Display device with diffuser

Abstract

The invention relates to a display device (1) comprising an illumination unit (2), a diffuser (3) and a display panel (4). The diffuser (3) has a microlens array (30) with a plurality of microlenses (31). The geometry of the microlenses (31) varies over the area of the microlens array (30) in such a way that the microlens array (30) has a diffuser function and a higher-level lens function.

Description

[0001] Description

[0002] Display device with diffuser

[0003] The present invention relates to a display device comprising a lighting unit, a diffuser and a display panel.

[0004] Microlens arrays are used as optical elements in a wide variety of applications. The microlenses are usually arranged in a regular grid and follow the same lens geometry at every position within the grid. When an ordered beam of light passes through such a microlens array, the geometry of the microlens surface can be used to create a tailored light distribution similar to that of a diffuser film.

[0005] For example, DE 196 30 736 B4 describes a projection screen for a rear projection television set, comprising a Fresnel lens with circular divisions for focusing incident image light into the center of the optical axis of the projection screen, and an optical diffuser part with a lenticular section for diffusing the image light received by the Fresnel lens.

[0006] US 2018 / 0 149 860 A1 describes an optical scanning control device. The optical scanning control device comprises 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 is arranged in an array on a surface of at least one light entrance side and one light exit side of the screen. The microlenses are arranged such that the center-to-center distances are random in at least one of a first direction and a second direction orthogonal to the first direction. In head-up displays, in addition to the diffuser property, a global lens function is often also required. This is usually implemented using a lens on an additional surface. The lens can be designed as a thick lens or a Fresnel lens.However, a challenge with this approach is that not every system has enough space available, and additional components must then be introduced, resulting in additional costs and efficiency losses.

[0007] Another approach is to combine a microlens array with a thick lens, by arranging the microlens array structure on a thick lens and following the surface curvature of the lens. However, a thick lens is complex to manufacture, resulting in increased costs.

[0008] US 2012 / 0 262 646 A1 describes a film that exhibits both polarization selectivity and diffusion properties. The film can comprise a plurality of microlenses. The film can be used in a display device.

[0009] WO 2019 / 238842 A1 describes a device for generating a virtual image using scanning imaging. The device comprises at least one light source for generating a light beam, an imaging unit for generating an image, and an optical waveguide for dilating an exit pupil. An optical component for implementing a field-point-dependent aperture is arranged in front of a coupling region of the optical waveguide. The optical component can have a locally resolved diffuser and lens function.

[0010] JP 2021-135472 A describes a display device comprising a light source, a scanner that deflects the light emitted by the light source, and an optical element with a plurality of micro-optical elements arranged in an array. The optical element scatters the incident light using the micro-optical elements. The propagation direction of the scattered light varies according to the angle of incidence of the light from the scanner onto the optical element.

[0011] It is an object of the invention to provide an alternative solution for a display device with a diffuser, in which the diffuser also has a lens function in addition to the diffuser property.

[0012] This object is achieved by a display device having the features of claim 1. Preferred embodiments of the invention are the subject of the dependent claims.

[0013] According to one aspect of the invention, a display device comprises a lighting unit, a diffuser, and a display panel. The diffuser comprises a microlens array with a plurality of microlenses. The microlenses are sections of a lens, and the geometry of the microlenses varies across the surface of the microlens array such that the microlens array has a diffuser function and a higher-order lens function by varying the respective position of the section relative to a center of the lens across the surface of the microlens array.

[0014] The inventive solution uses a diffuser that combines a diffuser function and a global lens function in a preferably flat surface. The basis of this diffuser is a microlens array with a large number of microlenses. By selecting the geometry of the microlenses, the desired broadening of the light distribution is created for incident light. The global lens function is achieved by locally varying the geometry of the microlenses, i.e., by depending on the position of the respective microlens in the microlens array. Since two functions are combined in one component, the display device is optimized in terms of complexity and cost. By appropriately selecting the geometry of the individual microlenses, almost any global lens can be created.The idea is that, for any given geometry of the surface of the global lenses, the local, two-dimensional slope at the center of the aperture defined by the corresponding microlens is determined, and the geometry of the respective microlens is selected according to the determined slope. In this way, the global lens is, so to speak, imposed on the light distribution of the microlens array.

[0015] According to the invention, the microlenses are sections of a lens and the global lens function is achieved by varying the respective position of the section with respect to a center of the lens over the area of ​​the microlens array.

