Patent Description:
The present disclosure relates generally to image display, and more particularly to apparatus and method for displaying holographic imagery.

A hologram is produced by illuminating a holographic medium (e.g., a holographic panel or print) that encodes a light field emanating from a scene as an interference pattern. When the holographic medium is suitably illuminated with a light source, the interference pattern diffracts the light into a three-dimensional (3D) hologram image that exhibits visual depth cue such as parallax and perspective. In addition, a hologram may include multiple 3D hologram images (e.g., a multi-channel hologram), wherein each image corresponds to a respective position of an observer or corresponds to an incident angle of a light source. Recently there is growing interest to use holographic media to create 3D recordings of scenes that can be seen without the aid of special glasses or other intermediate optics. However, current hologram technology may have a limited depth of field (DOF) due to various factors, such as the coherence length of a laser and the quality of the holographic panel, leading to limited holographic element resolution of the holographic panel.

According to the present invention, there is provided a hologram image apparatus according to Claim <NUM> and a method of forming a composite hologram according to Claim <NUM>. Preferred embodiments of the invention are defined in Claims <NUM> to <NUM> and Claims <NUM> to <NUM>. In the following description, embodiments will be described. These embodiments fall within the scope of the present invention only if they are in accordance with Claim <NUM> or <NUM>.

As set forth above, while there is growing interest in using holographic media (e.g., holographic panels or prints) to create 3D recordings of scenes, current hologram technology may have a limited depth of field (DOF), leading to limited holographic element resolution of the holographic media. As such, any 3D imagery created on the holographic panel appears the clearest, the most in-focus, as the 3D imagery approaches the plane of the surface of the holographic panel, and the imagery that is farther away from the surface plane becomes blurry and out of focus. One approach to ensure the entire 3D imagery is crisp and in-focus may be to bind the content within a limited depth field. However, it is now recognized that this approach does not achieve the effect of depth needed to create deep, immersive scenes.

With this in mind, present embodiments are directed to an apparatus and method for producing high DOF and in-focus 3D holographic images. As discussed in greater detail below, in accordance with present embodiments, a composite hologram image is formed using a plurality of substantially transparent holographic panels each encoded with a portion of the composite hologram image. The plurality of holographic panels are placed adjacent to one another, such that a gap exists between adjacent holographic panels and respective DOFs of adjacent holographic panels overlap with one another. The hologram images of the plurality of holographic panels together form the composite hologram image. By keeping the hologram of each holographic panel within its respective DOF and by stacking the holographic panels adjacent to one another, the DOF of the composite hologram image is tunable without altering the holographic element resolution. For example, the DOF of the composite hologram image may increase with the number of holographic panels. As such, the overall depth effect may far exceed that possible from a single holographic panel, and a composite hologram image showing an in-focus, deep, and immersive scene may be achieved.

Turning to the drawings, <FIG> is a perspective view of a holographic image apparatus not according to the invention. In the illustrated configuration, the holographic image apparatus <NUM> includes a holographic panel or print <NUM> encoded with holographic 3D content <NUM> that has an in-focus DOF <NUM>. The holographic panel <NUM> may include substantially transparent material (e.g., transparent with respect to visible light) such as glass (as opposed to an opaque material). The holographic panel <NUM> may include tinted material (e.g., having about <NUM>% to about <NUM>%, such as about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>% light transparency). The holographic image apparatus <NUM> also includes one or more light sources <NUM> configured to illuminate the holographic panel <NUM> from one or more incident angles (e.g., angles with respect to the surface normal of the holographic panel <NUM>). The one or more light sources <NUM> may be dedicated light sources or may be integrated light sources in the surrounding where the holographic panel <NUM> is disposed, such as a common lighting system in a space (e.g., a display room, a stage).

