Optical assembly for a head-mounted display device, head-mounted display device, and method for assembling an optical assembly for a head-mounted display device

Abstract

An optical assembly for a head-mounted display device (HMD) is disclosed, which enables a detachable and secure installation of a waveguide in a capsule made of two lenses independently of a frame of the HMD. The optical assembly (10) comprises a first lens (12), a second lens (16) and a waveguide (14) in a stacked arrangement, wherein the waveguide (14) is arranged between the first and the second lens (12, 16). The first and the second lens (12, 16) comprise a snap-engagement structure (30) which is configured for snap-engagement of the lenses (12, 16) with one another with the waveguide (14) encapsulated therebetween. The invention also relates to a head-mounted display device (100) comprising the optical assembly (10) and to a method for assembling the optical assembly (10).

Description

Optical arrangement for a head-mounted display device, head-mounted display device and method for assembling an optical arrangement for a head-mounted display device

[0001] The present invention relates to an optical arrangement for a head-mounted display device, such as smart glasses or a virtual reality headset. The present invention further relates to a head-mounted display device. The present invention also relates to a method for assembling an optical arrangement for a head-mounted display device.

[0002] A see-through head-mounted display (HMD) for smart glasses typically comprises an image generator or projector system and an optical see-through system to transmit image light generated by the projector system as a virtual image to the user's eye. HMDs, particularly optical NED (near-eye display) systems, are known that are based on a see-through waveguide designed to guide the image light coupled into an input structure to an output structure via total internal reflection, where the image light is coupled out to the user's eye. To provide smart glasses with a correction for a user's visual impairment, i.e., to make them prescription-ready, it is known to create an optical structure in which the waveguide, either planar or curved, is supplemented by one or more corrective lenses (Rx lenses), e.g.,...by a pair of a push lens and a pull lens (usually the pull lens is located on the side of the waveguide facing the eye and the push lens on the side facing the environment) positioned across the user's field of view. Such an optical structure may include a stacked waveguide positioned between the push lens and the pull lens, also known as a push-pull optical system. It is known to use such push-pull optical systems in see-through HMDs to adjust the focal distance of the virtual image as projected onto the user's eye through the optical waveguide. Typically, one focal plane of the virtual image transmitted in the optical waveguide is at infinity, and the pull lens is used to pull the focal plane of the virtual image closer to the user for greater convenience.Since the pull lens positioned above the user's field of vision of the see-through HMD also uses the focal plane of a real image, the push lens is added to at least partially compensate for the effect of the pull lens on the real image.

[0003] Several technical problems need to be solved when designing such optical systems. These technical challenges may include at least one of the following: ensuring proper protection of the waveguide, which is the most expensive and sensitive component of the system; providing an air gap or vacuum gap around the waveguide, i.e., between the waveguide surfaces and the lenses in the stacked arrangement, to provide a change in the refractive index at the waveguide surfaces, thereby ensuring total internal reflection of the image light guided in the waveguide; and maintaining a simple, compact, and lightweight system design to meet, for example, manufacturing requirements and customer expectations. In addition to these technical challenges, it is desirable that the optical system design be compatible with most typical spectacle frames.Furthermore, it is highly desirable that the design of the optical system allows for a relatively simple lens replacement without damaging the waveguide. A simple lens exchange would make it possible to replace components of the smart glasses to adapt them to a user, as well as to unify and separate the processes for manufacturing lenses, waveguides and frames.

[0004] Known head-mounted displays (HMDs), particularly smart glasses, with removable prescription lenses employ a specific mechanical design of the frame to allow for the detachable attachment of the lenses. For example, US 11,815,685 B2 and US 10,983,352 B2 describe an HMD (smart glasses) with a head-mounted support structure (frame) designed to accommodate a planar waveguide, a non-removable lens, and a removable lens attached to the head-mounted support structure by magnets. Alternatively, US 2024 / 0077738 A1 discloses a smart glasses frame designed with bayonet-style fasteners, i.e., push-and-turn mechanisms, for the detachable attachment of the lens to the frame. In this design, an air gap between the waveguide and the removable lens is also provided by the mechanical design of the frame and the corresponding fastening means.

[0005] Therefore, known solutions for enabling removable Rx lenses in smart glasses require a special, more complex design of the smart glasses frame. This means that the frame design and the design of the optical components are closely linked and interdependent, thus preventing the use of typical spectacle frames in smart glasses. Furthermore, these known solutions offer limited protection of the waveguide against adverse environmental conditions, such as the lack of an air gap to protect against moisture and dust, particularly during lens replacement, as well as against careless user behavior, since a user could accidentally damage the waveguide during lens replacement.

[0006] There is therefore a need for a new design of the push-pull optics system for HMDs, e.g. in the form of smart glasses that offer proper waveguide protection, allow for the replacement of smart glasses components and fit into spectacle frames of different designs; i.e., there is a need for an improved push-pull optics system that is independent of the design of the spectacle frame.

[0007] The object of the present invention is therefore to provide an optical arrangement for an HMD which enables a detachable attachment of one or more Rx lenses to a waveguide, while enabling proper protection of the waveguide, wherein the frame design should not depend on the overall design of the optical arrangement and vice versa.

