Patent ID: 12204093

DETAILED DESCRIPTION

Under many circumstances, the center energy propagation path, or energy propagation axis, is normal to the energy projection surface of an energy directing device. Under these circumstances, the groups of energy rays from each location on the energy surface are distributed in a solid angle around an axis which is normal to the energy directing surface, independent of location on the energy surface. In other words, at each location on the energy surface, the energy propagation axis is aligned with the normal to the display surface. We introduce the energy deflection angle, or simply deflection angle, as the angle that the energy propagation axis makes with the normal to the display surface. In general, the deflection angle gives the direction of energy flow from the energy surface. It describes the average deflection of a plurality of projection paths at a particular location on that energy surface, relative to a normal to that surface.

For some embodiments of an energy directing device, it may be advantageous to have the direction of energy propagation, or energy propagation axis, no longer be aligned with the normal to the display surface at some locations on the energy surface. In other words, for some locations on the energy directing surface, there is a nonzero deflection angle. In some embodiments, the deflection angle may change with position across the energy projecting surface of the energy directing device. This may be done to focus the projected energy rays to a more localized region. It may also allow the convergence locations for all the energy rays to be closer to the energy directing surface, if the groups of energy propagation paths corresponding to locations near the edges of the energy directing surface are tilted toward the center of the energy directing surface.

Many example diagrams in this disclosure demonstrate this principle by illustrating embodiments where light rays are projected by a holographic energy surface, such as a light field display surface. Each location on a holographic energy surface has a two-dimensional (2D) spatial coordinate, and projects a group of light rays at a plurality of angles. Each light ray is associated with a 2D angular coordinate, and together the 2D spatial coordinate and the 2D angular coordinates form a 4D coordinate for each energy projection path. In each example, it is possible to generalize the discussion to include energies of other types, such as mechanical energy, in which transducers create energy at an energy projecting surface which may be able to project ultrasound waves in multiple directions depending on the location on the energy projecting surface, or even multiple directions at each location on the energy projecting surface. These ultrasound waves may converge to form tactile surfaces in front of the energy surface.

An energy surface may be combined with arrays of waveguides in order to create an energy directing system.FIG.1Ashows an example wherein a single waveguide104A is placed over an energy source plane120defined by a plurality of individually-addressable energy source locations, such as locations110,111, and112at coordinates u0, uk, and u−k, respectively. In an embodiment, the energy source locations are defined on a seamless energy surface102. In an embodiment, the energy surface102may be the surface of a display panel or a surface of a relay medium. As such, in an embodiment, the energy source locations may be individual pixels of a display panel. In another embodiment, the energy source locations correspond to energy locations on a relayed energy surface.

In an embodiment, the waveguide104A is configured to propagate energy to and/or from an energy source location, such as location103, on the energy surface102, along an angle determined at least in part by the location of the energy source location103with respect to the waveguide104A. For example, some of the energy from the energy source location at uk111is received by the waveguide104A and propagated into a propagation path142defined by a chief ray propagation path132, corresponding to the location of energy source location uk111relative to waveguide104A. Similarly, the energy to and/or from the pixel at u−k112is received by the waveguide104A and directed along a propagation path141, which is defined by chief ray propagation path131, corresponding to the location of energy source location u−k112relative to waveguide104A. The chief ray130that is normal to the energy surface102is provided in this example by the energy source location u0110close to an axis of symmetry for the propagation paths of the waveguide104A, which is substantially aligned with energy propagation path130. The coordinates u0, uk, and u−kare angular coordinates of energy propagation paths in one dimension, axis U, but there is a corresponding angular coordinate in the orthogonal dimension, axis V. In a four-dimensional coordinate system, the waveguide104A may be assigned to have a single spatial coordinate in two dimensions (X,Y), and an energy source location associated with a waveguide may produce an energy propagation path with a two-dimensional angular coordinate (U, V). Together, these 2D spatial coordinates (X,Y) and 2D angular coordinates (U,V) form a 4-dimensional (4D) energy propagation path coordinate (X,Y,U,V) assigned to each energy source location103located in the energy source plane120.

As an example, in an embodiment, a four-dimensional light field may be defined by all the 4D coordinates (X,Y,U,V) for multiple waveguides at various spatial coordinates, each waveguide104A associated with multiple illumination source pixels103, each pixel with independent U, V coordinates.FIG.1Bshows a holographic electromagnetic energy directing system160comprised of a waveguide array disposed over an illumination source plane120defined by an energy surface102. Above the energy surface102, the holographic system160may include a waveguide array104comprised of waveguides104A,104B, and104C. Associated with each waveguide104A,104B, and104C is a group of pixels102A,102B, and102C, which projects and/or receives electromagnetic energy along propagation paths125A,125B, and125C, respectively. The array of waveguides104defines an energy directing surface101. The chief rays131,130, and132define a range of energy propagation paths directed through the waveguide104A at the minimum value, mid-value, and maximum value of light field angular coordinate U, respectively. Since the energy source locations of the energy surface102extend in two dimensions, there are a plurality of energy propagation paths through the waveguide104A in the light field angular coordinate V which is orthogonal to U, although these are not shown inFIG.1B. In other words, there is a bundle of light rays (energy propagation paths) that are projected from all the energy source locations associated with a waveguide104A, and these are substantially grouped around the center axis130. This center energy propagation axis, or energy propagation axis defines a line of symmetry, since it is often coincident with the approximate midpoint of the angular range of light rays projected from the energy directing system160at a particular (X,Y) location for waveguide104A, both in the horizontal and vertical dimensions. InFIG.1B, in an embodiment, the energy-inhibiting structures109may be configured to form vertical walls between neighboring waveguides104A,104B, and104C to inhibit the energy from one group of energy sources associated with a first waveguide from reaching the neighboring waveguide. For example, electromagnetic energy of any pixel102B associated with the center waveguide104B cannot reach waveguide104A because the energy-inhibiting structure109between these two waveguides may absorb this energy.

In an example,FIG.1Cshows a side view of a light field display150comprised of the display device108with a two-dimensional waveguide array104shown inFIG.1Bmounted above its active display area surface. This light field display projects light rays into propagation paths as shown inFIG.1B. In one embodiment, the display150may be used as a building block in a light field display assembly with a higher resolution than the individual light field display150with the use of tapered energy relays.

