LIGHT GUIDE, IMAGING DEVICE AND HMD WITH SEPARATE IMAGING CHANNELS

Description

[0001] The present invention relates to an optical fiber for an imaging device for generating a virtual image from a source image displayed on an image sensor. The invention also relates to a head-mounted display (HMD).

[0002] A common type of head-mounted display uses screens worn in front of the eyes, presenting electronic images such as computer-generated images or images captured by cameras. These types of head-mounted displays are often bulky and do not allow for direct perception of the surroundings.

[0003] More recently, head-mounted displays have been developed that are able to combine electronic images with the user's immediate perception of their surroundings, thus presenting an electronic image without obstructing their direct perception of the environment. Such head-mounted displays, also known as smart glasses when designed in the form of eyeglasses, enable the use of this technology in everyday life.

[0004] When combining electronic images with the directly perceived image of the environment, the following principles are essentially used in data glasses, on which the combination can be based: 1. Use of ordinary eyeglasses with a beam combiner (e.g., a beam splitter cube) attached to the front. 2. Coupling of the light between the head and the lens from the side and reflection of the light at the inside of the lens towards the eye, whereby diffraction gratings, Fresnel elements, or similar devices can be used to assist this process. 3. Guiding of the light from the electronic image by means of total internal reflection within the lens and merging of the light path of the electronic image with the immediate image of the surroundings using an output coupling structure arranged within the lens to couple the light path of the electronic image out of the lens towards the eye. The lens thus serves as a light guide for the coupled light.

[0005] The first principle works well visually, but has very low social acceptance because the front-mounted beam combiner is very conspicuous and large. Furthermore, it makes the glasses front-heavy. The second principle can only be implemented anatomically with a significantly increased distance between the glasses and the head, which is also unacceptable.

[0006] The more promising approaches therefore start with the third principle, namely guiding the light within the spectacle lens as a light guide. The output structure can be designed as a diffraction grating, a partially transparent, inclined mirror, or in the form of partially transparent Fresnel elements. In the case of a diffraction grating, the beam path of the electronic image is coupled out of the spectacle lens, for example, via the first-order diffraction maximum, while the observation light can pass through the output structure with minimal interference via the zero-order diffraction maximum.

[0007] In an HMD operating according to the third principle described above, divergent beams emanating from a field point of the field represented by a source image (hereinafter referred to as the source image field) are typically collimated or largely collimated and guided through the optical fiber as collimated beams. The diameter of the beams is determined by the entrance pupil of the imaging device, of which the optical fiber is a part. The central rays of the beams are referred to as principal rays. The angle between the beams representing the left and right edges of the source image field, or between their principal rays as measured in the region of the exit pupil, is called the horizontal field angle.The vertical field angle is defined as the angle, measured at the exit pupil, between the beams representing the vertical edges of the original image field, or their principal rays. Large field angles—especially large horizontal field angles—occur when the original image field is large, particularly when displaying an image in 16:9 format. The field angle causes the cross-sectional area of ​​all transmitted beams to increase with increasing distance from the eye. Consequently, at large field angles, the distance between the outer principal rays becomes so great that coupling is generally no longer possible via a side surface of the lens, but only via the front or back surface, resulting in large coupling structures.An optical fiber in which the coupling of the beams occurs via the back surface, i.e. the surface facing the eye, is described, for example, in US 2011 / 0062998 A1.

[0008] US 2012 / 0057253 A1 describes a coupling structure that has two tilted sub-surfaces.

[0009] DE 102015 122 131 B3 describes the tilting of a entire Fresnel surface used to couple out an imaging beam path from a spectacle lens.

[0010] DE 10 2014 207 492 A1 describes Fresnel surfaces that are used for decoupling and that create a mapping from the image transmitter or an intermediate image of the image transmitter into the virtual intermediate image.

[0011] DE 10 2014 207 500 B3 describes a reflective layer located between the coupling area of ​​a spectacle lens and the coupling structure of the spectacle lens, which serves to guide the beam.

[0012] US 2014 / 0226215 A1 describes a light guide in a display for representing a virtual image, in which the coupling of the imaging beam path into the light guide takes place via the circumferential surface of the light guide.

[0013] US patent 2017 / 0184855 A1 describes a device for displaying a virtual image.

