CN117850036A - Tunable lens with translatable reflector - Google Patents

Abstract

The invention relates to a tunable lens with a translatable reflector. A tunable lens comprising a pair of reflectors is disclosed. At least one of the reflectors may be curved to facilitate focusing or defocusing capabilities of the lens. At least one of the reflectors is translatable for tuning the focusing/defocusing capability. The reflectors may be configured in a wafer lens configuration, with one reflector being a 50/50 reflector and the other being a polarization selective reflector. Refractive elements may be provided between the reflectors for providing more optical power to the lens and/or for balancing optical aberrations.

Description

Tunable lens with translatable reflector

Cross Reference to Related Applications

The present application claims priority from: U.S. provisional patent application No. 63/414,260, entitled "Tunable Lens with Translatable Reflector (tunable lens with translatable reflector)", filed on 7, 10, 2022; and U.S. non-provisional patent application No. 18/079,427, entitled "Tunable Lens with Translatable Reflector (tunable lens with translatable reflector), filed 12/2022, the entire contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates to optical devices, and more particularly to tunable optical elements, and visual display devices using such tunable optical elements.

Background

Visual displays are used to provide information to one or more viewers, including still images, video, data, and the like. Visual displays have applications in different fields including entertainment, education, engineering, science, professional training, advertising, to name a few. Some visual displays (e.g., television sets (TV sets)) display images to digital users, while some visual display systems are intended for individual users. The visual display may be viewed directly or by means of special glasses, which may include optical shutters, as well as special zoom lenses.

An artificial reality system typically includes a near-eye display (NED) (e.g., a head set) or a pair of glasses) configured to present content to a user. The near-eye display may display the virtual object or combine an image of the real object with the virtual object as in a Virtual Reality (VR) application, an augmented reality (augmented reality, AR) application, or a Mixed Reality (MR) application. For example, in an AR system, a user may view an image (e.g., a computer-generated image (CGI)) of a virtual object superimposed on the surrounding environment. In some near-eye displays, each eye of the user sees an image displayed on a miniature display panel. The image can be observed through a visual lens (ocular lens).

Head-mounted displays (HMDs) require compact and efficient display systems. Because the display of an HMD or NED is typically worn on the head of a user, large, bulky and heavy, unbalanced, and/or heavy display devices will be heavy and potentially uncomfortable for the user to wear. Compact display devices require compact and efficient light sources, shutters, display panels, visual lenses, and the like. Visual lenses with short focal lengths and large numerical apertures used in NED applications may benefit from focal length tunability.

Disclosure of Invention

In one embodiment, a lens is provided that includes opposing first and second reflectors; wherein the first reflector is configured to at least partially transmit a light beam therethrough for impingement onto the second reflector, and wherein the second reflector is configured to at least partially reflect the light beam propagating through the first reflector back to the first reflector; wherein the first reflector is further configured to at least partially reflect the light beam reflected by the second reflector back to the second reflector, and wherein the second reflector is further configured to at least partially transmit the light beam reflected by the first reflector; and wherein at least one of the first reflector or the second reflector is translatable by application of a control signal for tuning at least one of a focal length of the lens or a position of a focal point of the lens.

In another embodiment, a near-eye display (NED) is provided, the NED comprising: a display panel for providing image light carrying an image; and a tunable visual lens for viewing the image therethrough, the tunable visual lens comprising: an opposing first reflector and a second reflector, wherein the first reflector is configured to at least partially transmit the image light therethrough to impinge on the second reflector, and wherein the second reflector is configured to at least partially reflect the image light back to the first reflector; wherein the first reflector is further configured to at least partially reflect the image light back to the second reflector, and wherein the second reflector is further configured to at least partially transmit the image light therethrough for viewing the image; and wherein at least one of the first reflector or the second reflector is translatable by application of a control signal for tuning the position of the image plane of the tunable visual lens.

In yet another embodiment, a wafer lens is provided, the wafer lens comprising: a partial reflector; a linear reflective polarizer; and a quarter wave plate located in the optical path between the partially reflector and the linear reflective polarizer; wherein at least one of the partially reflector or the linear reflective polarizer is curved; and wherein at least one of the partial reflector or the linear reflective polarizer is translatable or deformable by applying a control signal to at least one of a focal length of the wafer lens or a position of a focal point of the wafer lens.

