Coupling area of ​​a light guide for a display device

Abstract

The present invention relates to an optical fiber (400) for a display device (100) with a display panel (200). The optical fiber (400) has an input area (410) with an input surface (411) for coupling light (301) from a light source (300) and a deflection area (450) with a light deflection surface (451) for deflecting the light (301) into a light-guiding area (440) for guiding the light (301) along an axis (460). The light-guiding area (440) has a top surface (441) that is parallel to the axis (460) and a bottom surface (442) that is inclined relative to the axis (460) and has a structure (443) for deflecting the light (301) incident on the bottom surface (442) towards the top surface (441). The structure (443) is designed to achieve a homogeneous, surface-level illumination of the top surface (441). The coupling area (410) has a stepped structure (420).

Description

[0001] The present invention relates to a light guide for a display device for installation in a motor vehicle. Such light guides for backlighting a display device are used today in almost every motor vehicle, for example for the electro-optical display of speed information, navigation information, or other vehicle information.

[0002] In most cases, display backlights are based on light guides into which light from several light-emitting diodes (LEDs) is coupled. The light propagates through the light guide by total internal reflection and is then coupled out again with the help of microstructures on the light guide, resulting in a homogeneous light distribution.

[0003] In such backlighting applications, it is often necessary to deflect the light by 90° after coupling it into the optical fiber. This deflection is typically achieved using a planar or curved deflection surface. In both cases, the light emitted by the LED is coupled in planarly, meaning the emitted light strikes a planar coupling surface of the optical fiber. With both designs, the deflection area must be obscured to prevent uncontrolled stray light. Using a curved deflection surface generally allows for high deflection efficiency. The efficiency increases with the degree of curvature of the deflection surface.

[0004] A disadvantage of this approach is that, with increasing efficiency when using a curved deflection surface, the width of the aperture for blocking uncontrolled stray light becomes ever larger, which is undesirable in many applications. If deflection needs to be implemented in a small space, the previously described concepts result in efficiency losses of 50% or more. Due to the aperture, display devices are limited in their design and size, and frameless displays cannot be used.

[0005] WO 2013 037 288 A1 describes a direct light guide structure, a direct light guide plate and a light-emitting device.

[0006] US 2010 0 195 315 A1 describes a light-emitting device and an image-displaying device.

[0007] US 2001 0 019 380 A1 describes a lighting unit and a liquid crystal display that uses it.

[0008] The present invention is based on the objective of providing an improved solution for a coupling area of ​​an optical fiber, thereby achieving a more efficient use of the light coupled into the optical fiber.

[0009] This problem is solved according to the invention by a light guide for a display device according to the preamble of independent claim 1 together with the features of the characterizing part of independent claim 1. Advantageous embodiments can be found in the dependent claims.

[0010] The invention provides a light guide for a display device with a display panel, wherein the light guide has an input area for coupling light from a light source, wherein the light guide has a deflection area with a light deflection surface for deflecting the light into a light guide area for guiding the light along an axis, wherein the light guide area has a top surface that is designed parallel to the axis and a bottom surface that is inclined relative to the axis and has a structure for deflecting the light incident on the bottom surface towards the top surface, wherein the structure is designed to achieve a homogeneous planar backlighting of the top surface, wherein the input area has a stepped structure.

[0011] In the solution according to the invention, the light guide is designed to redirect the light emitted by the light source, e.g., an LED, after it is coupled into the coupling area of ​​the light guide. The light emitted by the light source is initially distributed uncontrollably in all directions after being coupled into the coupling area of ​​the light guide. A portion of the coupled light strikes a surface of the stepped structure according to the invention and is selectively modified and redirected in its emission angle, thereby preventing the formation of unwanted, uncontrolled scattered light. The stepped structure formed in the coupling area thus ensures that a portion of the coupled light is redirected in a defined quantity and at a defined angle onto the light-deflector surface of the light guide.When the light from the stepped structure strikes the light deflection surface, total internal reflection does not occur due to the angle altered by the stepped structure. Instead, the light exits the light guide at the deflection surface almost completely at a defined angle. This light can then be used to backlight a portion of the display panel located in this area. The unusable edge of the display can thus be reduced to just a few millimeters, enabling virtually borderless displays without the need for a diffuser to block stray light.

[0012] A particular advantage of the light guide according to the invention is that the light coupled into the coupling area by the light source is deflected in a defined amount, thereby preventing unwanted, uncontrolled scattered light in the deflection area and allowing the light deflected by the step structure to be used for homogeneous backlighting of a display panel without a diaphragm.