[0014] JP 2002-31777 A shows electronic glasses with an imaging device having two coupling elements whose orientations are tilted relative to each other about an axis.

[0015] DE 10 2014 115 341 A1 describes an imaging optic for data glasses with an output coupling structure that has two substructures tilted relative to each other about an axis.

[0016] US 2017 / 0285347 A1 describes lenses for data glasses, whereby the lenses may have output coupling structures tilted relative to each other about an axis.

[0017] The object of the present invention is to provide an imaging device and an HMD in which the coupling structures can be kept small.

[0018] This problem is solved by an imaging device according to claim 1 and an HMD according to claim 12. The dependent claims contain advantageous embodiments of the invention.

[0019] An imaging device according to the invention for generating a virtual image comprises an image transmitter with at least two image transmitter sections for displaying at least two output image field areas of an output image and a light guide, wherein the light guide comprises a coupling structure for coupling beams emanating from the output image into the optical fiber and a planar coupling structure for coupling the beams coupled into the optical fiber out of the optical fiber, wherein the planar coupling structure comprises at least two sub-areas and wherein each sub-area is assigned to a different of the output image field areas and couples out the beams emanating from the corresponding output image field area.

[0020] According to the invention, the partial surfaces of the output structure are tilted relative to each other. The two partial surfaces of the output structure are tilted about two axes that are not parallel to each other, preferably about two axes perpendicular to each other, such that horizontally adjacent field areas are generated in the virtual image from vertically superimposed fields in the output image, or vertically superimposed fields are generated in the virtual image from horizontally adjacent fields in the output image.

[0021] The image sensor sections do not necessarily need to be connected or part of the same display. In other words, the image sensor can be designed as a single display or as an arrangement of at least two displays. The effects achievable with the imaging device according to the invention result directly from the use of the optical fiber according to the invention and the effects described above.

[0022] Tilting the partial surfaces of the output coupling structure relative to each other allows the cross-sectional area occupied by the beams transmitted through the optical fiber in the area of ​​the input structure to be manipulated in such a way that the cross-sectional area can be adapted to the desired dimensions. In particular, the cross-sectional area can be reduced in the direction of the thickness of the optical fiber. This makes it possible to design the optical fiber such that it has a rear surface facing the user's eye, a front surface facing away from the user's eye, and a circumferential surface connecting the rear surface to the front surface, with the input structure being arranged in the optical fiber such that the beams can be coupled in via the circumferential surface.

[0023] If, in a coordinate system where the z-axis is perpendicular to the surface representing the exit pupil and points towards the optical fiber, the two sub-surfaces are tilted relative to each other about the y-axis, the beams of light reaching the exit pupil can be guided through regions of the optical fiber that are offset from each other in the x-direction. This makes it possible, for example, to use image sensors offset from each other in the x-direction to represent different lateral output image field regions in order to generate the output image.

[0024] Tilting the partial surfaces relative to each other around the x-axis allows the beams reaching the exit pupil to be guided closer together in the region of the coupling structure, thereby reducing the extent of the beam distribution in the z-direction (direction of the optical fiber's thickness). More precisely, when the beams are projected onto the xz-plane in the region of the coupling structure, the extent of this projection in the z-direction is reduced. This facilitates the use of coupling structures with a smaller extent in the z-direction and, in particular, can enable coupling via a side surface of the optical fiber—that is, via a section of the circumferential surface located laterally on the optical fiber—even with a large horizontal output field. This side surface can also simultaneously form the coupling structure.

[0025] In general, tilting the partial surfaces around two non-parallel axes allows manipulation of the beam distribution in the coupling structure area, resulting in a desired shape. Specifically, the aspect ratio of the cross-sectional area of ​​the beam distribution can be altered. This makes it possible, for example, to shift beams so that horizontally adjacent output image field areas are represented by vertically shifted beams in the coupling structure area. Furthermore, these beams can also be shifted horizontally relative to each other.Although the output image can then only be displayed via an enlarged image sensor or an image sensor with separate displays for the output image field areas, the area on which the output image is displayed or the position of the separate displays can be optimally adapted to the desired coupling structure.

[0026] Smooth reflective surfaces, for example, can be used as sub-surfaces of the output structure. These surfaces are inclined relative to the inner and front surfaces in such a way that the beams of light guided through the optical fiber are coupled out through the rear surface. A smooth surface is defined as a continuously differentiable surface.

