System for illuminating multi-pixel display device

Abstract

An optical homogenization plate (1) for illuminating a multi-pixel display device (10), such as a liquid crystal screen. A speckle noise suppression unit (3, 300) is provided for reducing speckle noise before light is coupled into the homogenization plate (1). This type of component can be used in a picture generation device of an HUD system.

Description

Technical Field

[0001] Various aspects of this disclosure relate to a system for illuminating a multi-pixel display device, such as that used in a HUD system. In particular, various aspects of this disclosure relate to a system for illuminating a multi-pixel display device, the system having a speckle noise suppression unit. Background Technology

[0002] Transparent screen units are used in various applications. For example, they are used in HUD (Head-Up Display) systems in motor vehicles. HUD systems generate virtual images, allowing drivers to perceive displayed information without taking their eyes off the road. The virtual image is generated in a virtual image plane, unlike a real image displayed on a physical surface (e.g., a transparent surface). In HUD systems, this virtual image plane is located outside the vehicle. The area within which the driver can perceive the virtual image is called the eye-tracking range.

[0003] The transparent screen unit includes a picture generation unit (PGU). The PGU includes a multi-pixel display device, such as a liquid crystal display or a micromirror array. The multi-pixel display device is illuminated by a light source.

[0004] Narrow-band or monochromatic light sources are typically used. This is especially true when using holographic optical elements (HOEs). This is due to the wavelength-selective diffraction characteristics of HOEs. The diffraction efficiency of a HOE is a function of wavelength.

[0005] Therefore, laser light sources are commonly used as light sources with high luminous flux. However, these light sources introduce a significant amount of speckle noise into the image plane due to their coherence. Speckle noise diminishes the visual impression of the image. Summary of the Invention

[0006] Systems (illumination systems) for illuminating multi-pixel display devices are needed, which reduce speckle noise. Compact illumination systems that can be integrated into limited installation spaces are required. Illumination systems that illuminate multi-pixel display devices with a desired light distribution on the display plane are also needed.

[0007] This problem is addressed by the features of the independent claims. The features of the dependent claims define the embodiments.

[0008] The following describes an optical system and arrangement for illuminating a multi-pixel display device. This system can suppress speckle noise. The illumination intensity in the pixel plane of the multi-pixel display device can be set in a targeted manner. A compact structure is possible. This system and arrangement can be used as a PGU in a head-up display (HUD) system with a multi-pixel display device. In various variations, multiple diffuser elements arranged in series are used. These diffuser elements are positioned upstream of the multi-pixel display device along the light beam path, enabling adaptive illumination of the pixel plane of the multi-pixel display device.

[0009] According to various examples, light is modified in stages by passing through multiple optical elements. For example, the light may pass through two or more diffusers. Therefore, the pixel plane of a multi-pixel display device can be illuminated with a desired light distribution. The multi-pixel display device has emission characteristics set by illuminating the pixel plane using multiple optical elements.

[0010] For example, multiple diffusers can be arranged sequentially. A first diffuser can implement a speckle noise suppression unit. For this purpose, the diffuser can be moved, for example, within a kHz range. A second diffuser can be configured to properly illuminate a third diffuser. The third diffuser can have emission characteristics adapted to an optical imaging system arranged downstream of a multi-pixel display device in the optical path. For example, the corresponding entrance pupil of the optical imaging system can be properly illuminated.

[0011] In this configuration, the various segments of the light beam path can be guided within the optical block or implemented as a free beam. Using an optical block to guide the light typically allows for a more compact arrangement.

[0012] A system for illuminating the pixel plane of a multi-pixel display device is disclosed.

[0013] The system includes a laser source. For example, the laser source may include a single emitter, such as a laser diode. A multicolor laser source may also be used; for example, such a multicolor laser source may include three emitters that provide light at red, green, and blue wavelengths.

[0014] Typically, laser sources are configured to provide phase-coherent light. This can then lead to speckle noise.

[0015] The system also includes a speckle noise suppression unit. As a general rule, different types of speckle noise suppression units can be used. One implementation involves using a moving diffuser, whereby the speckle pattern is "averaged out." However, other types of speckle noise suppression units exist, such as liquid crystal light modulator elements. The phase profile of the laser can be altered, particularly randomized, by the speckle noise suppression unit. Typically, active devices (i.e., devices including motors or actuators that move one or more elements) can be used as speckle noise suppression units.

[0016] For example, the speckle noise suppression unit can take the form of a diffuser that moves within the kHz range.

[0017] The system also includes an optical waveguide that guides the coherent light emitted by the light source toward the speckle noise suppression unit. Specifically, optical fiber can be used as the optical waveguide. For example, multimode fiber can be used. An output coupling lens element can be positioned at the end of the optical waveguide facing the speckle noise suppression unit.

[0018] The system also includes an optical homogenization plate. The optical homogenization plate includes a top side, a bottom side, and (at least) one side side. Therefore, the side side is positioned at the edge between the top and bottom sides. The thickness of the optical homogenization plate can be defined as the distance between the top and bottom sides. In a system integrated into a PGU within a HUD system, the top side may face the multi-pixel display device. The homogenization plate may be made of acrylic glass or glass. The homogenization plate comprises a planar, optically transparent substrate.

