Near-eye display with array optics

Abstract

To provide a near-eye display using a transparent organic light-emitting diode (OLED).SOLUTION: Light from pixels can be switchably tuned and / or steered with tunable beam-steering and focusing elements (called as tunable micro-lenses). These tunable micro-lenses are arranged in an array and mated to the array of pixels, for example, by embedding in a spectacle lens. The tunable micro-lenses use fast-switching half-wave plates to selectively focus and / or tilt 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 tunable micro-lenses can double the apparent resolution of a near-eye display. And by switching between focusing and non-focusing at the same rate, the tunable micro-lenses can effectively superimpose virtual images from the pixels on the real-world image visible through the pixels.SELECTED DRAWING: Figure 2

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 Ser. No. 62 / 950,707, filed December 19, 2019, and U.S. patent application Ser. No. 62 / 946,498, filed December 11, 2019, each of which is incorporated herein by reference in its entirety. [Background technology]

[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 using the near-eye display. The image generator may have light-reflecting pixels (e.g., liquid crystal on silicon devices) or light-emitting pixels (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. Alternatively, it may be outside the user's field of view and project a beam at an angle to the user's field of view.

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

[0004] Imaging optics focus the image generated by the image generator. Imaging optics can be pupil-forming or non-pupillary. Pupil-forming optics create 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 it. Non-pupillary optics do not create an intermediate image. Instead, they typically focus the image to infinity, so that it appears in focus when the eye is relaxed (i.e., focused at a distance). Parameters of imaging optics in near-eye displays include (1) eye clearance (the distance between the edge of the last optic and the exit pupil, typically 20 mm), (2) exit pupil distance (the distance between the apex of the last optic and the exit pupil), (3) eyebox (often equivalent to the exit pupil) (which includes the range of angular and lateral positions of the eye at the exit pupil distance from which the entire image generated by the display is visible), (4) depth of field, and (5) field of view. Summary of the Invention

[0005] More recently, see-through image generators have become available in the form of transparent OLED arrays. Near-eye displays with transparent OLED arrays or other see-through displays do 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 produce a varying virtual image. Optical elements between the see-through display and the user's eye help to focus the virtual image.

[0006] The technology of the present invention utilizes a see-through display and couples it with dynamic, switchable optics to focus a virtual image for the user. This technology is useful for near-eye displays that can be brought very close to the eye, for example, in glasses, and used as an augmented reality device. These near-eye displays can be implemented as a virtual reality display. Such near-eye displays include optical elements that can focus light using electronically actuated components with no moving parts. This allows the near-eye display to be adjusted and focused for each individual's optical prescription. Optical elements can also be used to focus a virtual image source in the near-eye display and turn it on and off as desired, thereby allowing the viewer to see the real world without the virtual image present. Optical elements can also combine the virtual image with a real-world image and rapidly turn it off and on so that the viewer perceives the virtual and real-world images as if they were being viewed simultaneously. Furthermore, optical elements can rapidly translate or reposition the focal point of the lens that focuses the virtual image. This rapid translation can be used to increase the number of apparent visible pixels, improving / increasing resolution.

[0007] A near-eye display of the present invention may include an array of light-emitting transparent pixels in optical communication with an array of switchable microlenses. In operation, the array of light-emitting transparent pixels transmits ambient light and emits light toward the eyes of a near-eye display wearer. The array of switchable microlenses focuses the light to form a virtual image that is 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 an eyeglass lens. The array of light-emitting transparent pixels may be at least 100 pixels by 100 pixels, or may be larger. There may be one switchable microlens per light-emitting transparent pixel in the array of light-emitting transparent pixels. And, the array of switchable microlenses may be switchable between focused and unfocused states at a rate of at least 60 Hz.

[0009] Each switchable microlens may be an electro-active lens that focuses light to a focal point when the light is in a first polarization state and transmits 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 modulator (e.g., a dynamic half-wave plate) in optical communication with the electro-active lens. The polarization modulator can switch light from a corresponding transparent emissive pixel that emits light in the first polarization state between the first and second polarization states at a rate of at least 60 Hz.

[0010] The near-eye display can also include an array of tilting mechanisms in optical communication with the array of light-emitting transparent pixels and the array of switchable microlenses. These tilting mechanisms can steer 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, there can be a first number of pixels in the array of light-emitting transparent pixels, and the tilting mechanisms can steer the light between the resolvable angles fast enough that the array of switchable lenses forms a virtual image having a second number of pixels greater than the first number of pixels.

