WO2019238853A1 - Full color optical waveguide display - Google Patents

Abstract

The invention relates to a full color optical waveguide display. The latter has at least two optical waveguides (5R, 5G, 5B) which are optimized for different wavelengths (λR, λG, λB), wherein an adhesive material (72), which has a refractive index comparable to air, is disposed between said optical waveguides (5R, 5G, 5B).

Description

description

Full-color display Lichtwelienleiter

The present invention relates to a full-color optical waveguide display.

A full-color optical waveguide display is known from WO 2017/060665 A1, which has three optical waveguides that are optimized for different wavelengths. These monochrome optical fibers are each designed for one of the colors red, green and blue. By decoupling and overlaying the three colors, a white picture results. The monochrome optical fibers are separated from each other by an air gap. Through the refractive index difference between glass and air, the total reflection of the injected light is ensured on the outer sides of the optical waveguide, the light is guided through the waveguide, and is only coupled out at the location provided by the structuring of the holographic layer. If a display is implemented as an airtight system, in which three monochrome optical fibers are separated by an air gap, condensation can form in the system. If the condensed water settles on the glasses, there is no longer a total reflection at the interface between glass and air. The optical fibers lose their function. In addition, there are problems with stability, particularly when installing such a system in a vehicle, such as an automobile. Vibrations cause vibrations, the optical fibers are not stably separated by the air gap - they can vibrate freely in the system and touch each other with a small air gap. The function of the optical waveguide is no longer ensured. WO 2017/060665 Al suggests that instead of air, a nanoporous material between the Arrange optical fibers. However, this only partially solves the condensation and stability problems. A better solution is desirable.

According to the invention, there is an adhesive material between the optical fibers, which has a refractive index comparable to that of air. The space between the optical fibers is thus completely filled with the adhesive material, air cannot enter, and the formation of condensation is prevented. Due to its compressibility, which is significantly lower than that of air, the adhesive material prevents the optical waveguides from vibrating relative to one another, thus increasing the stability of the entire structure.

A surface of an optical waveguide pointing away from the at least one other optical waveguide is preferably coated with the adhesive material. This makes it possible to arrange further components on this coating without an air gap having to be present.

The adhesive material is preferably silicone. This material is easy to process, has the desired optical and stability properties, and is readily available.

The adhesive bond of the adhesive material to the optical waveguide is, for example, a releasable connection when using silicone, the two components separating when released, without residues of one component remaining on the other. It is therefore a releasable adhesive bond that leaves the individual components undamaged. This enables subsequent corrections, for example when aligning the individual components, without impairing one of the components. One is not non-destructive Detachable connection, however, does not offer this advantage. However, it is less susceptible to subsequent manipulation.

Further variants and their advantages can also be found in the following description of exemplary embodiments with the aid of illustrations.

Figure overview:

Fig.l head-up display according to the prior art

 Fig. 2 schematic beam path

 Fig. 3 schematic beam path with diffuser

 Fig. 4 Beam path with a directed diffuser

 Fig. 5 beam path with several imaging devices

 Fig. 6 Beam path with an image in infinity

 Fig. 7 Beam path with virtual doubling

 Fig. 8 Beam path with optical fiber

 Fig. 9 Beam path with optical fiber

 Fig. 10 head-up display with fiber optic cable

 Fig.ll optical fiber with two-dimensional magnification

Fig. 12 Head-up display with fiber optic cable

 Fig. 13 Optical waveguide in longitudinal section

 Fig. 14 optical fiber of a display according to the invention

figure description

Fig.l shows a schematic diagram of a head-up display according to the prior art. It has an image generator 1, an optical unit 2 and a mirror unit 3. A display element 11 emits a beam of rays SB1, which is reflected by a folding mirror 21 onto a curved mirror 22, which is directed in the direction of the mirror unit 3, here as a windshield 31 of a vehicle is reflected. Get from there the beam of rays SB2 towards the eye 61 of a viewer. The driver sees a virtual image VB, which is located outside the vehicle above the hood or even in front of the vehicle. Due to the interaction of the optical unit 2 and the mirror unit 3, the virtual image VB is an enlarged representation of the image displayed by the display element 11. Here are symbolically a speed limit, the current vehicle speed and navigation instructions. 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 or not at all visible to the viewer. The larger the eyebox 62, the less restricted the viewer is in choosing his seating position.

