Patent Description:
Head-mounted display devices (also called herein head-mounted displays) are gaining popularity as means for providing visual information to a user. For example, some head-mounted display devices are used for virtual reality and augmented reality operations.

When using head-mounted display devices for AR applications, it may be desirable for the display device to seamlessly transmit ambient light to a user's eyes while projecting one or more images to the user's eyes. <NPL> discloses a virtual reality display with eye vergence and accommodation cue using stacked scattering polarizers.

Accordingly, there is a need for a head-mounted display device that has adjustable optical power and can transmit both ambient light and project image light to a user's eyes. Additionally, it may be desirable for display devices to have adjustable optical power to decrease eye fatigue and improve user comfort and satisfaction with such devices.

Thus, the above deficiencies and other problems associated with conventional head-mounted display devices are reduced or eliminated by the disclosed display devices of the invention.

In accordance with an aspect of the invention, there is provided a display device that includes an image source and a display. The image source is configured to project image light. The display includes a first optical diffuser and a second optical diffuser. The display is configured to receive the image light, diffuse the image light at the first diffuser when the image light has a first polarization, and diffuse the image light at the second diffuser when the image light has a second polarization that is different from (e.g., orthogonal to) the first polarization.

The display further comprises:
a first optical retarder disposed between the first optical diffuser and the second optical diffuser, wherein:.

The display may further comprise one or more third optical diffusers disposed between the first optical diffuser and the second optical diffuser.

The display may further comprise:
one or more second optical retarders, each optical retarder of the one or more second optical retarders corresponding to a respective optical diffuser of the one or more third optical diffusers and disposed between the respective optical diffuser and the first optical diffuser, wherein
each optical retarder of the one or more second optical retarders may be configured to transmit the image light transmitted through the first optical diffuser toward the second optical diffuser, and to transmit the first diffused image light output from the second optical diffuser toward the first optical diffuser.

The display may further comprise one or more fourth optical diffusers, wherein the second optical diffuser is disposed between the first optical diffuser and the one or more fourth optical diffusers.

The display may further comprise:
one or more third optical retarders, each optical retarder of the one or more third optical retarders corresponding to a respective optical diffuser of the one or more fourth optical diffusers and disposed between the respective optical diffuser of the one or more fourth optical diffusers and the second optical diffuser.

The first optical retarder may be an active optical retarder configurable to be in any of a first state and a second state, and wherein:.

The first optical diffuser and the second optical diffuser may have a same optical axis; and
the image source may be located at an off-axis position relative to the optical axis.

The first optical diffuser is spaced apart from the second optical diffuser.

Each of the first optical diffuser and the second optical diffuser are configured to diffuse first light having the first polarization and to transmit second light having the second polarization.

The display device may further comprise:.

The display may be configured to transmit a portion of ambient light incident upon the display; and
the lens assembly may be configured to transmit the portion of ambient light with the second optical power.

Each of the first and second optical diffusers may include a polarization sensitive hologram.

A respective optical diffuser of the first optical diffuser and the second optical diffuser may include:.

The first light may include third light in a first wavelength range and fourth light in a second wavelength range; and
a respective optical diffuser of the first optical diffuser and the second optical diffuser may include:.

The first light may include fifth light in a first incident angle range and sixth light in a second incident angle range; and
a respective optical diffuser of the first optical diffuser and the second optical diffuser may include:.

In accordance with another aspect of the invention, there is provided a display device that includes an image source configured to project image light. The image light is configurable to have a first circular polarization or a second circular polarization that is different from (e.g., orthogonal to) the first polarization. The display also includes a display that has a first optical diffuser and a second optical diffuser. The display is configured to receive the image light, diffuse the image light at the first diffuser when the image light is configured to have the first polarization, and diffuse the image light at the second diffuser when the image light is configured to have the second polarization.

In accordance with a further aspect of the invention, there is provided a method of displaying images, the method including providing image light from an image source and receiving the image light at a first optical diffuser. The method also includes, when the image light received at the first optical diffuser has a first polarization, diffusing the image light at the first optical diffuser to output first diffused image light having the first polarization. The method further includes, when the image light received at the first optical diffuser has a second polarization different from the first polarization: (i) transmitting the image light through the first optical diffuser, (ii) converting the image light from the second polarization to the first polarization, (iii) diffusing the image light having the first polarization at a second optical diffuser to output second diffused image light having the first polarization, (iv) converting the second diffused image light from the first polarization to the second polarization, and (v) transmitting the second diffused image light having the second polarization through the first optical diffuser.

Each of the first optical diffuser and the second optical diffuser is configured to diffuse light having the first polarization and to transmit light having the second polarization.

In accordance with yet a further aspect of the invention, there is provided a method of displaying images, the method including projecting first image light having first circular polarization. The method also includes diffusing the first image light at a first optical diffuser to output first diffused image light, the first diffused image light having the first polarization. The method further includes projecting second image light having a second circular polarization that is different from (e.g., orthogonal to) the first polarization, transmitting the second image light through the first optical diffuser, and converting the second image light into third image light having the first polarization. The method also includes diffusing the third image light at a second optical diffuser to output second diffused image light, the second diffused image light having the first polarization, converting the second diffused image light into third diffused image light having the second polarization, and transmitting the third diffused image light through the first optical diffuser.

It will be appreciated that any features discussed as suitable for inclusion in any of the aspects described herein, will also be suitable for inclusion in any of the other aspects in any combination.

Thus, the disclosed embodiments provide a varifocal polarization selective diffusive display that has adjustable optical power and is capable of diffusing image light having a first polarization and transmitting ambient light that has a polarization different from the first polarization without diffusing the ambient light or adding significant aberration or distortion.

For a better understanding of the various described embodiments, reference should be made to the Description of Embodiments below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures.

These figures are not drawn to scale unless indicated otherwise.

The present invention provides a head-mounted display device (or display device) that projects diffuse image light having a first polarization to a user and transmits ambient light having a second polarization to the user without diffusing the ambient light. Additionally, the head-mounted display device has adjustable optical power that alleviates eye fatigue or user discomfort associated with vergence accommodation conflict. In some embodiments, the ambient light is transmitted to the viewer without significant optical aberrations or distortions, in order to allow the user of the display device to accurately perceive and interact with objects in the outside environment.

Reference will now be made to embodiments, examples of which are illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide an understanding of the various described embodiments.

It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first light projector could be termed a second light projector, and, similarly, a second light projector could be termed a first light projector, without departing from the scope of the various described embodiments. The first light projector and the second light projector are both light projectors, but they are not the same light projector.

The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms "includes," "including," "comprises," and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The term "exemplary" is used herein in the sense of "serving as an example, instance, or illustration" and not in the sense of "representing the best of its kind.

<FIG> illustrates a perspective view of display device <NUM> in accordance with some embodiments. In some embodiments, display device <NUM> is configured to be worn on a head of a user (e.g., by having the form of spectacles or eyeglasses, as shown in <FIG>, or to be included as part of a helmet that is to be worn by the user). When display device <NUM> is configured to be worn on a head of a user, display device <NUM> is called a head-mounted display. Alternatively, display device <NUM> is configured for placement in proximity of an eye or eyes of the user at a fixed location, without being head-mounted (e.g., display device <NUM> is mounted in a vehicle, such as a car or an airplane, for placement in front of an eye or eyes of the user). As shown in <FIG>, display device <NUM> includes display <NUM>. Display <NUM> is configured for presenting visual contents (e.g., augmented reality contents, virtual reality contents, mixed-reality contents, or any combination thereof) to a user.

In some embodiments, display device <NUM> includes one or more components described herein with respect to <FIG>. In some embodiments, display device <NUM> includes additional components not shown in <FIG>.

<FIG> is a block diagram of system <NUM> in accordance with some embodiments. The system <NUM> shown in <FIG> includes display device <NUM> (which corresponds to display device <NUM> shown in <FIG>), imaging device <NUM>, and input interface <NUM> that are each coupled to console <NUM>. While <FIG> shows an example of system <NUM> including display device <NUM>, imaging device <NUM>, and input interface <NUM>, in other embodiments, any number of these components may be included in system <NUM>. For example, there may be multiple display devices <NUM> each having associated input interface <NUM> and being monitored by one or more imaging devices <NUM>, with each display device <NUM>, input interface <NUM>, and imaging devices <NUM> communicating with console <NUM>. In alternative configurations, different and/or additional components may be included in system <NUM>. For example, in some embodiments, console <NUM> is connected via a network (e.g., the Internet) to system <NUM> or is self-contained as part of display device <NUM> (e.g., physically located inside display device <NUM>). In some embodiments, display device <NUM> is used to create mixed-reality by adding in a view of the real surroundings. Thus, display device <NUM> and system <NUM> described here can deliver augmented reality, virtual reality, and mixed-reality.

In some embodiments, as shown in <FIG>, display device <NUM> is a head-mounted display that presents media to a user. Examples of media presented by display device <NUM> include one or more images, video, audio, or some combination thereof. In some embodiments, audio is presented via an external device (e.g., speakers and/or headphones) that receives audio information from display device <NUM>, console <NUM>, or both, and presents audio data based on the audio information. In some embodiments, display device <NUM> immerses a user in an augmented environment.

In some embodiments, display device <NUM> also acts as an augmented reality (AR) headset. In these embodiments, display device <NUM> augments views of a physical, real-world environment with computer-generated elements (e.g., images, video, sound, etc.). Moreover, in some embodiments, display device <NUM> is able to cycle between different types of operation. Thus, display device <NUM> operate as a virtual reality (VR) device, an augmented reality (AR) device, as glasses or some combination thereof (e.g., glasses with no optical correction, glasses optically corrected for the user, sunglasses, or some combination thereof) based on instructions from application engine <NUM>.

Display device <NUM> includes electronic display <NUM>, one or more processors <NUM>, eye tracking module <NUM>, adjustment module <NUM>, one or more locators <NUM>, one or more position sensors <NUM>, one or more position cameras <NUM>, memory <NUM>, inertial measurement unit (IMU) <NUM>, one or more optical assemblies <NUM>, or a subset or superset thereof (e.g., display device <NUM> with electronic display <NUM>, optical assembly <NUM>, without any other listed components). Some embodiments of display device <NUM> have different modules than those described here. Similarly, the functions can be distributed among the modules in a different manner than is described here.