Drawings

Exemplary embodiments will now be described in conjunction with the accompanying drawings, in which:

FIG. 1A is a side cross-sectional view of a tunable lens of the present disclosure having at least one translatable reflector;

FIG. 1B is a polarization diagram of the tunable lens of FIG. 1A, showing an exploded side view of the elements of the tunable lens of FIG. 1A;

FIG. 1C is a ray-tracing view of one embodiment of the tunable lens of FIG. 1A with a translatable partial reflector (translatable partial reflector);

FIG. 1D is a ray-tracing diagram of one embodiment of a tunable lens of FIG. 1A having a translatable reflective polarizer (translatable reflective polarizer);

FIG. 2 is a graph of translational distance versus power change for tunable lens 100D of FIG. 1D;

FIG. 3A is a schematic side view of a translatable reflector of the tunable lens of FIGS. 1A-1D positioned on a motor-actuated translation stage;

FIG. 3B is a schematic side view of the translatable reflector of the tunable lens of FIGS. 1A-1D with a miniature voice coil/electromagnetic actuator;

FIG. 3C is a schematic side view of a mounted reflector of the tunable lens of FIGS. 1A-1D movable by a shape memory alloy actuator;

FIG. 3D is a schematic side view of the mounted reflector of the tunable lens of FIGS. 1A-1D movable by a piezoelectric actuator;

FIG. 4 is a schematic diagram of a near-eye display including the tunable lens of FIG. 1A, FIG. 1C, and/or FIG. 1D as a viewing lens for the near-eye display;

FIG. 5 is a top view of a near-eye display having the form factor of a pair of eyeglasses; and

fig. 6 is a three-dimensional view of a head mounted display of the present disclosure.

Detailed Description

While the present teachings are described in connection with various embodiments and examples, the present teachings are not intended to be limited to these embodiments. On the contrary, the present teachings encompass various alternatives and equivalents, as will be appreciated by those of skill in the art. All statements herein reciting principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Furthermore, such equivalents are intended to include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

As used herein, unless explicitly stated otherwise, the terms "first" and "second," etc. are not intended to imply a sequential ordering, but rather to distinguish one element from another. Similarly, the sequential ordering of method steps does not imply an order in which they are performed unless explicitly stated.

Presenting a simulated scene or an enhanced scene to a user of a near-eye display may result in visual fatigue and nausea due to the limited ability of existing head-mounted devices to properly compensate for the disparity between eye convergence and eye focus to accommodate visual distances, a problem known as vergence accommodation conflict (vergent-accommodation conflict). Vergence adjustment conflicts occur because vergence of a user's eyes changes as the virtual object that the user is looking at changes, while accommodation of the eyes (i.e., focus) is typically fixed and set by the distance between the electronic display that produces the virtual image and the lens system that projects the image into the user's eyes.

In near-eye display systems based on miniature display panels viewed through a visual lens, one solution to the problem of convergence adjustment conflicts is to move the display panel back and forth according to the convergence angle of the object displayed by the display panel. The physical movement of the display panel may cause speed problems and reliability problems. Another solution is to make the ocular lens as a zoom as the ocular lens itself, i.e., dynamically tune or change the optical power (i.e., focusing power or defocusing power) of the ocular lens to accommodate dynamic changes in ocular vergence.

The solution described herein provides an efficient and compact zoom lens capable of rapidly changing its optical power. The zoom lens of the present disclosure may be based on a so-called wafer lens (wafer lens) comprising a reflective optical element in the optical path through polarization folding. The wafer lens may comprise two reflectors, for example a polarization selective reflector and a partial reflector. By making at least one of these reflectors translatable (e.g., through the use of a plurality of micro-actuators), the position of the reflector along the optical axis can be dynamically changed as desired. In addition to adjustment, the translatable reflector may also be used to control spherical correction and provide Rx correction, rather than relying on prescription glasses.

According to the present disclosure, a lens is provided that includes opposing first and second reflectors. The first reflector is configured to at least partially transmit the light beam therethrough to impinge upon the second reflector. The second reflector is configured to at least partially reflect the light beam propagating through the first reflector back to the first reflector. The first reflector is further configured to at least partially reflect the light beam reflected by the second reflector back to the second reflector. The second reflector is further configured to at least partially transmit the light beam reflected by the first reflector. At least one of the first reflector or the second reflector is translatable by application of a control signal for tuning at least one of a focal length of the lens or a position of a focal point of the lens. For example, at least one of the first reflector or the second reflector may be coupled with an actuator controllable by application of an external electrical signal for tuning at least one of a focal length of the lens or a position of a focal point of the lens.

In some embodiments, the first reflector comprises a partial mirror (e.g., a 50/50 mirror) that reflects as much light as it transmits. The second reflector may comprise a reflective polarizer. The lens may further comprise a Quarter Wave Plate (QWP) located between the first and second reflectors for converting the polarization state of the light beam from a first polarization state to a second orthogonal polarization state when the light beam propagates in two passes through the quarter wave plate (double pass propagation). The reflective polarizer may be, for example, a linear reflective polarizer. The actuator may comprise at least one of: stepper motors, voice coil actuators, shape memory alloys, direct Current (DC) motors, piezoelectric actuators, or electromagnetic actuators. At least one of the first reflector or the second reflector may be mounted on a translation stage movable by an actuator. At least one of the first reflector or the second reflector may be deformed by application of a control signal for tuning at least one of a focal length of the lens or a position of a focal point of the lens. The lens may further comprise one or more refractive lens elements located between the first reflector and the second reflector.

