Head-mounted display, holder for a lens for head-mounted display, and method of assembling head-mounted display

Abstract

A head-mounted display (HMD) (10) with a vision correction lens (16) is proposed which is easy and cost-effective to manufacture. The HMD (10) comprises a frame (12) having a mounting space (20) for accommodating a waveguide (14) and a holder (18) with a lens (16) inserted in the holder (18). The holder (18) is configured for releasable attachment to the frame (12). The holder (18) comprises a supporting part (40) protruding beyond a lens surface (28) of the lens (16), when the lens (16) is inserted in the holder (18). The supporting part (40) of the holder abuts an adjacent waveguide surface (30) of the waveguide (14), when the holder (18) with the lens (16) is inserted in the mounting space (20), so as to provide an airgap (26) between the adjacent waveguide and lens surfaces (28, 30). A holder (18) for a lens (16) and a method of assembling an HMD (10) is proposed as well.

Description

Head-mounted display, holder for a lens for head-mounted display, and method of assembling head-mounted display

[0001] The present invention relates to head-mounted displays such as smartglasses or virtual reality headsets. The present invention further relates to a holder for a lens for a headmounted display. Furthermore, the present invention relates to a method of assembling a head-mounted display.

[0002] Head-mounted display (HMD) systems enable visual immerse of a user in an extended reality (XR) environment, such as a virtual reality (VR) environment, an augmented reality (AR) or a mixed reality (MR) environment, by projecting a virtual image content to the user's eye. Smartglasses are eye or head-worn wearable AR or MR devices which may include displays that add virtual image content alongside or to what a wearer sees through the smartglasses, i.e. superimpose virtual image content provided by an image generator onto a field of view of the wearer of the smartglasses. Virtual reality headsets are eye or head-worn wearable devices which do not allow a wearer to directly see a realenvironment through opaque displays and present to the wearer only a virtual image content provided by the image generator, though in this case an information about the real environment can be captured, e.g. with cameras or lidars, and added to the virtual image content.

[0003] A head-mounted display (HMD) or near eye display (NED) usually comprises an image generator or projector system and an optical system to transmit an image light generated by the projector system to a user eye as a virtual image. For example, known are HMD optical systems based on a see-through or opaque planar or curved waveguide designed to guide the image light coupled-in at an in-coupling structure by total internal reflections to an out-coupling structure, where the image light is output-coupled towards the eye or eyes of the user. In order to provide an HMD with a correction of vision defects of the user, such as a prescription-enabled smartglasses, it is known to create an optical structure, where a waveguide is supplemented with a prescription (Rx) lens or lenses arranged across a field of view of the user. In other words, such an optical structure may include a stacked arrangement of a waveguide and an Rx lens or Rx lenses. In a see-through HMD such a stacked optical arrangement can comprise two Rx lenses arranged on either side of a waveguide (to act on both the virtual and real environment images), while an opaque HMD can comprise a single Rx lens arranged on an eye-side of a waveguide.

[0004] One of the technical problems to be solved in the design of such optical systems is to provide an airgap or a vacuum gap around the waveguide, i.e. between the waveguiding surfaces of the waveguide and the surfaces of the Rx lens or lenses in the stacked arrangement, so as to provide a large enough refractive index step at the waveguiding surfaces and thereby ensure total internal reflections of the image light guided inside the waveguide. At that, it is desirable to have an HMD optical system designed with removable Rx lens or lenses to enable customization of the HMD for a specific user prescription.

[0005] In the present disclosure, the term "airgap" does not only encompass a gap filled with natural air, but also a gap filled with a fluid or a gap which is void of any material, i.e. a vacuum gap.

[0006] Known are different designs of HMDs with a waveguide and Rx lenses, including an HMD with a head-mounted support structure accommodating a planar waveguide, a non-remov- able lens and a removable lens which is coupled to the head-mounted support structure by magnets, for example as described in US11 ,815,685 B2 and US10,983,352 B2, or using bayonet mounts, i.e. push-and-turn structures, as described in US2024 / 007773 A1, as well as a smartglasses design where a support frame accommodates a planar waveguide and an Rx lens which is coupled to the frame using an elastic ring fit into a groove on the edge of the lens and a corresponding recess in the frame, as described in CN 220419686 II. In CN 220419686 II, an air gap between the planar waveguide and the Rx lens is provided by a mechanical design of the support frame, having a part projecting in-between thereof to act as a spacer.

[0007] The mechanical design-based solution disclosed in CN 220419686 II, although being simple and cost-effective to manufacture, does not allow the Rx lens to be removable. With this design, there is a high risk of mechanical damage to the waveguide if a user attempts to disassemble and re-assemble the smartglasses to replace the Rx lens without professional assistance. The technical designs disclosed in the other documents mentioned above provide for a HMD with a removable Rx lens, however through a more complex design leading to an increased cost of manufacture.

