Patent Description:
<CIT> teaches that light from an image displayed on a display screen is transmitted to an observer's eye by way of a dynamic optical element (such as a spatial light modulator or an electrically switchable holographic composite) which acts as a lens. The characteristics of the dynamic optical element can be altered so that it acts sequentially to direct light of different colors to the observer's eye. In one optional embodiment emitters on the display screen emit infra-red radiation which is projected by the dynamic lens as a broad wash onto the eye. Infra-red radiation reflected back from the eye is focussed by the dynamic lens onto detectors also provided on the display screen. The detectors are thus able to sense the direction of eye gaze, and the dynamic lens is controlled in dependence on this to create an area of high resolution in an area of interest centered on the direction of gaze, which is moved to follow the eye gaze as its direction alters. Other than in the area of interest, the dynamic lens has a relatively low resolution.

<CIT> teaches that new methods are presented for multiplexing volume holograms in electrooptic materials. Multiple volume holograms can be superimposed in a medium and be individually addressed by tuning the underlying refractive index of the medium or the crystal parameters, while keeping the external parameters (wavelength, angles) fixed.

According to aspects of the present invention there is provided a device and method, as defined in the accompanying independent claims.

As discussed above, display devices may be configured to project virtual images to a user's eye by providing image light to a hologram recorded in a holographic film. When the image light is provided to the hologram at a reference angle, the hologram diffracts the image light at a particular outbound angle. If the user's pupil is in a position such that light rays at the outbound angle intersect the pupil, the user is able to view the virtual image. However, if the pupil moves away from this position (e.g., if the user eye looks left, right, up or down), then the virtual image is no longer viewable by the user's eye. In other words, the nature of the holographic film is such that the virtual image is viewable with only a single, or very limited range of, pupil positions.

Accordingly, this description relates to projecting a virtual image to a user's eye such that the virtual image can be viewed from a variety of different pupil positions. In many examples, an initial step is to determine a position of a user eye. Image light is provided to a holographic film that includes multiple different holograms. Each hologram is recorded with the same reference beam, but the individual holograms are recorded differently. The differential recording is performed so that, for image light inbound at a given reference angle, each hologram diffracts the image light differently. In other words, each hologram differently "aims" or "redirects" light coming in at this inbound reference angle so that the light exits at a different diffraction angle. A state of the holographic film may be adjusted based on the determined position of the user's eye. The adjustment may cause a particular hologram to be illuminated/activated, the hologram being selected based on it having a diffraction angle that intersects the determined position of the user's eye. By adjusting the state of the holographic film to illuminate a particular hologram based on the position of the pupil of the user eye, the system enables viewing of virtual images even as the pupil significantly changes positions.

<FIG> shows an example display device that may include one or more of the example optical systems described herein. More particularly, <FIG> shows an example head-mounted display (HMD) device <NUM> in the form of a pair of wearable glasses with a near-eye display <NUM>. The HMD device <NUM> is shown in simplified form. In some implementations, the near-eye display <NUM> may be at least partially see-through such that virtual images may appear to augment a real-world environment viewable through the near-eye display <NUM>. In other implementations, the near-eye display <NUM> may be an occluding, virtual reality display. A near-eye display device may take any other suitable form than the example shown. Moreover, the concepts discussed herein may be broadly applicable to other types of display devices, such as large format display devices.

The HMD device <NUM> includes a controller <NUM> configured to control operation of the display <NUM>. Control of operation of the display <NUM> may be additionally or alternatively controlled by one or more computing devices (e.g., remote from the HMD device <NUM>) in communication with the HMD device <NUM>. The controller <NUM> may include a logic device and a storage device, as discussed in more detail below with respect to <FIG>. The logic device and storage device may be in communication with various sensors and display system components of the HMD device <NUM>.

The HMD device <NUM> also includes a holographic display system <NUM> controlled by the controller. Example display systems for use with holographic display system <NUM> are described in more detail below with reference to <FIG>.

The HMD device <NUM> may also include various sensors and related systems to provide information to the controller <NUM>. Such sensors may include, but are not limited to, one or more outward facing image sensors <NUM> and one or more inward facing image sensors <NUM>.