[0011] Each tilt mechanism may include a polarization adjuster in optical communication with the polarization-selective beam director. The polarization adjuster switches light from a corresponding transparent emissive pixel between a first polarization state and a second polarization state at a rate of at least 60 Hz. The polarization-selective beam director also directs light of the first polarization state in a first direction and light of the second polarization state in a second direction. The polarization-selective beam director may be a static polarization-selective beam director (e.g., a crystal optic or polarizing thin film beam splitter) or a dynamic polarization-selective beam director including a birefringent liquid crystal material actuated by a voltage supply.

[0012] The near-eye display may also include an array of fixed microlenses in optical communication with the array of adjustable microlenses for focusing light.

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

[0014] All combinations of the foregoing concepts, and additional concepts discussed in more detail below (provided such concepts are not mutually inconsistent), are considered to be part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are considered to be part of the inventive subject matter disclosed herein. The terms explicitly used in any disclosure incorporated by reference herein should be given the meaning most consistent with the specific concepts disclosed herein. [Brief explanation of the drawings]

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

[0016] [Figure 1]FIG. 1 shows a near-eye display. [Figure 2] FIG. 2 shows a pixel and adjustable microlens suitable for use in the near-eye display of FIG. [Figure 3] 3A and 3B illustrate the operation of the (first) polarization adjuster (liquid crystal waveplate) of FIG. [Figure 4] 4A and 4B illustrate the operation of the tilt mechanism of FIG. [Figure 5] 5A and 5B illustrate how the first polarization adjuster and tilt mechanism can work together to steer light. [Figure 6] 6A and 6B illustrate the operation of the switchable lens of FIG. [Figure 7] 7A and 7B illustrate how a second polarization adjuster and a switchable lens can work together to focus or collimate light. [Figure 8] FIG. 8 shows how the pixel and adjustable microlenses of FIG. 2 can steer collimated light. [Figure 9] FIG. 9 shows how the pixel and adjustable microlenses of FIG. 2 can focus light. [Figure 10] FIG. 10 shows how the pixel and adjustable microlenses of FIG. 2 can steer and focus light. [Figure 11] FIG. 11 shows an alternative near-eye display in which each pixel includes or is coupled to an adjustable lens, such as the lens in FIGS. 6A and 6B, in conjunction with a corresponding fixed lens. DETAILED DESCRIPTION OF THE INVENTION

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

[0018] The pixels 5 can be implemented as a transparent array of OLEDs emitting red, green, and blue light. Typical shapes for pixels fabricated today are rectangular or circular, but they can be any other suitable shape, limited primarily by better manufacturing methods. An array of pixels arranged in a 2-pixel by 3-pixel grid can be used to display useful characters. Near-eye displays generally have finer spatial resolution; a suitable near-eye display has an array of 1920 pixels by 1080 pixels. Other arrays can be many times this size. Pixel pitch can range from a few millimeters to hundreds of nanometers, or even 10 nanometers or less.

[0019] Each pixel 5 is separated from a corresponding adjustable focusing and beam steering element 7 (also called an adjustable microlens) by a distance 4. Depending on the number of pixels 5, the lateral dimensions 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 emitting red light, one pixel 5 emitting green light, and one pixel 5 emitting green light per adjustable microlens 7. In this case, the pixels 5 may be arranged in a Bayer pattern or other suitable pattern to provide a full-color image. Larger pixels may be 1 mm by 1 mm. Smaller pixels may have a length or width of 6.3 microns or less. The pitch and lateral dimensions of the microlenses may match those of the pixels, for example, on the order of 10 nm, 100 nm, 1 μm, 10 μm, 100 μm, 1 mm, or 10 mm.

[0020] In operation, each pixel 5 emits light 6 to a corresponding adjustable microlens 7. The adjustable microlens 7 steers and / or focuses the light 6 so that the eye 8 can focus the light at 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 to achieve a desired amount of pre-focus for the eye 8 to properly focus the light at the focal point 9. This adjustment of the distance 4 adapts the optical element (micro-lens 7) to the optical prescription 8 of the eye.

