DE102018130148A1 - Head-Up Display - Google Patents

Abstract

The present invention relates to a head-up display (10), in particular for a motor vehicle, comprising an imaging unit (12) for generating at least one image, wherein the imaging unit (12) can emit light radiation for generating the at least one image, and wherein the head-up display (10) furthermore has an optical unit with at least one mirror (16, 18) for reflecting the light radiation and for guiding the light radiation onto an imaging surface, characterized in that at least one mirror (18) is designed as an optical phased array , which has a plurality of separately adjustable mirror elements (30), the mirror elements (30) being at least partially movable longitudinally to reduce speckle patterns.

Description

The present invention relates to a head-up display, in particular for a motor vehicle. The present invention relates in particular to a head-up display which enables a reduction in speckle patterns. The present invention further relates to the use of an optical phased array for reducing speckle patterns in a head-up display.

Head-up displays, particularly for motor vehicles, are well known in the art. Head-up displays have an imaging unit that projects an image, for example, to a combiner and thus to a type of screen. Alternatively, there are variants of head-up displays in which the image from the imaging unit is projected onto the windshield of the motor vehicle. The driver of the motor vehicle, for example, can therefore see the projected image when looking at the combiner or the windshield.

When designing head-up displays, it is particularly important to generate an image which can be easily and comfortably perceived by the driver of a vehicle which is equipped with a head-up display.

In head-up displays, so-called speckles or speckle patterns can occur due to the illumination of optically rough projection surfaces, in particular in the case of unevenness in the order of magnitude of the wavelength of the radiation forming the image.

US 2017/0293156 A1 describes devices and methods that use a first fixed figure element, a polarizing beam splitter and a second fixed figure element to reduce speckle patterns in projected images. In particular, laser light is generated and divided into two parts with orthogonal polarizations. The first part of the laser light is internally reflected on at least three inner surfaces of the second solid figure element and then spatially recombined with the second part of the laser light in the first solid figure element. The difference in path length that the two sections follow creates a temporal incoherence in the recombined laser light beam, and this temporal incoherence also reduces as spots in the projected image.

US 2017/0293155 A1 describes devices and methods that use birefringent elements to reduce speckle patterns. The birefringent elements are angular and separate received laser light into two separate light beams and then recombine the two angularly separate light beams. At least one scan mirror is configured to reflect the recombined laser light beam, and a driver circuit is configured to provide an excitation signal to excite the movement of the at least one scan mirror. The angular separation of the light beams creates a relative delay between the two light beams, and this relative delay between the light beams creates a temporal incoherence in the recombined light beams. This temporal incoherence can reduce speckle patterns in the projected image.

US 2017/0199382 A1 describes a HUD device installed on a vehicle and displaying an image as a virtual image in a visible area in a manner visually recognizable to an occupant by projecting the image onto a windshield. The HUD device includes an oscillator that oscillates a laser light flux, a screen, a part that has an unevenness in a projection area in which the image is generated by projecting the laser light flux, an optical projection system that projects the laser light flux onto the screen element, an optical magnification system that enlarges the image onto which the windshield projects and directs light of the image into the visible area; and a controller that causes a focal length of the projection optical system to oscillate in time. Accordingly, an appropriate visible area is ensured, luminescence inconsistencies in an image that is visually recognized are suppressed, and it becomes easy to save space.

Such solutions known from the prior art can offer further potential for improvement, in particular with regard to providing a high-quality image in a head-up display.

It is the object of the present invention to at least partially overcome the disadvantages known from the prior art. It is in particular the object of the present invention to provide a solution which enables high-quality imaging of a head-up display in a simple and reliable manner. It is a particularly preferred object of the present invention to prevent or at least significantly reduce the occurrence of speckle patterns in a head-up display.

According to the invention, the problem is solved by a head-up display with the features of claim 1. The problem is also solved according to the invention by an arrangement with the features of claim 6 and by a method with the features of claim 9. Preferred embodiments of the Invention are in the Subclaims, described in the description or the figures, wherein further features described or shown in the subclaims or in the description or the figures, individually or in any combination, can constitute an object of the invention if the context does not clearly indicate the opposite.