[0008] Thus, there is a need in a simple mechanical arrangement for attachment of an Rx lens or lenses to a waveguide in an HMD that allow the Rx lens or lenses to be removable, i.e. to allow self-assembly and disassembly of the system by a user in certain cases, for example, when a simple air gap is provided between the waveguide and the Rx lens, while ensuring for a proper protection of the waveguide from mechanical damage and for a required air gap or air gaps to maintain the conditions for total internal reflection of the light guided in the waveguide.

[0009] It is an object of the present invention to provide a HMD which allows for releasable attachment of an Rx lens or Rx lenses to a waveguide while ensuring for a proper protection of the waveguide from mechanical damage and for a required air gap or air gaps to maintain the conditions of total internal reflection, and wherein the HMD is cost-effective to manufacture.

[0010] It is a further object of the present invention to provide a holder for a lens for an HMD.

[0011] It is a further object of the present invention to provide a method of assembling an HMD.

[0012] According to a first aspect of the present invention, a head-mounted display (HMD) is provided, comprising a frame having a mounting space for accommodating a waveguide and a holder with a lens inserted in the holder, wherein the holder is configured for releasable attachment to the frame, wherein the holder comprises a supporting part protruding beyond a lens surface of the lens, when the lens is inserted in the holder, and abutting an adjacent waveguide surface of the waveguide, when the holder with the lens is inserted in the mounting space, so as to provide an air gap between the adjacent waveguide and lens surfaces.

[0013] According to the invention, the technical problem described above is solved by an HMD comprising a frame having a mounting space for accommodating a plurality of optical elements including a waveguide and a holder with a lens, such as a planar or curved waveguide and a prescription lens. The frame may be configured to accommodate one or more further optical elements in addition to the waveguide and the holder with the lens. The holder with the lens in the HMD according to the invention is configured for releasable attachment to the frame. To ensure an air gap between the stacked arrangement of the waveguide and the lens, the holder comprises a supporting part which protrudes beyond a lens surface of the lens, when the lens is inserted in the holder. The supporting part protruding beyond the lens surface of the lens abuts an adjacent waveguide surface of the waveguide, when the holder with the lens is inserted in the mounting space. Thus, the supporting part, and thus, the holder itself acts as a spacer to provide an air gap between the adjacent waveguide and the lens surfaces. No additional airgap enabling elements like separate spacers are needed. The supporting part may extend along the full circumference of the lens. The holder with the supporting part according to the invention further provides a protection to the waveguide preventing direct contact of the lens to the waveguide and thereby mechanical damage of the waveguide.

[0014] The holder of the HMD according to the invention is simple in design and manufacture and ensures effective and simple setting and maintaining a required air gap in-between the lens and the waveguide. The air gap height or thickness is set not by any additional separating element or elements, but by the dimensions of the supporting part, i.e. in essence by the size of the holder in the stacking direction of the stack of waveguide and lens. The dimensions of the holder, in particular of the supporting part of the holder, are comparably easy to control with high precision during the manufacture of the holder, and local, small deviations in the dimensions of the supporting part will not substantially affect the height of the air gap. The supporting part defining the air gap allows avoiding the use of additional separating elements that would require manufacturing and positioning in-between the optical elements with micro-scale precision. In contrast, the holder including its supporting part preferably is a monolithic single component.

[0015] The HMD according to the invention is cost-effective in manufacture, and further allows self-assembly and disassembly at least of the lens of the HMD by a user.

[0016] In the present disclosure, the term "lens" encompasses optical elements of any kind, for example lenses with positive or negative optical power, in particular prescription (Rx) lenses, including progressive lenses, diffractive optical elements, glass plates without optical power, and the like.

[0017] Preferred embodiments of the present invention are defined in the dependent claims and / or are described hereinafter.

[0018] In an embodiment, at least one of the frame and the holder may comprise a fixation structure for snapping the holder with the lens into the mounting space.

[0019] This embodiment has the advantage that attachment of the holder to the frame can be accomplished in a very simple manner. A further advantage is that the position of the holder when snapped into the frame is well defined, in particular it is ensured that the supporting part abuts the waveguide surface to provide the air gap between the waveguide and the lens, while no excessive pressure is exerted to the waveguide. The fixation structureenabling snapping the holder with the lens into the mounting space of the frame not only simplifies the attachment of the holder to the frame, but also allows for a simple detachment of the holder from the frame, for example when the lens is to be exchanged for another lens.

[0020] In a further embodiment, the fixation structure of the frame may comprise one or more protrusions in an inner wall of the frame delimiting the mounting space, wherein the one or more protrusions are formed to enable snapping the holder with the lens into the mounting space and maintaining the holder inside the mounting space.

[0021] The protrusions are easy to manufacture fixation elements of the fixation structure for releasable attachment of the holder in the mounting space. In particular, the protrusions allow for snapping the holder with the lens into the mounting space of the frame and maintain the holder inside the mounting space in a loss-proof manner and in a well-defined position.