[0021] 2 illustrates in more detail a single pixel 5 and a single adjustable microlens 7 of near-eye display 10. Adjustable microlens 7 includes a first polarization adjuster (switchable half-wave plate) 20 in series with an adjustable tilt mechanism / beam steering element 55, a second polarization adjuster (switchable half-wave plate) 85, and a switchable lens 105. First polarization adjuster 20 and second polarization adjuster 85 change the polarization state of light passing through adjustable microlens 7 between a first linear polarization state 15 (e.g., perpendicular to the plane of the figure / drawing) and a second linear polarization state 16 (e.g., perpendicular to the plane of the figure / drawing). The polarization adjuster 55 switches between a linear polarization state 50 (e.g., parallel to the plane of the figure / drawing) of 45°. In other versions of the adjustable micropixel, the polarization adjuster may switch light between other polarization states, such as ±45° linear polarization states or left- and right-handed circular polarization states. The adjustable tilt mechanism / beam steering element 55 and switchable lens 105 steer and focus light in one polarization state but not the other.

[0022] The adjustable microlens 7 functions by using the polarization adjuster 20 to switch the polarization state of light 130 emitted by the pixel 5, so that the light 130 is either steered or focused by the tilt mechanism / beam steering element 55 and the switchable lens 105, respectively, or passes through these elements unchanged. In operation, the pixel 5 emits a light beam 130 with a polarization state 15 perpendicular to the plane of the figure / drawing (this polarization state is indicated by an X, the tail of the arrow representing the polarization vector, pointing into the plane of the figure / drawing). The light 130 enters the polarization adjuster 20 with polarization state 15 and subsequently emerges with polarization state 50. Polarization state 50 is a symbol used to identify linear polarization directions parallel to the plane of the figure / drawing, i.e., oriented left-to-right or right-to-left through the figure / drawing.

[0023] Each pixel 5 may be implemented as an OLED that emits monochromatic (e.g., red, green, or blue) light in a first polarization state 15. Pixels 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 polarizing filter, or passed through a randomly polarized system whose various components only affect light in the desired polarization state and not light components in other polarization states.

[0024] Tunable microlens polarization switching and beam steering elements The first polarization adjuster 20 is a half-wave plate that can be switched between a first state of no retardation and a second state of half-wave retardation. An exemplary switching speed for this component is 30 milliseconds, but can range from 5 to 300 milliseconds depending on the liquid crystal used. The first polarization adjuster 20 is comprised of a first substrate 25 and a second substrate 30, and is sandwiched between a layer of liquid crystal 27 (e.g., Merck MLC-2140) is sandwiched and sealed between two substrates 25 and 30. On the surface of the first substrate 25 is a first electrode 40 consisting of a transparent, conductive coating (e.g., indium tin oxide (ITO)), and on top of the ITO is a first transparent alignment layer (not shown, but e.g., polyimide made from Nissan Sunever 410 polyimide varnish). Typically, the first alignment layer is applied, cured, and then buffed with a felt cloth to the desired alignment orientation of the liquid crystal. Adjacent to the first electrode 40 is liquid crystal 27.

[0025] On the surface of the second substrate 30 is a second electrode 35 made of a transparent conductive material (e.g., ITO). On the second electrode 35 is a second alignment layer. The first and second alignment layers are polished or oriented to align the liquid crystal molecules in orthogonal directions. In the example 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 cross when viewed along the optical axis of the tunable microlens, which is perpendicular to the first and second polarization states.

[0026] This crossed alignment layer configuration causes the liquid crystal molecules to assume a twisted configuration 45 in the absence of an applied voltage: in a relaxed state, the liquid crystal molecules align in orientation / direction 50 near the first substrate 25, in orientation / direction 15 near the second substrate 30, and midway between orientation 50 and orientation 15 in the middle of the liquid crystal layer, where the liquid crystals are aligned with the first electrode 40 and the second electrode 30, respectively. As the orientation approaches 5, there is an increasing twist in the direction closer to orientation 50 and orientation 15. When the liquid crystal 27 is in the twisted configuration 45, the first polarization modulator 20 changes the polarization state of incident light 130 from the first polarization state 15 to the second polarization state 50. Applying a voltage to the first electrode 40 and the second electrode 35 causes the liquid crystal 27 to untwist (straighten). Light 130 propagating through the first polarization modulator 20 when the liquid crystal 27 is untwisted remains in the first polarization state 15.

[0027] Figures 3A and 3B show first polarization modulator 20 in its off and on states, respectively. Figure 3A shows a voltage source 145 connected to electrodes 35 and 40. When this voltage source 145 is off, liquid crystal 27 is in twisted orientation 45. This is referred to as the off state. 3B, voltage source 145 is on, resulting in reorientation of liquid crystal 27 into a linear or untwisted orientation 135 in which the liquid crystal molecules are aligned perpendicular to substrates 35 and 40 of first polarization modulator 20. This is referred to as the on state.