The one or more outward facing image sensors <NUM> may be configured to measure attributes of the physical environment in which the HMD device <NUM> is located. Such visual data of the physical environment may be used to provide video-based augmented reality display data to the holographic display system <NUM>. In one example, a live or semi-live video/image feed of the user's real-world environment, as imaged by the outward facing image sensors <NUM>, may be displayed via the holographic display system <NUM> to simulate a see-through display system. Virtual objects may be displayed over the images of the real-world environment to present an augmented reality scene to the user. In another example, the outward facing image sensors <NUM> may image the real-world environment for position tracking and mapping of objects in the real-world environment.

In one example, the one or more image sensors <NUM> may include a visible-light camera configured to collect a visible-light image of a physical space. Further, the one or more image sensors <NUM> may include a depth camera configured to collect a depth image of a physical space. More particularly, in one example, the depth camera is an infrared time-of-flight depth camera. In another example, the depth camera is an infrared structured light depth camera.

The one or more inward facing image sensors <NUM> may be configured to acquire image data in the form of gaze tracking data from a wearer's eyes. The controller <NUM> of the HMD device <NUM> may be configured to determine gaze directions of each of a wearer's eyes in any suitable manner based on the information received from the image sensors <NUM>. For example, one or more light sources such as infrared light sources may be configured to cause a glint of light to reflect from the cornea of each eye of a wearer. The one or more image sensors <NUM> may then be configured to capture an image of the wearer's eyes. These images of the glints and of the pupils may be used by the controller <NUM> to determine an optical axis of each eye. Using this information, the controller <NUM> may be configured to determine a direction the wearer is gazing (also referred to as a gaze vector). In one example, the one or more light sources, the one or more inward facing image sensors <NUM>, and the controller <NUM> may collectively comprise a gaze detector. This gaze detector is configured to determine a position of a user eye, a gaze vector, a pupil position, head orientation, eye gaze velocity, eye gaze acceleration, change in angle of eye gaze direction, and/or any other suitable tracking information of the user eye. In other implementations, a different type of gaze detector/sensor may be employed in the HMD device <NUM> to measure one or more gaze parameters of the user's eyes. In some implementations, eye gaze tracking may be recorded independently for each eye of a wearer of the HMD device <NUM>.

In one particular example, a pupil of a human eye may have a minimum diameter of about <NUM> millimeters. At that size, the pupil can move to a discrete number of independent (e.g., not overlapping) positions. In some cases, there may be up to forty independent positions. Accordingly, the controller <NUM> may be configured to identify which position, of the possible forty positions, the pupil is in.

The controller <NUM> is configured to adjust a state of the holographic display system <NUM> based on a determined position of the user eye. This adjustment allows virtual image to be viewed from the determined position. In particular, the controller <NUM> may adjust a state of a holographic film of the holographic display system <NUM> to diffract image light to intersect the position of the user eye as will be discussed in further detail below.

<FIG> show an example optical system <NUM> in simplified form. In one example, the optical system <NUM> may be employed in the holographic display system <NUM> for the HMD device <NUM> of <FIG>, or any other suitable display device. The optical system <NUM> includes optical elements arranged in front of, or near, a user eye <NUM>. A controller <NUM> controls operation of the optical system <NUM> to, among other things, determine a position of the user eye <NUM> and adjust a state of the optical system to direct image light to the user eye <NUM>.

The optical system <NUM> includes an optical sensor <NUM> for imaging the user eye <NUM>. The controller <NUM> determines a position of a pupil <NUM> (or another aspect) of the user eye <NUM> based on image data received from the optical sensor <NUM>. In one example, the optical sensor <NUM> corresponds to the one or more inward facing image sensors <NUM> shown in <FIG>. The controller <NUM> determines the position of the pupil <NUM> as described above, or in any other suitable manner.

The optical system <NUM> includes an image source <NUM> configured to output image light to a waveguide <NUM>. The image source <NUM> may take any suitable form. The image source <NUM> may employ various image formation technologies including, but not limited to, a liquid crystal display (LCD), a liquid crystal on silicon (LCOS) display, or another suitable display technology. The image source <NUM> may employ any suitable backlight or other illumination source. In one example, the image source <NUM> may include one or more laser light sources (e.g., laser diodes) to provide spatially coherent image light to the waveguide <NUM>. A laser has a narrow linewidth (e.g., emits light at a single wavelength), that produces little or no rainbow effect when diffracted by a hologram.