The curvature of the curved mirror 22 serves on the one hand to prepare the beam path and thus to provide a larger image and a larger eyebox 62. On the other hand, the curvature compensates for a curvature of the windshield 31, so that the virtual image VB corresponds to an enlarged reproduction of the image represented by the display element 11. The curved mirror 22 is rotatably supported by means of a bearing 221. The thereby possible rotation of the curved mirror 22 enables a displacement of the eyebox 62 and thus an adaptation of the position of the eyebox 62 to the position of the eye 61. The folding mirror 21 serves to ensure that the path covered by the beam SB1 between the display element 11 and the curved mirror 22 is long, and at the same time the optical unit 2 is still compact. The optical unit 2 is delimited from the surroundings by a transparent cover 23. The optical elements of the optical unit 2 are thus protected, for example, against dust located in the interior of the vehicle. Is on the cover 23 further an optical film 24, which is to prevent incident sunlight SL from reaching the display element 11 via the mirrors 21, 22. This can be temporarily or permanently damaged by the heat generated. To prevent this, for example, an infrared portion of the sunlight SL is filtered out by means of the optical film 24. A glare shield 25 serves to shade a falling light from the front, so that it is not reflected by the cover 23 in the direction of the windshield 31, which would cause glare to the viewer. In addition to the sun light SL, the light from another interference light source 64 can reach the display element 11.

The same reference numerals are used in the following figures for the same or equivalent elements, and are not necessarily described again for each figure.

2-4 show a simplified schematic beam path in a head-up display. The different reflections are omitted for the sake of clarity. On the left you can see the eye 61, in the middle the image plane 10, which corresponds to both the display element 11 and the virtual image VB, and on the right the aperture A of an imager 12, which is, for example, a spacial light modulator, also called SLM. Light is spatially modulated with an SLM. This can be done in different ways. A special type of SLM is a DMD projector, whereby DMD stands for "Digital Micromirror Device". This is a device in which either a single micromirror movable in the X and Y directions scans a laser beam over an image area, or in which the image area is formed by a large number of micromirrors arranged side by side, which are illuminated by a light source. The eyebox 62 is in the viewing plane 63 by means of a strong line and upper and lower bounds.

2 shows points PI to P4 in the image plane 10. It can be seen that the point PI is only visible from parts of the eyebox 62 due to its position in the image plane 10 and the size of the aperture A. The point P4 is only visible outside the eyebox 62. Only the points P2 and P3 are visible in the eyebox 62; rays emanating from them also fall into the eye 61. Thus, only a small area 101 of the image plane 10 can be detected by the eye 61 in the position shown.

3 shows the same arrangement as FIG. 2, but with a diffuser 13 arranged in the image plane 10. This ensures that light coming from the imager 12 is diffusely scattered. This is indicated in points PI and P4 by means of diffusely scattered beams DS1-DS5, the direction of which indicates which direction is diffusely scattered, and the length of which indicates the intensity in the corresponding direction. It can be seen that the greatest intensity runs in the center of the corresponding beam shown in FIG. 2, illustrated here by the diffusely scattered beam DS3. The greater the angle of the other beams DS1, DS2, DS4, DS5 to the beam DS3, the lower their intensity. It can be seen that the beam DS5 entered the eye 61 from the point PI. The diffusely scattered rays DS3 and DS4 continue to fall into the eyebox 62, while the rays DS1 and DS2 lie outside and are therefore lost. The same applies to point P4.

4 shows the same arrangement as FIG. 3, but with a diffuser 131, which has a special diffusion characteristic. It can be seen that all the diffusely scattered beams DS1 to DS5 emanating from point PI have approximately the same intensity have, and their angular distribution is such that they all get into the eyebox 62. There is therefore no loss of light at this point.

5 shows a similar arrangement to the previous figures, but here with several image generators 12. The image generators 12 are matched to one another in such a way that light rays are emitted in points PI and P4 in a larger angular range, which also means point P4 from the Eyebox 62 is visible out. By increasing the number of imagers 12, an effect similar to that of a diffuser 13 with regard to the visibility of the points PI to P4 in the entire eyebox 62 is achieved.

