A lens module containing two lens elements separated by an air gap

Abstract

The head mounted display may include a display system and an optical system supported by a housing. The optical system may be a catadioptric optical system having a removable lens element and a non-removable lens element. The optical system may include a quarter wave plate coated on the non-removable lens element without an intervening adhesive layer. The optical system may further include a reflective polarizer and a linear polarizer. The removable lens element may be selectively attached to the optical system. The removable lens element may be separated from the non-removable lens element by an air gap when the removable lens element is attached to the optical system. The removable lens element may have a convex curved surface that matches a concave curved surface of the non-removable lens element.

Description

[Technical Field]

[0001] This application relates generally to optical systems, and more particularly to optical systems for head-mounted displays. (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 274,398, filed November 1, 2021, which is incorporated by reference herein in its entirety. [Background technology]

[0002] Head-mounted displays, such as virtual reality glasses, use lenses to display images to a user. A microdisplay can generate an image for each of the user's eyes. A lens can be provided between each of the user's eyes and a portion of the microdisplay, allowing the user to view virtual reality content.

[0003] If care is not taken, head-mounted displays can be cumbersome and tiring to wear. Optical systems for head-mounted displays can use large and heavy lens arrangements. Extended use of head-mounted displays using this type of optical system can be uncomfortable.

[0004] It would therefore be desirable to be able to provide an improved head mounted display. Summary of the Invention

[0005] A head-mounted display can include a display system and an optical system. The display system and the optical system can be supported by a housing that is worn on a user's head. The head-mounted display can present images to a user using the display system and the optical system while the housing is worn on the user's head.

[0006] The display system can have a pixel array that generates image light associated with an image. The display system can have a linear polarizer through which the image light from the pixel array passes, and a quarter-wave plate through which the light passes after passing through the linear polarizer.

[0007] The optical system may be a catadioptric optical system having at least a first lens element and a second lens element. The optical system may include a quarter wave plate coated on the first lens element without an intervening adhesive layer. The optical system may further include a reflective polarizer and a linear polarizer.

[0008] The second lens element may be a removable lens element configured to be selectively attached to the optical system. The second lens element may include one or more mounting structures configured to be attached to corresponding mounting structures included on the first lens element or to a support structure within the device. The second lens element may be separated from the first lens element by an air gap when the second lens element is attached to the optical system.

[0009] The second lens element may have a convex surface that matches the curvature of the concave surface of the first lens element, and the minimum radius of curvature of the convex surface of the second lens element may be within 20% of the minimum radius of curvature of the concave surface of the first lens element. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram of an exemplary head-mounted display according to one embodiment.

[0011] [Figure 2] FIG. 1 is a diagram of an exemplary head-mounted display illustrating components of an exemplary optical system within the head-mounted display, according to one embodiment.

[0012] [Figure 3]3 is a cross-sectional side view of an exemplary head-mounted display illustrating how the polarization of light changes as it passes through the optical system of FIG. 2 in accordance with one embodiment.

[0013] [Figure 4] FIG. 2 is a top view of an exemplary lens element with a mounting structure on the top surface, according to one embodiment.

[0014] [Figure 5] 1 is a cross-sectional side view of an exemplary lens element having an edge surface with mounting structures according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Head-mounted displays can be used in virtual reality and augmented reality systems, for example, to provide virtual reality and / or augmented reality content to a user using a pair of virtual reality glasses worn on the user's head.

[0016] An exemplary system in which an electronic device (e.g., a head-mounted display such as a pair of virtual reality glasses) is used in providing virtual reality to a user is shown in Figure 1. As shown in Figure 1, virtual reality glasses 10 (sometimes referred to as glasses 10, electronic device 10, head-mounted display 10, device 10, etc.) can include a display system such as display system 40 that generates images and can have an optical system such as optical system 20 that allows a user (see, e.g., user's eyes 46) to view the images generated by display system 40 by looking in direction 48.

[0017] Display system 40 (sometimes referred to as display panel 40 or display 40) can be based on a liquid crystal display, an organic light emitting diode display, an emissive display having an array of crystalline semiconductor light emitting diode dies, and / or a display based on other display technologies. System 40 may include separate left and right displays for the user's left and right eyes, or a single display may span both eyes.

[0018] Visual content (e.g., image data for still and / or moving images) can be provided to the display system (display) 40 using control circuitry 42 attached to the glasses (head-mounted display) 10 and / or control circuitry attached external to the glasses 10 (e.g., within an associated portable electronic device, laptop computer, or other computing equipment). The control circuitry 42 can include storage devices such as hard disk storage devices, volatile and non-volatile memory, electrically programmable storage devices for forming solid-state drives, and other memory. The control circuitry 42 can also include one or more microprocessors, microcontrollers, digital signal processors, graphics processors, baseband processors, application-specific integrated circuits, and other processing circuitry. Communications circuitry within the circuitry 42 can be used to send and receive data (e.g., wirelessly and / or via wired paths). The control circuitry 42 can use the display system 40 to display visual content such as virtual reality content (e.g., computer-generated content associated with a virtual world), pre-recorded video of a movie or other medium, or other images. An exemplary configuration in which the control circuitry 42 provides virtual reality content to a user using the display system 40 may be described herein by way of example. In general, however, the display system 40 and optical system 20 of the glasses 10 may be used by the control circuitry 42 to present any suitable content to the user.