One or more processors <NUM> (e.g., processing units or cores) execute instructions stored in memory <NUM>. Memory <NUM> includes high-speed random access memory, such as DRAM, SRAM, DDR RAM or other random access solid state memory devices; and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. Memory <NUM>, or alternately the non-volatile memory device(s) within memory <NUM>, includes a non-transitory computer readable storage medium. In some embodiments, memory <NUM> or the computer readable storage medium of memory <NUM> stores programs, modules and data structures, and/or instructions for displaying one or more images on electronic display <NUM>.

Electronic display <NUM> displays images to the user in accordance with data received from console <NUM> and/or processor(s) <NUM>. In various embodiments, electronic display <NUM> may comprise a single adjustable display element or multiple adjustable display elements (e.g., a display for each eye of a user). In some embodiments, electronic display <NUM> is configured to project images to the user through one or more optical assemblies <NUM>.

In some embodiments, the display element includes one or more light emission devices and a corresponding array of spatial light modulators. A spatial light modulator is an array of electro-optic pixels, opto-electronic pixels, some other array of devices that dynamically adjust the amount of light transmitted by each device, or some combination thereof. These pixels are placed behind one or more lenses. In some embodiments, the spatial light modulator is an array of liquid crystal based pixels in an LCD (a Liquid Crystal Display). Examples of the light emission devices include: an organic light emitting diode, an active-matrix organic light-emitting diode, a light emitting diode, some type of device capable of being placed in a flexible display, or some combination thereof. The light emission devices include devices that are capable of generating visible light (e.g., red, green, blue, etc.) used for image generation. The spatial light modulator is configured to selectively attenuate individual light emission devices, groups of light emission devices, or some combination thereof. Alternatively, when the light emission devices are configured to selectively attenuate individual emission devices and/or groups of light emission devices, the display element includes an array of such light emission devices without a separate emission intensity array.

One or more optical components in the one or more optical assemblies <NUM> direct light from the arrays of light emission devices (optionally through the emission intensity arrays) to locations within each eyebox. An eyebox (e.g., eyebox <NUM>, shown in <FIG>) is a region that is occupied by an eye of a user of display device <NUM> (e.g., a user wearing display device <NUM>) who is viewing images from display device <NUM>. In some embodiments, the eyebox is represented as a <NUM> x <NUM> square. In some embodiments, the one or more optical components include one or more coatings, such as anti-reflective coatings.

In some embodiments, the display element includes an infrared (IR) detector array that detects IR light that is retro-reflected from the retinas of a viewing user, from the surface of the corneas, lenses of the eyes, or some combination thereof. The IR detector array includes an IR sensor or a plurality of IR sensors that each correspond to a different position of a pupil of the viewing user's eye. In alternate embodiments, other eye tracking systems may also be employed.

Eye tracking module <NUM> determines locations of each pupil of a user's eyes. In some embodiments, eye tracking module <NUM> instructs electronic display <NUM> to illuminate the eyebox with IR light (e.g., via IR emission devices in the display element).

A portion of the emitted IR light will pass through the viewing user's pupil and be retro-reflected from the retina toward the IR detector array, which is used for determining the location of the pupil. Alternatively, the reflection off of the surfaces of the eye is used to also determine location of the pupil. The IR detector array scans for retro-reflection and identifies which IR emission devices are active when retro-reflection is detected. Eye tracking module <NUM> may use a tracking lookup table and the identified IR emission devices to determine the pupil locations for each eye. The tracking lookup table maps received signals on the IR detector array to locations (corresponding to pupil locations) in each eyebox. In some embodiments, the tracking lookup table is generated via a calibration procedure (e.g., user looks at various known reference points in an image and eye tracking module <NUM> maps the locations of the user's pupil while looking at the reference points to corresponding signals received on the IR tracking array). As mentioned above, in some embodiments, system <NUM> may use other eye tracking systems than the embedded IR one described herein.

Adjustment module <NUM> generates an image frame based on the determined locations of the pupils. In some embodiments, this sends a discrete image to the display that will tile sub-images together thus a coherent stitched image will appear on the back of the retina. Adjustment module <NUM> adjusts an output (i.e. the generated image frame) of electronic display <NUM> based on the detected locations of the pupils. Adjustment module <NUM> instructs portions of electronic display <NUM> to pass image light to the determined locations of the pupils. In some embodiments, adjustment module <NUM> also instructs the electronic display to not pass image light to positions other than the determined locations of the pupils. Adjustment module <NUM> may, for example, block and/or stop light emission devices whose image light falls outside of the determined pupil locations, allow other light emission devices to emit image light that falls within the determined pupil locations, translate and/or rotate one or more display elements, dynamically adjust curvature and/or refractive power of one or more active lenses in the lens (e.g., microlens) arrays, or some combination thereof.

Optional locators <NUM> are objects located in specific positions on display device <NUM> relative to one another and relative to a specific reference point on display device <NUM>. A locator <NUM> may be a light emitting diode (LED), a corner cube reflector, a reflective marker, a type of light source that contrasts with an environment in which display device <NUM> operates, or some combination thereof. In embodiments where locators <NUM> are active (i.e., an LED or other type of light emitting device), locators <NUM> may emit light in the visible band (e.g., about <NUM> to <NUM>), in the infrared band (e.g., about <NUM> to <NUM>), in the ultraviolet band (about <NUM> to <NUM>), some other portion of the electromagnetic spectrum, or some combination thereof.

In some embodiments, locators <NUM> are located beneath an outer surface of display device <NUM>, which is transparent to the wavelengths of light emitted or reflected by locators <NUM> or is thin enough to not substantially attenuate the light emitted or reflected by locators <NUM>. Additionally, in some embodiments, the outer surface or other portions of display device <NUM> are opaque in the visible band of wavelengths of light. Thus, locators <NUM> may emit light in the IR band under an outer surface that is transparent in the IR band but opaque in the visible band.

IMU <NUM> is an electronic device that generates calibration data based on measurement signals received from one or more position sensors <NUM>. Position sensor <NUM> generates one or more measurement signals in response to motion of display device <NUM>. Examples of position sensors <NUM> include: one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor that detects motion, a type of sensor used for error correction of IMU <NUM>, or some combination thereof. Position sensors <NUM> may be located external to IMU <NUM>, internal to IMU <NUM>, or some combination thereof.

Based on the one or more measurement signals from one or more position sensors <NUM>, IMU <NUM> generates first calibration data indicating an estimated position of display device <NUM> relative to an initial position of display device <NUM>. For example, position sensors <NUM> include multiple accelerometers to measure translational motion (forward/back, up/down, left/right) and multiple gyroscopes to measure rotational motion (e.g., pitch, yaw, roll). In some embodiments, IMU <NUM> rapidly samples the measurement signals and calculates the estimated position of display device <NUM> from the sampled data. For example, IMU <NUM> integrates the measurement signals received from the accelerometers over time to estimate a velocity vector and integrates the velocity vector over time to determine an estimated position of a reference point on display device <NUM>. Alternatively, IMU <NUM> provides the sampled measurement signals to console <NUM>, which determines the first calibration data. The reference point is a point that may be used to describe the position of display device <NUM>. While the reference point may generally be defined as a point in space; however, in practice the reference point is defined as a point within display device <NUM> (e.g., a center of IMU <NUM>).

In some embodiments, IMU <NUM> receives one or more calibration parameters from console <NUM>. As further discussed below, the one or more calibration parameters are used to maintain tracking of display device <NUM>. Based on a received calibration parameter, IMU <NUM> may adjust one or more IMU parameters (e.g., sample rate). In some embodiments, certain calibration parameters cause IMU <NUM> to update an initial position of the reference point so it corresponds to a next calibrated position of the reference point. Updating the initial position of the reference point as the next calibrated position of the reference point helps reduce accumulated error associated with the determined estimated position. The accumulated error, also referred to as drift error, causes the estimated position of the reference point to "drift" away from the actual position of the reference point over time.

Imaging device <NUM> generates calibration data in accordance with calibration parameters received from console <NUM>. Calibration data includes one or more images showing observed positions of locators <NUM> that are detectable by imaging device <NUM>. In some embodiments, imaging device <NUM> includes one or more still cameras, one or more video cameras, any other device capable of capturing images including one or more locators <NUM>, or some combination thereof. Additionally, imaging device <NUM> may include one or more filters (e.g., used to increase signal to noise ratio). Imaging device <NUM> is configured to optionally detect light emitted or reflected from locators <NUM> in a field of view of imaging device <NUM>. In embodiments where locators <NUM> include passive elements (e.g., a retroreflector), imaging device <NUM> may include a light source that illuminates some or all of locators <NUM>, which retroreflect the light toward the light source in imaging device <NUM>. Second calibration data is communicated from imaging device <NUM> to console <NUM>, and imaging device <NUM> receives one or more calibration parameters from console <NUM> to adjust one or more imaging parameters (e.g., focal length, focus, frame rate, ISO, sensor temperature, shutter speed, aperture, etc.).

In some embodiments, display device <NUM> includes one or more optical assemblies <NUM>, which can include a single optical assembly <NUM> or multiple optical assemblies <NUM> (e.g., an optical assembly <NUM> for each eye of a user). In some embodiments, the one or more optical assemblies <NUM> receive image light for the computer generated images from the electronic display <NUM> and direct the image light toward an eye or eyes of a user. The computer-generated images include still images, animated images, and/or a combination thereof. The computer-generated images include objects that appear to be two-dimensional and/or three-dimensional objects.

In some embodiments, electronic display <NUM> projects computer-generated images to one or more reflective elements (not shown), and the one or more optical assemblies <NUM> receive the image light from the one or more reflective elements and direct the image light to the eye(s) of the user. In some embodiments, the one or more reflective elements are partially transparent (e.g., the one or more reflective elements have a transmittance of at least <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%), which allows transmission of ambient light. In such embodiments, computer-generated images projected by electronic display <NUM> are superimposed with the transmitted ambient light (e.g., transmitted ambient image) to provide augmented reality images.