FIG.1Dshows an energy device101A, such as a display, with an active energy area105covered with an array of waveguides104, surrounded by a non-energetic bezel106. A magnified view of an area130shows the two waveguides104A at (X,Y)=(0,0) and104B at (X,Y)=(1,0) as defined by the U,V, and Z-axes140that are shown inFIG.1B, as well as the 4-D coordinates for the energy source associated with each waveguide. These energy source locations are located on the energy surface102and define the energy source plane120. For example, energy source location183is associated with (X,Y,U,V) coordinates (0,0,−2,−2), denoted by x0y0u−2v−2. The energy source location193, under the same relative location relative to waveguide104B as the location of energy source location183relative to waveguide104A, has the same (U,V) coordinate (−2,−2), with (X,Y,U,V) coordinate (1,0,−2,−2). Similarly, energy source location181at the center of waveguide104A, has (X,Y,U,V) coordinate (0,0,0,0), while energy source location191at the center of waveguide104B has (X,Y,U,V) coordinate (1,0,0,0). Some other 4D energy propagation path coordinates are shown inFIG.1D, including (X,Y,U,V)=(0,0,−1,0), (0,0,−2,0), (0,0,−3,0), and (1,0,0,0).

FIG.1Eshows an example in which two holographic objects122and124are projected by a light field display system comprised of five waveguides104A-E that define an energy directing surface101, wherein each waveguide projects light from a group of associated pixels102A-E, respectively. The holographic object122and124are created by the convergence of a multitude of light projection paths such as propagation path groups121and123, and are perceived by an observer151. The pixel plane120is defined by a seamless energy surface102. The light rays defined by chief rays123forming holographic object124include light from pixel171projected by waveguide104A, light from pixel172projected by waveguide104B, and light from pixel173projected by waveguide104C. The light rays defined by chief rays121converging at the in-screen holographic object122include light from pixel174projected by waveguide104C, light from pixel175projected by waveguide104D, and light from pixel176projected by waveguide104E. InFIG.1E, the light-inhibiting structures109forming vertical walls between neighboring waveguides104A-E prevent light generated by one group of pixels associated with a first waveguide from reaching a neighboring waveguide. For example, light from any pixel102C associated with the waveguide104C cannot reach waveguide104B or waveguide104D because the light-inhibiting structures109surrounding waveguide104C would block and absorb this stray light. WhileFIG.1Eillustrates an embodiment of a light field display system for projecting light, it is to be appreciated that the same principles apply for other types of holographic energy systems, such as light field capture system, light field display and capture system, holographic energy system of other electromagnetic energy or mechanical energy, bidirectional energy systems, or multiple energy domains.

FIG.2Aillustrates a schematic diagram of an embodiment of an energy directing system200. In an embodiment, the energy directing system may be wall mounted, projecting electromagnetic and/or mechanical energy such as light or sound waves outward to an audience in seats including seat88mounted on a graded floor89. In an embodiment, the energy directing system200may be similar to the energy directing systems discussed above with respect toFIGS.1A,1B, and1E. Specifically, the energy directing system200includes an energy directing surface201A formed by an array of energy waveguides (not shown). The energy directing surface201A may be configured according to the principles disclosed above with respect to the energy directing surface101defined by waveguides104as shown inFIGS.1A-1E, where each waveguide is associated with a group of energy source locations, and configured to direct energy from each of the associated energy source locations along an energy propagation path associated with a four-dimensional (4D) coordinate. This 4D coordinate is comprised of two spatial coordinates corresponding to a location of the waveguide through which the respective energy propagation path passes, and two angular coordinates determined at least by a location of the respective energy source location, the angular coordinates defining the direction of the respective propagation path.

In an embodiment, the holographic energy system200is configured to project bundles of light rays, including light ray bundle63from the top location33(x1, y1) of a light field display surface201A, and light ray bundle65from the bottom location35(x2, y2) of the light field display surface201A. The top location33and bottom location35are each associated with a spatial coordinate (X, Y), and the plurality of light propagation paths are defined according to the 4D coordinate system discussed above with respect toFIGS.1A-1E. Each light ray group may be centered on a center light energy propagation axis, or center light ray, which defines the general direction of propagation for the light rays leaving the display surface201A at a given location (X,Y) on that light field display surface201A. In the illustrated embodiment inFIG.1A, light ray group63is projected along the center light energy propagation axis53, and light ray group65is projected along center light energy propagation axis55. Each light energy propagation axis (also called a center energy propagation path) may represent a line of symmetry, since it is often coincident with the approximate midpoint of the angular range of light rays projected from the holographic energy system200at a particular (X,Y) location in the 4D coordinate system, both in the horizontal and vertical dimensions. For example, center light propagation axis53lies approximately along the midpoint of the angular range73for the light rays leaving the top location33of the energy directing surface201A, and center light propagation axis55lies close to the midpoint of the angular range75for the light ray group65projected from the bottom location35of the energy directing surface201A. The center light propagation axis, or center energy projection path, is often substantially aligned with the average energy vector for all the light rays leaving the display surface at a given position.

FIG.2Aillustrates an embodiment of the holographic energy system200with zero deflection angle, where the center light energy propagation axis of each group of rays projected from a light field display surface201A are parallel, and normal to that energy directing surface201A, as shown by the right angle45that the center light energy propagation axis55makes with the light field display surface. Note that with this embodiment, no light rays from the group of light rays63reach viewer seat88, which means that a viewer in this seat88cannot see light rays from the top location33of the light field display surface201A, and therefore seat88is not in the holographic viewing volume67of the display. Holographic objects that are formed by converging light propagation paths from the light field display in the holographic object volume66may be fully viewable to a viewer within the holographic viewing volume67. The boundary of the holographic viewing volume in the side view shown inFIG.2Amay be formed by the region in which at least one energy propagation path from a waveguide at an energy location33on the top of the display can intersect with at least one energy propagation path of a waveguide at an energy location35on the bottom off the display. InFIG.2A, at each location within the holographic viewing volume67of a light field display, at least one light propagation path from most of the waveguides on the light directing display surface can intersect. In general, a holographic viewing volume of the array of waveguides comprises a set of locations where at least one propagation path from each waveguide of the array of waveguides can intersect. A different holographic viewing volume including seat88may be effected by introducing a nonzero deflection angle to the group of light rays that are projected from waveguides at selected locations on the energy directing surface201A. This deflection in the energy propagation axis may be applied with different magnitude and direction at different points on the light field display surface201A in order to optimize the viewing volume for a given seating arrangement of viewers of the display, and result in a holographic viewing volume67which is closer to the light field display surface201A and thus closer to holographic objects projected from the light field display surface201A.

FIG.2Billustrates an embodiment of the holographic energy system250, in accordance with the principles disclosed in the present disclosure. The holographic energy system250is similar to the holographic energy system200illustrated inFIG.2Awith the modification of including at least one non-zero deflection angle in the holographic energy system250. The same numerals are assigned to the same components inFIGS.2A and2B. In an embodiment, the light field display surface201B may correspond to an alternate configuration of the energy directing surface101defined by an array of waveguides similar to waveguides104defined above inFIGS.1A-1E. In an embodiment, the holographic energy system250inFIG.2Bis configured to propagate energy to and/or from an audience which resides at a location that is primarily below a portion of the holographic energy system250, such as its midpoint height.