The image source <NUM> may provide image light to the waveguide <NUM> in any suitable manner. For example, the image source <NUM> may provide image light via an input coupling prism, embossed grating, volume hologram, slanted diffraction grating, or other coupling grating or hologram. In the illustrated implementation, the image source <NUM> provides image light to the waveguide <NUM> at a fixed angle of incidence. However, in other implementations, the image source <NUM> may vary the angle of incidence at which image light is provided to the waveguide <NUM>.

The waveguide <NUM> may be configured to propagate image light received from the image source <NUM> to a field of view of the user eye <NUM>. In particular, image light may propagate through the waveguide <NUM> until eventually exceeding a total internal reflection (TIR) critical angle after a certain number of reflections. Once the critical angle is exceeded, the image light exits the waveguide <NUM>. The waveguide <NUM> may take any suitable form. In the illustrated implementation, the waveguide <NUM> has a wedge shape. In other implementations, the waveguide <NUM> may have a constant thickness instead of a wedge shape.

A holographic film <NUM> may be configured to receive image light exiting the waveguide <NUM>. In one example, the holographic film <NUM> is adjacent the waveguide <NUM> in the field of view of the user, though the holographic film may be situated in any suitable manner/location. The holographic film <NUM> includes a plurality of different holograms <NUM>. In one example, each hologram <NUM> is a Bragg grating. Each hologram <NUM> may be recorded in the holographic film <NUM> with the same reference beam. In other words, in one example with N holograms, hologram <NUM> is recorded using reference beam R; hologram <NUM> is recorded using the same reference beam R; and so on through hologram N. However, each of these holograms maybe recorded differently so as to differently diffract image light received from the waveguide <NUM> at the reference angle. In particular, each hologram <NUM> may be recorded in such a manner that each hologram <NUM> diffracts image light at a different angle. For example, the different angles of diffraction of the different holograms <NUM> may intersect different possible positions of the pupil <NUM>. In one example, a number of holograms <NUM> of the holographic film <NUM> may correspond to the total number of possible pupil positions (e.g., <NUM>-<NUM>) of the user eye <NUM>.

The controller <NUM> is configured to adjust a state of the holographic film <NUM> based on a position <NUM> of the user eye <NUM>, as determined via the optical sensor <NUM>. In particular, the controller <NUM> adjusts the state of the holographic film <NUM> such that a particular one of the holograms <NUM> is selected/activated/excited to diffract image light to intersect the determined position <NUM> of the user eye <NUM>. In such a state of the holographic film <NUM>, the other non-active holograms do not diffract the image light to the position of the user eye. Instead, the non-active holograms transmit the image light.

By varying the state of the holographic film <NUM> to select different holograms that diffract image light differently, the optical system <NUM> may provide image light selectively to a range of possible positions of the pupil <NUM>. For example, as shown in <FIG>, the pupil <NUM> is oriented at a first position 218A. The controller <NUM> determines, via optical sensor <NUM>, that the pupil is in this first position 218A, and in response adjusts a state of the holographic film <NUM>. The state adjustment of the holographic film excites a first hologram having a particular angle of diffraction that diffracts the image light to intersect the position 218A.

In another example (<FIG>), the pupil <NUM> is oriented in a second position 218B. The controller <NUM> determines the second position 218B (e.g., via optical sensor <NUM>), and adjusts a state of the holographic film <NUM> to excite a second, different hologram. The second hologram has a particular angle of diffraction that diffracts the image light to intersect the position 218B, and is selected/activated for that reason. In other words, the controller <NUM> adjusts the state of the holographic film <NUM> responsive to a change in pupil position so that image light is provided to the pupil at the changed pupil position. In particular, with each change in pupil position, a different hologram <NUM> of the holographic film <NUM> may be excited to appropriately diffract image light to the pupil <NUM> as it moves.

The plurality of holograms <NUM> may be recorded in the holographic film <NUM> in any suitable manner. In the present invention each hologram <NUM> is recorded with the same reference beam, but with the holographic film <NUM> being subject to a different amount of shear. Shear may include any suitable amount of unaligned forces applied to one part of the holographic film <NUM> in one direction, and another part of the holographic film <NUM> in the opposite direction. The shear force(s) may be applied to the holographic film <NUM> in any suitable manner. By adjusting the amount of shear applied to the holographic film <NUM> for each recording, the angle of diffraction can be varied for each hologram, e.g., so that each hologram has a diffraction angle that is different from one or more of the others. In other words, multiple instances of the same hologram (e.g., having the same reference and signal) may be recorded on the holographic film <NUM>, and each hologram may be oriented differently based on a different amount of shear applied during recording of the hologram.