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

[0029] In an alternative embodiment, the second structure 65 may instead 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 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 located on opposite sides of the cavity (e.g., on the surfaces of the first and third structures 60 and 70 that bound the cavity). These electrodes 75 and 80 perform the same function as electrodes 35 and 40 of first polarization adjuster 20. When no voltage is applied to electrodes 75 and 80, the liquid crystal is oriented to be index-matched to the first structure 60. In this state, light 130 passes through tilting mechanism 55 unaffected by its propagation direction or its polarization state. Applying a voltage to electrodes 75 and 80 reorients the liquid crystal so that its index of refraction no longer matches that of the first structure 60. As a result, light 130 passing through tilting mechanism 55 is refracted at the boundary between first and second structures 60 and 65. This refraction steers light 130 without changing its polarization state.

[0031] 4A and 4B show liquid crystal tilting mechanism 55 with voltage source 150 connected to electrodes 75 and 80. FIG. 4A shows the tilting mechanism when voltage source 150 is off, and FIG. 4B shows the tilting mechanism when voltage source 150 is on. When voltage source 150 is off, light 140 in second polarization state 50 experiences the same refractive index in both liquid crystal 65 and first structure 60, so no optical effect (tilt or steering) occurs. When voltage source 150 is on, liquid crystal 65 tilts itself , creating a refractive index mismatch at the boundary between the liquid crystal 65 and the first structure 60 for light 155 of the second polarization state 50. This results in a tilt of the light beam 155 at the boundary, as shown in FIG. 4B. The tilt angle is large enough to produce a spot that can be resolved from the spot produced when the tilt mechanism is off (i.e., the tilt angle is resolvable because of corresponding spots formed by the tilted and untilted beams in the plane of the virtual image). The light beam 155 is refracted again as it exits the first structure 60 and enters free space.

[0032] 4B shows tilt mechanism 55 operating alone, with no other components attached. However, in one preferred embodiment, tilt mechanism 55 is directly coupled to another component with the same refractive index. Because the refractive index does not change across this interface, the exiting beam of light should not be refracted as it leaves tilt mechanism 55.

[0033] Tilting of light occurs only for one polarization direction of light (here, second polarization state 50). Incident light of the orthogonal polarization state (first polarization state 15) propagates through tilt mechanism 55 without bending or tilting, whether voltage supply 140 is on or not.

[0034] If the liquid crystal in the cavity version of tilt mechanism 55 is a planar liquid crystal (rather than a vertically aligned liquid crystal), the amount of change in the liquid crystal's refractive index can be controlled by an applied voltage in an analog fashion, making tilt mechanism 55 an analog-tunable device. An example of a liquid crystal is Merck MLC-2140, which typically responds to peak-to-peak voltage changes 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 power consumption increases.

[0035] 5A and 5B illustrate how the tilt mechanism 55 and the first polarization adjuster 20 work together 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 tilt occurs, regardless of the on or off state of the liquid crystal in the tilt mechanism 55. As shown in FIG. 5B, when both the first polarization adjuster 20 and the tilt mechanism 55 are on, tilt occurs. Because the liquid crystal layer 27 of the polarization switcher 20 is much thinner than the liquid crystal layer of the tilt mechanism 55, the first polarization adjuster 20 switches states much faster than the tilt mechanism 55. This allows the tilt function of the tilt mechanism to be switched on and off more quickly than the tilt mechanism 55 itself can be switched.

[0036] If the tilt mechanism 55 comprises a solid birefringent material instead of a birefringent liquid crystal, the amount of tilt provided by the tilt mechanism may not be adjustable, but the tilt mechanism can still be rapidly switched on and off by utilizing the first polarization adjuster 20. This is the preferred embodiment.

[0037] Two or more tilt mechanisms 55 (and polarization adjuster 20, if desired) may be serially connected or stacked with tilt orientations at different angles relative to each other, allowing tilting in multiple directions. For example, one tilt mechanism oriented as in Figures 5A and 5B and stacked on another tilt mechanism rotated 90° about the optical axis (z) can produce four different beam steering or tiling angles: two left-to-right, and two "in-out" with respect to the plane of Figures 5A and 5B.