[0013] The stepped structure has at least one leg and at least one flank. One advantage is that a stepped structure with one leg and one flank is particularly easy to manufacture, as it does not require a complex surface structure. Furthermore, it has been found that the coupling area can be easily adapted to the design of the display device, especially the size of the display panel, due to the stepped structure; that is, the height and width of the light guide can be varied. Thus, even with limited installation space, the distance between, for example, a coupling surface and the deflection area can be easily varied thanks to the stepped structure in the coupling area, without generating unwanted stray light and therefore without requiring a baffle. Height variation of the coupling area is particularly advantageous in instrument clusters with integrated display panels.

[0014] The light guide incorporates a reflector. One advantage of this is that the light coupled out at the edge cannot be coupled back into the light guide, particularly not into the light-guiding area, by means of the reflector, thus preventing over-illumination of the display panel. The light coupled out at the edge is directed away from the light guide and therefore away from the display panel by the reflector.

[0015] According to an advantageous embodiment of the invention, the leg has an angle of less than 42.5° relative to the perpendicular of the coupling surface. It has been found that a leg in this angular range provides particularly good reduction of stray light and homogeneous backlighting in the deflection area and the adjacent light guide area. A further advantage is that the light reflected by such a leg is distributed evenly across the display panel in the deflection area, thereby avoiding areas of varying brightness and easily achieving the desired homogeneous backlighting of the deflection area and the adjacent light guide area, and thus homogeneous backlighting of the entire display panel.

[0016] According to an advantageous embodiment of the invention, the flank has an angle greater than 43° relative to the perpendicular of the coupling surface, preferably an angle within a range of 43° to 90°. It has been found that a flank within this angular range prevents over-illumination in the light deflection area. Excess light coupled into the coupling area from the light source is coupled out via the flank. This has the advantage that the excess light does not enter the light-guiding area uncontrollably and cause undesirable areas of varying brightness there.

[0017] According to an advantageous embodiment of the invention, the stepped structure has at least four steps, each step comprising a leg and a flank. It has been found that such a stepped structure ensures a particularly homogeneous light distribution in the deflection area and in the adjacent light guide area. With such a stepped structure, the desired area-wide backlighting and thus homogeneous backlighting of the display panel can be easily achieved. A further advantage is that light losses are significantly reduced due to such a stepped structure, thereby enabling compact and efficient light deflection in a small space.

[0018] According to an advantageous embodiment of the invention, a first stage has a first leg at an angle to the perpendicular of the coupling surface between 24.1° and 25.1°, preferably 24.6°.

[0019] Advantageously, a second stage following the first stage has a second leg at an angle to the perpendicular of the coupling surface between 19.3° and 20.3°, preferably 19.8°.

[0020] Advantageously, a third stage following the second stage has a third leg at an angle to the perpendicular of the coupling surface between 16.3° and 17.3°, preferably 16.8°.

[0021] Advantageously, a fourth stage following the third stage has a fourth leg at an angle to the perpendicular of the coupling surface between 11.3° and 12.3°, preferably 11.8°. It has been found that a coupling area with such stages enables particularly efficient illumination of display panels, even in the deflection area, with a wide beam angle, thereby utilizing as much light from the light source as possible.

[0022] According to an advantageous embodiment of the invention, single white LEDs are provided as the light source. Duo-LEDs can also be used, consisting of two LEDs sharing a standard LED package. This configuration is advantageous when the light guide is to be used for simple backlighting of a display panel in a small space, which is backlit by only a single light source. An advantage is that a single LED and the stepped structure according to the invention in the coupling area of ​​the light guide generate a desired homogeneous light color for backlighting the display panel. Furthermore, this allows for use in very small spaces where the coupling area must be very small and only one light source is required. Compared to other solutions, the space requirement and assembly effort of a single LED are very low.

[0023] According to a further advantageous embodiment of the invention, at least two single-color LEDs are provided as the light source. Such an embodiment is useful when the light guide is to be used for backlighting a display panel that cannot be backlit with a single light source. Such a light source is particularly suitable for very large display panels that use multiple single-color LEDs for backlighting. An advantage is that the use of different colored single-color LEDs and the stepped structure according to the invention in the coupling area of ​​the light guide generates a desired homogeneous light color. In particular, white light can also be achieved if light sources with a suitable primary color are used. Furthermore, backlighting in other colors and color temperatures between warm and daylight white light can also be easily implemented.

