Optical system for generating a virtual image and method for producing an output coupling arrangement of an optical system

Abstract

An optical system for generating a virtual image of a source image provided on an imager, comprising at least one light guide to be worn in front of an eye, an input coupling arrangement for coupling a beam path from the source image into the light guide, and an output coupling arrangement for coupling the beam path out of the light guide towards the eye. The input coupling arrangement couples the beam path into the light guide in such a way that the beam path propagates within the light guide to the output coupling arrangement by reflection at the inner surface and / or the outer surface of the light guide. The output coupling arrangement has a region that is impinged upon by the beam path propagating in the light guide to the output coupling arrangement. The surface of the output coupling arrangement is treated such that the beam path is output-coupled from the light guide towards the eye via a first part of the region of the output coupling arrangement, while in a second part thereof, the beam path is output-coupled from the light guide towards the eye at most with a reduced intensity or not at all.

Description

Field of the Invention

[0001] The present invention relates to an optical system for generating a virtual image of a source image provided on an imager.

[0002] Furthermore, the present invention relates to a method for producing an output coupling arrangement for such an optical system. Background Art

[0003] An optical system of the type set forth at the beginning is known from the document WO 2016 / 102190 A1.

[0004] An optical system of the type set forth at the beginning can be used in a so-called head-mounted display (HMD), i.e., a display device worn on the head. A conventional form of HMD uses a screen that is worn in front of the eyes and presents computer-generated images or images taken by a camera to the user. Such an HMD is typically bulky and does not allow direct perception of the surrounding environment. In recent years, HMDs have been developed that can present images recorded by a camera or computer-generated images to the user without obstructing direct perception of the surrounding environment. Such HMDs (also referred to as smart glasses) allow this technology to be used in daily life.

[0005] The optical system of such smart glasses typically has an imager, an input coupling element, an optical waveguide, and an output coupling element. The input coupling of light from the source image into the optical waveguide and the output coupling of the light propagating in the optical waveguide from the optical waveguide can be achieved using different means, such as based on reflection, refraction, diffraction, holography, etc. or combinations thereof. Smart glasses are characterized by high requirements for imaging quality, while having a relatively large imaging ratio. At the same time, in the case of such a head-mounted system, emphasis is placed on low weight and compactness (small installation space), requiring the use of as few optical surfaces as possible to image the source image to generate a virtual image. However, as a result, only a few surfaces are then available for compensating optical aberrations. Equally important is that perfect vision obtained through smart glasses (the so-called see-through function) is one of the important criteria determining the acceptance and success of HMD products.

[0006] In the case of an optical system, where the output coupling of light propagating in an optical waveguide is achieved by reflection at a free-form Fresnel surface having one (e.g., a free-form mirror) or multiple segments, as described in the documents set forth at the beginning, due to the relative positions of the output coupling arrangement close to the exit pupil of the optical system and close to the pupil of the user's eye, the optical imaging quality depends to a large extent on the trueness and quality of the surface of the output coupling arrangement. Local shape deviations of the individual Fresnel segments result in a significant reduction in optical performance, manifested as contrast loss, double images (ghost images), and other imaging aberrations. In addition, connection conditions are applied between the individual segments of the Fresnel surface, which should be understood as continuously extendable patches of a free-form surface, and these connection conditions require that the tolerances of the individual Fresnel segments with respect to shape deviations and with respect to their mutual relative positions (i.e., positions relative to each other) be in the sub-micron range (<< 1 µm), such that acceptable imaging quality can be obtained. In practice, especially when manufacturing plastic parts, due to the properties of plastics (such as thermal expansion, compressibility, internal stress, surface adhesion, etc.) and the manufacturing techniques and processes used (such as injection molding, injection compression molding, etc.), it is found to be very difficult and complex to maintain a very small tolerance range in terms of the shape trueness and mutual alignment of the Fresnel segments. Maintaining a very small tolerance range directly affects the yield of high-quality parts and poses significant challenges both technically and from a process perspective.