[0008] Another object of the present invention is to provide a corresponding head-mounted display device.

[0009] Another object of the present invention is to provide a corresponding method for assembling an optical arrangement for a head-mounted display device.

[0010] According to a first aspect of the present invention, an optical arrangement for a head-mounted display device is provided, comprising a first lens, a second lens and a waveguide in a stacked arrangement, wherein the waveguide is arranged between the first and the second lens and wherein the first and the second lens comprise a snap-engagement structure configured to snap the first and second lens together, the waveguide being encapsulated between the first and the second lens.

[0011] The present invention solves at least some of the technical problems described above. The first and second lenses of the optical arrangement according to the invention form a protective capsule for the waveguide secured therein. The capsule formed by the first and second lenses secures the waveguide within it, preventing movement relative to the lenses. The first and second lenses, with their snap-in mechanism, can have a relatively simple design suitable for mass production. The shapes of the first and second lenses may differ from conventional lenses only at their circumferential edges, where the snap-in mechanism is located, while the corrective surfaces of the lenses can be obtained using conventional manufacturing and processing techniques for corrective lenses. The optical arrangement according to the invention can be compact and lightweight.The first and second lenses can be separated by releasing the snap-fit ​​connection between them, thus enabling the replacement, inspection, and maintenance of the waveguide or lenses, as well as the adaptation of the system to the user's needs. The lens-replaceable feature, and essentially the overall design of the optical arrangement according to the invention, is independent of the frame design; that is, the optical arrangement can fit into various eyeglass frames, and the frame can be replaced during the smart glasses' lifecycle, for example, depending on the user's fashion preferences, without affecting the optical system. Furthermore, all major components of the HMD are interchangeable; for example, a projector can be replaced along with the waveguide.Furthermore, the design of the first and second lenses can be standardized for essentially any waveguide in any frame.

[0012] The term "lens" in this disclosure can encompass optical elements of any kind, for example, lenses with positive or negative optical power, in particular corrective lenses (Rx lenses), including progressive lenses, diffractive optical elements, glass plates without optical power, and the like. For example, one of the first and second lenses can be a corrective lens (Rx lens) manufactured according to a user's prescription. The other of the first and second lenses can also be a lens with a specific optical power, such as a corrective lens (e.g., the user's prescription can be realized with a combination of the optical powers of the two lenses), but it can also be a lens without optical power, e.g., a flat or curved plate with plane-parallel surfaces.

[0013] The term "waveguide" can, but is not limited to, include a planar waveguide, a curved waveguide, a stack of waveguides or waveguide layers, a waveguide housing containing a waveguide formed in a protective glass capsule, etc., which may be based on any optical waveguide technology, including, but not limited to, reflective, refractive and holographic types of waveguides.

[0014] The snap-in mechanism can be arranged at the peripheral edges or in the area of ​​the same of the first and second lenses and, in particular, can extend over the entire circumference of the first and second lenses without being limited thereto.

[0015] The snap-fit ​​structure can be configured such that the first and second lenses are in a rotationally fixed position relative to each other when they are in snap-fit ​​engagement. Such a rotationally fixed positional relationship can be achieved through friction and / or form fit of the interlocking snap elements of the snap-fit ​​structure.

[0016] Preferred embodiments of the present invention are defined in the dependent claims and / or are described below.

[0017] In one embodiment, the snap-fit ​​structure can comprise at least one first fitting element located on one of the first and second lenses, and at least one second fitting element located on the other of the first and second lenses, wherein the first and second fitting elements are configured to engage with each other by friction and / or form fit.

[0018] The friction and / or form fit between the fitting elements can be such that the first lens and the second lens are secured to each other in a direction parallel to the optical axis of the first and the second lens and / or in a radial direction with respect to the optical axis of the first and the second lens and / or in a circumferential direction around the optical axes of the first and the second lens.

[0019] In a further embodiment and in connection with the previous embodiment, one of the first and second lenses can have a seat for receiving the other of the first and second lenses, wherein the first fitting element is arranged on a wall of the seat and the second fitting element is arranged on a circumference of the other of the first and second lenses.

[0020] One of the lenses, with a seat to accommodate the other lens, has the advantage of a simple design that allows the waveguide to be encapsulated within the capsule formed by the two lenses. A further advantage is that it simplifies the centering of the lenses relative to each other.

[0021] In one of the preceding embodiments, it is preferred if one of the first and second fitting elements is an annular groove and the other of the first and second fitting elements is an annular flange.

[0022] In this embodiment, the snap-fit ​​structure is of a very simple yet reliable mechanical design. The lens encompassing the ring flange can advantageously be almost identical to a conventional lens, particularly a corrective lens, and can thus be manufactured using conventional techniques.

[0023] The annular groove and the annular flange can extend over the entire circumference of the first and second lenses. Furthermore, the annular groove can include one or more structural features, such as local recesses or depressions, that are spatially limited in the circumferential direction, and the annular flange can have one or more projections for engaging in the one or more recesses or depressions to secure the lenses against rotation relative to each other and / or to assist the user in rotatingly aligning the first and second lenses with each other during the snap-in engagement of the lenses.