Input interface <NUM> is a device that allows a user to send action requests to console <NUM>. An action request is a request to perform a particular action. For example, an action request may be to start or end an application or to perform a particular action within the application. Input interface <NUM> may include one or more input devices. Example input devices include: a keyboard, a mouse, a game controller, data from brain signals, data from other parts of the human body, or any other suitable device for receiving action requests and communicating the received action requests to console <NUM>. An action request received by input interface <NUM> is communicated to console <NUM>, which performs an action corresponding to the action request. In some embodiments, input interface <NUM> may provide haptic feedback to the user in accordance with instructions received from console <NUM>. For example, haptic feedback is provided when an action request is received, or console <NUM> communicates instructions to input interface <NUM> causing input interface <NUM> to generate haptic feedback when console <NUM> performs an action.

Console <NUM> provides media to display device <NUM> for presentation to the user in accordance with information received from one or more of: imaging device <NUM>, display device <NUM>, and input interface <NUM>. In the example shown in <FIG>, console <NUM> includes application store <NUM>, tracking module <NUM>, and application engine <NUM>. Some embodiments of console <NUM> have different modules than those described in conjunction with <FIG>. Similarly, the functions further described herein may be distributed among components of console <NUM> in a different manner than is described here.

When application store <NUM> is included in console <NUM>, application store <NUM> stores one or more applications for execution by console <NUM>. An application is a group of instructions, that when executed by a processor <NUM>, is used for generating content for presentation to the user. Content generated by the processor <NUM> based on an application may be in response to inputs received from the user via movement of display device <NUM> or input interface <NUM>. Examples of applications include: gaming applications, conferencing applications, video playback application, or other suitable applications.

When tracking module <NUM> is included in console <NUM>, tracking module <NUM> calibrates system <NUM> using one or more calibration parameters and may adjust one or more calibration parameters to reduce error in determination of the position of display device <NUM>. For example, tracking module <NUM> adjusts the focus of imaging device <NUM> to obtain a more accurate position for observed locators <NUM> on display device <NUM>. Moreover, calibration performed by tracking module <NUM> also accounts for information received from IMU <NUM>. Additionally, if tracking of display device <NUM> is lost (e.g., imaging device <NUM> loses line of sight of at least a threshold number of locators <NUM>), tracking module <NUM> re-calibrates some or all of system <NUM>.

In some embodiments, tracking module <NUM> tracks movements of display device <NUM> using second calibration data from imaging device <NUM>. For example, tracking module <NUM> determines positions of a reference point of display device <NUM> using observed locators <NUM> from the second calibration data and a model of display device <NUM>. In some embodiments, tracking module <NUM> also determines positions of a reference point of display device <NUM> using position information from the first calibration data. Additionally, in some embodiments, tracking module <NUM> may use portions of the first calibration data, the second calibration data, or some combination thereof, to predict a future location of display device <NUM>. Tracking module <NUM> provides the estimated or predicted future position of display device <NUM> to application engine <NUM>.

Application engine <NUM> executes applications within system <NUM> and receives position information, acceleration information, velocity information, predicted future positions, or some combination thereof of display device <NUM> from tracking module <NUM>. Based on the received information, application engine <NUM> determines content to provide to display device <NUM> for presentation to the user. For example, if the received information indicates that the user has looked to the left, application engine <NUM> generates content for display device <NUM> that mirrors the user's movement in an augmented environment. Additionally, application engine <NUM> performs an action within an application executing on console <NUM> in response to an action request received from input interface <NUM> and provides feedback to the user that the action was performed. The provided feedback may be visual or audible feedback via display device <NUM> or haptic feedback via input interface <NUM>.

<FIG> is an isometric view of a display device <NUM>, which corresponds to part of or all of display device <NUM> (see <FIG>) in accordance with some embodiments. In some embodiments, display device <NUM> includes an emission array <NUM> (e.g., a light emission device array or reflective element), and an optical assembly (e.g., optical assembly <NUM>) having one or more optical components <NUM> (e.g., lenses). In some embodiments, display device <NUM> also includes an IR detector array.

In some embodiments, light emission device array <NUM> emits image light and optional IR light toward the optical components <NUM>. Light emission device array <NUM> may be, e.g., an array of LEDs, an array of microLEDs, an array of OLEDs, or some combination thereof. Light emission device array <NUM> includes light emission devices <NUM> that emit light in the visible light (and optionally includes devices that emit light in the IR).

In some embodiments, display device <NUM> includes an emission intensity array configured to selectively attenuate light emitted from light emission array <NUM>. In some embodiments, the emission intensity array is composed of a plurality of liquid crystal cells or pixels, groups of light emission devices <NUM>, or some combination thereof. Each of the liquid crystal cells is, or in some embodiments, groups of liquid crystal cells are, addressable to have specific levels of attenuation. For example, at a given time, some of the liquid crystal cells may be set to no attenuation, while other liquid crystal cells may be set to maximum attenuation. In this manner, the emission intensity array is able to control what portion of the image light emitted from light emission device array <NUM> is passed to the one or more optical components <NUM>. In some embodiments, display device <NUM> uses an emission intensity array to facilitate providing image light to a location of pupil <NUM> of eye <NUM> of a user, and minimize the amount of image light provided to other areas in the eyebox <NUM>.

An optional IR detector array detects IR light that has been retro-reflected from the retina of eye <NUM>, a cornea of eye <NUM>, a crystalline lens of eye <NUM>, or some combination thereof. The IR detector array includes either a single IR sensor or a plurality of IR sensitive detectors (e.g., photodiodes). In some embodiments, the IR detector array is separate from light emission device array <NUM>. In some embodiments, the IR detector array is integrated into light emission device array <NUM>.

In some embodiments, light emission device array <NUM> and an emission intensity array make up a display element. Alternatively, the display element includes light emission device array <NUM> (e.g., when light emission device array <NUM> includes individually adjustable pixels) without the emission intensity array. In some embodiments, the display element additionally includes the IR array. In some embodiments, in response to a determined location of pupil <NUM>, the display element adjusts the emitted image light such that the light output by the display element is refracted by one or more optical components <NUM> toward the determined location of pupil <NUM>, and not toward another presumed location.

In some embodiments, display device <NUM> includes one or more broadband sources (e.g., one or more white LEDs) coupled with a plurality of color filters, in addition to, or instead of, light emission device array <NUM>.

One or more optical components <NUM> receive the image light (or modified image light, e.g., attenuated light) from emission array <NUM>, and direct the image light to a detected or presumed location of the pupil <NUM> of an eye <NUM> of a user. In some embodiments, the one or more optical components <NUM> include one or more optical assemblies <NUM>.

<FIG> are schematic diagrams illustrating a display device in accordance with some embodiments.

<FIG> is a schematic diagram illustrating a varifocal polarization sensitive diffusive display device (referred to hereafter as "display device") <NUM>, according to certain embodiments. As shown, display device <NUM> includes an image source <NUM> configured to provide (e.g., project, output, generate, emit) image light corresponding to images to be displayed, and a display <NUM> configured to display the images. In some embodiments, the image light provided by the image source <NUM> may have any of: a first polarization, a second polarization different from (e.g.,orthogonal to) the first polarization, or a combination of more than one polarization. For example, in some embodiments, the image light is configurable to be first image light <NUM>-<NUM> having first polarization or second image light <NUM>-<NUM> having second polarization. In some embodiments, the first polarization is right-handed polarization or RCP, and the second polarization is left-handed polarization or LCP, or vice versa. In some embodiments, display <NUM> includes a plurality of optical diffusers (e.g., a first optical diffuser <NUM> and a second optical diffuser <NUM>). Display <NUM> is configured to: (<NUM>) receive first image light <NUM>-<NUM> and diffuse the first image light <NUM>-<NUM> at first optical diffuser <NUM> (as shown in <FIG>), or (<FIG>) receive second image light <NUM>-<NUM> and diffuse the second image light <NUM>-<NUM> at second optical diffuser <NUM> (as shown in <FIG>).

Each of the first optical diffuser <NUM> and the second optical diffuser <NUM> is configured to diffuse light having the first polarization and to transmit light having the second polarization. For example, as shown in inset A of <FIG>, first optical diffuser <NUM> is configured to diffuse first image light <NUM>-<NUM> having the first polarization as first diffused image light <NUM>.

As shown in <FIG>, ambient light <NUM>, which may be unpolarized, may be incident upon the second optical diffuser <NUM>. A first portion <NUM>-<NUM> of the ambient light <NUM> having the first polarization (e.g., RCP) is diffused at the second optical diffuser <NUM>, and a second portion <NUM>-<NUM> of the ambient light <NUM> having the second polarization (e.g., LCP) is transmitted through both the second optical diffuser <NUM> and the first optical diffuser <NUM>.

In some embodiments, as shown in <FIG>, first optical diffuser <NUM> includes a first surface <NUM>-A, and is configured to receive the first image light <NUM>-<NUM> at the first surface <NUM>-A and to output the first diffused image light <NUM> from the first surface <NUM>-A (e.g., reflectively diffuse the first image light <NUM>-<NUM> at the first surface <NUM>-A). Additional details regarding the first optical diffuser <NUM> and the second optical diffuser <NUM> are provided below with respect to <FIG> and Figures 6A - 6D.

Display device <NUM> also includes a first optical retarder <NUM> that is disposed between the first optical diffuser <NUM> and the second optical diffuser <NUM>. As shown in <FIG>, when the display <NUM> receives second image light <NUM>-<NUM> having the second polarization, the first optical diffuser <NUM> is configured to transmit the second image light <NUM>-<NUM>. The first optical retarder <NUM> is configured to receive the second image light <NUM>-<NUM> that has been transmitted through the first optical diffuser <NUM>, and to convert the polarization of the second image light <NUM>-<NUM> such that after transmitting through the first optical retarder <NUM>, second image light <NUM>-<NUM> has the first polarization and is diffused by the second optical diffuser <NUM> as second diffused image light <NUM> also having the first polarization. The first optical retarder <NUM> is further configurable to receive the second diffused image light <NUM>, and to convert the polarization of the second diffused image light <NUM> from the first polarization to the second polarization such that the second diffused image light <NUM> is transmitted by the first optical diffuser422.