[0007] In order to ensure the aforementioned perspective function (transparency) of the optical waveguide in the region of the output coupling arrangement, it is advantageous to provide the output coupling arrangement with a partially transparent layer that reflects some of the luminous intensity of the light beam path from the imager, but which has the property of being as transparent as possible in the viewing direction passing through it, and thus represents a compromise between the best possible transparency and the maximum intensity of the light output-coupled towards the user's eye. In addition, the output coupling arrangement is typically applied to a second housing. The second housing can be matched to the shape of the output coupling arrangement in the region of the output coupling arrangement. The housing is adhered to the optical waveguide by means of an adhesive or in any other way. In the case where no housing is used, the grooves of the output coupling arrangement can also be filled with another transparent substance, such as an adhesive. The surface of the housing facing the adhesive inherently or after appropriate treatment has anti-adhesive properties, and the housing can be used only during the curing process for shaping and can then be removed.

[0008] Another problem with using a partially transparent layer, which is decisive for the perspective function, is that light partially transmitted through a Fresnel section impinges on the shadow region of a subsequent Fresnel section and reaches the observer's eye after single or multiple reflections. Here, if the output coupling arrangement has a free-form Fresnel surface, the continuity condition is usually violated. Since the focus in designing the Fresnel surface is on optimizing the reflection regions of the Fresnel sections, imaging aberrations occur during passage through the Fresnel edge and in the shadow regions of the Fresnel sections where the light beam path is reflected. Deviations from the target geometry due to manufacturing processes, such as rounding of sections due to the radius of the diamond tool during ultra-precision machining, further amplify this effect. The resulting light components reach the user's eye, causing contrast loss, double images, trailing of the perceived image, and other unwanted effects, which overall have a negative impact on the imaging quality of the optical system.

[0009] JP 2016-110080 A also discloses an optical system. The output coupling arrangement has a plurality of regions inclined with respect to each other, and the regions of the plurality of regions directly impinged on by the light rays propagating in the optical waveguide are partially provided with a reflective layer. Summary of the Invention

[0010] Therefore, the present invention is based on the following object: to develop an optical system of the type described at the beginning to improve its imaging quality.

[0011] Furthermore, the present invention is based on the following object: to provide a method for producing an improved output coupling arrangement.

[0012] According to the present invention, with respect to the optical system described at the beginning, this object is achieved in that the regions of the output coupling arrangement impinged on by the light beam path have been surface-treated in such a way that the light beam path is output-coupled from the light guide to the eye via a first part of the region of the output coupling arrangement pre-defined for imaging the source image, while the light beam path is not output-coupled or at most output-coupled with a reduced intensity from the light guide in a second part of the region of the output coupling arrangement different from the first part.

[0013] The optical system according to the invention deviates from the concept of providing partial specular reflection over the entire area arranged for the output coupling such that the entire area of the output coupling arrangement struck by the beam path couples the beam path out of the light guide into the eye. In contrast, in the system according to the invention, the beam path is taken only from parts of the area of the output coupling arrangement struck by the beam path, which parts are selected purposefully with the aim of coupling the beam path out into the user's eye. To this end, the area of the output coupling arrangement struck by the beam path has been surface-treated in such a way that the beam path is coupled out of the light guide into the eye only via a predefined first part of the area of the output coupling arrangement, while the beam path is not coupled out of the light guide or is coupled out at most with a reduced intensity in a second part of the area struck by the beam path. Here, the reduced intensity should be understood as being relative to the intensity of the beam path coupled out in the first part, and thus, the low-intensity coupling out in the second part does not significantly impair the quality of the virtual image generated therein. The first part of the area of the output coupling arrangement is selected or determined in view of the best imaging quality of the optical system.

[0014] In particular, the first part is the part of the area of the output coupling arrangement that meets the defined minimum requirements in terms of surface quality, degree of trimming of the shape, and other parameters related to the imaging quality. The first part can be confirmed by suitable measurement methods. For example, suitable measurement methods include conventional methods for tactile and non-contact shape measurement, such as profilometry, white light interferometry, chromatic confocal measurement methods.

