PATENT DOCUMENT

Publication Number: US-12158590-B2
Application Number: US-202318326540-A
Country: US
Kind Code: B2

Title: Lens mounting systems with flexures coupled to the lens

Abstract:
A head-mounted device may include optical assemblies for presenting images to a user. The optical assemblies may each have a display for generating an image and a lens that presents the image to a corresponding eye box for viewing by a user. The optical assemblies may have lens barrels. Each lens barrel may have a first end to which a display is mounted and may have an opposing second end. A mount may be used to attach the lens to the second end of the lens barrel. The mount may have at least one flexure. The flexure may have a U-shaped cross-sectional shape. The mount may have a ring-shaped flexure that extends around a peripheral edge of the lens, may have flexure segments, or may have a set of three discrete flexures located at different positions along the edge of the lens.

Claims:
What is claimed is: 
     
       1. A head-mounted device, comprising:
 a head-mounted housing; 
 optical assemblies in the head-mounted housing that are configured to provide images to eye boxes, wherein each optical assembly includes:
 a display; 
 a lens barrel coupled to the display; 
 a lens, wherein the lens comprises a first material with a first coefficient of thermal expansion; and 
 a flexure coupled between the lens and the lens barrel, wherein the flexure comprises a second material that is different from the first material, and the second material has a second coefficient of thermal expansion that is within 10% of the first coefficient of thermal expansion. 
 
 
     
     
       2. The head-mounted device defined in  claim 1  wherein the lens comprises a catadioptric lens. 
     
     
       3. The head-mounted device defined in  claim 1  wherein the flexure comprises a ring with a U-shaped cross-sectional shape. 
     
     
       4. The head-mounted device defined in  claim 1  wherein the first material comprises a first polymer and wherein the second material comprises a second polymer that is different than the first polymer. 
     
     
       5. The head-mounted device defined in  claim 4  wherein the second polymer comprises polyetherimide. 
     
     
       6. The head-mounted device defined in  claim 5  wherein the first polymer comprises cyclic olefin polymer. 
     
     
       7. The head-mounted device defined in  claim 1  wherein the lens comprises a catadioptric lens with a peripheral edge and wherein the flexure comprises a polymer ring with a U-shaped cross-sectional shape that extends around the peripheral edge. 
     
     
       8. The head-mounted device defined in  claim 7  wherein the lens barrel comprises a metal lens barrel and wherein the catadioptric lens comprises polymer. 
     
     
       9. A head-mounted device optical module, comprising:
 a tube-shaped metal support having opposing first and second ends; 
 a display coupled to the first end; 
 a catadioptric lens having a peripheral edge; and 
 a flexure having a first portion attached to the tube-shaped metal support at the second end, having a second portion attached to the peripheral edge, and having a bend between the first and second portions, wherein the flexure comprises a material having an elastic modulus of at least 2 GPa and a yield strength of at least 70 MPa. 
 
     
     
       10. The head-mounted device optical module defined in  claim 9  wherein the material has a coefficient of thermal expansion that is matched to that of the catadioptric lens within 10%. 
     
     
       11. The head-mounted device optical module defined in  claim 9  further comprising epoxy that attaches the second portion to the peripheral edge. 
     
     
       12. The head-mounted device optical module defined in  claim 9  further comprising epoxy that attaches the first portion to the tube-shaped metal support. 
     
     
       13. The head-mounted device optical module defined in  claim 9  further comprising a screw that attaches the first portion to the tube-shaped metal support. 
     
     
       14. The head-mounted device optical module defined in  claim 13  further comprising a ring-shaped seal between the tube-shaped metal support and the flexure. 
     
     
       15. The head-mounted device optical module defined in  claim 9  wherein the flexure has a U-shaped cross-sectional shape and the material comprises polymer. 
     
     
       16. The head-mounted device optical module defined in  claim 15  wherein the polymer has an elongation-to-failure value of at least 30%. 
     
     
       17. A head-mounted device, comprising:
 a head-mounted housing; 
 optical assemblies in the head-mounted housing that are configured to provide images to eye boxes, wherein each optical assembly includes:
 a display; 
 a lens support coupled to the display; 
 a polymer catadioptric lens; and 
 a lens mount having a set of three flexures, each coupled between the polymer catadioptric lens and the lens support at a different location along a peripheral edge of the polymer catadioptric lens. 
 