When the holographic panel <NUM> is illuminated by the one or more light sources <NUM>, the produced hologram image (e.g., the holographic 3D content <NUM>) is in-focus (e.g., clear and crisp) within the DOF <NUM>. The holographic panel <NUM> may be a single-channel hologram or may be a multi-channel hologram, such that different frames of images are revealed when the holographic panel <NUM> is illuminated from different incident angles of the one or more light sources <NUM> or when observers view the holographic panel <NUM> from different viewing angles. The DOF <NUM> may be about <NUM> millimeters (mm) from a surface <NUM> of the holographic panel <NUM> (e.g., a distance <NUM> is about <NUM>) and/or about <NUM> above and below the holographic panel <NUM> (e.g., a distance <NUM> is about <NUM>). As set forth above, the DOF of the holographic panel <NUM> is limited by the holographic element resolution, which may be difficult to improve. In accordance with present embodiments, the DOF of a hologram may be improved without altering the holographic element resolution. In particular, it is now recognized that in- focus, high depth of field 3D imagery may be achieved using a plurality of holographic panels to form a composite hologram image as discussed below.

<FIG> is a perspective view of an embodiment of the holographic image apparatus <NUM> that includes a stack of holographic panels or prints <NUM> (e.g., a plurality of holographic panels) to extend the DOF. In the illustrated embodiment, the holographic image apparatus <NUM> includes the one or more light sources <NUM> and a plurality of the holographic panels <NUM> stacked or arranged adjacent to one another with a gap <NUM> between adjacent holographic panels <NUM>. The gap <NUM> may be considered to represent a distance from the center of one holographic panel <NUM> to the center of an adjacent holographic panel <NUM> in the surface normal or out of plane direction. As discussed later, the gap <NUM> may be a constant value or may change (e.g., increase or decrease) for different pairs of adjacent holographic panels <NUM>.

Although in the illustrated embodiment only three holographic panels <NUM> are shown, the stack of holographic panels <NUM> may include any suitable number of holographic panels <NUM>. In the illustrated embodiment, the stack of holographic panels <NUM> are arranged such that surface normals or out of plane directions <NUM>, <NUM>, and <NUM> of the holographic panels <NUM> are approximately aligned in the same direction, and edges <NUM>, <NUM>, and <NUM> of the holographic panels <NUM> are also approximately aligned with respect to one another. However, in other embodiments, the holographic panels <NUM> may be arranged in other relative configurations. For example, <FIG> each show a top view of an arrangement of the stack of holographic panels <NUM>, wherein the orientation of each holographic panel <NUM> may be characterized in terms of the gap <NUM>, a tilt angle, and/or a shift or shift distance. As shown, the stack of holographic panels <NUM> may be described with reference to a surface normal <NUM> and orthogonal axes <NUM> and <NUM> in the plane of a reference holographic panel <NUM> in the longitudinal and lateral directions. Note that the directions are defined by parallel edges of the reference holographic panel <NUM>. More specifically, the one or more gaps <NUM> (e.g., direction and distance) are described with respect to the surface normal <NUM> of the reference holographic panel <NUM>. The one or more tilt angles are described with respect to the surface normal <NUM> of the reference holographic panel <NUM> (e.g., a relationship between a surface normal of the respective holographic panel and the surface normal <NUM> of the reference holographic panel <NUM>). The one or more shifts (e.g., direction and distance) are described with respect to the reference holographic panel <NUM> and with respect to the orthogonal axis <NUM>.

