DE102024118867A1 - Waveguide, curved disk with such a waveguide, and display device with such a waveguide - Google Patents

Abstract

A waveguide with
a coupling area (4) and a coupling area (5) spaced apart from it,
wherein the coupling region (4) couples at least a part of the incident radiation into the waveguide in such a way that the coupled part propagates as a coupled beam in the waveguide (1) by reflection to the output coupling region (5), which deflects at least a part of the coupled beam in such a way that the deflected part exits the waveguide (1),
wherein the waveguide (1) has several straight-line extending transparent segments (9 ₁ - 9 ₅ ) in which the coupled beam of rays is propagated by reflections,
wherein each segment (9 ₁ - 9 ₅ ) has a planar segment front (10 ₁ - 10 ₅ ) and a planar segment back (11 ₁ - 11 ₅ ) which are parallel to each other,
wherein the segment front faces (10 ₁ - 10 ₅ ) of directly adjacent segments (9 ₁ , 9 ₂ ; 9 ₂ , 9 ₃ ; 9 ₃ , 9 ₄ ; 9 ₄ , 9 ₅ ) enclose an angle (Ω ₁ , Ω ₂ , Ω ₃ , Ω ₄ ) of non-180° with each other in order to reproduce a curved path of an imaginary front face (14) from the coupling area to the coupling area (4, 5),
wherein of two directly adjacent segments at least one segment has a compensation hologram (12 ₁ - 12 ₄ , 13 ₂ - 13 ₅ ; 16, 17) onto which the coupled beam of light hits,
wherein the compensation hologram (12 ₁ - 12 ₄ , 13 ₂ - 13 ₅ ; 16, 17) causes the coupled beam of rays to propagate in the two directly adjacent segments with the same reflection angle (α) for a majority of the reflections.

Description

The present invention relates to a waveguide, a transparent curved disk with such a waveguide, and a display device with such a waveguide.

Waveguides can be used for display devices and often have an input area and a separate output area, whereby the light to be guided is coupled into the waveguide via the input area and guided to the output area by means of reflection and coupled out again via the output area.

Such waveguides can be integrated into transparent disks, for example. If the disks are curved and thin, the waveguides are typically formed in the same shape, with a curved front and back surface. However, since reflection to guide the light within the waveguide occurs at these curved surfaces, this unfortunately causes the beam path to diverge. This results in aberrations that cause wavefront errors dependent on the curvature and propagation distance. If the waveguide is part of an imaging system, this reduces image quality. If the waveguide carries an image hologram, it adversely affects the quality of the hologram reconstruction. Furthermore, varying reflection angles lead to incomplete imaging of the field of view.

Based on this, the object of the invention is therefore to provide an improved waveguide. Furthermore, a transparent curved disk with such a waveguide and a display device with such a waveguide are to be provided.

The invention is defined in the independent claims. Advantageous embodiments are specified in the dependent claims.

The waveguide according to the invention can have an input region and a spaced-apart output region, wherein the input region couples at least a portion of incident radiation into the waveguide such that the coupled portion propagates as a coupled beam within the waveguide by reflection to the output region, which deflects at least a portion of the coupled beam such that the deflected portion exits the waveguide. The waveguide can have several straight-extending transparent segments in which the coupled beam propagates by reflection, each segment having a flat front and a flat back surface that are parallel to each other.

The front faces of directly adjacent segments can form an angle other than 180° with each other, thus replicating a curved path of an imaginary front face from the coupling-in to the coupling-out region. Of two directly adjacent segments, at least one can have a compensation hologram onto which the coupled beam of light strikes, the compensation hologram causing the coupled beam of light to propagate with the same reflection angle in the two directly adjacent segments for a majority of reflections.

Thus, according to the invention, the predetermined curved profile of the conceptual front face can be replaced by the flat segment front faces in a segmented manner, so that no varying reflection angles occur. Individual deviating reflection angles, which may be unavoidable due to the segmented design of the waveguide, are compensated by the compensation hologram (or by several compensation holograms), so that the overall beam path does not diverge and thus excellent beam guidance can be provided. At the same time, the desired curved shape of the waveguide can be realized, so that the waveguide can, for example, be part of a curved thin disk and/or be integrated into it. The curved disk can, for example, have a cylindrical curvature. The disk and/or the waveguide can have the predetermined curved profile in a first plane and extend straight (without curvature) perpendicular to it.

