Projection device

Abstract

The invention relates to a projection device comprising a coherent light source (14R, 14G, 14B), a first diffuser (171, 1703) and a second diffuser (172), which are arranged movably relative to one another, an illumination optical unit (155), an image generator (11) and a projection optical unit (156), furthermore having a projection surface (21). The first diffuser (171, 1703) is arranged in the projection surface (21), and the second diffuser (172) is arranged in the beam path adjacent to the first diffuser (171, 1703).

Description

[0001] Projection device

[0002] The present invention relates to a projection device. Such projection devices are used, for example, in a head-up display for a motor vehicle. A head-up display, also known as a HUD, is a display system in which the viewer can maintain their line of sight because the content to be displayed is projected into their field of vision. While such systems were originally used primarily in the aviation sector due to their complexity and cost, they are now also being installed in large-scale production vehicles in the automotive industry.

[0003] Head-up displays generally consist of an image-generating unit (PGU), an optical unit, and a mirror unit. The image-generating unit creates the image, using at least one display element. Modern head-up displays typically use displays or scanning systems for image generation. Displays can be, for example, LCDs (LC: Liquid Crystal), p-LED displays (LED: Light Emitting Diode), LCoS displays (LCoS: Liquid Crystal on Silicon), or DMD systems (DMD: Digital Micromirror Device). A laser scanning system is an example of a scanning system. The optical unit directs the image onto the mirror unit. The mirror unit is a partially reflective, translucent disc.The viewer thus sees the content displayed by the imaging unit as a virtual image, and simultaneously the real world behind the glass. In automotive applications, the windshield often serves as the mirror unit, its curved shape being taken into account in the display, for example, by pre-distorting the image displayed by the imaging unit. Through the interaction of the optical unit and the mirror unit, the virtual image is a magnified and distorted representation of the image generated by the imaging unit.

[0004] In laser scanning systems, the light from RGB color laser diodes is scanned across the display area by a scanner that, for example, incorporates oscillating MEMS mirrors (MEMS: micro-electro-mechanical system). The image is then generated on the display area by modulating the power of the color laser diodes synchronously with the movement of the mirrors.

[0005] Laser scanning systems offer advantages over LCD-based display solutions, including less complex optics, higher energy efficiency, and lower cooling requirements. As an alternative to RGB color laser diodes, a short-wavelength laser can also be used to scan an RGB wavelength converter in a suitable intermediate image plane.

[0006] With coherent light, such as that emitted by a laser light source, unwanted speckle patterns often appear, which should be reduced or eliminated to achieve a good image. Speckle patterns, light granulation, laser granulation, or simply speckle, refer to the granular interference phenomena that can be observed, for example, when optically rough object surfaces (unevenness on the order of the wavelength) are illuminated with sufficient coherence. In more ordered structures, such as lens arrays, the interfering interference effects can also exhibit a higher degree of order. Here, we use the term speckle or speckle pattern more broadly to include such effects as well.

[0007] The term "speck," which refers to both a single spot of light and the entire interference pattern, is derived from the English word "speckle." Depending on the imaging system used, the predominantly English-language literature also distinguishes between "subjective speckle" and "objective speckle": If the speckle is projected directly onto a screen without the aid of a lens or other optical devices, it is called objective speckle. In contrast, subjective speckle refers to the imaging of the interference pattern using a lens or more complex optical systems. This includes the human eye.

[0008] Against this background, US 2021 / 0048736 A1 describes a projection device comprising a coherent light source, a first diffuser and a second diffuser arranged to be movable relative to each other, illumination optics, an image generator, and projection optics. US 2014 / 285899 A1 describes a projection device according to the preamble of claim 1. It mentions that the diffusion screens can be movable and can be moved in opposite directions to improve the quality of the projected image. The movement is discussed in the context of vibration and the reduction of speckle patterns, with a focus on the vibration amplitude and direction. An improved projection device is desired.

[0009] A projection device according to the invention, comprising a coherent light source, a first diffuser and a second diffuser which are arranged to be movable relative to each other, an illumination optic, an image transmitter and a projection optic, has a projection surface, wherein the first diffuser forms the projection surface and the second diffuser is arranged in the beam path adjacent to the first diffuser.