According to the present invention there is also provided a wafer lens comprising a partial reflector, a linear reflective polarizer and a quarter wave plate in the optical path between the partial reflector and the linear reflective polarizer. At least one of the partial reflector or the linear reflective polarizer is curved and is translatable or deformable by applying a control signal to at least one of a focal length of the lens or a position of a focal point of the lens. At least one of the partial reflector or the linear reflective polarizer may be coupled to one or more actuators controllable by application of an external electrical signal for tuning at least one of a focal length of the wafer lens or a position of a focal point of the wafer lens. The one or more actuators may include, for example, stepper motors, voice coil actuators, shape memory alloys, DC motors, piezoelectric actuators, and/or electromagnetic actuators. At least one of the partially reflector or the linear reflective polarizer may be mounted on a translation stage movable by an actuator.

In accordance with the present disclosure, a near-eye display (NED) is provided that includes a display panel for providing image light carrying an image, and a lens of the present disclosure for viewing the image through the lens.

Referring now to fig. 1A, a lens 100A of the present disclosure includes opposing first and second reflectors 111 and 112, with optional first and second refractive lens elements 101 and 102 disposed in series between the first and second reflectors 111 and 112. The first and second reflectors 111 and 112 may be deposited on/supported by the first and second refractive lens elements 101 and 102, or may be provided on separate substrates. The lens 100A may be used as a tunable visual lens for viewing images in the linear domain displayed by the micro display panel 106 at short distances by converting the images in the linear domain into images in the angular domain at the eye pupil 110. Here and in the rest of the specification, the term "image in the linear domain" refers to the following image: the individual pixels of the image are represented by pixel linear coordinates (i.e., the row and column numbers of the display panel), and the term "image in the angular domain" refers to the following image: individual pixels of the image are represented by the angle of the collimated beam at the pupil 110 of the eye. In other words, the term "image in the linear domain" refers to the following image: the individual pixels of the image are represented by ray coordinates, and the term "image in the angular domain" refers to the following image: the individual pixels of the image are represented by ray angles. It should also be noted that the image in the angular domain can be directly viewed by the eye because the cornea and lens of the eye convert the ray angle into ray coordinates on the retina of the eye.

In operation, the display panel 106 emits image light carrying the displayed image. The image light is represented in fig. 1A by beam 104. The first reflector 111 of the lens 100A is configured to at least partially transmit the light beam 104 through the first reflector 111 to impinge on the second reflector 112. The second reflector 112 is configured to at least partially reflect the light beam 104 propagating through the first reflector 111 back to the first reflector 111. The first reflector 111 is further configured to at least partially reflect the light beam 104 reflected by the second reflector 112 back to the second reflector 112. The second reflector 112 is further configured to at least partially transmit the light beam 104 reflected by the first reflector 111 to the pupil 110 of the eye.

Lens 100A has optical power due to the presence of an element having optical power. For example, as shown in fig. 1A, the first reflector 111 may be curved. The optional first refractive lens element 101 and second refractive lens element 102 located in the optical path between the first reflector 111 and the second reflector 112 may also provide optical power and/or balance optical aberrations to the lens 100A. The curvatures of the individual optical elements may be selected so as to counteract or reduce the overall optical aberration of the lens 100A. At least one or both of the first reflector 111 or the second reflector 112 may be translated and/or deformed by application of one or more control signals in the form of electrical signals, mechanical pressure, force, or the like, for tuning the lens 100A (i.e., changing the position of the focal point of the lens 100A, the focal length of the lens 100A, and/or the position of the image plane provided by the lens 100A relative to the eye pupil 110). The focal position of lens 100A is tuned in a controllable and predictable manner.

In some embodiments, deformable reflectors 111 and/or 112 may change their radius of curvature, thereby changing their optical power and tuning the overall optical power of lens 100A. The tunable optical power allows one to tune the axial position of the image plane of the image projected by lens 100A. Reflectors 111 and/or 112 may be deformable by applying radial pressure to reflectors 111 and/or 112. In some embodiments, both the position along the optical axis and the radius of curvature of reflectors 111 and/or 112 may vary. Furthermore, depending on the specifics of the configuration, a controllable compensation of the eye aberrations (i.e. the prescription of the eye) may be achieved.

