Near-eye display with array optics

Abstract

Transparent organic light-emitting diodes (OLEDs) can be used as light-emitting pixels in near-eye displays for augmented reality applications. Light from these pixels can be switchably adjusted and / or steered by adjustable beam steering and focusing elements (also called adjustable microlenses). These adjustable microlenses are arranged in an array and coupled to the array of pixels, for example, by being embedded in eyeglass lenses. The adjustable microlenses use fast-switching half-wave plates to selectively focus and / or tilt the light from the pixels. By switching the light from the pixels between resolvable positions / angles at a rate faster than the flicker fusion threshold (e.g., 60 Hz), the adjustable microlenses can effectively double the apparent resolution of the near-eye display. Also, by switching between focused and unfocused states at the same rate, the adjustable microlenses can effectively superimpose a virtual image from the pixel onto the real-world image seen through the pixel.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority under 35 U.S.C. § 119(e) to U.S. Patent Application No. 62 / 950,707, filed on December 19, 2019, and U.S. Patent Application No. 62 / 946,498, filed on December 11, 2019. Each of these applications is hereby incorporated by reference in its entirety.

Background Art

[0002] A typical near - eye display includes an image generator for generating an image, a light combiner for combining the image with ambient light, and imaging optics for focusing the image for a user who uses the near - eye display. The image generator may have pixels that reflect light (e.g., liquid crystals on a silicon device) or pixels that emit light (e.g., an array of organic light - emitting diodes (OLEDs)). In either case, the image generator is typically not within the user's field of view. Instead, it may be outside the user's field of view and project a beam at an angle with respect to the user's field of view.

[0003] The light combiner brings the light from the image generator into the user's field of view. For example, the light combiner may be a cube beam splitter having one surface or port that is perpendicular to the user's field of view and faces the user's eye. The light from the image generator enters one of the other ports of the beam splitter and is re - directed through the port facing the user's eye. When the near - eye display is an augmented reality display, the light combiner combines the light from the image generator with external light and projects the combined light onto the user's eye.

[0004] The imaging optical element focuses the image generated by the image generator. The imaging optical element can be either pupil-forming or non-pupil-forming. The pupil-forming optical system generates an intermediate image at a point between the image generator and the eye. This image should be formed far enough away from the eye for the eye to focus on the image. The non-pupil-forming optical systems do not generate an intermediate image. Instead, they typically cause the image to be focused at infinity so that the eye appears to be in focus when relaxed (i.e., when focused at a distance). The parameters of the imaging optical element in a near-eye display include (1) the eye clearance (the distance between the end of the last optical element and the exit pupil, typically 20 mm), (2) the exit pupil distance (the distance between the vertex of the last optical element and the exit pupil), (3) the eyebox (often corresponding to the exit pupil) (including the range of angular and lateral positions of the eye at the exit pupil distance from which the entire image generated by the display can be seen), (4) the depth of field and (5) the field of view.

Summary of the Invention

[0005] More recently, see-through image generators have become available in the form of transparent OLED arrays. A near-eye display having a transparent OLED array or other see-through display does not require an optical combiner. Instead, the see-through display is placed directly within the user's field of view and can be adjusted to generate a changing virtual image. The optical element between the see-through display and the user's eye helps to focus the virtual image.

[0006] The technology of the present invention utilizes a see-through display, which is coupled to a dynamically switchable optical element to focus a virtual image for the user. This technology can be implemented as a near-eye display that is brought very close to the eye, such as glasses, and can be used as an augmented reality device. Such a near-eye display includes an optical element that can focus light using electronically actuated components without moving parts. This allows the near-eye display to be adjusted and focused for each individual's optical prescription. Also, the optical element can be used to focus on the virtual image source within the near-eye display and switch it on and off as desired, thereby enabling the user to see the real world without the presence of the virtual image. The optical element can also rapidly switch off and on to combine the virtual image with the image of the real world so that the observer perceives the images of the virtual and real worlds as if they were seen simultaneously. Further, the optical element can rapidly translate or reposition the focus of the lens that focuses on the virtual image. This rapid translation can be used to increase the apparent number of visible pixels and improve / increase the resolution.

[0007] The near-eye display of the present invention may include an array of light-emitting transparent pixels that optically communicates with an array of switchable microlenses. During operation, the array of light-emitting transparent pixels transmits ambient light and emits light towards the eye of the near-eye display wearer. The array of switchable microlenses focuses the light to form a virtual image perceived by the near-eye display wearer.

[0008] The array of light-emitting transparent pixels and the array of adjustable microlenses may be embedded in the spectacle lenses. The array of light-emitting transparent pixels may be at least 100 pixels × 100 pixels or more. There may be one switchable microlens per light-emitting transparent pixel within the array of light-emitting transparent pixels. And the array of switchable microlenses can be switched between a focused state and an unfocused state at a rate of at least 60 Hz.

[0009] Each switchable microlens may be an electroactive lens that focuses light to a focal point when the light is in a first polarization state and transmits the light without focusing the light to a focal point when the light is in a second polarization state. In this case, the near display may include a polarization adjuster (e.g., a dynamic half-wave plate) that optically communicates with the electroactive lens. The polarization adjuster can switch light from a corresponding transparent light-emitting pixel that emits light in the first polarization state between the first polarization state and the second polarization state at a rate of at least 60 Hz.

[0010] The near-eye display may also include an array of tilt mechanisms that optically communicate with an array of light-emitting transparent pixels and an array of switchable microlenses. These tilt mechanisms can direct light emitted by the array of light-emitting transparent pixels between resolvable angles, for example, at a rate of at least 60 Hz. In this case, a first number of pixels may be present within the array of light-emitting transparent pixels, and the tilt mechanisms can direct light between resolvable points quickly enough for the array of switchable lenses to form a virtual image having a second number of pixels that is greater than the first number of pixels.