In one particular example, the holographic film <NUM> may be recorded by generating a reference beam and a signal to create a desired holographic interference pattern. For example, the reference beam may include planar wave fronts. For a Bragg grating, the signal also may include planar wave fronts, for example. For a 3D image, the signal may include light scattered off a 3D object, for example. The interference pattern may be printed on an ion beam machine. The printed interference pattern may be placed proximate to a thick photosensitive film, such as dichromated gelatin or silver halide. The substrate of the film may be illuminated via a laser until the hologram has been copied into the substrate. In one example, the copy process is repeated to record each hologram in the film, and for each recording, a different amount of shear is to be applied to the film. In another example, a master volume hologram is printed that includes all of the different holograms, allowing the master volume hologram to be copied into the substrate of the photosensitive film in a single recording step.

In implementations of the optical system <NUM> that employ the holographic film <NUM> including different holograms recorded with different amounts of shear being applied to the holographic film <NUM>, the state of the holographic film <NUM> may be altered by adjusting an amount of shear applied to the holographic film <NUM>.

<FIG> and <FIG> schematically show an example holographic film <NUM> under different amounts of shear that affect an operating state of a hologram <NUM> of the holographic film <NUM>. <FIG> and <FIG> show vector diagrams corresponding to the hologram <NUM> under different amounts of shear, and will be referenced throughout discussion of the hologram <NUM>.

<FIG> shows the holographic film <NUM> under a larger amount of shear relative to that shown in <FIG>. Specifically, a top surface <NUM> of the holographic film <NUM> (e.g., a Bragg grating) is shifted in an opposite direction relative to a bottom surface <NUM> of the holographic film <NUM>. A light ray <NUM> is provided to the holographic film <NUM> at an angle (α). Application of the larger amount of shear to the holographic film <NUM> distorts the holographic film <NUM>. In particular, the distortion of the holographic film <NUM> causes the planes of the Bragg grating to rotate relative to the angle (α) of light ray <NUM>. As such light ray <NUM> is incident on the hologram <NUM> at an angle different than the reference angle, and light ray <NUM> is transmitted through the hologram <NUM> without being diffracted. In other words, the hologram <NUM> is in a non-active state in which the hologram <NUM> acts transparent to the light ray <NUM>.

<FIG> shows a vector diagram <NUM> corresponding to the hologram <NUM> when the holographic film <NUM> is subjected to the larger amount of shear, as shown in <FIG>. A reference vector <NUM> corresponds to the light ray <NUM> shown in <FIG>. Reference vector <NUM> has a length equal to a reciprocal of the wavelength of the light ray <NUM>. Vector <NUM> has a direction perpendicular to the wave front of the light ray <NUM>. A hologram vector <NUM> corresponds to the hologram <NUM> shown in <FIG>. Hologram vector <NUM> has a length equal to a reciprocal of the distance between the planes of hologram <NUM>. Hologram vector <NUM> has a direction perpendicular to the planes of the hologram <NUM>. A circle <NUM> of constant radius is formed from a combination of a signal vector <NUM> and the reference vector <NUM> that were used to record the hologram <NUM>. In this case, the hologram vector <NUM> is not aligned with the circle <NUM> of constant radius (e.g., the ends of the vector do not lie on the perimeter of the circle). As such, light ray <NUM> is incident on the hologram <NUM> at an angle different from the reference angle, and the hologram <NUM> does not diffract light ray <NUM> as shown in <FIG>.

<FIG> shows the holographic film <NUM> under a smaller amount of shear relative to that shown in <FIG>. In particular, the top surface <NUM> of the holographic film <NUM> (e.g., a Bragg grating) is shifted in an opposite direction relative to the bottom surface <NUM> of the holographic film <NUM> to a lesser extent than in <FIG>. The light ray <NUM> is provided to the holographic film <NUM> at the same angle (α) as shown in <FIG>. Application of the smaller amount of shear to the holographic film <NUM> distorts the holographic film <NUM> to a lesser extent. In particular, the distortion of the holographic film <NUM> causes the planes of the Bragg grating to rotate relative to the angle (α) of the light ray <NUM> such that the light ray <NUM> is incident on the hologram <NUM> at the reference angle. As such, light ray <NUM> is incident on the hologram <NUM> at the reference angle, and light ray <NUM> is diffracted by the hologram <NUM>. In other words, the hologram <NUM> may be in an excited state in which the hologram <NUM> diffracts the light ray <NUM>.