In the ideal case, light is transmitted through an optical diffuser without diffusion. For instance, in the ideal case, the second image light <NUM>-<NUM> having the second polarization is transmitted through the first optical diffuser <NUM> without any diffusion. In some cases, a small amount of the transmitted light may be diffused. For example, a small, non-zero amount of the second image light <NUM>-<NUM> may be diffused by the first optical diffuser <NUM>. However, a portion of the diffuse light compared to the incident light for a configuration in which an optical diffuser causes transmission of (most of) the incident light is less than a portion of the diffuse light compared to the incident light for a configuration in which an optical diffuser causes diffusion of the incident light. For example, an optical diffuser causes diffusion of less than <NUM>% (e.g., less than <NUM>%) of the incident light while the optical diffuser allows transmission of the incident light and the optical diffuser causes diffusion of greater than <NUM>% (e.g., greater than <NUM>%) of the incident light while the optical diffuser allows diffusion of the incident light).

Thus, in some embodiments, the first optical diffuser <NUM> is configured to output first diffused image light <NUM> by diffusing the first image light <NUM>-<NUM> (as shown in <FIG>), and the second optical diffuser <NUM> is configured to output second diffused image light <NUM> by diffusing the second image light <NUM>-<NUM> having the second polarization (as shown in <FIG>). In some embodiments, the first diffused image light <NUM> has the first polarization and the second diffused image light <NUM> has the second polarization.

In some embodiments, as shown in <FIG>, display <NUM> may include more than two optical diffusers (e.g., first optical diffuser <NUM>, and optical diffusers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n, n ><NUM>).

In some embodiments, a distance between any two adjacent optical diffusers in display <NUM> is larger than <NUM> micrometers, <NUM> micrometers, <NUM> micrometers, <NUM> millimeter, <NUM> millimeters, <NUM> millimeters, <NUM> millimeters, <NUM> millimeters, or <NUM> millimeters. For example, as shown in <FIG>, first optical diffuser <NUM> is spaced apart from optical diffuser <NUM>-<NUM> by distance D1 that is larger than <NUM> micrometers, <NUM> micrometers, <NUM> micrometers, <NUM> millimeter, <NUM> millimeters, <NUM> millimeters, <NUM> millimeters, <NUM> millimeters, or <NUM> millimeters and optical diffuser <NUM>-<NUM> is spaced apart from optical diffuser <NUM>-<NUM> by distance D2 that is larger than <NUM> micrometers, <NUM> micrometers, <NUM> micrometers, <NUM> millimeter, <NUM> millimeters, <NUM> millimeters, <NUM> millimeters, <NUM> millimeters, or <NUM> millimeters. Thus, first optical diffuser <NUM> is spaced apart from any of optical diffusers <NUM> (e.g., optical diffusers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n) by a distance that is larger than <NUM> micrometers, <NUM> micrometers, <NUM> micrometers, <NUM> millimeter, <NUM> millimeters, <NUM> millimeters, <NUM> millimeters, <NUM> millimeters, or <NUM> millimeters. In some embodiments, as shown in <FIG>, distance D2 is different from distance D1. In some embodiments, distances D1 and D2 are substantially the same (e.g., within +/- <NUM> millimeters).

In some embodiments, display <NUM> includes one or more third optical diffusers disposed between the first optical diffuser <NUM> and the second optical diffuser <NUM>.

In some embodiments, display <NUM> also includes optical retarders <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n corresponding to optical diffusers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n, respectively. Each of the optical retarders (e.g., optical retarder <NUM>-<NUM>) is disposed between the respective optical diffuser (e.g., optical diffuser <NUM>-<NUM>) and first optical diffuser <NUM>, and between the respective optical diffuser (e.g., optical diffuser <NUM>-<NUM>) and an adjacent optical diffuser (e.g., optical diffuser <NUM>-<NUM>). In some embodiments, any (e.g., some or all) of optical retarders <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n can be a switchable optical retarder (e.g., an active optical retarder) that is configurable to be in any of a first state and a second state (e.g., an "off' state and an "on" state), and display device <NUM> further includes controllers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n coupled to optical retarders <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n, respectively, and configured to control the respective states of optical retarders <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n. Operation of switchable optical retarders is described below with respect to <FIG>.

In some embodiments, by configuring the states of optical retarders <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n using controllers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n, any of optical diffusers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n (e.g., optical retarder <NUM>-i, i = <NUM>, <NUM>,. , n) can be selected to act as second optical diffuser <NUM> configured to output second diffused image light <NUM> by diffusing second image light <NUM>-<NUM> (as shown in <FIG>) and the corresponding optical retarder (e.g., optical retarder <NUM>-i) would function as first optical retarder <NUM>. For example, as shown in <FIG>, to have optical diffuser <NUM>-n act as second optical diffuser <NUM> and optical retarder <NUM>-n function as first optical retarder <NUM>, the states of optical retarders <NUM>-<NUM> through <NUM>-(n-<NUM>) are set to be "on" and the state of optical retarder <NUM>-n is set to be "off. " In this way, optical retarders <NUM>-<NUM> through <NUM>-(n-<NUM>) are configured to transmit the second image light <NUM>-<NUM> propagating toward optical diffuser <NUM>-n without changing its polarization, and to transmit the second diffused image light <NUM> propagating toward the first optical diffuser <NUM> without changing its polarization. Optical retarder <NUM>-n is configured to transmit the second image light <NUM>-<NUM> as third image light having the first polarization so that the third image light is diffused at optical diffuser <NUM>-n, and to transmit the diffused third image light output from the optical diffuser <NUM>-n as the second diffused image light <NUM> having the second polarization.

In another example, as shown in <FIG>, to have optical diffuser <NUM>-<NUM> act as second optical diffuser <NUM> and optical retarder <NUM>-<NUM> function as first optical retarder <NUM>, the states of optical retarders <NUM>-<NUM> are set to be "on" and the state of optical retarder <NUM>-<NUM> is set to be "off. " In this way, optical retarder <NUM>-<NUM> is configured to transmit the second image light <NUM>-<NUM> propagating toward optical diffuser <NUM>-<NUM> without changing its polarization, and to transmit the second diffused image light <NUM> propagating toward the first optical diffuser <NUM> without changing its polarization.

Thus, in some embodiments, the second optical diffuser <NUM> can be any of optical diffusers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n. As such, there can be one or more third optical diffusers between first optical diffuser <NUM> and second optical diffuser <NUM>, and/or, there can be one or more fourth optical diffusers that are not between first optical diffuser <NUM> and second optical diffuser.

In some embodiments, optical retarders <NUM> may include switchable optical retarders as well as optical retarders that are not switchable (e.g., not active optical elements). For example, as shown in <FIG>, optical retarders <NUM>-<NUM> through <NUM>-(n-<NUM>) are switchable optical retarders and optical retarders <NUM>-n is not required to be a switchable optical retarder.

As shown in <FIG>, when a switchable optical retarder (e.g., an optical retarder <NUM>) is configured to be in the "off' state, the switchable optical retarder is configured to convert the polarization of incident light from an incident polarization to an orthogonal polarization. For example, as shown in <FIG>, switchable optical retarder <NUM>-n, in the "off' state, is configured to convert the polarization of second image light <NUM>-<NUM>, transmitted through the first optical diffuser <NUM>, from the second polarization to the first polarization.

As shown in <FIG>, when a switchable optical retarder is configured to be in the "on" state, the switchable optical retarder is configured to transmit incident light transmitted without changing its polarization. For example, as shown in <FIG>, optical retarder <NUM>-<NUM>, in the "on" state, is configured to transmit second image light <NUM>-<NUM>, transmitted through the first optical diffuser <NUM>, without changing its polarization.

Referring to <FIG>, in some embodiments, the first optical diffuser <NUM> and the second optical diffuser <NUM> of display device <NUM> have a same optical axis <NUM>, and the image source <NUM> is disposed at an off-axis position relative to the optical axis <NUM>. Additional details regarding the image source <NUM> are provided below with respect to <FIG>.

Referring to <FIG>, in some embodiments, display device <NUM> includes a lens assembly <NUM> and a switchable optical retarder <NUM> disposed between the display <NUM> and the lens assembly <NUM>. Switchable optical retarder <NUM> is electrically coupled to controller <NUM>, and operation of the switchable optical retarder <NUM> is described above with respect to <FIG>. In some embodiments, as shown in <FIG>, when the image source <NUM> is configured to output the first image light <NUM>-<NUM>, the switchable optical retarder <NUM> is configured to be in a first state (e.g., in this example, an "off' state). Switchable optical retarder <NUM>, in the first state, is configured to receive the first diffused image light <NUM> and to output third diffused image light <NUM>-<NUM> having third polarization. In some embodiments, as shown in <FIG>, when the image source <NUM> is configured to output second image light <NUM>-<NUM>, the switchable optical retarder <NUM> is configured to be in a second state. Switchable optical retarder <NUM>, in the second state (e.g., in this example, an "on" state), is configured to receive the second diffused image light <NUM> and to output fourth diffused image light <NUM>-<NUM> having the third polarization. Thus, regardless of whether the image source <NUM> is configured to output the first image light <NUM>-<NUM> or the second image light <NUM>-<NUM>, switchable optical retarder <NUM>, in the first state or the second state, is configured to output diffused image light having the third polarization. Although <FIG> show the third polarization being the same as the second polarization, the third polarization may be the same as either the first polarization or the second polarization (e.g., the third polarization can be either LCP or RCP).

In some embodiments, as shown in <FIG>, the switchable optical retarder <NUM> is also configurable to receive the second portion <NUM>-<NUM> of ambient light <NUM> that has been transmitted through display <NUM>, and to output second ambient light <NUM> having a fourth polarization that is different from (e.g., orthogonal to) the third polarization regardless of whether the switchable optical retarder <NUM> is in the first state or the second state. For example, as shown in <FIG>, when the diffused image light <NUM>-<NUM> and <NUM>-<NUM> output from the switchable optical retarder <NUM> is LCP light, the second ambient light <NUM> output from the switchable optical retarder <NUM> is RCP light. Alternatively, when the diffused image light <NUM>-<NUM> and <NUM>-<NUM> output from the switchable optical retarder <NUM> is RCP light, the second ambient light <NUM> output from the switchable optical retarder <NUM> is LCP light.