[0011] Each tilt mechanism may include a polarization adjuster that optically communicates with a polarization-selective beam director. The polarization adjuster switches light from a corresponding transparent light-emitting pixel between the first polarization state and the second polarization state at a rate of at least 60 Hz. Also, the polarization-selective beam director directs light in the first polarization state in a first direction and light in the second polarization state in a second direction. This polarization-selective beam director may be a static polarization-selective beam director (e.g., a crystal optics or polarization thin-film beam splitter), or a dynamic polarization-selective beam director that includes a birefringent liquid crystal material actuated by a voltage supply.

[0012] The near-eye display may also include an array of fixed microlenses that optically communicates with the array of adjustable microlenses and focuses light.

[0013] Another near-eye display of the present invention includes an array of light-emitting transparent pixels having a first number of pixels optically communicating with an array of polarization adjusters, an array of polarization-selective tilt mechanisms, and an array of switchable microlenses. During operation, the array of light-emitting transparent pixels transmits ambient light and emits light in a first polarization toward the eyes of the near-eye display wearer. The array of polarization adjusters switches light between a first polarization state and a second polarization state at a rate of at least 60 Hz. The array of polarization-selective tilt mechanisms directs light in the first polarization state in a first direction and light in the second polarization state in a second direction. And the array of switchable microlenses focuses the light in the first polarization state and the light in the second polarization state to form a virtual image having a second number of pixels greater than the first number of pixels perceived by the near-eye display wearer.

[0014] All combinations of the foregoing concepts, and additional concepts discussed in more detail below (assuming such concepts are not mutually inconsistent), are considered to be part of the subject matter of the invention disclosed herein. In particular, all combinations of the subject matter recited in the claims, which appear at the end of this disclosure, are considered to be part of the inventive subject matter disclosed herein. Terms used in any disclosure incorporated herein by reference and explicitly used herein should be given meanings that most closely match the specific concepts disclosed herein.

Brief Description of the Drawings

[0015] Those skilled in the art will understand that the drawings are presented primarily for illustrative purposes and are not intended to limit the scope of the subject matter of the invention described herein. The drawings are not necessarily to scale, and in some instances, various aspects of the subject matter of the invention disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate understanding of different features. In the drawings, like reference characters generally mean like features (e.g., functionally similar and / or structurally similar elements).

[0016]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0017] Figure 1 shows an exemplary near-eye display 10 having transparent light-emitting pixels 5 and an adjustable focusing and beam steering element 7 (also referred to as an adjustable microlens). This near-eye display 10 may be mounted on an eyewear frame (not shown), or attached to an eyewear frame, or may be embedded in the eyewear lens 12 without light output or. Such lenses may also include an embedded controller 14 and a power source 16 for operating and powering the pixels 5 and the adjustable microlens 7. The controller 14 and / or the power source 16 may also be attached to the frame, or embedded within the frame, and may be connected to the pixels 5 and the adjustable microlens 7 via a wired or wireless connection.

[0018] The pixel 5 can be implemented as a transparent array of OLEDs that emit red, green, and blue light. The typical shape of pixels fabricated today is rectangular or circular, but any other suitable shape may be used, and the shape is mainly limited by better manufacturing methods. An array of pixels arranged in a 2-pixel by 3-pixel grid can be used to display useful characters. Generally, a near-eye display with more pixels has a finer spatial resolution, and a suitable near-eye display has an array of 1920 pixels by 1080 pixels. Other arrays may be several times this size. The pixel pitch can range from a few millimeters to hundreds of nanometers, or even down to 10 nanometers or less.

[0019] Each pixel 5 is separated from a corresponding adjustable focusing and beam steering element 7 (also referred to as an adjustable microlens) by a distance 4. Depending on the number of pixels 5, the lateral dimension of each pixel 5, and the pixel pitch, there may be one pixel 5 per adjustable microlens 7, or multiple pixels 5 per adjustable microlens 7. For example, if each pixel 5 emits light of only one color (e.g., red, green, or blue light), there may be at least one pixel 5 that emits red light, one pixel 5 that emits green light, and one pixel 5 that emits blue light per adjustable microlens 7. In this case, the pixels 5 may be arranged in a Bayer pattern or other suitable pattern in order to provide a full-color image. Larger pixels can be 1 mm × 1 mm. Smaller pixels can have a length or width of 6.3 microns or less. The pitch and lateral dimension of the microlenses can match those of the pixels, e.g., on the order of 10 nm, 100 nm, 1 μm, 10 μm, 100 μm, 1 mm, or 10 mm.

[0020] During operation, each pixel 5 emits light 6 towards a corresponding adjustable microlens 7. The adjustable microlens 7 steers and / or focuses the light 6, whereby the eye 8 can focus the light onto a focal point 9 on the retina. Adjusting the distance 4 between the pixel 5 and the microlens 7 changes the degree of optical focusing by the lens 7 and achieves a desirable amount of pre-focus for the eye 8 to correctly focus the light onto the focal point 9. This adjustment of the distance 4 adapts the optical element (microlens 7) to the eye's optical prescription 8.

[0021] Figure 2 illustrates in more detail a single pixel 5 and a single adjustable microlens 7 of the near-eye display 10. The adjustable microlens 7 includes a first polarizer (switchable half-wave plate) 20, a second polarizer (switchable half-wave plate) 85, and a switchable lens 105 in series with an adjustable tilt mechanism / beam steering element 55. The first polarizer 20 and the second polarizer 85 switch the polarization state of the light passing through the adjustable microlens 7 between a first linearly polarized state 15 (e.g., perpendicular to the plane of the figure / drawing) and a second linearly polarized state 50 (e.g., parallel to the plane of the figure / drawing). In other versions of the adjustable micropixel, the polarizer may switch the light between other polarization states, such as linearly polarized states of ±45° or circularly polarized states of left and right rotation. The adjustable tilt mechanism / beam steering element 55 and the switchable lens 105 steer and focus the light in one polarization state but not in the other.