In particular, the flat segment front faces can run perpendicular to the first plane, so that the specified curved profile is present in the first plane.

The reflections for guiding the coupled beam of light can occur, in particular, at the front and rear faces of the segments. At least one of the reflections can be a total internal reflection or a reflection at a reflective or partially reflective layer or coating. Several or all of the reflections can also be total internal reflections. Furthermore, it is possible that a reflective coating is applied to one or more front faces of the segments and/or to one or more rear faces, at which at least one of the reflections is reflected. Reflections (or several or all reflections) take place.

The coupling region can be configured to deflect the portion of the radiation upon coupling, which then propagates as a coupled beam in the waveguide. In particular, the coupling region can be reflective, refractive, and/or diffractive. Preferably, the coupling region can feature a hologram.

The waveguide can be designed such that a first and a directly adjacent second segment are formed as separate segments, with the first segment having an outcoupling hologram that couples out the coupled beam of light in such a way that it hits the second segment and is coupled into it.

The second segment may have a coupling hologram that couples the beam of light coming from the first segment into the second segment. It is also possible that the second segment does not have a coupling hologram. In this case, the beam of light coming from the first segment can enter the second segment, for example, via its front or back surface.

The output hologram and/or the input hologram can serve as a compensation hologram.

In particular, the waveguide can have three or more separate segments, each designed in the same way as the first and second segments.

Furthermore, it is possible that at least two directly adjacent segments of the waveguides are formed as a single piece. In this case, the coupled beam of radiation does not need to exit via a front or back surface at the transition between the two directly adjacent segments and re-enter the next segment via the front and back surfaces, but can propagate the coupled beam of radiation exclusively within the material of the first and second segments.

The waveguide according to the invention can comprise a combination of separate segments and segments formed in one piece. However, it is also possible that the waveguide comprises only separate segments or only segments joined together in one piece.

The output area can display a hologram or an image hologram.

In particular, the output coupling area can be configured as a holographic diffuser, so that image information contained in the coupled beam is perceptible to a viewer as an image by means of the diffuser function. The image information can, for example, be perceptible in a plane of the output coupling area. Thus, different images can be displayed (depending on the information in the coupled beam).

Furthermore, the output coupling area can be configured as an image hologram, with the image information embedded (and unchangeable) in the image hologram. When the coupled beam of light strikes the image hologram, the embedded image is reconstructed in a known manner and thus becomes perceptible to an observer. The image hologram can, in particular, be configured as an image-plane hologram, in which the reconstructed image is perceptible, for example, as a (essentially planar) image in the waveguide or as a (essentially planar) image in a film or coating in which the hologram is formed. The image hologram can be configured to have several embedded images designed for different wavelengths, so that, depending on the selected wavelength of the coupled radiation, one of the images of the image hologram can be selectively reconstructed.

The waveguide segments can be made of plastic and/or glass.

All described holograms can be designed as reflective holograms and/or as transmissive holograms. Furthermore, the holograms can be designed, for example, as volume holograms or surface holograms. At least one, several, or all of the holograms can be designed, for example, in a film or coating that may be part of the corresponding segment or connected to it.

The waveguide according to the invention can be configured to perform an infinity-to-infinity mapping. However, it is also possible for it to perform a finite-to-infinity mapping, an infinite-to-finite mapping, or a finite-to-finite mapping.

Furthermore, a transparent curved disc with a waveguide according to the invention (including all further developments) is provided. The transparent curved disc can, in particular, have a cylindrical curvature or any other arbitrary curvature. It can, for example, be a disc in a vehicle on land, water, and/or air. In particular, it can be a window or door. (or parts thereof) of passenger compartments of trains (preferably ICE trains). It could also include other panes of glass, such as shop windows, glass from household appliances, furniture, or refrigerated display cases. It could also include curved visors on helmets or protective windscreens on motorcycles, or similar items.

Furthermore, a display device is provided with a waveguide according to the invention (including all further developments) and a radiation source that emits the radiation incident on the coupling area.