[0015] By using the optical system according to the invention, the contrast loss, double images, trailing of the perceived image, and other unwanted effects (which do not actually contribute to imaging) of the light from the source image entering the user's eye are avoided or at least reduced.

[0016] The first part of the area of the output coupling arrangement struck by the beam path can be surface-treated by means of a reflective layer provided, which first parts are for coupling the beam path out of the light guide. In this context, the reflective layer should also be understood to mean a partially reflective layer. Thus, the reflectivity of the reflective layer can be in the range of 1% to 100%. Moreover, the reflective layer should also be understood to mean a layer composed of a plurality of individual layers. According to the invention, in the case of an output coupling arrangement consisting of a plurality of output coupling areas, the surface treatment of the individual output coupling areas can be different. This also applies to parts of different output coupling areas and parts of the same output coupling area. In particular, the first part can be surface-treated with a reflective layer having a reflectivity difference of at least 0.1%.

[0017] In contrast to conventional systems, the reflective layer is not applied to the entire area of the output coupling arrangement, but only in a selected part (first part) of this area.

[0018] Accordingly, the second part without the reflective layer does not contribute or only contributes to a reduced extent to the output coupling of the light beam path from the light guide. In addition, as a result of the coating being carried out only in the first part of the area of the output coupling arrangement, the transparency (perspective function) of the light guide is increased in the area of the output coupling arrangement since the uncoated second part has the maximum possible transmission. Since the area of the output coupling arrangement is not provided with a reflective layer everywhere, the intensity of the light beam path coupled out from the light guide is reduced, which can be achieved by increasing the luminosity of the imager or by coating the first part with a higher reflectivity.

[0019] As an alternative or addition to the surface treatment of the first part with the reflective layer, the second part of the area of the output coupling arrangement can be surface-coated with a layer that is transparent in the visible spectrum and ideally has a refractive index match, through which the light beam path should either not be output-coupled from the light guide or at most be output-coupled to the user's eye with a reduced intensity, wherein the refractive index matching layer in the second part at least reduces the reflection of the light beam path to the user's eye and / or causes the light beam path to be output-coupled from the light guide in a direction away from the eye.

[0020] This measure also advantageously contributes to improving the imaging quality of the optical system, in that those parts of the area of the output coupling arrangement that would cause a loss of contrast, double images or any other deterioration in the imaging quality if the light beam path is output-coupled from the light guide to the user's eye have a reduced reflectivity relative to the first part due to the refractive index matching layer and / or promote an increased transmission of the light beam path for output-coupling the light beam path only in a direction away from the user.

[0021] The refractive index matching layer is preferably highly transparent in the visible spectrum. The refractive index is matched to the material of the light guide and / or the output coupling arrangement in such a way that the refractive index jump (which causes reflection) is as small as possible in the second part of the area of the output coupling arrangement.

[0022] The refractive index matching layer should also be understood to mean a layer that is formed, for example, by filling grooves with a refractive index-matching material in the case of a surface with a Fresnel section.

[0023] The output coupling arrangement can have an area with one or more Fresnel sections. In particular, the Fresnel surface can be a free-form Fresnel surface with one or more sections.

[0024] In the case of an output coupling arrangement configured with a plurality of Fresnel segments, a first part of the area of the output coupling arrangement is in each case an area located outside the shadow cast by adjacent Fresnel segments, and these first parts are intended to output-couple the beam path into the user's eye as required.

[0025] As already described at the beginning, imaging aberrations can occur when the beam path passes through the Fresnel edge and light penetrates the shadow area of the Fresnel segment. However, as provided by the above measurements, if the areas of the long edges of the Fresnel segments that are located outside the respective projected shadows are at least partially selected as the first parts such that the beam path is output-coupled from the light guide only in the first parts, then the components of the beam path that reach the shadow area of the Fresnel segment no longer cause imaging aberrations because these components are not output-coupled from the light guide or are output-coupled at most with a reduced intensity.