6 shows an arrangement similar to the previous figures, but here the imager 12 does not focus on one image plane, but collimates to infinity. The rays arriving in the observation plane 63 to a point each run parallel to one another. This makes it possible, instead of arranging several coordinated image generators 12, as shown in FIG. 5, to virtually double the one image generator 12. This is shown in the following figures.

FIG. 7 shows an arrangement similar to FIG. 6, but here with virtual doubling of the image generator 12. For this purpose, a beam splitter is arranged in the beam path of the image generator 12, which reflects part of the radiation onto a mirror 122. The mirror plane 123 of the beam splitter 121 is aligned parallel to the mirror 122. The number of parallel beams of rays emanating from the imager 12, two of which are shown here, is doubled, and their intensity is halved in each case. Thus, both of the beams shown hit the eyebox 62. The virtual imager 12 'is indicated by dashed lines. Through A suitable arrangement of further beam splitters and suitable adaptation of their size can be achieved so that beams can be viewed from any point in the eyebox 62 over a large angular range if the eye 61 is located there.

Fig. 8 shows a similar arrangement as Fig. 7. However, the beam splitter 121 and the mirror 122 are replaced by an optical waveguide 5 here. The optical waveguide 5 has a mirror plane 523 with which light coming from the imager 12 is coupled into the optical waveguide 5. The extension of the original beam direction is indicated by dashed lines. The light coupled into the optical waveguide 5 is totally reflected at its interfaces and is thus guided within the optical waveguide 5. The optical waveguide 5 also has mirror planes 522 which are partially transparent and each couple a part of the light impinging on them from the optical waveguide 5. For the sake of clarity, this is shown with the parallel beam at only one angle. One can see the principle of multiplication of the parallel beams. With a suitable arrangement, he can achieve a sufficiently uniform illumination of the eyebox 62. Instead of using mirror planes 522, 523, the coupling and decoupling can also be carried out by means of diffraction gratings (not shown here) arranged on the surface of the optical waveguide 5 or in another manner known to the person skilled in the art.

FIG. 9 shows an arrangement similar to that of FIG. 8, but here the optical waveguide 5 has a coupling-in hologram 53 and a coupling-out hologram 52, which are arranged as volume holograms in the middle of the optical waveguide 5. Here too, only the principle is indicated. It goes without saying that by suitable selection of the holograms it can be achieved that the entire eyebox 62 is evenly illuminated with parallel beams at all desired angles.

Fig. 10 shows a head-up display similar to Fig.l, here al lerdings in spatial representation and with a Lichtwel lenleiter 5. One recognizes the schematically indicated imager 12, which generates a parallel beam SB1, which by means of the mirror plane 523 in the optical fiber 5 is coupled. Several mirror planes 522 each reflect part of the light impinging on them in the direction of the windshield 31, the mirror unit 3. From this, the light is reflected in the direction of the eye 61, which sees a virtual image VB above the bonnet or at a further distance in front of the vehicle.

Fig.ll shows a schematic spatial representation of an optical fiber 5 with two-dimensional magnification. It has a first optical waveguide 510, which splits the light bundle L2 propagating in it into several light bundles L3, and is thus widening in the y direction. The light bundles L3 pro engage in a second optical waveguide 520, which splits them into a plurality of light bundles L4, and is thus widening in the x direction. In a third optical waveguide 530, a light bundle LI coming from the outside is coupled into the optical waveguide 5 in order to propagate in the first optical waveguide 510 as a light bundle L2. In the lower left area, a coupling hologram 53 can be seen in the third optical waveguide 530, by means of which light LI coming from an imager 12, not shown, is coupled into the optical waveguide 5. In this it spreads in the first optical waveguide 510 according to the drawing at the top right, according to the arrow L2. In this area of the optical waveguide 5 there is a folding hologram 51 which, like many partially arranged one behind the other translucent mirror acts, and produces a widened beam in the Y direction and spreading in the X direction. This is indicated by three arrows L3. In the part of the optical waveguide 5, the second optical waveguide 520, which extends to the right in the illustration, there is a coupling-out hologram 52, which also acts similarly to many partially transparent mirrors arranged one behind the other, and is indicated by arrows L4 in the Z direction upwards from the Optical fiber 5 decouples. A widening takes place in the X direction so that the original incident light bundle LI leaves the optical waveguide 5 as a light bundle L4 enlarged in two dimensions. The optical waveguide 5 thus has a first optical waveguide 510 widening in the y direction, which has the folding hologram 51, a second optical waveguide 520 widening in the x direction, which has the coupling-out hologram 52, and a third optical fiber 530, which has the coupling-in hologram 53.