With this in mind, <FIG> shows the stack of holographic panels <NUM> having one or more holographic panels <NUM> tilted and/or shifted with respect to one another. In the illustrated embodiment, the stack of holographic panels <NUM> includes the reference holographic panel <NUM> and first and second offset holographic panels <NUM> and <NUM>. The first offset holographic panel <NUM> is tilted with respect to the reference holographic panel <NUM> with a tilt angle <NUM> (e.g., an angle between the surface normal of the first offset holographic panel <NUM> and the surface normal <NUM>) and shifted with respect to the reference holographic panel <NUM> with a shift <NUM> (e.g., direction and distance). The second offset holographic panel <NUM> is tilted with respect to the reference holographic panel <NUM> with a tilt angle <NUM> (e.g., an angle between the surface normal of the second offset holographic panel <NUM> and the surface normal <NUM>) and shifted with respect to the reference holographic panel <NUM> with a shift <NUM>. It should be noted that the tilt angle (e.g., the tilt angles <NUM> and
<NUM>) could be along the orthogonal axis <NUM>, the orthogonal axis <NUM>, or both. The shift angles <NUM> and <NUM> may have the same value or different values, and the shifts <NUM> and <NUM> may be the same distance or different distances.

<FIG> shows the stack of holographic panels <NUM> having the holographic panels <NUM> arranged with variable gaps. As set forth above, the gap <NUM> is described as a distance from the centers of the adjacent holographic panels <NUM> in the surface normal <NUM> or out of plane direction. Herein, the centers of the holographic panels <NUM> are indicated by points <NUM>. In the illustrated embodiment, the stack of holographic panels <NUM> includes the reference holographic panel <NUM> and holographic panels <NUM> and <NUM>. The holographic panels are arranged such that there is a first gap <NUM> between the reference holographic panel <NUM> and the holographic panel <NUM>, and a second gap <NUM> between the holographic panels <NUM> and <NUM>. The first and second gaps <NUM> and <NUM> may have the same value or different values.

<FIG> shows the stack of holographic panels <NUM> having the holographic panels <NUM> arranged with no gap or substantially no gap (e.g., the holographic panels <NUM> are aligned in their orthogonal axes <NUM> and <NUM>). In the illustrated embodiment, the stack of holographic panels <NUM> includes the reference holographic panel <NUM> and holographic panels <NUM> and <NUM>. The holographic panels <NUM> are arranged substantially side by side such that the centers <NUM> of these holographic panels (e.g., <NUM>, <NUM>, and <NUM>) are aligned in the orthogonal axis <NUM>. There may be a shift <NUM> between the reference holographic panel <NUM> and the holographic panel <NUM>, and a shift <NUM> between the holographic panels <NUM> and <NUM>. The shifts <NUM> and <NUM> may have the same value or different values. It should be noted that the stack of holographic panels <NUM> may be arranged in any suitable arrangement as discussed in <FIG>, or a combination thereof. The different arrangements of the holographic panels <NUM> may achieve a larger combined DOF, showing an in-focus, deep, and immersive scene.

Referring back to <FIG>, the one or more light sources <NUM> are configured to illuminate one or more respective holographic panels <NUM> from one or more incident angles. Each of the holographic panels <NUM> may be made of glass or a similar material with high transparency. In some embodiments, the one or more holographic panels <NUM> of the stack of holographic panels <NUM> may be tinted with the same or different transparencies (e.g., about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, or about <NUM>% to about <NUM>% light transparency). In some embodiments, the one or more of holographic panels <NUM> of the stack of holographic panels <NUM> may be opaque and/or <NUM>% tinted. In some embodiments, the first holographic panel <NUM> in the stack of holographic panels <NUM> with respect to an observer may be substantially transparent, such that the observer may see subsequent holographic panels <NUM> behind the first holographic panel <NUM>. In some embodiments, the last holographic panel <NUM> in the stack of holographic panels <NUM> with respect to the observer may be opaque. In some embodiments, the degree of tinting may increase towards the last holographic panel <NUM> in the stack of holographic panels <NUM> with respect to the observer. It should be noted that the distance for each gap <NUM> is determined by the desired depth of the effect. In this way, the content <NUM> (see <FIG>) of each holographic panel <NUM> remains within the respective DOF, such that a composite hologram image of the stack of holographic panels <NUM> is clear (e.g., in-focus) as will be discussed with respect to <FIG>.