[0026] A second part (where the output coupling of the beam path from the light guide in the direction towards the user's eye is reduced or suppressed) can in each case be an area of the Fresnel segment that is located within the shadow cast by adjacent Fresnel segments, and / or can generally be an area that is not suitable for output-coupling the beam path into the user's eye because it does not meet the requirements for optimal imaging quality.

[0027] Furthermore, according to the invention, there is provided a method for producing an output coupling arrangement for an optical system according to the invention, for example. According to the invention, the method comprises:

[0028] Determining a first part of the area of the output coupling arrangement that is suitable for output-coupling the beam path that travels from a source image and in the light guide towards the user's eye for the purpose of imaging the source image,

[0029] Surface-treating the area of the output coupling arrangement in such a way that the beam path is output-coupled from the light guide via these first parts to the user's eye, while the beam path is not output-coupled from the light guide or is output-coupled at most with a reduced intensity to the eye in a second part of the area of the output coupling arrangement that is different from these first parts.

[0030] The first parts can be determined using suitable optical measurement methods, as specified above by way of example.

[0031] The method according to the invention has the same advantages as those described with respect to the optical system according to the invention.

[0032] In a preferred configuration, the surface treatment of the area of the output coupling arrangement can include applying a reflective layer to the first parts.

[0033] Advantageously, in this case the surface treatment can be carried out by means of a mask which masks the part of the area of the output coupling arrangement which should not be coated when applying the reflective layer. After determining the first part, such a coating mask can be manufactured, for example, by means of a laser cutting method, an etching method or any other method. The mask advantageously ensures that the reflective coating is applied only to the desired first part of the area of the output coupling arrangement.

[0034] As an alternative or addition thereto, the surface treatment of the area of the output coupling arrangement can include applying a refractive index matching layer on the second part.

[0035] Other advantages and features will be apparent from the following description and the drawings.

[0036] It goes without saying that the above features and the features to be explained below can be used not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the invention. Description of the Drawings

[0037] Exemplary embodiments of the invention are shown in the drawings and are described in more detail below with reference to these drawings. Specifically:

[0038] Figure 1 A top view of an exemplary embodiment of an optical system for generating a virtual image is shown;

[0039] Figure 1A A plan view of the entire area of the output coupling arrangement is shown, wherewith respect to Figure 1 a magnified scale;

[0040] Figure 2 A part of the optical system is shown to explain how stray light is generated in the area of the output coupling arrangement in the system;

[0041] Figure 3 A part of an optical system for generating a virtual image according to the principles of the invention is shown;

[0042] Figures 4 to 7 An example of the area of the output coupling arrangement which has been surface-treated in the area is shown; and

[0043] Figure 8 A flow chart of a method for producing an output coupling arrangement for an optical system for generating a virtual image is shown. Detailed Description

[0044] Figure 1An optical system provided with the general reference numeral 10 is shown for generating a virtual image of a source image provided on an imager 12. The optical system 10 can be an optical system of a head-mounted display (HMD), more specifically, smart glasses. In particular, the optical system 10 is capable of presenting the source image, which can be an image recorded by a camera or a computer-generated image, provided by the imager 12 to a user without obstructing the direct perception of the surrounding environment. This means that the optical system 10 allows the user to look through the optical system (so-called see-through function) simultaneously as in the case of conventional glasses. Such a system is also referred to as augmented reality glasses or virtual reality glasses.

[0045] The optical system 10 includes at least one light guide 16 to be worn in front of the user's eyes 14. The light guide 16 can be implemented as a spectacle lens or can be integrated in a spectacle lens. Figure 1 Only one light guide 16 is shown, where the system 10 can have a second light guide (not shown) to be worn in front of the user's other eye. It should also be understood that the light guide 16 can be composed of a stacked arrangement of multiple light guides, as may be the case in such a system, in order to use a corresponding light guide as a transmission channel for a corresponding spectral range, for example.