It is proposed a head-up display, in particular for a motor vehicle, comprising an imaging unit for generating at least one image, light radiation for generating the at least one image being emittable by the imaging unit, and the head-up display also having an optical unit has at least one mirror for reflecting the light radiation and for guiding the light radiation onto an imaging surface, at least one mirror being designed as an optical phased array which has a multiplicity of mirror elements which can be adjusted separately and in particular independently of one another, the mirror elements for reducing speckle patterns are longitudinally movable.

Such a head-up display, in particular by the provision of an optical phased array (English: optical phased array), allows an effective reduction of the occurrence of speckle patterns and thereby high-quality imaging of image content or image content.

The head-up display is arranged, for example, in a vehicle, such as in a motor vehicle. In this case, an optical unit configured as a mirror unit can be arranged, for example, into which radiation is emitted by an imaging unit or imaging unit, such as a backlit LCD display, or a laser light source. The housing can be arranged approximately in the dashboard of the motor vehicle. The radiation can represent an image when projecting onto an imaging surface. For example, it is known for head-up displays that information from driver assistance systems or a multimedia unit, such as information from a navigation system, for example directions of travel or speed, or also information from a radio, or also other selectable information or specifications as images, that is to say graphical representations or texts. The optical unit, which has at least one mirror and, for example, more than one mirror and can therefore be referred to as a mirror unit, serves in particular to reflect the rays emitted by the imaging unit and thus to guide them in a defined manner to a projection surface or imaging surface. In addition, the mirror unit can serve to enlarge an image and thus serve as a magnifying mirror or otherwise influence the radiation. For example, an imaging screen, also referred to as a combiner, or a windscreen slide of a motor vehicle can serve as the projection surface.

The position of the head-up display is usually in front of the observer, in particular in front of the driver of the motor vehicle, in a passenger compartment of the motor vehicle. A space can be provided in the area of the dashboard, in particular in the area of a combination scoop, in which the head-up display can be mounted and protected from dirt particles by means of a cover, which is preferably transparent.

The imaging unit can have a radiation source, for example. The radiation source can emit radiation in a manner known per se, which forms an image. In other words, the imaging unit can emit light radiation for generating the at least one image based on a desired image content. In a non-limiting manner, the imaging unit or the radiation source can comprise one or a plurality of LED radiation sources or one or a plurality of laser light sources.

The information projected onto the display element or onto the imaging surface, for example the windshield, can be overlaid in a manner known per se with information shining through the imaging surface from an environment located behind the imaging surface, as a result of which a virtual image or a virtual display can be provided . In order to enable the driver to have a good view of the virtual image depending on the seating position or size, an eye box, which is also called an “eyebox”, can be tracked in the vehicle. The eyebox is the area or field of vision in which the user's eye point lies, i.e. the area in which the user can see the information displayed. The deflection of the output light by the projection device serves to track the eyebox and can be realized by means of an adjustment device, for example on the described or another mirror unit of an optical device.

As indicated above, there are also versions of head-up displays in which the virtual image is not projected onto the windshield, but is projected with an additional mirror, the so-called combination mirror, of the head-up display towards the observer, and thus in particular correct setting of the Combination mirror is projected on the face or in the eyebox.

In the head-up display described here, it is further provided that at least one mirror and thus at least one mirror of the optical unit or the mirror unit is designed as an optical phased array. The optical phased array is designed in such a way that it has a multiplicity of separately adjustable mirror elements, the mirror elements being at least partially longitudinally movable to reduce speckle patterns.

This configuration in particular can allow significant advantages over the solutions from the prior art.

