Patent Description:
It is desirable to develop technology that makes displayed content more immersive. Displayed content may be static or dynamic. Static content may comprise a still image. Dynamic content may comprise filmed video content, augmented reality (AR) content, or virtual reality (VR) content.

Some bright light sources that can be viewed in real life may blind a user, due to glare. Glare inhibits the human capability to gather visual information from an environment. For example, human dark vision can be inhibited by bright headlamps at night. Glare can also distract a user from performing a task. For example, glare from direct sunlight may distract a driver or a pilot. Different people have different sensitivities to glare, differently affecting their ability to perform a task.

<CIT> describes a near eye display (NED). The NED includes an electronic display configured to output image light to an optical element. The optical element is configured to receive the image light, direct the image light, and form an image at the eye. The NED also includes an angle selective filter having a curved surface. The angle selective filter is configured to filter out light beams of light exiting the optical element and having an angle of incidence on the curved surface larger than a cut-off angle of incidence.

<CIT> describes a glare visor for reducing ambient light intensity perceived by a wearer viewing a head-up display employing display light including a given wavelength(s) of light. The visor includes a visor body comprising optically transparent material which is partially absorbing of light of visible optical wavelengths thereby to reduce the intensity of ambient light transmitted therethrough to the wearer. A transparent optical coating is formed upon a surface of the visor body which is partially transmissive of light of visible optical wavelengths amongst which it is preferentially transmissive of light of a subrange of wavelengths for including therein the wavelength(s) of display light. This permits a perceived enhancement of contrast between display light relative to ambient light.

<CIT> describes a system for imposing a filter between a vehicle driver's eyes and a source of light including at least one detector facing inward into a compartment in the vehicle toward a likely position of the head of the vehicle driver and arranged to obtain images of the eyes of the driver and a processor coupled to the detector(s) and arranged to determine the location of the driver's eyes based on analysis of the images obtained by the detector(s) and to obtain information about objects exterior of the vehicle providing sources of light from the images obtained by the detector(s) based on reflections off of the driver's eyes, i.e., the position of such objects. A filter, such as a pixelated screen, is imposed between the sources of light and the driver's eyes based on the location of the driver's eyes and the information about the exterior objects providing the sources of light.

<CIT> describes a display control device for a vehicle that includes: a display controller that displays a predetermined display image on a windshield of the vehicle; a visibility reducing area detector that detects a presence or an absence of a visibility reducing area which reduces a visibility of the display image on the windshield; and a gaze detector that detects a gaze of a driver. When the display image overlaps with the visibility reducing area and the driver does not keep the gaze on the display image, the display controller moves the display image to an outside of the visibility reducing area.

<CIT> describes multiple imaging areas that are disposed in a one-to-one relationship with multiple optical lenses disposed in a substantially coplanar alignment. A baffle wall interposed between the multiple imaging areas is provided with means for diffusively reflecting incident light rays. Low frequency components are removed from the spatial frequencies of multiple images captured in the multiple imaging areas, whereupon the multiple images are compared to determine the amount of parallax and measure the distance to the object. This allows for preventing degradation in the accuracy of distance measurement when light rays emanating from a high-intensity object located outside of the field angle are reflected from the baffle wall and impinge on the imaging area.

In a first aspect, there is provided an apparatus according to claim <NUM>.

In some, but not necessarily all examples the display is configured to render the display content at up to a first peak luminance, and the glare system is configured to render the glare content at up to a second peak luminance greater than the first peak luminance.

In some, but not necessarily all examples the glare system comprises a glare emitter, and optics configured to superimpose the glare content from the glare emitter onto the field of view. In some, but not necessarily all examples the optics comprises a beam combiner configured to combine the display content of the display and the glare content of the glare emitter.

In some, but not necessarily all examples the glare system is configured to render the glare content at different positions across the field of view concurrently, while the display renders the display content.

In some, but not necessarily all examples the apparatus comprises a controller configured to control the position of the glare content rendered by the glare system. In some, but not necessarily all examples the controller is configured to control the position of the glare content in dependence on control of the display content rendered by the display. In some, but not necessarily all examples the controller is configured to control the position of the glare content based on a predetermined or random pattern. In some, but not necessarily all examples the controller is configured to dynamically move the position of the glare content across the field of view while the display renders the display content.