[0019] The system includes an input coupling structure. The input coupling structure is formed on the side of a homogenization plate, adjacent to a speckle noise suppression unit. The input coupling structure is configured to couple light input from the speckle noise suppression unit into the homogenization plate. As a separate component, the input coupling structure can be adhesively bonded to or otherwise applied to the side of the homogenization plate. However, the input coupling structure can also be formed as a surface topography variation on the side of the homogenization plate.

[0020] The system further includes an output coupling structure. The output coupling structure is formed on the top side of the homogenization plate. The output coupling structure is configured to output coupled light from the homogenization plate in a manner distributed over the entire area of ​​the output coupling structure for illuminating a multi-pixel display device. This means that a specific light field can be obtained through the output coupling structure, i.e., a specific intensity distribution depending on a location along the surface of the homogenization plate. Therefore, suitable illumination of the pixel plane of the multi-pixel display device can be achieved. Specifically, the pixel plane of the multi-pixel display device can be illuminated over its entire area, i.e., all pixel elements are illuminated at any given time, and there is no sequential illumination of different pixel elements.

[0021] Because of the use of a homogenizing plate with an output coupling structure, a particularly compact illumination unit can be implemented, for example, especially compared to a free beam path.

[0022] The output coupling structure can be specifically implemented as a diffuser. Light is scattered by the diffuser, and thus specific emission characteristics are obtained.

[0023] As a general rule, diffusers can be implemented in various ways, such as as microstructure diffusers, holographic diffusers, volumetric diffusers, and diffusers based on surface undulations. Diffusers can be made of different materials, including plastics, glass, and optionally have coatings.

[0024] As described above, using multiple diffusers (spot noise suppression units and output coupling structures) makes it possible to obtain the desired illumination of the pixel plane.

[0025] Therefore, the system for illuminating the pixel plane of a multi-pixel display device includes a laser source. The laser source is configured to emit light along a beam path. The system also includes a speckle noise suppression unit, which is implemented as, for example, a movable diffuser. The speckle noise suppression unit is arranged in the beam path. The system further includes a diffuser. The diffuser is arranged downstream of the speckle noise suppression unit in the beam path starting from the laser source and is configured to emit light with emission characteristics in the direction of the multi-pixel display device.

[0026] Therefore, a diffuser first positioned on the beam path suppresses speckle noise. Thus, a diffuser positioned on the beam path adjacent to the pixel plane of the multi-pixel display device achieves the desired emission characteristics: first illuminating the pixel plane, and then illuminating the entrance pupil of the optical imaging system positioned downstream of the multi-pixel display device on the beam path.

[0027] Optionally, another diffuser may be present, and if present, this additional diffuser is arranged between the speckle noise suppression unit and the diffuser (close to the display device), and is configured to emit light with additional emission characteristics in the direction of the diffuser arranged adjacent to the display device. This additional emission characteristic can be configured to achieve full-area illumination of the aperture of the diffuser arranged adjacent to the display device.

[0028] Such a system, as described above, can be part of the PGU (Power Mirror Unit) of a HUD (Head-Up Display) system. A HUD system may include one or more HOEs (Holes of Images) along the light beam path. The multi-pixel display device can be, for example, a liquid crystal display or a micromirror array.

[0029] The one or more HOEs may perform different functions. For example, it is conceivable that the one or more HOEs are part of or implement a wavefront manipulator, as described in WO 2022 / 189275 A1 (where the wavefront manipulator is referred to as a holographic element), the corresponding disclosure of which is incorporated herein by cross-reference.

[0030] For example, the corresponding wavefront manipulator may include two HOEs arranged directly and successively in the beam path. In other words, no additional optical elements or components are arranged between the two HOEs. The two HOEs are further configured to be reflective for at least one defined wavelength and a defined angle of incidence range. Therefore, light waves having at least one defined wavelength and within the defined angle of incidence range are efficiently diffracted. Preferably, the holographic element is configured to be transmissive for the remaining wavelengths; in other words, it is transmissive for wavelengths that do not correspond to the at least one defined wavelength and have angles of incidence exceeding the defined angle of incidence range. Using two HOEs with at least a partially reflective configuration and arranged directly and successively has various advantages. For example, one advantage is that the image quality can be significantly improved by the individual configuration of the HOEs, especially in conjunction with a head-up display. For this purpose, the HOEs occupy almost no installation space; therefore, when only a very small amount of available installation space exists, such as in the case of a head-up display designed for a motor vehicle, a significant improvement in image quality (compared to implementations without HOEs) can be achieved, for example, by means of a suitable wavefront manipulator. Holographic arrangements achieve high refractive power, particularly comparable to that achieved, for example, by optical components configured to be transmissive and chromatic aberration-free. Compared to transmissive holograms, reflective HOEs for a defined wavelength offer a wider angular spectrum, higher efficiency, and greater wavelength selectivity. Therefore, despite the wider incident angular spectrum, color channels can still be separated from each other. Consequently, holographic arrangements can achieve a large field of view while maintaining high efficiency, making them suitable for VR head-up displays (VR - virtual reality) and augmented reality head-up displays (AR HUDs) with large fields of view and large numerical apertures. Further application possibilities are offered by head-up displays with curved projection surfaces, such as head-up displays for windshields of vehicles (particularly motor vehicles, aircraft, or ships), and head-up displays generally used for viewing windows. While various variations using one or more HOEs in the optical imaging system of a HUD system are described below, corresponding techniques for the image generation unit can also be used in conjunction with non-holographic HUD systems.