In an embodiment, this is accomplished by configuring the holographic energy system250so the light projection axes for at least some of the projected rays are tilted downward. For example, a light ray bundle13projected from the top location33of the light field display surface201B is defined by a light energy propagation axis63, forming a non-zero deflection angle43with a normal10to the light field display surface201B, which, in this embodiment, results in the light energy propagation axis63tilting down towards the audience members. In an embodiment, the light rays projected from the bottom location35of the light field display surface201B are defined by a light energy propagation axis65with a different direction than axis63, in this case normal45to the light field display surface201B. The angular spread23of the projected rays13about axis63projected from the top of the display represents a vertical field of view23, while the angular spread of the group of projected rays15about axis65projected from the bottom of the display represents a vertical field of view25, where the angular spread of23and25may be equal. In an embodiment, the light rays projected at positions located between the top location33and bottom location35of the light field display surface201B may have a deflection angle which varies between angle43at the top of the light field display surface201B, and the angle of zero (normal45to the display surface) at the bottom of the light field display surface201B. In an embodiment, this variation may be a gradient, such that the light rays projected from the middle height of the light field display surface201B and characterized by the light energy propagation axis4and are projected with a deflection angle44, which is a value between the deflection angle43at the top location33of the light field display surface201B and the deflection angle of zero (normal45) at the bottom location35of the light field display surface201B. A possible advantage of this gradient configuration is that the holographic viewing volume7for holographic objects projected from light field display surface201may be optimized for the anticipated seating arrangement, achieving improved performance and composite field-of-view for that set of viewers given the available angular ranges23,25of projected rays. Note that an added advantage is that the holographic viewing volume7is now closer to the light field display surface201B and the holographic object volume6with the nonzero deflection angles shown inFIG.2B, as compared to the increased separation of the holographic viewing volume67from the holographic object volume66with zero deflection angle shown inFIG.2A. In general, the deflection angles of waveguides in an array of waveguides may be configured such that the holographic viewing volume of the array of waveguides is closer to the energy directing surface than the holographic view volume of the array of waveguides if the deflection angles of the waveguides of array of waveguides were configured to be zero.

A deflection angle, whether it is constant or variable across the energy directing surface201B, may be implemented with configurations of the present disclosure for waveguides at the display surface, or with separate energy-deflecting elements placed close to the energy directing surface201B.

FIG.3Aillustrates an orthogonal view of an embodiment of a first subsystem300of an energy directing system, this first subsystem having zero deflection angle. In an embodiment, the holographic energy directing system300is operable to project holographic content along a normal to a light field display surface301A. The subsystem300may include waveguides302A and302B that are neighboring elements of a waveguide array345, which defines an energy directing surface301A that corresponds to the light field display surface201A inFIG.2A, and energy directing surface101defined by waveguide layer104shown inFIGS.1A-1E. The waveguide302A is configured to propagate energy along multiple propagation paths from the energy locations303on an energy surface340and through the waveguide302A, while waveguide302B is configured to propagate energy along multiple propagation paths from the energy locations305on the energy surface340through the waveguide302B. The angular direction of each energy propagation path is dependent at least in part on the position of the corresponding energy location. For example, energy from the energy location304that passes through the waveguide302A and is directed by the waveguide302A is shown as the shaded region311, which is the energy propagation path from energy location304, and is defined by energy propagation axis308. Similarly, energy from energy source location361at one edge of the energy source locations303is projected by the waveguide302A along an energy propagation path362, and energy from energy source location363at the opposite edge of the energy source locations303is projected along energy propagation path364. These energy projection paths362and364define the range of angles307for the group of propagation paths associated with waveguide302A. The energy propagation paths associated with waveguide302B are similar in behavior. The propagation path from energy location306that passes through the waveguide302B is shown as the shaded region312, which is the energy propagation path from energy location306, and is defined by the energy propagation axis310. The angular range309of propagation paths for waveguide302B is similar to the angular range307associated with waveguide302A. In an embodiment, the energy locations304and306are located at the approximate center of energy locations303and305associated with two different waveguides302A and302B, respectively. Additionally, the center energy locations304and306are aligned with the symmetrical center of the waveguides302A and302B, respectively. Configured as such, the propagation paths through waveguide302A and the corresponding energy locations303define an angular range307of the propagation paths associated with the waveguide302A, and the energy propagation axis308is a line of symmetry for these propagation paths. The propagation paths through waveguide302B and the corresponding energy locations305define an angular range309of the propagation paths in one dimension associated with the waveguide302B, and the energy propagation axis310is a line of symmetry for this group of propagation paths. The energy propagation axes308and310, also referred to as center energy propagation paths, are parallel to the normal of the energy directing surface301A, effecting a zero deflection angle with respect to energy directing surface301A. The configuration of the waveguides302A and302B and energy surface340in the holographic energy system300may be implemented to effect a zero deflection angle at desired locations. For example, the locations33,35shown inFIG.2Aand location35shown inFIG.2Bmay all have a zero deflection angle as discussed above, and the zero deflection angle at these locations may be implemented by having the holographic energy systems200and250include waveguides similar to waveguides302A,302B at these locations

In an embodiment, the energy propagated through the energy locations303may each fill a substantial portion of the aperture of waveguide302A, and may be blocked from entering the aperture of neighboring waveguide302B by one of the energy-inhibiting walls315. Similarly, the energy propagated from the energy locations305may each fill a substantial portion of the aperture of waveguide302B, and may be blocked from entering the aperture of neighboring waveguide302A by one of the energy-inhibiting walls315. Note that in this disclosure, most of the time the energy locations on energy surface340such as303and305are referred to as energy sources, but configurations are possible (e.g. light field sensing devices) in which energy propagation paths are incident on the waveguide and the energy locations on the waveguides are energy sensors. In an embodiment, a light field display which also records as well as projects light propagation paths may have groups of energy locations303and305, the groups of energy locations which either all emit or sense electromagnetic energy, or the groups of energy locations comprised of a combination of energy emitters and energy sensors which may be interleaved.