 
     
     
       18. The head-mounted device defined in  claim 17  wherein the lens support comprises a metal lens support having a tubular shape and wherein at least one flexure of the set of the three flexures comprises a polymer ring with a U-shaped cross-sectional shape.

Description:
This application claims the benefit of provisional patent application No. 63/431,394, filed Dec. 9, 2022, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices, and, more particularly, to electronic devices such as head-mounted devices. 
     BACKGROUND 
     Electronic devices such as head-mounted devices have displays that generate images and lenses that are used in presenting the images to users. Components such as lenses may be sensitive to stress, which raises challenges when mounting lenses in head-mounted devices. 
     SUMMARY 
     A head-mounted device may include optical assemblies for presenting images to a user. The optical assemblies may each have a display for generating an image and a lens that presents the image to a corresponding eye box for viewing by a user. The lens may be a catadioptric lens with polymer lens elements that exhibit stress-induced birefringence when subjected to excessive stress. 
     The optical assemblies may have lens barrels. Each lens barrel may have a first end to which a display is mounted and may have an opposing second end. A lens mount that helps reduce stress in the lens may be used to attach the lens to the second end of the lens barrel. The mount may have at least one flexure. The flexure may have a U-shaped cross-sectional shape. The mount may have a ring-shaped flexure that extends around a peripheral edge of the lens, may have flexure segments, or may have a set of three discrete flexures located at different positions along the edge of the lens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram of an illustrative head-mounted device in accordance with an embodiment. 
         FIG.  2    is a front view of an illustrative lens in accordance with embodiments. 
         FIGS.  3  and  4    are cross-sectional side view of peripheral portions of illustrative lenses and associated mounting structures in accordance with embodiments. 
         FIGS.  5  and  6    are top views of illustrative flexures for mounting a lens in accordance with embodiments. 
         FIGS.  7 ,  8 ,  9 , and  10    are cross-sectional side views of additional illustrative flexure arrangements for mounting a lens in accordance with embodiments. 
         FIG.  11    is a diagram showing how adhesive may be introduced into a gap between an illustrative flexure and a lens in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as head-mounted devices may have displays for displaying images and lenses that are used in presenting the images to eye boxes for viewing by a user. The lenses may be mounted in a head-mounted device using support structures that help minimize lens stress. In an illustrative embodiment, the lenses are mounted in rigid lens supports such as metal lens barrels using lens mounts based on flexures. The flexures help prevent stress from being applied to the lenses even when the electronic devices are subjected to changes in operating temperature that cause the lenses to expand and contract. 
       FIG.  1    is a schematic diagram of an illustrative electronic device of the type that may include lenses mounted with flexures. Device  10  of  FIG.  1    may be a head-mounted device (e.g., goggles, glasses, a helmet, and/or other head-mounted device. In an illustrative configuration, device  10  is a head-mounted device such as a pair of goggles (sometimes referred to as virtual reality goggles, mixed reality goggles, augmented reality glasses, etc.). 
     As shown in the illustrative cross-sectional top view of device  10  of  FIG.  1   , device  10  may have a housing such as housing  12  (sometimes referred to as a head-mounted support structure, head-mounted housing, or head-mounted support). Housing  12  may include a front portion such as front portion  12 F and a rear portion such as rear portion  12 R. When device  10  is worn on the head of a user, rear portion  12 R rests against the face of the user and helps block stray light from reaching the eyes of the user. 
     Main portion  12 M of housing  12  may be attached to head strap  12 T. Head strap  12 T may be used to help secure main portion  12  on the head and face of a user. Main portion  12 M may have a rigid shell formed from housing walls of polymer, glass, metal, and/or other materials. When housing  12  is being worn on the head of a user, the front of housing  12  may face outwardly away from the user and the rear of housing  12  (and rear portion  12 R) may face towards the user. In this configuration, rear portion  12 R may face the user&#39;s eyes located in eye boxes  36 . 