An optical phased array is to be understood in particular to mean a grating structure which can emit a signal in the form of a wave. These waves overlap in a constructive and disturbing manner, which amplifies the signal in one direction and prevents it in other places. In this way, such an array can emit a strictly focused signal, which can be directed in different directions by stepping the timing of the transmissions that occur at different locations along the array. Phased arrays are known per se in other areas. For example, the optical phased array can be configured as described in Byung-Wook Yoo et al., Optical phased array using high contrast gratings for two dimensional beamforming and beamsteering, Optics Express, Vol. 21, No. 10, page 12238.

Through the use of an optical phased array, the image or the light that falls on the imaging unit, for example using other mirrors arranged between them, can be directed into desired areas or positions or reflected here. This can be done, for example, by the light falling on one or a plurality of movable mirrors of the mirror or of the optical phased array and being reflected by them under a phase modulation. Control of the direction of propagation of the light and thus of the image can be realized or improved by moving the mirror to a substrate, as described in detail below.

The advantage of using an optical phased array can be seen in the fact that a very rapid change in the direction of propagation of the light is possible. In other words, it can be made possible to drive a first region of an imaging surface and a second region of an imaging surface at a very high frequency. As a result, the image generated in each case can have a very high quality. In particular, this can allow speckle patterns to be prevented or at least significantly reduced.

This can be particularly advantageous in a head-up display, as described below.

Bumps on the illuminated surface or the imaging surface, for example the windshield, can be regarded as scattering centers from which spherical waves of different phases emanate which interfere in the far field. This creates a spatial structure with randomly distributed intensity maxima and intensity minima. The three-dimensional interference phenomena are longitudinal and transverse speckle, which depend on the respective longitudinal and transverse coherence. Transversal speckles have greater significance at a greater distance because the individual spherical wave components can always be simplified more than flat waves. The speckle contrast can therefore be used as a measure of coherence.

When viewing speckle on a coherently irradiated surface with the naked eye, the user, such as the driver of a vehicle, perceives a moving pattern when viewing the image of the head-up display. This is caused by the different interference on the retina when the eye moves. The direction of movement depends on the position of the focal plane in relation to the retina. The eyes of short-sighted and far-sighted persons who are not accommodated perceive different directions of movement.

Such patterns can be very disruptive when displaying image content, for example on the windshield, using a head-up display of a vehicle.

The head-up display described here now makes it possible, in particular by providing the optical phased array, to prevent or at least reduce such patterns or phenomena referred to as speckle patterns.

By providing the optical phased array in the optical unit or in the mirror unit, the laser beams can be controlled or deflected such that the occurrence of speckle patterns can be effectively counteracted. This is because the corresponding mirror elements can be used to reduce or eliminate the speckle pattern are preferably moved at a fast speed so that the laser point is essentially never at the same location or is always in motion. This can make it possible for the speckle patterns to be reduced or disintegrate. In other words, the laser beam can be prevented from being constantly in one position with respect to the imaging surface, but the laser beam or the laser beams can always be in motion, thereby reducing the occurrence of the speckle patterns as described above.

The precise movement or the exact settings of the respective mirror elements can dependably depend on the design of the surface of the respective imaging surface and on the radiation source used. However, the exact settings can easily be determined by calibrating the system, it being possible, for example, for human or computer-based individual images to be examined for the occurrence of speckle patterns with different settings or movements of the mirror elements, so that optimal settings can be found by calibration.

For example, but in no way limited to this, it can be provided that, in addition to the basic settings of the optical phased array, a longitudinal stroke or a signal is also modulated onto the control signal, which determines the basic position of the laser beams on the imaging surface. Examples include a sinusoidal stroke, a rectangular stroke or a sawtooth stroke.

The head-up display described here can thus effectively reduce speckle patterns in a simple manner. This allows a particularly high-quality display of the image or images, which is of great advantage for readability.

In addition, viewing the image can be more comfortable for the human eye and also counteract fatigue.

By using an optical phased array, speckle patterns can be reduced particularly effectively, since the laser beams can be deflected very precisely. In addition, the use of the optical phased array is very customizable, so that the head-up display can be used regardless of the surface of the imaging area, such as a windshield or a combiner. This enables problem-free implementation in existing systems.