[0016] For example, the lens can be in the shape of a spherical lens. The microlenses can form sections of a lens. The respective position of the section in relation to a center of the lens varies across the area of ​​the microlens array. In the center of the microlens array, for example, the section of a microlens can be symmetrical around the center of the lens, e.g. the vertex, whereas at the edge of the microlens array the respective section of the microlenses is shifted relative to the center of the lens. As a result, light passing through these microlenses will, in addition to being widened in accordance with the diffuser function, also experience a deflection corresponding to a global lens. By adjusting the shifting of the sections of the individual microlenses accordingly, almost any global lens can be created.

[0017] According to one aspect of the invention, the microlenses are arranged in a regular grid. Arranging the microlenses in a regular grid has the advantage that the resulting light distribution can be controlled very precisely.

[0018] According to one aspect of the invention, the microlenses have a rectangular aperture. This means that the microlenses each have a rectangular base area when viewed from above. This results in the distribution of the output light beams having an approximately rectangular cross-section. Such a cross-section is often desirable, for example, for illuminating the eyebox in a head-up display. In principle, however, the base areas of the microlenses can also have other shapes, for example, round, hexagonal, etc.

[0019] According to one aspect of the invention, the microlens array functions as 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. In principle, however, other global lens functions can also be implemented, e.g., spherical or aspherical converging lenses or diverging lenses.

[0020] According to one aspect of the invention, the display device is a component of a head-up display. The use of a display device according to the invention for head-up displays is particularly advantageous, since these often require a global lens function in addition to the diffuser property.

[0021] According to one aspect of the invention, the illumination unit provides collimated light. The inventive solution is particularly suitable for collimated light, since in this case, a very precisely defined angular distribution of the input light is present. Thus, the angular distribution of the output light is also determined very precisely.

[0022] According to one aspect of the invention, the lighting unit comprises a light source array and a collimator array. The light source array is formed by an arrangement of a plurality of light sources, the light of which is collimated by a plurality of collimators that form the collimator array. In this way, a large-area lighting unit can be realized that ensures homogeneous illumination of the display panel. In principle, however, the described solution can be implemented in display devices with lighting optics of all types. A display device according to the invention is preferably used in a means of transport. The means of transport can be, for example, a motor vehicle, but alternatively also an aircraft, a rail vehicle, or a watercraft.

[0023] Further features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the figures.

[0024] Figure overview

[0025] Fig. 1 shows schematically a head-up display according to the prior art for a motor vehicle;

[0026] Fig. 2 shows schematically a display device of a head-up display;

[0027] Fig. 3 shows schematically a display device according to the invention of a

[0028] Head-up displays;

[0029] Fig. 4 illustrates the operating principle of a diffuser with a rough surface;

[0030] Fig. 5 illustrates the operating principle of a microlens array as a diffuser;

[0031] Fig. 6 shows schematically a first region of a diffuser of a display device according to the invention;

[0032] Fig. 7 schematically shows a second region of a diffuser of a display device according to the invention; Fig. 8 illustrates the implementation of microlenses of a microlens array as sections of a lens; and

[0033] Fig. 9 shows schematically a means of transport that uses a display device according to the invention.

[0034] Character description

[0035] To better understand the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the figures. Like reference numerals are used in the figures for like or equivalent elements and are not necessarily described again for each figure. It is understood that the invention is not limited to the illustrated embodiments and that the described features can also be combined or modified without departing from the scope of the invention as defined in the appended claims.

[0036] Fig. 1 shows a schematic diagram of a head-up display for a motor vehicle according to the prior art. The head-up display comprises a display device 1, an optical unit 6, and a mirror unit 7. A beam SB1 emanates 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 it toward the mirror unit 7. The mirror unit 7 is depicted here as the windshield 70 of a motor vehicle. From there, the beam SB2 travels toward an eye 8 of a viewer.

[0037] The viewer sees a virtual image VB, which is located outside the motor vehicle above the hood or even in front of the vehicle. Due to the interaction of the optical unit 6 and the mirror unit 7, the virtual image VB is an enlarged representation of the image shown on the display panel 4. This symbolically shows a speed limit, the current vehicle speed and navigation instructions. As long as the eye 8 is within the eyebox 9 indicated by a rectangle, all elements of the virtual image VB are visible to the eye 8. If the eye 8 is outside the eyebox 9, the virtual image VB is only partially visible to the viewer or not visible at all. The larger the eyebox 9, the less restricted the viewer is in choosing their seating position.