If the output coupling area displays an image hologram, the radiation source can be, for example, an LED and/or laser. If the output coupling area is designed as a diffuser, the radiation source can be, for example, an image module that generates an image and directs it as a beam of light onto the input coupling area.

The image module can include an image sensor (preferably planar) and a control unit (e.g., with a processor and memory) for image generation. The image sensor can be, for example, an LCD module, an LCoS module, an OLED module, a microLED module, or a tilting mirror matrix. Furthermore, the image sensor can have a plurality of pixels, arranged, for example, in columns and rows. The image sensor can also be self-illuminating and/or non-self-illuminating.

Furthermore, an imaging device is provided with a waveguide according to the invention (including all further developments) and a detector on which the deflected part of the coupled beam exiting the waveguide hits.

The detector can be connected to the flat front or back surface of one of the segments. In particular, a direct connection is possible. The detector can be a digital image sensor (e.g., a CCD sensor or a CMOS sensor), a detector array, or, for example, a solar cell.

Furthermore, the imaging device can be designed such that at least one optical imaging element is arranged in the area between the detector and the flat front or back surface of the segment. This at least one optical imaging element can be, for example, a lens, a refractive lens, or a refractive camera lens. It is also possible for the area between the detector and the flat front or back surface of the segment to be free of imaging optical elements. In other words, the deflected portion of the coupled beam exiting the waveguide strikes the detector without having passed through any further optical imaging elements. In this case, it is advantageous if the output coupling area, in addition to being deflected, also possesses an optical imaging property.

The imaging device according to the invention can be designed as a camera (e.g. digital camera or video camera).

In the display device, the waveguide can be part of a curved disk. The curved disk is preferably transparent.

It is understood that the features mentioned above and those to be explained below can be used not only in the combinations given, but also in other combinations or on their own, without leaving the scope of the present invention.

• 1 eine schematische Darstellung einer holographischen Anzeigevorrichtung 2 mit einem erfindungsgemäßen Wellenleiter 1;
• 2 eine schematische Darstellung zur Erläuterung der segmentierten Nachstellung des gekrümmten Verlaufs einer gedachten Vorderseite 14 durch die Segmente 9₁ - 9₅ des Wellenleiters 1 von 1;
• 3 eine schematische Darstellung eines bekannten Wellenleiters 1' mit gekrümmter Vorder- und Rückseite 10', 11';
• 4 eine schematische Darstellung einer Abwandlung der holographischen Anzeigevorrichtung 2 und des Wellenleiters 1 von 1;
• 5 eine schematische Darstellung einer weiteren holographischen Anzeigevorrichtung 2 mit einem anderen Ausführungsbeispiel eines erfindungsgemäßen Wellenleiters 1;
• 6 eine Abwandlung der holographischen Anzeigevorrichtung 2 und des Wellenleiters 1 von 5, und
• 7 eine schematische Darstellung einer holographischen Abbildungsvorrichtung 20 mit einem erfindungsgemäßen Wellenleiter 1 gemäß 1.

The invention is explained in more detail below with reference to exemplary embodiments and the accompanying drawings, which also disclose essential features of the invention. These exemplary embodiments serve only for illustration and are not to be interpreted as limiting. For example, a description of an exemplary embodiment with a plurality of elements or components is not to be interpreted as meaning that all of these elements or components are necessary for implementation. Rather, other exemplary embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different exemplary embodiments may be combined with one another unless otherwise specified. Modifications and variations described for one of the exemplary embodiments may also be applicable to other exemplary embodiments. To avoid repetition, identical or corresponding elements in different figures are designated with the same reference numerals and are not explained multiple times. The figures show:

• 1 a schematic representation of a holographic display device 2 with a waveguide 1 according to the invention;
• 2 a schematic representation to explain the segmented reproduction of the curved path of an imaginary front face 14 by the segments 9 ₁ - 9 ₅ of the waveguide 1 of 1 ;
• 3 a schematic representation of a known waveguide 1' with curved front and back sides 10', 11';
• 4 a schematic representation of a modification of the holographic display device 2 and the waveguide 1 of 1 ;
• 5 a schematic representation of a further holographic display device 2 with another embodiment of a waveguide 1 according to the invention;
• 6 a modification of the holographic display device 2 and the waveguide 1 of 5 , and
• 7 a schematic representation of a holographic imaging device 20 with a waveguide 1 according to the invention 1 .