[0024] It has been found that, for example, the combination of red (R-LED), green (G-LED), and blue (B-LED) LEDs, also known as R / G / B-LEDs, is particularly well-suited. Using R / G / B-LEDs allows for excellent coverage of white light, as well as any color desired by the customer, and color correction. A further advantage is that replacing a colored LED with one of a different color eliminates the need to measure new LEDs, making the use of R / G / B-LEDs both time- and cost-efficient.

[0025] The optical fiber according to the invention is used in display devices, particularly in the automotive sector, e.g., for a central display in the dashboard or an instrument cluster. The optical fiber according to the invention can also be used for backlighting control elements, e.g., button systems.

[0026] The invention provides a light guide for a display device with a display panel, wherein the light guide has an input area for coupling light from a light source, wherein the light guide has a deflection area with a light deflection surface for deflecting the light into a light guide area for guiding the light along an axis, wherein the light guide area has a top surface that is designed parallel to the axis and a bottom surface that is inclined relative to the axis and has a structure for deflecting the light incident on the bottom surface towards the top surface, wherein the structure is designed to achieve a homogeneous planar backlighting of the top surface, wherein the input area has a stepped structure.

[0027] In the solution according to the invention, the light guide is designed to redirect the light emitted by the light source, e.g., an LED, after it is coupled into the coupling area of ​​the light guide. The light emitted by the light source is initially distributed uncontrollably in all directions after being coupled into the coupling area of ​​the light guide. A portion of the coupled light strikes a surface of the stepped structure according to the invention and is selectively modified and redirected in its emission angle, thereby preventing the formation of unwanted, uncontrolled scattered light. The stepped structure formed in the coupling area thus ensures that a portion of the coupled light is redirected in a defined quantity and at a defined angle onto the light-deflector surface of the light guide.When the light from the stepped structure strikes the light deflection surface, total internal reflection does not occur due to the angle altered by the stepped structure. Instead, the light exits the light guide at the deflection surface almost completely at a defined angle. This light can then be used to backlight a portion of the display panel located in this area. The unusable edge of the display can thus be reduced to just a few millimeters, enabling virtually borderless displays without the need for a diffuser to block stray light.

[0028] A particular advantage of the light guide according to the invention is that the light coupled into the coupling area by the light source is deflected in a defined amount, thereby preventing unwanted, uncontrolled scattered light in the deflection area and allowing the light deflected by the step structure to be used for homogeneous backlighting of a display panel without a diaphragm.

[0029] The stepped structure has at least four steps, each with a leg and a flank. It has been found that such a stepped structure ensures a particularly homogeneous light distribution in the deflection area and the adjacent light guide area. This stepped structure allows for the simple implementation of the desired area-wide backlighting and thus homogeneous backlighting of the display panel. A further advantage is that this stepped structure significantly reduces light loss, enabling compact and efficient light deflection in a small space.

[0030] A first stage has a first leg at an angle to the perpendicular of the coupling surface between 24.1° and 25.1°, preferably 24.6°.

[0031] A second stage, following the first stage, has a second leg at an angle to the perpendicular of the coupling surface between 19.3° and 20.3°, preferably 19.8°.

[0032] A third stage, following the second stage, has a third leg at an angle to the perpendicular of the coupling surface between 16.3° and 17.3°, preferably 16.8°.

[0033] A fourth stage, following the third stage, has a fourth leg at an angle to the perpendicular of the coupling surface between 11.3° and 12.3°, preferably 11.8°. It has been found that a coupling area with such stages enables particularly efficient illumination of display panels, even in the deflection area, with a wide beam angle, utilizing as much light from the light source as possible.

[0034] Further features of the present invention will become apparent from the following description and the attached claims in conjunction with the figures. Advantageous embodiments of the invention will also become apparent from the features of the following description and the figures.

[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. The same reference numerals are used in the figures for identical or equivalently acting elements and are not necessarily described again for each figure. It is understood that the invention is not limited to the embodiments shown and that the described features can also be combined or modified without departing from the scope of protection of the invention as defined in the appended claims. Figure overview

[0036] They show, in a schematic, sketch-like representation: Fig. 1 known concepts for light deflection in an optical fiber, Fig. 2 a section through a light guide together with the amount of light emitted over the length of the light guide. Fig. 3 a section through an embodiment of an optical fiber according to the invention; Fig. 4 an enlarged sectional view of an embodiment of a coupling area of ​​an optical fiber according to the invention; Fig. 5 an enlarged oblique view of part of an embodiment of a coupling area of ​​an optical fiber according to the invention; Fig. 6 a section through a display device with a light guide according to the invention; Fig. 7 a section through a light guide according to the invention together with the amount of light emitted over the length of the light guide. Character description