In some, but not necessarily all examples the apparatus comprises an eye sensor configured to detect at least one ocular characteristic while the display content and the glare content are rendered. In some, but not necessarily all examples the apparatus is configured to cause information from the eye sensor to be stored in non-volatile memory.

In some, but not necessarily all examples the display is a near-eye display.

According to various, but not necessarily all, embodiments of the invention there is provided a head-mounted display system comprising the near-eye display and the glare system for one or each eye of a user.

In a second aspect, there is provided a method according to claim <NUM>.

<FIG> illustrates an apparatus <NUM> comprising: a display <NUM> configured to render display content <NUM>; and a glare system <NUM> configured to render glare content <NUM>. The apparatus <NUM> is configured to combine the display content <NUM> and the glare content <NUM> to form a combined rendered image <NUM> with one or more regions of elevated brightness. Examples of combined images <NUM> are shown in <FIG>. <FIG> illustrates a retinal image <NUM> in a user's eye <NUM>, representing the combined image <NUM> as seen by the user.

Rendering in this context means providing in a form that is perceived by the user. The display content <NUM> means display output of the display <NUM> and the glare content <NUM> means glare output of the glare system <NUM>. The display content <NUM> may be static or dynamic.

The display <NUM> as referred to herein is a display source which acts as a source of first pixelated light <NUM> providing the display content <NUM>. The display source may be a display panel as illustrated, such as a backlit liquid crystal display or a light emitting diode display. Alternatively, the display <NUM> may be configured as a projector configured to project the display content <NUM> onto a reflective screen of the apparatus <NUM> or directly onto a user's retina.

The display <NUM> is configured to render the display content <NUM> at up to a first peak luminance. The first peak luminance of the display <NUM> is limited by design constraints such as a required high spatial resolution of pixels or a required high dynamic range while displaying dark scenes. The first peak luminance takes into account any illuminator, such as a backlight, which the display <NUM> may have.

The glare system <NUM> acts as a source of second light <NUM> providing glare content <NUM>. The glare system <NUM> is configured to render glare content <NUM> at up to a second peak luminance that is brighter than the first peak luminance. Depending on implementation, the second peak luminance of the glare system <NUM> may be at least double the first peak luminance of the display <NUM>. The second peak luminance of the glare system <NUM> may have a value in the order of magnitude of thousands of candela per square metre (cd/sqm) or more, not in the order of magnitude of hundreds or less. For example, a second peak luminance of approximately 5000cd/sqm±1000cd/sqm can produce a strong glare effect if required by the implementation. In some, but not necessarily all of the above examples, the first peak luminance of the display <NUM> could have a value in the order of magnitude of hundreds of cd/sqm, which enables the glare to stand out even if the display <NUM> is operated at peak luminance.

The relative positioning of the glare system <NUM> and the display <NUM> within the apparatus <NUM> are not limited to the arrangement shown in <FIG>. Further, the features of the apparatus <NUM> may be provided by a single device or module as shown, or by a plurality of devices or modules that form a system when combined.

<FIG> illustrates how the glare content <NUM> can be positioned with respect to the display content <NUM>.

As illustrated in <FIG>, the display content <NUM> is rendered by the display <NUM> over a field of view <NUM>. The field of view <NUM> is the amount of field of view of user vision occupied by the display content <NUM>, as modified by any optics, such as magnifiers, that the apparatus <NUM> may have.

The field of view <NUM> of the display content <NUM> may cover the whole (full-screen) or at least a portion of an available display field of view (DFOV) of the display <NUM>. A DFOV is the amount of field of view of user vision occupied by the physical display <NUM>. A larger diagonal screen size of the display <NUM> occupies a greater DFOV.

As illustrated in <FIG>, the glare system <NUM> is configured to render the glare content <NUM> in the field of view <NUM> of the display content <NUM>. The glare content <NUM> comprises at least one region (area) of glare content <NUM> extending across a portion of the field of view <NUM> of the display content <NUM>. In some implementations, a region of glare content <NUM> is capable of being small enough relative to the display content <NUM> to have a distinguishable shape within the combined image <NUM>, such as a spot or line. A region of glare content <NUM> may be controllable by the glare system <NUM> to have diffuse edges. In some examples, a region of glare content <NUM> may be controllable to have sharp, defined edges. Other regions of the display content <NUM> in the combined image <NUM> may be non-brightened by the glare content <NUM>.