[0022] Alternatively or additionally, the fixation structure may comprise one or more frame grooves in an inner wall of the frame, and the holder has one or more frame engaging parts for engaging into the one or more frame grooves, wherein the one or more frame groves and the one or more frame engaging parts are formed to enable snapping the holder with the lens into the mounting space and maintaining the holder inside the mounting space.

[0023] This embodiment also provides for an easy to manufacture fixation structure which enables an easy attachment and detachment of the holder into and from the mounting space of the frame.

[0024] In a further embodiment, the holder may be configured to grip the lens at the periphery of the lens by surface friction and / or form fit.

[0025] The advantage here is that the lens can be manufactured essentially as in a standard process. In particular, the holder and the lens may be detached from each other, as a surfacefriction and / or form fit do not require using e.g. a glue to fix the lens to the holder. Surface friction may be sufficient to avoid rotation of the lens relative to the holder, which may be important for a prescription lens. Also a form fit may be suitable to prevent the lens from rotation relative to the holder.

[0026] In a further embodiment, the lens may have a lens groove and the holder may have a lens engaging part for engaging into the lens groove, when the lens is inserted into the holder.

[0027] The advantage here is that the axial position of the lens relative to the holder, i.e. the position of the lens in direction perpendicular to the lens surface is well defined by the groove and the engaging part of the holder, thereby further simplifying the assembly of the lens with the holder. The manufacture of the lens with a groove is simple essentially as in a standard process, as it needs only making the groove in the side surface or wall of the lens, similar to Nylon rimless frames. The groove may extend over a part or the full circumference of the lens.

[0028] In a further embodiment, the holder may be configured as a ring or tube made of an elastic material and may have an inner circumference in a relaxed, unstretched state, which is smaller than an outer circumference of the lens.

[0029] Such an elastic holder, for example made of a rubber-like material, is advantageous as it can be used with multiple frames and lenses of different sizes within certain size ranges, as the holder can be stretched over the lens circumference and then contracts to grip the lens at its periphery. Further, assembling the lens with the holder can be easily accomplished by stretching the holder over the lens, and then, due to an elastic contraction of the ring or tube, the holder automatically grips the lens. An elastic holder is also advantageous in the context of one or more of the embodiments above, according to which the holder with the lens is snappable into the mounting space of the frame.

[0030] An elastic holder has the further advantage that the waveguide is additionally protected from an excessive pressure that may be exerted to the waveguide when the user pushesthe holder with the lens into the mounting space of the frame. Thus, the waveguide which is an expensive component, is well protected.

[0031] The elastic holder may be extended to a tube-shaped implementation of the holder,wherein only a precision of cross-section dimension (i.e. in the stacking direction of the waveguide and lens) of the tube is important to control during its manufacture, as its outer shape is defined by the lens circumference shape, when the lens is inserted into the elastic holder and the holder is stretched over it.

[0032] In a further embodiment, the supporting part of the holder may be configured to seal the air gap and / or to protect a circumferential edge of the lens.

[0033] Thus, moisture and / or dust is prevented from entering the air gap and thereby from soiling the waveguide in this embodiment.

[0034] In a further embodiment, the holder may comprise a tab for pulling the holder with the lens out of the mounting space of the frame.

[0035] The tab of the holder advantageously provides for an easy extraction of the holder with the lens from the frame, i.e. allows for self-assembly and self-disassembly of the system by a user, for example when the lens is to be exchanged with another lens according to the user prescription. Further, with the tab, the removal and then replacing of the lens is possible through the holder without a touch of the lens itself.

[0036] In a further embodiment, the waveguide may comprise a waveguide package comprising a waveguide substrate and a protective cover encapsulating the waveguide for protection thereof, or the waveguide may comprise a stacked assembly of a waveguide and one or more protection sheets on one or both sides of the waveguide.

[0037] A combination of the holder, in particular when it is provided as an elastic holder, and the waveguide package or stacked waveguide assembly provides for extra protection of thewaveguide to ensure that even higher pressure or accidental impact to the waveguide from the holder side will not damage the waveguide.

[0038] In a further embodiment, the HMD may further comprise a further optical element accommodated in the mounting space of the frame.

[0039] For example, the lens may be arranged on one side of the waveguide, and the further optical element, for example another lens, e.g. another prescription lens, may be arranged on the opposite side of the waveguide. Such another lens may have an optical power to at least partially compensate an optical power of the lens in the holder.

[0040] In the context of the previous embodiment, a further airgap may be provided between the waveguide and the further optical element.

[0041] Further in the context of the previous embodiment, the holder may be configured to hold the further optical element, or the HMD may comprise a further holder for holding the further optical element, wherein the further holder may be configured for releasable attachment to the frame.

[0042] In a further embodiment, the holder may be configured not only to releasably accommodate the lens or lenses as described above, but also to releasably accommodate the waveguide.

[0043] This embodiment may be advantageous if the waveguide itself should be exchangeable for another waveguide, wherein in this case exchanging the waveguide is easy to accomplish, for example by pulling the holder with the lens and the waveguide out of the frame.