A specific exemplary configuration of the first reflector 111 and the second reflector 112 will now be considered. It should be understood that the examples considered below are non-exclusive and that many other configurations are possible. The first reflector 111 may be a partial mirror (e.g., 50/50 mirror) that reflects the same amount of light as it transmits; that is, the light energy per unit time of the transmitted light and the reflected light is the same. The second reflector 112 may be a reflective polarizer (e.g., a linear reflective polarizer) configured to reflect linearly polarized light of a predetermined linear polarization orientation. Lens 100A may further include a Quarter Wave Plate (QWP) 108 disposed between first reflector 111 and second reflector 112 for converting the polarization state of light beam 104 from a first polarization state to a second orthogonal polarization state upon double pass propagation of the light beam 104 through QWP 108, the double pass propagation being provided by reflection of light beam 104 from first reflector 111.

In fig. 1A, the QWP 108 is shown as being laminated on the first refractive lens element 101, as a non-limiting example. Other locations of the QWP 108 in the optical path between the first and second reflectors 111, 112 are also possible, e.g. the QWP 108 may be laminated on the second refractive lens element 102 or supported by the second refractive lens element 102. The QWP 108 may also be laminated on the first reflector 111 or the second reflector 112, or supported by the first reflector 111 or the second reflector 112, as long as the QWP 108 is disposed between the reflective surface of the first reflector 111 and the reflective surface of the second reflector 112.

Fig. 1B provides an illustration of the optical path of folded beam 104 using a combination of reflective polarizers, polarization rotators (e.g., QWP used in a double pass with intermediate reflection), and partial reflectors. The display panel 106 may include a linear transmissive polarizer 120 coupled to a display side QWP 122 to circularly polarize the light beam 104. In this exemplary configuration, the light beam 104 emitted by the display panel 106 is left-hand circularly polarized (LCP) as it propagates through the display side QWP 122.

The LCP beam 104 propagates through the first reflector 111 (i.e., the 50/50 reflector in this embodiment) and impinges on the QWP 108, which QWP 108 converts the polarization state into a 45 degree linear polarization state. The second reflector 112 (i.e., the linear reflective polarizer in this embodiment) is configured to reflect the 45 degree linearly polarized light, so that the light beam 104 is reflected back from the second reflector 112 through the QWP 108, thereby converting the polarization state back to LCP. When reflected from the first reflector 111, the LCP beam 104 becomes right-handed circularly polarized (right circular polarized, RCP) due to the change in the direction of propagation of the beam 104. RCP beam 104 propagates through QWP 108, becomes 135 degrees linearly polarized, and is transmitted through the reflective polarizer to eye pupil 110. It should be noted that the polarization states and angles of linear polarization are merely examples, and that other configurations for folding the beam path by polarization are possible.

Lens 100A is one embodiment of a wafer lens that may be used as a visual lens for a near-eye display. The polarized beam folding of the optical path of the wafer lens makes the NED very compact, which may be desirable in NED applications. Such a wafer lens comprises a partial reflector (first reflector 111), a linear reflective polarizer (second reflector 112), and a quarter wave plate (QWP 108) in the optical path between the partial reflector and the linear reflective polarizer. At least one of the partially reflector or the linear reflective polarizer may be curved to provide optical power to the wafer lens. At least one of the partial reflector or the linear reflective polarizer may be translated by application of a control signal for tuning the axial position and/or focal length and/or image plane of the focal point of the wafer lens. In a near-eye display application of lens 100A, changing the image plane position relative to the eye pupil 110 position allows one to accommodate eye refocusing due to dynamic changing eye convergence, with the purpose of mitigating convergence accommodation conflicts.

It should be noted that the movement of the focal point/image plane of the wafer lens can be achieved essentially without tuning the optical power of the lens. For example, if the element having optical power is not a reflector such as a refractive lens, actuating either reflector (e.g., a planar reflector) may still move the position of the image plane provided by lens 100A without changing the effective focal length of lens 100A. Similarly, if only a single element having optical power, e.g., only one reflector is curved and no additional refractive element is present, actuation of that reflector may change the focal/image plane position of the lens without changing the effective focal length of the lens.

Bending reflectors 111 and/or 112 may provide a minimal form factor, but if another refractive element is present in lens 100A, such as first refractive lens element 101 and/or second refractive lens element 102, no bending is required. The optical power of the lens 100A changes when (1) the distance between the elements having optical power changes, or (2) the surface is deformed by the change in curvature. If the focal point of the lens is moved relative to the display panel being imaged, focusing or defocusing can occur without a change in optical power to move the eye to adjust the focal point. The position of the focal point is defined by the lens parameters and the optical path length in consideration of the folding path of the lens 100A.