[0024] In a further embodiment, at least one of the first and second lenses can comprise a further snap-engagement structure for snapping the waveguide with the at least one of the first and second lenses.

[0025] In this embodiment, the waveguide can be secured to one of the first and second lenses before the other is attached to it, further simplifying the assembly of the optical arrangement.

[0026] Furthermore, it is preferred if the waveguide is in a predetermined positional relationship, in particular a rotational relationship, to the first and second lenses, when the first and second lenses are in snap-fit ​​engagement with each other.

[0027] This embodiment is advantageous because it ensures the correct position of the waveguide relative to the lenses. When the lenses are in snap-fit ​​engagement with each other, the positional relationship is fixed.

[0028] Furthermore, it is preferred if the first and second lenses are in a predetermined positional relationship to each other, if the first and second lenses are brought into snap-fit ​​engagement with each other.

[0029] This embodiment is advantageous, for example, when the lenses have optically effective, non-rotationally symmetric surfaces, as is the case, for example, with lenses for correcting astigmatism.

[0030] In a further embodiment, the optical arrangement can include a spacer structure to provide an air gap in at least one waveguide region of the waveguide between at least one waveguide surface of the waveguide and a lens surface of at least one of the first and second lenses facing the at least one waveguide surface.

[0031] Thus, an air gap can be advantageously and simply provided along the waveguide area between the waveguide and at least one of the first and second lenses. Preferably, the spacer structure forms an air gap on both sides of the waveguide, i.e., to each of the first and second lenses. If the spacer structure, the snap-fit ​​structure, and / or other sealing means provide a seal for the optical arrangement (i.e., the capsule formed by the lenses snapping together), a vacuum gap can be provided instead of an air gap between the waveguide and at least one of the first and second lenses, which would improve waveguide protection.

[0032] In a further embodiment, the spacer structure can comprise at least one projection extending from the lens surface facing the at least one waveguide surface to the at least one waveguide surface, wherein the at least one waveguide surface rests against the at least one projection.

[0033] In this embodiment, the spacer structure has a very simple mechanical design. In particular, the at least one projection, which may have a short radial extension and may be arranged in a circumferential region of the lens, can be an integral part of the lens surface facing the at least one waveguide surface, as provided in a further embodiment. It is also preferred that both lenses each include a projection, so that the waveguide can be clamped between the projections and thereby secured in a fixed position between the lenses, while simultaneously providing an air gap to maintain the total internal reflection conditions in the waveguide region of the waveguide.

[0034] In a further embodiment, which may be an alternative to the previous embodiments but may also be used in addition to the previous embodiments, the spacer structure may comprise at least one spacer arranged between the at least one waveguide surface and the lens surface facing the at least one waveguide surface.

[0035] This embodiment, with a simple mechanical design, also allows for an air gap between one or both surfaces of the waveguide and the adjacent lenses.

[0036] In particular, the spacer structure can comprise a stretchable ring-shaped strip that is stretched over and around a circumferential edge of the waveguide.

[0037] This embodiment is particularly advantageous because the spacer structure can be easily attached to the waveguide by stretching the elastic annular strip over and around a circumferential edge of the waveguide. Upon release, the annular strip elastically contracts, gripping the waveguide in such a way that its edges extend onto the waveguide surfaces from both sides, thus creating spacers between the two waveguide surfaces and the adjacent lenses. This requires only that the strip width be greater than the thickness of the waveguide's circumferential edge.

[0038] In another embodiment, the spacer structure can be elastic, in particular compressible.

[0039] An elastic spacer structure offers a very simple and cost-effective design to provide additional protection for the waveguide encapsulated between the lenses.

[0040] In a compressible spacer structure, the thickness of the spacer in the compressed state, which rests against the waveguide and separates it from the lenses when the lenses are snapped together, defines the thickness of the air gap.

[0041] In a further embodiment, the spacer structure can comprise a first part and a second part, wherein the first part and the second part are compressible, one of the first and second parts being more compressible than the other. For example, the spacer of the spacer structure can have a less compressible base part that contacts the waveguide and a more compressible part, for example, projections of an uneven relief surface profile of the spacer.

[0042] Instead of providing an air gap or a vacuum gap for optical isolation of the lenses from the waveguide, in another embodiment the waveguide may comprise a coating with a low refractive index or an angle-selective reflective interference coating on at least one surface of the waveguide for optical isolation of the waveguide from the first lens and / or the second lens.

[0043] This embodiment has the advantage that the thickness of the optical arrangement can be reduced in the direction of the optical axis, since no air gap is required between the waveguide and the lenses to guide the image light through the waveguide.

[0044] In another embodiment, the snap-in engagement structure can be configured to seal the stacked arrangement of the first and second lenses with the waveguide in a circumferential region of the stacked arrangement.