[0044] In a further embodiment, the frame may comprise a first frame component and at least a second frame component attachable to the first frame component, wherein the first and at least one second frame components may jointly support the waveguide and the lens when the first and at least one second frame components are attached to each other defining the mounting space.

[0045] A frame comprising at least two frame components attachable to each other may be advantageous, for example if the holder is not an elastic holder or at least a holder which is not enabled for being snapped into the mounting space of the frame and / or for being pulled out of the frame. In this case, the at least two frame components attachable to each other simplifies assembling of the HMD.

[0046] According to a second aspect of the present invention, a holder for a lens is provided, configured for releasable attachment to a frame of an HMD with a waveguide, wherein the holder comprises a supporting part protruding beyond a lens surface of the lens, when the lens is inserted in the holder, and abutting an adjacent waveguide surface of the waveguide, when the holder with the lens is attached to the frame, so as to provide an air gap between the adjacent waveguide and lens surfaces.

[0047] According to a third aspect of the present invention, a method of assembling an HMD is provided, the method comprising:providing a frame comprising a mounting space for accommodating a waveguide;arranging the waveguide in the mounting space;inserting a lens into a holder so that a supporting part of the holder protrudes beyond a lens surface of the lens; andattaching the holder with the lens to the frame so that the supporting part abuts an adjacent waveguide surface of the waveguide, so as to provide an air gap between the adjacent waveguide and lens surfaces.In particular, said inserting the lens into the holder may comprise stretching the holder over a periphery of the lens.Said attaching the holder with the lens to the frame may comprise snapping the holder into the mounting space of the frame.

[0048] It is to be understood that the holder according to the invention and the method according to the invention may have the same or similar advantages and embodiments as described above with respect to the HMD according to the invention.

[0049] Further features and advantages of the invention will become apparent from the following description and the accompanying drawings.

[0050] Embodiments of the invention are shown in the drawings and will be described below with reference to the drawings. In the drawings:Fig. 1 shows a part of an HMD in the form of smartglasses according to an embodiment of the present invention in a perspective view;Fig. 2 shows the HMD of Fig. 1 in a cross-section;Fig. 3 shows a holder of the HMD of Figs. 1 and 2 in isolation in a perspective view;Fig. 4 shows an enlarged view of detail IV in Fig. 2;Fig. 5 shows a detail of another embodiment of the HMD according to the present invention in a view similar to Fig. 4;Fig. 6 shows a step of a method of inserting a lens into an elastic holder according to an embodiment of the present invention;Fig. 7 shows a detail of another embodiment of an HMD according to the invention in a view similar to Fig. 4;Fig. 8 shows a detail of another embodiment of an HMD according to the present invention in a view similar to Fig. 4;Fig. 9 shows a detail of another embodiment of an HMD according to the present invention in a view similar to Fig. 4;Fig. 10 shows a detail of another embodiment of an HMD according to the present invention in a view similar to Fig. 4;Fig. 11 shows a detail of another embodiment of an HMD according to the present invention in a view similar to Fig. 4;Fig. 12 shows a detail of another embodiment of an HMD according to the present invention in a view similar to Fig. 4;Fig. 13 shows a detail of another embodiment of an HMD according to the present invention in a view similar to Fig. 4; andFig. 14 shows a detail of another embodiment of an HMD according to the present invention in a view similar to Fig. 4.

[0051] With reference to Figs. 1 to 4, an embodiment of an HMD in the form of smartglasses labeled with general reference numeral 10 will be described by way of illustrative, non-limiting example. It will be appreciated by those skilled in the art that the present invention is equally implementable in an HMD of any type for AR, VR and MR applications.

[0052] In Fig. 1, a part of a smartglasses 10 is shown for the sake of briefness and clarity. The smartglasses 10 comprises, as main components, a frame 12, a waveguide or waveguide package 14, a lens 16, and a holder 18 for the lens 16. Only a part of the frame 12 is shown in Fig.1 that is designed mainly for accommodating optical components of the smartglasses 10.

[0053] The frame 12 defines a mounting space 20 within the frame 12 for accommodating the waveguide or waveguide package 14. The waveguide package 14 may comprise a planar waveguiding substrate 22 and a protection glass sheet 24 for protecting the waveguidingsubstrate 22. In other embodiments which are not explicitly shown in the drawings, a stacked assembly of a waveguide and one protection glass sheet arranged on one side of the waveguide and another protection glass sheet arranged on the other side, thus sandwiching the waveguide, are possible.

[0054] In the following, the term "waveguide" will encompass a single waveguide, a waveguide package with a waveguiding substrate and a cover glass encapsulating the waveguiding substrate, or a stacked assembly of a waveguide with protection glass sheets, if not described otherwise.

[0055] The lens 16 especially may be a prescription (Rx) lens manufactured in accordance with a prescription of a user to correct for vision defects of the user wearing the smartglasses 10 such as by having corresponding optical power.