As illustrated in <FIG>, the glare system <NUM> is configured to render the glare content <NUM> at different positions inside the field of view <NUM> of the display content <NUM>. The glare system <NUM> may be configured to vary the position of the glare content <NUM> within the boundaries of the DFOV.

Rendering glare content <NUM> inside a field of view <NUM> would be understood to include keeping rendered glare content <NUM> fully within the boundaries of the field of view <NUM>, and depending on implementation could include allowing an area/line of glare content <NUM> predominantly inside the field of view <NUM> to overlap at least one boundary of the field of view <NUM>.

Rendering glare content <NUM> at different positions would be understood to include the capability to render first glare content <NUM> at a first position in the field of view <NUM> at a first time, and to render second glare content <NUM> at a second different position in the field of view <NUM> at the first time and/or at a later time, wherein the second position is offset from the first position in a first dimension (e.g. horizontal) and/or in a second orthogonal dimension (e.g. vertical) in the same plane as the first dimension. As a result, the combined image <NUM> can have spatially variable or spatiotemporally variable glare/peak luminance.

In some, but not necessarily all examples the glare system <NUM> is configured to dynamically move a region of glare content <NUM> from a first position p1 within (inside) the field of view <NUM> at time t1, to a second position p2 within the field of view <NUM> at time t2. The second position p2 is offset from the first position p1 in the first dimension and/or in the second dimension. Dynamic movement means that the region of glare content <NUM> is moved while continuing to be rendered by the glare system <NUM>. The glare system <NUM> may have sufficient refresh rate/frame rate and spatial resolution to provide a smooth motion.

In some, but not necessarily all examples the glare system <NUM> may be configured to render a first region of glare content <NUM> at position p1 at time t1 and a second region of glare content <NUM> at position p2 at time t2. The second region of glare content <NUM> is not rendered at time t1 and the first region of glare content <NUM> is not rendered at time t2.

In some, but not necessarily all examples the glare system <NUM> may be configured to render a plurality of regions of glare content <NUM> p1, p2 concurrently.

In some, but not necessarily all examples the brightness of the glare content <NUM> may be controllable.

Although the examples described herein refer to the ability of the glare system <NUM> to render glare content <NUM> inside a field of view <NUM>, it would be appreciated that the glare system <NUM> may or may not additionally be configured to render glare content <NUM> at positions wholly or predominantly outside the field of view <NUM>.

<FIG>, <FIG>, <FIG> illustrate example implementations of the apparatus <NUM> wherein the display <NUM> is a near eye display (NED). The apparatus <NUM> forms at least part of a head-mounted display (HMD) system <NUM>. An HMD system <NUM> is worn on the head or as part of a helmet. A display <NUM> may be provided in front of one eye (monocular HMD) or each eye <NUM> (binocular HMD).

<FIG> illustrates an example configuration of an HMD system <NUM> for one eye <NUM>. The same configuration may be applied for the other eye in a binocular HMD system <NUM>.

The display <NUM> is small relative to non-NEDs. The HMD system <NUM> comprises an optional eyepiece <NUM>. The eyepiece <NUM> or a separate lens may magnify and/or re-focus the rendered display content <NUM> to enlarge and/or sharpen the effective DFOV and improve user immersion. In an example implementation, the eyepiece <NUM> is a Fresnel lens.

In some, but not necessarily all examples the HMD system <NUM> may be configured for virtual reality. The display content <NUM> may be virtual reality content. The HMD system <NUM> may be substantially opaque so that the user cannot see the real world through the display content <NUM>.

In <FIG>, the display <NUM> is in front of the user's eye <NUM>. However, examples of the present disclosure may be applied in other configurations in which the display <NUM> is away from the centre or even the periphery of a user's field of view, and an optical arrangement directs the display content <NUM> towards the centre of the user's field of view and to the user's eye <NUM>.

<FIG> shows an example implementation of the glare system <NUM> that does not require moving parts. In <FIG>, the glare system <NUM> is applied to the HMD of <FIG>, however, the glare system <NUM> may alternatively be applied to <FIG>, or other compatible examples. The apparatus <NUM> from <FIG> may provide a combined image <NUM> as shown in <FIG>.

The glare system <NUM> comprises a plurality of glare emitters <NUM>. The use of multiple spatially distributed glare emitters <NUM> enables the position of glare content <NUM> to be controlled by controlling which glare emitters <NUM> are illuminated, without a requirement for moving parts such as micro-electromechanical actuators.