<FIG> shows a vector diagram <NUM> corresponding to the hologram <NUM> when the holographic film <NUM> is subjected to the smaller amount of shear as shown in <FIG>. A reference vector <NUM> corresponds to the light ray <NUM> shown in <FIG>. A hologram vector <NUM> corresponds to the hologram <NUM> shown in <FIG>. A circle <NUM> of constant radius is formed from a combination of a signal vector <NUM> and the reference vector <NUM> that were used to record the hologram <NUM>. In this case, the hologram vector <NUM> is aligned with the circle <NUM> of constant radius (e.g., the ends of the vector do lie on the perimeter of the circle). As such, light ray <NUM> is incident on the hologram <NUM> at the reference angle, and the hologram <NUM> diffracts light ray <NUM> as shown in <FIG>.

Although the concept of applying shear to a holographic film is discussed in a context of a single hologram/Bragg grating, such a concept may be equally applicable to all holograms recorded in the holographic film.

Continuing with <FIG>, in implementations of the optical system <NUM> that employ a holographic film <NUM> that is adjusted by applying different amounts of shear, the optical system <NUM> may include a shearing mechanism <NUM> configured to adjust an amount of shear applied to the holographic film <NUM>. In particular, the controller <NUM> may control the shearing mechanism <NUM> to adjust the amount of shear applied to the holographic film.

<FIG> show an example shearing mechanism <NUM>. The shearing mechanism <NUM> includes one or more piezoelectric elements <NUM> connected to the holographic film <NUM>. In particular, the piezoelectric element <NUM> may be connected (<NUM>) to a top surface <NUM> of the holographic film <NUM> at a first position <NUM>, and (<NUM>) to a bottom surface <NUM> of the holographic film <NUM> at a second position <NUM>. In <FIG>, a controller <NUM> applies a first voltage to the piezoelectric element <NUM> to apply a first amount of shear, in which the first and second positions <NUM> and <NUM> are separated by a first distance D1. This first amount of shear may place a hologram <NUM> of the holographic film <NUM> in an excited state, as shown in <FIG>, in which the hologram diffracts image light inbound from the waveguide at the reference angle. In <FIG>, the controller <NUM> applies a second, different voltage to piezoelectric element <NUM> to apply a second, greater amount of shear. The second amount of shear causes the first and second positions <NUM> and <NUM> to separate by a second distance D2, which is greater than the first distance D1. In the depicted examples, the second amount of shear places the hologram <NUM> in a non-active state (<FIG>), in which the hologram transmits, as opposed to diffracts, light.

The above described scenarios are meant to be non-limiting. The controller <NUM> may control the piezoelectric element <NUM> in any suitable manner to apply any suitable amount of shear to the holographic film <NUM>. In one example, a <NUM> long piezoelectric element may be stretched/distorted up to <NUM> microns under a voltage of up to ~ <NUM> volts. Such a range of stretching/distortion may be suitable to apply different amounts of shear to the holographic film to excite any of the different holograms of the holographic film as desired.

Returning to <FIG>, in an alternative implementation, the holographic film <NUM> may include a mixture of liquid crystals and polymer (e.g., UV curing polymer) in which holograms <NUM> are recorded. In this example implementation, not part of the present invention, the holographic film may be adjusted, not through variable shear, but instead by applying an electric field (e.g., a voltage) to the holographic film <NUM>, so as to affect an orientation of the liquid crystals. In particular, the presence of the electric field may cause the liquid crystal molecules to be birefringent. Such a re-orientation of the liquid crystal molecules may have the same effect on light with appropriate linear polarization as a change in refractive index of the holographic film. Changing the apparent refractive index of the liquid crystal causes the average refractive index of the liquid crystal and the surrounding polymer to change. The change in the average refractive index causes the angle of the reference ray within the material to change (by Snells law). The change of the angle of the reference ray causes one of the recorded holograms to be selected/activated while the remainder of the holograms remain inactive. In other words, in such a configuration, different holograms may be selectively enabled/disabled by applying an appropriate voltage to the holographic film <NUM>.