[0010] A coherent light source is understood to be a light source that emits coherent light, for example, a laser light source. The illumination optics are located downstream of the coherent light source and serve to illuminate the image source with the light coming from the light source. The image source is, for example, a DMD or another type of scanner. A translucent display element, such as a liquid crystal display, or more generally, an element referred to as a light valve, can also serve as the image source. The projection optics project the image generated by the image source onto a projection surface. This can generally also be an intermediate image plane, i.e., a plane in which a viewer does not typically view the projected image. In this case, a further projection surface is present in which a viewer views the projected image.In the case of a head-up display, the additional projection surface lies, for example, in the plane where the viewer sees the virtual image of the head-up display. In the case of a conventional video projector, the additional projection surface lies in the plane of a screen. The diffusers, which move relative to each other, serve to reduce speckle effects that arise from interactions of the coherent light. Thus, speckle effects are suppressed in the intermediate image plane and not in the illumination path itself. Although a larger cross-section must be covered by the diffuser in the intermediate image plane than in the illumination path, this has the advantage that the light in the illumination path remains coherent, which increases the sharpness of the image, especially when using MEMS as the image source.

[0011] According to the invention, the diffusers are moved relative to each other with a speed of less than 1 mm / s or with a frequency of less than 1 Hz. A combination of such relative motion and frequency is also within the scope of the invention. These configurations have the advantage that no particularly large or powerful drive is required to generate the relative motion. A comparatively small or weak drive is sufficient; no high accelerations are necessary. This saves energy and / or requires little installation space and / or generates no or only minimal vibrations that could adversely affect other components.

[0012] A vibration is generally considered to be a relatively rapid periodic motion. For optical systems, it is usually assumed in this context that frequencies above the threshold of perception are meant, i.e., values ​​well above 25 Hertz. However, the relative motion of the two axes proposed according to the invention is less than 1 Hertz. Preferably, it is about 0.1 Hertz or less. This is more accurately described as oscillation or slow fluctuation than as vibration.

[0013] Preferably, the projection surface has an image diagonal between 7.5 cm and 13 cm. The low speed of the relative movement of the two diffusers, as described in the invention, is particularly suitable for use with an image size of this order of magnitude.

[0014] Preferably, one of the two diffusers is statically arranged, and the other is a movable diffuser. This combination of a static and a movable component achieves speckle reduction in a cost-effective manner.

[0015] Preferably, the first diffuser is arranged to be movable in a first direction, and the second diffuser is arranged to be movable in a second direction, wherein the first and second directions are orthogonal to each other. Orthogonal directions are understood to mean both two directions that are perpendicular to each other at 90° and two directions that have at least one such perpendicular component, i.e., that are not parallel to each other. Advantageously, orthogonally arranged diffusers are operated with a time offset, so that at the reversal point of the movement of the first diffuser, the correspondingly orthogonally arranged second diffuser is in motion, thus ensuring continuous relative movement of the diffusers.

[0016] According to one embodiment, a motor comprising a shape memory alloy is provided as the drive motor for the relative movement of the diffusers. A shape memory alloy (also known as SMA or memory metal) is a special metal or alloy that can exist in two different crystal structures. The term shape memory alloy derives from the phenomenon that shape memory alloys can seemingly "remember" a previous shape despite subsequent significant deformation.

[0017] Shape memory alloys can transmit very high forces without noticeable fatigue over a very large number of motion cycles. Compared to other actuator materials, shape memory alloys have by far the highest specific energy output, i.e., the ratio of work done to material volume. Elements made of a shape memory alloy can function for several million cycles. However, the properties of shape memory elements deteriorate with an increasing number of cycles. The property of shape memory alloys, which is usually considered a disadvantage—namely, that they only allow relatively slow shape changes, which are also not particularly accurately reproducible—well meets the requirements for reducing speckle effects. Another advantage of a motor using a shape memory alloy is its small installation space requirement.

[0018] According to another embodiment, an eccentric is provided as the drive motor for the relative movement of the diffusers. An eccentric is advantageously suited to generating a desired slow relative movement. For example, a spring-loaded eccentric is provided. A further advantage of an eccentric drive is the small installation space required.

[0019] According to one embodiment, an element made of a shape-memory alloy is arranged in the edge region of a diffuser. Typically, the diffuser has an edge region on all its sides. In the case of a rectangular diffuser, there are therefore four sides. According to a first advantageous embodiment, the shape-memory alloy element is arranged only on one of these sides. According to a second advantageous embodiment, corresponding elements are arranged on opposite sides of the diffuser. According to a third advantageous embodiment, corresponding elements are arranged on mutually orthogonal sides of the diffuser. These elements thus serve, firstly, as a support or suspension for the diffuser. Secondly, they serve to drive it. In this way, different functions are advantageously realized in a single component.Advantageously, elements arranged orthogonally to each other are operated with a time offset, so that at the reversal point of the movement of a first element, a correspondingly orthogonal element to it is in motion, and in this way an uninterrupted relative movement of the diffusers is ensured.