FIG.3Billustrates an orthogonal view of an embodiment of a second subsystem350of a holographic energy directing system, the second subsystem350having non-zero deflection angle. The subsystem350may include waveguides322A and322B that are neighboring elements of a waveguide array345, which defines an energy directing surface301B that may correspond to portions of the display surface201B inFIG.2B, or an alternate configuration of the energy directing surface101defined by waveguides104shown inFIGS.1A-1E. The waveguide322A is configured to propagate energy along propagation paths through the energy locations323on the energy surface340, while waveguide322B is configured to propagate energy through the energy locations325on the energy surface340. The angular direction of energy propagation path is dependent at least in part on the position of the corresponding energy location. The energy from the energy location324that passes through the waveguide322A and is directed by the waveguide322A is shown as the shaded region331, which is the energy propagation path from energy location324defined by the energy propagation axis328. Similarly, energy along propagation path332from the energy location326lies along energy propagation axis330. Energy from energy source location365at one edge of the energy source locations323is projected by the waveguide322A along an energy propagation path366, and energy from energy source location367at the opposite edge of the energy source locations323is projected along energy propagation path368. These energy propagation paths366and368define the range of angles327for the group of propagation paths associated with waveguide322A. The energy propagation paths associated with waveguide322B are similar. In an embodiment, the energy locations324and326are located at the approximate center of energy locations323and325, respectively. Configured as such, all the propagation paths passing through waveguide322A originating from the corresponding energy locations323define an angular range327, and the energy propagation axis328is a line of symmetry for these propagation paths. All the propagation paths through waveguide322B and originating from the corresponding energy locations325define an angular range329, and the energy propagation axis330is a line of symmetry for these propagation paths. The energy projection axes328and330are also known as center energy projection paths, and the angle338they make with the normal339to the energy directing surface301B is called the deflection angle. In contrast to the first subsystem300, the center energy location324of the group of energy locations323associated with the waveguide322A is offset from the symmetrical center of the waveguide322A. As a result, the energy propagation axis328is no longer perpendicular to the energy directing surface301B and forms a non-zero deflection angle338with respect to the normal339of the energy directing surface301B. In a similar way, the center energy location326of the group of energy locations325associated with the waveguide322B is offset from the symmetrical center of the waveguide322B, and the energy propagation axis330forms a non-zero deflection angle338with respect to the normal339of the energy directing surface301B. The configuration of the waveguides322A and322B and energy surface340in the holographic energy system350may be implemented to effect a non-zero deflection angle at a desired location. For example, the location33shown inFIG.2Bhas a non-zero deflection angle as discussed above, and the non-zero deflection angle at this location may be implemented by having the holographic energy system350include waveguides similar to waveguides322A,322B at this location or other locations where a non-zero deflection angle is desired.

As discussed above, in an embodiment, the light rays projected at positions located between the top location33and bottom location35of the display surface201B shown inFIG.2Bmay have a deflection angle which varies between angle43at the top of the display surface101, and the angle of zero (normal45to the display surface) at the bottom of the display surface101. In such an embodiment, the configuration of the waveguides302A,302B,322A, and322B may be incorporated to effect the desired variations of the deflection angles. For example, in an embodiment, a holographic energy directing system may include a first deflection angle of zero effected by a waveguide similar to the waveguide302A or302B and a second deflection angle that is non-zero effected by a waveguide similar to the waveguide322A or322B. In another example, a holographic energy directing system may include a first non-zero deflection angle effected by a waveguide similar to the waveguide302A or302B and a second non-zero deflection angle effected by a waveguide similar to the waveguide322A or322B where the first and second non-zero deflection angle may be the same or different. In another example, in an embodiment, a holographic energy system may include an array of energy waveguides302A,302B,322A, or322B comprising waveguides each having an energy propagation axis that defines a deflection angle relative to the normal of the energy directing surface301B, the deflection angle of the waveguides being different from that of the other waveguides in the array of energy waveguides345.

As discussed above, a gradient of deflection angles may be desired in some embodiments. To effect a desired gradient of deflection angles, an array of energy waveguides, such as wave guides302A,302B,322A, or322B, may be configured such that the deflection angle of each immediate subsequent waveguide in a first direction may be configured to be different than the deflection angle of each immediate preceding waveguide. In an embodiment, the deflection angle of each immediate subsequent waveguide in a first direction is greater than the deflection angle of each immediate preceding waveguide in the first direction. In another embodiment, the deflection angle of each immediate subsequent waveguide in a first direction may be configured to be less than the deflection angle of each immediate preceding waveguide in the first direction. In still another embodiment, the deflection angle of two adjacent waveguides can vary substantially. In an embodiment, the gradient of deflection angles may be interrupted at one or more desired locations by a discontinuity of deflection angle changes along a first direction. In an embodiment, the energy propagated through the energy locations323may each fill a substantial portion of the aperture of waveguide322A, and may be blocked from entering the aperture of neighboring waveguide322B by one of the energy-inhibiting walls335. Similarly, the energy propagated through the energy locations325may each fill a substantial portion of the aperture of waveguide322B, and may be blocked from entering the aperture of neighboring waveguide322A by one of the energy-inhibiting walls335.

FIG.3Cillustrates an embodiment of asymmetrically constructed energy waveguides that may be incorporated into an energy directing system, like system250, for effecting a non-zero deflection angle. Waveguides342A and342B are neighboring elements of an energy waveguide array345and define an energy directing surface301C. In an embodiment, energy directing surface301C is a light field display surface. Energy directing surface301C may correspond to portions of the display surface201B inFIG.2B, or an alternate configuration of the energy directing surface101shown inFIGS.1A-1E. The energy waveguide342A directs energy through energy locations343on energy s surface340, while waveguide342B directs energy through energy source locations345on energy surface340.

The energy from the energy location344that approaches the waveguide342A is represented by the shaded region388A, centered on axis348A, and this energy is redirected by the waveguide342A into the propagation path388B, which is the shaded region that leaves the waveguide342A centered on axis348B. Similarly, energy from energy location346that approaches the waveguide342B is represented by the shaded region398A, centered on axis399A, and this energy is redirected by the waveguide342B into the propagation path398B, which is the shaded region that leaves waveguide342B, centered on axis399B. In a similar way, energy from energy source location371at one edge of the energy source locations343is propagated towards the waveguide342A along axis372A, is refracted within the waveguide along axis372B, and leaves the waveguide342A along axis372C. Energy from energy source location373at the opposite edge of the energy source locations343is propagated along axis374A toward waveguide342A, is refracted within the waveguide along axis374B, and exits the waveguide along axis374C. These energy propagation paths372C and374C define the range of angles347for the group of all propagation paths associated with waveguide342A. The energy projection paths associated with waveguide342B are similar. Note that in contrast toFIG.3B, the center energy source location344of the group of energy source locations343associated with the waveguide342A is directly underneath the center of the waveguide342A, and the surface of the waveguide near light field display surface301C is asymmetric. As a result, the energy propagation axis348A for the energy from source344is refracted by the waveguide342A into energy propagation axis348B, which is roughly the center of the angular range347of the group of energy propagation paths originating from all the energy source locations343and passing through the waveguide342A. This means that from the discussion above,348B is the energy propagation axis for the energy projected by waveguide342A, and this energy propagation axis348B is not perpendicular to the light field display surface301C, making a non-zero angle338with respect to the normal339of the light field display surface. Similarly,399B is the energy propagation axis for the energy projected by waveguide342B, as it lies substantially near the center of the angular range349for all the projection energy paths from the energy source locations345propagated by the waveguide342B, and this energy propagation axis399B is not perpendicular to the energy directing surface301C, making a non-zero angle338with respect to the normal339of the energy directing surface. Energy from locations343associated with waveguide342A may be blocked by one of the energy-inhibiting structures355form reaching the aperture of the neighboring waveguide342B and vice versa.