[0019] The input / output device 44 can be coupled to the control circuitry 42. The input / output device 44 can be used to collect user input from a user, can be used to make measurements about the environment surrounding the glasses 10, can be used to provide output to a user, and / or can be used to provide output to external electronics. The input / output device 44 can include buttons, joysticks, keypads, keyboard keys, touch sensors, trackpads, displays, touchscreen displays, microphones, speakers, light-emitting diodes for providing visual output to a user, sensors (e.g., force sensors, temperature sensors, magnetic sensors, accelerometers, gyroscopes, and / or other sensors for measuring the orientation, position, and / or movement of the glasses 10, proximity sensors, capacitive touch sensors, strain gauges, gas sensors, pressure sensors, ambient light sensors, and / or other sensors). Optionally, the input / output device 44 can include one or more cameras / optical sensors (e.g., a camera for capturing images of the user's surroundings, a camera for performing gaze detection operations by viewing the eyes 46, and / or other cameras).

[0020] 2 is a cross-sectional side view of eyeglasses 10 illustrating how optical system 20 and display system 40 can be supported by a head-mounted support structure, such as housing 12 of eyeglasses 10. Housing 12 may have the shape of a frame for a pair of eyeglasses (e.g., eyeglasses 10 may resemble glasses), the shape of a helmet (e.g., eyeglasses 10 may form a helmet-mounted display), the shape of goggles, or any other suitable housing shape that allows housing 12 to be worn on a user's head. A configuration in which housing 12 supports optical system 20 and display system 40 in front of a user's eyes (e.g., eyes 46) when the user views system 20 and display system 40 in direction 48 may be described herein by way of example. Housing 12 can have other desired configurations, if desired.

[0021] The housing 12 may be formed from plastic, metal, fiber composite materials such as carbon fiber materials, wood and other natural materials, glass, other materials, and / or combinations of two or more of these materials.

[0022] The input / output devices 44 and control circuitry 42 may be mounted in the housing 12 along with the optical system 20 and the display system 40, and / or portions of the input / output devices 44 and control circuitry 42 may be coupled to the glasses 10 using cables, wireless connections, or other signal paths.

[0023] The display system 40 and the optical components of the glasses 10 can be configured to display images to the user 46 using a lightweight and compact configuration. The optical system 20 may be based, for example, on a catadioptric lens (e.g., a lens that uses both reflection and refraction of light).

[0024] The display system 40 may include an image source, such as a pixel array 14. The pixel array 14 may include a two-dimensional array of pixels P that emit image light (e.g., organic light-emitting diode pixels, light-emitting diode pixels formed from a semiconductor die, liquid crystal display pixels with a backlight, liquid crystal on silicon pixels with a frontlight, etc.). A polarizer, such as a linear polarizer 16, may be disposed in front of the pixel array 14 and / or laminated to the pixel array 14 to provide polarized image light. The linear polarizer 16 may have a pass axis aligned with the X-axis of FIG. 2 (for example). The display system 40 may also include a wave plate, such as a quarter-wave plate 18, to provide circularly polarized image light. The fast axis of the quarter-wave plate 18 may be aligned at 45 degrees to the pass axis of the linear polarizer 16. The quarter-wave plate 18 may be mounted in front of the polarizer 16 (between the polarizer 16 and the optical system 20). If desired, a quarter wave plate 18 can be attached to the polarizer 16 (and the display 14).

[0025] The optical system 20 may include a lens element, such as lens element 26. Lens element 26 may be formed from a transparent material, such as plastic or glass. Lens element 26 may have a surface S1 facing the display system 40 and a surface S2 facing a user (e.g., eye 46). Surface S1 may be convex (e.g., spherically convex, cylindrically convex, or aspherically convex), concave (e.g., spherically concave, cylindrically concave, or aspherically concave), or a free-form surface. A free-form surface may include both convex and concave portions. Alternatively, a free-form surface may have varying convex or concave curvatures (e.g., different portions with different radii of curvature, portions with curvature in one direction, and portions with curvature in two directions, etc.). As used herein, a free-form surface that is primarily convex (e.g., a surface that is mostly convex and / or a surface that is convex at its center) may still be referred to as a convex surface, and a free-form surface that is primarily concave (e.g., a surface that is mostly concave and / or a surface that is concave at its center) may still be referred to as a concave surface. Surface S2 may be a convex surface (e.g., a spherically convex, cylindrically convex, or aspherically convex), a concave surface (e.g., a spherically concave, cylindrically convex, or aspherically concave), or a free-form surface.

[0026] A spherically curved surface (e.g., a spherically convex surface or a spherically concave surface) may have a constant radius of curvature across the surface. In contrast, an aspherically curved surface (e.g., an aspherically concave surface or an aspherically convex surface) may have a radius of curvature that varies across the surface. A cylindrical surface may be curved only around one axis, rather than around multiple axes as a spherical surface. In some cases, one of the lens surfaces may have an aspherical surface that changes from convex (e.g., at the center) to concave (e.g., at the edge) at different locations on the surface. This type of surface is sometimes referred to as an aspherical surface, a predominantly convex (e.g., a surface in which the majority of the surface is convex and / or the surface is convex at its center) aspherical surface, a freeform surface, and / or a predominantly convex (e.g., a surface in which the majority of the surface is convex and / or the surface is convex at its center) freeform surface. In one exemplary configuration shown in FIG. 2, surface S1 is an aspherically convex surface and surface S2 is an aspherically concave surface. This configuration may be described herein as an example.