[0031] Without departing from the scope of protection of this invention, the features set forth above and described below may be used not only in the expressly stated applicable combinations, but also in other combinations or individually. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of an exemplary system for illuminating a multi-pixel display device.

[0033] Figure 2 yes Figure 1 Another side view of the exemplary system.

[0034] Figure 3 yes Figure 1 A three-dimensional diagram of an exemplary system.

[0035] Figure 4 The illumination intensity provided by the system along the pixel plane of the multi-pixel display device is shown.

[0036] Figure 5 The exhibition showcases various examples of systems for illuminating multi-pixel display devices and HUD systems for multi-pixel display devices.

[0037] Figure 6 It is a (normalized) polar plot showing two possible angular distributions of the emission characteristics of a system used to illuminate a multi-pixel display device.

[0038] Figure 7 Local variations in emission characteristics are illustrated using multiple polar plots based on the corresponding angular distributions of various examples.

[0039] Figure 8 Local variations in emission characteristics are illustrated using multiple polar plots based on the corresponding angular distributions of various examples.

[0040] Figure 9 The speckle noise suppression unit is illustrated schematically according to various examples.

[0041] Figure 10 The diagram illustrates HUD systems based on various examples.

[0042] Figure 11 This is a schematic diagram of an exemplary system for illuminating a multi-pixel display device.

[0043] Figure 12 It comes from Figure 11 A three-dimensional diagram of the system's structural implementation. Detailed Implementation

[0044] In the context of the following description of exemplary embodiments, the features, characteristics, and advantages of the invention described above, as well as the ways of achieving these features, characteristics, and advantages, will become clearer and more apparent, with reference to the accompanying drawings.

[0045] Figure 1A system 100 for illuminating a multi-pixel display device 10 is schematically shown. Laser light (e.g., red-green-blue channels or fewer or more channels) from a laser source 19 is coupled into a speckle noise suppression unit 3 (implemented here as a dynamically moving diffuser) via an optical waveguide 4. For this purpose, a lens element (e.g., a GRIN lens) may optionally be positioned at a suitable end of the optical waveguide 4. The emission characteristics of such a lens element can vary depending on the application. The lens element can provide collimation. For example, a lens element with collimation characteristics adapted to the input angle range of the speckle noise suppression unit 3 can be provided. In particular, dispersion must be considered here. In an alternative to the above scheme or further, a parabolic mirror can be used for beam spreading and collimation between the end of the optical waveguide 4 and the speckle noise suppression unit 3.

[0046] For example, together with system 100, the multi-pixel display device 10 can be part of the PGU of the HUD system. Together with system 100, the multi-pixel display device 10 can also be envisioned as part of a holographic diffuser. In such a holographic diffuser, an image is generated in an image plane arranged on a transparent surface. For example, a see-through screen can be implemented in this way.

[0047] Specifically, in this application scenario, there may be one or more HOEs that apply one or more optical effects to light through diffraction. For example, light can be deflected or collimated. These one or more HOEs require a light source emitting narrowband or monochromatic light. For this purpose, lasers are typically used as the light source. Coherent light can be prone to speckle noise.

[0048] Speckle noise (also known as optical granulation or laser granulation, or simply speckle) refers to the granular interference phenomenon that can be observed when a fully coherently illuminated optically rough object surface (with inhomogeneities on the order of wavelength).

[0049] The diffuser implementing the speckle noise suppression unit 3 moves randomly in two lateral directions perpendicular to the axis of the optical waveguide, for example, randomly relative to both the optical waveguide 4 and the rest of the setup. For example, the moving frequency can be adjustable. In this way, speckle noise can be effectively suppressed.

[0050] Subsequently, light is input-coupled into the transparent substrate of the optical homogenization plate 1 (e.g., made of glass or plastic) through the input coupling structure 2 (which may also be referred to as the light redistribution structure). The input coupling structure 2 is arranged on the side 23 of the homogenization plate 1, directly adjacent to the speckle noise suppression unit 3. This allows for a compact structure; additional collimating lens elements, etc., can be omitted.

[0051] The typical thickness of the homogenization plate 1 is in the range of 5 mm to 20 mm, preferably in the range of 10 mm to 20 mm.

[0052] The input coupling structure 2 can be applied as a separate component to the homogenization plate 1. For example, the input coupling structure 2 can take the form of a micropillar lens array.

[0053] Typically, a micropillar lens array comprises a 1D or 2D array of micropillar lens elements (micropillar lenses) configured to refract light in different directions. For example, a 1D array can be used in which the micropillar lenses are arranged to be spaced apart from each other in a first direction and extend in a second direction perpendicular to the first direction.

[0054] The input coupling structure 2 can take the form of, for example, a film (e.g., a micropillar lens array film). However, the input coupling structure 2 can also be integrally formed with the homogenization plate 1, i.e., formed as a single component. For example, the side surface 23 can be formed with a suitable surface morphology (e.g., as an indented micropillar lens array on the side surface 23).

[0055] On the lower side 22 of the optical homogenization plate 1, the light guide substrate of the optical homogenization plate is provided with an additional transparent light redistribution structure 5, which redistributes the light field according to the desired design specifications, for example by multiple scattering and reflection 9.