[0020] According to another embodiment, a thin liquid layer in which particles are diffused serves as the diffuser, and the properties of the liquid layer and the particles are matched to induce Brownian motion in the particles. Brownian motion is an irregular and jerky thermal motion of small particles in liquids or gases. The proposed use of Brownian motion has the advantage that the diffuser is passively driven, requiring no separate drive motor or, for example, an electrical energy supply, but remaining in motion solely due to ambient heat. Thus, neither a separate drive nor a separate energy supply is necessary to reduce speckle effects.Such a passively driven diffuser is considered a movable diffuser within the scope of this invention, since it performs the movement suitable for speckle suppression by means of the movement of the diffused particles, which also fulfill a diffuser function.

[0021] Advantageously, a projection device according to the invention is used in a head-up display.

[0022] Further features of the present invention will become apparent from the following description and the attached claims in conjunction with the figures.

[0023] Figure overview

[0024] Fig. 1 schematically shows a head-up display for a means of transportation;

[0025] Fig. 2 schematically shows an embodiment of an imaging unit;

[0026] Fig. 3 shows an imaging unit according to the invention;

[0027] Fig. 4 shows an arrangement of two diffusers;

[0028] Fig. 5 shows a diffuser with shape memory drive;

[0029] Fig. 6 shows another diffuser with shape memory drive;

[0030] Fig. 7 shows a diffuser arrangement with Brownian motion; and

[0031] Fig. 8 schematically shows a means of transport in which a solution according to the invention is implemented. Figure description

[0032] 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.

[0033] Fig. 1 schematically shows a head-up display for a vehicle as an example of an image generation system 1. The head-up display comprises an imaging unit 2, an optical unit 3, and a mirror unit 4. A beam of light SB1 originates from a projection surface 21 and is reflected by a first mirror 31 onto a curved mirror 32, which reflects it towards the mirror unit 4. The mirror unit 4 is represented here as the windshield 41 of the vehicle. From there, the beam of light SB2 travels towards the eye 61 of a viewer.

[0034] The viewer sees a virtual image VB, which is located outside the vehicle, above the hood or even in front of the vehicle. Through the interaction of optical unit 3 and mirror unit 4, the virtual image VB is a magnified representation of the image coming from the projection surface 21. Here, a speed limit, the current vehicle speed, and navigation instructions are symbolically displayed. As long as the eye 61 is within the eyebox 62, indicated by a rectangle, all elements of the virtual image are visible to the eye 61. If the eye 61 is outside the eyebox 62, the virtual image VB is only partially visible or not visible at all. The larger the eyebox 62, the less restricted the viewer is in choosing their seating position.The curvature of the curved mirror 32 is adapted to the curvature of the windshield 41 and ensures that the image distortion is as stable as possible across the entire eyebox 62. The curved mirror 32 is rotatably mounted by means of a bearing 321. This rotation of the curved mirror 32 allows the eyebox 62 to be moved, thus adjusting its position to the position of the eye 61. The first mirror 31 ensures that the path traveled by the beam SB1 between the projection surface 21 and the curved mirror 32 is long, while simultaneously maintaining the compact size of the optical unit 3. The optical unit 3 is separated from its environment by a transparent cover 33. The optical elements of the optical unit 3 are thus protected, for example, from dust present in the interior of the vehicle.A glare shield 34 serves to reliably absorb light reflected across the interface of the cover 33, thus preventing glare for the viewer. In addition to sunlight SL, light from another ambient light source 64 can also reach the projection surface 21.

[0035] Fig. 2 schematically shows an embodiment of an imaging unit 2 with light sources 14R, 14G, 14B that emit coherent light. The figure shows a controllable mirror unit 73 in the imaging unit 2, which acts as a display element 11. The mirror unit 73 consists, for example, of a two-dimensional arrangement of micromirrors, each of which is positioned in one of two positions when controlled. A light beam LB incident on it is thus modulated in a pixel grid to generate the virtual image VB. This is a DMD. According to another embodiment, the controllable mirror unit 73 consists of a mirror adjustable about several axes, which is controlled such that an incident laser beam is reflected according to a two-dimensional grid, thereby generating the virtual image VB.