It may be particularly preferred for the optical phased array to have a plurality of mirror elements which, at least partially, are fixed to a carrier so as to be movable longitudinally and at least partially apart. In this configuration, the direction of propagation of the reflected light can be controlled in a particularly preferred manner. This is because a movable arrangement of the mirror elements on the carrier can make it possible for a movement of the mirror element to change its orientation relative to the carrier and in particular relative to the display surface and relative to the imaging unit, such as the laser. This accordingly enables the direction of reflection of the light beams to be adjusted, as a result of which the position of the projection can be adjusted. This allows the occurrence of speckle patterns to be reduced in a precise and particularly effective manner.

This is surprisingly also achieved in that the mirror elements can be moved at least partially longitudinally. It has been shown that in particular such a movement of the mirror elements can effectively reduce or prevent speckle patterns.

An at least partially longitudinal movement of the mirror elements can be understood to mean that the mirror elements can be moved at any position or at individual positions in a direction which is transverse to the plane of the mirror surface.

For example, in this regard it may be possible for the plurality of mirror elements to have a flat mirror surface and to be fixed to a support so that they can be moved longitudinally and separately from one another in such a way that the mirror elements are movable perpendicularly or tilted relative to the mirror surface.

It can be particularly preferred that the mirror elements can be moved by a MEMS actuator. A MEMS actuator is to be understood in a manner known per se to be such an actuator or such an actuating unit which is based on or has a micro-electro-mechanical system (MEMS). Such an actuator is of great advantage in particular for the application described here, since these can usually be designed with a very small mass due to their small size, so that the mirrors can be moved in a simple manner at a high frequency. This in turn allows the occurrence of speckle patterns to be reduced in an exact and particularly effective manner.

Furthermore, it can be preferred that the imaging unit comprises at least one laser light source. In particular, a laser light source as an imaging unit and thus for generating at least one image can be particularly advantageous for the head-up display described here. Because a laser can be used to produce high quality images, which can improve the visual impression of the user. In addition, laser light can be aligned very precisely, which can lead to a very precise deflection or reflection or can further improve it when it hits the optical phased array, so that the reflected light is also used in a very defined manner for a projection of the image or images can be. This in turn can lead to the creation of a very high quality and high contrast image. Furthermore, it can be made possible that the position of the projection is particularly defined, so that the occurrence of speckle patterns can be prevented or reduced very reliably.

Finally, it has been shown that in addition to the brilliance, speckle is perceived as a typical laser property. As a result, the head-up display described here can be particularly advantageous in combination with a laser light source.

For example, a so-called RGB laser can be used as the laser. An RGB laser can in particular be understood to mean such a laser which is designed to emit light with different colors, in particular the colors red, green and blue and corresponding mixed colors. This also enables images to be generated which have a colored design. This in turn can produce a particularly high quality image.

With regard to further advantages and features of the head-up display, reference is made to the description of the arrangement, the method, the figures and the description of the figures, and vice versa.

The present invention furthermore relates to an arrangement of a head-up display and an imaging surface, the head-up display being designed and arranged in such a way that it directs light radiation for generating at least one image onto the imaging surface, characterized in that Head-up display is designed as described above.

With regard to the head-up display, reference is therefore made to the above statements.

As also indicated above, it is provided that the head-up display is configured and arranged in such a way that light radiation for generating at least one image is directed onto the imaging surface. In other words, the head-up display can be positioned such that, in particular by adjusting the mirrors of the optical unit or the mirror unit, the light beams emitted by the imaging unit are directed onto the imaging surface or are projected thereon, in order for the driver of the vehicle to make at least one picture visible. Basically, a picture is to be understood here to mean all the contents of the illustration, regardless of whether it is a graphic representation, writing or the like.

The advantages of such a head-up display can be seen in summary, in particular, in a high-quality image, in particular the occurrence of speckle patterns can be reduced.