[0027] Alternatively, each sub-surface of the coupling structure can be a faceted reflective surface, wherein the faceted reflective surface comprises a smooth base surface and facets inclined relative to the smooth base surface.

[0028] The smooth surface or base can be a planar surface. However, it can also have an imaging function, for example, a light-collecting function. In this case, the smooth surface or base exhibits curvature. In the case of a faceted reflective surface, the curvature can be realized in the facets instead of the smooth base. The imaging function of the output coupling structure makes it possible to further reduce the space required by the beams in the direction of the optical fiber's thickness within the output coupling structure. The smooth surface or base can also be a freeform surface. A freeform surface, in this context, is understood to be a complex surface that can be represented, in particular, by domain-defined functions, especially twice continuously differentiable domain-defined functions. This is to be distinguished from simple surfaces, such as...spherical surfaces, aspherical surfaces, cylindrical surfaces, toric surfaces, etc.

[0029] In an advantageous further embodiment of the optical fiber according to the invention, it comprises, in addition to the output coupling structure, a further reflective element, which can in particular be designed as a smooth reflective surface or a faceted reflective surface. This further reflective element has an imaging function. It can in particular be realized by a freeform surface. In particular, if the output coupling structure also has an imaging function, no further imaging optical elements are necessarily required in addition to the output coupling structure and the further reflective element with the imaging function.

[0030] If the output coupling structure has an imaging structure and / or another reflective optical element with imaging function is present, an intermediate image can be generated in the optical fiber between the output coupling structure and the input coupling structure, which enables a further reduction in the space requirement of the beams transmitted by the optical fiber in the z-direction in the area of ​​the input coupling structure.

[0031] In the imaging device according to the invention, the image sensor sections can be offset from one another. The offset of the image sensor sections can be along the x-axis and / or along the y-axis. This provides a great deal of freedom in the arrangement of the image sensor sections, so that the arrangement of the image sensor sections can be adapted to the shape of the desired coupling structure and thus to the optical fiber.

[0032] The offset of the image sensor sections can be achieved by using a display large enough to show different output image field areas offset from one another. The image sensor sections are then defined by the sections of the display on which the respective output image field areas are shown. Alternatively, a separate display can be used for each output image field area, with the displays together forming the image sensor. In this case, the displays do not need to be larger than the output image field areas to be displayed, so the combined display area does not need to be larger than the area of ​​the output image to be displayed.The latter also makes it possible not only to optimize the position of the image sensor sections, but also to optimize the relative inclination between the image sensor sections, which can contribute to improving the correction of the image.

[0033] An HMD according to the invention is equipped with an imaging device according to the invention. In particular, the HMD according to the invention can be designed as glasses, thus constituting data glasses. The use of an imaging device according to the invention makes it possible to manufacture HMDs – and in particular data glasses – that can be designed compactly in the area of ​​the optical fiber coupling structure.

[0034] Further features, properties and advantages of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures. Figure 1 shows a schematic representation of an imaging device with a light guide according to the prior art. Figure 2 shows a schematic representation of a first embodiment of an imaging device with a light guide in which partial surfaces of the output coupling structure of the light guide are tilted relative to each other. Figure 3 shows a schematic representation of a second embodiment of an imaging device with a light guide in which partial surfaces of the output coupling structure of the light guide are tilted relative to each other. Figure 4 shows a possible arrangement of output image field areas of an output image on a display. Figure 5 shows the image generated by the imaging device based on the output image field areas of the output image. Figure 4generated virtual image. Figure 6 shows a possible alternative arrangement of output image field areas of an output image on a display. Figure 7 shows the virtual image generated by the imaging device based on the output image field areas of the output image. Figure 6 generated virtual image. Figure 8 shows a schematic representation of a third embodiment of an imaging device with a light guide in which partial surfaces of the light guide's output coupling structure are tilted relative to each other. Figure 9 shows a schematic representation of a fourth embodiment of an imaging device with a light guide in which partial surfaces of the light guide's output coupling structure are tilted relative to each other. Figure 10 shows an example of data glasses.