[0036] The light beam LB, which strikes the micromirrors of the mirror unit 73, or the laser beam, which falls on the mirror adjustable about several axes, originates from the light sources 14R, 14G, 14B. The light sources 14R, 14G, 14B are shown here as schematic boxes. They can be designed as conventional light sources, for example as light-emitting diodes (LEDs), or as laser light sources. The solution according to the invention is particularly useful when the light sources 14R, 14G, 14B emit coherent light in which speckles can occur, which are reduced by measures according to the invention.

[0037] Fig. 3 shows an imaging unit 2 according to the invention. The light sources 14R, 14G, 14B are designed as laser diodes. The light emitted by them is collimated, indicated here by lenses 151. By means of a mirror 161 or by means of two dichroics 162, 163, the light emitted by the three light sources is combined in a common direction of propagation. It passes through a lens, which here schematically represents an illumination optic 155. It is then deflected by means of the mirror unit 73 as an image transmitter 11 according to an image to be displayed. It then reaches a lens, which here schematically represents a projection optic 156. It then reaches a first diffuser 171 arranged in the projection surface 21 of the projection optic 156. A second diffuser 172 is arranged adjacent to this. After the second diffuser 172, the light continues as a beam SB1.In the illustrated embodiment, the second diffuser 172 is fixed, while the first diffuser 171 is movable by means of a schematically indicated drive 181. A linear movement BLIN1 of the first diffuser 171 is indicated in the illustration by a double arrow. The linear movement BLIN1 has a frequency of less than 1 Hz and a speed of movement of less than 1 mm / s.

[0038] Fig. 4 schematically shows an arrangement of the two diffusers 171 and 172 according to one embodiment in a perspective view. For clarity, the distances are sometimes exaggerated. The schematically depicted projection optics 156 are visible. The optical axis OA1 of the light coming from the projection optics is shown by a dashed line. The projection plane 21 of the projection optics 156 is also indicated by a dashed line. The first diffuser 171 is arranged in the projection plane 21. It is driven by a linear motor 181. The linear movement BLIN1 is indicated by a double arrow and runs parallel to or within the projection plane 21. The second diffuser 172 is arranged parallel to the projection plane 21 and to the first diffuser 171. It is driven by a linear motor 182.The linear movement BLIN2 is indicated by a double arrow and runs parallel to or in the projection plane 21, but perpendicular to the linear movement BLIN1 of the first diffuser 171. The direction R1 of the linear movement BLIN1 of the first diffuser 171 is thus perpendicular to the direction R2 of the linear movement BLIN2 of the second diffuser 171. The first direction R1 and the second direction R2 are therefore orthogonal to each other. For example, an eccentric 188 is provided as the drive 182, against which a diffuser 172 rests by means of a preload 189, for example a spring. The eccentric 188 rotates about its eccentrically arranged axis and thereby sets the diffuser 172 into a linear movement BLIN2.

[0039] Fig. 5 schematically shows a diffuser 171 with a shape memory drive. The diffuser 171 is connected at its left and right sides (i.e., in its edge region 173) to a stationary component 180 via a motor 183. The motor 183 schematically includes a spring 184, which consists of a bent wire held at both ends 186 in retaining elements 185 and rests against the diffuser 171 in its central region 187. The bent wire is made of a shape memory alloy and has two stable geometric shapes. The spring 184 on the left in the figure shows the bent wire in a first, curved shape. In this first shape, the central region 187 of the wire is bent away from the ends 186 of the wire to the right in the plane of the drawing. The two ends 186 of the wire are only partially located in the respective holding elements 185.The spring 184 shown on the right in the figure displays the bent wire in a flat second shape. In this second shape, the ends 186 of the wire protrude further into the respective retaining element 185 than in the first shape of the wire. By changing the temperature of the wire, by changing the current flowing through the wire, or by other suitable measures, the shape memory alloy is caused to switch between the two shapes. The two springs 184 arranged on the left and right are operated in opposite directions, so that the diffuser 171 performs a linear movement BLIN1 in the direction of R1. Fig. 6 schematically shows a diffuser 171 with a shape memory drive in a further embodiment. The diffuser 171 is connected to a stationary component 180 via a motor 183 on its upper side (as shown in the figure) and via a motor 183' on its right side.The motor 183, 183' schematically comprises a spring 184, 184' consisting of a bent wire, which is held at both ends 186, 186' in retaining elements 185, 185' and rests against the diffuser 171 in its central region 187, 187'. The bent wire is made of a shape-memory alloy which, as described in the previous figure, has two stable geometric forms. Both springs 184, 184' are shown in their bent, first form. They are preferably operated with a phase shift. In this case, the diffuser 171 does not perform a linear movement, but rather a two-dimensional movement composed of two linear movements BLIN1, BLIN2 with orthogonal directions R1, R2. Preferably, the two motors 183, 183' are operated at different frequencies.