     Device  10  may have electrical and optical components that are used in displaying images to eye boxes  36  when device  10  is being worn. These components may include left and right optical assemblies  20  (sometimes referred to as optical modules). Each optical assembly  20  may have an optical assembly support  38  (sometimes referred to as a lens barrel, optical module support, or support structure). Supports  38  may have hollow tubular shapes or other suitable shapes. Optical assemblies  20  may slide laterally along guide rails to adjust optical-assembly-to-optical-assembly separation to accommodate different user interpupillary distances. Rear portion  12 R may include flexible structures (e.g., a flexible polymer layer, a flexible fabric layer, etc.) so that portion  12 R can stretch to accommodate movement of assemblies  20 . 
     Each assembly  20  may have a display  32  coupled to one end of support  38  and a lens mounted to an opposing end of support  38 . Display  32  has an array of pixels for displaying images. Lens  34  may optionally have a removable vision correction lens for correcting user vision defects (e.g., refractive errors such as nearsightedness, farsightedness, and/or astigmatism). During operation, images displayed by displays  32  may be presented to eye boxes  36  through lenses  34  for viewing by the user. 
     To help satisfy design constraints (e.g., low weight, compact size, wide field of view, high resolution, etc.), lenses  34  may be catadioptric lenses. A catadioptric lens incorporates optical components such as polarizers and wave plates to create a folded optical path that can help reduce lens size. The use of these polarization-sensitive optical components may, however, make lenses  34  sensitive to performance degradation due to stress-induced birefringence effects. Lenses  34  may, as an example, include lens elements formed from polymers (for example, COC polymer (cyclic olefin copolymer) or other suitable polymers) that help minimize lens weight, but these polymers may exhibit birefringence when subjected to excess stress. 
     Satisfactory operation for lenses  34  may be achieved by mounting lenses  34  using lens mounts that help isolate lenses  34  from sources of stress. In an illustrative configuration, supports  38  may be formed from strong rigid materials such as metal (e.g., aluminum, etc.). When operating device  10  over wide temperature ranges (e.g., 0-50° C.), there is a risk that expansion and contraction of materials in assemblies  20  and, more particularly, mismatches in the coefficient of thermal expansion between the polymer of lenses  34  and the metal of supports  38 , can give rise to unwanted stress in lenses  34 , leading to unwanted stress-induced birefringence in lenses  34 . Unwanted temperature-change-induced stress may be avoided by mounting lenses  34  within supports  38  using lens mounts based on flexures. 
       FIG.  2    is a front view of an illustrative lens for device  10 . A shown in  FIG.  2   , lens  34  may be surrounded by flexible lens mount  40 . Lens mount  40  may include one or more flexures. In an illustrative embodiment, lens mount  40  contains a ring-shaped flexure that runs around the entire perimeter of lens  34 . Arrangements in which mount  40  includes a number of separate segments (see, e.g., illustrative segment SG) each of which has a separate strip-shaped flexure segment or in which mount  40  includes discrete flexures such as illustrative discrete flexure DL (e.g., a set of three discrete flexures attached to the periphery of lens  34  at three evenly spaced locations along the periphery) may also be used. Support  38  may be attached to mount  40  along the outer peripheral edge of mount  40  or support  38  may be attached to mount  40  where support  38  overlaps mount  40  (sec, e.g.,  FIG.  3   ). 
       FIG.  3    is a cross-sectional side view of an illustrative peripheral portion of lens  34  and mount  40  of  FIG.  2    taken along line  42  of  FIG.  2    and viewed in direction  44 . As shown in  FIG.  3   , support (lens barrel)  38  may be overlapped by mount  40 . Mount  40  may be formed from polymer, metal, or other material that is shaped to form a flexure. In the example of  FIG.  3   , mount  40  is a ring-shaped flexure with a U-shaped cross section that runs along the ring-shaped peripheral edge of lens  34 . First portion  40 - 1  of the flexure is attached to the peripheral edge of lens  34  with a first ring of adhesive  50  and second portion  40 - 2  of the flexure is attached to support  38  with a second ring of adhesive  52 . Bend  40 - 3  runs along mount  40  between portions  40 - 1  and  4 - 2  and allows mount  40  to flex. For example, portion  40 - 1  may move radially outwardly towards portion  40 - 2  when lens  34  expands radially due to an increase in operating temperature. The metal of support  38  has a significantly lower coefficient of thermal expansion than the polymer of lens  34 , but is separated by an air gap from the edge of lens  34 , so that lens  34  can expand radially outwardly without contacting support  38  and is therefore not stressed due to pressure from contact with support  38 . 