[0035] Before beginning to explain exemplary embodiments of the invention, reference will be made to Figure 1An imaging device with a light guide according to the prior art is described. The figure shows a schematic representation of an imaging device such as can be used in a head-mounted display (HMD), e.g., in smart glasses. The depicted imaging device comprises a light guide 1 with a back surface 3 and a front surface 5. When the imaging device is used in an HMD, the back surface faces the user's eye and the front surface 5 faces away from the eye. The light guide 1 also has a circumferential surface 7, of which an inclined section 9 serves as a coupling surface 9 (with or without imaging function) for beams of light emanating from an image sensor 11. The coupling surface 9 forms the coupling structure in this imaging device.The beams coupled into the optical fiber 1 are guided in the optical fiber 1 by means of total internal reflections at the rear surface 3 and the front surface 5 to an output coupling structure in the form of an inclined splitter mirror 13, from which they are coupled out of the optical fiber 1 through the rear surface 3 and superimposed on ambient light passing through the splitter mirror 13, so that a user of the HMD equipped with the imaging device perceives a virtual image of the original image floating in the environment.

[0036] The point behind the back surface 3 where all beams of light share a common cross-section is the exit pupil 17. The eyebox is generally of importance for head-mounted displays (HMDs). The eyebox is the three-dimensional area of ​​the beams within which the eye's pupil (not shown) can move without vignetting the image. Since the distance between the eye and the display is essentially constant with HMDs, the eyebox can be reduced to a two-dimensional one that only considers the eye's rotational movements. In this case, the eyebox essentially corresponds to the exit pupil of the display at the location of the eye's entrance pupil. The latter is usually defined by the eye's pupil. Therefore, only the exit pupil 17 is considered in this description.

[0037] As from Figure 1As can be seen, beams 4a, 4b, 4c emanating from different initial image field points 2a, 2b, 2c of the initial image reach the exit pupil 17 at different angles, with the beams 4a, 4c emanating from the outermost field points 2a, 2c forming the edge of the total beam array in the region of the exit pupil 17. The angle α between the beams 4a, 4c emanating from the outermost field points 2a, 2c represents the field angle of the initial image, which is shown in the representation. Figure 1 a horizontal field angle.

[0038] For the following considerations, it is expedient to view the beam path backwards, i.e., starting from the exit pupil 17 through the optical fiber 1 to the image sensor 11. The totality of the beam bundles emanating from the exit pupil 17 has a field angle range in which all beam bundles are located. The respective angles of the individual beam bundles relative to the optical axis characterize the field point at which they ultimately strike the initial image displayed on the image sensor 11. As can be seen from Figure 1 As can be seen, there is a situation for the in Figure 1The problem with the beam 4c emanating from the exit pupil 17 downwards and to the right is that, after multiple reflections in the optical fiber 1, it does not exit through the side surface 9 of the optical fiber 1, but rather through its front surface 5. This is because the field angle α leads to a large widening of the total beams the further the beams move away from the exit pupil 17. This results in the following: Figure 1 The coupling surface 9 shown does not allow all beams of light to pass through this coupling surface 9 and the imaging optics 15. The beams exiting through the front surface 5 therefore cannot contribute to the imaging process. This non-imaging, i.e., blocked, area is shown in Figure 1marked by a double arrow 19. The blocking has the effect that only the output image field area 21 in the output image displayed on the image transmitter 11 can contribute to the generation of a virtual image. The output image fields to be displayed are therefore in the Figure 1The configuration shown is subject to severe limitations. If these limitations are circumvented by coupling via the rear surface 3 or the front surface 5 instead of a side surface, the resulting large expansion of the total beam bundle necessitates large coupling structures and imaging optics. Furthermore, the coupling and output structures in this case will be diffraction gratings or Fresnel structures, which have a strong deflecting effect to generate the necessary total internal reflection. At large field angles and / or a large eyebox, portions of the beams transmitted by the optical fiber 1 would be deflected by the diffraction grating or Fresnel structure forming the output coupling structure.The light beam is deflected by the Fresnel structure forming the output coupling structure, such that instead of being coupled out, it is reflected back from an air-adjacent interface of the optical fiber 1 onto the output coupling structure and strikes it a second time. Such portions of the beam are unusable for imaging and lead to a reduction in the image field and / or pupil size. This effect is also known as "footprint overlap".