[0037] Fig. Figure 1 shows known concepts for light deflection in an optical fiber 400. In backlighting applications, it is often necessary to deflect the light 301 by 90° after coupling it into the optical fiber 400. In one concept, a planar deflection surface 451 is used for this deflection. This concept is described in Fig. 1a) is shown and achieves a deflection efficiency of approximately 50%. In another concept, a curved surface 451 is used for deflection. Examples of this are shown in Fig. 1b) and Fig. 1c) shown. In Fig. 1b) The curved surface 451, or the section through the curved surface 451, is a circular arc. In Fig. 1c), on the other hand, involves a parabolic deflection. In all cases, planar coupling of the light 301 emitted by a light source not shown in the figure, for example a light-emitting diode, occurs; that is, the emitted light 301 strikes a planar coupling surface 411 of the optical fiber 400. In the cases described below, the following applies: Fig. 1a) and Fig. 1b) In the concepts shown, the area of ​​the deflecting surface 451 must be covered by an aperture not shown in the figures due to scattered light.

[0038] When using a curved deflection surface 451, a high deflection efficiency can generally be achieved. The efficiency increases the smaller the curvature of the deflection surface. For example, while in the Fig. 1b) shows an efficiency of only 40%, the efficiency of the arrangement shown in Fig. 1c) shown arrangement at 90%. However, this means that with increasing efficiency, the aperture width becomes ever larger, which is undesirable in many applications.

[0039] Fig. Figure 2 shows a section through an optical fiber 400 together with the distribution of the amount of light y emitted over the length of the optical fiber 401. The optical fiber 400 shown here has a greater curvature than the one shown in Figure 2. Fig. 1c) described light guide 400. In this area, light 306 couples out of the light guide 400 in an uncontrolled manner. The light 301 coupled into the light guide 400 is deflected by 90° via a deflection area 450 into a light guide area 440 of the light guide 400. In this way, homogeneous backlighting of the display panel 200, which is arranged above the light guide area 440, is achieved. For the deflection of the light 305 into the light guide area 440, the deflection area 450 has a parabolic deflection surface 451, which is shown in the section shown. Fig. 2 is shown. A diagram illustrates the distribution of the light 305, 306 coupled out of the optical fiber 400, based on the amount of light indicated on the y-axis (also referred to as luminance or luminance, usually measured in cd / m²). 2 ) shown over the length 401 of the optical fiber 400 specified on the x-axis.

[0040] The optical fiber 400 has a coupling area 410 with a coupling surface 411 for coupling light 301 from a light source 300. The light 301 emitted by the light source 300, for example a light-emitting diode, strikes a planar coupling surface 411 and is coupled into the coupling area 410 of the optical fiber 400. The light 301 coupled into the coupling area 410 of the optical fiber 400 is then distributed uncontrollably in all directions along the optical fiber 400. The coupled light 301 strikes the light deflection surface 451 of the deflection area 450 in an uncontrolled manner, causing part of the light 305 to be deflected into the light guide area 440 by total internal reflection, and another part of the coupled light 301 is coupled out of the light guide 400 as coupled-out light 306 in the area of ​​the light deflection surface 451.Due to partial coupling of the light from the light guide 400, uncontrolled stray light 306 occurs in the deflection area 450, resulting in overillumination in this area. The uncontrolled stray light 306 is masked by an aperture 470 located above the deflection area 450.

[0041] Based on the in Fig. As shown in diagram 2, the amount of light, indicated on the y-axis, increases along the length 401 of the light guide 400 (indicated on the x-axis) due to stray light 306 in the deflection area 450, leading to over-illumination in this area of ​​the light guide 400. In contrast, the light 305 deflected into the light guide area 440 is distributed almost uniformly along its length. The amount of light, indicated on the y-axis, thus remains constant in the light guide area 440 along the length of the light guide 400 (indicated on the x-axis), resulting in homogeneous backlighting of the display panel 200.

[0042] As in Fig. As shown in Figure 2, the amount of light y is not distributed uniformly over the length 401 of the light guide 400, which means that in the deflection area 450 of the light guide 400 a aperture 470 is required due to stray light 306 and the size of the display panel 200 to be backlit is severely limited.