WhileFIGS.3B and3Cshow embodiments of waveguides for effecting non-zero deflection angles, other embodiments are also possible. For example, in an embodiment, the waveguides may be tilted at an angle relative to a normal of the energy surface340. Other examples may include waveguides that contain sloped sections or facets, contain multiple elements, or otherwise are modified from the configurations shown inFIGS.3B and3Cin order to direct energy at a non-zero deflection angle relative to the display surface. The waveguides may be configured for an arrangement of energy locations which is distributed about the center of each waveguide or offset from the center of each waveguide. These waveguide solutions may be combined with other optical elements, including layers of glass with varying indices of refraction, mirrored layers, thin films, diffraction gratings, holographic optical elements, metamaterial layers, or the like in order to achieve a non-zero deflection angle.

FIGS.3B and3Cshow example embodiments with a deflection angle built into the surface of an energy-directing device. In contrast,FIG.4Aillustrates an orthogonal view of an embodiment of a holographic energy system with a deflection angle achieved using a layer of optic elements placed over the energy directing surface401, such as a light field display surface, to deflect light rays once they leave the energy directing surface401. The energy leaving energy directing surface401at the location405are spread over the angular range406, including the propagation paths411,412, and413. The energy directing surface401may have zero deflection angle, and constructed in a similar manner to the energy-directing surfaces301A inFIG.3A,201AinFIG.2A, or101inFIGS.1A-1Ediscussed above. For example, a waveguide such as302A or302B shown inFIG.3Amay be located at the location405of the energy directing surface401to effect a zero deflection, whereby the energy propagation axis412is parallel with a normal to the display surface401. An optical element may comprise a layer of refractive optics402to refract the received energy propagation paths from the energy directing surface401, changing the direction of many incident energy propagation paths. In the example illustrated inFIG.4A, propagation path411is deflected into propagation path431, propagation path412is deflected into propagation path432, and propagation path413is deflected along propagation path433. The close-up views421,422, and423of the optical element402show energy propagation paths that are bent twice as they pass through the higher refractive index of the optical element402, which may be a refractive element, at first surface441A, and then again at second surface441B. The paths411,412, and413are first bent toward the normal of the first surface441A, as they travel into the higher-index material of the refractive material402at surface441A, and then away from the normal of the interface as they leave the higher-index material of the refractive optics402at second surface441B. The result is that the angular range406of the energy propagations paths leaving the energy directing surface401, which was symmetric around the energy output axis412, has been mapped and transformed to angular range426, which has an energy propagation axis432which is the approximate axis of symmetry for the plurality of deflected propagation paths and is tilted at an angle438relative to the normal439to the energy directing surface401. In other words, the energy rays have all been deflected by a non-zero deflection angle, so that the holographic content propagates in a generally tilted direction relative to the normal to the display surface. Note that while this example illustrated inFIG.4Ashows how rays of light from an energy projecting surface may be deflected by refractive optics using prisms with varying properties, it is possible to use layers of glass with varying indices of refraction, mirrored layers, thin films, diffraction gratings, diffractive optics, holographic optical elements, single lenses, multi-element lenses, liquid lenses, deformable surfaces, metamaterial surfaces, or the like. The layer of optics may be optimized for a particular viewing geometry and coupled to a light field display surface allowing viewing volume customization with relatively lesser expense than tailoring the deflection angle of waveguides across the display surface.

FIG.4Billustrates the same optical system shown inFIG.4A, showing the deflection angle ϑ439that the energy propagation axis432makes with the normal to the energy directing surface401. The group of propagation paths451from location405on the display surface401are grouped around the input optical axis412as they approach the optical element402, and they are redirected to group452centered on optical axis432as they leave the optical element402. The angular range406of input propagation paths451may be substantially the same as the angular range426of the output propagation paths452, or they may differ, depending on the implementation.

The example ofFIG.4Bshows a planar layer of optical elements used to achieve a non-zero deflection angle of energy from a light field display across its surface. In some embodiments, the light field display is configured to propagate more than one type of energy. For example, the light field display may project two types of energy, such as acoustic energy and electromagnetic energy. In some embodiments, the acoustic energy is directed from multiple locations on one or more surfaces that are disposed a short distance from the display surface401, and these locations direct the acoustic energy into the holographic object volume. In other embodiments, the display surface401itself contains both acoustic energy transducers as well as electromagnetic waveguides, projecting both electromagnetic energy and acoustic energy. The acoustic energy may be projected from transducer or acoustic waveguide locations between the electromagnetic waveguide elements of the waveguide array (e.g.345inFIGS.3A,3B, and3C) on the display surface, and may help form structures that inhibit energy (e.g.315inFIG.3A or355inFIG.3C) from being transported from one electromagnetic waveguide element to another.

In an embodiment, a spatially separated array of transducers that project ultrasonic acoustic energy can be configured to create three-dimensional haptic shapes and surfaces in mid-air. Phase delays and amplitude variations across the array can assist in directing the ultrasound from multiple sources to interfere at one or more specific haptic locations which may provide the sensation of touch. These haptic locations may coincide with projected holographic objects. Generally, acoustic waveguides or transducers placed on a planar surface, whether the surface is apart from the display surface or integrated into the display surface, tend to project the acoustic energy outward and normal to that surface. Ideally, an array of deflection angles for those sound-producing locations would enable the sound to be directed towards convergence points from multiple locations on the planar surface, which can enable volumetric tactile surfaces to form.

In an embodiment, deflection angles for both electromagnetic and acoustic energy may be achieved with metamaterials. These metamaterials are primarily two-dimensional patterned surfaces called metasurfaces with engineered subwavelength cells or structures that may be used as materials that redirect energy wave fronts. This deflection of an input beam of energy may be done by arranging for graded phase shifts along the profile of the metamaterials. One conventional approach of metasurface design is to effect local phase modulation, which dictates the behavior of outgoing waves according to a generalized Snell's Law (GSL). This has been used in optics to design structures such as lenses and beam splitters. In acoustics, the phase shifts within metasurfaces have been used to manipulate wave fronts and to absorb sounds.