[0056] The lens 16 and the waveguide 14 form a stacked arrangement such that the lens 16 and the waveguide 14 overlap each other in a field of view of the wearer of the smartglasses 10.

[0057] An air gap 26 is provided between a lens surface 28 of the lens 16 and a waveguide surface 30 of the waveguide 14 which is required to maintain the conditions of total internal reflection of light guided within the waveguide 14. Another air gap 32 is provided in the present embodiment between the protection glass sheet 24 and the waveguide 22, wherein the air gap 32 is enabled by a spacer 34 fixedly connecting the protection glass sheet 24 and the waveguiding substrate 22 in the peripheral region thereof. Such an arrangement of the waveguiding substrate 22 being separated from the protection glass sheet 24 with an airgap by means of the spacer 34 is shown only as an exemplary illustration. The present invention is not limited to any means for separating and / or stacking the waveguiding substrate and the protection glass sheet.

[0058] As may be appreciated by those skilled in the art, the smartglasses 10 may further comprise an image generator or projector 38, for example, a flat panel display device, such as an LCD module, an LCoS module, an OLED module etc., for providing image light that isusually followed by optics for directing the image light provided by the image generator or projector 38 to the waveguide 14. On the other side, the image generator or projector 38 is provided with a connector 36 to further (not shown) electronics of the smartglasses 10 such as a battery and a processor. The waveguide 14 may comprise, as known to those skilled in the art, an in-coupling structure (not shown) coupling the image light into the waveguide 14, wherein the waveguide 14 guides the image light by total internal reflection to an out-coupling structure (not shown) of the waveguide, which couples the image light out of the waveguide 14 into the eye of a user wearing the smartglasses 10. The stacked arrangement of the lens 16 and the waveguide 14 provide a see-through optical system to transmit image light generated by the projector 38 as a virtual image and environmental light in the field of view of the user to the user’s eye.

[0059] The holder 18 for holding the lens 16 is shown in isolation in Fig. 3. As shown in Fig. 3, the holder 18 is configured as a ring or a short tube. As described with reference to further embodiments below, the holder 18 especially may be made of an elastic material, for example a rubber-like material, for example an elastomer.

[0060] When the lens 16 is inserted into the holder 18 and the holder 18 with the lens 16 is attached to the frame 12, the lens 16 overlaps the waveguide 14 as shown in Fig. 2.

[0061] In the embodiment of Fig. 1 to 4, the tube-shaped holder 18 comprises a supporting part 40 protruding beyond the lens surface 28, when the lens 16 is inserted in the holder 18. When the holder 18 with the lens 16 is attached to the frame 12, i.e. when the holder 18 with the lens 16 is attached in the mounting space 20 within the frame 12, the supporting part 40 abuts the adjacent waveguide surface 30 of the waveguide 14 and, thus, provides the air gap 26 between the adjacent waveguide and lens surfaces 28, 30.

[0062] The holder 18 may be configured to snap into the mounting space 20 of the frame 12, when the holder 18 with the lens 16 is pushed (according to an arrow 42 in Fig. 4) into the mounting space 20 of the frame 12. To be snappable, the holder 18 is made of an elastic material. Further, the holder 18 in the present embodiment comprises a tapering portion 44 in order to facilitate sliding and passing the holder 18 beyond a protrusion 46 at anupper edge of an inner wall of the frame 12. The protrusion 46 is part of a fixation structure for releasable attachment of the holder 18 with the lens 16 in the mounting space 20. In a preferred embodiment the protrusion 46 extends along a part of the periphery circumference of the mounting space 20, i.e. an inner wall of the frame 12, to provide for an easy snapping of the holder 18 with the lens 16 into the mounting space 20. In other words, there are preferably several protrusions 46 distributed along the circumference of the mounting space 20 in the inner wall of the frame 12, for example, as shown in Fig. 2. In another embodiment, the protrusion 46 in the inner wall of the frame 12 is made along the whole circumference of the mounting space 20, but a width of the protrusion 46, i.e. its extent from the inner wall into the mounting space 20, is made less to allow for snapping of the elastic holder 18 with the lens 16 into the mounting space 20. As shown in Fig. 4, as another part of the fixation structure, the holder 18 has, at its end facing away from the waveguide 14, a protrusion 48 abutting the inner side of the protrusion 46 of the frame 12 so that the holder 18 is secured to the frame 12 in a mechanically stable manner.

[0063] The holder 18 grips the lens 16 at a periphery or circumference of the lens 16 by surface friction and / or form fit. In the embodiment of Fig. 1 to 4, the holder 18 grips the lens 16 essentially by a form fit. To this end, the lens 16 has a groove 50 along its full or along a part of its circumference, wherein the lens holder 18 has a lens engaging part 52 adapted to the shape of the groove 50, which engages the groove 50, when the lens 16 is inserted into the holder 18.