[0043] Fig. Figure 3 shows a section through an exemplary embodiment of an optical fiber 400 according to the invention. The optical fiber 400 has a coupling area 410 for coupling light 301 from a light source 300, e.g., a light-emitting diode. The coupling area 410 has a stepped structure 420 on its outer surface, extending towards the optical fiber area 440. The stepped structure is formed between a coupling surface 411 of the coupling area 410 and an underside 442 of the optical fiber area 440. In an exemplary embodiment, the stepped structure 420 has several, in this embodiment four, successive steps. Each of the four steps 421-424 in turn has a leg 430-433 and a flank 434-437. A detailed illustration of the stepped structure 420 is given in Figure 3. Fig. 4 and Fig. 5.

[0044] The light source 300, in its assembled state, is positioned with the light guide 400 below the coupling surface 411 of the coupling area 410. The coupling of the light 301 emitted by the light source 300, i.e., the emitted light 301, strikes the planar coupling surface 411 and is coupled into the coupling area 410 of the light guide 400.

[0045] The light 301, after being coupled into the coupling area 410 of the optical fiber 400, is distributed uncontrollably in all directions. A portion of the coupled light 301 encounters the step structure 420 according to the invention and its exit angle is selectively changed via surfaces of the legs 430-433 and deflected towards the parabolic deflecting surface 451 formed in the deflection area 450, thereby preventing the formation of uncontrolled scattered light 306 in the deflection area 450. The surfaces of the legs 430-433 are, as shown in Fig. As shown in Figure 4, the coupling surface 411 is formed at an angle α of less than 42.5° relative to the perpendicular. This results in a homogeneous light distribution in the deflection area 450. The legs 430-433 of the stepped structure 420 according to the invention ensure that a portion of the coupled light 301 is deflected in a defined quantity at a defined angle onto the light deflection surface 451 of the optical fiber 400. When the light 301 coming from the legs 430-433 of the stepped structure 420 strikes the light deflection surface 451, total internal reflection does not occur. Instead, the light 301 striking the light exits the optical fiber 400 almost completely in the region of the deflection surface 451 of the deflection area 450 at a defined angle. The light 304 coupled out of the optical fiber is used to illuminate a portion of the light arranged in this region. Fig. to backlight the three display panels 200 (not shown). An advantage of the light 304 coupled out from the light deflection surface 451 is that the propagation behavior of the coupled light 304, which is deflected from the legs 430-433 of the stepped structure 420 according to the invention onto the deflection surface 451, is predictable. The light 304 coupled out from the light guide 400 enables a planar, homogeneous light distribution in the deflection area 450 and ensures planar, homogeneous backlighting of the display panel 200 in this area.

[0046] Another portion of the light 301 coupled into the coupling area 410, namely the unwanted light 302, 303 in the edge region of the coupling area 410, couples out of the light guide 400. The light 303 coupled out in the edge region of the coupling area 410, opposite the stepped structure 420, strikes a reflector 801 and is directed away from the light guide 400 and thus away from the display panel 200, preventing it from re-coupled into the light guide, and in particular not into the light guide area. This prevents over-illumination of the display panel 200 in this region of the coupling area 410 due to unwanted light 303. The same principle applies to the light 302 coupled out in the edge region of the coupling area 410, in the direction of the light guide area 440. The unwanted light 302 strikes the flanks 434-437 of the step structure 420 according to the invention. The flanks are, as in Fig. As shown in Figure 4, the coupling surface 411 is arranged at an angle β greater than 43° to the perpendicular. The light 302 striking the flanks 434-437 is thus coupled out of the coupling area 410 and therefore out of the light guide 400. The unwanted light 302 coupled out of the light guide 400 strikes the reflector 800 and is directed away from the light guide 400 and thus away from the display panel 200 by means of the reflector, so that no over-illumination of the display panel 200 occurs in this area and the coupled-out light 302 is not coupled back into the light guide, in particular not into the light guide area. Reflector 800 is located below the light guide area 440 and extends over its entire length. A reflector 801, which reflects the coupled-out light 303, is also located in the deflection area 450. Reflectors 800 and 801 could optionally be formed as a single unit.

[0047] The deflection area 450 with the light deflection surface 451 also serves to partially deflect the light 301 coupled into the coupling area 410 into the light guide area 440 of the optical fiber 400. The light deflection surface 451 is arranged parabolically relative to the coupled light 301 and the axis 460 of the optical fiber area 440. Due to the parabolic shape of the light deflection surface 451, a homogeneous light distribution of the light 305 deflected into the light guide area 440 of the optical fiber 400 is achieved.