Fig. 12 shows a spatial representation of a head-up display with three optical fibers 5R, 5G, 5B, which are arranged one above the other and each represent an elementary color red, green and blue. Together they form the optical waveguide 5. The holograms 51, 52, 53 present in the optical waveguides 5 are wavelength-dependent, so that one optical waveguide 5R, 5G, 5B is used for one of the elementary colors. An image generator 1 and an optical unit 2 are shown above the optical waveguide 5. Both together are often referred to as an imaging unit or PGU 100. The optics unit 2 has a mirror 20, by means of which the light generated by the image generator 1 and shaped by the optics unit 2 is deflected in the direction of the respective coupling hologram 53. The light generated by the imaging unit 100 is in the coupling-in area 531, in which the respective coupling-in holograms 53 are located. coupled into the optical fiber 5. It leaves the optical waveguide 5 in the display area 521, in which the respective outcoupling holograms 52 are located. The image generator 1 has three light sources 14R, 14G, 14B for the three elements in tare colors. It can be seen that the entire unit shown has a low overall height compared to its light-emitting surface.

13 shows three optical fibers 5 in longitudinal section. The upper optical waveguide 5 has an ideally flat upper limiting surface 501 and an ideally flat lower limiting surface 502, both of which are arranged parallel to one another. It can be seen that a parallel light bundle LI, which propagates from left to right in the optical waveguide 5, remains unchanged and parallel in cross section due to the parallelism and flatness of the upper and lower boundary surfaces 501, 502. The middle optical waveguide 5 'has upper and lower boundary surfaces 501', 502 'which are not completely flat and are not parallel to one another at least in sections. The optical waveguide 5 'thus has a thickness which varies in the direction of light propagation. It can be seen that the light bundle LI 'is no longer parallel after a few reflections and also has no homogeneous cross section. The lower optical waveguide 5 "has upper and lower limitation surfaces 501", 502 ", which deviate even more from the ideal shape than the upper two. The light beam LI" thus also deviates even more from the ideal shape.

14 shows the optical waveguide 5 of a full-color optical waveguide display according to the invention. The three monochrome optical waveguides 5R, 5G, 5B arranged one above the other can be seen. They are each optimized for different wavelengths XR, XG, XB. The present invention provides an fill the gap between the optical fibers 5R, 5G, 5B with an adhesive material 72, which has a refractive index comparable to air of n = 1.0. Due to the difference in the refractive index between glass and the surrounding filler 72, the total reflection of the injected light is ensured. Advantages of the invention lie in the elimination of the air gap between the optical waveguides 5R, 5G, 5B while maintaining the functionality of the display, in particular if this is a head-up display for a vehicle. This greatly increases the stability of the entire system. As a result, no condensed water can form between the optical waveguides 5R, 5G, 5B and deposit on the glass surfaces. Likewise, no further contamination, such as dust, can get between the optical waveguides 5R, 5G, 5B. Due to the fixed connection of the optical fibers 5R, 5G, 5B to one another, the system has greater stability and improved robustness. It is better protected against environmental influences such as vibrations or changes in the climatic conditions. Furthermore, the use of the adhesive material 72 between the optical fibers 5R, 5G, 5B ensures an exact positioning of the optical fibers 5R, 5G, 5B with respect to one another, which no longer changes due to the adhesion during operation, so that the images of the monochrome optical fibers 5R, Overlay 5G, 5B as desired. The solution according to the invention can also be used for fixing other optical components in complex systems while maintaining functionality. Instead of using a material 72 with a refractive index comparable to air, which has a refractive index n = 1.0, a material with a higher refractive index is used according to a variant of the invention. In this case, a waveguide medium with a correspondingly higher refractive index is used, so that total reflection at the interfaces of the waveguide medium is still ensured. It is known to use a nanoporous material between the optical waveguides 5R, 5G, 5B. Such a material is characterized by extremely thin material threads, which ensure the stability of the nanoporous material. However, the low refractive index is due to the high proportion of air. The proportion of material threads is negligible compared to the air trapped in the system. Air cannot circulate freely here, but humidity can still penetrate. It is difficult to remove them again due to the low circulation. The invention aims at a material 72 with a low refractive index that no longer requires air to realize the difference in refractive index. A type of silicone was mentioned here as an example. The previous air gap is therefore massively filled with the material 72, while when using a nanoporous material there is still a high proportion of air in the gap. An advantage of the invention compared to the use of nanoporous material is the increased stability, since solid materials, such as silicones, are less sensitive than nanoporous materials. In addition, nanoporous materials can lead to an undesirable scattering of light, since the light rays are deflected with each contact with a material thread. Such contacts exist several times alone within an air gap or a nanoporous layer. In the case of special optical materials 72, as proposed according to the invention, this is not the case.