[0064] The holder 18 may be shaped as a small rubber-like tube that can be stretched over the circumference edge of the lens 16 to cover it and then grip with the same by contraction, so that a part of the tube, i.e. the supporting part 40 protrudes beyond the lens surface 28 and abuts the waveguide surface 30 so as to act as a spacer to define the air gap 26.

[0065] As shown in Fig. 3, the holder 18 for the lens 16 may comprise a tab or pulling part 54 which a user of the smartglasses 10 can grip to pull the holder 18 with the lens 16 inserted therein out of the frame 12. Thus, the lens 16 can be easily extracted by pulling the tab 54 and thus the holder 18 together with the lens 16 out of the frame 12.

[0066] With reference to Figs. 5 to 14, further embodiments of a smartglasses or an HMD according to the present invention will be described. Throughout Figs. 5 to 14, elements which are identical, similar or comparable with elements in Figs. 1 to 4 are labeled with the same reference numeral. Further, only the differences between the embodiments of Figs. 5 to 14 with the embodiment of Figs. 1 to 4 will be described.

[0067] In the embodiment of Fig. 5, the holder 18 is configured as a ring, wherein the ring has, in cross-section, substantially a C-shape. A first leg 56 of the C-shape of the holder 18 forms a lens engaging part engaging into a groove 50 of the lens 16. A second leg 58 on an opposite side with respect to the leg 56 forms a supporting part 40 of the holder 18 which provides for the air gap 26 between the lens 16 and the waveguide 14. The holder 18 and the frame 12 comprise a fixation structure for releasable attachment of the holder 18 in the mounting space 20 of the frame 12, in particular for snapping the holder 18 into the mounting space 20 of the frame 12, which fixation structure comprises a groove 60 in an inner wall of the frame 12, while the holder 18 has a frame engaging part 62 which engages with form fit into the groove 60 when the holder 18 with the lens 16 is snapped into the mounting space 20 of the frame 12.

[0068] Fig. 6 illustrates, for the embodiment in Fig. 5, the step of inserting the lens 16 into the holder 18. The holder 18 is a ring made of an elastic material which can be stretched to enlarge the diameter of the holder 18. As shown in the upper drawing A in Fig. 6, the elastic holder 18 has, in the relaxed, unstretched state, an inner circumference which is smaller than an outer circumference of the lens 16 shown in the lower drawing C in Fig. 6. From the relaxed, unstretched state shown in the upper drawing A of Fig. 6, the elastic ring-shaped holder 18 can be stretched with applying a certain tensile force according to arrows 64 to a stretched state shown in the middle drawing B of Fig. 6 where the inner circumference of the elastic holder 18 is slightly larger than the outer circumference of the lens 16. In the stretched state, the elastic holder 18 can be put on the outer circumference of the lens 16. In other words, the elastic holder 18 can be stretched over the lens 16. When it is stretched over the lens 16 and released from the tensile force, the holder 18 then grips the lens 16 by contraction. Thus, the holder 18 grips the lens 16 at its periphery by surface friction as shown in the lower drawing C in Fig.6. Furthermore, any parts of the elastic holder 18 free of the grip with the periphery of the lens 16, will tend to elasticcompression to return into an unstretched state. In such way, the legs 56 and 58 of the holder 18 can be formed automatically after the release of the tensile force, by means of the compression of edge parts of the elastic holder 18 around edges of the lens 16 as shown in the lower drawing C in Fig.6. Anyway, the legs 56 and 58, either pre-formed in the elastic holder 18 or formed in result of the compression of edge parts of the elastic holder 18, provide for the form fit of the leg 56 in the groove 50 and the leg 58 gripping around the lens edge onto surface 28, for example, as shown in Fig. 5.

[0069] In the embodiment of Fig. 7, the holder 18 has a shape similar to the shape of the holder 18 in the embodiment of Fig. 5. The frame 12 in this embodiment has a protrusion 46 on its inner wall similar to the protrusion 46 of the frame 12 of the embodiment in Fig. 4. Again, the holder 18 may be an elastic ring suitable for snapping the holder 18 into the mounting space 20 of the frame 12 as described above. It is also possible that the legs 56 and 58 of the holder 18 in this embodiment are formed by means of compression of edge parts of the elastic ring-shaped holder around and over the edges of the lens 16 as described above with reference to Figs. 5 and 6.

[0070] Figs. 8 to 10 show further embodiments which differ from the previous embodiments by the cross-sectional shape of the holder 18 when the lens 16 is inserted into the holder 18. It is preferable that the holder 18 in these embodiments is elastic. In Fig. 8, the holder 18 has substantially a C-shaped cross-section, but without a pre-formed frame engaging part 62 as in Fig. 5. In this embodiment, it is preferred to have the holder 18 made of elastic material with an initial shape (i.e. a shape in a relaxed state) of a ring or short tube with a uniform wall thickness. In that case, the legs 56 and 58 of the holder 18 are formed after such simple elastic tube is stretched over and grips the lens 16 as described above with reference to Fig. 5 and 6. In the embodiment of Fig. 9, the holder 18 has a L-shaped cross-section, when the lens 16 is inserted into the holder 18, wherein the holder 18 grips the lens 16 essentially by surface friction, i.e. the lens 16 does not have a groove like in the embodiments of Fig. 4, 5, and 6. In the embodiment of Fig. 10, the holder 18 has substantially a t-shaped cross-section with the pre-formed lens engaging part 52 that engages the groove 50 in the circumference of the lens 16, when the lens 16 is inserted into the holder 18 like in the embodiment in Fig. 4.