At the in 1 In the illustrated embodiment of a waveguide 1 according to the invention, this part is a holographic display device 2.

The holographic display device 2 comprises, in addition to the waveguide 1, an image generation module 3, which generates an image that is coupled into the waveguide 1 via an input coupling area 4 of the waveguide 1, guided in the waveguide 1 (as will be described in detail below) up to an output coupling area 5 spaced apart from the input coupling area 4 and is coupled out by means of the output coupling area 5, so that a user can perceive the image with his eye A.

To generate the image, the image generation module 3 comprises an image sensor 6, which is controlled by a control unit 7 containing a processor P and a memory M. The image thus generated is then fed to the coupling area 4 via an image optic 8 (which may, for example, have one or more lenses). The image optic 8 is optional and can also be omitted.

The image source 6 can be, for example, a planar image source 6, such as an LCD module, an LCoS module, an OLED module, a µLED module, or a tilting mirror matrix. The image source 6 can have a plurality of pixels, which can be arranged, for example, in numbers and columns. The image source can be, for example, self-illuminating or non-self-illuminating.

In the exemplary embodiment of 1 Five straight _, transparent segments _91–95 . Each segment _91–95 has a flat front face _101–105 and a flat back face _111–115 , which _are aligned parallel to each other. The front faces _101–105 and the _{back faces 111–115 extend} perpendicularly to the xy-plane and the drawing plane _{, respectively} . Each segment _91–95 has the form _of a plane-parallel plate.

The first segment 9 ₁ has a coupling area 4 on its rear side 11 ₁ , which is configured here as a hologram. However, the coupling area 4 can also be configured in any other way. For example, it can be configured as a prismatic element. Furthermore, it is possible to configure the image generation module 3 such that the generated image enters the first segment 9 ₁ at the desired angle to the beam path, in which case the area of the rear side 11 ₁ through which the generated image enters the first segment 9 ₁ is the coupling area 4.

As in 1 As shown schematically, in the embodiment described here, the coupling area 4 deflects the coupled image (two light rays from a pixel are shown as representatives of the generated and coupled image - one with a solid line and one with a dashed line) so that the coupled image is then guided by means of total internal reflection at the front of segment 10 ₁ and the back of segment 11 ₁ to an output hologram 12 ₁ of the first segment 9 ₁ .

The segments _91-95 are arranged such _{that the segment front faces 101-105 of directly adjacent segments 91-95 enclose an} angle _{Ω1 , Ω2 , Ω3} and _Ω4 of non-180° with each other, so that the segment front faces _101-105 trace a curved path of an imaginary front face 14 (in the xy-plane), as _shown schematically in 2 shown.

The second to fourth segments 9 ₂ - 9 ₄ each have an input hologram 13 ₂ - 13 ₄ and an output hologram 12 ₂ - 12 ₄ , as shown in 1 The fifth segment features a coupling hologram 13 ₅ .

As schematically in 1 As shown, the coupled image is coupled out of the corresponding segment 9 ₁ - 9 ₄ via the respective output hologram 12 ₁ - 12 ₄ and coupled back into the corresponding segment 9 ₂ - 9 ₅ via the respective input hologram 13 ₂ - 13 ₅ of the directly adjacent segment 9 ₂ - 9 ₅ , whereby in each segment 9 ₁ - 9 ₅ the coupled image is guided by total internal reflection at the segment front 10 ₁ - 10 ₅ and the segment back 11 ₁ - 11 _5. The light then strikes the output coupling area 5 in the fifth segment 9 ₅ , which causes output coupling via the segment front 10 ₅ .

The outcoupling hologram 12 ₁ of the first segment 9 ₁ and the incoupling hologram 13 ₂ of the second segment 9 ₂ are designed such that the coupled image in the second segment 9 ₂ is guided with the same reflection angle α (to the normal, which is schematically drawn, of the surface at the point of incidence) during total internal reflection at the front of the segment 10 ₂ and the back of the segment 11 ₂ as in the first segment 9 ₁ .

The same applies to the combination of the second output hologram 12 ₂ and the third input hologram 13 ₃ , to the combination of the third output hologram 12 ₃ and the fourth input hologram 13 ₄ , and to the combination of the fourth output hologram 12 ₄ and the fifth input hologram 13 ₅ .