[0027] Optical structures such as partially reflective coatings, wave plates, reflective polarizers, linear polarizers, anti-reflective coatings, and / or other optical components can be incorporated into eyeglasses 10 (e.g., system 20) that allow light rays from display system 40 to pass through and / or reflect from surfaces in optical system 20, such as surfaces S1 and S2, thereby providing optical system 20 with the desired lens power.

[0028] An exemplary arrangement of optical layers is shown in Figure 2. The structural arrangement of these layers will be described first, and the function of these layers will be discussed in more detail in connection with Figure 3.

[0029] 2, a partially reflective mirror such as partially reflective mirror 22 (e.g., a metallic mirror coating or other mirror coating such as a dielectric multilayer coating having 50% transmission and 50% reflection) can be formed on the aspherical convex surface S1 of lens element 26. Partially reflective mirror 22 may also be referred to as a beam splitter 22, a half mirror 22, or a partially reflective layer 22.

[0030] A wave plate, such as wave plate 28, may be formed on the aspherical concave surface S2 of lens element 26. Wave plate 28 (sometimes referred to as retarder 28, quarter wave plate 28, etc.) may be a quarter wave plate that conforms to surface S2 of lens element 26. Retarder 28 may be a coating on surface S2 of lens element 26.

[0031] The reflective polarizer 30 may be attached to the retarder 28 using an adhesive layer 32. The reflective polarizer 30 may have orthogonal reflection and pass axes. Light polarized parallel to the reflection axis of the reflective polarizer 30 is reflected by the reflective polarizer 30. Light polarized perpendicular to the reflection axis, and therefore parallel to the pass axis of the reflective polarizer 30, passes through the reflective polarizer 30. The adhesive layer 32 may be a layer of optically clear adhesive (OCA).

[0032] The polarizer 34 may be attached to the reflective polarizer 30 using an adhesive layer 36. The polarizer 34 may be a linear polarizer. The polarizer 34 is sometimes referred to as an external block linear polarizer 34 or a clean-up polarizer 34. The linear polarizer 34 may have a pass axis aligned with the pass axis of the reflective polarizer 30. The linear polarizer 34 may have a pass axis orthogonal to the pass axis of the linear polarizer 16. The adhesive layer 36 may be a layer of optically clear adhesive (OCA).

[0033] Optical system 20 may include additional lens elements, such as lens element 84. Lens element 84 may be formed from a transparent material, such as plastic or glass. Lens element 84 may have a surface S3 facing display system 40 and a surface S4 facing a user (e.g., eye 46). Surface S3 may be convex (e.g., spherically convex, cylindrically convex, or aspherically convex), concave (e.g., spherically concave, cylindrically concave, or aspherically concave), or a free-form surface. Surface S4 may be convex (e.g., spherically convex, cylindrically convex, or aspherically convex), concave (e.g., spherically concave, cylindrically concave, or aspherically concave), or a free-form surface.

[0034] 2, surface S3 of lens element 84 faces surface S2 of lens element 26. Surface S3 may have a convex curvature that matches the shape of the concave curvature of surface S2. Surface S4 may have a concave curvature.

[0035] In one possible configuration, the lens element 84 may be a removable lens element. In other words, a user can easily remove and replace the lens element 84 within the optical system 20. This allows the lens element 84 to be customizable. If the lens element 84 were permanently fixed to the optical system, the lens power provided by the lens element 84 could not be easily changed. However, by making the lens element 84 customizable, a user can select the lens element 84 that best suits their eyes and place the appropriate lens element 84 within the optical system. The lens element 84 may be used, for example, to accommodate a user's eyeglass prescription. A user may replace the lens element 84 with an updated lens element if their eyeglass prescription changes (without having to replace any of the other components within the device 10). The lens element 84 may have a variable lens power and / or provide a variable amount of astigmatism correction to provide prescription correction for the user.

[0036] In contrast to lens element 84, lens element 26 does not have to be a removable lens element. Accordingly, lens element 26 may be referred to as a permanent lens element, a fixed lens element, or a non-removable lens element. The example of lens element 26 being a non-removable lens element is merely illustrative. In another possible configuration, lens element 26 may be a removable lens element (similar to lens element 84).

[0037] An air gap 102 may exist between lens element 84 and lens element 26 (and other layers on lens element 26). To improve the performance of the optical system, the curvature of surface S3 of lens element 84 may approximately match the curvature of surface S2 of lens element 26. As a result, surface S3 matches surface S2 (and other layers on surface S2, such as layers 28, 32, 30, 36, and 34, that have the same curvature as surface S2). In this manner, matching the curvature of surface S3 to the curvature of surface S2 of lens element 26 allows the user's eyes to be positioned closer to the optical system during operation than if lens 84 had a flatter, non-conforming surface. Positioning the user's eyes closer to the optical system improves the user's field of vision during operation of the system. Thus, the curvature of surface S3 allows the user to experience an improved field of vision.