The glare emitters <NUM> comprise light emitting diodes or a suitable alternative. The glare emitters <NUM> are collectively brighter than an effective backlight brightness of the display <NUM>. Effective backlight brightness means once light from the backlight has passed through the liquid crystals/pixels of the display <NUM>. The glare emitters <NUM> are individually brighter than light emitting diodes of the display <NUM>.

The illustrated glare emitters <NUM> are configured to render pixelated glare content <NUM>. The glare emitters <NUM> may be arranged in a pixel matrix as shown. The matrix may form a regular array or an irregular pattern. The regular array may form orthogonal rows and columns. One row (or column) is illustrated, comprising glare emitters <NUM> at positions (i, j), (i+<NUM>, j),. , (i+n, j), where i is a row and j is a column or vice versa. If an irregular pattern is used, the glare emitters <NUM> may be positioned according to areas in the field of view <NUM> where it is anticipated that glare will be required. For example, the spatial density of glare emitters <NUM> may be: greater in the periphery or in the centre of the field of view <NUM>; greater in a left half or in a right half of the field of view <NUM>; greater in a top half or a bottom half of the field of view <NUM>; or a combination thereof.

The size of a region (area) of glare content <NUM>, and the number of regions, are controllable by controlling how many glare emitters <NUM> are illuminated. The brightness of glare content <NUM> may be controllable by controlling the brightness of a glare emitter <NUM>.

The spatial resolution of the glare emitters <NUM> may be less than a spatial resolution of the display <NUM>. For example, the display <NUM> may have an angular resolution (spatial resolution) of at least five pixels per degree more than the spatial resolution of the glare emitters <NUM>. The lower spatial resolution of the glare system <NUM> enables the selection of glare emitters <NUM> with a greater peak luminance.

The glare emitters <NUM> may be supported by a supporting structure <NUM> such as a substrate.

The glare emitters <NUM> may be substantially opaque. The glare emitters <NUM> and any associated supporting structure <NUM> may be peripherally offset from the DFOV, as shown.

Therefore, the glare system <NUM> comprises optics <NUM> configured to superimpose the glare content <NUM> from the glare emitters <NUM> onto the field of view <NUM> of the display content <NUM> to control the position of the glare content <NUM> in the combined (merged) image <NUM>. The optics <NUM> comprises any optical device that can change a direction of a beam of light, such as a beam combiner.

In <FIG>, the optics <NUM> comprises a beam combiner configured to combine the display content <NUM> of the display <NUM> and the glare content <NUM> of the glare emitters <NUM>.

The beam combiner is configured to receive from the display <NUM> first pixelated light <NUM> defining the display content <NUM>. The first pixelated light <NUM> may be incident in a first direction.

The beam combiner is configured to receive from the glare emitters <NUM> second light <NUM> defining the glare content <NUM>. The second light <NUM> may be pixelated light if the glare emitters <NUM> are arranged as a matrix. The second light <NUM> is incident in a second direction which is different from the first direction and depends on how the glare emitters <NUM> are located and oriented relative to the display <NUM>. In <FIG>, the first and second directions are substantially orthogonal.

The beam combiner is configured to combine the first pixelated light <NUM> defining the display content <NUM> with the second light <NUM> defining the glare content <NUM> to provide, as an output third pixelated light <NUM> defining the combined image <NUM>. Various beam combiners are commercially available. Some are formed by joining two prisms to form a cube. The beam combiner may e.g. consist of a partially reflecting surface or a dichroic mirror surface, which can e.g. be flat or have optical power.

In an alternative implementation not shown in <FIG>, the position of glare content <NUM> may be controlled via a mechanism (not shown) that slides or tilts the optics <NUM> (active optics <NUM>), and/or that slides or tilts a glare emitter <NUM> (active glare emitter <NUM>), and/or that slides or tilts an additional optical arrangement, such as a lens, installed between the optics <NUM> and the glare emitters <NUM>.

In various examples, fewer glare emitters <NUM> or only one glare emitter <NUM> may be provided. An example of a single glare emitter <NUM> is a high-brightness illuminator (backlight) for a second display (not shown). Pixels of the second display may selectively block the unpixellated light from the illuminator to control the position of glare content <NUM> transmitted through the second display towards the optics <NUM>. In an implementation, the second display is a monochrome display, when the glare content <NUM> is substantially white light. In an implementation, the second display is a liquid crystal display. In another example, the position of glare content <NUM> emitted by a single smaller glare emitter <NUM> may be controlled by active optics <NUM>.