[0039] A first embodiment of an imaging device in which the with reference to Figure 1 The described problem is reduced, as will be discussed below with reference to Figure 2 described.

[0040] The figure shows an optical fiber 1 with a back surface 3 and a front surface 5, as well as a circumferential surface 7. In the present embodiment, one side surface of the circumferential surface 7 serves as the coupling surface 9 and thus as the coupling structure of the optical fiber 1. Furthermore, the optical fiber 1 comprises an output coupling structure 13, which in the present embodiment is formed by two planar output coupling mirrors 131 and 132, tilted relative to each other and configured as beam splitters. In the present embodiment, the output coupling mirrors 131 and 132 are structures embedded in the optical fiber 1. These can be produced, for example, by grinding the optical fiber 1 in the region of the side surface opposite the coupling surface 9 so that the mirror surfaces 131 and 132 are formed.These are then partially mirrored, and finally a wedge-shaped attachment is applied to the partially mirrored surfaces to restore the original shape of the optical fiber 1. As in the optical fiber from . Figure 1 The beams are guided from the coupling surface 9 to the coupling structure by total reflection at the rear surface 3 and the front surface 5.

[0041] In addition to the light guide 1, it shows Figure 2 also an image sensor 11, an imaging optic 15 and the exit pupil 17 of the imaging device.

[0042] The Figure 2 It also shows a coordinate system whose x-axis runs into the plane of the leaf. The y-axis points upwards in the plane of the leaf, and the z-axis points to the right in the plane of the leaf. As in Figure 2As can be seen, the dividing mirror 13 2 is tilted relative to the dividing mirror 13 1 about the x-axis and about the y-axis. The two dividing mirrors 13 1 , 13 2 thus form tilted partial surfaces of the output coupling structure 13.

[0043] To explain the initial effects of tilting the dividing mirror 13 2 relative to the dividing mirror 13 1 about the x-axis and the associated design of the output coupling structure 13 with two mutually tilted sub-surfaces, the following is described with reference to Figure 1The beams emanating from the exit pupil 17 towards the image sensor 11 are again examined. By tilting the second beam splitter 13 2 relative to the first mirror 13 1 about the x-axis, the beams of the optical fiber 1 reflected by it are shifted parallel to the yz-plane compared to the beams reflected by the beam splitter 13 1. This results in a reduction in the cross-sectional area occupied by the beams in the z-direction when considering the beams emanating from the exit pupil 17 at the field angle α in the region of the coupling surface 9. More precisely, the projection of the cross-sectional area occupied by the beams in the region of the coupling structure 9 onto the xz-plane has a smaller extent in the z-direction than is the case for the optical fiber. Figure 1(which has no mutually tilted sub-areas of the output coupling structure 13) is the case. In other words, the beams move closer together in the region of the input surface 9. This allows, in comparison to the imaging device made of Figure 1 When the beams are coupled through the coupling surface 9 arranged in the circumferential surface 7, either a larger field angle α is transmitted by the optical fiber 1 or, with the same transmitted field angle, the thickness of the optical fiber 1 is reduced.

[0044] Due to the rotation about the y-axis, beams of light emanating from the exit pupil 17 are guided through different superimposed regions of the optical fiber 1, depending on which mirror 131, 132 they are reflected from. This causes the beams of light reflected by the two mirrors 131, 132 to diverge in the x-direction within the optical fiber when projected onto the xy-plane. They are then deflected by superimposed regions of the coupling mirror 25 through the rear surface 3 towards superimposed imaging optics 151, 152. Passing through the imaging optics 151, 152, they finally reach image sensors 111, 112, which are also superimposed in the x-direction.This makes it possible to distribute the initial image onto two image transmitters 11 1 that are superimposed in the x-direction, whereby horizontally adjacent field areas in the virtual image can be vertically superimposed initial image field areas in the original image.

[0045] Due to the rotation of the two mirror surfaces relative to each other around both the x-axis and the y-axis, the cross-sectional area occupied by the beams located in the region of the coupling structure 25 can be reduced along the z-direction and simultaneously increased in the x-direction when projected onto the xz-plane. This also allows for the displacement of beams from the z-direction to the x-direction. The resulting flexibility in the distribution of image sensor sections of the image sensor 11 enables the transmission of particularly large horizontal field angles α, which in particular also facilitates the transmission of 16:9 formats. The spacing and respective beam angles of the image sensor sections of the image sensor 11 can be optimally adapted to the path of the beams in the optical fiber.