[0045] This embodiment has the advantage that reliable protection of the waveguide and the capsule interior formed by the snap-fit ​​lenses against adverse environmental conditions, such as moisture, dust, etc., can be achieved without additional sealing measures, thus further simplifying the mechanical design of the optical arrangement. Alternatively or additionally, an adhesive seal can be provided around the circumference of the optical arrangement. Furthermore, as mentioned above, sealing the optical arrangement allows for the creation of a vacuum gap between the waveguide and at least one of the first and second lenses instead of an air gap, thereby further improving waveguide protection.

[0046] In a further embodiment, at least one of the first and second lenses can comprise a composite structure consisting of a first part made of a first material and at least one second part made of a second material different from the first material. For example, at least one of the first and second lenses can be a composite lens comprising, for instance, a glass part to increase stiffness and a plastic part to reduce the size and weight of the lens.

[0047] In a further and / or related embodiment, at least one part of the snap-engagement structure of at least one of the first and second lenses comprises a plastic material.

[0048] This embodiment has the advantage that the lenses are particularly easy to snap together and the snapping process is harmless to the lenses due to the increased flexibility of the plastic part of the snap-in engagement structure, i.e., the risk of damage, e.g., breakage, to the lenses when snapping them together is at least reduced.

[0049] According to a second aspect of the present invention, a head-mounted display device is provided which comprises an optical arrangement according to the first aspect of the invention.

[0050] According to a third aspect of the present invention, a method for assembling an optical arrangement for a head-mounted display device is provided, the method comprising the following: Providing a first lens, a second lens and a waveguide, wherein the first and second lenses comprise a snap-fit ​​structure, Arranging the first lens, the waveguide and the second lens in a stacked arrangement, wherein the waveguide is positioned between the first and the second lens, snap-fit ​​engagement of the first and second lenses using the snap-fit ​​structure, thereby forming the optical arrangement that encapsulates the waveguide between the first and second lenses.

[0051] It is understood that the HMD and the method according to the invention may have the same or similar advantages and embodiments as described above with regard to the optical arrangement according to the invention.

[0052] Further features and advantages of the invention will become apparent from the following description and the accompanying drawings.

[0053] Embodiments of the invention are shown in the drawings and are described below with reference to the drawings. The drawings show: Fig. 1 shows a cross-sectional part of an optical arrangement for an HMD according to an embodiment of the present invention; Fig. 2 shows a cross-sectional part of an optical arrangement for an HMD according to another embodiment of the present invention; Fig. 3 shows a cross-sectional part of an optical arrangement for an HMD according to another embodiment of the present invention; Fig. 4 shows a cross-sectional part of an optical arrangement for an HMD according to yet another embodiment of the present invention; and Fig. 5 shows a part of an HMD in the form of data glasses according to an embodiment of the present invention.

[0054] With reference to Figures 1 to 4, embodiments of an optical arrangement 10 according to the present invention are described by means of illustrative, non-limiting examples. In each embodiment, the optical arrangement 10 is configured for use in (as part of) a head-mounted display (HMD), which is described later with reference to Figure 5. Figures 1 to 4 show only a portion of the optical arrangement 10, comprising a peripheral region of the optical arrangement 10. An optical axis OA of the optical arrangement 10 is shown in Figure 1 for illustration. Unless otherwise specified, the following description applies to all embodiments shown in Figures 1 to 4. In Figures 1 to 4, identical, similar, or comparable elements are designated by the same reference numerals.

[0055] With reference to Figures 1 to 4, the optical arrangement 10 comprises a first lens 12, a waveguide 14, and a second lens 16. The first lens 12 can be, but is not limited to, a corrective lens (Rx lens). The second lens 16 can also be, but is not limited to, a corrective lens (Rx lens). The waveguide 14 can be a planar waveguide, as shown in Figures 1 to 4, but can also be a curved waveguide, a stack of waveguides or waveguide layers, a waveguide housing containing a waveguide formed in a protective glass capsule, etc.

[0056] The lens 12, the waveguide 14 and the lens 16 are arranged in a stack, with the waveguide 14 positioned between the first lens 12 and the second lens 16.

[0057] When the optical arrangement 10 is integrated into a head-mounted display (HMD), such as smart glasses, worn on the user's head in front of the user's eye(s), the second lens 16 can be located on the eye-facing side of the waveguide 14, which can also be referred to as the back or inside of the waveguide 14, while the first lens 12 is located on the environment-facing side of the waveguide 14, which can also be referred to as the front or outside of the waveguide 14. In this configuration, the first lens 12 can be a push lens, and the second lens 16 can be a pull lens, thus forming the push-pull optical system of the optical arrangement 10.

[0058] The lens 12 has two opposing principal surfaces, essentially perpendicular to the optical axis OA, namely surface 18 and an opposing surface 20. Surface 20 of the lens 12 faces the waveguide 14, while surface 18 faces away from the waveguide 14, i.e., towards the surroundings. The waveguide 14, in turn, has two opposing principal surfaces: a first surface 22 facing the first lens 12 and a second surface 24 facing the second lens 16, between which the light is guided. The second lens 16 then has two opposing principal surfaces: a surface 26 facing the waveguide 14 and a surface 28 facing away from the waveguide 14.