<FIG> illustrates the apparatus <NUM> of <FIG> comprising an eye sensor <NUM>. The eye sensor <NUM> is configured to detect at least one ocular characteristic while the display content <NUM> and the glare content <NUM> are rendered. Alternatively, the eye sensor <NUM> could be applied to the apparatus <NUM> of <FIG>, or any other compatible example. An eye sensor <NUM> may be provided for one or each eye <NUM>.

In some, but not necessarily all examples the eye sensor <NUM> is configured to detect at least one ocular characteristic indicative of gaze direction.

In some, but not necessarily all examples the eye sensor <NUM> is configured to detect at least one ocular characteristic indicative of pupil size.

In some, but not necessarily all examples the eye sensor <NUM> is configured to detect at least one ocular characteristic indicative of blinking.

Commercially available eye sensors include infra-red sensors and visible light cameras. An infra-red sensor may operate in the near infra-red spectrum, in some examples.

<FIG> illustrates an example implementation of the eye sensor <NUM>. The apparatus <NUM> comprises an emitter <NUM> configured to emit electromagnetic radiation <NUM> and an eye sensor <NUM> configured to detect reflected electromagnetic radiation <NUM> reflected from the cornea.

One or more of the above ocular characteristics may be used for clinical vision testing or for simulation such as virtual reality simulation.

Clinical vision testing may comprise examining a user's response to glare. An improper pupil size, improper blinking, or a delayed response, may indicate a clinical condition. The combination of glare content <NUM> and display content <NUM> enables examination of the effect of glare on sight and cognition. The user may be asked questions about what they can see on the display <NUM> while they are subjected to controlled glare content <NUM>. The precise positioning of glare content <NUM> enables precise determination of how much of the user's central and peripheral vision is affected by glare. The optional eye sensor <NUM> may help to support a diagnosis, or even enable automatic feedback control of the examination. An HMD system <NUM> is useful for clinical vision testing because a wider field of view can be tested, because the apparatus <NUM> is in a fixed position relative to the eye <NUM> to aid repeatability, and because a user's vision can optionally be shielded from ambient light. For example, the HMD system <NUM> may comprise a shroud (not shown) to block out ambient light.

The eye sensor <NUM> may be employed to improve immersion in a simulated activity such as playing a video game or operating a virtual reality simulator such as a flight simulator or driving simulator. For example, the user may be able to issue input commands by modifying their gaze direction and/or by blinking.

In some, but not necessarily all examples the apparatus <NUM> is configured to cause information from the eye sensor <NUM> to be stored in non-volatile memory, such as the memory shown in <FIG>. The information may be stored permanently until deleted or overwritten. This supports tracking of the user during clinical vision testing, or tracking of user performance during a simulated activity. Other information that may be stored includes, for example: glare content <NUM>; display content <NUM>; user data; microphone data; camera data; localization data, etc..

In some, but not necessarily all examples information from the eye sensor <NUM> is provided as feedback to control graphical rendering of the display content <NUM> and/or to control rendering of the glare content <NUM>. For example, glare content <NUM> may be brightened or dimmed for user-specific optimization. The glare content <NUM> may be controlled to be bright enough to cause a desired user reaction, but not so bright that it triggers an extreme reaction.

In <FIG>, the eye sensor <NUM> forms part of the HMD system <NUM> and faces the eye <NUM>. The eye sensor <NUM> may require its own optics. <FIG> and <FIG> illustrate alternative arrangements that improve ease of packaging and may allow shared optics.

<FIG> and <FIG> show that the emitter <NUM> for the eye sensor <NUM> may be relocated, and may direct its electromagnetic radiation <NUM> to the optics <NUM> of the glare system <NUM>. In <FIG> and <FIG>, the optics <NUM> comprises the beam combiner. The beam combiner directs the electromagnetic radiation <NUM> to the cornea where it is reflected <NUM> and detected by the eye sensor <NUM>.

<FIG> and <FIG> show that the electromagnetic radiation <NUM> from the emitter <NUM> for the eye sensor <NUM> may be incident to the optics <NUM> in the second direction corresponding to the direction of the glare content <NUM>.