In some embodiments, as shown in <FIG>, the lens assembly <NUM> is a polarization selective lens assembly. The lens assembly <NUM> is configured to, based on the polarization of light incident upon the lens assembly <NUM>, transmit the incident light at either a first optical power or a second optical power. For example, as shown in <FIG>, the lens assembly <NUM> is configured to receive the diffused image light <NUM>-<NUM> and <NUM>-<NUM> output from the switchable optical retarder <NUM> and having the third polarization, and to direct (e.g., focus, substantially collimate) the diffused image light <NUM>-<NUM> and <NUM>-<NUM> at a first optical power. Lens assembly <NUM> is also configured to transmit the second ambient light <NUM>, output from the switchable optical retarder <NUM> and having the fourth polarization, at a second optical power that is different from (e.g., smaller than) the first optical power. In some embodiments, the second optical power is zero. In some embodiments, the lens assembly <NUM> is configured to transmit second ambient light <NUM> without adding significant optical aberrations. In some embodiments, the lens assembly <NUM> may include a pancake lens or a metasurface lens.

<FIG> are schematic diagrams illustrating an image source <NUM> in a display device in accordance with some embodiments.

In some embodiments, the image source <NUM> includes a projector <NUM> configured to output image light <NUM>' having an initial polarization (e.g., LCP or RCP), a polarization sensitive optical element <NUM>, and a switchable optical retarder <NUM> disposed between the projector <NUM> and the polarization sensitive optical element <NUM>. Switchable optical retarder <NUM> is electrically coupled to controller <NUM> and operation of the switchable optical retarder <NUM> is described above with respect to <FIG>. In some embodiments, the projector <NUM> is configured to generate linearly polarized light and includes a circular polarizer, such as a quarter wave retarder, that is configured to convert the linearly polarized light into image light <NUM>' having an initial polarization that is a circular polarization (e.g., LCP or RCP).

In some embodiments, switchable optical retarder <NUM> is configured to receive image light <NUM>' having the initial polarization and to output image light <NUM>", having either the first polarization or the second polarization, toward polarization sensitive optical element <NUM>. Switchable optical retarder <NUM> is configurable to be in one of a first state and a second state (e.g., an "on" state and an "off' state, or vice versa) and the polarization of the image light <NUM>" depends on the state of the switchable optical retarder <NUM>. Polarization sensitive optical element <NUM> is configured to receive the image light <NUM>" output from the switchable optical retarder <NUM>, regardless of the polarization of the image light <NUM>", and to project (e.g., steer, direct, diffract) the image light <NUM>" as either the first image light <NUM>-<NUM> or the second image light <NUM>-<NUM>, depending on the polarization of the image light <NUM>". When the image light <NUM>" has the second polarization, the polarization sensitive optical element <NUM> is configured to project the image light <NUM>" as the first image light <NUM>-<NUM> propagating a first direction (e.g., for diffusion by the first optical diffuser <NUM> shown in <FIG>). When the image light490" has the first polarization, the polarization sensitive optical element <NUM> is configured to project the image light <NUM>" as the second image light490-<NUM> propagating in a second direction (e.g., for diffusion by the second optical diffuser <NUM> shown in <FIG>). In some embodiments, when the first optical diffuser <NUM> is spaced apart from the second optical diffuser <NUM>, the first direction is distinct from the second direction so that the first image light <NUM>-<NUM> projected onto the first optical diffuser <NUM> is horizontally aligned with the second image light <NUM>-<NUM> projected onto the second optical diffuser <NUM>. In some embodiments, the polarization sensitive optical element <NUM> is a Pancharatnam-Berry phase optical element (e.g., a geometric phase optical element, a geometric phase grating).

For example, as shown in <FIG>, projector <NUM> outputs the image light <NUM>' having the second polarization (e.g., LCP). When the switchable optical retarder <NUM> is in the first state (e.g., "on" state), the image light <NUM>' is transmitted as image light <NUM>" without a change in polarization. Polarization sensitive optical element <NUM> receives the image light <NUM>" having the second polarization and projects (e.g., steers, directs, diffracts) the image light <NUM>" as the first image light <NUM>-<NUM> propagating in the first direction (e.g., having a first angle A1 relative to a surface normal of polarization sensitive optical element <NUM>). Thus, when the switchable optical retarder <NUM> is in the first state, the first image light <NUM>-<NUM> having the first polarization (e.g., RCP) is output from polarization sensitive optical element <NUM>.

In another example, as shown in <FIG>, the projector <NUM> outputs the image light <NUM>' having the second polarization (e.g., LCP). When switchable optical retarder <NUM> is in the second state (e.g., "off' state), the image light <NUM>' is converted to image light <NUM>" having the first polarization. Polarization sensitive optical element <NUM> receives the image light <NUM>" having the first polarization and projects (e.g., steers, directs, diffracts) the image light <NUM>" as the second image light <NUM>-<NUM> propagating in the second direction (e.g., having a second angle A2 relative to a surface normal of polarization sensitive optical element <NUM>). Thus, when the switchable optical retarder <NUM> is in the second state, the second image light <NUM>-<NUM> having the second polarization (e.g., LCP) is output from the polarization sensitive optical element <NUM>.

<FIG> illustrate operation of a display device <NUM>, corresponding to display device <NUM>. As shown, display device <NUM> has a display assembly that includes three optical diffusers: a first optical diffuser <NUM>-<NUM>, a second optical diffuser <NUM>-<NUM>, and a third optical diffuser <NUM>-<NUM>. The display assembly also includes two optical retarders: a first optical retarder <NUM>-<NUM> disposed between the first optical diffuser <NUM>-<NUM> and the second optical diffuser <NUM>-<NUM>, and a second optical retarder <NUM>-<NUM> disposed between the second optical diffuser <NUM>-<NUM> and the third optical diffuser <NUM>-<NUM>. Details regarding the optical diffusers and optical retarders are provided above with respect to <FIG> and not repeated here for brevity. The display device <NUM> also includes an image source <NUM> that is configured to provide (e.g., output, generate, emit, project) image light toward the display assembly. The display device <NUM> is configured to selectively diffuse the image light from any of the first optical diffuser <NUM>-<NUM>, the second optical diffuser <NUM>-<NUM>, and the third optical diffuser <NUM>-<NUM>. The focal plane of the image projected toward a user's eye <NUM> can be changed by causing diffusion of the image light at the different optical diffusers of the display device <NUM>. Thus, the display device <NUM> is able to quickly switch between the three optical diffusers in order to provide a user with a multi-focal image. The switching can be a fast time-sequenced switching process so that a user perceives a single scene with objects located at different focal planes. For example, the images are time sequenced so that they are presented to the user at a high enough frame rate at which each frame is not separately discernable by the human eye <NUM> (e.g., faster than the flicker fusion threshold). In some embodiments, the frame frequency is greater than <NUM> Hertz. In some embodiments, the frame frequency is <NUM> Hertz or higher. For instance, an image may include a dog, a tree, and a house. A first portion of the image light corresponding to the dog may be diffused at the first optical diffuser <NUM>-<NUM> (as shown in <FIG>) so that the diffused image light <NUM>-<NUM> presents the user with an image of a dog at a first focal plane, a second portion of the image light corresponding to the tree may be diffused at the second optical diffuser <NUM>-<NUM> (as shown in <FIG>) so that the diffused image light <NUM>-<NUM> presents the user with an image of a tree at a second focal plane that is distinct from the first focal plane, and a third portion of the image light corresponding to the house may be diffused at the third optical diffuser <NUM>-<NUM> (as shown in <FIG>) so that the diffused image light <NUM>-<NUM> presents the user with an image of a house at a third focal plane that is distinct from the first focal plane and the second focal plane. Thus, by consecutively providing the portions of the image light corresponding to the dog, tree, and house and diffusing the respective portions of the image light at different optical diffusers, a multi-focal image or multi-focal scene can be seamlessly presented to a user.

<FIG> are cross-sectional diagrams of polarization sensitive hologram <NUM>, which corresponds to any of the first optical diffuser <NUM> and the second optical diffusers <NUM> and <NUM> in accordance with some embodiments. As shown in <FIG>, the polarization sensitive hologram <NUM> includes a first surface <NUM>-<NUM>, a second surface <NUM>-<NUM> that is opposite to the first surface <NUM>-<NUM>, and optically anisotropic molecules <NUM> disposed between the first surface <NUM>-<NUM> and the second surface <NUM>-<NUM>. In some embodiments, the polarization sensitive hologram <NUM> is configured to output light from the first surface <NUM>-<NUM> in response to receiving incident light at the first surface <NUM>-<NUM>. As shown, when the incident light (e.g., light <NUM>) has the first circular polarization (e.g., RCP), diffused light <NUM> having the first circular polarization is output from the first surface <NUM>-<NUM>. In some embodiments, the light <NUM> is substantially collimated and propagating in a first direction. In some embodiments, the polarization sensitive hologram <NUM> is configured to diffuse the light <NUM> to output diffused light <NUM> that propagates in a plurality of directions. When the incident light (e.g., light <NUM>) has the second circular polarization (e.g., LCP), the polarization sensitive hologram <NUM> is configured to transmit light <NUM> from the second surface <NUM>-<NUM>. In some embodiments, light <NUM> is transmitted without change in polarization or direction.

In some embodiments, the polarization sensitive hologram <NUM> may be incident angle selective, and/or wavelength selective.

<FIG> illustrates wavelength selectivity of the polarization sensitive hologram <NUM> in accordance with some embodiments. In some embodiments, the polarization sensitive hologram <NUM> is configured to diffuse light having the first circular polarization and a wavelength that is within a first predefined spectral range, and to transmit light having a wavelength that is outside of the first predefined spectral range regardless of the polarization of the light.