Thus _, the coupled image is guided with the same reflection angle α in each segment _91–95 , so that the beam path does not diverge in segments _91–95 and no unwanted aberrations are introduced by the guidance in segments _{91–95 .} More precisely, the light rays L1, L2 from each field point can have a different guidance angle (i.e. _, when a field of view is propagated through the waveguide), but this angle does not change in each individual segment _{91–95 .}

In 3 The diagram schematically shows the beam path into a curved waveguide 1', whose front face 10' corresponds to the curvature of the imaginary front face 14. 2 The waveguide exhibits a characteristic curvature. Due to the curvature of the front 10' and back 11' of the waveguide 1', the reflection angle changes with each reflection. If the reflection angle α is present at the first reflection, the reflection angles _β1 , _β3 , and _β5 , and _β2 , _β4 , and _β6, respectively, occur at subsequent reflections, where _β1 and _β2 , _β3 and _β4 , and _β5 and _β6 differ. This causes the beam path to diverge, resulting in wavefront errors that depend on the curvature of the front and back surfaces and the propagation distance. Incomplete field of view imaging can also occur.

The segmented design of the waveguide 1 according to the invention avoids the problems described, since the same reflection angle α is always present during propagation of the coupled image in the waveguide (for each field point). Thus, a curved waveguide 1 with excellent optical properties can be provided.

Since the out-coupling and in-coupling holograms 12 ₁ - 12 ₄ , 13 ₂ - 13 ₅ serve to ensure that the reflection angles α in adjacent segments 9 ₁ - 9 ₄ are equal, these holograms can also be called compensation holograms.

In a further development not shown, it is possible to omit the coupling hologram 13 ₂ - 13 ₅ for at least one of the segments 9 ₂ - 9 _5. In this case, only the corresponding output coupling hologram 12 ₁ - 12 ₄ needs to be designed such that, after entering the corresponding segment, the coupled image is propagated in such a way that the desired reflection angle α is achieved.

Segments _91-95 can be _made of glass or plastic.

The output area 5 can be configured as a hologram. In particular, it can be configured as a holographic diffuser, so that a user can perceive the coupled-in image, which strikes the output area 5, as an image in the plane of the output area 5. The output area 5 can therefore also be described as an image hologram, whereby, when configured as a holographic diffuser, the image information is provided by the coupled-in image (or the correspondingly guided light rays).

However, it is also possible to design the output coupling area as a hologram in which the desired image information is embedded within the hologram. In this case, it is only necessary to couple light from a suitable light source 15 into the waveguide 1 via the input coupling area 4, as shown schematically in 4 The coupled light is shown in the same way as in conjunction with 1 As described, the light is guided via segments _91–95 to the output area ₅ and directed onto it, so that the image information exposed into the output area 5 is reconstructed by means of the incident light or beam of light, making the reconstructed image perceptible to a viewer. The output area 5 can, in particular, be designed as an image-plane hologram, in which the reconstructed image is perceptible as a (essentially planar) image.

A laser and/or an LED can be used as the light source 15, for example.

In 5 is a modification of waveguide 1 according to 1 shown. In the exemplary embodiment of 5 Waveguide 1 has three straight segments ₉₁ - _93. Waveguide 1 in 5 is formed in one piece or monolithically. However, due to the three segments _{91–93 ,} the reflection angle α would change, as is the case, for example, for the dashed beam at the first reflection in the second segment _92. Here, the reflection angle δ is... So that a reflection occurs again in the further propagation process... Since the angle of reflection α is present, the second segment 9 ₂ exhibits a first compensation hologram 16. Similarly, the third segment 9 ₃ exhibits a second compensation hologram 17. This ensures that the same reflection angle α is present in each subsequent segment.

In embodiment 5, any coupling losses that may occur between the separate segments 9 ₁ - 9 ₃ according to embodiments 1 and 4 can be advantageously avoided.

In embodiment 5, the curved waveguide can be referred to as a segmented monolithic waveguide 1. With such a waveguide 1, the desired coupling, guiding, and decoupling of the generated image is possible.