     Mount  40  may, if desired, be formed from a material such as polyetherimide (PEI) or other rigid polymer that exhibits a high yield strength and a high elongation-to-failure value. The elastic modulus of the material forming mount  40  may be, for example, at least 1.5 GPa, at least 2 GPa, or at least 3 GPa, as examples. The high strength and high rigidity of the material forming mount  40  helps mount  40  accurately hold lens  34  in place. The material of mount  40  may exhibit a yield strength (e.g., at least 30 MPa, at least 70 MPa, or at least 100 MPa), so that mount  40  exhibits a good yield-strength-to-stiffness ratio. To provide mount  40  with satisfactory durability, it may be desirable for the material of mount to have an elongation-to-failure value of at least 25%, at least 35%, or at least 40%. To ensure satisfactory attachment of mount  40  with adhesive  52  and  50 , the material of mount  40  preferably also exhibits satisfactory compatibility (bond strength) with adhesives  52  and  50 . Adhesives  52  and  50  may be, for example, epoxy, so the material of mount  40  preferably forms satisfactory bonds with epoxy. The coefficient of thermal expansion of the material of mount  40  may be matched (e.g., within 20%, within 10%, within 5%, or within 2%) to the coefficient of thermal expansion of the material of lens  34 . In this way, lens stress can be avoided that might otherwise be imposed by mount  40  on lens  34  if, for example, the perimeter of mount  40  were to expand less quickly than the perimeter of lens  34  as a function of increasing operating temperature and thereby constrain the expansion of lens  34 . Other types of materials may be used in forming mount  40 , if desired. The use of polyetherimide that is matched to the polymer of lens  34  in its coefficient of thermal expansion and that exhibits high yield strength and high elongation-to-failure values is illustrative. 
     If desired, thermally induced lens stress may be minimized using a reverse flange adhesive attachment arrangement of the type shown in  FIG.  4   . With this type of arrangement, lens  34  may be provided with a milled flange that is bonded to a surface of support  38  that faces radially outward (away from lens  34 ). As shown in  FIG.  4   , adhesive  50  (e.g., a soft adhesive) may be used to attach outwardly facing surface  53  of support  38  to opposing inwardly faced milled flange surface  54  of lens  34 . An air gap such as air gap  56  is preferably present between outer peripheral edge surface  58  of lens  34  and opposing inwardly facing surface  60  of support  38 , thereby ensuring that the periphery of lens  34  (surface  58 ) will not contact support  38  and will therefore not receive stress from support  38  even as lens  34  expands radially outward as a function of increasing operating temperature. 
     If desired a set of discretely located flexures such as the illustrative flexures of  FIGS.  5  and  6    may also be used in supporting lens  34  (e.g., at three points along the perimeter of lens  34 ). In the examples of  FIGS.  5  and  6   , lens  34  is viewed from the rear of device  10  (e.g., along the Z axis). One side of illustrative flexures  64  and  66  may be attached to the periphery of lens  34  using adhesive  68  and another side of flexures  64  and  66  may be attached to support  38  (e.g., using adhesive, screws or other fasteners, etc.). During fluctuations in operating temperature, lens  34  may expand radially outward and may contract radially inward. With the flexure arrangements of  FIGS.  5  and  6   , flexures  64  and  66  may radially flex to accommodate the lens expansion and contraction, while accurately maintaining a desired mounting location for lens  34  within support  38 . In arrangements in with flexures are located at discrete locations around the periphery of lens  34  (e.g., three discrete locations), sealing structures (e.g., ring-shaped elastomeric boots) may be used to help seal the periphery of lens  34  against support  38  and thereby prevent dust and moisture ingress into assembly  20 . As with the ring-shaped flexure of  FIGS.  2  and  3   , the discrete flexures of  FIGS.  5  and  6    may be used to maintain lens  34  in a satisfactory position (without significant lateral shifting in X and Y position and without significant tilt away from the Z axis) while flexing to accommodate expansion and contraction due to temperature changes. The strength of mount  40  may help assemblies  20  resist plastic deformation and other damage during drop events and other undesired impacts leading to excessive stress. 