[0040] Fig. 7 shows a schematic, sectional view of a diffuser arrangement 170, the movement of which is based on Brownian motion. The diffuser arrangement 170 has a liquid-tight wall 1701, which encloses a liquid 1702. Diffusers 1703, shown here as thin plates, are located in the liquid 1702. These plates move essentially in the plane of the diffuser arrangement 1701, i.e., mainly with motion components in the first direction R1 and the second direction R2, indicated by double arrows. The size, shape, and other properties of the plates are matched to the dimensions and properties of the wall 1701 enclosing the liquid 1702, as well as the fluidity and other properties of the liquid 1702. This achieves the desired slow movement of the diffusers 1703, preferably at a speed of up to 1 mm / s.

[0041] In other words, the invention relates to head-up displays, and in particular to the technical area concerning the speckle phenomenon. This phenomenon can occur in laser projections and is considered an undesirable optical effect that should be avoided. Generally, this phenomenon is described as a granular interference pattern that appears on an optically rough object surface when the illumination is sufficiently coherent. Speckles are often avoided or reduced by rapidly moving a diffuser translationally in the x, y, or z direction, or in two or three of these directions combined, or by tilting, shaking, or rotating it around an axis. The reduction of the speckle phenomenon can be enhanced by propagating the laser beam twice through the same moving diffuser in the illumination path.This, however, requires reflective elements and is subject to significant disadvantages in terms of installation space, as the individual optical elements require physically determined projection distances and mechanical suspensions. Furthermore, this cannot be transferred to an intermediate image plane, since most intermediate image planes are far too large to be rotated at high speeds or shaken at high frequencies without causing adverse effects such as loss of installation space or unpleasant noise generation. Previously known methods also suffer from the problem that they disrupt coherence in the illumination path, which leads to poorer laser focusability and thus to unacceptable imaging properties on the intermediate image plane within a MEMS laser scanning system.The invention is based on using two successive diffusers 171, 172 as an intermediate image plane, one of which is fixed and the other moving slowly. The scattering properties of the diffusers 171, 172 and their distance from each other are selected such that a sharp image impression remains, ideally as small as mechanically possible. The advantage of this setup is that the movement can be so extremely slow (even <1 Hz) that no disturbing noise is generated. This setup can also be implemented quite compactly, e.g., using an eccentric attachment with a DC motor. There are also hardly any requirements regarding the accuracy of the movement.Contrary to general expectations, the inventors have discovered that the coherence of the laser can be disrupted by diffuse scattering at a first diffuser and subsequently by minute relative movements at a second diffuse surface to such an extent that no visually perceptible granular interference patterns (speckles) remain, or at least their contrast is below the perception threshold. The preferred implementation involves despeckling in the projection path: two diffuse planes serve as an intermediate image plane, in which either the front or the rear plane moves while the other remains static. Such an arrangement is ideal in combination with a laser scanning system. Another implementation involves despeckling in the illumination path: it is also possible to use this setup in the illumination path. There, too, it can be used in a space-saving manner, especially when a linear setup without 180° reflection is desired.The preferred implementation of despeckling in the projection path is particularly interesting for laser-scanning-based systems (via MEMS). The image is generated in the projection surface 21 (an intermediate image plane / image screen) and despecked there directly by the relative movement of the diffusers 171 and 172. It should be noted that extremely small relative movements are implemented according to the invention. The image size on the projection surface 21 is in the range of 3" to 5", thus having a diagonal of 7.5 cm to almost 13 cm. The low speed of the relative movement of the two diffusers 171 and 172, as described in the invention, is particularly suitable for interacting with an image size of this order of magnitude. A unique feature of the invention is that an extremely slow frequency is used for despeckling, which is more accurately described as a slow oscillation or fluctuation.