[0038] Tunable microlens polarization switching and focusing element Referring again to Figure 2, light exiting tilt mechanism 55 enters second polarization adjuster 85. Like the first polarization adjuster, second polarization adjuster 85 may be a half-wave plate that can be switched between a first state of no retardation and a second state of half-wave retardation. When no power is applied to polarization modulator 85, it is in a twisted configuration 90 (same as configuration 45), and when power is applied, it is in an untwisted configuration. In the twisted (off) configuration 90, second polarization modulator 85 converts light in first polarization state 15 to second polarization state 50. In the untwisted (on) configuration, light in first polarization state 15 propagates through second polarization modulator 85 without changing state.

[0039] As shown in FIG. 2, light emerging from the second polarization modulator 85 enters a switchable lens 105, which consists of a solid component 115 having a concave and a planar substrate 110 joined together to form a sealed cavity 100. A first electrode 120 is located on the concave surface, and a second electrode 125 is located on the surface of the planar substrate 110 facing the concave surface. These electrodes 120 and 125 are transparent and coated with alignment layers with parallel or antiparallel polishing / alignment directions. (The alignment layers in the polarization modulator are polished in directions perpendicular to each other, while the alignment layers in other components are typically polished parallel or antiparallel to each other.) The cavity contains a volume of liquid crystal, whose birefringent orientation is oriented to be index-matched to the structure 115 when no voltage is applied to the electrodes 120 and 125. In this off state, light, regardless of polarization, passes through the lens 105 unaffected by its propagation direction. Applying a voltage to the electrodes 120 and 125 causes the liquid crystal molecules to realign themselves. This reorientation increases the apparent refractive index of the liquid crystal material, causing light passing through the switchable lens 105 to become more focused.

[0040] Switchable lenses can have on-state focal lengths of about 1 mm to about 25 mm. Depending on the liquid crystal and lens size used, they can be switched as fast as 3 milliseconds or as fast as 300 milliseconds. The light output of the lens can be on / off only or can be analog adjustable over a range. Small lenses (e.g., 1 mm diameter) typically switch faster than larger lenses (e.g., 3 mm diameter), and liquid crystals with low rotational viscosity typically switch faster than liquid crystals with high rotational viscosity.

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

[0042] 6A and 6B show a switchable lens 105 having a voltage supply 160 connected to electrodes 120 and 125. The cavity 100 is filled with liquid crystal. When the voltage supply 160 is off, light 165 passes through the cavity 100 (and the 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 the 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 the electrodes 120 and 125, the liquid crystal in the cavity 100 aligns with the applied electric field. This changes the refractive index of the liquid crystal along the optical axis of the switchable lens, causing light polarized in the first polarization state 15 to focus, for example, at a focal point 170. Due to the birefringence of the liquid crystal, the switchable lens 105 does not focus light in the second polarization state 50, even when the voltage supply 160 is on.

[0043] If a planar liquid crystal, e.g., Merck-MLC-2140, is used, the refractive index can be adjusted in an analog fashion, making the position of the focal point 170 analog adjustable. This allows the focal length of the adjustable microlens 7 to be adjusted without changing the distance 4 between the adjustable microlens 7 and the pixel 5, as shown in FIG.

[0044] In order for the switchable lens 105 to focus the incident light, the polarization of the light is The second polarization adjuster 85 should be aligned with the polishing direction of the alignment layer of the switchable lens 105, which in this example is parallel or anti-parallel to the first polarization state 15. In some cases, depending on the state of earlier components in the optical path, the light arriving at the point of incidence of the lens 105 may be in the second polarization state 50. In these cases, if the beam is 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, if the light striking 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 will emerge from the second polarization adjuster 85 in an undesired orientation (i.e., the second polarization state 50, as in FIG. 3A ). In these cases, the second polarization adjuster 85 should be on to ensure that the light arriving at the switchable lens 105 is in the first polarization state 15.

[0045] 7A and 7B illustrate the operation of the switchable lens 105 in series with the second polarization adjuster 85 (which is connected, controlled, and operates in the same manner as the first polarization adjuster 20). In FIG. 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 a focal point 170. In FIG. 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 by the switchable lens 105 to a focal point 170.

[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 light output on / off switch for the switchable lens 105. The switchable lens 105 may be adjusted to a desired light output and then switched on and off by the faster second polarization adjuster 85 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, eliminating the polarization aspect of the system and the second polarization adjuster 85, making the lens a binary switchable on / off optical element.