It can be provided that the imaging surface is part of a windshield, in particular of the motor vehicle, or part of an imaging element, in particular a so-called combiner, that is separate from the windshield. Such applications are known for head-up displays and therefore offer a simple implementation of the present invention in existing systems or peripherals.

In addition, it can be made possible in particular in the case of such imaging surfaces that the information projected onto the display element or onto the imaging surface can be overlaid in a manner known per se with information which shines through the imaging surface from an environment located behind the imaging surface, as a result of which a virtual image or A virtual display can be provided which enables a particularly large number of options with regard to the representability, in particular in combination with the environment in front of the vehicle.

With regard to the imaging surface or projection surface described above, it can further be provided that it has a projection structure or imaging structure. This configuration enables the image or the image content to be projected in a particularly advantageous manner. This configuration can be advantageous because the imaging light radiation may fall onto the display surface at an unfavorable angle of incidence. The projection structure or imaging structure can be designed as a coating, for example. Examples of coatings include, for example, holographic elements, such as holographic foils, which can be easily implemented by the person skilled in the art can be configured in such a way that the radiation falling on the display surface can be imaged as desired in order to display it to the user in the best possible way.

Alternatively, it can be advantageous if the coating comprises nanoscale silver particles. For example, the coating can have a transparent plastic in which nanoscale particles, such as silver particles, are embedded. Such coatings are characterized in particular by the fact that they enable a sharp, luminous projection and nevertheless a clear view. Furthermore, in particular light that falls onto the display surface at oblique angles can be projected easily and with high contrast.

Basically, nanoparticles can be those particles that have a size in a range from 1 nm to 1000 nm. The size of the nanoparticles can be chosen depending on the wavelength of the incident light. It was found that, for example, particles with a size of 62 nanometers, for example in a transparent polymer, such as polyvinyl alcohol, which is basically suitable as a matrix as well as other transparent polymers, enable a coating that selectively emits light with a wavelength of 458 Can reflect nanometers, which corresponds to blue light. If the imaging unit now directs appropriate light onto the display element or the projection coating, the corresponding image can be clearly visible on the display element, even from oblique viewing angles. Of course, a mixture of particles of different sizes, in particular in the nanometer range and / or different materials, can also be provided.

Layer thicknesses of the respective coating can be in a range of less than 1 millimeter, for example 0.5 mm.

In addition to coatings, however, the imaging structure can also have an embedding, for example in the windshield or the imaging element separate therefrom, so that the structure is formed, for example, by the imaging surface itself or a corresponding layer is embedded in the display element.

With regard to further advantages and features of the arrangement, reference is made to the description of the head-up display, the method, the figures and the description of the figures, and vice versa.

1. a) Bereitstellen eines Head-Up-Displays, wie dies vorstehend beschrieben ist,
2. b) Emittieren von Lichtstrahlung zum Erzeugen des wenigstens einen Bildes auf wenigstens ein optisches Phased Array als Spiegel; und
3. c) Einstellen des wenigstens einen optischen Phased Arrays derart, dass die Lichtstrahlung auf die Abbildungsoberfläche geleitet wird; wobei
4. d) eine Mehrzahl von Spiegelelementen des optische Phased Array zur Reduzierung von Speckle-Mustern zumindest teilweise longitudinal bewegt werden.

The present invention furthermore relates to a method for displaying at least one image on an imaging surface using a head-up display, the method comprising the following method steps:

1. a) providing a head-up display as described above,
2. b) emitting light radiation to generate the at least one image on at least one optical phased array as a mirror; and
3. c) adjusting the at least one optical phased array in such a way that the light radiation is directed onto the imaging surface; in which
4. d) a plurality of mirror elements of the optical phased array are moved at least partially longitudinally to reduce speckle patterns.

Such a method is used, in particular, to use a head-up display, as described above, to image or project onto an imaging surface. In this regard, method steps a) to c) can be carried out using a head-up display as described above in a manner known per se, for example using a laser light source as the light source. The light rays are generated according to the desired image or image content and directed into an optical unit with mirrors. The radiation can be directed or reflected by the mirror to the imaging surface.