As shown, light <NUM>, having the first circular polarization and a first wavelength λ1 that is within the first predefined spectral range, is incident upon the polarization sensitive hologram <NUM>. Thus, light <NUM> is diffused at the polarization sensitive hologram <NUM> and diffused light <NUM> having the first circular polarization is output from the polarization sensitive hologram <NUM>. On the other hand, light <NUM>, which has a wavelength λ that is outside the first predefined spectral range, is transmitted through the polarization sensitive hologram <NUM> without a change in direction or polarization.

For example, as shown in <FIG>, the polarization sensitive hologram <NUM> can be incident angle selective so that the polarization sensitive hologram <NUM> interacts differently with incident light having different incident angles with respect to a direction indicated by dashed line <NUM> that is normal to first surface <NUM>-<NUM>. In some embodiments, the polarization sensitive hologram <NUM> is configured to diffuse light having the first circular polarization and incident upon polarization sensitive hologram <NUM> at an incident angle that is within a first predefined incident angle range (e.g., smaller than angle φ). In some embodiments, the polarization sensitive hologram <NUM> is configured to transmit third light that is incident upon the polarization sensitive hologram <NUM> at an incident angle that is outside of the first predefined incident angle range (e.g., equal or larger than φ), regardless of the polarization of the light.

As shown, light <NUM> having the first circular polarization can be incident upon the polarization sensitive hologram <NUM> in a direction that forms a first incident angle θ1 with respect to line <NUM>. First incident angle θ1 is within the first predefined incident angle range (e.g., θ1 < φ). Thus, light <NUM> is diffused at the polarization sensitive hologram <NUM>, and diffused light <NUM> having the first circular polarization is output from the polarization sensitive hologram <NUM> in response to light <NUM>. On the other hand, light <NUM> is incident upon the polarization sensitive hologram <NUM> at a second incident angle θ2 that is outside the first predefined incident angle range (e.g., θ2 ≥ φ). Thus, light <NUM> is transmitted through the polarization sensitive hologram <NUM> without change in direction or polarization.

<FIG> illustrates optical paths of light transmitted through the polarization sensitive hologram <NUM> in accordance with some embodiments. In some embodiments, as shown in <FIG>, the polarization sensitive hologram <NUM> includes a plurality of optical diffuser layers (e.g., first optical diffuser layer <NUM>, second optical diffuser layer <NUM>, and third optical diffuser layer <NUM>). A first optical diffuser layer <NUM> has a first surface <NUM>-<NUM>, a second surface <NUM>-<NUM>, and optically anisotropic molecules <NUM>-<NUM> disposed between the first surface <NUM>-<NUM> and the second surface502-<NUM>. A third optical diffuser layer <NUM> has a third surface <NUM>-<NUM>, a fourth surface <NUM>-<NUM>, and optically anisotropic molecules <NUM>-<NUM> disposed between the third surface <NUM>-<NUM> and the fourth surface <NUM>-<NUM>. A second optical diffuser layer <NUM>, has optically anisotropic molecules <NUM>-<NUM> disposed between the second surface <NUM>-<NUM> and the third surface <NUM>-<NUM>.

In some embodiments, the first optical diffuser layer <NUM> is configured to diffuse light having a wavelength that is within a first predefined spectral range, the second optical diffuser layer <NUM> is configured to diffuse light having a wavelength that is within a second predefined spectral range that is different from the first predefined spectral range, and the third optical diffuser layer <NUM> is configured to diffuse light having a wavelength that is within a third predefined spectral range that is different from the first predefined spectral range and from the second predefined spectral range. In some embodiments, the polarization sensitive hologram <NUM> is configured to diffuse light having a wavelength that is within a wider spectral range that encompasses the first predefined spectral range, the second predefined spectral range, and the third predefined spectral range. As shown in inset B, the optically anisotropic molecules <NUM>-<NUM> that are disposed between first surface <NUM>-<NUM> and second surface <NUM>-<NUM> are arranged such that the first optical diffuser layer <NUM> diffuses light <NUM> having the first circular polarization and a first wavelength λ1 that is within the first predefined spectral range. Thus, diffuse light <NUM> having the first wavelength λ1 is output from first optical diffuser layer <NUM> via second surface <NUM>-<NUM>. Optically anisotropic molecules <NUM>-<NUM> that are disposed between the second surface <NUM>-<NUM> and the third surface <NUM>-<NUM> are arranged such that the second optical diffuser layer <NUM> diffuses light <NUM> having the first circular polarization and a second wavelength λ2 that is within a second predefined spectral range and transmits diffuse light <NUM> without change in direction or polarization. Thus, diffuse light <NUM> having the second wavelength λ2 is output from the second optical diffuser layer <NUM> through the third surface <NUM>-<NUM>. Optically anisotropic molecules <NUM>-<NUM> that are disposed between the third surface <NUM>-<NUM> and the fourth surface <NUM>-<NUM> are arranged such that the third optical diffuser layer diffuses light <NUM> having the first circular polarization and a third wavelength λ3 that is within a third predefined spectral range and transmits diffuse light <NUM> and diffuse light <NUM> without change in direction or polarization. Thus, diffuse light <NUM> having the third wavelength λ3 is output from the fourth surface <NUM>-<NUM>, together with diffuse light <NUM> and diffuse light <NUM>. Thus, when incident light (e.g., light <NUM>, <NUM>, <NUM>) having the first polarization and wavelength within the wider spectral range encompassing the first predefined spectral range, the second predefined spectral range, and the third predefined spectral range is incident upon the polarization sensitive hologram <NUM>, the polarization sensitive hologram <NUM> outputs diffuse light (e.g., diffuse light <NUM>, <NUM>, <NUM>) having wavelengths corresponding to the wavelengths of the incident light. Polarization sensitive hologram <NUM> is also configured to receive light <NUM> having a wavelength that is outside the wider spectral range encompassing the first predefined spectral range, the second predefined spectral range, and the third predefined spectral range, and transmit the light <NUM>, without change in polarization or direction, regardless of the polarization of the light <NUM>.

In some embodiments, the polarization sensitive hologram <NUM> may be configured to diffuse light that is incident upon the polarization sensitive hologram <NUM> with an incident angle that is within a wider incident angle range encompassing a first predefined incident angle range, a second predefined incident angle range that is different from the first predefined incident angle range, or a third predefined incident angle range that is different from the first predefined incident angle range and the second incident angle spectral range. For example, the optically anisotropic molecules <NUM>-<NUM>, disposed between the first surface <NUM>-<NUM> and the second surface <NUM>-<NUM>, may be arranged such that the first optical diffuser layer diffuses light having the first circular polarization and incident upon polarization sensitive hologram <NUM> at first angle θ1 that is within the first predefined incident angle range, and outputs diffused first light. Optically anisotropic molecules <NUM>-<NUM>, disposed between the second surface <NUM>-<NUM> and the third surface <NUM>-<NUM>, are arranged such that the second optical diffuser layer diffuses light having the first circular polarization and incident upon the polarization sensitive hologram <NUM> at a second angle that is within the second predefined incident angle range, and outputs diffuse light. Optically anisotropic molecules <NUM>-<NUM>, disposed between the third surface <NUM>-<NUM> and the fourth surface <NUM>-<NUM>, are arranged such that the third optical diffuser layer diffuses light having the first circular polarization and incident upon the polarization sensitive hologram <NUM> at a third angle that is within the third predefined incident angle range, and outputs diffuse light. Thus, when incident light having the first polarization is incident upon the polarization sensitive hologram <NUM> at an incident angle that is within the wider incident angle range encompassing the first predefined incident angle range, the second predefined incident angle range, or the third predefined incident angle range, the polarization sensitive hologram <NUM> outputs diffuse light. Polarization sensitive hologram <NUM> is also configured to receive light incident upon the polarization sensitive hologram <NUM> at an incident angle that is outside the wider incident angle range encompassing the first predefined incident angle range, the second predefined incident angle range, and the third predefined incident angle range, and transmit the light without change in polarization or direction, regardless of the polarization or wavelength of the light.

Although polarization sensitive hologram <NUM> is shown in <FIG> to include three optical diffuser layers, it is understood that the polarization sensitive hologram <NUM> may include any number of optical diffuser layers.

<FIG> is a schematic diagram illustrating an optical diffuser <NUM>, corresponding to any of the optical diffusers <NUM>, <NUM>, <NUM>-n, according to some embodiments. Each rod <NUM> is a representation of an orientation of an optically anisotropic molecule in the optical diffuser <NUM>. Dashed lines <NUM> demarcate transitions between different domains <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>. In general, the boundaries can be located anywhere in the polarization sensitive optical diffuser. In some embodiments, the boundaries are periodic such that the boundaries are spaced apart evenly (e.g., forming a periodic structure of domains). Although three domains are shown for illustrative purposes, the optical diffuser <NUM> may have any number of domains.

As shown, optically anisotropic molecules in each domain are aligned to form a grating-like pattern. Thus, in each domain, the optically anisotropic molecules are configured to diffract incident light, having a desired handedness and being within predetermined angular and wavelength ranges, in a specific direction. As shown, the alignment of the optically anisotropic molecules vary slightly between two adjacent domains and thus, optically anisotropic molecules in adjacent domains are configured to diffract the incident light in different directions, resulting in an overall effect of diffuse light being output from the optical diffuser <NUM>. For example, the optically anisotropic molecules in domain <NUM>-<NUM> may be configured to direct (e.g., diffract) the incident light in a first direction, the optically anisotropic molecules in domain <NUM>-<NUM> are configured to direct (e.g., diffract) the incident light in a second direction that is different from the first direction, and the optically anisotropic molecules in domain <NUM>-<NUM> are configured to direct (e.g., diffract) the incident light in a third direction that is different from each of the first and second directions. Thus, the combined effect of diffracting light in slightly different directions at different domains of the optical diffuser <NUM> results in the incident light being diffused and output as diffuse light. Additionally, just as an optical grating can be designed to redirect light at a predetermined direction (e.g., predetermined angle), the optical diffuser <NUM> can also be designed to output diffuse light such that a chief ray of the output diffuse light propagates in a predetermined direction (e.g., forms a predetermined angle with respect to a surface of the optical diffuser <NUM>).