[0047] FIG. 7A also shows a light filter 175 on the surface of the second polarization adjuster 85 closest to the switchable lens 105. Light-activated curing polymers and / or monomers can be added to the liquid crystals in the cavity 100 to freeze or fix the light output of the switchable lens after the light output has been adjusted to the user's prescription. If the liquid crystals in the polarization adjuster should not be frozen or fixed during the lens curing process, the passband of the filter 175 can be selected to block the light-activating / curing wavelengths used to cure the polymer in the lens cavity 100 from reaching the second polarization adjuster 85. This approach can be used to adapt the near-eye display to a particular user's eye prescription and then freeze it in place, simplifying the system. If no photosensitive polymers are used in the polarization adjuster and the liquid crystals used are UV-stable, the filter 175 is not required.

[0048] Steering and / or focusing light with near-eye displays 8-10 show the operation of a pixel 5 and a fully adjustable microlens 7 in a near-eye display 10 with a static tilt mechanism 55. FIG. 8 shows a system in which the first polarization adjuster 20 is configured to cause the tilt mechanism 55 to tilt the light and the lens 105 to be in the OFF state. The system tilts but does not focus the light. FIG. 9 shows a system in which the first polarization adjuster 20 is configured to cause the tilt mechanism 55 to transmit the light without tilting and the lens 105 to be in the ON state. FIG. 10 shows the first polarization adjuster 20 configured to cause the tilt mechanism 55 to tilt the light from the pixel 5 and lens 105 in the ON state. The light is tilted and focused.

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

[0050] [Table 1]

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

[0052] Although the components are shown separated for clarity in Figure 9, they may be joined together without an air interface between them (and therefore little or no refraction), as shown in Figures 8 and 10. In other words, the components may be integrated into an optical block without moving parts. This optical block may be more robust and less susceptible to vibration than individual components. If the components are made of materials with low thermal expansion coefficients, the optical block may also be less susceptible to temperature fluctuations.

[0053] Near-eye display with adjustable and fixed microlenses FIG. 11 shows an alternative near-eye display 11 with adjustable microlenses 7 associated with respective fixed lenses 3. The fixed lenses 3 may be conventional lenses made of glass or plastic and formed collectively into a microlens array. The fixed lenses 7 reduce the adjustable range of the adjustable microlenses 7, allowing thinner, faster switching layers of liquid crystal to be used for the polarization adjusters, tilt mechanisms, and switchable lenses of the adjustable microlenses 7. For example, if the total desired adjustment range is 300-500 diopters of light output, the fixed lenses 3 may be made with 300 diopters of light output, and the adjustable microlenses 7 may have an adjustment range of 0-200 diopters rather than 0-500 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 adjustable microlenses 7 are shown with all features. This means that pixel light emission, polarization adjustment, tilt and focus changes, etc. can be achieved. During operation, not all features may be desired at once. In these cases, only those 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 the figures are merely examples; other substrate / lens shapes and liquid crystal orientations can instead be used to achieve the desired light bending and focusing. This focusing can also be in a different direction, e.g., diverging rather than converging. Similarly, tilt mechanism 55 can be positioned to tilt light to the left (rather than to the right), and polarization adjuster 20 and polarization adjuster 85 can be modified or positioned to switch the polarization of incident light from second polarization state 50 to first polarization state 15 (rather than vice versa).

[0056] Although the tunable lenses described above use liquid crystals as the material to change the refractive index of a particular layer, other materials with variable refractive indices may also be used, including lithium niobate (LiNbO3), barium titanate (BaTiO3), lithium titanate (LiTaO3), and many others.

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

[0058] Due to the fast switching rate of the first polarization adjuster 20 and the second polarization adjuster 85, the adjustable microlens 7 can steer and focus the light from the pixel 5 back and forth between two points at a rate that exceeds the flicker fusion threshold. This causes the wearer of the near-eye display 10, 11 to perceive two separate pixels when in fact there is only one. If the adjustable microlens 7 switches the light from the 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] This beam steering and focusing can be used to double or quadruple the apparent pixel count of the near-eye displays 10, 11. For example, if the near-eye displays 10, 11 have a 100-pixel by 100-pixel array, each with a corresponding adjustable microlens 7 as shown in FIG. 2, the apparent resolution of the near-eye displays can be increased to 200 pixels by 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., up and down in addition to the left and right switch provided by the first tilt mechanism 55), the light from each pixel 5 can be shifted in two directions. This allows four apparent pixels to be projected from a single pixel. Thus, the 100-pixel by 100-pixel near-eye displays 10, 11 can be perceived as a 200-pixel by 200-pixel display.