[0048] The light guide area 440 serves to guide the light 305, deflected by the deflecting surface 451, along an axis 460. The light guide area 440 has a top surface 441, which is designed parallel to the axis 460, and a bottom surface 442, which is inclined relative to the axis 460. The bottom surface 442 of the light guide area 440 has a structure 443 for deflecting the light 305 incident on the bottom surface 442 towards the top surface 441 of the light guide 400. The structure 443 is designed to provide a planar, homogeneous backlighting of the top surface 441, and thus homogeneous backlighting of a Fig. to realize 3 display panels 220 (not shown). The structure 443 on the underside 442 of the light guide area 440 can, for example, be a microlens structure, roughness structure, mirror structure, or a grating structure, e.g., a reflection grating. The structure 443 is formed on the outside of the underside 442 of the light guide area 440. In the two adjacent areas, the deflection area 450 and the adjacent light guide area 440, sufficient, homogeneous backlighting can thus be achieved over the entire length 401 of a display panel 200 (not shown).

[0049] In Fig. Figure 4 shows a sectional view of the coupling area 410 with the stepped structure 420 of an optical fiber 400 according to the invention, enlarged for better understanding than is necessary for an actual realization of the optical fiber 400. In an exemplary embodiment, the stepped structure 420 has four steps. The stepped structure 420 is formed on the outside of the coupling area 410 in the direction of the optical fiber area 440, between the coupling surface 411 of the coupling area 410 and the underside 442 of the optical fiber area 440.

[0050] Each of the four stages has a leg 430-433 and a flank 434-437. The legs 430-433 have an angle α1-α4 with respect to the perpendicular of the coupling surface, measured in direction 460 of the light guide area 440, of less than 42.5°.

[0051] Calculations have shown that optimal backlighting of the display panel (not shown) is achieved when the first stage 421, which connects to the coupling surface 411 of the coupling area 410, has a first leg 430 at an angle α1 to the perpendicular of the coupling surface 411 between 24.1° and 25.1°. In the exemplary embodiment, the first leg 430 preferably has an angle α1 of 24.6°. Furthermore, the second stage 422, which follows the first stage 421, has a second leg 431 at an angle α2 to the perpendicular of the coupling surface 411 between 19.3° and 20.3°. In the exemplary embodiment, the second leg 431 preferably has an angle α2 of 19.8°. The third stage 423, which follows the second stage 422, has a third leg 432 at an angle α3 to the perpendicular of the coupling surface 411 between 16.3° and 17.3°.In the exemplary embodiment, the third leg 432 preferably has an angle α3 of 16.8°. Finally, the fourth stage 424, which follows the third stage 423, has a fourth leg 433 at an angle α4 to the perpendicular of the coupling surface 411 between 11.3° and 12.3°. In the exemplary embodiment, the fourth leg 433 preferably has an angle α4 of 11.8°.

[0052] The angles α1-α4 of the individual legs 430-433 become increasingly acute from the coupling surface 411 towards the underside 442 of the light guide area 440, thereby distributing the light 301 striking the surfaces of the legs 430-433 evenly and achieving optimal backlighting in the deflection area 450 of the light guide 400. This has the advantage that the light 301 coupled into the coupling area 410, after striking the individual surfaces of the legs 430-433, is deflected at a specific angle towards the deflection surface 451 and coupled out of the light guide 400 again, so that homogeneous, planar backlighting occurs in this area above the deflection area 450.

[0053] The flanks 434-437 of the stepped structure 420 according to the invention have an angle β greater than 43° relative to the perpendicular of the coupling surface, measured opposite the direction 460 of the light guide area 440. In the preferred embodiment, the individual flanks 434-437 have an angle β in an angular range between 43° and 90°, so that excess light 302, particularly in the edge region of the coupling area 410, is coupled out of the coupling area 410 and thus out of the light guide 400 via the flanks 434-437. This prevents over-illumination of the display panel 200 (not shown) in this area. The light 301 coupled in at the edge region of the coupling area 410 thus strikes the flanks 434-437. An optimal result for the extraction of light 301 in the edge region is achieved when the surfaces of the flanks 434-437 are aligned at 90° perpendicular to the coupled light 301.

[0054] Due to the stepped structure 420, the coupling area 410 can be adapted to the specific design of a display device, in particular to the size of a display panel 200 which is to be backlit, by simply adjusting the individual angles α1-α4 of the legs 430-433 and the individual angles β of the flanks 434-437, i.e. the height of the coupling area 410 can be varied in a simple way.

[0055] Fig. Figure 5 shows, for better understanding, an enlarged oblique view from the front of part of an embodiment of a coupling area 410 with a stepped structure 420 of an optical fiber 400 according to the invention. The coupling area 410 with the stepped structure 420 according to the invention is largely identical to the one described previously in Fig. 4 shown coupling area 410. In an exemplary embodiment, the step structure 420 shows four steps.