In 6 is a variation of the embodiment of 5 shown. In this case, it is done in the same way as in the embodiment of 4 The output coupling area 5 is designed as an image hologram and a light source 15 is provided to supply the light with which the image in the output coupling area 5 is then reconstructed when the light coupled into and guided in the curved monolithic waveguide 1 hits the output coupling area 5.

In 7 is an embodiment of an imaging device 20 with a waveguide 1 according to 1 shown. The imaging device can project an object 21 (in 7 (A star is shown as an example) is imaged onto a detector 22. Radiation coming from the object 21 can be collimated by means of a first optic 23 and directed onto the coupling area 4, so that the coupled radiation is guided in the waveguide 1 as described to the coupling area 5 and coupled out from there. The coupled-out radiation can then be directed or focused onto the detector 22 by means of a second optic 24. The first and/or second optic 23, 24 are optional and can also be omitted. In the embodiment of 7 The imaging device can also be referred to as a camera. Furthermore, the imaging device 20 can also be the waveguide 1 of the other embodiments (in particular according to 5 and 6 exhibit.

Claims (14)

Waveguide with an input region (4) and an output region (5) spaced apart therefrom, wherein the input region (4) couples at least a portion of incident radiation into the waveguide such that the coupled portion propagates as an input beam in the waveguide (1) by reflection to the output region (5), which deflects at least a portion of the coupled beam such that the deflected portion exits the waveguide (1), wherein the waveguide (1) has several straight-extending transparent segments (9 ₁ - 9 ₅ ) in which the coupled beam propagates by reflection, wherein each segment (9 ₁ - 9 ₅ ) has a planar segment front (10 ₁ - 10 ₅ ) and a planar segment back (11 ₁ - 11 ₅ ) which are parallel to each other, wherein the segment fronts (10 ₁ - 10 ₅ ) of directly adjacent segments (9 ₁ , ₉₂ ; ₉₂ , ₉₃ ; ₉₃ , ₉₄ ; ₉₄ , ₉₅ ) enclose an angle ( _Ω1 , _Ω2 , _Ω3 , _Ω4 ) of non-180° with each other in order to reproduce a curved path of an imaginary front face (14) from the coupling-in to the coupling-out region (4, 5), wherein of any two directly adjacent segments at least one segment _{has a compensation hologram (121-124, 132-135 ; 16} , ₁₇ ) onto which the coupled beam of light strikes, wherein the compensation hologram ( _121-124 , _132-135 ; 16, ₁₇ ) causes the coupled beam of light to be _enclosed in the two directly propagated to adjacent segments in a majority of reflections with the same reflection angle (α). waveguides Claim 1 , wherein the planar segment front faces (10 ₁ - 10 ₅ ) run perpendicular to a first plane, so that the specified curved profile is in the first plane. waveguides Claim 1 or 2 , wherein the coupling region (4) deflects part of the radiation during coupling. Waveguide according to one of the above claims, wherein the coupling area (4) has a hologram. Waveguide according to one of the above claims, wherein at least one of the reflections in the waveguide is an internal total reflection. Waveguide according to one of the above claims, wherein a first and a directly adjacent second segment (9 ₁ , 9 ₂ ) are designed as separate segments, wherein the first segment has an outcoupling hologram (12 ₁ ) which couples out the coupled beam of rays in such a way that it hits the second segment (9 ₂ ) and is coupled into it. waveguides Claim 6 , wherein the second segment (9 ₂ ) has a coupling hologram (13 ₂ ) that couples the beam of light coming from the first segment into the second segment. waveguides Claim 6 or 7 , wherein the output hologram (12 ₁ ) and/or the input hologram (13 ₂ ) serve as compensation holograms. Waveguide according to one of the above claims, wherein at least two directly adjacent segments (9 ₁ - 9 ₅ ) are formed in one piece. Waveguide according to one of the above claims, wherein the output coupling area has a hologram or an image hologram. Transparent curved disk with a waveguide according to one of the above claims. Display device with a waveguide after one of the Claims 1 until 10 and a radiation source (3; 15) that emits the radiation incident on the coupling area (4). Imaging device with waveguide according to one of the Claims 1 until 10 and a detector (22) onto which the deflected part of the coupled beam exiting the waveguide (1) meets. Device according to Claim 12 or 13 , wherein the waveguide (1) is part of a curved disk.