[0059] The first lens 12 and the second lens 16 comprise a snap-fit ​​structure 30 configured for snap-fit ​​engagement between the first and second lenses 12, 16, with the waveguide 14 being encapsulated between the first and second lenses 12, 16 when the lenses 12 and 16 are snapped together. Thus, when the first lens 12 and the second lens 16 are brought into snap-fit ​​engagement, as shown in Fig. 1, the first and second lenses 12, 16 form a capsule in which the waveguide 14 is secured and well protected.

[0060] With reference to Figures 1 to 4, the snap-fit ​​structure 30 comprises at least one first fitting element 32 provided on the second lens 16 and at least one second fitting element 34 provided on the first lens 12. The first fitting element 32 and the second fitting element 34 are configured to engage with each other by friction and / or a form fit; that is, the first and second fitting elements 32, 34 can be held together in a connection by friction and / or interlocking and mutually locking. In the embodiment shown, the second fitting element 34 is an annular flange, and the first fitting element 32 is an annular groove configured to engage with the annular flange. It is also possible, although not shown, for the first fitting element 32 to be a flange and the second fitting element 34 to be a groove.The first fitting element 32 and the second fitting element 34 can extend over the entire circumference of the first and second lenses 12, 16, without being restricted to them. The snap-fit ​​structure 30 secures the first and second lenses 12 and 16 to each other at least in a linear direction parallel to the optical axis OA of the optical arrangement 10 and in a radial direction with respect to the optical axis OA, and can also be configured such that the first and second lenses 12, 16 are secured to each other in a predetermined positional relationship, in particular in a predetermined rotational relationship with respect to each other, for example, such that they can only be brought into snap engagement with each other in a predetermined positional relationship with respect to each other.This can be achieved, for example, by having one of the lenses 12, 16 as part of the first and second fitting elements 32, 34 include at least one projection and the other of the lenses 12, 16 include at least one corresponding recess or indentation, thereby ensuring that the first and second fitting elements 32, 34 can only engage with each other when the at least one projection is aligned with the at least one recess or indentation.

[0061] The second lens 16 includes a seat 36 for receiving the first lens 12. The seat 36 can also receive the waveguide 14, as shown in Fig. 1. The seat 36 can be formed by an annular flange 38, which can extend over the entire circumference of the second lens 16 and in a direction perpendicular to the surface 26 of the second lens 16. The first fitting element 32 (configured as a groove in the embodiments shown in Figs. 1 to 4) is arranged on a wall of the seat 36, here the inner wall of the flange 38. When the lenses 12 and 16 are in snap-fit ​​engagement with each other, the waveguide 14 is in a fixed positional relationship to the first and second lenses 12, 16, for example by friction fit and / or form fit with the first and second fitting element 32, 34 and / or other elements of the optical arrangement 10 that bear against the waveguide 14 or form a carrier for it.

[0062] Furthermore, when lenses 12 and 16 are in snap-fit ​​engagement with the intervening encapsulated waveguide 14, a first air gap (or vacuum gap) 40 is provided between the surface 20 of the first lens 12 and the first surface 22 of the waveguide 14, which faces the surface 20 of the first lens 12; that is, the surfaces 20 and 22 are spaced apart from each other by the air gap. A second air gap (or vacuum gap) 42 is arranged between the mutually facing surfaces 24 and 26 of the waveguide 14 and the second lens 16. The air gaps 40 and 42 are provided in at least one waveguide region of the waveguide 14, that is, in a region of the waveguide 14 in which image light generated by a projector (not shown) is guided by total internal reflection between the first and second surfaces 22 and 24 of the waveguide 14.

[0063] To enable the air gaps 40 and 42, the optical arrangement 10 includes a spacer structure 44 designed to keep the surfaces 20, 22 separated from each other and to keep the surfaces 24, 26 separated from each other at least in the waveguide area of ​​the waveguide 14.

[0064] Referring to Figures 1 to 4, the spacer structure 44 comprises a first projection 46 extending from the surface 20 of the first lens 12 towards the waveguide 14. When the first and second lenses 12 and 16 are in snap-fit ​​engagement with each other, as shown, for example, in Figures 1 and 4, the first surface 22 of the waveguide 14 rests against the projection 46. The spacer structure 44 further comprises a projection 48 extending from the surface 26 of the second lens 16 towards the second surface 24 of the waveguide 14, so that the second surface 24 of the waveguide 14 rests against the projection 48 when the lenses 12 and 16 are snapped into each other. In one embodiment, this causes the waveguide 14 to be clamped between the projections 46, 48 when the first and second lenses 12, 16 are in snap engagement, as shown, for example, in Figs. 1 and 4.

[0065] The projections 46 and 48 can extend over the entire circumference of the first and second lenses 12, 16. The projections 46 and 48 can be integral with the first and second lenses 12, 16, i.e., they can be formed as integral parts of the first and second lenses 12, 16 during a manufacturing process, e.g., an injection molding process. In other embodiments (not shown), the projections 46 and 48 can be separate elements from the first and second lenses 12, 16, e.g., in the form of pads attached to the surfaces 20 and 26 of the first and second lenses 12, 16 by means of an adhesive. In one embodiment, the projections 46, 48 are made of an elastic material, in particular a compressible material.