Fig. 1C shows one embodiment of the tunable lens 100A of fig. 1A (tunable lens 100C) having a curved translatable first reflector 111 (i.e., a partial reflector in this example). Coordinates of the pixels 106A to 106E of the display panel 106 are converted into angles of incidence of the image beams 104A to 104E emitted by the respective pixels 106A to 106E onto the eye pupil 110 of the viewer, thereby converting an image in the linear domain displayed by the display panel 106 into an image in the angular domain at the eye pupil 110 of the viewer, wherein the conversion coefficient is defined by the optical power of the tunable lens 100C. By translating the first reflector 111 along the optical axis of the lens 100, as indicated by arrow 180, the position of the image plane relative to the eye pupil 110 can be changed to facilitate convergence driven accommodation of the eye. The position may change due to a change in the optical power or focal length of the lens 100C. As described above, the position of the image plane can also be changed without changing the optical power. In either case, adjusting the position of the image plane relative to the eye pupil 110 provides real-time eye accommodation changes to the viewer of the display panel 106. In the embodiment shown in FIG. 1C, the first reflector 111 is a partial (e.g., 50/50) reflector.

Turning to fig. 1D and with further reference to fig. 1A, tunable lens 100D (fig. 1D) is one embodiment of tunable lens 100A (fig. 1A). In the tunable lens 100D of fig. 1D, the second reflector 112 (e.g., a curved reflective polarizer) is translatable. In some embodiments, the reflective polarizer may be flat. At least one of the first reflector 111 or the second reflector 112 may be translatable for tuning the optical power of the tunable lens by applying an external signal. The first reflector 111 and/or the second reflector 112 may be adhered to/supported by an additional substrate, and the additional substrate may be moved to move the first reflector 111 and/or the second reflector 112.

Referring to fig. 2, the relationship between reflector translation and the desired power change (in diopters) of tunable lens 100C of fig. 1C is plotted. It can be seen that only about 3mm of translation is required to achieve a 10 diopter change in optical power. Because the reflectors are disposed on thin, lightweight films, translation of one or both reflectors can be performed in a fast and energy efficient manner by the translation stage 190 of fig. 1C and 1D. By way of non-limiting example, translation stage 190 may include an actuator, such as a stepper motor, voice coil actuator, shape memory alloy, DC motor, piezoelectric actuator, and/or electromagnetic actuator. The actuator may be controlled by applying an external electrical signal such as a voltage, current, etc. Examples of translational configurations of reflectors of tunable lenses 100A, 100C, or 100D are shown in fig. 3A-3D.

Referring first to fig. 3A, translatable reflector assembly 300A may be used to translate reflectors 111 and/or 112 of tunable lens 100A of fig. 1A, reflectors 111 and/or 112 of tunable lens 100C of fig. 1C, and reflectors 111 and/or 112 of tunable lens 100D of fig. 1D. Translatable reflector assembly 300A of fig. 3A includes reflector 311 supported by translation stage 304, which corresponds to translation stage 190 of tunable lenses 100C and 100D. Translation stage 304 is actuated by micro-motor 302A to translate reflector 311 along optical axis 306 of the tunable lens, as indicated by arrow 380. The micro-motor 302A may include, for example, a stepper motor or a DC motor (e.g., a DC brushless servo motor). The motor 302A may be activated by applying an electrical signal to rotate the motor 302A controlled angle.

Referring to fig. 3B, translatable reflector assembly 300B may be used to translate reflectors 111 and/or 112 of tunable lens 100A of fig. 1A, reflectors 111 and/or 112 of tunable lens 100C of fig. 1C, and reflectors 111 and/or 112 of tunable lens 100D of fig. 1D. Translatable reflector assembly 300B of fig. 3B includes reflector 311 supported by translation stage 304, which corresponds to translation stage 190 of tunable lenses 100C and 100D. Translation stage 304 is actuated by electromagnetic actuator 302B to translate reflector 311 along optical axis 306 of the tunable lens, as indicated by arrow 380. Electromagnetic actuator 302B may include, for example, a voice coil and/or an electromagnetic coil coupled to a permanent magnet. Electromagnetic actuator 302B may be actuated by application of an external signal (e.g., an electrical current) to translate reflector 311 by a controlled amount.

Referring now to fig. 3C, translatable reflector assembly 300C may be used to translate reflectors 111 and/or 112 of tunable lens 100A of fig. 1A, reflectors 111 and/or 112 of tunable lens 100C of fig. 1C, and reflectors 111 and/or 112 of tunable lens 100D of fig. 1D. The translatable reflector assembly 300C of fig. 3C is one example of a translatable reflector that does not require a translation stage. The translatable reflector assembly 300C includes a reflector 311 supported by a plurality of memory alloy actuators 302C. The memory alloy actuator 302C may include a memory alloy wire that changes its shape as a function of temperature. The temperature may be adjusted by a plurality of heaters 308, the plurality of heaters 308 being disposed in thermal contact with the memory alloy actuator 302C. Applying an electrical current to the heater 308 causes the memory alloy actuator 302C to translate the reflector 311 by a controlled amount.