In some embodiments, an optical diffuser may include an alignment layer (e.g., a photoalignment layer, a layer including organic or inorganic compounds including photosensitive groups) and helical structures formed by optically anisotropic molecules. In such cases, the alignment layer is formed by adding a layer of photoalignment material on a surface of the optical diffuser. The alignment layer is then exposed to alignment light (e.g., linearly, circularly, or elliptically polarized light) with a desired intensity and incident angle. The alignment light is scanned over the alignment layer while rotating polarization of the alignment light, effectively writing an x-y alignment pattern onto an alignment layer in two dimensions. After preparation of the alignment layer, a layer of optically anisotropic molecules is applied onto the alignment layer, forming helical structures. The x-y alignment pattern of the alignment layer defines the orientation of the helical structures of the optically anisotropic molecules. After formation of the helical structures, the layer of optically anisotropic molecules is firmed (e.g., fixed, set, or cured) to form a polymer. In some embodiments, the firming includes thermal or UV curing. In some embodiments, helical structures are formed of liquid crystals, such as cholesteric liquid crystals. The helical structures are aligned along helical axes. In some embodiments, each of the helical axes are substantially parallel to the z-axis (e.g., each helical axis and the z-axis form an angle less than <NUM> degree). Alternatively, the helical axes may form a non-zero angle with respect to the z-axis. In some embodiments, the optically anisotropic molecules are rotated in a same rotational direction (forming a helical twist) about a respective helical axis.

In some embodiments, a polarization sensitive optical diffuser does not include an alignment layer and the helical structures of the polarization sensitive optical diffuser are formed without an alignment layer.

In some embodiments, an optical diffuser includes bulk liquid crystal. In such cases, an x-y-z alignment pattern can be written in three dimensions in the bulk liquid crystal material.

<FIG> is a flowchart of a method <NUM> of displaying images in accordance with some embodiments. Method <NUM> includes (operation <NUM>) providing image light (e.g., image light <NUM>-<NUM>, <NUM>-<NUM>) from an image source <NUM> and (operation <NUM>) receiving the image light at a first optical diffuser <NUM>. Method <NUM> also includes, when the image light received at the first optical diffuser <NUM> has a first polarization (e.g., image light <NUM>-<NUM>), (operation <NUM>) diffusing the image light at the first optical diffuser <NUM> to output first diffused image light (e.g., first diffused image light <NUM>) having the first polarization. The method <NUM> further includes (operation <NUM>), when the image light <NUM>-<NUM> received at the first optical diffuser <NUM> has a second polarization that is different from the first polarization, (i) transmitting the image light <NUM>-<NUM> through the first optical diffuser <NUM>, (ii) converting the image light <NUM>-<NUM> from the second polarization to the first polarization, (iii) diffusing the image light <NUM>-<NUM> having the first polarization at a second optical diffuser <NUM> to output second diffused image light <NUM> having the first polarization, (iv) converting the second diffused image light <NUM> from the first polarization to the second polarization, and (v) transmitting the second diffused image light <NUM> having the second polarization through the first optical diffuser <NUM>.

In light of these principles, we now turn to certain embodiments of a varifocal polarization sensitive diffusive display device.

In accordance with some embodiments, a display device (e.g., display device <NUM>) includes an image source (e.g., image source <NUM>) and a display (e.g., display <NUM>). The image source is configured to project image light (e.g., image light <NUM>-<NUM>, <NUM>-<NUM>). The display includes a first optical diffuser (e.g., first optical diffuser <NUM>) and a second optical diffuser (e.g., second optical diffuser <NUM>). The display is configured to receive the image light, diffuse the image light at the first optical diffuser when the image light has a first polarization, and diffuse the image light at the second optical diffuser when the image light has a second polarization that is different from (e.g., orthogonal to) the first polarization.

In accordance with some embodiments, a display device (e.g., display device <NUM>) includes an image source (e.g., image source <NUM>) configured to project image light (e.g., image light <NUM>-<NUM>, <NUM>-<NUM>). The image light is configurable to have a first polarization or a second polarization (e.g., LCP or RCP, or vice versa) that is different from the first polarization. The display device also includes a display (e.g., display <NUM>) that includes a first optical diffuser (e.g., first optical diffuser <NUM>) and a second optical diffuser (e.g., second optical diffuser <NUM>). The display is configured to receive the image light, diffuse the image light at the first optical diffuser when the image light is configured to have the first polarization, and diffuse the image light at the second optical diffuser when the image light is configured to have the second polarization.

According to the claimed invention, each of the first optical diffuser (e.g., first optical diffuser <NUM>) and the second optical diffuser (e.g., second optical diffuser <NUM>) is configured to diffuse first light having the first polarization and to transmit second light having the second polarization.

According to the claimed invention, the display (e.g., display <NUM>) is further configured to output first diffused image light (e.g., first diffused image light <NUM>) having the first polarization when the image light is configured to have the first polarization (e.g., first image light <NUM>-<NUM>). The display is also configured to output second diffused image light (e.g., second diffused image light <NUM>) having the second polarization when the image light is configured to have the second polarization (e.g., second image light <NUM>-<NUM>). The first optical diffuser includes a first surface (e.g., first surface <NUM>-A) and is configured to receive the image light at the first surface. The first diffused image light and the second diffused image light are each output from the first surface.

According to the claimed invention, the display (e.g., display <NUM>) further includes a first optical retarder (e.g., first optical retarder <NUM>) disposed between the first optical diffuser (e.g., first optical diffuser <NUM>) and the second optical diffuser (e.g., second optical diffuser <NUM>). Each of the first optical diffuser and the second optical diffuser is configured to reflectively diffuse light having the first polarization and transmit light having the second polarization. The first optical retarder is configured to receive the image light (e.g., image light <NUM>-<NUM>) transmitted through the first optical diffuser. The first optical retarder is configurable to: (i) convert the image light from the second polarization to the first polarization such that the image light (e.g., image light <NUM>-<NUM>) is diffused by the second optical diffuser as second diffused image light (e.g., second diffused image light <NUM>) having the first polarization, (ii) receive the second diffused image light, and (iii) convert the second diffused image light from the first polarization to the second polarization so that the second diffused image light is transmitted by the first optical diffuser.

According to the claimed invention, the display (e.g., display <NUM>) further includes a first optical retarder (e.g., first optical retarder <NUM>) disposed between the first optical diffuser (e.g., first optical diffuser <NUM>) and the second optical diffuser (e.g., second optical diffuser <NUM>). When the image light is configured to have the second polarization (e.g., second image light <NUM>-<NUM>), the first optical diffuser is configured to transmit the image light and the first optical retarder is configured to receive the image light transmitted through the first optical diffuser. The first optical retarder is configurable to convert the polarization of the image light from the second polarization to the first polarization such that the image light is diffused by the second optical diffuser as second diffused image light (e.g., second diffused image light <NUM>) having the first polarization. The first optical retarder is also configured to receive the second diffused image light, convert the polarization of the second diffused image light from the first polarization to the second polarization, and to output the second diffuse image light such that the second diffused image light is transmitted by the first optical diffuser.

In some embodiments, the display (e.g., display <NUM>) further includes one or more third optical diffusers (e.g., optical diffusers <NUM>-<NUM> and <NUM>-<NUM>) disposed between the first optical diffuser (e.g., first optical diffuser <NUM>) and the second optical retarder (e.g., second optical diffuser <NUM>, <NUM>-n).

In some embodiments, the display (e.g., display <NUM>) further includes one or more second optical retarders (e.g., optical retarders <NUM>-<NUM> and <NUM>-<NUM>). Each optical retarder of the one or more second optical retarders corresponds to a respective optical diffuser of the one or more third optical diffusers and is disposed between the respective optical diffuser and the first optical diffuser (e.g., optical retarder <NUM>-<NUM> corresponds to optical diffuser <NUM>-<NUM> and is disposed between optical diffuser <NUM>-<NUM> and first optical diffuser <NUM>). The each optical retarder is configured to transmit the image light (e.g., second image light <NUM>-<NUM>) transmitted through the first optical diffuser and propagating toward the second optical diffuser (e.g., second optical diffuser <NUM>, <NUM>-n) without changing its polarization. The each optical retarder is also configured to transmit the first diffused image light (e.g., first diffused image light <NUM>) output from the second optical diffuser and propagating toward the first optical diffuser without changing its polarization.

In some embodiments, the display (e.g., display <NUM>) further includes one or more fourth optical diffusers (e.g., optical diffuser <NUM>-n). The second diffuser (e.g., second optical diffuser <NUM>, <NUM>-<NUM>) is disposed between the first optical diffuser (e.g., first optical diffuser <NUM>) and the one or more fourth optical diffusers.

In some embodiments, the display (e.g., display <NUM>) further includes one or more third optical retarders (e.g., optical retarder <NUM>-n). Each optical retarder of the one or more third optical retarders corresponds to a respective optical diffuser of the one or more fourth optical diffusers and is disposed between the respective optical diffuser of the one or more fourth optical diffusers and the second optical diffuser (e.g., optical retarder <NUM>-n corresponds to optical diffuser <NUM>-n and is disposed between optical retarder <NUM>-n and second optical diffuser <NUM>).

In some embodiments, the first optical retarder (e.g., first optical retarder <NUM>) is an active optical retarder (e.g., a switchable optical retarder) configurable to be in any of a first state and a second state (e.g., "on" state and "off' state, or vice versa). In the first state (e.g., "off' state), the optical retarder is configured to convert the polarization of the image light transmitted through the first optical diffuser from the second polarization to the first polarization (e.g., convert the polarization of second image light <NUM>-<NUM> from the second polarization to the first polarization). In the second state, the optical retarder is configured to transmit the image light transmitted through the first optical diffuser without changing its polarization (e.g., transmit second image light <NUM>-<NUM>).