[0046] The light guide 16 has an inner surface 18 facing the eyes 14 and an outer surface 20 facing away from the eyes. The light guide 16 is transparent to visible light so that the user can look through the light guide 16 in the direction of the visual axis 22.

[0047] The optical system 10 further includes an input coupling arrangement 24 for input-coupling a beam path 26 emitted from the source image of the imager 12 into the light guide 16, between the inner surface 18 and the outer surface 20. The input coupling arrangement 24 and the light guide 16 can have an integral implementation, that is, there is no interface, and thus there is no air gap between the input coupling arrangement 24 and the light guide 16. In addition to input-coupling the beam path 26 emitted from the imager 12 into the light guide 16, the input coupling arrangement 24 is also used to collimate the divergent beam path 26 emitted from the imager 12.

[0048] In the light guide 16, the beam path 26 that has been coupled into the light guide 16 via the input coupling arrangement 24 propagates by reflection at the inner surface 18 and the outer surface 20. In this case, the reflection of the beam path 26 is based on total internal reflection of the beam path 26 at the inner surface 18 and the outer surface 20 of the light guide 16. The beam path 16 undergoes one or more reflections at the inner surface 18 and / or the outer surface 20 in the light guide 16 (for simplicity, Figure 1After only a single reflection at the inner surface 18), it propagates to the output coupling arrangement 28. The function of the output coupling arrangement 28 is to output-couple the beam path 26 from the light guide 16 to the user's eye 14, with the result that the user can perceive the virtual image of the source image imaged by the system 10.

[0049] Due to the relative positions of the output coupling arrangement 28 close to the exit pupil of the optical system and the pupil 14 of the eye, the optical imaging quality of the generated virtual image depends to a large extent on the surface finish and surface quality of the output coupling arrangement 28.

[0050] In the exemplary embodiment shown, the output coupling arrangement 28 is implemented as a freeform Fresnel surface with a plurality of Fresnel segments 28a, which have a sawtooth implementation. Figure 1 Seven segments are shown by way of example. The Fresnel segments are oriented in such a way that the zero ray of the beam path 26 incident on the respective Fresnel segment (facet) 28a is reflected in the direction of the inner surface 18 of the light guide 16 and enters the user's eye 14 from this inner surface. The light beam incident on the output coupling arrangement 28 through the outer surface 20 from the surrounding environment is transmitted by the output coupling arrangement to the greatest possible extent, so that the user of the optical system 10 thus has the impression that the virtual image generated according to the source image of the imager 12 floats in the surrounding environment.

[0051] Figure 1A A plan view of the entire area 29 of the output coupling arrangement 28 is shown separately and with an enlarged scale relative to Figure 1 In the example shown, the output coupling arrangement 28 has seven Fresnel segments 28a - 28g. The Fresnel segments 28a - 28g form the area 29 of the output coupling arrangement 28, which is struck by the beam path 26 propagating from the input coupling arrangement 24 to the output coupling arrangement 28 in the light guide 16. In the case of a conventional optical system, the entire area 29 (as Figure 1A shown) is used, for example, to output-couple the beam path 26 into the user's eye 14. However, this has disadvantages in terms of the imaging quality of the optical system 10, manifested as contrast loss, generation of double images (ghost images), and other aberrations. This is explained below with reference to Figure 2 by way of example. In special cases, the area 29 of the output coupling arrangement 28 can consist of a single Fresnel segment.