The plurality of holograms <NUM> may be stored in the liquid crystal and polymer mixture of the holographic film <NUM>. Each hologram <NUM> may be recorded with the same reference beam. However, each hologram <NUM> may be activated at a different refractive index of the liquid crystal that is unique to the particular hologram in the holographic film <NUM>. Moreover, the different refractive indices may cause the image light to be diffracted at different angles relevant to each recorded hologram.

In one particular example, not part of the present invention, a liquid crystal display (e.g., having approximate dimensions of <NUM> by <NUM>) is aligned with a lens (e.g., having a <NUM> focal length). A reference beam and signal, both planar wave fronts, are directed through the aligned components to create a desired holographic interference pattern. A thick photosensitive film, such as dichromated gelatin, is placed in the focal plane of the lens to record the interference pattern. The recording step may be repeated at distances of ~ <NUM> while modulating the liquid crystal display appropriately to achieve different refractive indices for each hologram.

In implementations of the optical system <NUM> that employ the holographic film <NUM> recorded in this manner, the state of the holographic film <NUM> may be adjusted to excite a particular hologram <NUM> by adjusting a voltage applied to the holographic film <NUM>. For example, the controller <NUM> may apply a particular voltage to the liquid crystal structure of the holographic film <NUM> to adjust the refractive index of the liquid crystal structure to a selected refractive index corresponding to the particular hologram.

In some implementations, the controller <NUM> may control the image source <NUM> in conjunction with the holographic film <NUM>. In particular, the controller <NUM> may momentarily turn off the image source <NUM> when the controller adjusts the state of the liquid crystal structure of the holographic film <NUM>. Subsequently, once the state of the liquid crystal structure has changed, the controller <NUM> may turn the image source <NUM> back on. By controlling the image source <NUM> and the holographic film <NUM> in this manner, the user eye may not perceive any change in state of the holographic film <NUM>.

<FIG> shows an example method <NUM> for projecting an image. Method <NUM> may be performed by or on a display device such as HMD device <NUM> (<FIG>). In general, method <NUM> may be performed by any suitable display device in which a holographic film is employed that has multiple holograms recorded differently into the film using a common reference beam.

At <NUM>, method <NUM> includes determining, via an optical sensor, a position of a user eye. The position of the user eye may be determined in any suitable manner. In one example, a gaze vector of the user eye may be determined, as described above. In one example, the position of the user eye corresponds to a position of a pupil of the user eye.

At <NUM>, the method <NUM> includes providing, via an image source, image light to a holographic film of the display device. In one example (<FIG>), image light is provided from light source <NUM> to holographic film <NUM> via waveguide <NUM>. The holographic film includes multiple holograms recorded with the same reference beam, but recorded differently to differently diffract image light received from the image source.

At <NUM>, the method <NUM> includes adjusting, based on the determined position of the user eye, a state of the holographic film such that a particular one of the holograms diffracts image light to intersect the position of the user eye.

In the invention, the holograms of the holographic film is recorded while applying different amounts of shear to the holographic film during the recording of each hologram (or simulating such conditions in a master volume hologram). In some such implementations, at <NUM>, the method <NUM> includes controlling a shearing mechanism to adjust an amount of shear applied to the holographic film to adjust the state of the holographic film.

In some implementations, not part of the invention, the holograms of the holographic film may be recorded in a liquid crystal structure (e.g., a liquid crystal and polymer mixture). In some such implementations, at <NUM>, the method <NUM> optionally may include applying a particular voltage to the liquid crystal structure of the holographic film to adjust a refractive index of the liquid crystal structure to a selected refractive index corresponding to the particular hologram to adjust the state of the holographic film.

According to the above described method, a virtual image may be projected to a pupil of a user eye even as a position of the pupil changes across a range of motion of the pupil.

In some implementations, the methods and processes described herein may be tied to a computing system of one or more computing devices.

<FIG> schematically shows a non-limiting implementation of a computing system <NUM> that can enact one or more of the methods and processes described above. For example, the computing system <NUM> may correspond to the HMD device <NUM> shown in <FIG>.

For example, the logic machine <NUM> may be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs.