[0038] The radius of curvature of surface S3 of lens element 84 may vary across the lens element (e.g., an aspherical lens element as in FIG. 2) or may be constant. The radius of curvature may vary in magnitude and / or sign. The minimum radius of curvature of surface S3 may be less than 15 millimeters, less than 20 millimeters, less than 25 millimeters, less than 30 millimeters, less than 35 millimeters, less than 40 millimeters, less than 50 millimeters, greater than 20 millimeters, between 25 millimeters and 30 millimeters, etc. Similarly, the minimum radius of curvature of surface S2 of lens element 26 may be less than 15 millimeters, less than 20 millimeters, less than 25 millimeters, less than 30 millimeters, less than 35 millimeters, less than 40 millimeters, less than 50 millimeters, greater than 20 millimeters, between 25 millimeters and 30 millimeters, etc. The magnitude of the minimum radius of curvature of surface S3 may be within 1% of the magnitude of the minimum radius of curvature of surface S2, within 5% of the magnitude of the minimum radius of curvature of surface S2, within 10% of the magnitude of the minimum radius of curvature of surface S2, within 20% of the magnitude of the minimum radius of curvature of surface S2, within 50% of the magnitude of the minimum radius of curvature of surface S2, between 1% and 20% of the magnitude of the minimum radius of curvature of surface S2, etc. The sign of the radii of curvature may be changed as desired (e.g., changing from a convex curvature to a concave curvature or vice versa).

[0039] Because surface S3 approximately matches the curvature of surface S2, the width of air gap 102 may be approximately constant across the lens element. As a particular example, the thickness of the air gap across surface S3 of lens element 84 may be uniform to within 100%, within 50%, within 20%, within 10%, within 5%, within 3%, within 2%, within 1%, etc. The variation in the thickness of the air gap across surface S3 may be less than 50%, less than 20%, less than 10%, less than 5%, less than 3%, less than 2%, less than 1%, etc.

[0040] One or more additional coatings 38 may also be included in optical system 20 (sometimes referred to as lens 20, lens assembly 20, or lens module 20). Coatings 38 may include an anti-reflective coating (ARC), an anti-soiling (AS) coating, or any other desired coating. In the example of FIG. 2, coating 38 is formed on surface S4 of removable lens element 84.

[0041] Figure 3 is a cross-sectional side view of exemplary optical system 20 and display system 40, showing how light from the display passes through the optical system of Figure 2. Note that adhesive layers 32, 36, and 82 and coating 38 are not shown in Figure 3 because these layers do not significantly affect the polarization of light traveling through the system.

[0042] As shown in FIG. 3, light ray R1 may be emitted from display 14. Light ray R1 exits display 14 with a mixture of polarization states. When image light ray R1 exits display 14 and passes through linear polarizer 16, light ray R1 becomes linearly polarized, aligned with the pass axis of linear polarizer 16. The pass axis of linear polarizer 16 may be aligned with the X-axis in FIG. 3, for example. After passing through polarizer 16, light ray R2 passes through wave plate 18, which may be a quarter-wave plate. When light ray R2 passes through quarter-wave plate 18, light ray R3 exits the quarter-wave plate circularly polarized (e.g., with clockwise circular polarization).

[0043] When circularly polarized light ray R3 strikes partially reflecting mirror 22, a portion of ray R3 passes through partially reflecting mirror 22 as reduced-intensity ray R4. Ray R4 is refracted (partially focused) by the shape of convex surface S1 of lens element 26. Note that the depiction of surfaces S1 and S2 as flat surfaces in Figure 3 is for illustrative purposes only. In practice, surfaces S1 and S2 may be curved (e.g., aspherically convex and aspherically concave), as described in connection with Figure 2.

[0044] Wave plate 28 can convert the circular polarization of light ray R4 to linear polarization. Quarter wave plate 28 can, for example, convert circularly polarized light ray R4 to light ray R5 having a linear polarization aligned with the X-axis in Figure 2. Quarter wave plate 28 in optical system 20 can be rotated 90 degrees relative to quarter wave plate 18 in display 40 (e.g., the fast axes of quarter wave plates 18 and 28 are orthogonal).

[0045] As previously mentioned, the reflective polarizer 30 can have orthogonal reflection and pass axes. Light polarized parallel to the reflection axis of the reflective polarizer 30 is reflected by the reflective polarizer 30. Light polarized perpendicular to the reflection axis, and therefore parallel to the pass axis of the reflective polarizer 30, passes through the reflective polarizer 30. In the exemplary arrangement of Figure 3, the reflective polarizer 30 has its reflection axis aligned with the X-axis and its pass axis aligned with the Y-axis, so that ray R5 reflects from the reflective polarizer 30 as reflected ray R6. Note that the pass axis of the reflective polarizer 30 is orthogonal to the pass axis of the linear polarizer 16 in the display system 40.

[0046] The reflected ray R6 has linear polarization aligned with the X-axis. After passing through the quarter-wave plate 28, the linear polarization of ray R6 is converted to circular polarization (i.e., ray R6 becomes counterclockwise circularly polarized ray R7).