In other words, the invention relates to the construction of a robust, compact head-up display based on optical waveguides without an air gap. The proposed solution prevents condensation from forming between the optical fibers 5R, 5G, 5B and reduces the vibration problem. Further details can be found in the claims or the introduction to the description. It is understood that the measures given can also be used according to the invention in a modification or in a combination other than that described here.

Reference character list

1 image generator

 100 PGU (imaging unit)

10 image plane

 101 area (the image plane)

11 display element

 12 imagers

 121 beam splitters

 122 mirrors

 123 mirror plane

 13, 131 diffuser

14, 14R, 14G, 14B light source

2 optics unit

 20 mirrors

 21 folding mirrors

 22 curved mirror

 221 storage

 23 transparent cover

24 optical film

 25 glare protection

3 mirror unit

 31 windshield

 311 visor

4 control unit

 41 control unit

 411 line

 41 IR, 41 IG, 411B line

413R, 413G, 413B cable 5 optical fibers

 500 stacks (of optical fibers)

 501 upper boundary surface

 502 lower boundary surface

 503 left boundary surface

 504 right boundary surface

 505 front boundary surface

 506 rear boundary surface

 507 Additional information

 51 folding hologram

 510 first optical waveguide (widening in the y direction)

51001.51002 interface

 5101, ..., 510n first optical waveguide

 52 decoupling hologram

 520 second optical waveguide (pointing in the x direction)

 52001.52002 interface

 521 decoupling area

 522 mirror plane

 523 mirror plane

 53 coupling hologram

 530 third optical fiber (coupling)

 531 coupling area

 532 coupling structure

 54 substrate

 55 top layer

 6 hologram layer

60 viewers

 61 eye

 62 eyebox

 63 Viewing level

64 Interference light source 72 adhesive material

A aperture

 D distance

D _D Thick top layer

D _s thick substrate

 DS1 ... DS5 diffuse scattered rays LI ... L4 light

L41, L42 partial light beam

LPR, LPG, LPB light package

LSI, LS2 light rays

 La direction of light

 N normal

 PI ... P4 point (on the image plane) RE Real plane

 SB1, SB2 beams

SL sunlight

 U1-U4 potential

 VB, VB ', VB "virtual image

VE virtual level

La main direction angle

XR, XG, XB wavelength

Claims

claims 1) Full-color optical waveguide display, comprising at least two optical waveguides (5R, 5G, 5B) optimized for different wavelengths (XR, XG, XB), with an adhesive material (5R, 5G, 5B) between these optical waveguides ( 72), which has a refractive index comparable to air. 2) Full-color optical waveguide display according to claim 1, wherein one of the at least one other optical waveguide (5R, 5G, 5B) facing surface of an optical waveguide (5R, 5G, 5B) is coated with the adhesive material (72). 3) Full-color optical fiber display according to claim 1 or 2, wherein the adhesive material (72) is silicone. 4) Full-color optical waveguide display according to one of the preceding claims, wherein the space between two optical waveguides (5R, 5G, 5B) is solidly filled with material (72).