The logic machine <NUM> may include one or more processors configured to execute software instructions. For example, such instructions maybe executed by logic machine <NUM> to process eye imaging data, determine an eye position based on the eye imaging data, and control a state of optical system <NUM> to provide image light to a user's eye at the determined eye position. Additionally or alternatively, the logic machine <NUM> may include one or more hardware or firmware logic machines configured to execute hardware or firmware instructions. Processors of the logic machine <NUM> may be single-core or multicore, and the instructions executed thereon may be configured for sequential, parallel, and/or distributed processing. Individual components of the logic machine <NUM> optionally may be distributed among two or more separate devices, which may be remotely located and/or configured for coordinated processing. Aspects of the logic machine <NUM> may be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration.

Storage machine <NUM> includes one or more physical devices configured to hold instructions executable by the logic machine <NUM> to implement the methods and processes described herein.

For example, the logic machine <NUM> and the storage machine <NUM> may be integrated in the controller <NUM> shown in <FIG>, the controller <NUM> shown in <FIG>, and/or the controller <NUM> shown in <FIG>. In some implementations, the controllers <NUM>, <NUM>, and <NUM> may be implemented as purely hardware.

For example, the visual representation may include a virtual image. As the herein described methods and processes change the data held by the storage machine <NUM>, and thus transform the state of the storage machine <NUM>, the state of display subsystem <NUM> may likewise be transformed to visually represent changes in the underlying data. Such display devices may be combined with logic machine <NUM> and/or storage machine <NUM> in a shared enclosure, such as an HMD device, for example, or such display devices may be peripheral display devices.

In some implementations, the input subsystem <NUM> may comprise or interface with selected natural user input (NUI) componentry.

As non-limiting examples, the communication subsystem <NUM> may be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some implementations, the communication subsystem <NUM> may allow computing system <NUM> to send and/or receive messages to and/or from other devices via a network such as the Internet.

In the invention, a display device comprises an optical sensor configured to image a user eye, an image source configured to provide image light, a holographic film including a plurality of holograms, each hologram recorded with a same reference beam but recorded differently so as to differently diffract image light received from the light source, and a controller configured to <NUM>) determine, via the optical sensor, a position of the user eye, and <NUM>) adjust, based on the determined position of the user eye, a state of the holographic film such that a particular hologram of the plurality of holograms diffracts image light to intersect the position of the user eye. Each hologram is recorded with a different amount of shear applied to the holographic film. In one example implementation that optionally may be combined with any of the features described herein, non-active holograms other than the particular hologram do not diffract image light to the position of the user eye while the particular hologram diffracts image light to the position of the user eye. In the invention, the display device further comprises a shearing mechanism configured to adjust an amount of shear applied to the holographic film, and the state of the holographic film is adjusted by controlling the shearing mechanism to adjust the amount of shear applied to the holographic film. The shearing mechanism includes one or more piezoelectric elements, and controlling the shearing mechanism to adjust the amount of shear applied to the holographic film includes adjusting a voltage applied to the one or more piezoelectric elements. In one example implementation that optionally may be combined with any of the features described herein, the display further comprises a waveguide configured to propagate the image light from the image source to the holographic film, and the holographic film is adjacent the waveguide. In one example implementation that optionally may be combined with any of the features described herein, the display device is a near-eye display device. In one example implementation that optionally may be combined with any of the features described herein, the position of the user eye is a position of a pupil of the user eye.

Claim 1:
A display device (<NUM>) comprising:
an optical sensor (<NUM>) configured to image a user eye;
a light source (<NUM>) configured to provide image light;
a holographic film (<NUM>) having recorded thereon a plurality of holograms (<NUM>), each hologram recorded with a same reference beam but recorded differently so as to differently diffract image light received from the light source (<NUM>), wherein each of the plurality of holograms is recorded with a different amount of shear applied to the holographic film; and
a controller (<NUM>) configured to <NUM>) determine, via the optical sensor (<NUM>), a position of the user eye, and <NUM>) adjust, based on the determined position of the user eye, a state of the holographic film (<NUM>) such that a particular hologram (<NUM>) of the plurality of holograms diffracts image light to intersect the position of the user eye, wherein the state of the holographic film (<NUM>) can be altered by adjusting an amount of shear applied to the holographic film (<NUM>).