[0056] The individual stages 421-424 are formed on the outside of the coupling area 410. The individual stages 421-424 extend over the width z of the optical fiber 400. The coupling area 411 also extends over the width z of the optical fiber 400. The first stage 421 is followed by a second stage 422, a third stage 423, and a fourth stage 424. Each of the four stages 421-424 has a leg 430-433 and a flank 434-437. Each of the stages 421-424 has a radius ri at the transition between the respective flank 434-437 and the respective leg 430-433. Furthermore, each stage has a radius ra on its outside at the transition between the respective flank 434-437 and the respective leg 430-433. The two radii ri, ra serve to ensure that the light guide 400 can be easily demolded during the manufacturing process and that no damage occurs to the step structure 420.Such damage can cause unwanted scattered light to form in this region of radii ri, ra. The individual legs 430-433 and flanks 434-437 exhibit different angles α1-α4, β as well as different surface sizes.

[0057] Fig. Figure 6 shows a section through a display device 100 with a light guide 400 according to the invention in the assembled state. In this embodiment, the light source 300, whose light 301 is to be distributed by the light guide 400, is arranged on a circuit board 700 of the display device 100. As shown in Fig. 3 and Fig. As described in Figure 4, the light 301 emitted by the light source 300 is coupled into the coupling area 410 and thus into the optical fiber 400 via a coupling surface 411. A portion of the coupled light 301 is deflected by the stepped structure 420 formed in the coupling area 410 according to the invention, or rather by the legs 430-433 formed in the stepped structure 420, onto the light deflection surface 451 of the optical fiber 400. When the light 304 coming from the stepped structure 420 strikes the light deflection surface 451, total internal reflection does not occur; instead, the light 304 striking the surface exits the optical fiber 400 almost completely in the region of the deflection surface 451 at a defined angle. A further portion of the coupled-out light 302, 303 in the edge region of the coupling area 410 is coupled out of the optical fiber again.The light 302, 303 coupled out of the light guide 400 strikes the reflector 800, 801 and is directed away from the light guide 400 and thus away from the display panel 200. Another portion of the coupled light 301 is guided via the light deflection surface into the light guide area 440 of the light guide 400. Due to the parabolic light deflection surface 451, the deflected light 305 is distributed homogeneously within the light guide area 440. The light 305 deflected into the light guide area 440 is further deflected towards the top of the light guide 400, where, after exiting the light guide 400, it serves to backlight a display panel 200. As in . Fig. As shown in Figure 6, due to the step structure 420 according to the invention, the display panel 200 is backlit homogeneously over the entire length 401 of the light guide 400.

[0058] Fig.Figure 7 shows a section through an optical fiber 400 according to the invention with the step structure 420 formed in the coupling area 410. The distribution of the coupled light 301 in the optical fiber 400 is shown in a diagram based on the amount of light indicated on the y-axis (usually measured in luminance [cd / m²]). 2The diagram shows the light distribution over the length 401 of the light guide 400, as indicated on the x-axis. As can be seen in the diagram, the display panel 200 is backlit homogeneously over the entire length 401 of the light guide 400. The light 304 coupled out at the deflection point 450 and the light 305 redirected into the light guide area 440 are distributed evenly over the entire length 401 of the light guide 400. The amount of light indicated on the y-axis is therefore constant over the length 401 of the light guide 400, as indicated on the x-axis. The light 304 coupled out at the deflection point 450 and the light 305 emitted in the light guide area 440 form a homogeneous amount of light and overlap in the required quantity, resulting in homogeneous backlighting between the deflection point 450 and the light guide area 440.

[0059] Overall, this example demonstrates how the invention allows for the simple design of a light guide with the inventive stepped structure in the coupling area, enabling the achievement of a uniform, homogeneous backlighting of a display panel at the required intensity without the need to block stray light with a baffle. Due to the stepped structure and the arrangement of the individual steps at different angles, otherwise undesirable stray light can be easily used to backlight a display panel. This allows for the realization of larger displays with a very small bezel. Reference symbol list 100 Display device 200 Display Panels 300 light sources 301 coupled light 302 extracted light 303 extracted light 304 extracted light 305 deflected light 306 Stray light 400 fiber optic cables 401 Length of optical fiber 410 coupling area 411 Coupling area 420-step structure 421st level 422nd level 423 level 424th level 430 thighs 431 thighs 432 thighs 433 thighs 434 flank 435 flank 435 flank 437 flank 440 light guide area 441 Top 442 Underside 443 Structure 450 deflection range 451 Light deflection surface 460 axle 470 aperture 700 printed circuit boards 800 reflector 801 Reflector ri radius inside ra radius outside x-axis length of optical fiber y-axis amount of light y' Height of optical fiber z wide optical fibers α1 angle α2 angle α3 angle α4 angle β angle