It is further provided that in the optical phased array provided, the mirror elements for reducing speckle patterns are at least partially moved longitudinally. This can be made possible at a high frequency, for example by means of a MEMS actuator. A MEMS actuator is to be understood in a manner known per se to be such an actuator or such an actuating unit which is based on or has a micro-electro-mechanical system (MEMS). Such an actuator is of great advantage in particular for the application described here, since these can usually be designed with a very small mass due to their small size, so that the mirrors can be moved in a simple manner at a high frequency. This in turn allows the occurrence of speckle patterns to be reduced in an exact and particularly effective manner.

By providing the optical phased array in the optical unit or in the mirror unit, the laser beams can be controlled or deflected such that the occurrence of speckle patterns can be effectively counteracted. Because for In order to reduce or eliminate the speckle pattern, the corresponding mirror elements can preferably be moved at a rapid speed in such a way that the laser point is essentially never at the same location or is always in motion. This can make it possible for speckle patterns to be reduced or disintegrate. In other words, the laser beam can be prevented from being constantly in one position with respect to the imaging surface, but the laser beam or the laser beams can always be in motion, thereby reducing the occurrence of the speckle pattern.

The exact movement or the exact settings of the respective mirror elements can depend on the design of the surface of the respective imaging surface and on the radiation source used. However, the exact settings can easily be determined by calibrating the system, it being possible, for example, to examine human or computer-based individual images with regard to the occurrence of speckle patterns with different settings or movements of the mirror elements, so that optimal settings can be found.

It can therefore be advantageous that method step d) is based on a calibration step in which the reduction of speckle patterns with different movements of the mirror elements is examined for an image or for an image content.

With regard to further advantages and features of the method, reference is made to the description of the head-up display, the arrangement, the figures and the description of the figures, and vice versa.

• 1 eine schematische Darstellung zeigend eine Ausgestaltung eines Head-Up Displays gemäß der Erfindung;
• 2 eine schematische Darstellung zeigend einen Spiegel für ein Head-Up Display gemäß 1;
• 3 eine schematische Darstellung zeigend eine Detailansicht des Spiegels aus 2;
• 4 den Spiegel aus 2 in einer ersten Konfiguration;
• 5 den Spiegel aus 2 in einer zweiten Konfiguration; und
• 6 den Spiegel aus 2 in einer dritten Konfiguration.

Further advantages and advantageous configurations of the objects according to the invention are illustrated by the drawings and explained in the following description. It should be noted that the drawings are only descriptive and are not intended to limit the invention in any way. Show it:

• 1 a schematic representation showing an embodiment of a head-up display according to the invention;
• 2nd a schematic representation showing a mirror for a head-up display according to 1 ;
• 3rd a schematic representation showing a detailed view of the mirror 2nd ;
• 4th the mirror 2nd in a first configuration;
• 5 the mirror 2nd in a second configuration; and
• 6 the mirror 2nd in a third configuration.

1 shows a schematic representation showing an embodiment of a head-up display 10th according to the present invention.

Such a head-up display 10th is used in particular in a motor vehicle, such as a passenger car. The head-up display 10th be arranged approximately in the dashboard of the motor vehicle. The head-up display 10th includes an imaging unit 12 for emitting light rays for generating an image. The light rays are thus formed and emitted in such a way that a desired image can be projected onto an imaging surface or projection surface. For example, it is for head-up displays 10th known that information from driver assistance systems or a multimedia unit can be displayed. For example, information from a navigation system, for example directions of travel or speed, or information from a radio, or other images, that is to say graphic representations or texts, can be mentioned here.

For example, an imaging screen, also referred to as a combiner, can serve as the projection surface or imaging surface, in which case the imaging surface can be part of the head-up display 10. In the embodiment shown, however, the image can be projected onto the windshield of the motor vehicle, in which case the image surface is not part of the head-up display 10th is.