<FIG> is a schematic perspective view of a composite hologram image <NUM> produced by the holographic image apparatus <NUM> of <FIG>. In the illustrated embodiment, each holographic panel <NUM> of the stack of holographic panels <NUM> is encoded with holographic 3D content <NUM> that may be the same or different from one another. Each of the content <NUM> has a corresponding DOF <NUM>, and the DOF <NUM> may be different or the same for each holographic panel <NUM>. The gap <NUM> between the adjacent holographic panels <NUM> is controlled, such that a first image <NUM> of the holographic panel <NUM> overlaps with a second image <NUM> of the adjacent holographic panel <NUM> with an overlapping region <NUM>. In accordance with present embodiments, both the first and second images <NUM> and <NUM> are in-focus (e.g., the DOF of the first image <NUM> overlaps with the DOF of the second image <NUM>).

By keeping the content <NUM> of each holographic panel <NUM> within the appropriate depth bounds (e.g., within the DOF) and by stacking the holographic panels <NUM> adjacent to one another, the composite hologram image <NUM> is produced in-focus and has a high DOF. In particular, the overall depth effect of the composite hologram image <NUM> may be tunable without altering the holographic element resolution, and may far exceed that possible from a single holographic panel <NUM>. For example, the overall depth effect of the composite hologram image <NUM> may increase with the number of holographic panels <NUM>. In the illustrated embodiment, the composite hologram image <NUM> (e.g., the first and second images <NUM> and <NUM> combined) has an overall depth effect that spans the DOF of the first image <NUM> and the DOF of the second image <NUM>, which exceeds the DOF of the first image <NUM> or the DOF of the second image <NUM> alone. As such, the content <NUM> of each holographic panel <NUM>, and therefore the composite hologram image <NUM> as a whole, would remain in-focus and clear throughout a depth <NUM> of the entire composite hologram image <NUM> (e.g., a combined depth of field).

It may be appreciated that because the holographic panels <NUM> are substantially transparent or at least partially transparent, the presence of the holographic panels <NUM> does not block or obstruct the continuity of the composite hologram image <NUM>. By way of non-limiting example, a scene may be recorded and encoded onto the stack of holographic panels <NUM>, such that each of the holographic panels <NUM> contains a portion of the scene. The stack of holographic panels <NUM> are arranged with adjacent holographic panels <NUM> placed with appropriate gaps <NUM> such that when the stack of holographic panels <NUM> are illuminated by the one or more light sources <NUM>, each holographic panel <NUM> produces an image that forms a portion of the composite hologram image <NUM>, with the multiple images together showing the in-focus, deep, immersive scene.

<FIG> is a block diagram of certain components forming the holographic image apparatus <NUM> of <FIG>. In the illustrated embodiment, the holographic image apparatus <NUM> includes a controller <NUM> operatively coupled to an imagery system <NUM>. The imagery system <NUM> includes the holographic panels <NUM> and the one or more light sources <NUM> as set forth above. The imagery system <NUM> may also, in certain embodiments, include one or more actuators <NUM> coupled to the one or more light sources <NUM>, the one or more actuators <NUM> being configured to control the arrangement or orientation of the one or more light sources <NUM> upon receiving one or more instructions (e.g., one or more control signals) from the controller <NUM>. For example, the one or more actuators <NUM> may move the one or more light sources <NUM> and/or control one or more incident angles of the one or more light sources <NUM> on the holographic panels <NUM>. The imagery system <NUM> may also, in some embodiments, include one or more actuators <NUM> coupled to the holographic panels
<NUM>. In some embodiments, the one or more actuators <NUM> are configured to control the arrangement or orientation of the holographic panels <NUM> upon receiving one or more instruction (e.g., one or more control signals) from the controller <NUM>. For example, the one or more actuators <NUM> may move the holographic panels <NUM>, change the values of the one or more gaps (e.g., gaps <NUM>, <NUM>, and <NUM>), change the values of the one or more tilt angles (e.g., tilt angles <NUM> and <NUM>), and/or change the values of the one or more shifts (e.g., shifts <NUM> and <NUM>), as discussed in relation to <FIG> and <FIG>. The one or more actuators <NUM> and <NUM> may be any one or a combination of suitable actuators (e.g., hydraulic, pneumatic, electric, thermal or magnetic, or mechanical actuators).