[0042] Fig. 8 schematically shows a means of transport 100 in which a solution according to the invention is implemented. In this example, the means of transport 100 is a motor vehicle. The image generation system 1 is a head-up display. Data about the vehicle's surroundings can be acquired using sensors 101. The sensors 101 can, in particular, include sensors for environmental detection, e.g., ultrasonic sensors, laser scanners, radar sensors, lidar sensors, or cameras. The information acquired by the sensors 101 can be used to generate content to be displayed for the image generation system 1. Further components of the motor vehicle in this example are a navigation system 102, which can provide position information, and a data transmission unit 103. The data transmission unit 103 can, for example,A connection to a backend is established, for example, to obtain updated software for vehicle components. A memory 104 is available for data storage. Data exchange between the various vehicle components takes place via a network 105.

[0043] Reference symbol list

[0044] 1 Image generation system

[0045] 11 image transmitters

[0046] 14R,14G,14B Light source

[0047] 151 lens

[0048] 155 Lighting optics

[0049] 156 Projection optics

[0050] 161 mirrors

[0051] 162 Dichroic

[0052] 163 Dichroic

[0053] 170 Diffuser arrangement

[0054] 1701 Wall

[0055] 1702 Liquid

[0056] 1703 Diffuser

[0057] 171 Diffuser, first

[0058] 172 Diffuser, second

[0059] 173,173' Edge area

[0060] 180 component, fixed

[0061] 181 Drive

[0062] 182 Drive

[0063] 183,183' Motor (with shape memory alloy)

[0064] 184,184' spring

[0065] 185,185' Holding element

[0066] 186, 186' End (wire end)

[0067] 187,187' Midrange

[0068] 188 eccentrics

[0069] 189 lead

[0070] 2 Imaging Unit

[0071] 21 projection surface

[0072] 3 Optical unit 31 First mirror

[0073] 32 Curved Mirror

[0074] 321 Storage

[0075] 33 Cover

[0076] 34 Glare protection

[0077] 4 mirror unit

[0078] 41 Windscreen

[0079] 61 Eye

[0080] 62 Eyebox

[0081] 64 Source of interference

[0082] 73 Mirror unit

[0083] 100 means of transport

[0084] 101 Sensors

[0085] 102 Navigation system

[0086] 103 Data transmission unit

[0087] 104 storage

[0088] 105 Network

[0089] BLINi Linear Motion

[0090] LB light beam

[0091] LS laser beam

[0092] OA1 Optical Axis

[0093] R1,R2 direction

[0094] SB1 beam bundle

[0095] SB2 beam bundle

[0096] SL Sunlight

[0097] VB Virtual Image

Claims

Patent claims 1. Projection device comprising a coherent light source (14R, 14G, 14B), a first diffuser (171, 1703) and a second diffuser (172) arranged to be movable relative to each other, an illumination optic (155), an image transmitter (11) and a projection optic (156), further comprising a projection surface (21), wherein the first diffuser (171, 1703) is arranged in the projection surface (21), and the second diffuser (172) is arranged in the beam path adjacent to the first diffuser (171, 1703), characterized in that the diffusers (171, 172, 1703) are moved relative to each other with a relative movement (BLIN1, BLIN2) of less than 1 mm / s and / or with a frequency of less than 1 Hz.

2. Projection device according to claim 1, wherein the projection surface (21) has an image diagonal between 7.5cm and 13cm.

3. Projection device according to one of claims 1 to 2, wherein one of the two diffusers (172,171) is statically arranged and the correspondingly other diffuser (171,172) is a movable diffuser.

4. Projection device according to one of claims 1 to 2, wherein the first diffuser (171 ) is arranged to be movable in a first direction (R1 ) and the second diffuser (172) is arranged to be movable in a second direction (R2), wherein the first direction (R1) and the second direction (R2) are orthogonal to each other.

5. Projection device according to one of claims 1 to 4, wherein a motor (183,183') comprising a shape memory alloy is provided as the drive motor for the relative movement (BLIN1 , BLIN2) of the diffusers (171 ,172).

6. Projection device according to one of claims 1 to 4, wherein an eccentric (186) is provided as a drive motor for the relative movement (BLIN1 , BLIN2) of the diffusers (171 ,172).

7. Projection device according to claim 5, wherein an element (184, 184') made of a shape memory alloy is arranged in the edge region (173, 173') of a diffuser (171).

8. Projection device according to any one of claims 1 to 4, wherein a A diffuser arrangement is provided which has a thin liquid layer in which particles acting as diffusers (1703) are diffused, and the properties of the liquid (1702) and the particles are matched to set the particles and thus the diffusers (1703) into Brownian motion.

9. Head-Up Display comprising a projection device according to one of the preceding claims.

Images