[0052] Figure 2 A part of the light guide 16 in the area of the output coupling arrangement 28 is shown, showing two successive Fresnel segments 28 i and 28 i+1 . In addition, Figure 2Shows the beam path 26 propagating in the light guide 16. The beam of the beam path 26 (designated by 26a) passes through the Fresnel section 28 i , strikes the long edge 34 of the Fresnel section 28 i+1 and is partially reflected from this long edge due to the partial transparency of the output coupling arrangement 28 (as shown by the beam 26b), and partially enters the Fresnel section 28 i+1 (as shown by the beam 26c). Thus, the beam 26b is output-coupled from the light guide 16 in the direction of the user's eye (not shown here) through the Fresnel section 28 i+1 . The beam 26b is the target beam, which is required and used to image the source image, with the aim of generating a virtual image in the user's eye. Figure 2 Also shown is the beam 26d of the beam path 26, which, compared to the beam 26a, initially passes through the Fresnel section 28i, more precisely through its long edge 30 and short edge 32, and after passing through it, is incident on the long edge 34 of the Fresnel section 28 i+1 . From this long edge, the beam is partially reflected (as shown by the beam 26e) and partially transmitted (as shown by the beam 26f). The beam 26d is incident on the Fresnel section 28 i+1 in the region 36 of the Fresnel section, which region is actually in the shadow of the Fresnel section 28 i . The beam 26e is reflected in the shadow region 36 and is output-coupled from the light guide 16 to the user's eye through the Fresnel section 28 i+1 . This beam represents extraneous light or stray light, which does not contribute to correctly imaging the source image for generating the virtual image, but rather interferes with the imaging quality due to the generation of a double image. The beam 26e cannot contribute to correct imaging especially because it additionally passes through the Fresnel section 28 i . In addition, multiple reflections that degrade the imaging quality may occur during the passage through the edges 30 and 32. Additionally, if due to manufacturing tolerances, for example as a result of rounding of the Fresnel section 28 i (as shown by the dashed line 38 in the Fresnel section 28 i ), the Fresnel sections 28 i and 28 i+1 deviate from the target geometry, the imaging quality may deteriorate further. Such geometric errors lead to a further deterioration of the imaging quality.

[0053] When designing the imaging parameters of the output coupling arrangement, the edges of the sections through which the beam path 26 passes and the subsequent output coupling to the user's eye 14 are typically not taken into account and are therefore undesirable. On the other hand, for the see-through function, a certain transparency of the output coupling arrangement is required.

[0054] To avoid the above problems, according to the present invention, the region 29 of the output coupling arrangement 28 is struck by the light beam path 26, as Figure 1A shown, for example, not (partially) specularly reflected as a whole as in the prior art, such that the light beam path 26 is output-coupled from the light guide 16 over the entire region 29 of the output coupling arrangement 28, but only (partially) specularly reflected in a region in a predetermined part of the region 29. This is achieved by the fact that the region of the output coupling arrangement 28 struck by the light beam path 26 has been surface-treated in a predetermined region such that the light beam path 26 is output-coupled from the light guide 16 to the eye 14 via a first part of the region 29 of the output coupling arrangement struck by the light beam path 26, while the light beam path 26 is not output-coupled from the light guide 16 or is output-coupled to the eye 14 at most with a reduced intensity in a second part of the region 29 of the output coupling arrangement struck by the light beam that is different from the first part. This is described below with reference to Figures 3 to 7 this.

[0055] Figure 3 An exemplary embodiment is shown in which the light beam path 26 is output-coupled from the light guide 16 towards the user's eye 14 (see Figure 1 ) only via the first parts 42, 44, 46 of the Fresnel sections 28a, b, and c (three are shown here), while the light beam path 26 is not output-coupled from the light guide 16 towards the user's eye 14 in the second parts 48a, 48b (Fresnel section 28c), 50a, 50b (Fresnel section 28b), and 52a, 52c (Fresnel section 28a). For this purpose, the first parts 42, 44, 46 are provided with a reflective layer, and the reflectivity of these reflective layers can be in the range of 1% to 100%. The first parts 42, 44, 46 can be different in terms of the applied layers, especially in terms of their reflectivity values. The first parts 42, 44, 46 have been determined based on a previous measurement process including suitable measurement methods. The first parts 42, 44, 46 are confirmed based on minimum requirements regarding surface quality, the degree of shaping, and other parameters related to imaging quality. For example, suitable measurement methods include conventional methods for tactile and non-contact shape measurement, such as profilometry, white light interferometry, and chromatic confocal measurement methods.