To provide for control over various operational parameters of the imagery system <NUM>, the controller <NUM> may include a processor <NUM> and a memory <NUM> (e.g., non- transitory computer-readable medium/memory circuitry) communicatively coupled to the processor <NUM>. The controller <NUM> may also include a user interface <NUM> communicatively coupled to the processor <NUM> and/or the memory <NUM> to enable a user to provide inputs to control operation of the imagery system <NUM>. For example, the inputs may include, but are not limited to, on/off switches, positions, and/or incident angles of the one or more light sources <NUM>, and the arrangement of the holographic panels <NUM>, such as positions, the one or more gaps (e.g., gaps <NUM>, <NUM>, and <NUM>), the one or more tilt angles (e.g., tilt angles <NUM> and <NUM>), and the one or more shifts (e.g., shifts <NUM> and <NUM>).

The processor <NUM> may include one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more general purpose processors, or any combination thereof. Furthermore, the term processor is not limited to just those integrated circuits referred to in the art as processors, but broadly refers to computers, processors, microcontrollers, microcomputers, programmable logic controllers, application specific integrated circuits, and other programmable circuits. The memory <NUM> may include volatile memory, such as random access memory (RAM), and/or non-volatile memory, such as read-only memory (ROM), optical drives, hard disc drives, or solid-state drives. The memory <NUM> may store one or more sets of instructions (e.g., processor-executable instructions) and/or algorithms implemented to perform operations related to operation of the imagery system <NUM>. For example, the memory <NUM> may store instructions to turn on or off the one or more light sources <NUM> and/or instructions to control the one or more actuators <NUM> and <NUM> in the manner discussed above (e.g., changing positions, orientations, and/or arrangements of the one or more light sources <NUM> and the holographic panels <NUM>). For example, the memory <NUM> may store information about the holographic panels <NUM>, such as information of the encoded holographic 3D content <NUM> and the in-focus DOF <NUM> for each of the holographic panels <NUM>. For example, the memory <NUM> may store algorithms to determine the arrangement of the holographic panels <NUM> (e.g., gaps, tilt angles, and/or shifts) based on the DOF <NUM> of each individual holographic panel <NUM>, such that the encoded content <NUM> of adjacent holographic panels <NUM> overlap and are in-focus. In this way, the controller <NUM> may be considered an imagery system controller, which includes certain programmed algorithmic structure that carries out certain operational methods associated with the illumination and movement of the holographic panels <NUM>.

<FIG> is a flow chart illustrating an example of a method <NUM> of forming the composite hologram <NUM> using the holographic image apparatus <NUM>. While the method <NUM> is described using acts performed in a specific sequence (as represented in blocks), it should be understood that the present disclosure contemplates that the described acts may be performed in different sequences than the sequence illustrated, and certain described acts may be skipped or not performed altogether in other embodiments. The method <NUM> may include providing a plurality of holographic panels (block <NUM>). For example, providing the plurality of holographic panels may include recording and/or encoding a scene on the stack of holographic panels <NUM>, such that each of the holographic panels <NUM> contains a portion of the scene. As set forth above, the holographic panels <NUM> may include substantially transparent material such as glass (as opposed to an opaque material). In some embodiments, at least some of the holographic panels <NUM> may include tinted material (e.g., having about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>% light transparency). The degree of tinting may depend at least in part on the content of the encoded content of the holographic panel <NUM>. For example, the degree of tinting may increase towards the first or the last holographic panel in the stack of holographic panels <NUM> (e.g., the holographic panel that includes an edge or ending portion of the scene). Furthermore, each of the holographic panels <NUM> may be a single-channel hologram or a multi-channel hologram.