<FIG> and <FIG> show that an emitter <NUM> for the eye sensor <NUM> is located between individual glare emitters <NUM>. A plurality of emitters <NUM> for the eye sensor <NUM> may be provided. The glare emitters <NUM> and the eye sensor emitters <NUM> may form an alternating pattern. The glare emitter(s) <NUM> and an eye sensor emitter(s) <NUM> may be supported by a common supporting structure <NUM>.

In <FIG>, the eye sensor <NUM> is located in the original position shown in <FIG>. However, <FIG> shows that the eye sensor <NUM> may also be relocated. In <FIG>, the optics <NUM> of the glare system <NUM> acts as a beam splitter to direct the electromagnetic radiation <NUM> reflected from the user's cornea to the eye sensor <NUM>.

<FIG> shows that the optics <NUM> may direct the reflected electromagnetic radiation <NUM> parallel to the second direction of the glare content <NUM>, to the eye sensor <NUM>. In <FIG>, the eye sensor <NUM> and the glare emitter(s) <NUM> are supported by a common supporting structure <NUM>.

<FIG>, <FIG> illustrate further example implementations of the apparatus <NUM> wherein the display <NUM> is a NED. The apparatus <NUM> forms at least part of an HMD system <NUM>. In contrast to <FIG>, the HMD system <NUM> may be configured for augmented reality. The display content <NUM> may be augmented reality content, augmenting a user's view of the real world with virtual content. The HMD system <NUM> may be substantially transparent so that the user can see the real world through the display content <NUM>.

<FIG> shows an HMD system <NUM> to which the glare system <NUM> may be applied. The display <NUM> is away from the centre or even the periphery of a user's field of view. An optical arrangement directs the display content <NUM> towards the centre of the user's field of view and to the user's eye <NUM>. In some, but not necessarily all examples the HMD system <NUM> is shaped like eyeglasses.

The HMD system <NUM> may utilize curved combiner technology or waveguide technology, for example. Available waveguide technologies include: diffractive waveguides; holographic waveguides; reflective waveguides; or retinal projection.

<FIG> illustrates an HMD system <NUM> that utilizes waveguide technology. <FIG> illustrates guiding optics <NUM>, <NUM> directing the first pixelated light <NUM> defining the display content <NUM> to an exit pupil expander <NUM>. The exit pupil expander <NUM> is provided instead of the eyepiece <NUM> of <FIG>, to direct the third pixelated light defining the combined image <NUM> into a desired part of the user's field of view. The exit pupil expander <NUM> may be provided by a light guide comprising an in-coupling diffraction grating <NUM> and an out-coupling diffraction grating <NUM>.

In some, but not necessarily all examples an illuminator <NUM> for the display <NUM> is provided separately from the display <NUM>. A beam splitter <NUM> of the guiding optics directs light <NUM> from the illuminator <NUM> towards the display <NUM>. The illuminator <NUM> may output unpixellated light <NUM>. The display <NUM> selectively reflects the unpixellated light <NUM> to produce the first pixelated light <NUM> defining the display content <NUM>. The peak luminance of the display <NUM> may be determined, at least in part, by the peak luminance of the illuminator <NUM>.

In this example, the display <NUM> is provided by a liquid crystal on silicon device (LCOS). Such a device comprises a reflective layer and an array of liquid crystal (LC) pixel control elements. The array of LC pixel control elements are able to selectively control reflection of incident light pixel by pixel.

<FIG> illustrates the HMD system <NUM> of <FIG> comprising a glare system <NUM>. The beam splitter <NUM> of the guiding optics acts as a beam combiner for the glare content <NUM>, in analogy to the beam combiner of <FIG>. The glare emitter <NUM> may be implemented using one of the techniques described in relation to <FIG>. The beam splitter/combiner <NUM>/<NUM> directs the first pixelated light <NUM> defining the display content <NUM> and the second light <NUM> defining the glare content <NUM> to the exit pupil expander <NUM>.

<FIG> illustrates the HMD system <NUM> of <FIG> comprising an eye sensor <NUM>. The emitter <NUM> for the eye sensor <NUM> is positioned near the glare emitters <NUM> in analogy with <FIG>. The eye sensor <NUM> is positioned with line of sight to the eye <NUM>, and may for example be supported at the periphery of the exit pupil expander <NUM>. In an alternative implementation, the emitter <NUM> for the eye sensor <NUM> may be located proximally to the eye sensor <NUM>.