[0022] The adjustable microlens 7 functions by using a polarizer to switch the polarization state of the light 130 emitted by the pixel 5, whereby the light 130 is steered or focused by the tilt mechanism / beam steering element 55 and the switchable lens 105, respectively, or passes through without changing these elements. During operation, the pixel 5 emits a light beam 130 in a polarization state 15 perpendicular to the plane of the figure / drawing (this polarization state is indicated by X, which is the tail of the arrow representing the polarization vector pointing to the plane of the figure / drawing). The light 130 enters the polarizer 20 in the polarization state 15 and then emerges in the polarization state 50. The polarization state 50 is a symbol used to identify that the linear polarization direction is parallel to the plane of the figure / drawing, i.e., the figure / drawing is oriented from left to right or right to left.

[0023] Each pixel 5 may be implemented as an OLED that emits light of a single color (e.g., red, green, or blue) in a first polarization state 15. The pixel 5 may also be configured to emit randomly polarized light. In this case, the light can be polarized in the first polarization state 15 using a polarization filter, or passed through a system of randomly polarized components that only affect the components of the light in the desired polarization state and do not affect the components of the light in other polarization states.

[0024] Polarization switching and beam steering elements of an adjustable microlens The first polarization adjuster 20 is a half-wave plate that can switch between a non-delay in the first state and a half-wavelength delay in the second state. An exemplary switching speed for this component is 30 milliseconds, but it can range from 5 to 300 milliseconds depending on the liquid crystal used. The first polarization adjuster 20 is composed of a first substrate 25 and a second substrate 30, and a layer of liquid crystal 27 (e.g., Merck MLC-2140) is sandwiched and sealed between the two substrates 25 and 30. On the surface of the first substrate 25, there is a first electrode 40 made of a transparent and conductive coating (e.g., indium tin oxide (ITO)), and a first transparent alignment layer (not shown, e.g., a polyimide made from Nissan Sunever 410 polyimide varnish) on the ITO. Typically, the first alignment layer is applied, cured, and then polished with a felt cloth to align the desired alignment of the liquid crystal. Adjacent to the first electrode 40 is the liquid crystal 27.

[0025] On the surface of the second substrate 30, there is a second electrode 35 made of a transparent conductive material (e.g., ITO). On the second electrode 35, there is a second alignment layer. The first and second alignment layers are polished or oriented so as to align liquid crystal molecules in orthogonal directions. In the embodiment shown in FIG. 2, the first alignment layer is configured to align adjacent liquid crystal molecules 27 parallel to the second polarization state 50 (parallel to the plane of the page), and the second alignment layer is configured to align adjacent liquid crystal molecules parallel to the first polarization state 15 (perpendicular to the plane of the page). These alignment layers appear to intersect when viewed along the optical axis of an adjustable microlens where the first polarization state and the second polarization state are perpendicular.

[0026] This crossed alignment layer configuration causes the liquid crystal molecules to assume a twisted configuration 45 in the absence of an applied voltage. That is, in the relaxed state, the liquid crystal molecules are aligned in an orientation / direction 50 close to the first substrate 25, aligned in an orientation / direction 15 close to the second substrate 30, aligned midway between the orientation 50 and the orientation 15 in the middle of the liquid crystal layer, and as the liquid crystal approaches the first electrode 40 and the second electrode 35 respectively, the twist gradually increases in a direction close to the orientation 50 and the orientation 15. When the liquid crystal 27 is in the twisted configuration 45, the first polarization adjuster 20 changes the polarization state of the incident light 130 from the first polarization state 15 to the second polarization state 50. When a voltage is applied to the first electrode 40 and the second electrode 35, the twist of the liquid crystal 27 is untwisted (becomes straight). The light 130 that propagates through the first polarization adjuster 20 when the liquid crystal 27 is not twisted remains in the first polarization state 15.

[0027] FIGS. 3A and 3B respectively show the first polarization adjuster 20 in its off state and on state. FIG. 3A shows a voltage source 145 connected to the electrode 35 and the electrode 40. When this voltage source 145 is off, the liquid crystal 27 is in a twisted alignment 45 state. This is called the off state. In FIG. 3B, the voltage source 145 is on, and as a result, the liquid crystal 27 is reoriented to a linear or untwisted alignment 135 where the liquid crystal molecules are aligned perpendicular to the substrates 35 and 40 of the first polarization adjuster 20. This is called the on state.

[0028] Referring again to FIG. 2, the tilt mechanism 55 consists of two wedge-shaped structures 60 and 65. The first structure 60 may be made of a solid material such as glass, and the second structure 65 may be constructed from either a solid birefringent material such as quartz or a cavity containing an adjustable birefringent material such as liquid crystal. (In these cases, the tilt mechanism 55 can be implemented as a Glan-Thompson polarizer, Rochon prism, Wollaston prism, calcite beam displacer, or other suitable crystal polarizer.) When the second structure 65 is constructed from a solid birefringent material, the solid birefringent material is oriented such that its refractive index matches that of the first structure 60 along the second polarization direction 50, while its refractive index is different from that of the first structure 60 along the first polarization direction 15. The operation of the static tilt mechanism 55 is controlled by the first polarization adjuster 20. When the polarization is rotated in one direction, no tilt occurs. When the polarization is rotated in the opposite direction, tilt occurs. Thus, the speed of this component is the same as the speed of the polarization adjuster. This is a preferred embodiment.