[0066] With reference to Figures 1 to 4, the snap-fit ​​structure 30 can further be configured to seal the stacked arrangement of the first and second lenses 12, 16 and the waveguide 14 in the circumferential region of the stacked arrangement. In particular, the snap-fit ​​structure 30 can seal the interior of the capsule formed by the first and second lenses 12, 16 when snapped together, including the air gaps 40, 42, against the environment; for example, the snap-fit ​​structure 30 can prevent moisture, dust, etc., from contaminating the optical surfaces of the lenses 12, 16 and the waveguide 14.

[0067] In one embodiment, at least the second lens 16, which includes the seat 36 for receiving the first lens 12, comprises a composite structure with a first part made of a first material and at least a second part made of a second material different from the first material. In particular, the main part of the second lens 16 can be a rigid glass part or a rigid part made of hard, transparent plastic, such as is typically used for eyeglasses, while the flange 38, at least in the region of the first fitting element 32, can be made of a more elastic plastic material (compared to the material of the rigid part). This facilitates the insertion of the first lens 12 into the seat 36, with the first lens 12 snapping into the second lens 16 without the risk of damaging one or both of the first and second lenses 12, 16.Furthermore, or alternatively to the above, the seat 36 may have a taper or chamfer 50 made of an elastic material to facilitate the insertion of the first lens 12 and the waveguide 14 into the seat 36.

[0068] In addition to or as an alternative to the sealing effect of the snap-fit ​​structure 30, the capsule formed from the first and second lenses 12, 16, which are snapped into one another, can be sealed by an adhesive seal, which, however, should allow easy separation of the first and second lenses 12, 16 from each other without damaging the lenses 12, 16 and the waveguide 14; for example, a peelable adhesive can be used for such a seal.

[0069] In the embodiment of Fig. 2, the spacer structure 44 of the optical arrangement 10 has a spacer 52 which is arranged at least on one side of the waveguide 14, i.e., between one of the first and second waveguide surfaces 22, 24 and the corresponding lens surface 20, 26 facing that waveguide surface, in order to allow the corresponding air gap or vacuum gap 40 or 42. Preferably, the spacer 52 is arranged on both sides of the waveguide 14 (or extends to both sides of it), i.e., at least a part of the spacer 52 is arranged between each of the first and second waveguide surfaces 22, 24 and the corresponding lens surface 20, 26 facing the waveguide surface, in order to allow the air gaps or vacuum gaps 40, 42 on both sides of the waveguide 14, at least in the waveguide region of the waveguide 14.In a preferred embodiment, the spacer 52 is elastic, e.g. made of an elastic material such as an elastomer or rubber, to provide additional protection for the waveguide 14.

[0070] In one embodiment, the spacer 52 is configured as a stretchable annular strip that is to be stretched over and around a circumferential edge 54 of the waveguide 14. In this embodiment, a fully circumferential annular spacer 52 can have a C-shaped cross-section and can comprise legs 56, 58 connected by a web 57, wherein the legs 56, 58 overlap the circumferential edge 54 of the waveguide 14 from both sides, so that the waveguide 14 is clamped between the legs 56 and 58 of the spacer 52, as shown in Figures 2 and 3. The thickness of the legs 56, 58 defines the thickness of the air gaps 40, 42.In a preferred embodiment, the legs 56, 58 are designed to be compressible such that when the first and second lenses 12, 16 snap together, the legs 56, 58 are compressed and the air gaps 40, 42 in their compressed state are defined by the thickness of the legs 56, 58.

[0071] The embodiment of Fig. 3 differs from the embodiment of Fig. 2 in the implementation of the spacer 52. The spacer 52 of the optical arrangement 10 in the embodiment of Fig. 3 comprises parts with different compressibilities. As shown in Fig. 3, the spacer 52, in particular the legs 56 and 58 of the spacer 52, can have a non-uniform cross-section; that is, it can have a uniform base part that contacts the waveguide 14, which is less compressible, and non-uniform projections or serrations 60 that extend from the base part and contact the surfaces of the first and second lenses 12, 16, which, due to their non-uniformity, are more compressible than the base part. Such an implementation of the spacer 52 further facilitates the insertion of the first lens 12 and the waveguide 14 into the seat 36.

[0072] In the embodiments of Figs. 2 and 3, the elastic spacer structure 44 not only provides the air gaps 40 and 42, but also advantageously provides a seal for the air gaps 40, 42 as well as securing and protecting the waveguide 14 between the first and second lenses 12, 16, which are snapped into each other.

[0073] The embodiment of Fig. 4 is similar to the embodiment of Fig. 1 and differs from it by an additional snap-engagement structure 64 for the snap-engagement of the waveguide 14 with the second lens 16. The additional snap-engagement structure 64 can be arranged on the wall of the seat 36, i.e., on the inner wall of the flange 38. The additional snap-engagement structure 64 can include an annular flange or projection 66 that extends from the wall of the seat 36 toward the waveguide 14, i.e., inwardly. The flange 66 can extend over the entire circumference of the waveguide 14 or can be provided only along a portion of the circumference of the waveguide 14.The flange or projection 66 can comprise an elastic material, for example a plastic or rubber material, so that a snap-fit ​​engagement between the waveguide 14 and the second lens 16 can be easily produced without the risk of damaging the waveguide 14 and the second lens 16.