Such approaches have limitations in efficiency of scattering, which may be overcome by using metamaterials that are known as bi-anisotropic materials. In bi-isotropic electromagnetic media, the electric and magnetic fields are coupled by intrinsic constants of the media. If the coupling constants depend on the direction within the media, the media is referred to as bi-anisotropic. A similar phenomena occurs in acoustics for inhomogeneous elastic materials that display Willis coupling, in which stain is coupled to momentum and stress is coupled to velocity in the frequency domain.

A bi-anisotropic electromagnetic response can be implemented by bi-anisotropic metasurfaces, where the scattered electromagnetic fields are different depending on the direction of illumination. For electromagnetic metasurfaces, typical solutions are based on cascaded impedance layers. These structures have been experimentally verified to deflect light with a high efficiency, focus light, and achieve other optical functionalities.

FIG.4Cillustrates a holographic energy system similar to that shown inFIG.4B, but with one or more optical metasurfaces404taking the place of the optical element402shown inFIG.4B. The same numerals are assigned to the same components inFIGS.4B and4C. In the example shown inFIG.4C, one or more layers of metasurfaces404are used to achieve the deflection angle ϑ438. The metamaterials may achieve local phase modulation according to a generalized Snell's law, or have a higher efficiency for deflecting a beam of light by being constructed of structures made of bi-isotropic materials or bi-anisotropic materials. If individual metasurface regions are individually addressable and configurable, the deflection angle ϑ438may be programmed across a range of angles at each of these regions.

In acoustics, recently it has been shown that using bi-anisotropic resonators achieved with specific resonator geometry dimensions, an incident plane sound wave may be redirected by large angles of greater than 60 deg with a power efficiency of greater than 90% [1]. Such a technology is a candidate for generating a gradient deflection angle for sound wave fronts across a surface containing an array of sound generators such as transducers. Such a gradient deflection angle may be used to assist the focus of multiple ultrasonic wave fronts to a common point of interference, achieving a volumetric tactile surface, which may provide the sensation of touch as described above.

FIG.4Dis an example of a system which deflects an incoming sound wave471into an output sound wave473with a substantial deflection angle ϑ476.FIG.4Drepresents a deflection element with a single deflection location configured to receive mechanical energy from a single energy source location, and deflect the received mechanical energy along deflected propagation paths. The sound wave is produced by an acoustic waveguide or an acoustic transducer located at position403on a surface of sound energy sources481. The surface481may be a surface disposed next to a light field display surface comprised of many acoustic waveguides or transducers, or the surface481may be a dual-energy light field display surface comprised of both electromagnetic waveguides as well as acoustic energy transducers, wherein the electromagnetic waveguides and the acoustic energy transducers may be interleaved. Sound wave471is produced along the energy axis472, normal to the surface481, and parallel with the normal475, and is deflected by one or more metasurface layers480into sound wave473along axis474. The angle ϑ476between the energy propagation axis474of the deflected sound wave and the normal439to the surface of sound sources481is the deflection angle. If individual metasurface regions are individually addressable and configurable, the deflection angle ϑ476may be programmed across a range of angles at each of these regions. The one or more metasurface layers480may be made of a 2D patterned surface of arrangements of sub-wavelength cells, or acoustic cells that are made from bi-anisotropic metamaterials.

A gradually changing deflection angle, called a deflection gradient, may be used across a display surface to increase the field of view for a specific viewing volume, or bring the viewing volume closer to the display surface.FIG.5Aillustrates a top view of an embodiment of an electromagnetic energy directing system, which may be any energy directing system discussed in the present disclosure, including a light field display. In an embodiment, the energy directing system ofFIG.5Aincludes an energy projecting surface501with a 60-degree angular energy propagation range at various surface locations of the energy projecting surface501and no deflection angle. In an embodiment, the energy surface501may incorporate the configurations of energy directing surfaces similar to101ofFIGS.1B and1E, the light field display surface201A inFIG.2A, and surface301A inFIG.3A. In an embodiment, the groups of energy propagation paths of the surface501are directed normal to the surface501, effecting zero deflection angles. Each group of energy propagation paths with energy propagation axes521-525is distributed over a 60-degree angular range514-518, respectively. The resulting holographic viewing volume504, where energy from all different surface locations overlap, and where holographic objects located everywhere in the holographic object volume503can be seen, has the same 60-degree field-of-view519. Note that the holographic viewing volume504may not be closer than roughly the width of the display for this geometry. In this configuration, the holographic object volume is quite large geometrically, but it may be limited by the maximum projection distance from the light field display surface501.

FIG.5Bshows the same display surface501as that shown inFIG.5Abut with gradient deflection angles achieved across the display surface that is realized with an optical deflection layer571similar to layer402shown inFIGS.4A-4Bplaced directly in front of the display surface501, allowing the holographic viewing volume508to be positioned much closer to the light field display surface501. InFIG.5B, energy propagation groups581-585each produced symmetrically about an energy propagation axis parallel to the normal509of the display surface501with zero deflection angle are almost all deflected by the optical deflection layer571by deflection angles531-535which range from +30 degrees on the left side of the light field display surface to −30 degrees on the right side. Energy propagation paths581produced symmetrically about an energy propagation axis normal509to the display surface501are all deflected by an angle531of 30 degrees by the deflection layer571into deflected energy propagation paths centered on axis551, toward the center holographic viewing volume508. Similarly, energy rays582are deflected by 15 degrees into energy propagation axis552; energy rays583are undeflected and continue along energy propagation axis553, energy rays584are deflected by −15 degrees into energy propagation axis554, and energy rays585are deflected by −30 degrees into energy propagation axis555, in such a way that each of the deflected propagation axes551-555point close to the middle of the holographic viewing volume508, independent of location on the display surface. At intermediate points on the light field display surface501, the deflection angle may be an interpolated value of the deflection angles just given. In other words, the deflection angle may continuously change across position on the energy directing surface, or it may be grouped in regions and have borders of discontinuity. The deflection angle is shown to change in only one dimensions inFIG.5B, but in general the deflection angle may be any continuous or non-continuous function of position across the energy directing surface. In the configuration shown inFIG.5B, the angular spread before and after deflection for energy propagation paths581-585is an angle541-555of 60 degrees.

The result is that bundles of energy propagation paths centered on energy propagation axes are directed toward the holographic viewing volume508from each portion of the light field display surface, resulting in a field-of-view that can be as much as angle529equal to about 120 degrees, and a holographic viewing volume508which may have the proximity to the display surface501of a fraction of the horizontal width of the display surface. Notice that light rays leaving the edges of the display surface may not be directed into a horizontal area that is wider than the width of the display surface, resulting in the avoidance of energy projected away from the holographic viewing volume508.