[0056] The light redistribution structure 5 can be applied as a separate component to the homogenization plate 1. The light redistribution structure 5 can be implemented directly in the substrate, for example, in the form of a spherical (hemispherical) or elliptical protrusion or depression, but it can also be implemented by bonding a structural film with a refractive index-matched adhesive. Alternatively, the light redistribution structure 5 can take the form of, for example, a film (e.g., a micropillar lens array film). However, the light redistribution structure 5 can also be integrally formed with the homogenization plate 1, i.e., formed as a single component. For example, the lower side 22 can be formed with a suitable surface morphology (e.g., as a micropillar lens array in the form of indentations).

[0057] For example, the design specifications of the lateral uniformity and spatial alignment (emission characteristics of the homogenization plate 1) of the light field 8 emitted by the homogenization plate 1 can be set by the configuration, arrangement, size, and / or quantity of this light redistribution structure (the main emission direction 205—perpendicular to the surface of the homogenization plate 1—is also indicated by reference numerals). The following will combine... Figure 4 and Figure 6 Describe the details related to the light intensity of the light field 8 as it changes with its position on the homogenization plate, and the emission characteristics of the light field 8.

[0058] A reflector structure 6 is disposed below the light redistribution structure 5. This reflector structure, in the form of a reflective layer, is used to reduce light loss on the lower side 22 of the optical homogenization plate 1. The reflector structure 6 deflects light back towards the optical homogenization plate 1. The reflector structure 6 can be adhesively bonded to the light redistribution structure 5, for example, as a reflective film. The reflector structure 6 can also be produced, for example, as a metal vapor deposition (thin film) using aluminum.

[0059] Optionally, an output coupling structure 7 can be used on the top side 21 of the homogenization plate 1 to specifically set the angular distribution of the light field leaving the homogenization plate. The output coupling structure can take the form of a diffraction diffuser. Therefore, in this scenario, multiple diffuser elements arranged in series are used, specifically, a diffraction diffuser implementing the output coupling structure 7 and a diffuser implementing the speckle noise suppression unit 3.

[0060] A suitable design of the output coupling structure 7 allows for customized illumination of the pixel plane 11 of the multi-pixel display device 10. For example, the pixels of a liquid crystal display (e.g., a thin-film liquid crystal display (TFT display)) are arranged in the pixel plane 11.

[0061] The output coupling structure 7 can be applied as a separate component to the homogenization plate 1. The output coupling structure 7 can take the form of, for example, a film. However, the output coupling structure 7 can also be integrally formed with the homogenization plate 1, i.e., formed as a single component. For example, the top side 21 can be formed with a suitable surface morphology.

[0062] In various examples, in particular, the optical homogenization plate 1 can be manufactured as a single integral part together with the output coupling structure 7, the input coupling structure 2, and the light redistribution structure 5. For example, such an integral part can be manufactured from a block of free plastic. For example, 3D printing or injection molding methods can be considered as manufacturing techniques.

[0063] To suppress the visibility of the diffuser features of the output coupling structure 7 to the human eye—that is, for example, the structured surface of the output coupling structure—it can be advantageous to decouple (i.e., space) the pixel plane 11 from the output plane or the output coupling structure 7 (see gap 12). For this purpose, gap 12 preferably has an extension range in the range of approximately 20 mm to 100 mm, optionally in the range of 25 mm to 25 mm, and further optionally in the range of 30 mm. Therefore, gap 12 is typically larger than the thickness of the homogenization plate 1. For example, gap 1 has an extension range of approximately 100% to 150% of the thickness of the homogenization plate 1, since the homogenization plate 1 typically has a thickness between 5 mm and 20 mm. However, in this context, the size setting of gap 12 does not depend on the thickness of the homogenization plate 1, but rather on the positioning of the virtual image plane: this will be explained below.

[0064] The human eye—for example, in the case of a HUD system—adapts to a virtual image plane. This virtual image plane is imaged onto the pixel plane 11. Therefore, this means that structures spaced from the pixel plane 11 at a distance greater than the depth of field—for example, diffuser features of the output coupling structure—are imaged only very vaguely and are therefore imperceptible (or in any case, not perceived as unpleasant). This is particularly advantageous for magnifying optical systems (e.g., HUD systems). In this case, the pixel plane 11 is imaged onto the virtual image plane in a magnified manner. Magnifications of 10x or greater (e.g., 15x or greater) are conceivable. In augmented reality applications, the virtual image plane can be virtually located at infinity (eye accommodation distance > 5 m) and has a large extension range within the eye's field of vision. Typically, distances between the eye's range of motion and the virtual image plane exceeding 5 m, or exceeding 10 m, or exceeding 20 m are conceivable. In this scenario, if the gap 12 is set to be particularly small, such that the diffuser feature of the output coupling structure 7 lies within the depth of field, the feature will appear particularly large and therefore be perceived as particularly unpleasant in the observer's field of vision. Typically, the gap 12 can be set to be as large as needed (without a significant diffuser feature), but as small as possible (for compact installation space).

[0065] Furthermore, the pixel plane 11 can be tilted or inclined relative to the homogenization plate 1.