The imaging unit 12 can in one housing 14 be arranged or the radiation for projecting an image along a beam path into the housing 14 radiate. In the case 14 can also use mirrors 16 , 18th be provided, which can transmit or reflect the radiation. The mirror 16 , 18th can be used, for example, when the imaging unit 12 the radiation cannot send directly to the imaging surface, for example due to geometric conditions. Furthermore, the mirror 16 , 18th in the case of a reflection, increase the radiation or influence it in some other way in order to enable high-quality imaging.

The mirror 16 , 18th are thus in the optical beam path of the imaging unit 12 arranged or are part of the same, so that the imaging unit 12 emitted radiation on the mirrors 16 , 18th meets and is reflected or forwarded from there. As an imaging unit 12 a backlit display, such as a TFT display or LCD display, can be used in a manner known per se. The imaging unit can be particularly preferred 12 have one or more laser light sources. In particular, the beam path runs from the mirror 18th to an imaging surface or projection surface, as already described above.

The mirror 18th is described in detail in the following figures, identical or comparable components being provided with the same reference symbols.

In the 2nd is the mirror 18th shown, which is designed as an optical phased array.

Under an optical phased array there is in particular a grating structure 22 to understand the waveform emit signal. These waves overlap each other in a constructive and disturbing manner, which amplifies the signal in one direction and prevents it in other places. In this way, such an array can emit a strictly focused signal, which can be directed in different directions by stepping the timing of the transmissions that occur at different locations along the array. This is through the arrows 24th , 26 , 28 realized, the arrow 24th that on the lattice structure 22 incident and from the imaging unit 12 or the mirror 16 to represent coming light, and being the arrow 24th to represent the light reflected on a first area and the arrow 26 to represent the light reflected on a second area. It should be mentioned here that the first area and the second area do not necessarily have to be at a large distance from one another, but rather can be very close to one another

It may further be preferred that the optical phased array or the mirror 18th a plurality of mirror elements 30th has that is movable on a carrier 32 are fixed. In this configuration, the direction of propagation of the reflected light can be controlled in a particularly preferred manner. Because by a movable arrangement of the mirror elements 30th on the carrier 32 can be made possible by movement of the mirror element 30th its orientation relative to the carrier 32 and particularly relative to the imaging surface and relative to the imaging unit 12 , such as a laser. This enables the direction of reflection of the light beams to be adjusted accordingly, as a result of which the position of the projection or image can be adjusted. In this way, a reduction of speckle patterns can be achieved in an exact and effective manner, which enables high-quality imaging.

It is in the 2nd also the lattice structure 22 indicated. This can be designed such that a uniform height of the lattice structure 22 , for example in an exemplary range of less than 20 nm. A minimal initial phase difference of the reflected light can be achieved.

It may be preferred that the mirror elements 30th are movable by a MEMS actuator. This is in the 3rd shown where in detail spring elements 34 are shown, which are the mirror elements 30th on the carrier 32 fix. There is for each side or corner of the respective mirror element 30th one spring element each 34 intended. By controlling the spring elements 32 can the mirror element 30th be selectively tilted to either side. This allows control of the direction of reflection of the light and thus the reduction of the speckle pattern to be controlled particularly effectively and reliably.

The advantage of movable mirror elements 30th by means of a MEMS actuator, in particular in the case of a phased array, it can also be seen that these can usually be designed with a very small mass due to their small size, so that the mirror elements 30th can be easily moved at a high frequency. This in turn allows the speckle patterns to be reduced or erased in a very effective and reliable manner.

In the 4th to 6 are exemplary alignments of the mirror elements 30th shown by a control of the respective spring elements 34 is achievable.