Turning to fig. 3D, translatable reflector assembly 300D may be used to translate reflectors 111 and/or 112 of tunable lens 100A of fig. 1A, reflectors 111 and/or 112 of tunable lens 100C of fig. 1C, and reflectors 111 and/or 112 of tunable lens 100D of fig. 1D. The translatable reflector assembly 300D of fig. 3D is another example of a translatable reflector that does not require a translation stage. Translatable reflector assembly 300D includes reflector 311 supported by a plurality of piezoelectric actuators 302D. The piezoelectric actuator 302D may include a stack of piezoelectric elements. The length of the stack of piezoelectric elements may be varied by applying a voltage to the stack, causing the piezoelectric actuator 302D to translate the reflector 311 by a controlled amount.

Referring to fig. 4, a near-eye display (NED) 400 may include any of the tunable lenses disclosed herein. NED 400 includes a display panel 106 coupled with a tunable lens 100 (e.g., lens 100A of fig. 1A, lens 100C of fig. 1C, and lens 100D of fig. 1D, or any variation of such lenses contemplated herein). The display panel 106 is configured to provide images in the linear domain. Three such display panel pixels are shown in fig. 4: a first pixel 401, a second pixel 402, and a third pixel 403. The second pixel 402 is an on-axis pixel, i.e. the second pixel 402 is arranged on the optical axis 413 of the lens 100, while the first pixel 401 and the third pixel 403 are off-axis pixels arranged offset from the optical axis 413.

The lens 100 is configured to convert an image in the linear domain into an image in the angular domain at the eyebox (eyebox) 412 of the NED 400 for direct viewing by the user's eye (not shown) at the eyebox 412. The term "image in the angular domain" refers to the following image: the individual pixels of the image are represented by the angle of the collimated beam at the eyebox 412. For example, the first pixel 401 emits a first cone of light emission 461, which first cone of light emission 461 is collimated by the lens 100 into a first collimated light beam 471, which first collimated light beam 471 has an oblique angle of incidence at the image plane 450 of the NED 400, which image plane 450 is typically arranged in the eyebox 412. The second pixel 402 emits a second diverging light cone 462, which second diverging light cone 462 is collimated by the lens 100 into a second collimated light beam 472, which second collimated light beam 472 has a zero (or normal) angle of incidence at the image plane 450. Finally, the third pixel 403 emits a third diverging cone 463 of light, which third diverging cone 463 of light is collimated by the lens 100 into a third collimated light beam 473, which third collimated light beam 473 has an oblique angle of incidence at the image plane 450 of opposite sign to the oblique angle of incidence of the first collimated light beam 471. In other words, the lens 100 operates as an offset-to-angle element that converts the offset of the divergent light beam upstream of the lens 100 into the angle of the collimated light beam downstream of the lens 100.

In NED 400, display panel 106 is imaged by lens 100 to image plane 450. The eye accommodation required for focusing the lens of the eye is a function of the distance from the eye to the image plane 450. The position of the image plane 450 is determined by the focal length of the lens 100 and the relative position of the focal point of the lens 100 with respect to the display panel 106. The position of the image plane 450 may be changed as follows: a focal length change; the focus moves relative to the display panel 106; or both. For example, if the entire lens 100 is moved relative to the display panel 106, the position of the image plane 450 may change with the movement of the focal point relative to the display panel 106 even if the focal length of the lens 100 is constant. This may be similar to axially translating a planar reflector within lens 100, such that the focal length of lens 100 may or may not be changed, depending on the particular configuration of lens 100.

Referring to fig. 5, a near-eye display 500 includes a frame 501 having the form factor of a pair of eyeglasses. For each eye, the frame 501 supports: an electronic display panel 508, a visual lens 510 optically coupled to the electronic display panel 508, an eye-tracking camera 504, and a plurality of illuminators 506. The vision lens 510 may include any of the tunable lenses disclosed herein. The illuminator 506 may be supported by a vision lens 510 for illuminating an eyebox 512. The electronic display panel 508 provides an image in the linear domain that is converted by the vision lens 510 into an image in the angular domain for viewing by the user's eyes.