[0029] In an alternative embodiment, instead, the second structure 65 may be configured as a sealed cavity containing an electrically actuated birefringent liquid such as a liquid crystal material. In this case, a third substrate 70 may be added to provide one boundary of the cavity. One side surface of the first structure 60 provides another boundary of the cavity. A side seal structure (not shown) seals the liquid crystal within the cavity.

[0030] In this configuration, transparent electrodes 75 and 80 are provided on the opposing side surfaces of the cavity (e.g., on the surfaces of the first structure 60 and the third structure 70 that form the boundaries of the cavity). These electrodes 75 and 80 perform the same functions as electrodes 35 and 40 of the first polarization adjuster 20. When no voltage is applied to electrodes 75 and 80, the liquid crystal is oriented so as to have a refractive index matching that of the first structure 60. In this state, light 130 passes through the tilt mechanism 55 without being affected by its propagation direction or its polarization state. When a voltage is applied to electrodes 75 and 80, the liquid crystal is reoriented so that its refractive index no longer matches that of the first structure 60. As a result, the light 130 passing through the tilt mechanism 55 is refracted at the boundary between the first structure 60 and the second structure 65. This refraction steers the light 130 without changing the polarization state of the light.

[0031] Figures 4A and 4B show a liquid crystal tilt mechanism 55 having a voltage source 150 connected to electrodes 75 and 80. Figure 4A shows the tilt mechanism when the voltage source 150 is off, and Figure 4B shows the tilt mechanism when the voltage source 150 is on. When the voltage source 150 is off, since the light 140 in the second polarization state 50 has the same refractive index in both the liquid crystal 65 and the first structure 60, no optical effect (tilt or steering) occurs. When the voltage source 150 is on, the liquid crystal 65 reorients itself to create a refractive index mismatch at the boundary between the liquid crystal 65 and the first structure 60 for the light 155 in the second polarization state 50. As a result, as shown in Figure 4B, tilting of the light beam 155 occurs at the boundary. The tilt angle is large enough to produce a spot that can be resolved from the spot generated when the tilt mechanism is off (i.e., since it is the corresponding spot formed by the tilted beam and the non-tilted beam in the plane of the virtual image, the tilt angle is resolvable). The light beam 155 is refracted again when it exits the first structure 60 and enters free space.

[0032] FIG. 4B shows the tilting mechanism 55 operating alone without other components attached. However, in one preferred embodiment, the tilting mechanism 55 is directly coupled to another component with the same refractive index. Since the refractive index does not change across this interface, the beam of light emerging should not refract when leaving the tilting mechanism 55.

[0033] The tilting of light occurs only for one polarization direction of light (here, the second polarization state 50). Incident light in the orthogonal polarization state (the first polarization state 15) propagates through the tilting mechanism 55 without bending or tilting regardless of whether the voltage supply unit 140 is on or off.

[0034] When the liquid crystal in the cavity version of the tilting mechanism 55 is a planar liquid crystal (rather than a vertically aligned liquid crystal), the amount of change in the refractive index of the liquid crystal is controlled by the voltage applied in an analog manner, making the tilting mechanism 55 an analog - adjustable device. An example of the liquid crystal is Merck MLC - 2140, which typically responds to a peak - to - peak voltage change of 0.5 volts to 8 volts. Typically, the voltage is an alternating current (AC) sine wave or square wave with a frequency typically between 15 and 60 Hz. Lower frequencies can be used, but flicker may become visible. Higher frequencies can be used, but in that case, the power consumption increases.

[0035] FIGS. 5A and 5B illustrate how the tilting mechanism 55 and the first polarization adjuster 20 cooperate to select whether to tilt or steer light. As shown in FIG. 5A, when the first polarization adjuster 20 is in the off state, no tilting occurs regardless of the on - state or off - state of the liquid crystal in the tilting mechanism 55. As shown in FIG. 5B, tilting occurs when both the first polarization adjuster 20 and the tilting mechanism 55 are on. Since the liquid crystal layer 27 of the polarization switch 20 is much thinner than the liquid crystal layer of the tilting mechanism 55, the first polarization adjuster 20 switches states much faster than the tilting mechanism 55. Thus, the on - off of the tilting function of the tilting mechanism can be switched faster than switching the tilting mechanism itself.

[0036] When the tilting mechanism 55 has a solid birefringent material instead of a birefringent liquid crystal, the amount of tilt provided by the tilting mechanism may not be adjustable, but the tilting mechanism can still quickly switch on and off by using the first polarizer 20. This is a preferred embodiment.

[0037] Two or more tilting mechanisms 55 (and, if desired, polarizers 20) may be connected in series or stacked with different tilt orientations relative to each other at different angles, and tilting can be performed in multiple directions. For example, one tilting mechanism stacked on another tilting mechanism oriented as in FIGS. 5A and 5B and rotated 90° around the optical axis (z) can generate four different beam steering angles or tile angles: two from left to right and two "inward and outward" with respect to the plane of FIGS. 5A and 5B.

[0038] Polarization switching and focusing elements of an adjustable microlens Referring again to FIG. 2, the light emerging from the tilting mechanism 55 enters the second polarizer 85. Similar to the first polarizer, the second polarizer 85 may be a half-wave plate that can switch between a non-retarded state in the first state and a half-wave retardation state in the second state. The liquid crystal is in a twisted configuration 90 (the same as configuration 45) when no power is applied to the second polarizer 85 and in an untwisted configuration when power is applied. In the twisted (off) configuration 90, the second polarizer 85 converts light in the first polarization state 15 to the second polarization state 50. Also, in the untwisted (on) state, light in the first polarization state 15 propagates through the second polarizer 85 without changing its state.