[0047] Circularly polarized light ray R7 passes through lens element 26, and a portion of ray R7 is reflected in the positive Z direction by partially reflective mirror 22 on convex surface S1 of lens element 26 as reflected ray R8. Reflection from the curved shape of surface S1 provides additional optical power to optical system 20. Note that any portion of ray R7 transmitted by partially reflective layer 22 (e.g., R7' in the negative Z direction) may be converted to linear polarization by quarter-wave plate 18 and then reaches linear polarizer 16. This linearly polarized light has polarization aligned with the Y axis (e.g., perpendicular to the pass axis of linear polarizer 16), causing it to be absorbed by linear polarizer 16. As a result, contrast degradation and stray light artifacts from this portion of ray R7 are prevented in the image viewed by the user.

[0048] Light ray R8 from partially reflecting mirror 22 is converted from circularly polarized light to linearly polarized light ray R9 by quarter-wave plate 28. It also passes through curved surface S2 of lens element 26, providing additional optical power (e.g., refractive optical power) to optical system 20. The linear polarization of light ray R9 is aligned with the Y-axis, which is parallel to the pass axis of reflective polarizer 30. Therefore, light ray R9 passes through reflective polarizer 30 as light ray R10 to provide a viewable image to the user.

[0049] Linear polarizer 34 has its pass axis aligned with the pass axis of reflective polarizer 30 (i.e., parallel to the Y-axis in this example), so that any light from the external environment is polarized by linear polarizer 34 and the light is not reflected by reflective polarizer 30. Light transmitted by linear polarizer 34 and reflective polarizer 30 passes through retarders 28 and 18 and is absorbed by linear polarizer 16. Linear polarizer 34 has its pass axis (parallel to the Y-axis) that is orthogonal to the pass axis (parallel to the X-axis) of linear polarizer 16 in the display.

[0050] After passing through linear polarizer 34, light finally passes through lens element 84. Lens element 84 provides additional optical power (e.g., refractive optical power) to optical system 20 at surface S3 and / or surface S4.

[0051] The partially reflective layer 22, lens element 26, quarter-wave plate 28, reflective polarizer 30, linear polarizer 34, and adhesive layers 32 and 36 may be formed as a solid assembly with no air gaps. As shown in Figure 2, each of layers 22, 26, 28, 30, 34, 32, and 36 is directly attached to the adjacent layer. This is particularly noteworthy when retarder 28 is attached directly to the aspherical concave surface S2 of lens element 26.

[0052] Conventionally, retarders are planar. However, herein, retarder 28 is a coating applied directly onto the curved surface of lens element 26 to provide uniform retardation across the lens element. Accordingly, retarder 28 of FIG. 2 can have an aspherical curvature (e.g., curvature along multiple axes and with different radii of curvature) with a relatively uniform thickness to provide a relatively uniform retardation. The retardation is equal to the retarder thickness multiplied by the birefringence of the retarder material. The thickness 62 (shown in FIG. 2) of retarder 28 may be relatively uniform across the optical system (lens assembly). Retarder 28 conforms to the three-dimensional surface of lens element 26 and is sometimes referred to as a coating (e.g., coating 28 or retarder coating 28).

[0053] As specific examples, the retardation provided by retarder 28 throughout the retarder may be uniform to within 20%, 10%, 5%, 3%, 2%, 1%, etc. Similarly, the thickness 62 of retarder 28 throughout the retarder may be uniform to within 20%, 10%, 5%, 3%, 2%, 1%, etc. In other words, the retardation variation across the retarder is within 20%, 10%, 5%, 3%, 2%, 1%, etc. The thickness variation across the retarder is within 20%, 10%, 5%, 3%, 2%, 1%, etc.

[0054] The retarder 28 can be formed from any desired material using any desired process. As one example, the retarder 28 can be formed from a liquid crystal material deposited on a photo-alignment layer. As another example, the retarder 28 can be formed from a liquid crystal material that is aligned using shear alignment. As yet another example, the retarder 28 can be formed from an inorganic material using oblique deposition. The retarder 28 material can be deposited using spin coating, spray coating, physical vapor deposition (PVD), or any other desired technique.

[0055] The examples of materials having uniform birefringence and relatively uniform birefringence used to form the retarder are merely illustrative. Any type of retarder that provides uniform retardation can be used. As an example, the retarder can have a first thickness and a first birefringence in a first portion. The retarder can have a second thickness and a second birefringence in a second portion. The second birefringence can be different from the first birefringence, and the second thickness can be different from the first thickness. However, the retardation can be the same in both portions. In other words, the retarder can be provided with different birefringences in different portions that are compensated for by different thicknesses in different portions to provide uniform retardation. These types of techniques can be used to provide uniform retardation even when uniform thickness is not practical from a manufacturing standpoint.

[0056] In the example of FIG. 2 , the reflective polarizer 30 and the linear polarizer 34 are formed by optical films laminated to the lens assembly using an optically clear adhesive. This type of configuration may be satisfactory for some lens elements 26. Specifically, if the radius of curvature of the lens elements 26 (and lens elements 84) is sufficiently large, the reflective polarizer 30 and the linear polarizer 34 may be formed using films. However, as the radius of curvature decreases (i.e., the lens curvature increases), the reflective polarizer 30 and the linear polarizer 34 may experience reliability issues (e.g., wrinkles, cracks, etc.) due to the high level of curvature required. Certain applications may require the optical system to include lens elements with a high degree of curvature. In these applications, it may be desirable to form the reflective polarizer 30 and / or the linear polarizer 34 as coatings (instead of as adhesively laminated films).