[0038] The curvature of the curved mirror 61 is adapted to the curvature of the windshield 70 and ensures that the image distortion is stable across the entire eyebox 9. The curved mirror 61 is rotatably mounted by means of a bearing 610. The resulting rotation of the curved mirror 61 enables the eyebox 9 to be moved and thus the position of the eyebox 9 to be adjusted to the position of the eye 8. The first mirror 60 serves to ensure that the path traveled by the beam SB1 between the display panel 4 and the curved mirror 60 is long, while at the same time the optical unit 6 remains compact. The optical unit 6 is separated from the environment by a transparent cover 10. The optical elements of the optical unit 6 are thus protected, for example, from dust present in the interior of the vehicle.A glare shield 11 serves to reliably absorb the light reflected across the interface of the cover 10, preventing glare to the viewer. In addition to sunlight SL, light from another interfering light source 12 can also reach the display panel 4.

[0039] Fig. 2 shows a schematic diagram of a display device 1 of a head-up display. The display device 1 comprises an illumination unit 2 with a light source array 20, i.e. an arrangement of a plurality of light sources 21 whose light is collimated by a plurality of collimators 22 which form a collimator array 23. On its way to the display panel 4, the collimated light beam KLB emanating from the collimator array 23 passes through a lens 13 and a diffuser 3. The lens can be a cylindrical Fresnel lens, for example. The diffuser 3 can be designed as a diffuser film, for example. After passing through the display panel 4, the light beam enters the optical unit (not shown in Fig. 2) as a beam bundle SB1.

[0040] Fig. 3 schematically shows an example of a display device 1 according to the invention for a head-up display. In this case, the display device 1 also comprises an illumination unit 2 with a light source array 20 and a collimator array 23. Of course, other types of light sources can also be used instead of a light source array 20. It is also sufficient if the resulting collimated light beam KLB is only approximately collimated. On its way to the display panel 4, the collimated light beam KLB again passes through a diffuser 3. The diffuser 3 is formed by a microlens array 30 with a plurality of microlenses 31. The geometry of the microlenses 31 varies over the area of ​​the microlens array 30 such that the microlens array 30 also has a higher-level lens function in addition to the diffuser function. An additional lens, as required in the display device 1 shown in Fig. 2, can therefore be omitted.After passing through the display panel 4, the light beam enters the optical unit (not shown here) as beam SB1 as usual.

[0041] Fig. 4 illustrates the functional principle of a diffuser 3 with a rough surface 32. Fig. 4a) shows the basic path of the light rays, Fig. 4b) the angular distribution of the light rays before scattering and Fig. 4c) the angular distribution of the light rays after scattering. The incident light PL is approximately parallel. Its angular distribution is therefore very narrow. Due to the refraction of the light rays at the rough surface 32 as they pass from the diffuser 3 with the refractive index nn to the surrounding medium, typically air, with a refractive index n2, with n2<n1, the angular distribution is significantly broadened. Due to the irregular geometry of the rough surface 32 and the associated random scattering, the angular distribution of the scattered light GL can, for example, have the shape of a Gaussian curve.

[0042] Fig. 5 illustrates the functional principle of a microlens array 30 as a diffuser 3. Fig. 5a) shows the basic path of the light rays, Fig. 5b) the angular distribution of the light rays before scattering, and Fig. 5c) the angular distribution of the light rays after scattering. The incident light PL is again approximately parallel. Its angular distribution is therefore very narrow. Due to the refraction of the light rays by the microlenses 31 of the microlens array 30 as they pass from the diffuser 3 with the refractive index nn to the surrounding medium, typically air, with a refractive index n2, with n2<n1, the angular distribution is also significantly broadened in this case. Due to the regular geometry of the microlenses 31, the scattering does not occur randomly, so that the angular distribution of the scattered light GL can, for example, have a flat-top profile.