The purpose of the eye-tracking camera 504 is to determine the position and/or orientation of the user's two eyes. Once the position and orientation of the user's eyes are known, the gaze convergence distance and direction may be determined. The imagery displayed by the display panel 508 may be dynamically adjusted to more realistically immerse the user in the displayed augmented reality scene, and/or to provide specific functionality for interaction with the augmented reality, in view of the user's gaze. The focal/image plane position of the visual lens 510 may be tuned by translating the reflector of the visual lens 510 to reduce convergence adjustment conflicts, thereby reducing fatigue and headache for the user of the near-eye display 500. In operation, the illuminator 506 illuminates the eye at the corresponding eyebox 512 to enable the eye tracking camera to obtain an image of the eye and provide a reference reflection (i.e., glint). Flicker may be used as a reference point in the captured eye image to facilitate the determination of the eye gaze direction by determining the position of the eye pupil image relative to the flicker image. To avoid that the illumination light is distracting to the user, the illumination light may be made invisible to the user. For example, infrared light may be used to illuminate the eyebox 512.

Turning to fig. 6, hmd 600 is an example of an AR/VR wearable display system that encloses a user's face in order to more immerse it in an AR/VR environment. The function of HMD 600 may be to generate a fully virtual 3D image. HMD 600 may include a front body 602 and a strap 604. The front body 602 is configured for placement in front of the user's eyes in a reliable and comfortable manner, and the strap 604 may be stretched to secure the front body 602 to the user's head. A display system 680 may be provided in the front body 602 for presenting AR/VR images to a user. The display system 680 may include any of the tunable lenses disclosed herein. The side 606 of the front body 602 may be opaque or transparent.

In some embodiments, the front body 602 includes a locator 608 and an inertial measurement unit (inertial measurement unit, IMU) 610 for tracking acceleration of the HMD 600, and a position sensor 612 for tracking a position of the HMD 600. IMU 610 is such an electronic device: the electronic device generates data indicative of a position of the HMD 600 based on measurement signals received from one or more position sensors 612 that generate one or more measurement signals in response to movement of the HMD 600. Examples of the position sensor 612 include: one or more accelerometers, one or more gyroscopes, one or more magnetometers, other suitable types of sensors that detect motion, a type of sensor for error correction of the IMU 610, or some combination thereof. The position sensor 612 may be located external to the IMU 610, internal to the IMU 610, or some combination thereof.

The locator 608 is tracked by an external imaging device of the virtual reality system so that the virtual reality system can track the position and orientation of the entire HMD 600. The information generated by the IMU 610 and the position sensor 612 may be compared to the position and orientation obtained by the tracking locator 608 to improve the tracking accuracy of the position and orientation of the HMD 600. As a user moves and rotates in 3D space, the exact position and orientation is important for presenting the user with the proper virtual scene.

The HMD 600 may also include a depth camera assembly (depth camera assembly, DCA) 611 that captures data describing depth information for some or all of the local areas surrounding the HMD 600. The depth information may be compared to information from the IMU 610 to more accurately determine the position and orientation of the HMD 600 in 3D space.

HMD 600 may also include an eye tracking system 614 for determining the orientation and position of a user's eyes in real-time. The obtained position and orientation of the eyes also allows the HMD 600 to determine the gaze direction of the user and adjust the image generated by the display system 680 accordingly. In one embodiment, convergence, i.e. the angle of convergence of the user's eye gaze, is determined. The determined gaze direction and convergence angle may be used to adjust the focal length of the lenses of the display system 680 to reduce convergence adjustment conflicts. The direction and convergence can also be used for real-time compensation of visual artifacts depending on the viewing angle and eye position. Further, the determined vergence angle and gaze angle may be used to interact with a user, highlight an object, bring an object to the foreground, create additional objects or pointers, and so forth. An audio system may also be provided that includes, for example, a set of small speakers built into the front body 602.

Embodiments of the present disclosure may include or be implemented in conjunction with an artificial reality system. The artificial reality system adjusts sensory information about the outside world (e.g., visual information, audio, touch (somatosensory) information, acceleration, balance, etc.) obtained through sensory in some way before presenting to the user. As non-limiting examples, the artificial reality may include Virtual Reality (VR), augmented reality (augmented reality, AR), mixed Reality (MR), mixed reality (hybrid reality), or some combination and/or derivative thereof. The artificial reality content may include entirely generated content, or generated content in combination with captured (e.g., real world) content. The artificial reality content may include video, audio, physical or tactile feedback, or some combination thereof. Any of these content may be presented in a single channel or multiple channels (e.g., in stereoscopic video that produces a three-dimensional effect to the viewer). Further, in some embodiments, the artificial reality may also be associated with an application, product, accessory, service, or some combination thereof, for creating content in the artificial reality and/or otherwise for the artificial reality (e.g., performing an activity in the artificial reality), for example. The artificial reality system providing artificial reality content may be implemented on a variety of platforms including a wearable display (e.g., an HMD connected to a host computer system), a standalone HMD, a near-eye display with a form factor of glasses, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers.