[0046] A second embodiment of an optical fiber according to the invention is described below with reference to Figure 3 As described above, this figure also shows an optical fiber 1 with an inner surface 3, a front surface 5, and a circumferential surface 7, where, however, the coupling of the beams into the optical fiber 1 occurs through the rear surface 3. A reflective coupling surface 25 is formed in the circumferential surface 7, over which the beams entering the optical fiber 25 through the rear surface 3 are deflected such that they are guided by total internal reflection between the rear surface 3 and the front surface 5 to an output coupling structure 13. From this output coupling structure 13, the beams are finally coupled out of the optical fiber 1 through the rear surface 3 towards the exit pupil 17.

[0047] As in the first embodiment, the output coupling structure 13 comprises two mirror sections 13 1 and 13 2, whose reflective surfaces are oriented around the x-axis running into the plane of the sheet and around the Figure 3 The y-axes running upwards in the plane of the sheet are rotated relative to each other. As in Figure 3 As can be seen, in the present embodiment, the image sensor sections are implemented by separate image sensors 111, 112 and are inclined differently relative to the xy-plane. Adjusting the inclination relative to the xy-plane and selecting the distance between the two image sensors 111, 112 in the x-direction serves, in the present embodiment, to optimize the image correction.

[0048] Although in Figure 3If two separate image sensors 11 1 , 11 2 are used, it is also possible to display the initial image field areas on image sensor sections 11 1 , 11 2 of a single image sensor 11, which has a correspondingly large extent, particularly in the x-direction. Such an image sensor 11 is in Figure 4 The image sensor sections 111, 112 representing the output image field areas 121, 122 are arranged offset along the x-direction. The arrangement of the output image field areas 121, 122 in the virtual image generated by the imaging device is shown in Figure 5As shown, when using a single large image sensor 11, the degrees of freedom for optimizing the image correction are reduced. The only remaining possibility is to optimize the distance between the image sensor sections 111, 112, which represent the output image field areas 121, 122, in the x-direction, provided the image sensor 11 has the corresponding x-direction extent. Different tilting of the image sensor sections 111, 112 relative to the xz-plane is not possible with a single large image sensor 11. It should be noted that the image sensor sections 111, 112 can also represent overlapping output image field areas 121, 122. An alternative arrangement of the image sensor sections 11 1 , 11 2 , in which the image sensor sections 11 1 , 11 2 are offset in the y-direction, is shown in Figure 6 shown, the resulting image in Figure 7 .

[0049] In the first two embodiments, the output structure had no imaging function whatsoever. If the output structure is equipped with an imaging function, it is possible to further reduce the space required for the beams in the z-direction. An embodiment in which the output structure 13 has an imaging function is shown in Figure 8 As shown. In this embodiment, the dividing mirrors 131, 132, which form the partial surfaces of the output coupling structure 13, are tilted about both the x-axis and the y-axis, and the image sensors 111, 112 are arranged offset from each other along the x-direction. Compared to the previous embodiments, the imaging device from Figure 8However, there is no imaging optic 15 or 151, 152 outside the light guide 1. Instead, the partially transparent coupling mirror 25 of the light guide, the beam splitter mirrors 131, 132, and a further reflective element in the form of a beam splitter mirror 27 each have an imaging function. The additional beam splitter mirror 27 is arranged on the front surface 5 of the light guide 1. In combination, the imaging functions of these elements replace the imaging optics of the preceding embodiments.

[0050] In the present embodiment, the beam splitters 131, 132, the partially transparent coupling mirror 25, and the further beam splitter 27 used for coupling each have a focusing function, so that the beams emanating from the image sensors 111, 112 are collimated as a whole and are present as collimated beams at the exit pupil 17. However, it is also possible to design the individual mirrors such that their focusing effect is insufficient to generate parallel beams, resulting in slightly divergent beams at the exit pupil 17. This leads to the virtual image not being perceived at infinity, but at a finite distance. Furthermore, if the curvatures of the mirrors comprise a basic curvature and a superimposed freeform curvature, it is possible to optimize the correction of image aberrations.