[0039] As shown in FIG. 2, the light emerging from the second polarization adjuster 85 enters a switchable lens 105 that consists of a solid component 115 having a concave and a planar substrate 110 that are joined together to form a sealed cavity 100. There is a first electrode 120 on the concave surface and a second electrode 125 on the surface of the planar substrate 110 facing the concave surface. These electrodes 120 and 125 are transparent and are coated with an alignment layer in parallel or anti-parallel polishing / alignment directions. (The alignment layers in the polarization adjuster are polished in directions orthogonal to each other, while the alignment layers in other components are usually polished parallel or anti-parallel to each other.) There is an amount of liquid crystal in the cavity, and its birefringent orientation is oriented to match the refractive index with respect to the structure 115 when no voltage is applied to the electrodes 120 and 125. In this off state, regardless of the polarization, the light passes through the lens 105 without being affected in its propagation direction. When a voltage is applied to the electrodes 120 and 125, the liquid crystal molecules reorient themselves. This reorientation increases the apparent refractive index of the liquid crystal material and causes the light passing through the switchable lens 105 to be focused.

[0040] The switchable lens can have an on-state focal length of about 1 mm to about 25 mm. Depending on the liquid crystal used and the size of the lens, it can be switched at a speed of about 3 milliseconds or about 300 milliseconds. The light output of the lens may be only on / off, or it may be analog-adjustable over a certain range. Small lenses (e.g., 1 mm in diameter) are usually switched faster than larger lenses (e.g., 3 mm in diameter), and liquid crystals with low rotational viscosity are usually switched faster than those with high rotational viscosity.

[0041] The cavity 100 may also be constructed from a solid and / or non-adjustable birefringent material that is similarly oriented. In this case, the switchable lens 105 may be operable as a binary on / off component. Similarly, the planar substrate 110 can be replaced by another concave or convex surface by the substrate to form a cavity in the shape of a biconvex lens or a meniscus lens. The substrate surface can also be patterned in the shape of a Fresnel, diffractive, or stepped surface.

[0042] Figures 6A and 6B show a switchable lens 105 having a voltage supply 160 connected to electrodes 120 and 125. Cavity 100 is filled with liquid crystal. When the voltage supply 160 is off, light 165 passes through cavity 100 (and switchable lens 105), and no optical effect occurs. This is because the refractive index of the liquid crystal along the optical axis of the switchable lens is the same as the refractive index of element 115 for light polarized in the first polarization state 15. This is the state shown in FIG. 6A. When the voltage supply 160 is on and a voltage is applied between electrodes 120 and 125, the liquid crystal in cavity 100 aligns with the applied electric field. This causes the refractive index of the liquid crystal along the optical axis of the switchable lens to change, focusing the light polarized in the first polarization state 15, for example, at focus 170. Due to the birefringence of the liquid crystal, switchable lens 105 does not focus light in the second polarization state 50 even when voltage source 160 is on.

[0043] When a planar liquid crystal, for example, Merck - MLC - 2140 is used, the refractive index can be adjusted in an analog manner, and the position of focus 170 can be adjusted analogously. Thereby, as shown in FIG. 1, the focal length of the adjustable microlens 7 can be adjusted without changing the distance 4 between the adjustable microlens 7 and the pixel 5.

[0044] In order for the switchable lens 105 to focus the incident light, the polarization of the light should be aligned with the polishing direction of the array layer of the switchable lens and, in this embodiment, is parallel or anti-parallel to the first polarization state 15. In some cases, depending on the state of the components in front of the light path, the light reaching the incident point of the lens 105 may be in a second polarization state 50. In these cases, if the beam is intended to be focused, the second polarization adjuster 85 switches the incident light from the second polarization state 50 to the first polarization state 15 so that the switchable lens 105 can focus the beam. Similarly, when the light hitting the second polarization adjuster 85 is in the first polarization state 15 and the second polarization adjuster 85 is in the off state, the light emerges from the second polarization adjuster 85 in an undesired orientation (i.e., the second polarization state 50 as in Figure 3A). In these cases, the second polarization adjuster 85 should be on to ensure that the light reaching the switchable lens 105 is in the first polarization state 15.

[0045] Figures 7A and 7B show the operation of the switchable lens 105 in series with the second polarization adjuster 85 (which is connected and controlled and operates in the same manner as the first polarization adjuster 20). In Figure 7A, the incident light is in the second polarization state 50, the second polarization adjuster 85 is off, and the switchable lens 105 is on. The second polarization adjuster 85 converts the incident light from the second polarization state 50 to the first polarization state 15, and the switchable lens 105 focuses the light to the focal point 170. In Figure 7B, the incident light is in the first polarization state 15, the second polarization adjuster 85 is on, and the switchable lens 105 is on. The incident light propagates through the second polarization adjuster 85 without changing its polarization state and is focused to the focal point 170 by the switchable lens 105.

[0046] The second polarization adjuster 85 switches states (i.e., on and off) much faster than the switchable lens 105 and can be used as a faster optical output on / off switch for the switchable lens 105. The switchable lens 105 may be toggled on and off by the faster second polarization adjuster 85 even after being adjusted to the desired optical output and while the switchable lens 105 remains in the on state. Alternatively, the liquid crystal within the lens cavity 100 may be a cholesteric liquid crystal, removing the polarization aspects of the system and the second polarization adjuster 85 and turning the lens into a binary switchable on / off optical element.

[0047] FIG. 7A also shows an optical filter 175 on the surface of the second polarization adjuster 85 closest to the switchable lens 105. Photoactivatable curable polymers and / or monomers can be added to the liquid crystal in the cavity 100 to freeze or fix the optical output of the switchable lens after the optical output has been adjusted to the user's prescription. If the liquid crystal in the polarization adjuster is not to be frozen or fixed during the lens curing process, the passband of the filter 175 can be selected to block the photoactivation / curing wavelength used to cure the polymer in the lens cavity 100 from reaching the second polarization adjuster 85. This approach can be utilized to adapt a near-eye display to a particular user's eye prescription and then freeze it in place to simplify the system. If a photosensitive polymer is not used in the polarization adjuster and the liquid crystal used is UV stable, the filter 175 is not required.