In some embodiments, the display device (e.g., display device <NUM>) further includes a first switchable optical retarder (e.g., switchable optical retarder <NUM>) configured to receive any of the first diffused image light (e.g., first diffused image light <NUM>) and the second diffused image light (e.g., second diffused image light <NUM>), and to output third diffused image light (e.g., third diffused image light <NUM>). The first switchable optical retarder is configurable to be in a third state when the image light has the first polarization or a fourth state when the image light has the second polarization (e.g., in an "on" state when first image light <NUM>-<NUM> is output from image source <NUM> or in an "off' state when second image light <NUM>-<NUM> is output from image source <NUM>, or vice versa). The third diffused image light has a third polarization (e.g., LCP or RCP) regardless of whether the first switchable optical retarder is in the first state or the second state. The display device also includes a lens assembly (e.g., lens assembly <NUM>) configured to receive the third diffused image light output from the first switchable optical retarder, and focus the third diffused image light with a first optical power. The lens assembly is also configured to transmit light (e.g., second ambient light <NUM>) having a fourth polarization different from the third polarization at a second optical power that is different from the first optical power. The first switchable optical retarder is disposed between the display and the lens assembly.

In some embodiments, the display (e.g., display <NUM>) is configured to transmit a portion (e.g., second portion <NUM>-<NUM>) of ambient light (e.g., ambient light <NUM>) incident upon the display and the lens assembly is configured to transmit the portion (e.g., second portion <NUM>-<NUM> as second ambient light <NUM>) of ambient light with the second optical power.

In some embodiments, the image source (e.g., image source <NUM>) includes a projector (e.g., projector <NUM>) configured to output image light having an initial polarization (e.g., image light <NUM>'). The image source also includes a second switchable optical retarder (e.g., switchable optical retarder <NUM>) disposed between the projector and the polarization sensitive optical element. The second switchable optical retarder is configured to receive the image light having the initial polarization, and configurable to be in a first state or a second state (e.g., "on" or "off' state, or vice versa). The image light (e.g., image light <NUM>") output from the image source is configured to have the first polarization when the second switchable optical retarder in the first state and the image light output from the image source is configured to have the second polarization when the second switchable optical retarder is in the second state. The image source also includes a polarization sensitive optical element (e.g., polarization sensitive optical element <NUM>) configured to project the image light in a first direction toward the first optical diffuser when the image light is configured to have the first polarization (e.g., project image light <NUM>' as first image light <NUM>-<NUM>) and to project the image light in a second direction toward the second optical diffuser when the image light is configured to have the second polarization (e.g., project image light <NUM>' as second image light <NUM>-<NUM>).

In some embodiments, the first optical diffuser (e.g., first optical diffuser <NUM>) and the second optical diffuser (e.g., second optical diffuser <NUM>) have a same optical axis (e.g., optical axis <NUM>), and the image source (e.g., image source <NUM>) is located at an off-axis position relative to the optical axis.

In some embodiments, the first optical diffuser (e.g., first optical diffuser <NUM>) is spaced apart from the second optical diffuser (e.g., second optical diffuser <NUM>) by a distance larger than <NUM> micrometers (e.g., distance D1 and D2 are each no smaller than <NUM> micrometers).

In some embodiments, each of the first and second optical diffusers (e.g., first optical diffuser <NUM>, second optical diffusers <NUM> and <NUM>) includes a polarization sensitive hologram (e.g., polarization sensitive hologram <NUM>, <NUM>).

In some embodiments, a respective optical diffuser of the first optical diffuser (e.g., first optical diffuser <NUM>) and the second optical diffuser (e.g., second optical diffusers <NUM> and <NUM>) includes a first optical surface (e.g., first optical surface <NUM>-<NUM>, <NUM>-<NUM>), a second optical surface (e.g., second optical surface <NUM>-<NUM>, <NUM>-<NUM>) opposite to the first optical surface, optically anisotropic molecules (e.g., optically anisotropic molecules <NUM>, <NUM>-<NUM>) disposed between the first optical surface and the second optical surface. The optically anisotropic molecules are arranged such that the respective optical diffuser is configured to diffuse the first light (e.g., light <NUM>) having the first polarization and to transmit the second light (e.g., light <NUM>) having the second polarization.

In some embodiments, the first light includes third light in a first wavelength range (e.g., light <NUM>) and fourth light (e.g., light <NUM>) in a second wavelength range. A respective optical diffuser of the first optical diffuser and the second optical diffuser (e.g., first optical diffuser <NUM>, second optical diffusers <NUM> and <NUM>) includes a first optical surface (e.g., first optical surface <NUM>-<NUM>), a second optical surface (e.g., second optical surface <NUM>-<NUM>), a third optical surface (e.g., third optical surface <NUM>-<NUM>), first optically anisotropic molecules (e.g., optically anisotropic molecules <NUM>-<NUM>) disposed between the first optical surface and the second optical surface, and second optically anisotropic molecules (e.g., optically anisotropic molecules <NUM>-<NUM>) disposed between the second optical surface and the third optical surface. The first optically anisotropic molecules are arranged to diffuse the third and the second optically anisotropic molecules are arranged to diffuse the fourth light.

In some embodiments, the first light includes fifth light in a first incident angle range and sixth light in a second incident angle range. A respective optical diffuser of the first optical diffuser and the second optical diffuser (e.g., first optical diffuser <NUM>, second optical diffusers <NUM> and <NUM>) includes a first optical surface (e.g., first optical surface <NUM>-<NUM>), a second optical surface (e.g., second optical surface <NUM>-<NUM>), a third optical surface (e.g., third optical surface <NUM>-<NUM>), first optically anisotropic molecules (e.g., optically anisotropic molecules <NUM>-<NUM>) disposed between the first optical surface and the second optical surface, and second optically anisotropic molecules (e.g., optically anisotropic molecules <NUM>-<NUM>) disposed between the second optical surface and the third optical surface. The first optically anisotropic molecules are arranged to diffuse the fifth light and the second optically anisotropic molecules are arranged to diffuse the sixth light.

In some embodiments, the optically anisotropic molecules in an optical diffuser are arranged in a plurality of domains. Each domain of the plurality of domains includes a portion of the optically anisotropic molecules forming a grating-like pattern. Portions of optically anisotropic molecules in adjacent domains are configured to diffract the light in different directions.

In accordance with some embodiments, a display device includes a first optical diffuser and a second optical diffuser. The display device is configured to: receive the image light; diffuse the image light at the first optical diffuser when the image light has a first polarization; and diffuse the image light at the second optical diffuser when the image light has a second polarization different from the first polarization. In some embodiments, the display device does not include an image source (e.g., the image source is separate from the display device).

In accordance with some embodiments, a method (e.g., method <NUM>) of displaying images includes (operation <NUM>) providing image light (e.g., image light <NUM>-<NUM>, <NUM>-<NUM>) and (operation <NUM>) receiving the image light at a first optical diffuser (e.g., first optical diffuser <NUM>). The method also includes (operation <NUM>), diffusing the image light at the first optical diffuser to output first diffused image light (e.g., first diffused image light <NUM>) having the first polarization when the image light has a first polarization (e.g., image light <NUM>-<NUM>). The method further includes (operation <NUM>), when the image light has a second polarization that is different from (e.g., orthogonal to) the first polarization (e.g., image light <NUM>-<NUM>): (i) transmitting the image light through the first optical diffuser, (ii) converting the image light from the second polarization to the first polarization, (iii) diffusing image light having the first polarization at a second optical diffuser (e.g., second optical diffuser <NUM>) to output second diffused image light having the first polarization, (iv) converting the second diffused image light from the first polarization to the second polarization, and (v) transmitting the second diffused image light having the second polarization through the first optical diffuser.

In accordance with some embodiments, a method (e.g., method <NUM>) of displaying images includes projecting first image light having a first polarization (e.g., image light <NUM>-<NUM>) and diffusing the first image light at a first optical diffuser (e.g., first optical diffuser <NUM>) to output first diffused image light (e.g., first diffused image light <NUM>) having the first polarization. The method also includes projecting second image light having a second polarization (e.g., image light <NUM>-<NUM>) that is different from (e.g., orthogonal to) the first polarization. The method also includes transmitting the second image light through the first optical diffuser, converting the second image light into third image light having the first polarization, and diffusing the third image light at a second optical diffuser (e.g., second optical diffuser <NUM>) to output second diffused image light. The second diffused image light having the first polarization. The method further includes converting the second diffused image light into third diffused image light having the second polarization, and transmitting the third diffused image light through the first optical diffuser.

According to the claimed invention, each of the first optical diffuser (e.g., first optical diffuser <NUM>) and the second optical diffuser (e.g., second optical diffuser <NUM>) is configured to diffuse light having the first polarization and to transmit light having the second polarization.

Although various drawings illustrate operations of particular components or particular groups of components with respect to one eye, a person having ordinary skill in the art would understand that analogous operations can be performed with respect to the other eye or both eyes. For brevity, such details are not repeated herein.

Although some of various drawings illustrate a number of logical stages in a particular order, stages which are not order dependent may be reordered and other stages may be combined or broken out. While some reordering or other groupings are specifically mentioned, others will be apparent to those of ordinary skill in the art, so the ordering and groupings presented herein are not an exhaustive list of alternatives. Moreover, it should be recognized that the stages could be implemented in hardware, firmware, software or any combination thereof.

Claim 1:
A display device, comprising:
an image source (<NUM>) configured to project image light; and
a display including a first optical diffuser (<NUM>) and a second optical diffuser (<NUM>), wherein the display is configured to:
receive the image light;
diffuse the image light at the first optical diffuser when the image light has a first polarization; and
diffuse the image light at the second optical diffuser when the image light has a second polarization different from the first polarization;
wherein the display is further configured to:
output first diffused image light having the first polarization when the image light is configured to have the first polarization; and
output second diffused image light having the second polarization when the image light is configured to have the second polarization, wherein
the first optical diffuser includes a first surface and is configured to receive the image light at the first surface; and
the first diffused image light and the second diffused image light are each output from the first surface;
wherein the display device further comprises:
a first optical retarder (<NUM>) disposed between the first optical diffuser and the second optical diffuser, wherein:
each of the first optical diffuser and the second optical diffuser is configured to:
reflectively diffuse light having the first polarization; and
transmit light having the second polarization;
the first optical retarder is configured to receive the image light transmitted through the first optical diffuser; and
the first optical retarder is configurable to:
convert the image light from the second polarization to the first polarization such that the image light is diffused by the second optical diffuser as second diffused image light having the first polarization;
receive the second diffused image light; and
convert the second diffused image light from the first polarization to the second polarization so that the second diffused image light is transmitted by the first optical diffuser.