[0057] As a specific example, the linear polarizer 34 may be formed as a coating on the reflective polarizer 30 (allowing for the omission of an adhesive layer between the linear polarizer 34 and the reflective polarizer 30). A coatable linear polarizer may be formed from a layer of liquid crystal polymer or any other desired material that can be used to form a coating. The linear polarizer coating may include a dichroic dye in addition to the base material (e.g., liquid crystal polymer). Forming the linear polarizer as a coating allows for more aggressive curvature of the lens elements (and their conformal layers) in the optical system 20 without adversely affecting reliability. The thickness of the linear polarizer 34 (e.g., when formed as a coating) across the polarizer may be uniform to within 20%, 10%, 5%, 3%, 2%, 1%, etc. The thickness variation across the retarder linear polarizer may be within 20%, 10%, 5%, 3%, 2%, 1%, etc.

[0058] As another example, a single reflective polarizer and retarder layer can be used instead of separately formed reflective polarizer 30 and retarder 28 (as in FIG. 2). The reflective polarizer and retarder layer (sometimes called a circular reflective polarizer) can be coated directly onto surface S2 of lens element 26. The reflective polarizer and retarder layer may reflect light having a first circular polarization type and transmit light having a second, opposite circular polarization type. The reflective polarizer and retarder layer can be formed from cholesteric liquid crystals or any other desired material.

[0059] Note that if a reflective polarizer and a retarder layer are used, the linear polarizer 34 may optionally be omitted entirely. Alternatively, in embodiments with a reflective polarizer and a retarder layer 72, a circular polarizer can be used in place of the linear polarizer 34.

[0060] 2 using a single non-removable lens element 26 is merely illustrative. If desired, multiple non-removable lens elements may be used in optical system 20 in addition to removable lens element 84.

[0061] 2, the linear polarizer 34 is formed on surface S2 of the lens element 26. In other words, an air gap 102 is interposed between the lens element 84 and the linear polarizer 34. This example is merely illustrative. In another possible configuration, the linear polarizer 34 may be formed on surface S3 of the removable lens element 84. The linear polarizer 34 may be coated directly onto surface S3 of the removable lens element 84, or may be attached to surface S3 by a layer of adhesive. In this configuration, an air gap 102 is interposed between the linear polarizer 34 and the reflective polarizer 30 (and the lens element 26).

[0062] Yet another possibility is to place the linear polarizer 34 on the surface S4 of the removable lens element 84. The linear polarizer 34 may be coated directly on the surface S4 of the removable lens element 84 or may be attached to the surface S4 by a layer of adhesive. In this arrangement, the linear polarizer 34 is interposed between the surface S4 and the coating(s) 38.

[0063] Device 10 may include one or more mounting structures 104 used to selectively attach removable lens element 84 to the device. As shown in FIG. 4 , one or more mounting structures 104 may be included on surface S3 of lens element 84. The mounting structures may, for example, be distributed around the periphery of surface S3 (as shown in FIG. 4 ). The example having mounting structures on S3 is merely illustrative. One or more mounting structures 104 may also be included on surface S4 of lens element 84. The mounting structures may, for example, be distributed around the periphery of surface S4. Furthermore, one or more mounting structures 104 may be included on an edge surface of lens element 84 connecting surface S3 to S4. FIG. 5 is a cross-sectional side view of lens element 84 showing mounting structures 104 on an edge surface between surfaces S3 and S4. In general, any desired number of mounting structures in any desired locations may be included in device 10 to enable selective fixation of removable lens element 84 to device 10.

[0064] A wide variety of attachment structures can be used for attachment structure 104. The attachment structures may include protrusions, recesses, grooves, posts, magnets, hooks, loops, snaps, buttons, suction cups, drawstrings, zippers, adhesives (e.g., tape), flexible bands, or any other desired type of attachment structure. The attachment structures may be attached to corresponding attachment structures on lens element 26 and / or to support structures within device 10 (e.g., housing 12, a lens module housing formed separately from housing 12, etc.).

[0065] The mounting structure 104 on the lens element 84 may be a protrusion configured to mate with (interlock with) a corresponding recess. The corresponding recess may be included on the non-removable lens element 26 or on a support structure within the device 10 (e.g., housing 12, a lens module housing formed separately from housing 12, etc.). The protrusion on the lens element 84 may, as one example, bridge the air gap 102 between the lens elements 84 and 26 and protrude into the recess in the lens element 26. Layers 34, 36, 30, 32, and / or 28 may have corresponding openings to accommodate the protrusions.

[0066] The mounting structure 104 on the lens element 84 may be a recess configured to mate with (interlock with) a corresponding protrusion on the non-removable lens element 26 or on a support structure within the device 10 (e.g., housing 12, a lens module housing formed separately from housing 12, etc.). The protrusion on the lens element 26 may, as one example, bridge the air gap 102 between the lens elements 84 and 26 and protrude into a recess in the lens element 84. Layers 34, 36, 30, 32, and / or 28 may have corresponding openings to accommodate the protrusions.