[0051] Another embodiment of the imaging device is shown in Figure 9 The optical fiber 1 of this imaging device differs from the optical fiber of the one shown in Figure 8The imaging device shown is achieved primarily by the fact that the curvature of the beam splitter mirrors 131, 132, and the additional beam splitter mirror 27 forming the output coupling structure 13 is essentially designed such that an intermediate image 29 is generated in the optical fiber 1 in a plane perpendicular to the yz-plane and not parallel to the xy-plane. This measure allows for a further reduction in the space required for the beams in the z-direction in the region of the partially transparent input coupling mirror 25, which further increases the transmittable field angle α and thus the fields of view to be displayed, and simplifies the guidance of the beams through the optical fiber 1. For the reduction in the space required for the beams in the z-direction, it is sufficient if an intermediate image is present in the plane perpendicular to the yz-plane along a direction perpendicular to the x-direction, but not along a direction parallel to the x-direction.

[0052] In all embodiments, the optical fiber, together with the image sensor(s) and, optionally, an imaging optic arranged between the image sensor(s) and the optical fiber, forms an imaging device for generating a virtual image based on a source image displayed on the image sensor(s). In the case of multiple image sensors, the source image sections displayed on the respective image sensors represent different source image field areas of the source image. Such an imaging device can be used, in particular, in a head-mounted display (HMD). An example of an HMD is shown in Figure 10 A data glasses 201 was shown, i.e. an HMD, which is designed in the form of glasses that allow the simultaneous viewing of a virtual image and the surroundings.

[0053] The in Figure 10The illustrated data glasses 201 comprise a spectacle frame 207 with temples 211 and spectacle lenses 203 embedded in the spectacle frame 207. The spectacle lenses 203 are designed as light guides according to the invention, each of which is arranged together with an image transmitter in the corresponding temple 211 (in Figure 10 (not shown) form an imaging device designed according to one of the preceding embodiments. The spectacle lenses 203 can include coupling in and out structures and, optionally, a further structure with imaging properties, as described with reference to the Figures 6 and 7 as described, or imaging optics are present between the spectacle lenses 203 and the image transmitters arranged in the temples 211, as described in the reference to the Figures 2 and 3This is the case in the described embodiments. In the present embodiment, the coupling of the beams into the lenses 203 occurs via those side surfaces of the lenses 203 that adjoin the respective temples 211. However, it is also possible, in the illustrated data glasses 201, to couple the beams for imaging into the lenses 203 via the back surface of the lenses.

[0054] Although in Figure 10While a pair of smart glasses is shown as an example of a head-mounted display (HMD), it is understood that other embodiments of an HMD can also be equipped with a light guide according to the invention. If the HMD is to be suitable for displaying three-dimensional images, a light guide according to the invention and a display associated with the light guide are provided for each eye. If a three-dimensional display is not required, it is sufficient to design one of the two lenses 203 as a light guide according to the invention and to associate a display and, if necessary, imaging optics arranged between the display and the lens with it.

[0055] The invention, presented with reference to exemplary embodiments, makes it possible to reduce the extent of all the beams located in the area of ​​the coupling structure when projected onto the xz-plane. Since, for example, the thickness of the lens in a pair of smart glasses extends essentially along the z-direction, this direction represents a critical plane for the extent of all the beams. The presented invention also makes it possible to distribute the output image field to be displayed in the optical fiber across two or more sections along the x-direction and to transport it through these different sections from the respective image sensors to the output coupling structure. As a further degree of freedom for image correction, it proves advantageous if the image sensors are each positioned at a distance and angle relative to the respective output image field area they represent.

[0056] To achieve the greatest advantage regarding the transmission of large source image fields, a combination of the design of the output coupling structure with two mutually tilted sub-surfaces and the described aspects of intermediate image generation is advantageous. In this case, these two sub-surfaces are imaging surfaces, in particular collecting surfaces, and each has a shape optimized for the source image field area transmitted by them. The focal lengths of the two sub-surfaces are chosen to be sufficiently short so that the exit pupil is imaged close to the input coupling structure and, preferably, an intermediate image is simultaneously generated in the optical fiber. However, even if the sub-surfaces of the output coupling structure are not designed for imaging but merely consist of mutually tilted planar surfaces, a significant reduction in the space required for the beams in the z-direction is already achieved in the area of ​​the input coupling structure.