[0048] Steering and / or focusing of light by a near-eye display Figures 8 to 10 show the operation of the pixel 5 and the fully adjustable microlens 7 in the near-eye display 10 having the static tilt mechanism 55. Figure 8 shows a system in which the first polarizer 20 is set to tilt the light and turn off the lens 105 in the tilt mechanism 55. The system tilts the light but does not focus it. Figure 9 shows a system in which the first polarizer 20 is set to transmit the light without tilting and turn on the lens 105 in the tilt mechanism 55. Figure 10 shows the first polarizer 20 set to tilt the light from the on-state pixel 5 and the lens 105. The light is tilted and focused.

[0049] Table 1 is a truth table showing whether the adjustable microlens 7 bends or focuses the light from the pixel 5 for different combinations of settings of the first polarizer 20, the second polarizer 85, and the switchable lens 105 having the static tilt mechanism 55.

[0050]

Table 1

[0051] In some of the above exemplary component states, the light passes through the adjustable microlens 7 without causing focusing or tilting. This can be described as the "all-off state" of the adjustable microlens. This state can be used in a desirable state that allows the user to view real-world objects beyond the pixel 5 / near-eye display 10.

[0052] The components are shown separated for clarity in Figure 9, but they may be joined together without an air interface between them (thus, hardly or no refraction occurs), as shown in Figures 8 and 10. In other words, the components can be integrated into the optical block without moving parts. This optical block is more robust than individual components and is less affected by vibrations. If the components are made of a material with a low coefficient of thermal expansion, the optical block may also be less affected by temperature variations.

[0053] Near-eye display with adjustable and fixed microlenses Figure 11 shows an alternative near-eye display 11 with an adjustable microlens 7 that is coupled to each respective fixed lens 3. The fixed lens 3 may be a conventional lens made of glass or plastic and formed together within a microlens array. The fixed lens 7 reduces the adjustable range of the adjustable microlens 7 such that a thinner and faster-switching layer of liquid crystal can be used for the polarizer, tilt mechanism, and switchable lens of the adjustable microlens 7. For example, if the total desired adjustment range is 300 to 500 diopters of light output, the fixed lens 3 may be fabricated at 300 diopters of light output, and the adjustable microlens 7 may have an adjustment range of 0 to 200 diopters instead of 0 to 500 diopters.

[0054] In both the near-eye display 10 of FIG. 1 and the near-eye display 11 of FIG. 11, the pixels 5 and the adjustable microlenses 7 are shown as having all features, which means that pixel light emission, polarization adjustment, tilting, and focus change can be achieved. During operation, not all features may be desired at once. In these cases, only the parts necessary to achieve the desired goal may be included in the deployed system, while other parts may be omitted.

[0055] The planar and concave surfaces, orientations, and birefringence of the liquid crystal molecules described above and illustrated in each figure are merely examples, and other substrate / lens shapes and liquid crystal orientations may be used instead to achieve the desired light bending and focusing. This focusing may be in different directions, such as divergence instead of convergence, for example. Similarly, the tilt mechanism 55 may be arranged to tilt the light to the left (instead of to the right), and the polarizers 20 and 85 may be modified or arranged to switch the polarization of the incident light from a second polarization state 50 to a first polarization state 15 (instead of the reverse).

[0056] The adjustable lens described above uses liquid crystal as the material for changing the refractive index of a specific layer, but other materials with variable refractive indices may be used, including lithium niobate (LiNbO3), barium titanate (BaTiO3), lithium tantalate (LiTaO3), and many others.

[0057] Beam steering for improving apparent near-eye display resolution Using the high-speed tilt or beam steering provided by the adjustable microlens 7, the apparent spatial resolution of the near-eye displays 10 and 11 can be increased. By switching the focus of each microlens between a pair of resolvable points faster than the flicker fusion threshold frequency, the user can be made to perceive a resolution higher than that of the display device. The flicker fusion threshold frequency is the frequency at which an intermittent light stimulus appears completely stable to an average observer. The flicker fusion threshold frequency depends on several factors but is generally between 15 Hz and 60 Hz.

[0058] Thanks to the high switching rate of the first polarizer 20 and the second polarizer 85, the adjustable microlens 7 can steer and focus the light from pixel 5 back and forth between two points at a rate exceeding the flicker fusion threshold. As a result, the wearers of the near-eye displays 10, 11 perceive two separate pixels when there is actually only one. If the adjustable microlens 7 switches the light from pixel 5 between these two positions with a 50% duty cycle, each of the two apparent pixels should appear half as bright as the actual pixel 5.

[0059] Using this beam steering and focusing, the apparent pixel count of the near-eye displays 10, 11 can be doubled or quadrupled. For example, if the near-eye displays 10, 11 have an array of 100 pixels × 100 pixels and each has a corresponding adjustable microlens 7 as shown in FIG. 2, the apparent resolution of the near-eye display can be increased to 200 pixels × 100 pixels. If a second tilt mechanism 55 is added to each adjustable microlens 7 to tilt the beam in an orthogonal direction (e.g., vertically in addition to the left-right switching provided by the first tilt mechanism 55), the light from each pixel 5 can be shifted in two directions. This enables four apparent pixels to be projected from a single pixel. Thus, the 100 pixel × 100 pixel near-eye displays 10, 11 can be perceived as a 200 pixel × 200 pixel display.