Claims

[1] Light guide (400) for a display device (100) with a display panel (200), wherein the optical fiber (400) has a coupling area (410) with a coupling surface (411) for coupling light (301) from a light source (300), wherein the light guide (400) has a deflection area (450) with a light deflection surface (451) for deflecting the light (301) into a light guidance area (440) for guiding the light (301) along an axis (460), wherein the light-guiding area (440) has a top surface (441) which is designed parallel to the axis (460) and a bottom surface (442) which is inclined relative to the axis (460) and has a structure (443) for deflecting the light (301) incident on the bottom surface (442) towards the top surface (441), wherein the light guide (400) has a reflector (800) which extends over the entire length of the light guide area (440), and wherein the coupling area (410) has a step structure (420) which has at least one leg (430) and at least one flank (434), characterized by , that the leg (430) is designed to deflect the coupled light (301) incident on a surface of the leg (430) onto the light deflection surface (451) of the light guide (400), the flank (434) is configured to couple the coupled light (301) incident on a surface of the flank (434) out of the coupling area (410) and thus out of the optical fiber (400), and to direct the light (302) coupled out through the flank (434) onto the reflector (800), and the reflector (800) is designed to direct the light (302) coupled out through the flank (434) away from the light guide (400). [2] Optical fiber (400) according to claim 1, characterized by, that the leg (430) has an angle (α1) less than 42.5° to the perpendicular of the coupling surface (411). [3] Optical fiber (400) according to one of the preceding claims 1 and 2, characterized by , that the flank (434) has an angle (β) relative to the perpendicular of the coupling surface (411) greater than 43°, preferably an angle (β) in an angular range between 43° and 90°. [4] Optical fiber (400) according to any one of the preceding claims 1 to 3, characterized by , that the step structure (420) has at least four steps (421 to 424), each of which has a leg (430 to 433) and a flank (434 to 437). [5] Optical fiber (400) according to claim 4, characterized by , that a first stage (421) has a first leg (430) at an angle (α1) to the perpendicular of the coupling surface (411) between 24.1° and 25.1°, preferably 24.6°. [6] Optical fiber (400) according to claim 4, characterized by, that a second stage (422) following the first stage (421) has a second leg (431) at an angle (α2) to the perpendicular of the coupling surface (411) between 19.3° and 20.3°, preferably 19.8°. [7] Optical fiber (400) according to claim 4, characterized by , that a third stage (423) following the second stage (422) has a third leg (432) at an angle (α3) to the perpendicular of the coupling surface (411) between 16.3° and 17.3°, preferably 16.8°. [8] Optical fiber (400) according to claim 4, characterized by , that a fourth stage (424) following the third stage (423) has a fourth leg (433) at an angle (α4) to the perpendicular of the coupling surface (411) between 11.3° and 12.3°, preferably 11.8°. [9] Light guide (400) for a display device (100) with a display panel (200), wherein the optical fiber (400) has a coupling area (410) with a coupling surface (411) for coupling light (301) from a light source (300), wherein the light guide (400) has a deflection area (450) with a light deflection surface (451) for deflecting the light (301) into a light guidance area (440) for guiding the light (301) along an axis (460), wherein the light guide area (440) has a top surface (441) which is designed parallel to the axis (460) and a bottom surface (442) which is inclined relative to the axis (460) and has a structure (443) for deflecting the light (301) incident on the bottom surface (442) towards the top surface (441), and wherein the coupling area (410) has a step structure (420), characterized by , that the step structure (420) has at least four steps (421 to 424), each of which has a leg (430 to 433) and a flank (434 to 437), a first stage (421) has a first leg (430) at an angle (α1) to the perpendicular of the coupling surface (411) between 24.1° and 25.1°, preferably 24.6°, a second stage (422) following the first stage (421) has a second leg (431) at an angle (α2) to the perpendicular of the coupling surface (411) between 19.3° and 20.3°, preferably 19.8°, a third stage (423) following the second stage (422), having a third leg (432) at an angle (α3) to the perpendicular of the coupling surface (411) between 16.3° and 17.3°, preferably 16.8°, and a fourth stage (424) following the third stage (423) has a fourth leg (433) at an angle (α4) to the perpendicular of the coupling surface (411) between 11.3° and 12.3°, preferably 11.8°.

Images