<FIG> illustrates a combined image <NUM> comprising virtual reality display content <NUM> and glare content <NUM>. The combined image <NUM> is the retinal image <NUM> formed in the user's eye <NUM>. The combined image <NUM> may be rendered by the apparatus <NUM> of <FIG>, or by the virtual reality HMD system <NUM> of <FIG>.

The combined image <NUM> in the non-limiting example of <FIG> comprises two regions of glare content <NUM> concurrently rendered at two different positions across the field of view <NUM> of the display content <NUM>. The glare content <NUM> obscures some information in the display content <NUM>. <FIG> illustrates that the size of a region of glare content <NUM> is capable of being controlled to be small, for example occupying an area less than <NUM>% of an area of the field of view <NUM> of the display content <NUM>. However, the regions of glare content <NUM> could be larger.

<FIG> illustrates a combined image <NUM> comprising augmented reality display content <NUM> and glare content <NUM>, against a background of real objects that may be seen through a substantially transparent HMD system <NUM>, for example.

In this non-limiting example, the combined image <NUM> in <FIG> comprises two regions of glare content <NUM> concurrently rendered at two different positions across the field of view <NUM> of the display content <NUM>. The glare content <NUM> obscures some information in the display content <NUM>. For example, the glare content <NUM> makes recognition of the teapot in the display content <NUM> more challenging.

The apparatus <NUM> may comprise a controller configured to control the position and/or brightness of the glare content <NUM> rendered by the glare system <NUM> for the purposes described herein. <FIG> shows an example of a controller <NUM>.

In some, but not necessarily all examples the controller <NUM> may be configured to control the position of the glare content <NUM> in dependence on control of the display content <NUM> rendered by the display <NUM>. The display content <NUM> may be controlled by the controller <NUM> or by a different controller.

In some, but not necessarily all examples, the display content <NUM> depicts a virtual visual scene. This may occur in a simulation use case. A virtual visual scene refers to a representation of virtual visual space viewed from a virtual point of view (position and/or orientation) within a virtual visual space. The point of view may be a first-person perspective or a third-person perspective. A virtual visual space refers to a fully or partially artificial environment that may be viewed, which may be three dimensional.

In some, but not necessarily all examples the display content <NUM> depicts at least one virtual visual object. A virtual visual object may be an artificial virtual object (e.g. a computergenerated virtual object) or it may be an image of a real object in a real space that is live or recorded. A virtual object may be within a virtual visual scene (e.g. virtual reality) or displayed alone (e.g. augmented reality).

Some virtual objects may emit virtual light, for example a virtual sun or a virtual lamp, while other virtual objects merely reflect virtual light, for example the ground. The controller <NUM> may be configured to control the position of the glare content <NUM> to maintain a region of glare content <NUM> at the location of the virtual light-emitting virtual object within the virtual visual scene. This improves immersion because the brightness of bright virtual light-emitting virtual objects such as the sun can be better-replicated. In some examples, a light-reflecting virtual object can also be bright, such as a mirror reflecting the sun, in which case glare content <NUM> might be rendered at the location of a bright virtual light-reflecting virtual object.

In some, but not necessarily all examples a location at which glare content <NUM> is to be rendered is selected in dependence on an indication of the brightness of the virtual light associated with that location, for example associated with a virtual object at the location. In some implementations, a location could be selected if its associated indicated brightness is above a threshold.

The apparatus <NUM> may be provided with a human-machine interface or gesture/body motion sensor for enabling control of the point of view and/or for enabling manipulation of virtual objects. The control is enabled with a certain number of degrees of freedom, such as 3D position and/or 3D orientation. The position(s) of glare content <NUM> may be dynamically moved across the field of view <NUM> of the display content <NUM> to move within the combined image <NUM>, in dependence on dynamic control of the display content <NUM>. For example, the glare content <NUM> may be dynamically moved in dependence on the control of the point of view and/or manipulation of the virtual object, to maintain correspondence of the glare content <NUM> to bright virtual objects.

The above example improves immersion in simulation activities for leisure or for training and assessment, or even clinical vision tests that rely on similar display content <NUM>.