[0060] The adjustable microlens 7 can also be switched between a focused state and an unfocused state faster than the flicker fusion threshold frequency using a second polarizer adjuster 85. When the switchable lens 105 with the second polarizer adjuster 85 faster than the flicker fusion threshold frequency is "turned off", the corresponding pixel 5 and the peripheral light appear superimposed on each other to the wearer of the near-eye displays 10, 11. In other words, the virtual image from the pixel 5 and the real image are simultaneously displayed. The wearer quickly and continuously alternates between two views, the view of the virtual image and the view of the real-world image, providing an illusion of the virtual image superimposed on the real-world image. Adjusting the luminance of the pixel 5 or the duty cycle of the second polarizer adjuster 85 changes the apparent luminance of the virtual image. (Alternatively, the same effect can be achieved by simply turning the pixel 5 on and off faster than the flicker fusion threshold frequency.)

[0061] Conclusion Although various embodiments of the invention have been described and illustrated herein, those skilled in the art will readily envision various other means and / or structures for performing the functions described herein and / or for obtaining the results and / or one or more of the advantages thereof, and each of such variations and / or modifications is to be regarded as within the scope of the embodiments of the invention described herein. More generally, those skilled in the art will readily understand that all parameters, dimensions, materials, and configurations described herein are meant to be illustrative and that the actual parameters, dimensions, materials, and / or configurations will depend upon the particular application(s) for which the teachings of the invention are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Accordingly, it is to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and their equivalents, embodiments of the invention may be practiced otherwise than as specifically described and claimed. Embodiments of the invention disclosed herein are directed to each individual feature, system, article, material, kit, and / or method described herein. Additionally, any combination of two or more such features, systems, articles, materials, kits, and / or methods is included within the scope of the invention disclosed herein if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0062] The above embodiments can be implemented by any of a number of means. For example, embodiments of the design and fabrication of the technology disclosed herein may be implemented using hardware, software, or a combination thereof. When implemented in software, the software code may be executed by any suitable processor or collection of processors, whether provided on a single computer or distributed among a plurality of computers.

[0063] Also, concepts related to various inventions may be embodied as one or more methods, and examples have been provided. The acts performed as part of the method may be ordered in any suitable manner. As a result, embodiments may be constructed in which the acts are performed in an order different from that illustrated, including performing some of the acts simultaneously, even if they are shown as consecutive acts in the exemplary embodiments.

[0064] All definitions defined and used in this specification should be understood to control dictionary definitions, definitions in incorporated documents by reference, and / or the ordinary meaning of the defined terms.

[0065] The indefinite articles "a" and "an" used in this specification and the claims should be understood to mean "at least one" unless clearly indicated otherwise.

[0066] The phrase "and / or" as used in this specification and the claims means "either or both" of the associated elements, i.e., elements that exist conjunctively in some cases and disjunctively in other cases. The multiple elements listed with "and / or" should be interpreted in the same manner, i.e., as "one or more" of the associated elements that are connected in parallel. Other elements may optionally exist in addition to the elements specifically identified by the "and / or" clause, whether or not they are related to the specifically identified elements. Therefore, by way of non-limiting example, a reference to "A and / or B", when used in conjunction with a syntax without limitations such as "comprising", can refer to, in one embodiment, only A (optionally including elements other than B), in another embodiment, only B (optionally including elements other than A), and in yet another embodiment, both A and B (optionally including other elements), etc.

[0067] As used in this specification and the claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" is inclusive, i.e., it includes at least one of a number of elements or a list of elements, and optionally additional items not in the list, but also includes two or more. Terms that are clearly indicated to the contrary, such as "only one of" or "exactly one of", or terms such as "consisting of" when used in the claims, refer to including exactly one element out of a number of or listed elements. Generally, the term "or" as used in this specification is to be construed as indicating an exclusive alternative (i.e., "one or the other but not both") only when preceded by an exclusive term such as "either", "only one of", "only one of the", or "exactly one of". "Consisting essentially of" shall have the ordinary meaning as used in the field of patent law when used in the claims.

[0068] As used in this specification and the claims, the phrase "at least one" in reference to a list of one or more elements means at least one element selected from any one or more of the elements in the list of elements, but does not necessarily include at least one of every element specifically recited in the list of elements, and is not to be construed as excluding any combinations of elements in the list of elements. Also by this definition, it is permitted that elements other than those specifically identified in the list of elements referred to by the phrase "at least one" may optionally exist, whether or not they are related to the specifically identified elements. Therefore, by way of non-limiting example, "at least one of A and B" (or equivalently "at least one of A or B", or equivalently "at least one of A and / or B") can refer to, in one embodiment, at least one A (optionally including elements other than B) where B does not exist and optionally including two or more A's, in another embodiment, at least one B (optionally including elements other than A) where A does not exist and optionally including two or more B's, and in yet another embodiment, at least one A optionally including two or more A's, and at least one B optionally including two or more B's (optionally including other elements).

[0069] In the claims, as well as in the above specification, all transitional phrases such as "comprising", "including", "carrying", "having", "containing", "involving", "holding", "composed of", and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" are to be considered closed or semi-closed transitional phrases, respectively, as defined in the United States Patent and Trademark Office's Manual of Patent Examining Procedure, Section 2111.03.

Claims

1. A near-eye display comprising: an array of light-emitting transparent pixels that transmit ambient light and emit light toward the eyes of the near-eye display wearer; an array of switchable microlenses optically communicating with the array of light-emitting transparent pixels and configured to focus the light to form a virtual image perceived by the near-eye display wearer; wherein the array of switchable microlenses is a liquid crystal lens optically communicating with a corresponding transparent light-emitting pixel within the array of light-emitting transparent pixels, the liquid crystal lens being configured to focus the light to a focal point when the light is in a first polarization state and transmit the light in a non-focused state when the light is in a second polarization state, and the liquid crystal lens being switchable between the focused state and the non-focused state; and a polarization adjuster disposed between the corresponding transparent light-emitting pixel and the liquid crystal lens, the polarization adjuster being switchable between a first state in which the polarization adjuster switches the light from the first polarization state to the second polarization state and a second state in which light in the first polarization state propagates through the polarization adjuster without changing its polarization state, the polarization adjuster being switchable faster than the liquid crystal lens switches between the focused state and the non-focused state. A near-eye display.