[0074] In an alternative embodiment (not shown) of the optical arrangement 10, it is also possible, instead of providing an air gap, such as the air gaps 40, 42, to provide the first and second surfaces 22 and 24 of the waveguide 14 with a coating with a low refractive index or with an angle-selective reflective interference coating suitable for optically isolating the waveguide 14 from the first and second lenses 12, 16 at least in the waveguide region, even if the surfaces 20, 26 of the first and second lenses 12, 16 are in contact with the first and second surfaces 22, 24 of the waveguide 14 in their waveguide region.

[0075] The embodiments shown in Figures 1 to 4 are for illustrative purposes only; it is not assumed that any of the illustrations in Figures 1 to 4 limit the scope of protection of the present invention. Furthermore, it is understood that elements and details of the embodiments described above with reference to Figures 1 to 4 can be combined in various ways without deviating from the scope of protection of the invention. For example, the additional snap-engagement structure 64, as shown in Figure 4, can also be provided in any of the embodiments of the optical arrangement 10 in Figures 1 to 3 with the same advantages. In the other example, the projections 46, 48 of the spacer structure 44, which are shown in all embodiments of the optical arrangement 10 in Figures 1 to 4, can be provided in any of the embodiments, for example, in the embodiments of Figures 1 to 3.2 and 3 are omitted, with the spacer 52 essentially replacing the projections 46, 48.

[0076] Fig. 5 shows part of a head-mounted display (HMD) in the form of smart glasses 100 according to an embodiment of the present invention. The smart glasses 100 comprise a frame 102 and an optical arrangement 10 according to one of the optical arrangements 10 described above with reference to Figs. 1 to 4, wherein the optical arrangement 10 is inserted in the frame 102. As can be seen in Fig. 5, the frame 102 has a typical spectacle frame design, and one of the advantages of the present invention is that the optical arrangement 10 does not require any special adaptation of the frame 102 to the design of the optical arrangement 10 and vice versa.It is obvious to a person skilled in the art that the frame 102 is further configured to accommodate intelligent systems of the data glasses 100, including, but not limited to, an image generator or projector 104, a control system, and a battery (not shown), and to couple the intelligent systems with the optical arrangement 10 (optically, physically, and / or functionally). It is further understood that the invention is in no way limited with respect to the intelligent systems of the data glasses 100, for example, with regard to which intelligent systems are required for the proper functioning of the data glasses 100 and how these systems are housed in the frame 102 or coupled with the optical arrangement 10.Embodiments of the present invention provide an improved, unified design of the optical arrangement 10, which includes the stacked arrangement of the first lens 12, the waveguide 14, and the second lens 16, forming the push-pull optical system, and which does not require any special support structure or elements in the frame 102. As a result, the design of the frame 102 is essentially independent of the design of the optical arrangement 10.

[0077] Referring to Fig. 5, and as mentioned above, the data glasses 100 further comprise the image generator or projector 104, for example a flat-screen display device such as an LCD module, an LCoS module, an OLED module, etc., for providing image light, as is known in the prior art. The projector 104 is shown in Fig. 5 for illustrative purposes only, as being arranged in a central nose bridge portion of the frame 102, since it could just as easily be arranged in end pieces or in any other part of the frame 102, for example, in temples. The projector 104 is typically followed by optics (not shown) for directing the image light provided by the image generator or projector 104 to the waveguide 14 of the optical arrangement 10.As is known to those skilled in the art, the waveguide 14 can comprise an input coupling structure (not shown) that couples the image light into the waveguide 14, and the waveguide 14 can be configured to guide the coupled image light by total internal reflection to an output coupling structure (not shown) of the waveguide 14, which couples the image light out of the waveguide 14 into an eyebox, i.e., to the eye of a user wearing the data glasses 100. The optical arrangement 10 provides an optical transmission system to transmit image light generated by the projector 104 as a virtual image, together with ambient light as a real image, into the user's field of vision and into the user's eye.

[0078] A method for assembling an optical arrangement according to the present invention, such as the optical arrangement 10 according to one of the embodiments described above with reference to Figures 1 to 4, comprises the following steps.

[0079] First, the first lens 12, the second lens 16 and the waveguide 14 are provided, for example by injection molding, such that the first and second lenses 12, 16 comprise a snap-in engagement structure, which is the snap-in engagement structure 30 according to one of the embodiments of the present invention described above.

[0080] The first lens 12, the waveguide 14 and the second lens 16 are then arranged in a stacked arrangement, with the waveguide 14 being placed between the first and the second lens 12, 16.

[0081] Then the first and second lenses 12, 16 are snapped into engagement with each other using the snap-in structure 30, thereby encapsulating the waveguide 14 between the first and second lenses 12, 16 to form the optical arrangement 10.