[0066] Figure 2 It comes from Figure 1 A side view of System 100. From Figure 2 It is evident that the lateral extension range of the input coupling structure 2 is smaller than the extension range of the side surface 23 of the homogenization plate 1, that is, in Figure 2 The z-axis direction is along the long side of side 23. For example, in Figure 2 In the example, the input coupling structure 2 covers approximately 70% of the side surface 23. Typically, it is conceivable that the lateral extension of the input coupling structure 2 is no greater than 80%, 70%, or 50% of the side length of the side surface 23. However, in other examples, it is also conceivable that the input coupling structure 2 covers the entire side surface 23. The lateral extension of the input coupling structure 2 can be equal to the side length of the side surface 23. Furthermore, the aperture of the speckle noise suppression unit 3 is smaller than the lateral extension of the input coupling structure 2. Typically, the lateral extension of the speckle noise suppression unit 3 can, for example, not exceed 20% of the area of ​​the input coupling structure 2. Even though the speckle noise suppression unit 3 typically has a relatively limited extension relative to the side surface 23, relatively large-area input coupling of light to the homogenization plate 1 can be implemented through the input coupling structure 2. The extension (width on the side surface) and texture (micropillar lens texture, prism texture) of the input coupling structure 2 can be variably adapted (design freedom). For example, the input coupling structure 2 may include one or more prism structures; these act as scattering geometry for light that has already been input-coupled and internally reflected / scattered. Therefore, at the location of the input coupling structure 2, the emission characteristics of the homogenization plate 1—that is, the light distribution at the output coupling structure 7, such as uniformity—may be affected. Light is also further redistributed within the homogenization plate 1, for example, by the light redistribution structure 5. For this reason, the lateral extension of the input coupling structure 2 does not necessarily have to completely cover the entire length of the side surface 23. Figure 3 This is also clearly seen in the 3D diagram of System 100.

[0067] Figure 4 The light intensity in pixel plane 11 is shown (in Figure 4 In the diagram, the extent of the pixel plane 11 is indicated by a double arrow. In this case, the light intensity is determined by the emitted light field 8 (e.g., as an integral over all solid angles, with...). Figure 4 The same applies in the same direction, or only for the main launch direction 205). From Figure 4 It is evident that a constant light intensity over the extended range of pixel region 11 can be achieved by appropriately shaping the light field 8 (e.g., through appropriate configuration of the output coupling structure 7 and / or the light redistribution structure 5 and / or the input coupling structure 2). In other variations, it is also conceivable that the light intensity has different local dependencies, for example, having a peak at the center of pixel plane 11, or that the light intensity has multiple different maximum and minimum values.

[0068] Figure 5 The HUD system 200 is illustrated schematically. The HUD system 200 includes a system 100 for illuminating a multi-pixel display device 10 (wherein...) Figure 5(Only homogenization plate 1 is shown). In the figure, pixel plane 11 is tilted relative to homogenization plate 1. For this purpose, the main emission direction 205 of system 100 is shown. Furthermore, Figure 5 Other components of the HUD system 200 along the beam path of light are shown, such as mirror 206, holographic optics 202, windshield 203, and eye-tracking range 204.

[0069] For example, regarding Figure 5 One possible configuration shown in the example demonstrates considerations made at the system level in the HUD system 200, indicating that: (in addition to the spatial dependence of light intensity; see also...) Figure 4 The emission characteristics of the homogenization plate 1 are also crucial to the quality of the image displayed by the HUD system 200. These emission characteristics can be specifically set by using a holographic diffuser as the output coupling structure 7. For example, in Figure 6 Two exemplary emission characteristics 291 and 292 are plotted in polar coordinates using solid and dashed lines (each normalized in amplitude to a common value of the main emission direction 205, which is perpendicular to the surface of the output coupling structure 7, i.e., parallel to the y-axis). The polar coordinates show the amplitude of the light emitted in the corresponding direction (in the xy-plane) in each case. This amplitude distribution in angular space specifies the emission characteristics. Figure 6 The example clearly shows that the width of the angular spectrum of the light field 8 can be set by the output coupling structure 7: Figure 6 The corresponding widths of 295 and 296 were drawn in the middle. Specifically, from... Figure 6 It is evident that the emission characteristics do not completely illuminate the half of the space above the output coupling structure 7; that is, compared to the -90 to +90 reference emission characteristic 299 (dashed line) which uniformly illuminates the entire upper half of the space, the light is emitted in a more directional manner. Therefore, the multi-pixel display device 10 can be illuminated in a targeted manner. It is also conceivable that... Figure 6 As shown, by adjusting the lateral position (e.g., along) Figure 4 The diffraction characteristics of the holographic diffuser (shown on the X-axis) are modified to alter the emission characteristics in the angular spectrum according to the stated position. The image quality of the HUD system 200 can be improved by selecting appropriate emission characteristics 291, 292 (angular spectrum and / or lateral variations).

[0070] Figure 6 This is just one example of emission characteristics. Non-uniform emission characteristics can also be envisioned. The illumination system and the imaging system (HUD) should be matched to each other. That is, the exit pupil of the illumination system and the entrance pupil of the HUD should be matched to each other, so as to achieve the maximum possible luminous flux on the one hand, and avoid vignetting of the illumination system on the other. This may also require non-uniform or asymmetrical emission characteristics.