It shows 4th an embodiment in which the mirror elements 30th are tilted longitudinally aligned and essentially two areas are formed. 5 shows an embodiment in which the mirror elements 30th are also tilted longitudinally aligned and a larger number of contiguous areas is formed and 6 shows an embodiment in which the mirror elements 30th are also tilted longitudinally aligned and a larger number of contiguous areas is formed. By appropriate alignment of the mirror elements 30th and at best a movement, for example through a MEMS actuator, for example, but not limited to this, from the position shown to a non-tilted position, for example, speckle patterns visible to an observer in an image of the head-up display 10th be reduced effectively.

The embodiments shown are only intended to be explanatory and in no way limit the invention.

The exact movement or the exact settings of the respective mirror elements 30th can dependably depend on the design of the imaging surface and the radiation source used. However, the exact settings can easily be determined by calibrating the system, with individual or human-based individual images, for example, with regard to the occurrence of speckle patterns with different settings or movements of the mirror elements 30th can be examined so that optimal settings can be found by calibration.

For example, but in no way limited to this, it can be provided that, in addition to the basic settings of the optical phased array, a longitudinal stroke or a signal is also modulated onto the control signal, which determines the basic position of the laser beams on the imaging surface. Examples include a sinusoidal stroke, a rectangular stroke or a sawtooth stroke. Such strokes can be formed, for example, by the orientation and height of the respective mirror elements 30th to each other or through the areas formed thereby, as is shown in the 4th to 6 shown and described above.

Reference symbol list

10th

Head-Up Display

12

Imaging unit

14

casing

16

mirror

18th

mirror

22

Lattice structure

24th

arrow

26

arrow

28

arrow

30th

Mirror element

32

carrier

34

Spring element

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 2017/0293156 A1 [0005]
• US 2017/0293155 A1 [0006]
• US 2017/0199382 A1 [0007]

Claims (10)

Head-up display, in particular for a motor vehicle, comprising an imaging unit (12) for generating at least one image, light radiation for generating the at least one image being emittable by the imaging unit (12), and wherein the head-up display (10) furthermore has an optical unit with at least one mirror (16, 18) for reflecting the light radiation and for guiding the light radiation onto an imaging surface, characterized in that at least one mirror (18) is designed as an optical phased array which has a multiplicity of separately adjustable ones Has mirror elements (30), wherein the mirror elements (30) are at least partially longitudinally movable to reduce speckle patterns. Head-up display after Claim 1 , characterized in that the optical phased array has a plurality of mirror elements (30) which, at least partially, are fixed to a carrier (32) so as to be movable longitudinally and at least partially. Head-up display after Claim 2 , characterized in that the plurality of mirror elements (30) have a flat mirror surface and are fixed separately from one another in a longitudinally movable manner on a support (32) in such a way that the mirror elements (30) are movable perpendicularly or tilted relative to the mirror surface. Head-up display according to one of the Claims 1 to 3rd , characterized in that the mirror elements (30) can be moved by a MEMS actuator. Head-up display according to one of the Claims 1 to 4th , characterized in that the imaging unit (12) comprises at least one laser light source. Arrangement of a head-up display (10) and an imaging surface, the head-up display (10) being designed and arranged to direct light radiation for generating at least one image onto the imaging surface, characterized in that the head -Up display (10) is designed according to one of the Claims 1 to 5 . Order after Claim 6 , characterized in that the imaging surface is part of a windshield or part of an imaging element separate from the windshield. Arrangement according to one of the Claims 6 or 7 , characterized in that the imaging surface has an imaging structure. Method for displaying at least one image on an imaging surface using a head-up display (10), the method comprising the following method steps: a) providing a head-up display (10) according to one of the Claims 1 to 5 ; b) emitting light radiation to generate the at least one image on at least one optical phased array as a mirror (18); and c) adjusting the at least one optical phased array such that the light radiation is directed onto the imaging surface; wherein d) a plurality of mirror elements (30) of the optical phased array are at least partially moved longitudinally to reduce speckle patterns. Procedure according to Claim 9 , characterized in that method step d) is based on a calibration step in which the reduction of speckle patterns with different movements of the mirror elements (30) is examined for an image.

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