Examining the differences between the embodiments illustrated inFIG.5AandFIG.5B, we see that a gradient deflection angle may be used to increase the field-of-view of the viewing volume for viewers, decrease the separation between the energy projecting surface and the viewing volume, and thus increase the proximity of holographic objects to the viewing audience. The holographic object volume is smaller inFIG.5Bthan inFIG.5A, but it can be customized to accommodate the maximum projected distance for the light field display. The design parameters for the display may take this into account, balancing mutually competing requirements of projection distance, resolution, and field-of-view.

FIG.5Cis the same holographic display system shown inFIG.5B, except that the layer of deflection optics571inFIG.5Bhas been replaced with one or more layers575of gradient metasurfaces that produce the same deflection angles. Otherwise the same numerals are assigned to the same components inFIGS.5B and5C. The gradient metasurface layer575may deflect light rays by an angle which is tunable, similar to the behavior of the metamaterial surface404shown inFIG.4C. The metasurface layer575may change the direction of the rays of light by achieving local phase modulation according to a generalized Snell's law, or have a higher efficiency for deflecting a beam of light by being constructed of structures made of bi-isotropic metamaterials or bi-anisotropic metamaterials.

As shown inFIGS.3B and3C, a deflection angle on a light field display may be achieved using an array of waveguides, wherein each waveguide is configured to propagate energy through multiple energy locations and produce a group of energy projection paths that are centered on an energy propagation axis of symmetry that is not normal to the plane of the waveguides.FIG.5Dillustrates a top view of an embodiment of an energy projection surface520configured to have variable non-zero deflection angles as a function of location on the energy projection surface, allowing the holographic viewing volume to be positioned much closer to the energy projection surface than if no deflection angle was used. The same numerals are assigned to the same components inFIGS.5C and5D. The holographic system ofFIG.5Dis almost identical to that shown inFIG.5C, except that the gradient deflection angle inFIG.5Dis achieved with the waveguides that form the display surface520, rather than a surface of metamaterials509disposed in front of the display surface501. The energy directing display surface520may be comprised of waveguides similar to322A and322B forming the energy directing surface301B shown inFIG.3B, waveguides similar to342A and342B forming energy directing surface301C shown inFIG.3C, some combination of these waveguides with various deflection angles, or some other types of waveguides.

There are additional embodiments of a light field display surface that may be used to increase the field of view and the proximity of projected holographic objects to the viewing volume, or in other words, increase the immersive experience for the viewer. An embodiment which contains a curved surface which surrounds the front of the audience in an arc is one embodiment. In other embodiments, one or more display surfaces may be placed at an angle to a central display surface. This allows the resulting aggregate display surface to surround the viewing volume, to bring holographic objects closer to that volume, and achieve an increased field-of-view. Using flat surfaces angled with respect to one another allows multiple identical panels to be used in a configuration so that the full display surface may be constructed in a modular fashion and be optimized quickly for specific viewing volume requirements.

The concept of a deflection angle as a function of position on the energy-directing surface may be implemented to the propagation of mechanical energy. A spatially separated array of locations that project acoustic mechanical energy may be configured to create three-dimensional haptic shapes and surfaces in mid-air. In some embodiments, phase delays and amplitude variations across the array can assist in creating these haptic shapes. In some applications, it may be beneficial to be able to tilt the sound emitted from the sound energy locations at an angle toward a tactile volume.FIG.5Eshows a top-down orthogonal view of an acoustic mechanical energy directing device comprised of three acoustic mechanical energy sources561A,561F, and561K on an acoustic energy layer561producing sound waves56A,56F, and56K, respectively, where the sound waves are received and deflected into sound waves57A,57F, and5K, respectively, by a static acoustic deflection layer592toward a tactile volume558. The acoustic energy sources561A,561F, and561K may be acoustic transducers that are similar to the acoustic energy source located at position403shown inFIG.4D. The static acoustic deflection layer592may be a metasurface made of metamaterials, similar to480discussed in reference toFIG.4D, and may assist in directing sound wave fronts toward an area where tactile surfaces are generated. In an embodiment, the acoustic energy directing device shown inFIG.5Emay be used together with a light field display to generate tactile surfaces which are coincident with holographic objects. In another embodiment, the acoustic energy directing device shown inFIG.5Eis transparent to light and may be placed over the energy directing surface of a light field display to create a dual energy directing device which displays holographic objects and generates tactile surfaces.

It is possible to construct a reconfigurable four-dimensional (4D) acoustic energy field from an array of reconfigurable individual acoustic energy deflecting devices placed over an array of individual acoustic energy sources.FIG.5Fshows an orthogonal view of a 4D acoustic energy directing system comprised of a deflection element providing an array562of reconfigurable acoustic energy deflecting locations562A-D placed over an array561of acoustic energy sources561A-D. The reconfigurable acoustic energy deflecting locations562A-D may be provided by a deflection element comprised of individual devices, or individual sites on one or more substrates, where each substrate contains multiple sites. The energy deflecting locations562A-D may be metasurfaces made of metamaterials, described above, and may be similar to those shown on layer480ofFIG.4D. Energy source locations561A-D project sound waves56A-D, respectively, which are each received and deflected by acoustic energy deflecting locations562A-D into sound waves57A-D with a deflected propagation direction. Each acoustic energy deflecting location562A-D is associated with at least one acoustic energy propagation path with a two-dimensional angular coordinate (u, v), and a two-dimensional coordinate (x, y) that determines position on the energy-directing surface501A, Together these coordinates form a four-dimensional coordinate (x, y, u, v) for each acoustic energy propagation path. InFIG.5F, the positional coordinates for the sound propagation paths57A-D are (x, y)=(0,0), (1,0), (2,0), and (3,0), and the respective angular coordinates are (u,v)=(u0,v0), (u1,v1), (u2,v2), and (u3,v3), resulting in 4D coordinates=(0,0,u0,v0), (1,0,u1,v1), (2,0,u2,v2), and (3,0,u3,v3), respectively. In the embodiment shown inFIG.5F, each acoustic energy deflecting location562A-D deflects the energy from only one sound energy location561A-D, but it is possible for each sound deflecting location to direct multiple sound sources into multiple propagation paths, each with a (u, v) coordinate. Such an energy directing system may look very similar to a 4D light field display system shown inFIGS.1B and1E.