[0082] It is understood by those skilled in the art that the described assembly method is simple and intuitive, so that the optical arrangement 10 can be safely assembled by a user without professional assistance. It is also understood that the optical arrangement 10 according to the invention is relatively easy to disassemble and that one of the first and second lenses 12, 16 or the waveguide 14 can be replaced by separating the first lens 12 and the second lens 16 from each other by releasing the snap-fit ​​connection between the first and second lenses 12, 16.

Claims

Claims 1. Optical arrangement for a head-mounted display device (100) comprising a first lens (12), a second lens (16) and a waveguide (14) in a stacked arrangement, wherein the waveguide (14) is arranged between the first and the second lens (12, 16) and wherein the first and the second lens (12, 16) comprise a snap-engagement structure (30) configured to snap the first and the second lens (12, 16) together, wherein the waveguide (14) is encapsulated between the first and the second lens (12, 16).

2. Optical arrangement according to claim 1, wherein the snap-fit ​​structure (30) comprises at least one first fitting element (32) arranged on one of the first and second lenses (12, 16), and at least one second fitting element (34) arranged on the other of the first and second lenses (12, 16), wherein the first and second fitting elements (32, 34) are configured to engage with each other by at least one friction and form fit.

3. Optical arrangement according to claim 2, wherein one of the first and second lenses (12, 16) has a seat (36) for receiving the other of the first and second lenses (12, 16), wherein the at least one first fitting element (32) is arranged on a wall of the seat (36) and the at least one second fitting element (34) is arranged on a circumference of the other of the first and second lenses (12, 16).

4. Optical arrangement according to claim 2 or 3, wherein one of the first and second fitting elements (32, 34) is an annular groove and the other of the first and second fitting elements (32, 34) is an annular flange.

5. Optical arrangement according to any one of claims 1 to 4, wherein at least one of the first and second lenses (12, 16) comprises a further snap-engagement structure (64) for snap-engagement of the waveguide (14) with the at least one of the first and second lenses (12, 16).

6. Optical arrangement according to any one of claims 1 to 5, wherein the first and second lenses (12, 16) are in a predetermined positional relationship to each other when the first and second lenses (12, 16) are in snap-engagement with each other.

7. Optical arrangement according to one of claims 1 to 6, further comprising a spacer structure (44) to provide an air gap (40, 42) at least in a waveguide region of the waveguide between at least one waveguide surface (22, 24) of the waveguide (14) and a lens surface (20, 26) of at least one of the first and the second lens (12, 16) which faces the at least one waveguide surface (22, 24).

8. Optical arrangement according to claim 7, wherein the spacer structure (44) comprises at least one projection (46, 48) extending from the lens surface (20, 26) facing the at least one waveguide surface (22, 24) to the at least one waveguide surface (22, 24), wherein the at least one waveguide surface (22, 24) abuts the at least one projection (46, 48).

9. Optical arrangement according to claim 8, wherein the at least one projection (46, 48) is an integral part of the lens surface (20, 26) facing the at least one waveguide surface (22, 24).

10. Optical arrangement according to one of claims 7 to 9, wherein the spacer structure (44) comprises at least one spacer (52) arranged between the at least one waveguide surface (22, 24) and the lens surface (20, 26) facing the at least one waveguide surface (22, 24).

11. Optical arrangement according to claim 10, wherein the at least one spacer (52) is elastic and / or compressible.

12. Optical arrangement according to claim 10 or 11, wherein the spacer (52) comprises a stretchable annular strip that is stretched over and around a circumferential edge (54) of the waveguide (14).

13. Optical arrangement according to one of claims 10 to 12, wherein the spacer (52) comprises a first part and a second part, wherein the first part and the second part are compressible, wherein one of the first and the second part is more compressible than the other of the first and the second part.

14. Optical arrangement according to any one of claims 1 to 13, wherein the waveguide (14) comprises a coating with a low refractive index or an angle-selective reflective interference coating on at least one surface (22, 24) of the waveguide (14) for optical isolation of the waveguide (14) from the first and / or the second lens (12, 16).

15. Optical arrangement according to any one of claims 1 to 14, wherein the snap-in engagement structure (30) is configured to seal the stacked arrangement of the first and second lens (12, 16) and the waveguide (14) in a circumferential region of the stacked arrangement.

16. Optical arrangement according to any one of claims 1 to 15, wherein at least one of the first and the second lens (12, 16) comprises a composite structure consisting of a first part made of a first material and at least a second part made of a second material which is different from the first material.

17. Optical arrangement according to one of claims 1 to 16, wherein at least a part of the snap-in engagement structure (30) comprises a plastic material.

18. Head-mounted display device comprising an optical arrangement (10) according to any one of claims 1 to 17.

9. Method for assembling an optical arrangement (10) for a head-mounted display device (100), the method comprising: Providing a first lens (12), a second lens (16) and a waveguide (14), wherein the first and second lenses (12, 16) comprise a snap-fit ​​structure (30), Arranging the first lens (12), the waveguide (14) and the second lens (16) in a stacked arrangement, wherein the waveguide (14) is arranged between the first and the second lens (12, 16), snap-fit ​​the first and second lenses (12, 16) together using the snap-fit ​​structure (30), forming the optical arrangement (10) that encapsulates the waveguide (14) between the first and second lenses (12, 16).

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