2. The near-eye display according to claim 1, wherein the array of light-emitting transparent pixels and the array of switchable microlenses are embedded in an eyeglass lens.

3. The near-eye display according to claim 1, wherein the array of light-emitting transparent pixels is at least 100 pixels × 100 pixels.

4. The near-eye display according to claim 1, wherein the array of switchable microlenses includes one switchable microlens per light-emitting transparent pixel within the array of light-emitting transparent pixels.

5. The near-eye display according to claim 1, wherein the array of switchable microlenses is configured to switch between the focused state and the unfocused state at a rate of at least 60 Hz.

6. The near-eye display according to claim 1, wherein the polarization adjuster is configured to switch the light from the corresponding transparent light-emitting pixel between the first polarization state and the second polarization state at a rate of at least 60 Hz.

7. The near-eye display according to claim 1, wherein the array of light-emitting transparent pixels is configured to emit the light in the first polarization state.

8. The near-eye display according to claim 1, further comprising an array of tilt mechanisms optically communicating with the array of light-emitting transparent pixels and the array of switchable microlenses and steering the light radiated by the array of light-emitting transparent pixels between resolvable angles.

9. The near-eye display according to claim 8, wherein the array of switchable microlenses is configured to steer the light from the array of light-emitting transparent pixels between resolvable points at a rate of at least 60 Hz.

10. The near-eye display according to claim 8, wherein the array of light-emitting transparent pixels includes a first number of pixels, and the array of tilt mechanisms forms the virtual image at a speed sufficient to form the virtual image with a second number of pixels greater than the first number of pixels, and the array of switchable lenses is configured to steer the light between the resolvable points.

11. The polarization adjuster is a first polarization adjuster, The array of tilt mechanisms is, A second polarization modulator for switching the light between the first polarization state and the second polarization state at a rate of at least 60 Hz from corresponding transparent light-emitting pixels within the array of light-emitting transparent pixels. A polarization-selective beam director optically communicating with the polarization modulator for directing light in the first polarization state in a first direction and light in the second polarization state in a second direction. The near-eye display according to claim 8, comprising: **Claim 12** The near-eye display according to claim 11, wherein the polarization-selective beam director is a static polarization-selective beam director. **Claim 13** The near-eye display according to claim 11, wherein the polarization-selective beam director is a dynamic polarization-selective beam director including a birefringent liquid crystal material actuated by a voltage supply. **Claim 14** The near-eye display according to claim 1, further comprising an array of fixed microlenses optically communicating with the array of switchable microlenses for focusing the light. **Claim 15** A method of operating a near-eye display comprising an array of light-emitting transparent pixels optically communicating with an array of switchable microlenses, the method comprising: The array of switchable microlenses comprising a polarization modulator and a liquid crystal lens that focuses light in a first polarization state and transmits light in a second polarization state. The method comprising: Radiating light from the array of light-emitting transparent pixels toward the eye of a near-eye display wearer; Transmitting ambient light through the array of light-emitting transparent pixels toward the eye of the near-eye display wearer; Switching the polarization modulator between a first state in which the polarization modulator switches the light from the first polarization state to the second polarization state and a second state in which light in the first polarization state propagates through the polarization modulator without changing its polarization state. switching the switchable microlens array between a focusing state in which the switchable microlens array focuses the light to form a virtual image perceived by the near-eye display wearer and a non-focusing state in which the switchable microlens array does not focus the light; A method comprising:

16. The method of claim 15, wherein switching the switchable microlens array between the focusing state and the non-focusing state comprises switching the polarization modulator between the first state and the second state at a rate of at least 60 Hz.

17. switching the switchable microlens array between the focusing state and the non-focusing state comprises: focusing the light to a focal point when the light is in the first polarization state; transmitting the light without focusing the light to the focal point when the light is in the second polarization state; 16. The method of claim 15, further comprising:

18. The method of claim 17, further comprising switching the polarization modulator between the first state and the second state faster than the liquid crystal lens changes state.

19.

20. The method of claim 17, wherein emitting the light from the array of light-emitting transparent pixels comprises emitting the light in the first polarization state.

21.

22. The method of claim 15, further comprising steering the light emitted by the array of light-emitting transparent pixels between resolvable angles at a rate of at least 60 Hz.

23.

24. The array of light-emitting transparent pixels includes a first number of pixels, 25. The method of claim 15, further comprising steering the light emitted by the array of light-emitting transparent pixels to form a virtual image having a second number of pixels greater than the first number of pixels. Claim 22 A near-eye display comprising: an array of light-emitting transparent pixels having a first pixel count, transmitting ambient light, and emitting light in a first polarization towards the eyes of the near-eye display wearer; a liquid crystal polarization modulator optically communicating with the array of light-emitting transparent pixels and having a liquid crystal layer thin enough to switch the light between the first polarization state and a second polarization state at a rate of at least 60 Hz; an array of polarization-selective liquid crystal tilt mechanisms optically communicating with the liquid crystal polarization modulator and each having a liquid crystal layer thicker than the liquid crystal layer of the liquid crystal polarization modulator, for directing the light in the first polarization state in a first direction and the light in the second polarization state in a second direction; and an array of switchable microlenses optically communicating with the array of light-emitting transparent pixels for focusing the light in the first polarization state and the light in the second polarization state to form a virtual image having a second pixel count greater than the first pixel count perceived by the wearer of the near-eye display.

Images