[0067] In examples where mounting structure 104 includes a recess or protrusion, these features may be integrally molded with lens elements 84 and 26. In other words, the protrusion on lens element 84 may be formed from the same material as lens element 84 (e.g., formed in a single molding step with the lens element). The recess on lens element 84 may be defined by the material of lens element 84 (e.g., formed in a single molding step with the lens element). The protrusion on lens element 26 may be formed from the same material as lens element 26 (e.g., formed in a single molding step with the lens element). The recess on lens element 26 may be defined by the material of lens element 26 (e.g., formed in a single molding step with the lens element).

[0068] The mounting structure 104 may also be a magnet (e.g., a permanent magnet) configured to magnetically couple with a corresponding magnet included on the non-removable lens element 26 or on a support structure within the device 10 (e.g., housing 12, a lens module housing formed separately from the housing 12, etc.). As yet another example, the mounting structure on the lens element 84 may be a groove configured to mate with (interlock with) a corresponding post on the lens element 84 or on a support structure within the device (e.g., housing 12, a lens module housing formed separately from the housing 12, etc.).

[0069] The mounting structures 104 may be configured to properly align the removable lens element 84 with respect to the non-removable lens element 26 when the lens element 84 is attached to the device 10 to ensure satisfactory operation of the optical system. Different types of mounting structures 104 (e.g., protrusions, recesses, and magnets) may be used in a single device.

[0070] According to one embodiment, there is provided an electronic device configured to display an image, the electronic device including: a display panel configured to generate light for the image; and a lens module that receives light from the display panel, the lens module including: a first lens element; a second lens element, the second lens element being a removable lens element configured to be selectively attached to the lens module; a partially reflective mirror interposed between the first lens element and the display panel; a reflective polarizer interposed between the first lens element and the second lens element when the second lens element is attached to the lens module; and an air gap interposed between the first lens element and the second lens element when the second lens element is attached to the lens module.

[0071] According to another embodiment, the first lens element has a first convex surface and a first concave surface, the first convex surface being interposed between the first concave surface and the display panel.

[0072] According to another embodiment, the second lens element has a second convex surface and a second concave surface, and when the second lens element is attached to the lens module, the second convex surface is interposed between the first concave surface and the second concave surface.

[0073] According to another embodiment, the first concave surface has a minimum radius of curvature of a first magnitude and the second convex surface has a minimum radius of curvature of a second magnitude, the second magnitude being within 20% of the first magnitude.

[0074] According to another embodiment, the first concave surface has a minimum radius of curvature of a first magnitude and the second convex surface has a minimum radius of curvature of a second magnitude, the second magnitude being within 5% of the first magnitude.

[0075] According to another embodiment, the lens module includes a quarter wave plate interposed between the first lens element and the reflective polarizer.

[0076] According to another embodiment, the lens module includes a linear polarizer, and the reflective polarizer is interposed between the linear polarizer and the quarter wave plate.

[0077] According to another embodiment, the lens module includes a layer of adhesive that attaches the linear polarizer to the reflective polarizer.

[0078] According to another embodiment, the lens module includes an additional layer of adhesive that attaches the reflective polarizer to the quarter wave plate.

[0079] According to another embodiment, a linear polarizer is formed on the second convex surface of the second lens element.

[0080] According to another embodiment, a linear polarizer is formed on the second concave surface of the second lens element.

[0081] According to another embodiment, the air gap has a thickness that varies by less than 50%.

[0082] According to another embodiment, the lens module includes an anti-reflective coating on the second lens element, the second lens element being interposed between the anti-reflective coating and the first lens element when the second lens element is attached to the lens module.

[0083] According to another embodiment, the second lens element includes a mounting structure configured to be attached to a corresponding mounting structure on the first lens element when the second lens element is attached to the lens module.

[0084] According to another embodiment, the second lens element includes a mounting structure configured to be mounted to a corresponding mounting structure on the support structure when the second lens element is mounted to the lens module.

[0085] According to another embodiment, the second lens element is configured to accommodate an eyeglass prescription.

[0086] According to one embodiment, there is provided an electronic device configured to display an image, the electronic device including: a display panel configured to generate light for the image; a lens module that receives light from the display panel, the lens module including: a first lens element having a first convex surface and a first concave surface; and a second lens element having a second convex surface and a second concave surface, the second lens element being a removable lens element configured to be selectively attached to the lens module, wherein when the second lens element is attached to the lens module, the second convex surface faces the first concave surface, the first concave surface has a minimum radius of curvature of a first magnitude and the second convex surface has a minimum radius of curvature of a second magnitude, the second magnitude being within 20% of the first magnitude; and a partially reflective mirror interposed between the first lens element and the display panel.

[0087] According to another embodiment, the lens module includes an air gap interposed between the first lens element and the second lens element when the second lens element is attached to the lens module.

[0088] According to another embodiment, the air gap has a thickness that varies by less than 20%.

[0089] According to another embodiment, the lens module includes a reflective polarizer interposed between a first lens element and a second lens element when the second lens element is attached to the lens module, a quarter-wave plate interposed between the first lens element and the reflective polarizer, and a linear polarizer, the reflective polarizer being interposed between the linear polarizer and the quarter-wave plate.