[0057] The present invention has been described in detail with reference to exemplary embodiments for illustrative purposes. However, a person skilled in the art will recognize that deviations from these exemplary embodiments are possible, provided they do not exceed the scope of protection defined in the appended claims. For example, the output structure may have more than two tilted sub-surfaces. Likewise, more than two image sensors may be present. Furthermore, in addition to the offset in the x-direction, the image sensors may also have an offset in a direction perpendicular to the x-direction, whereby a suitable offset in this direction is limited by the thickness of the optical fiber, i.e., the distance between its back surface and its front surface. Finally, it is possible to provide faceted mirror surfaces instead of smooth, i.e., continuously differentiable, mirror surfaces.These facets then exhibit an inclination relative to a typically smooth base surface. This design makes it possible to arrange the base surfaces parallel to the front or back surface of the optical fiber. However, the facets of one sub-surface are tilted relative to the facets of the other sub-surface. Furthermore, the imaging effect of the coupling structure can be achieved not only by a correspondingly curved reflective surface, but also by a curvature of a side surface serving as the coupling structure, through which the beams pass when coupled into the optical fiber, so that the side surface forms a refractive imaging element.

Claims

1. Imaging apparatus for generating a virtual image, having an image generator (11) having at least two image generator sections (111, 112) for representing at least two initial image field regions (121, 122) of an initial image and having a light guide (1), wherein the light guide (1) comprises: - an input coupling structure (9, 25) for coupling beams coming from the initial image into the light guide (1), and - an extensive output coupling structure (13) for coupling the beams that were coupled into the light guide (1) out of the light guide (1), wherein the extensive output coupling structure (13) comprises at least two partial faces (131, 132) and wherein each partial face (131, 132) is assigned to a different one of the initial image field regions (121, 122) and couples out the beams coming from the corresponding initial image field region (121, 122), - wherein the partial faces (131, 132) of the output coupling structure (13) are tilted with respect to one another, characterized in that the partial faces (131, 132) of the output coupling structure (13) are tilted about two non-parallel axes (x, y) such that initial image field regions (121, 122) vertically superimposed in the initial image generate horizontally adjacent field regions in the virtual image or initial image field regions (121, 122) horizontally adjacent in the initial image generate vertically superimposed field regions in the virtual image.

2. Imaging apparatus according to Claim 1, characterized in that the axes (x, y) about which the output coupling faces (131, 132) are tilted with respect to one another are perpendicular to the output coupling direction (z).

3. Imaging apparatus according to Claim 1 or Claim 2, characterized in that each partial face (131, 132) of the output coupling structure (13) is a reflective face.

4. Imaging apparatus according to any of Claims 1 to 3, characterized in that every partial face (131, 132) of the output coupling structure (13) is a faceted reflective face having a smooth base face and facets that are inclined with respect to the base face, wherein the facets of the two partial faces (131, 132) are tilted with respect to one another.

5. Imaging apparatus according to any of Claims 1 to 4, characterized in that the output coupling structure (13) has an imaging function.

6. Imaging apparatus according to Claim 5, characterized in that the output coupling structure (13) has a light-converging function.

7. Imaging apparatus according to Claim 5 or Claim 6, characterized in that, in addition to the output coupling structure (13), it comprises a further reflective element (27), wherein the further reflective element has an imaging function.

8. Imaging apparatus according to any of Claims 5 to 7, characterized in that an intermediate image (29) is generated in the light guide (1) between the input coupling structure (9, 25) and the output coupling structure (13).

9. Imaging apparatus according to any of Claims 1 to 8, characterized in that it has a rear face (3), which is to face the eye of a user, a front face (5), which is to face away from the eye of the user, and a perimeter face (7) connecting the rear face (3) to the front face (5), wherein the input coupling structure (9) is arranged in the light guide such that the beams can be coupled in via the perimeter face (7).

10. Imaging apparatus according to any of Claims 1 to 9, characterized in that the image generator sections (111, 112) are offset with respect to one another.

11. Imaging apparatus according to any of Claims 1 to 10, characterized in that the image generator sections (111, 112) are formed by mutually separate displays.

12. HMD having an imaging apparatus according to any of Claims 1 to 11.

13. HMD according to Claim 12, which is designed as smartglasses (201).