[0071] For example, Figure 7 and Figure 8 A variant is shown in which the emission characteristics are modified by changing the corresponding angular spectrum 801-805 or 811-815 according to the lateral position along the x-axis (as an alternative to the x-axis or, in addition, along the z-axis). In this case, the width of the angular spectrum remains more or less constant, but the alignment of the main emission direction 205 is tilted, in one case ( Figure 7 Under one condition, it gradually tilts away from the center 7' of the output coupling structure 7, while in another case ( Figure 8 The light gradually tilts towards the center 7' of the output coupling structure 7. This means changing the main emission direction 205 by rotating the angular spectrum 801-805, 811-815 for different x-positions. Vividly speaking, the light's "emission lobe" gradually tilts but maintains approximately the same shape. In the example shown, this is achieved symmetrically about the center 7' of the output coupling structure 7, but in other examples, it can be achieved asymmetrically about the center 7'. Because of this position-dependent change in the main emission direction 205, the entrance pupil or eye-tracking range 204 of the HUD system's optical imaging system can be illuminated to achieve a natural and uniform brightness impression.

[0072] Figure 9 The speckle noise suppression unit 300 is schematically shown. For example, it can be implemented... Figure 1 The speckle noise suppression unit 300 includes a diffuser 301 in the xy plane. Different types of driving devices are conceivable for moving the diffuser 301 in the xy plane. For example, an electric drive device can be used. An electric drive device (also known as an electromagnetic drive device) uses, for example, a coil to generate an alternating magnetic field, in which a magnet subsequently moves. The magnet is connected to the diffuser 301. Figure 9 The diagram shows a corresponding actuator 303 assembled in a fixed reference system (fastening device 304) via a frame. The drive frequency of the electric actuator 303 can be dynamically set over a relatively wide frequency range, thereby resonantly exciting one or more eigenmodes of, for example, a mass spring system (formed by diffuser 301 and return spring 302). Optimal despeckle results can be obtained under this resonant state. This type of drive can be designed as a single-axis or dual-axis system (in... Figure 9 (A dual-axis system is illustrated by way of example). Furthermore, nondeterministic movement can be initiated by one or more vibratory motors (e.g., miniature motors with eccentric flywheel mass on their shafts) connected to the carrier frame of the diffuser.

[0073] The shift frequency should not be less than 100 Hz to achieve a suitable statistical average z. However, the optimal frequency range depends on the diffuser's geometry and mass (the natural frequency of the mass-spring system). Furthermore, psychoacoustic effects should be considered in the design; that is, trade-offs may exist between different objective variables.

[0074] Figure 9 The scenario described is merely one example of a hardware implementation of a speckle noise suppression unit. Typically, the beam path of light can change over time. For this purpose, elements in the beam path (e.g., a diffuser plate, see...) can be implemented... Figure 9 Mechanical movement (e.g., vibration or rotation) of the beam path (or glass fiber). The change in the beam path over time causes the speckle to "diffuse" over time, and this reduces perceived noise. Alternatively, the phase of the incident light can also be modified, for example, by a spatial light modulator (SLM).

[0075] Figure 10 A HUD system 600 according to various examples is schematically shown. The HUD system 600 includes a PGU 601. The PGU 601 includes a laser source 605 configured to emit light along a beam path 606. The laser source 605 corresponds to light emitted from... Figure 1 19. Laser source.

[0076] Light is incident on the speckle noise suppression unit 610. For example, the speckle noise suppression unit 610 can be as follows: Figure 9 Configured as described in (spot noise suppression unit 300).

[0077] Starting from the speckle noise suppression unit 610, light propagates along the beam path 606 to the optical element 615. The optical element 615 is configured to uniformly illuminate the aperture of the diffuser 620. For example, the homogenization plate 1 and the light redistribution structure 5 (see...) Figure 1 Together, this will be an example of optical element 615. Optical element 615 itself can take the form of a diffuser. The following will combine... Figure 11 The corresponding implementation methods will be discussed.

[0078] In this case, diffuser 620 (see Figure 1 The output coupling structure 7) is configured to emit light along the beam path 606 having the following emission characteristics: illuminating the multi-pixel display device 625 (corresponding to...). Figure 1 The pixel plane of the multi-pixel display device 10). Therefore, units 605, 610, 615, and 620 form system 621, which corresponds to, for example, from... Figure 1 System 100.

[0079] Then, light exits PGU 601 along beam path 606 and incidents on optical imaging system 630, which includes, for example, one or more holographic optical elements. Alternatively or in addition to the above, optical imaging system 630 may include, for example, one or more deflection elements or lens elements. The emission characteristics of diffuser 620 are configured such that light illuminates the entrance pupil of optical imaging system 630. Subsequently, the light reaches eye movement range 645, from which a virtual image can be perceived. The above has already been combined with... Figure 6 , Figure 7 and Figure 8 The corresponding technology is described.

[0080] For example, the section of beam path 606 between laser source 605 and speckle noise suppression unit 610 can be implemented at least partially via an optical waveguide (e.g., glass fiber). This has already been incorporated above. Figure 1 The section of beam path 606 between the speckle noise suppression unit 610 and the diffuser 620 is described, showing its extension within the optical block (homogenization plate 1). This achieves a particularly compact design. However, a free-beam implementation is also conceivable. The following section... Figure 11 The corresponding variants are discussed in the paper.

[0081] Figure 11 System 500 is illustrated schematically. System 500 provides connectivity with... Figure 1 The functionality corresponding to the functionality of system 100. System 500 can implement, for example... Figure 10 System 621. However, (with) Figure 1 (Different from China) Figure 11 In this process, a free beam path of light is used to illuminate the multi-pixel plane 506 of the multi-pixel display device 507.