In other examples, the control of the position of the glare content <NUM> may not depend on the display content <NUM>. The controller <NUM> may be configured to control the position (and optionally brightness) of the glare content <NUM> based on a predetermined or random pattern or a predetermined set of rules. This may be useful in specific clinical vision testing or other experiments that require repeatability whether or not the display content <NUM> changes. A predetermined pattern is nonrandom but is not affected by the display content <NUM> being displayed. An example rules-based approach relies on feedback from the eye sensor <NUM>, to perform the above-mentioned user-specific optimization of glare content <NUM>.

A few examples of clinical vision tests with which the apparatus <NUM> may be used include: stereo vision tests; visual acuity tests; colour recognition tests; visual field tests; contrast sensitivity tests; or halogen glare sensitivity tests. Various clinical conditions and human characteristics can affect glare sensitivity, such as: age; fatigue; eye diseases; eye degeneration; diabetes; migraines; drug side-effects; brain damage; and intoxication.

A few examples of simulation activities with which the apparatus <NUM> may be used include training, accreditation, or video game simulations. The activity represented by the display content <NUM> may comprise controlling a machine such as driving a car or piloting an aircraft, and/or controlling a virtual person in first-person perspective or in third-person perspective. One example simulation use case other than controlling a machine is simulating a structured environment such as a workplace or other architectural space, to test user acceptability of glare levels from natural and/or artificial light. The glare levels could be increased or decreased depending on how glare-sensitive the individual users are.

The apparatus <NUM> may also be used in other contexts such as improving immersion when watching television or movies.

<FIG> illustrates an example of a controller <NUM>. Implementation of a controller <NUM> may be as controller circuitry. The controller <NUM> may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

The memory <NUM> stores a computer program <NUM> comprising computer program instructions (computer program code) that controls the operation of the apparatus <NUM> when loaded into the processor <NUM>. The computer program instructions, of the computer program <NUM>, provide the logic and routines that enables the apparatus to perform the methods illustrated in <FIG>. The processor <NUM> by reading the memory <NUM> is able to load and execute the computer program <NUM>.

As illustrated in <FIG>, the computer program <NUM> may arrive at the apparatus <NUM> via any suitable delivery mechanism <NUM>. The delivery mechanism <NUM> may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a Compact Disc Read-Only Memory (CD-ROM) or a Digital Versatile Disc (DVD) or a solid state memory, an article of manufacture that comprises or tangibly embodies the computer program <NUM>. The delivery mechanism may be a signal configured to reliably transfer the computer program <NUM>. The apparatus <NUM> may propagate or transmit the computer program <NUM> as a computer data signal.

Computer program instructions for causing an apparatus <NUM> to perform at least the following or for performing at least the following:.

References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixedfunction device, gate array or programmable logic device etc..

The blocks illustrated in <FIG> may represent steps in a method and/or sections of code in the computer program <NUM>. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

The recording of data may comprise only temporary recording, or it may comprise permanent recording or it may comprise both temporary recording and permanent recording, Temporary recording implies the recording of data temporarily. This may, for example, occur during sensing or image capture, occur at a dynamic memory, occur at a buffer such as a circular buffer, a register, a cache or similar. Permanent recording implies that the data is in the form of an addressable data structure that is retrievable from an addressable memory space and can therefore be stored and retrieved until deleted or over-written, although long-term storage may or may not occur. The use of the term 'capture' in relation to an image relates to temporary recording of the data of the image. The use of the term 'store' in relation to an image relates to permanent recording of the data of the image.

If it is intended to use 'comprise' with an exclusive meaning then it will be made clear in the context by referring to "comprising only one" or by using "consisting".

Thus 'example', for example', 'can' or 'may' refers to a particular instance in a class of examples.

The term 'a' or 'the' is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a/the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use 'a' or 'the' with an exclusive meaning then it will be made clear in the context. In some circumstances the use of 'at least one' or 'one or more' may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

Claim 1:
An apparatus (<NUM>) comprising:
a display (<NUM>) configured to render display content (<NUM>) over a field of view;
a glare system (<NUM>) comprising a plurality of glare emitters (<NUM>) and configured to render glare content (<NUM>) in the field of view (<NUM>), wherein the glare system (<NUM>) is configured to render the glare content (<NUM>) at different positions across the field of view at different times while the display renders the display content (<NUM>); and
a controller (<NUM>) configured to control the position of the glare content (<NUM>) rendered by the glare system (<NUM>).