[0056] In contrast, the second parts 48a, 48b, 50a, 50b, 52a, and 52b are not provided with a reflective layer. It should be understood that the reflective layer should be understood to refer not only to a single layer but also to a layer structure composed of multiple individual layers.

[0057] As a supplement or alternative to applying a reflective layer to the first parts 42, 44, 46, the second parts 48a, 48b, 50a, 50b, 52a, 52b may be provided with a refractive index matching layer that at least reduces the reflection of the light beam path 26 towards the eye 14 in the second part and / or couples the light beam path 26 out of the output of the light guide 16 in a direction away from the eye, as Figure 3 indicated by the light beam 26t in

[0058] The refractive index matching layer in the second part may also be formed by filling the side thereof facing away from the eye 14 with a transparent refractive index matching material by means of the Fresnel sections 28a, b, c, as indicated by the hatched area 59 for the section adjacent to the Fresnel section 28.

[0059] As Figure 3 shown, each of the first parts 42, 44, 46 is a region of the respective long edge of the Fresnel sections 28a, 28b, 28c that is located outside the respective shaded areas of the adjacent Fresnel sections (see the shaded area 36 in Figure 2 or the shaded area 63 shown, for example, in Figure 4 ).

[0060] In contrast, the shaded areas of the Fresnel sections are not provided with a reflective layer but form the second parts 48b, 50b, 52b.

[0061] Figures 4 to 7 shows an exemplary embodiment of the area 29 of the output coupling arrangement 28 that is struck by the light beam path 26, having a first part 60 with a selective reflective coating and a second part 62 without a reflective coating. In Figures 4 to 7 , the first parts 60 of the area of the output coupling arrangement 28 are indicated by the hatched sections, at which the light beam path 26 is coupled out towards the user's eye 14. In particular, the hatched sections may all have different coatings or may partly have different coatings. The second part 62 is indicated by the white area. Figure 4 The exemplary embodiment in Figure 3 corresponds to the exemplary embodiment shown in two dimensions in Figures 5 to 7 shows an alternative exemplary embodiment of the first parts at which the light beam path 26 is coupled out towards the user's eye 14. As described above, a reflective layer may be present in the first parts. In the remaining part (second part) of the area of the output coupling arrangement 28 shown in white, no light beam path 26 is coupled out towards the user's eye 14. In these areas, the light components of the light beam path 26 may be made harmless, in particular by being transmitted or coupled out in a direction away from the user's eye 14, such that no foreign light or stray light reaches the user's eye 14 from these second parts. In Figures 4 to 7In it, the shaded areas of adjacent Fresnel segments are also shown hatched and are provided with reference numeral 63.

[0062] Figure 8 A method for generating the output coupling arrangement 28 is illustrated in a flow chart.

[0063] In step S1, the area 29 of the output coupling arrangement 28 is measured and / or a suitable pattern is recorded. In step S2, a first part of the area of the output coupling arrangement 28 is determined, which first parts are suitable for output coupling the beam path 26 from the light guide 16 in the direction of the eye for imaging the source image. The first parts can be determined using suitable measuring methods, as specified above by way of example. In step S3a, a mask is generated, for example within the scope of a laser cutting method, an etching method or any other method. As an alternative or addition to step S3a, in step S3b local adhesion conditions are established for subsequent coating of the first parts. In step S4, the first parts of the area 29 determined in step S2 are provided with a reflective layer.

[0064] As a supplement or alternative thereto, step S2 can include determining second parts, which second parts are not suitable for output coupling the beam path 26 from the light guide 16 towards the user's eye 14. In step S4, the second parts can be provided with a refractive index matching layer, which refractive index matching layer reduces or prevents reflection of the beam path 26 at the second parts and / or promotes output coupling of the beam path 26 in the direction away from the user's eye 14. For this purpose, these segments can be filled on the outside with a transparent material as described above. In this case, the refractive index matching layer can also cover the reflective coating of the first parts 42, 44, 46, 60.