[0082] The light is from laser source 501 (see Figure 1 Laser source 19 and Figure 10 The laser light source 501 generates light. Light propagates from the laser light source 501 towards the speckle noise suppression unit 502. This speckle noise suppression unit can have the same characteristics as... Figure 1 The speckle noise suppression unit 3 or Figure 9 It has the same design as the speckle noise suppression unit 300 in the middle.

[0083] Light can propagate as a free beam between the laser source 501 and the speckle noise suppression unit 502. It is also conceivable that the light is guided by glass fibers.

[0084] The speckle noise suppression unit 502 itself includes a movable diffuser that implements a specific emission characteristic 507. This causes illumination of an additional diffuser 504, which in turn provides an emission characteristic 508. The emission characteristic 508 is configured to achieve uniform illumination of the additional diffuser 505. Therefore, the diffuser 504 undertakes... Figure 1 The functionality of the homogenization plate 1 and the light redistribution structure 5.

[0085] Light can propagate as a free beam between the speckle noise suppression unit and diffuser 504, and between diffuser 504 and diffuser 505.

[0086] Therefore, this is an arrangement of multiple diffuser elements (spot noise suppression unit 502, diffuser 504, and diffuser 505) arranged in series.

[0087] The diffuser 505 has an emission characteristic 509. This emission characteristic 509 can be set to illuminate the entrance pupil of the HUD system's optical imaging system as needed. The emission characteristic 509 can be configured to... Figure 6 , Figure 7 and Figure 8 The example in the text corresponds to the method setting.

[0088] In this configuration, the pixel plane 506 of the multi-pixel detector 507 is illuminated. The multi-pixel detector then acquires emission characteristics 510. [Already combined] Figure 1 The corresponding aspects are discussed with respect to the pixel plane 11 of the multi-pixel detector 510. For example, the main emission direction of the multi-pixel display device 507, or in general, the emission characteristics 510 of the multi-pixel display device 507, can be set by appropriately setting the diffuser 505 or by adapting the emission characteristics 509.

[0089] In summary, the above describes techniques for illuminating multi-pixel display devices; one or more narrow-band and coherent light sources (e.g., lasers or laser diodes) can be used to efficiently illuminate multi-pixel display devices. For example, the PGU of a HUD system can be implemented in this way. Techniques for suppressing speckle noise are described. Techniques allowing uniform illumination of a large image field are described. For this purpose, one or more diffusers are used. Because the light distribution or light field can be flexibly set by appropriately configuring the output coupling structure (e.g., implemented as a diffuser) or input coupling structure (e.g., implemented as a diffuser) or light redistribution structure, high brightness can be achieved. In particular, the corresponding system for illuminating the multi-pixel display device can be arranged at a distance from the pixel plane of the multi-pixel display device (e.g., by translation / parallel shift and / or tilt). The light source can be arranged separately for the optical elements used for light redistribution, which provides flexibility regarding the required installation space and reduces unwanted heat input. Overall, a compact design of the system for illuminating the multi-pixel display device can be achieved, for example, a small thickness perpendicular to the pixel plane of the multi-pixel display device.

[0090] Figure 12 yes Figure 11 A perspective view of a specific embodiment of system 500. Two deflecting mirrors 521 and 522 are also shown.

[0091] It goes without saying that the features of the embodiments and aspects of the present invention described above can be combined with each other. In particular, without departing from the scope of the present invention, these features can be used not only in the described combinations, but also in other combinations or individually.

Claims

1. A system (100, 621) for illuminating a pixel plane (11) of a multi-pixel display device (10, 625), the system (100, 621) comprising: - Laser source (19, 601, 605). - Speckle noise suppression unit (3, 300, 610). - Optical waveguide (4), which guides the coherent light emitted by the laser source (19, 601, 605) toward the spot noise suppression unit (3, 300, 610), - An optical homogenizing plate (1) having a top side (21), a bottom side (22), and a side side (23). - An input coupling structure (2) is formed on the side (23) of the homogenization plate (1) adjacent to the speckle noise suppression unit (3, 300, 610) and is configured to couple the light input from the speckle noise suppression unit (3, 300, 610) into the homogenization plate (1), and - An output coupling structure (7) is formed on the top side (21) of the homogenization plate (1) and is configured to output coupled light from the homogenization plate (1) in a manner distributed over the entire area of ​​the output coupling structure (7) for illuminating the multi-pixel display device (10, 625).

2. The system (100, 621) as described in claim 1. in, The aperture of the speckle noise suppression unit (3, 300, 610) is smaller than the lateral extension of the input coupling structure (2).

3. The system as described in claim 1 or 2 (100, 621). in, The lateral extension range of the input coupling structure (2) is smaller than the extension range of the side (23) of the homogenization plate (1).

4. The system (100, 621) as claimed in any of the preceding claims. in, The speckle noise suppression unit (3, 300, 610) is arranged to be directly adjacent to the input coupling structure (2).

5. The system (100, 621) as described in any of the preceding claims. in, No collimating lens element is arranged between the speckle noise suppression unit (3, 300, 610) and the optical homogenization plate (1).

6. The system (100, 621) as claimed in any of the preceding claims further comprises: - Light redistribution structure (5), which is formed on the lower side (22) of the homogenization plate (1).

7. The system of claim 6 (100, 621) further includes: - A reflector structure (6) that extends along the light redistribution structure (5) on the underside (22) of the homogenization plate (1).