The scope of the present disclosure is not limited by the specific embodiments described herein. Indeed, various other embodiments and modifications in addition to those described herein will be apparent to those skilled in the art from the foregoing description and accompanying drawings. Accordingly, such other embodiments and modifications are intended to fall within the scope of this disclosure. Furthermore, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.

Claims (20)

1. A lens, the lens comprising:

opposing first and second reflectors;

wherein the first reflector is configured to at least partially transmit a light beam therethrough for impingement onto the second reflector, and wherein the second reflector is configured to at least partially reflect the light beam propagating through the first reflector back to the first reflector;

Wherein the first reflector is further configured to at least partially reflect the light beam reflected by the second reflector back to the second reflector, and wherein the second reflector is further configured to at least partially transmit the light beam reflected by the first reflector; and is also provided with

Wherein at least one of the first reflector or the second reflector is translatable by application of a control signal for tuning at least one of a focal length of the lens or a position of a focal point of the lens.

2. The lens of claim 1, wherein the first reflector comprises a partial mirror.

3. The lens of claim 2, wherein the partial mirror is a 50/50 mirror.

4. The lens of claim 2, wherein the second reflector comprises a reflective polarizer, the lens further comprising a quarter wave plate between the first and second reflectors for converting the polarization state of the light beam from a first polarization state to a second orthogonal polarization state as the light beam propagates through the quarter wave plate in two passes.

5. The lens of claim 4, wherein the reflective polarizer is a linear reflective polarizer.

6. The lens of claim 1, wherein the at least one of the first reflector or the second reflector is coupled with an actuator controllable by application of an external electrical signal for tuning the at least one of a focal length of the lens or a position of a focal point of the lens.

7. The lens of claim 6, wherein the actuator comprises at least one of: stepper motors, voice coil actuators, shape memory alloys, direct current DC motors, piezoelectric actuators, or electromagnetic actuators.

8. The lens of claim 6, wherein the at least one of the first reflector or the second reflector is mounted on a translation stage movable by the actuator.

9. The lens of claim 1, wherein at least one of the first reflector or the second reflector is deformable by application of a control signal for tuning the at least one of a focal length of the lens or a position of a focal point of the lens.

10. The lens of claim 1, further comprising a first refractive lens element located between the first reflector and the second reflector.

11. The lens of claim 10, further comprising a second refractive lens element located between the first reflector and the second reflector and coupled in series with the first refractive lens element.

12. A near-eye display NED, the NED comprising:

a display panel for providing image light carrying an image; and

a tunable visual lens for viewing the image therethrough, the tunable visual lens comprising:

an opposing first reflector and a second reflector, wherein the first reflector is configured to at least partially transmit the image light therethrough to impinge on the second reflector, and wherein the second reflector is configured to at least partially reflect the image light back to the first reflector;

wherein the first reflector is further configured to at least partially reflect the image light back to the second reflector, and wherein the second reflector is further configured to at least partially transmit the image light therethrough for viewing the image; and is also provided with

Wherein at least one of the first reflector or the second reflector is translatable by application of a control signal for tuning the position of the image plane of the tunable visual lens.

13. The NED of claim 12, wherein the at least one of the first or second reflectors is coupled with an actuator controllable by application of an external electrical signal for tuning the position of the image plane.

14. The NED of claim 13, wherein the actuator comprises at least one of: stepper motors, voice coil actuators, shape memory alloys, direct current DC motors, piezoelectric actuators, or electromagnetic actuators.

15. The NED of claim 14, wherein the at least one of the first or second reflectors is mounted on a translation stage movable by the actuator.

16. The NED of claim 12 further comprising a refractive lens element between the first and second reflectors.

17. A wafer lens, the wafer lens comprising:

a partial reflector;

a linear reflective polarizer; and

a quarter wave plate located in the optical path between the partially reflector and the linear reflective polarizer;

wherein at least one of the partially reflector or the linear reflective polarizer is curved; and is also provided with

Wherein at least one of the partial reflector or the linear reflective polarizer is at least one of translatable or deformable by applying a control signal to at least one of a focal length of the wafer lens or a position of a focal point of the wafer lens.

18. A wafer lens according to claim 17, wherein the at least one of the partially reflector or the linear reflective polarizer is coupled with an actuator controllable by application of an external electrical signal for tuning at least one of a focal length of the wafer lens or a position of a focal point of the wafer lens.

19. Wafer lens according to claim 18, wherein the actuator comprises at least one of: stepper motors, voice coil actuators, shape memory alloys, direct current DC motors, piezoelectric actuators, or electromagnetic actuators.

20. Wafer lens according to claim 19, wherein the at least one of the partial reflector or the linear reflective polarizer is mounted on a translation stage movable by the actuator.