FIG.5Gshows how the 4D acoustic energy directing system shown inFIG.5Fmay be used to generate a tactile interface. InFIG.5G, the multiple sources of acoustic energy56D,56H, and56L are produced by energy source locations561D,561H, and561L on plane561, and deflected by acoustic energy deflecting locations562D,562H, and562L on plane562into sound waves57D,57H, and57L. These sound waves57D,57H, and57L converge, producing a tactile interface591. In one embodiment, the sound waves are ultrasonic waves, and upon interfering produce a much lower-frequency wave which may produce a tactile sensation. The energy directing system shown inFIG.5Gmay be disposed close to the plane of a light field display surface, but completely offset from it spatially to avoid blocking the light from the display surface. The acoustic energy source plane561and the acoustic deflection plane562may be transparent to light from a light field display. The tactile surface591may be coincident with a holographic object projected by a light field display. The acoustic energy deflecting locations562D,562H, and562L on layer592may each deflect the sound waves by achieving local phase modulation according to a generalized Snell's law, or have a higher efficiency for deflecting a beam of sound by being constructed of structures made of bi-isotropic acoustic metamaterials or bi-anisotropic acoustic metamaterials.

FIG.5Hillustrates how a dual energy directing surface595may be constructed by interleaving energy waveguides with acoustic energy deflecting locations. The top view to the left inFIG.5Hshows how energy waveguides3020are interleaved with acoustic energy deflecting locations5620on the dual energy directing surface595. While this example shows that these elements have equal size, there are many more regular and irregular arrangements of an interleaved pattern where the acoustic deflecting locations may have a smaller or larger size than the waveguides. In this example, a row of elements589may be comprised of waveguides302A,302B, and302C which may the waveguides302A and302B shown inFIG.3A, and the row may also contain the acoustic beam deflecting locations562X and562Y, which may be similar to562D and562H shown inFIG.5G. The side view to the right inFIG.5Hshows how waveguides302A-C direct the electromagnetic energy from one or more electromagnetic energy source location groups303A-C, where waveguide302A directs energy along energy propagation path508A, waveguide302B directs energy along propagation paths580B, and waveguide302C directs energy along energy propagation path580C. Energy-inhibiting structures315A may be configured between neighboring waveguides302B and302C to inhibit the energy from one group of energy sources associated with a first waveguide from reaching the neighboring waveguide. Energy inhibiting structures315A may be similar to315inFIG.3A. Acoustic energy directing sites562X-Y receive mechanical energy from acoustic or mechanical energy source locations561X-Y, respectively, and deflect this energy into sound waves57X and57Y, respectively. Energy-inhibiting structures315B may be configured between waveguides such as302B and acoustic energy-deflecting sites such as562X to confine the energy of the waveguide from interfering with the acoustic energy-deflecting site, and vice-versa. The dual energy source surface594contains two types of energy source locations, and this energy is directed into energy propagation paths by waveguides and acoustic energy deflection locations on the dual energy directing surface595. While the embodiment inFIG.5Hshows one arrangement of different waveguides and acoustic beam deflection devices, there are many others which would allow an interleaved solution which projects two different 4D energy fields.

FIG.5Ishows how a dual energy directing surface595may be used to simultaneously project the surface592of a holographic object and a tactile surface591. The energy directing surface595is shown in detail inFIG.5H. The plurality of light waveguides3020as shown inFIG.5Hdistributed across the dual energy surface595comprises a 4D light field, projecting light rays580, a portion of which converge to form a holographic surface592. Holographic objects such as592produced in the holographic object volume may be viewed in the holographic viewing volume. The plurality of acoustic energy deflecting locations5620shown inFIG.5Hdistributed across the dual energy surface595and interleaved with the waveguides3020comprises a 4D acoustic energy field, and deflects a plurality of acoustic energy beams57so that they converge to form a tactile surface591, which may be coincident with the holographic surface592. The light projected light rays580are generated in a similar way to the light rays580A-C shown in the side view of595inFIG.5H, and the acoustic energy propagation paths57are generated in a similar way to the acoustic energy beams57X-Y shown inFIG.5H.

FIG.6illustrates an orthogonal view of an embodiment of a holographic display comprising a central wall-mounted light field display surface601directly in front of a viewing volume, and a side light field display surface602angled at 45 degrees relative to the central panel and tilted toward the viewing volume, where both panels feature gradient deflection angles across their surfaces. The holographic content is projected from the central panel in a direction that is generally toward the viewing volume. Light ray group631is projected along the energy propagation axis611near the top of the display, ray group632is projected along energy propagation axis612at the middle of the display, and light group633is projected along energy propagation axis613A near the bottom of the display. Each of these energy projection axes is at an angle (621,622, and623A) from the normal608to the display surface601. Similarly, the holographic content is projected from the lower light field display surface602also in the general direction of the viewing volume, at a variable angle relative to a normal609of the display surface602. The light ray group633is projected along axis613B near the top of display602at display surface position603, along energy propagation axis614in the middle of display602, and along energy propagation axis615at the bottom of the display602. Each of these directions of propagation is also at an angle (623B,624,625) from the normal609to the display surface602. The result is that the viewing volume may include all the audience members shown, including the little girl605and the two adults606, and the head of the holographic stegosaurus607may be projected further out and closer to the audience member605, increasing the realism and the immersivity of the scene.

FIG.7illustrates a top view of an embodiment of a light field display surface comprising a central flat surface701, and two light field display surfaces702,703on either side of the central surface701, angled inward toward the viewing volume705with respect to the central surface701. A gradient deflection angle, realized as the multiple energy projection axes710at an angle which is not normal to the display surface, allows holographic content to be projected from each position on each display surface along the energy projection axes710, in a direction that is approximately toward the center of the ideal viewing volume705. This display surface covers full field of vision for viewers located in the ideal viewing volume705who are facing the central display surface701. Holographic objects can be seen for viewers that may be further away in the extended viewing volume706. Energy directing surfaces can be used in configurations besides those shown inFIG.7. For example, it is possible to have energy projection surfaces with multiple facets, a curved or wedged surface, or a combination of these.

An energy directing surface with only a central planar surface has a planar proximity between a holographic object and the viewing volume, a planar field of view, and a planar threshold separation between the central display surface and the viewing volume. Adding one or more side energy-directing surfaces angled towards the viewer may increase the proximity between the display surface and a holographic object relative to the planar proximity, may increase the field of view relative to the planar field of view, or may decrease the separation between the display surface and the viewing volume relative to the planar separation. Further angling the side surfaces towards the viewer may further increase the proximity, increase the field of view, or decrease the separation. In other words, the angled placement of the side surfaces may increase the immersive experience for viewers.

The embodiment ofFIG.7may be extended to other energy domains. InFIG.7, the holographic object volume is the volume over which light energy rays converge to form light energy surfaces, the viewing volume is the volume for receiving light energy leaving the light energy surfaces, and the field of view is the angular range of energy projection paths that are received within the energy receiving volume.