8. The system (100, 621) as claimed in any of the preceding claims. in, The input coupling structure (2) is in the form of a micropillar lens array.

9. The system (100, 621) as claimed in any of the preceding claims. in, The output coupling structure (7) is in the form of a diffuser, and optionally in the form of a holographic diffuser with an adjustable angle range.

10. The system (100, 621) as claimed in any of the preceding claims. in, The input coupling structure (2) and the homogenization plate (1) are integrally formed to form the surface structure of the side (23).

11. The system (100, 621) as claimed in any of the preceding claims. in, The output coupling structure (7) is configured to output and couple the light from the homogenization plate (1) with locally variable emission characteristics (8).

12. The system (100, 621) as claimed in any of the preceding claims. in, The output coupling structure (7) is configured to change the main emission direction (205) according to the position (x, z) on the output coupling structure (7).

13. The system (100, 621) as described in claim 12. in, The output coupling structure (7) is configured such that the main emission direction (205) is tilted symmetrically about the center (7') of the output coupling structure (7) along at least one axis (x, z).

14. The system as described in claim 12 or 13 (100, 621). in, The output coupling structure (7) is configured to change the main emission direction (205) according to the position by rotating the angular spectrum (801-805, 811-815) of the emitted light.

15. The system (100, 621) as claimed in any of the preceding claims. in, The speckle noise suppression unit (3, 300, 610) is an active device.

16. The system (100, 621) as claimed in any of the preceding claims. in, The speckle noise suppression unit (3, 300, 610) includes a resonantly operating mass spring system, which includes a diffuser (301) mounted by one or more springs (302).

17. The system (100, 621) as described in claim 16. in, The natural frequency of the mass spring system of the speckle noise suppression unit (3, 300, 610) is not less than 100 Hz.

18. The system (100, 621) as claimed in any of the preceding claims. in, The output coupling structure (7) is arranged to illuminate the pixel plane over the entire area of ​​the pixel plane of the multi-pixel display device (100, 625).

19. An image generation unit (601) of a head-up display system (600), comprising: - The optical system (100) as described in any of the preceding claims, and - Multi-pixel display device (10,625).

20. The image generation unit (601) as described in claim 19. in, The multi-pixel display device (10, 625) is arranged at intervals with the output coupling structure (7) and the homogenization plate (1). The distance (12) between the multi-pixel display device (10, 625) and the output coupling structure (7) is in the range of 20 mm to 35 mm.

21. The image generation unit (601) as described in claim 19 or 20. in, The pixel plane (11) of the multi-pixel display device (10, 625) is tilted relative to the homogenization plate (1).

22. A head-up display system, comprising: - The image generation unit as described in any one of claims 19 to 21, and - An optical imaging system having holographic optical elements arranged in the beam path of light emitted by the image generating unit.

23. The head-up display system as described in claim 22, in, The output coupling structure (7) is configured to output coupled light from the homogenization plate (1) with emission characteristics (8), which are configured to illuminate the entrance pupil of the optical imaging system.

24. A system (100, 500, 621) for illuminating a pixel plane (506) of a multi-pixel display device (10, 625, 507), the system comprising: - A laser source (19, 601, 605) configured to emit light along the beam path (606), - Speckle noise suppression unit (3, 300, 502, 610), which is arranged on the beam path (606), and - Diffusers (7, 505, 620), starting from the laser source (19, 601, 605), are arranged downstream of the spot noise suppression unit (3, 300, 502, 610) on the beam path (606) and are configured to emit the light in the direction of the multi-pixel display device (10, 625, 507) with emission characteristics (8, 509).

25. The system of claim 24 (100, 500, 621) further comprises: - Another diffuser (615) is arranged in the beam path (606) between the spot noise suppression unit (3, 300, 502, 610) and the diffuser (7, 506, 620), and is configured to emit the light in the direction of the diffuser (7, 505, 620) with another emission characteristic (508), wherein the other emission characteristic (508) is configured to achieve full-area illumination of the aperture of the diffuser (7, 505, 620).

26. The system as described in claim 24 or 25 (500, 621). in, The beam path extends as a free beam between the speckle noise suppression unit and the diffuser.

27. An image generation unit (601) of a head-up display system (600), comprising: - The optical system (100) as claimed in any one of claims 24 to 26, and - Multi-pixel display device (10,625).

28. The image generation unit (601) as described in claim 27. in, The multi-pixel display device (10, 625) is arranged at intervals with the diffuser (7, 505, 620) and is tilted relative to the diffuser.

29. A head-up display system, comprising: - The image generation unit as described in claim 27 or 28, and - An optical imaging system having holographic optical elements arranged in the beam path of light emitted by the image generating unit.

30. An image generation unit for a head-up display system, comprising: - Multi-pixel display device (10,625). - A light source (19, 601, 605), preferably a laser light source, configured to emit light along a beam path toward the multi-pixel display device, and - Multiple diffuser elements (7, 505, 615, 620) are arranged in series between the light source and the multi-pixel display device along the beam path.

31. A head-up display system, comprising: - The image generation unit as described in claim 30 - An optical imaging system having holographic optical elements arranged in the beam path of light emitted by the image generating unit.

32. The head-up display system as described in claim 31, in, The optical imaging system images the pixel plane of the multi-pixel display device onto a virtual image plane at a magnification of at least 10x, and optionally at least 15x.

Images