[0071] In all embodiments of Figs. 1 to 10, the holder 18 only accommodates the lens 16, while the waveguide 14 is in direct engagement with the frame 12. Fig. 11 to Fig. 14 instead show embodiments of a smartglasses or HMD 10 in which the holder 18 is designed to not only accommodate the lens 16, but also the waveguide 14.

[0072] Fig. 11 and 12 show two embodiments, in which the holder 18 comprises a supporting part 40 for enabling the air gap 26 between the lens 16 and the waveguide 14, which is positioned not at an end of the holder as in the previous embodiments, but in an intermediate position between the ends of the holder 18. Furthermore, the end of the holder 18 in these embodiments is designed to accommodate the waveguide substrate 22 and the protection glass sheet 24 that are stacked and have the spacer 34 to provide an airgap in-between of them. Namely, the end of the holder 18 grips the stack of the waveguide substrate 22 and the protection glass sheet 24 by surface friction and form fit as shown in Figs. 11 and 12. In the embodiment of Fig. 13, the holder 18 comprises a further supporting part 70 gripping between the waveguiding substrate 22 and the protection glass sheet 24 which provides the air gap 32 between the waveguiding substrate 22 and the protection glass sheet 24 so that the spacer 34 shown in Figs. 11 and 12 can be dispensed with.

[0073] In the embodiment of Fig. 14, a smartglasses or HMD 10 comprises in addition to the lens 16, a further lens 74 as a further optical element in the stack arrangement, wherein the holder 18 accommodates the lens 16, the waveguide 14 and the further lens 74. The waveguide 14 thus is sandwiched between the lens 16 and the further lens 74 which can have an optical power, for example, such that to compensate at least partially for an optical power of the lens 16, or vice versa, to correspond to a prescription of the user in combination with the optical power of the lens 16. A further airgap 76 is provided between the further lens 74 and the waveguide 14, wherein the further airgap 76 is enabled by a further supporting part 78 of the holder 18, which grips between the waveguide 14 and the further lens 74. In the embodiment of Fig. 14, the protection glass sheet 24 may be omitted, as the waveguide 22 is sufficiently protected by the lenses 16 and 74 and the holder 18.

[0074] In all embodiments of Fig. 1 to 14, the frame 12 comprises two components 12a, 12b which are configured to jointly support the optical elements including the lens 16 and thewaveguide 14 and, if present, the further lens 74, by defining the mounting space 20 when the components 12a and 12b are attached to each other. For example, the component 12b may be a main body of the frame 12, and the component 12a may be a cover part of the frame 12 that together clamp the holder 16 and the optical elements in-between thereof when the components 12a, 12b are attached to each other.

[0075] A method of assembling a smartglasses or HMD 10 according to the present invention will be described with respect to the embodiment in Fig. 1 to 4. The method comprises providing the frame 12 comprising the mounting space 20 for accommodating the waveguide 14, and the holder 18, and arranging the waveguide 14 in the mounting space 20. Next, the lens 16 is inserted into the holder 18 as, for example shown in Fig. 6, by stretching the holder 18 over the outer circumference of the lens 16 such that the supporting part 40 protrudes beyond the lens surface 28 of the lens 16. Then, the holder 18 with the lens 16 is attached to the frame 12 by pushing it into the mounting space 20 within the frame such that the holder 18 with the lens 16 snaps into the mounting space 20. When the holder 18 is attached to the frame 12, the supporting part 40 of the holder 18 abuts the adjacent waveguide surface 30 of the waveguide 14, thereby providing the air gap 26 between the waveguide surface 30 and the lens surface 28. As one can see the described method of assembling the smartglasses or HMD 10 is simple and essentially error-resistant so that the smartglasses or HMD 10 can be safely self-assembled by a user without professional assistance.

[0076] It would be appreciated by those skilled in the art that the smartglasses or HMD 10 according to the embodiments of the invention is also subject to a simple disassembling, e.g. by a disassembly procedure reverse to the above-described method of assembling, especially using the tab 54 for pulling the holder 18 with the lens 16 out of the mounting space 20 of the frame 12 in an easy and effective manner. With the described assembly and disassembly methods, the user can quickly and safely replace the lens 16 and / or other optical components of the smartglasses or HMD 10 of the present invention.

