer.

[0035] The observer sees a virtual image VB, which is located outside the motor vehicle above the bonnet or even in front of the motor vehicle. Through the combined action of the optical unit 6 and the mirror unit 7, the virtual image VB is an enlarged display of the image displayed by the display panel 4. The speed limit, the current vehicle speed and the navigation instructions are symbolically shown here. As long as the eye 8 is within the eye movement range 9 indicated by the rectangle, all elements of the virtual image VB can be seen by the eye 8. If the eye 8 is outside the eye movement range 9, the virtual image VB can only be partially seen by the observer or even not seen at all. The larger the eye movement range 9, the less restricted the observer is when choosing his sitting position.

[0036] The curvature of the curved mirror 61 matches the curvature of the windshield 70 and ensures that the image display / image distortion (Bildverzeichnung) over the entire eye-moving range 9 is stable. The curved mirror 61 is rotatably mounted by means of a support 610. The rotation of the curved mirror 61 that can be achieved thereby enables the eye-moving range 9 to be displaced and thus the position of the eye-moving range 9 to be adjusted according to the position of the eye 8. The first mirror 60 is used to make the path that the beam SB1 passes through between the display panel 4 and the curved mirror 60 longer and at the same time the optical unit 6 is still very compact. The optical unit 6 is isolated from the surrounding environment by means of a transparent cover 10. Therefore, the optical elements of the optical unit 6 are protected, for example, from dust in the interior space of the vehicle. The shading member 11 is used to reliably absorb the light reflected on the interface of the cover 10 so as not to cause dazzle to the observer. In addition to the sunlight SL, light from other interfering light sources 12 may also be transmitted to the display panel 4.

[0037] Figure 2 A display device 1 of a head-up display is schematically shown. The display device 1 comprises an illumination unit 2 having a light source array 20, i.e., an assembly having a plurality of light sources 21, the light of which is collimated by a plurality of collimators 22 constituting a collimator array 23. On the way to the display panel 4, the collimated light beam KLB from the collimator array 23 passes through a lens 13 and a diffuser 3. The lens can be, for example, a cylindrical Fresnel lens. The diffuser 3 can be designed, for example, as a diffusion film. After passing through the display panel 4, the light beam is incident as a beam SB1 onto the display panel 4. Figure 2 Optical unit not shown.

[0038] Figure 3 An example of a display device 1 according to the invention for a head-up display is shown schematically. In this case, the display device 1 also comprises a lighting unit 2, which has a light source array 20 and a collimator array 23. Of course, other types of light sources can also be used instead of the light source array 20. It is sufficient even if the collimated light beam KLB generated is only approximately collimated. On the way to the display panel 4, the collimated light beam KLB passes through the diffuser 3 again. The diffuser 3 is composed of a microlens array 30 having a plurality of microlenses 31. Here, the geometry of the microlenses 31 is varied on the surface of the microlens array 30 in such a way that the microlens array 30 has an advanced lens function in addition to the diffuser function. Therefore, the diffuser 3 can be omitted. Figure 2 The additional lenses shown are required for the display device 1. After passing through the display panel 4, the light beam is incident as beam SB1 as usual on an optical unit not shown here.

[0039] Figure 4 The working principle of a diffuser 3 with a rough surface 32 is shown. Figure 4 a) shows the principle course of the light beam, Figure 4 b) shows the angular distribution of the beam before scattering, Figure 4 c) shows the angular distribution of the light beam after scattering. The incident light PL is approximately parallel. Therefore, its angular distribution is very narrow. 1 The diffuser 3 transitions to a refractive index of n 2 The surrounding medium (typically air, where n 2 <n 1 ) when the light beam is refracted on the rough surface 32, so the angular distribution is significantly widened. Due to the irregular geometry of the rough surface 32 and the random scattering associated therewith, the angular distribution of the scattered light GL can have the form of a Gaussian curve, for example.

[0040] Figure 5 The working principle of the microlens array 30 as a diffuser 3 is shown. Figure 5 a) shows the principle course of the light beam, Figure 5 b) shows the angular distribution of the beam before scattering, Figure 5 c) shows the angular distribution of the light beam after scattering. The incident light PL is roughly parallel again. Therefore, its angular distribution is very narrow. 1 The diffuser 3 transitions to a refractive index of n 2 The surrounding medium (typically air, where n 2 <n 1 ) when the light beam is refracted by the microlens 31 of the microlens array 30, so the angular distribution is also significantly widened in this case. However, due to the regular geometric shape of the microlens 31, the scattering is not random, so the angular distribution of the scattered light GL can have, for example, a flat top profile.