[0060] The adjustable microlens 7 can also be switched between focused and unfocused states faster than the flicker fusion threshold frequency using the second polarization adjuster 85. Turning a switchable lens 105 with a second polarization adjuster 85 "off" faster than the flicker fusion threshold frequency causes the corresponding pixel 5 and ambient light to be focused on the near-eye display 10, 11. The wearer sees the virtual image and the real image superimposed on each other. In other words, the virtual image from pixel 5 and the real image are displayed simultaneously. The wearer sees two views, one virtual and one real, alternating in rapid succession, providing the illusion of a virtual image superimposed on the real-world image. Adjusting the brightness of pixel 5 or the duty cycle of second polarization adjuster 85 changes the apparent brightness of the virtual image. (Alternatively, the same effect can be achieved by simply turning pixel 5 on and off faster than the flicker fusion threshold frequency.)

[0061] conclusion While various inventive embodiments have been described and illustrated herein, those skilled in the art will readily envision numerous other means and / or structures for performing the functions and / or obtaining the results and / or one or more advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on the specific application(s) for which the teachings of the present 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 inventive embodiments described herein. Accordingly, the foregoing embodiments are presented by way of example only, and it will be understood that, within the scope of the appended claims and their equivalents, inventive embodiments may be practiced otherwise than as specifically described and claimed. The inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods is included within the inventive scope of the present disclosure, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0062] The above embodiments can be implemented in any of numerous ways. For example, the design and construction of embodiments of the techniques disclosed herein may be implemented using hardware, software, or a combination thereof. If implemented in software, the software code may be executed on any suitable processor or collection of processors, whether provided on a single computer or distributed among multiple computers.

[0063] Also, various inventive concepts may be embodied as one or more methods, examples of which have been provided. Acts performed as part of a method may be ordered in any suitable manner. As a result, embodiments may be constructed in which acts are performed in a different order than illustrated, which may include performing some acts simultaneously, even though the exemplary embodiments show acts as sequential.

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

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

[0066] The term "and / or," as used in the specification and claims, should be understood to mean "either or both" of the conjoined elements, i.e., elements that are conjunctive in some cases and disjunctive in other cases. Multiple elements listed with "and / or" should be construed in the same manner, i.e., as "one or more" of the conjoined elements. Related or associated with the specifically identified elements. Whether or not an element is specifically identified by an "and / or" clause, other elements may optionally be present. Thus, as a non-limiting example, a reference to "A and / or B," when used in conjunction with open-ended language such as "comprising," can refer, in one embodiment, to A only (optionally including elements other than B), in another embodiment to B only (optionally including elements other than A), in yet another embodiment to both A and B (optionally including other elements), etc.

[0067] As used herein and in 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" shall be construed as inclusive, i.e., the inclusion of at least one, but also two or more, of the number or list of elements, and optionally additional items not listed. Terms clearly indicated to the contrary, such as "only one of" or "exactly one of," or, when used in the claims, "consisting of," only refer to the inclusion of exactly one element of the number or list of elements. Generally, as used herein, the term "or" shall only be construed to indicate exclusive alternatives (i.e., "one or the other, but not both") when preceded by exclusive terms, such as "either," "one of," "only one of," or "exactly one of." "Consisting essentially of," when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0068] As used in this specification and claims, the phrase "at least one" in connection with a list of one or more elements should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than those specifically identified in the list of elements referred to by the phrase "at least one," whether related or unrelated to the specifically identified elements. Thus, as a 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 at least one A (optionally including elements other than B), in one embodiment, where B is absent, and optionally including two or more As; at least one B (optionally including elements other than A), in another embodiment, where A is absent, and optionally including two or more Bs; at least one A, optionally including two or more As, and at least one B (optionally including other elements), in yet another embodiment, where two or more As are present, and optionally two or more Bs; and so forth.

[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 as open-ended, i.e., meaning including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively, as defined in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

[Claim 1] A near-eye display, an array of light-emitting transparent pixels that transmit ambient light and emit light toward the eye of a wearer of the near-eye display; an array of switchable microlenses in optical communication with the array of light-emitting transparent pixels for focusing the light to form a virtual image perceived by a wearer of the near-eye display.

Images