Claims

Claims1. A head-mounted display (HMD), comprising a frame (12) having a mounting space (20) for accommodating a waveguide (14) and a holder (18) with a lens (16) inserted in the holder (18), wherein the holder (18) is configured for releasable attachment to the frame (12), wherein the holder (18) comprises a supporting part (40) protruding beyond a lens surface (28) of the lens (16), when the lens (16) is inserted in the holder (18), and abutting an adjacent waveguide surface (30) of the waveguide (14), when the holder (18) with the lens (16) is inserted in the mounting space (20), so as to provide an airgap (26) between the adjacent waveguide and lens surfaces (28, 30).

2. The HMD of claim 1 , wherein at least one of the frame (12) and the holder (18) comprises a fixation structure for snapping the holder (18) with the lens (16) into the mounting space (20).

3. The HMD of claim 2, wherein the fixation structure comprises one or more protrusions (46) in an inner wall of the frame (12) delimiting the mounting space (20), wherein the one or more protrusions (46) are formed to enable snapping the holder (18) with the lens (16) into the mounting space (20) and maintaining the holder(18) inside the mounting space (20).

4. The HMD of any one of claims 2 or 3, wherein the fixation structure comprises one or more frame grooves (60) in an inner wall of the frame (12), and the holder (18) has one or more frame engaging parts (62) for engaging into the one or more frame grooves (60), wherein the one or more frame groves (60) and the one or more frame engaging parts (62) are formed to enable snapping the holder (18) with the lens (16) into the mounting space (20) and maintaining the holder (18) inside the mounting space (20).

5. The HMD of any one of claims 1 to 4, wherein the holder (18) is configured to grip the lens (16) at a periphery of the lens (16) by surface friction and / or form fit.

6. The HMD of any one of claims 1 to 5, wherein the lens (16) has a lens groove (50) and the holder (18) has a lens engaging part (52) for engaging into the lens groove (50), when the lens (16) is inserted into the holder (18).

7. The HMD of any one of claims 1 to 6, wherein the holder (18) is configured as a ring or tube made of an elastic material and has an inner circumference in a relaxed, unstretched state, which is smaller than an outer circumference of the lens (16).

8. The HMD of any one of claims 1 to 7, wherein the supporting part (40) of the holder (18) is configured to seal the airgap (26) and / or to protect a circumferential edge of the lens (16).

9. The HMD of any one of claims 1 to 8, wherein the holder (18) comprises a tab (54) for pulling the holder (18) with the lens (16) out of the mounting space (20) of the frame (12).

10. The HMD of any one of claims 1 to 9, wherein the waveguide (14) comprises a waveguide package comprising a waveguide substrate and a protective cover encapsulating the waveguide for protection thereof, or the waveguide (14) comprises a stacked assembly of a waveguide (22) and one or more protection sheets (24) on one or both sides of the waveguide (22).

11. The HMD of any one of claims 1 to 10, further comprising a further optical element (74) accommodated in the mounting space (20) of the frame (12).

12. The HMD of claim 11 , wherein a further airgap (76) is provided between the waveguide (14) and the further optical element (74).

13. The HMD of claim 11 or 12, wherein the holder (18) is configured to hold the further optical element (74), or the smartglasses comprises a further holder for holding the further optical element (74), wherein the further holder is configured for releasable attachment to the frame.

14. The HMD of any one of claims 1 to 13, wherein the holder (18) is configured to re- leasably accommodate the lens (16) and the waveguide (14).

15. The HMD of any one of claims 1 to 14, wherein the frame (12) comprises a first frame component (12a) and at least a second frame component (12b) attachable to the first frame component (12a), the first and at least one second frame components (12a, 12b) jointly supporting the waveguide (14) and the lens (16) when the first and at least one second frame components (12a, 12b) are attached to each other.

16. A holder for a lens (16), configured for releasable attachment to a frame (12) of a head-mounted display (10) with a waveguide (14), wherein the holder (18) comprises a supporting part (40) protruding beyond a lens surface (28) of the lens (16), when the lens (16) is inserted in the holder (18), and abutting an adjacent waveguide surface (30) of the waveguide (14), when the holder (18) with the lens (16) is attached to the frame (12), so as to provide an airgap (269 between the adjacent waveguide and lens surfaces (28, 30).

17. A method of assembling a head-mounted display (10), the method comprising:providing a frame (12) comprising a mounting space (20) for accommodating a waveguide (14);arranging the waveguide (14) in the mounting space;inserting a lens (16) into a holder (18) so that a supporting part (40) of the holder (18) protrudes beyond a lens surface (28) of the lens (16); andattaching the holder (18) with the lens (16) to the frame (12) so that the supporting part (40) abuts a waveguide surface (30) of the waveguide (14) that is adjacent to the lens surface (28), so as to provide an airgap (26) between the adjacent waveguide and lens surfaces (28, 30).

18. The method of claim 17, wherein said inserting the lens (16) into the holder (18) comprises stretching the holder (18) over a periphery of the lens (16).

19. The method of claim 17 or 18, wherein said attaching the holder (18) with the lens (16) to the frame (12) comprises snapping the holder (18) into the mounting space (20) of the frame.

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