[0041] Figure 6 A first region of a diffuser 3 of a display device according to the invention is schematically shown. In the centre of the diffuser 3 a microlens 31 of a microlens array 30 can be seen. Figure 7The second area near the edge of the diffuser 3 is schematically shown. In this example, the microlenses 31 are arranged in a regular grid and each has a rectangular aperture 33, that is, in a top view, the microlenses 31 have a rectangular shape. The global lens function is achieved by changing the geometry of the microlenses 31 on the surface of the microlens array 30. The microlenses 31 constitute local parts of the lens. Here, the corresponding position of the local part relative to the center of the lens changes on the surface of the microlens array 30. At the center of the microlens array 30, for example at one microlens 31, the local part can be symmetrical around the center of the lens (for example, the vertex), while at the edge of the microlens array 30, the corresponding local parts at these microlenses 31 are offset relative to the center of the lens. Therefore, the light passing through these microlenses 31 undergoes a deflection corresponding to the global lens in addition to the expansion corresponding to the diffuser function. By correspondingly adapting the local displacement of each microlens, an almost arbitrary global lens can be produced.

[0042] Figure 8 The microlens 31 of the microlens array is shown as a realization of a local 50 of the lens 5. In the example shown, the lens 5 is a spherical lens. For simplicity, only a two-dimensional view is shown. The lens 5 has a center 51, such as the vertex of the lens 5. The local 50 of the lens 5 constituting the microlens 31 is determined by an aperture block 52 reflecting the aperture of the microlens 31. In other words, the geometry of the microlens 31 is determined by the overlap between the lens 5 and the aperture block 52. The position of the aperture block 52 relative to the center 51 of the lens 5 depends on the position of the corresponding microlens 31 in the microlens array.

[0043] Fig. 9 A vehicle 100 using a display device 1 according to the present invention is schematically shown. In this example, the vehicle 100 is a motor vehicle. The motor vehicle has a display device 1 according to the present invention, which is a component of a head-up display in this example. Data of the vehicle's surroundings can be collected using a sensor device 101. The sensor device 101 can include sensors for environmental perception, such as ultrasonic sensors, laser scanners, radar sensors, lidar sensors or cameras. The information collected by the sensor device 101 can be used to generate content to be displayed on the display device 1. In this example, other components of the motor vehicle include a navigation system 102 that can provide position information and a data transmission unit 103. With the help of the data transmission unit 103, for example, a connection can be established with the back end in order to obtain the latest software for components of the motor vehicle. In order to store data, there is a memory 104. Data exchange between the various components of the motor vehicle is carried out via a network 105.

[0044] Reference numerals list

[0045] 1 Display device

[0046] 2 Lighting units

[0047] 20 Light source array

[0048] 21 Light Source

[0049] 22 Collimator

[0050] 23 Collimator Array

[0051] 3 Diffuser

[0052] 30 Microlens Array

[0053] 31 Microlens

[0054] 32 Surface

[0055] 33 Aperture

[0056] 4 Display Panel

[0057] 5. Lens

[0058] 50 Partial

[0059] 51 Center

[0060] 52 Aperture Block

[0061] 6 Optical unit

[0062] 60 First Mirror

[0063] 61 Curved Mirror

[0064] 610 Support

[0065] 7 Mirror Unit

[0066] 70 Windshield

[0067] 8 Eyes

[0068] 9 Eye movement range

[0069] 10 Cover

[0070] 11 Shading parts

[0071] 12 Interference light source

[0072] 13 Lens

[0073] 100 Transportation

[0074] 101 Sensor Device

[0075] 102 Navigation System

[0076] 103 Data Transmission Unit

[0077] 104 Memory

[0078] 105 Network

[0079] GL Scattered Light

[0080] KLB Collimated Beam

[0081] PL Parallel Light

[0082] SB1 beam

[0083] SB2 beam

[0084] SL Sunlight

[0085] VB Virtual Image

Claims

1. A display device (1), comprising a lighting unit (2), a diffuser (3) and a display panel (4), wherein: The diffuser (3) has a microlens array (30) with a plurality of microlenses (31), wherein the microlens (31) is a part (50) of a lens (5), and the geometric shape of the microlens (31) varies on the surface of the microlens array (30), so that by varying the corresponding position of the part (50) relative to the center (51) of the lens (5) on the surface of the microlens array (30), the microlens array (30) has a diffuser function and an advanced lens function.

2. The display device (1) according to claim 1, wherein: The lens (5) is a spherical lens.

3. The display device (1) according to claim 1 or 2, wherein: The microlenses (31) are arranged in a regular grid.

4. The display device (1) according to one of the preceding claims, wherein: The microlens (31) has a rectangular aperture (33).

5. The display device (1) according to one of the preceding claims, wherein: The microlens array (30) has the function of a cylindrical lens.

6. The display device (1) according to one of the preceding claims, wherein: The display device (1) is a component of a head-up display.

7. The display device (1) according to one of the preceding claims, wherein: The lighting unit (2) provides collimated light.

8. The display device (1) according to claim 7, wherein: The lighting unit (2) comprises a light source array (20) and a collimator array (23).

9. A vehicle (100) having a display device (1) according to one of the preceding claims.

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