[0043] Fig. 6 schematically shows a first region of a diffuser 3 of a display device according to the invention. The microlenses 31 of the microlens array 30 can be seen in the center of the diffuser 3. Fig. 7 schematically shows a second region of the diffuser 3, located near the edge. In this example, the microlenses 31 are arranged in a regular grid and each have a rectangular aperture 33, i.e., the microlenses 31 each have the shape of a rectangle in plan view. The global lens function is achieved by varying the geometry of the microlenses 31 across the surface of the microlens array 30. The microlenses 31 form sections of a lens. The respective position of the section relative to a center of the lens varies across the surface of the microlens array 30. In the center of the microlens array 30, for example, in the case of a microlens 31, the section can be located symmetrically around the center of the lens, e.g.the vertex, while at the edge of the microlens array 30, the respective section of the microlenses 31 is shifted relative to the center of the lens. As a result, light passing through these microlenses 31, in addition to being expanded according to the diffuser function, also experiences a deflection corresponding to a global lens. By appropriately adjusting the shift of the sections of the individual microlenses, almost any desired global lens can be created.

[0044] Fig. 8 illustrates the implementation of microlenses 31 of a microlens array as sections 50 of a lens 5. In the example shown, the lens 5 is a spherical lens. For the sake of simplicity, only a two-dimensional view is shown. The lens 5 has a center 51, e.g., the vertex of the lens 5. The section 50 of the lens 5 that forms the microlens 31 is determined by an aperture cuboid 52 that reflects the aperture of the microlens 31. In other words, the geometry of the microlens 31 is determined by the intersection between the lens 5 and the aperture cuboid 52. The position of the aperture cuboid 52 relative to the center 51 of the lens 5 depends on the position of the respective microlens 31 in the microlens array.

[0045] Fig. 9 schematically shows a means of transport 100 that uses a display device 1 according to the invention. In this example, the means of transport 100 is a motor vehicle. The motor vehicle has a display device 1 according to the invention, which in this example is part of a head-up display. Data on the vehicle's surroundings can be acquired using a sensor system 101. The sensor system 101 can in particular comprise sensors for environmental detection, e.g., ultrasonic sensors, laser scanners, radar sensors, lidar sensors, or cameras. The information acquired by the sensor system 101 can be used to generate content to be displayed for the display device 1. Further components of the motor vehicle in this example are a navigation system 102, by means of which position information can be provided, and a data transmission unit 103. By means of the data transmission unit 103, for example,A connection to a backend can be established, for example, to obtain updated software for components of the motor vehicle. A memory 104 is provided for storing data. Data exchange between the various components of the motor vehicle takes place via a network 105.

[0046] List of reference symbols

[0047] 1 display device

[0048] 2 lighting units

[0049] 20 light source array

[0050] 21 Light source

[0051] 22 Collimator

[0052] 23 Collimator array

[0053] 3 Diffuser

[0054] 30 microlens array

[0055] 31 Microlens

[0056] 32 Surface

[0057] 33 aperture

[0058] 4 Display panel

[0059] 5 lens

[0060] 50 Excerpt

[0061] 51 Center

[0062] 52 aperture blocks

[0063] 6 Optical unit

[0064] 60 First Mirror

[0065] 61 Curved Mirror

[0066] 610 Storage

[0067] 7 Mirror unit

[0068] 70 Windshield

[0069] 8 Eye

[0070] 9 Eyebox

[0071] 10 Cover

[0072] 11 Glare protection

[0073] 12 stray light source

[0074] 13 lens

[0075] 100 Means of transport 101 Sensor technology

[0076] 102 Navigation system

[0077] 103 Data transmission unit

[0078] 104 Storage 105 Network

[0079] GL Scattered light

[0080] KLB Collimated light beam

[0081] PL Parallel Light

[0082] SB1 beam SB2 beam

[0083] SL Sunlight

[0084] VB Virtual Image

Claims

Patent claims 1. Display device (1) with 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), and wherein the microlenses (31) are cutouts (50) of a lens (5) and 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 higher-level lens function in that the respective position of the cutout (50) with respect to a center (51) of the lens (5) varies over the area of ​​the microlens array (30).

2. Display device (1) according to claim 1, wherein the lens (5) is a spherical lens.

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

4. Display device (1) according to one of the preceding claims, wherein the microlenses (31) have a rectangular aperture (33).

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

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

7. Display device (1) according to one of the preceding claims, wherein the illumination unit (2) provides collimated light.

8. Display device (1) according to claim 7, wherein the illumination unit (2) comprises a light source array (20) and a collimator array (23).

9. Means of transport (100) with a display device (1) according to one of the preceding claims.

Images