[0065] It should be understood that the invention is not limited to the configuration of the output coupling arrangement 28 having Fresnel segments, but is also applicable to non-segmented output coupling arrangements, which are these reflective, diffractive or refractive output coupling optical units. In the case of a non-segmented output coupling arrangement, parts of the area of the output coupling arrangement hit by the beam path 26 are also determined, and the surface of this area is treated as described above so that the beam path 16 is output-coupled only in the determined parts towards the user's eye 14.

Claims

1. An optical system for generating a virtual image of a source image provided on an imager, the optical system comprising at least one light guide to be worn in front of an eye, an input coupling arrangement for coupling a light beam path originating from the source image into the light guide, and an output coupling arrangement for coupling the light beam path out of the light guide towards the eye, wherein, the input coupling arrangement couples the light beam path into the light guide such that the light beam path propagates within the light guide by reflection at the inner surface and / or outer surface of the light guide to the output coupling arrangement, wherein the output coupling arrangement has a region that is impinged upon by the light beam path propagating in the light guide, characterized in that, the region of the output coupling arrangement that is impinged upon by the light beam path has a Fresnel section that has been surface-treated such that a plurality of first portions of the region of the output coupling arrangement couple the light beam path out of the light guide to the eye, the plurality of first portions being those predetermined portions of the region that meet a minimum requirement in terms of the surface quality for imaging the source image, while in a plurality of second portions of the region of the output coupling arrangement that are different from the plurality of first portions, the light beam path does not couple out of the light guide to the eye or couples out of the light guide to the eye with a reduced intensity that does not impair the quality of imaging the source image.

2. The optical system according to claim 1, wherein, the plurality of first portions have been surface-treated to have a reflective layer.

3. The optical system according to claim 2, wherein, the reflectivity of the reflective layer is in the range of 1% to 100%.

4. The optical system according to any one of claims 1 to 3, wherein, the plurality of first portions have been surface-treated to have reflective layers with reflectivity values that differ by at least 0.1%.

5. The optical system according to any one of claims 1 to 3, wherein, the plurality of second portions have been surface-treated to have a refractive index matching layer, and the refractive index matching layer in the plurality of second portions at least reduces the reflection of the light beam path towards the eye such that it does not impair the quality of imaging the source image, and / or causes the light beam path to be output-coupled from the light guide in a direction away from the eye.

6. The optical system according to any one of claims 1 to 3, wherein, the plurality of first portions are defined by shape measurement of the surface of the region of the output coupling arrangement.

7. The optical system according to claim 1, wherein, each first portion of the plurality of first portions is a portion of a zone of the Fresnel section that lies outside the shadow cast by adjacent Fresnel sections.

8. The optical system according to claim 1, wherein, each second portion of the plurality of second portions is at least a zone of the Fresnel section that lies within the shadow cast by adjacent Fresnel sections.

9. A method for producing an output coupling arrangement of an optical system for generating a virtual image of a source image provided on an imager, the method comprising: Determine a plurality of first portions of the area of the output coupling arrangement including the Fresnel section such that the plurality of first portions meet a minimum requirement in terms of the surface quality of the area for output-coupling a beam path that comes from the source image and propagates in the light guide from the light guide towards the user's eye for the purpose of imaging the source image. Perform a surface treatment on the area of the output coupling arrangement such that the beam path is output-coupled from the plurality of first portions to leave the light guide and reach the user's eye, while in a second portion of the area of the output coupling arrangement that is different from these plurality of first portions, the beam path is not output-coupled from the light guide or is output-coupled to the eye with a reduced intensity that does not impair the quality of imaging the source image.

10. The method according to claim 9, wherein, the surface treatment of the area of the output coupling arrangement includes applying a reflective layer on the plurality of first portions.

11. The method according to claim 10, wherein, the surface treatment is performed using a mask that masks these plurality of second portions when the reflective layer is applied.

12. The method according to any one of claims 9 to 11, wherein, the surface treatment of the area of the output coupling arrangement includes applying a refractive index matching layer on these plurality of second portions.

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