       FIGS.  7 ,  8 ,  9 , and  10    are illustrative cross-sectional side views of illustrative flexures for mount  40 . The flexures of  FIGS.  7 ,  8 ,  9 , and  10    may extend in a continuous ring around the periphery of lens  34 , may be formed from a number of segments that extend around lens  34 , or may be formed from discretely located flexures (as shown, for example, in  FIGS.  5  and  6   ). In the arrangements of  FIGS.  7 ,  8 , and  9   , mount  40  has a U-shaped cross-sectional shape. 
     In the example of  FIG.  7   , screw  70  attaches mount (flexure)  40  to support  38  and adhesive  78  attaches mount  40  to lens  34 . When using a screw such as screw  70  to attach mount  40  to support  38  instead of adhesive, a separate seal such as seal  72  may be used to seal lens  34  to support  38  and thereby help prevent moisture and dust ingress into the interior of assembly  20 . Seal  72  may be an O-ring formed from an elastomeric gasket material, may be a ring of adhesive (e.g., pressure sensitive adhesive or other soft sealing adhesive), or may be other sealant. If desired, adhesive  76  may be provided at the interface between mount  40  and support  38  (e.g., epoxy or other rigid adhesive) and may be used both to attach mount  40  to support  38  and to seal mount  40  to support  38 . The use of screws such as screw  70  of  FIG.  7    to attach mount  40  to support  38  is illustrative. 
     The illustrative configurations of  FIGS.  8 ,  9 , and  10    may also involve the use of screws  70 , adhesive  76 , and/or seal  72  to attach and seal mount  40  to support  38 . In the example of  FIG.  8   , mount  40  protrudes inwardly under the outer edge of lens  34 . In the example of  FIG.  9   , screw  70  extends radially inward towards the center of lens  34 . In the example of  FIG.  10   , the flexure formed by mount  40  does not have a central bend, but rather relies on its length to ensure that sufficient flexure bending is available to accommodate radial outward expansion of lens  34  as operating temperatures rise. 
     The diagram of  FIG.  11    shows how adhesive  78  may be dispensed to attach mount  40  to the outer edge of lens  34 . In the example of  FIG.  11   , lens  34  and mount  40  have been flipped upside down relative to the orientation of  FIG.  3   . As shown in  FIG.  11   , mount  40  may have a chamfer such as chamfer  84  that locally widens the gap between lens  34  and mount  40  to facilitate the introduction of liquid adhesive into this gap. Adhesive may be dispensed in liquid form in direction  82  from dispenser  80  and may then be drawn into the gap between mount  40  and lens  34  by capillary action. After the liquid adhesive material has been drawn into the gap, the adhesive may be cured to form adhesive  78  (e.g., using ultraviolet light curing, curing using a two-part adhesive arrangement, etc.). To help control the downward progress of adhesive  78  while adhesive  78  is liquid, mount  40  may be provided with a stop feature such as step  86 . The presence of step  86  on the inwardly facing surface of mount  40  creases a surface tension break that stops the downward flow of adhesive  78  when flowing into the joint between lens  34  and mount  40 . In this way, the dispensing of adhesive  78  may be limited to a desired bonding area between mount  40  and lens  34 . 
     To help protect the privacy of users, any personal user information that is gathered by device  10  may be handled using best practices. These best practices including meeting or exceeding any privacy regulations that are applicable. Opt-in and opt-out options and/or other options may be provided that allow users to control usage of their personal data. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20230531
Publication Date: 20241203
Grant Date: 20241203
Priority Date: 20221209
Inventors: TREKELL, BLAKE N
ZIMMERMAN, AIDAN N
OLDENBO, Clas Magnus Oscar
NICHOLS, ANDREW
ADEBAYO, Ransomed I
PILARZ, Peter
MELROSE, JESSE
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B2027/0159", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B7/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B7/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0169", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0176", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0176", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B2027/0159", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B7/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0176", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 89122147