[0090] According to one embodiment, there is provided an electronic device configured to display an image, the electronic device including: a display panel configured to generate light for the image; a lens module that receives light from the display panel, the lens module including: a first lens element having opposite first and second surfaces, the first surface facing the display panel; a second lens element having opposite third and fourth surfaces, the second lens element being a removable lens element configured to be selectively attached to the lens module; an air gap interposed between the first lens element and the second lens element when the second lens element is attached to the lens module, the air gap having a curvature that faces the second surface and that matches the curvature of the second surface when the second lens element is attached to the lens module; and a partially reflective mirror interposed between the first lens element and the display panel.

[0091] The above is merely exemplary and various modifications may be made to the described embodiments. The above embodiments may be implemented individually or in any combination.

Claims

1. 1. An electronic device configured to display an image, comprising: a display panel configured to generate light for the image; a lens module that receives light from the display panel, the lens module comprising: a first lens element; and a second lens element, the second lens element being a removable lens element configured to be selectively attached to the lens module; and a partially reflective mirror interposed between the first lens element and the display panel; a reflective polarizer interposed between the first lens element and the second lens element when the second lens element is attached to the lens module; and an air gap between the first lens element and the second lens element when the second lens element is attached to the lens module; An electronic device with a lens module, comprising:

2. 10. The electronic device of claim 1, wherein the first lens element has a first convex surface and a first concave surface, the first convex surface being interposed between the first concave surface and the display panel.

3. 3. The electronic device of claim 2, wherein the second lens element has a second convex surface and a second concave surface, and the second convex surface is interposed between the first concave surface and the second concave surface when the second lens element is attached to the lens module.

4. 4. The electronic device of claim 3, wherein the first concave surface has a minimum radius of curvature of a first magnitude and the second convex surface has a minimum radius of curvature of a second magnitude, the second magnitude being within 20% of the first magnitude.

5. 4. The electronic device of claim 3, wherein the first concave surface has a minimum radius of curvature of a first magnitude and the second convex surface has a minimum radius of curvature of a second magnitude, the second magnitude being within 5% of the first magnitude.

6. The lens module is a quarter wave plate interposed between the first lens element and the reflective polarizer; The electronic device of claim 3 further comprising:

7. The lens module is a linear polarizer, wherein the reflective polarizer is interposed between the linear polarizer and the quarter-wave plate; The electronic device of claim 6 further comprising:

8. The lens module is a layer of adhesive that attaches the linear polarizer to the reflective polarizer The electronic device of claim 7 further comprising:

9. The lens module is an additional layer of adhesive that attaches the reflective polarizer to the quarter wave plate; The electronic device of claim 8 further comprising:

10. The electronic device of claim 7 , wherein the linear polarizer is formed on the second convex surface of the second lens element.

11. The electronic device of claim 7 , wherein the linear polarizer is formed on the second concave surface of the second lens element.

12. The electronic device described in claim 1, wherein the air gap is interposed between a first surface of the first lens element and a second surface of the second lens element, and the width of the air gap between the first surface and the second surface varies within a range of less than 50%.

13. 10. The electronic device of claim 1, wherein the lens module further comprises an anti-reflective coating on the second lens element, the second lens element being interposed between the anti-reflective coating and the first lens element when the second lens element is attached to the lens module.

14. 10. The electronic device of claim 1, further comprising a mounting structure configured to mount the second lens element to a corresponding mounting structure on the first lens element when the second lens element is mounted to the lens module.

15. 10. The electronic device of claim 1, further comprising a mounting structure configured to mount the second lens element to a corresponding mounting structure on a support structure when the second lens element is attached to the lens module.

16. The electronic device of claim 1 , wherein the second lens element is configured to accommodate an eyeglass prescription.

17. 1. An electronic device configured to display an image, comprising: a display panel configured to generate light for the image; a lens module that receives light from the display panel, the lens module comprising: a first lens element having a first convex surface and a first concave surface; a second lens element having a second convex surface and a second concave surface, the second lens element being a removable lens element configured to be selectively attached to the lens module, wherein when the second lens element is attached to the lens module, the second convex surface faces the first concave surface, the first concave surface has a minimum radius of curvature of a first magnitude, and the second convex surface has a minimum radius of curvature of a second magnitude, the second magnitude being within 20% of the first magnitude; and a partially reflective mirror interposed between the first lens element and the display panel; and an electronic device comprising: a lens module comprising:

18. The lens module is an air gap between the first lens element and the second lens element when the second lens element is attached to the lens module; 20. The electronic device of claim 17, further comprising:

19. the air gap has a substantially constant width across the first lens element and the second lens element; The lens module is a reflective polarizer interposed between the first lens element and the second lens element when the second lens element is attached to the lens module; and a quarter wave plate interposed between the first lens element and the reflective polarizer; a linear polarizer, wherein the reflective polarizer is interposed between the linear polarizer and the quarter wave plate; 20. The electronic device of claim 18, further comprising:

20. 1. An electronic device configured to display an image, comprising: a display panel configured to generate light for the image; a lens module that receives light from the display panel, the lens module comprising: a first lens element having opposite first and second surfaces, the first surface facing the display panel; a second lens element having opposing third and fourth surfaces, the second lens element being a removable lens element configured to be selectively attached to the lens module; and an air gap between the first lens element and the second lens element when the second lens element is attached to the lens module, the third surface facing the second surface when the second lens element is attached to the lens module, the third surface having a curvature matching the curvature of the second surface; a partially reflective mirror interposed between the first lens element and the display panel; An electronic device comprising a lens module comprising:

Images