The method <NUM> may include placing the plurality of holographic panels adjacent to one another (block <NUM>). More specifically, the plurality of holographic panels <NUM> may be stacked or arranged in such a way that each of the holographic panels <NUM> remains within the respective DOF, such that a composite hologram image of the stack of holographic panels is clear (e.g., in-focus). For instance, the orientation and/or distance between adjacent holographic panels <NUM> (e.g., gaps, tilt angles, shifts) are determined by the desired depth of the effect. For example, the distances (e.g., the gaps <NUM>, the shifts <NUM> and <NUM>) between adjacent holographic panels <NUM> may be controlled such that hologram images of the adjacent holographic panels overlap, and both of the adjacent hologram images are in-focus. By way of non-limiting example, the stack of holographic panels may be arranged in ways discussed in relation to <FIG> or a combination thereof. In some embodiments, block <NUM> may include coupling the plurality of holographic panels to actuator(s) (block <NUM>). For example, the plurality of holographic panels <NUM> may be coupled to the one or more actuators <NUM> to enable changing positions and/or orientations of the plurality of holographic panels <NUM> upon receiving control signals from the controller <NUM>.

The method <NUM> may include placing light sources to illuminate the plurality of holographic panels (block <NUM>). For example, block <NUM> may include disposing the one or more light sources <NUM> in proximity to the stack of holographic panels <NUM> to illuminate the stack of holographic panels <NUM> from suitable light incident angles. The one or more light sources <NUM> may be disposed at positions and orientations suitable to illuminate one or more than one holographic panel <NUM>. In some embodiments, block <NUM> may optionally include coupling the light sources to actuators (block <NUM>). For example, the one or more light sources <NUM> may be coupled to the one or more actuators <NUM> to enable changing positions and/or orientations of the one or more light sources <NUM> to change the light incident angles upon receiving control signals from the controller <NUM>. In some embodiments, different frames of hologram images may be revealed when the multi- channel holographic panels <NUM> are illuminated from different incident angles.

The method <NUM> may include illuminating the plurality of holographic panels to form a composite hologram image (block <NUM>). For example, the one or more light sources <NUM> are turned on manually or upon receiving control signals from the controller <NUM> to illuminate the stack of holographic panels <NUM> to form the composite hologram image <NUM>.

<FIG> is a flow chart illustrating an example of a method <NUM> of operating the holographic image apparatus <NUM> using the controller <NUM>. While the method <NUM> is described using acts performed in a specific sequence, it should be understood that the present disclosure contemplates that the described acts may be performed in different sequences than the sequence illustrated, and certain described acts may be skipped or not performed altogether in other embodiments. The method <NUM> may include coupling the control <NUM> to the imagery system <NUM> (block <NUM>). For example, the controller <NUM> is operatively/communicatively coupled to various components of the imagery system <NUM>, such as the one or more light sources <NUM>, the holographic panels <NUM>, and the one or more actuators <NUM> and <NUM>.

As illustrated, the method <NUM> may include receiving inputs form a user (block <NUM>). For example, the controller <NUM> may receive inputs from a user via the user interface <NUM> coupled to the processor <NUM> and/or the memory <NUM> of the controller <NUM>. The inputs may include instructions to adjust operational parameters of the one or more light sources <NUM> and/or the holographic panels <NUM>. The inputs may include, but are not limited to, on/off switches, positions, and/or incident angles of the one or more light sources <NUM>, and the arrangement of the holographic panels <NUM>, such as positions, the one or more gaps (e.g., gaps <NUM>, <NUM>, and <NUM>), the one or more tilt angles (e.g., tilt angles <NUM> and <NUM>), and the one or more shifts (e.g., shifts <NUM> and <NUM>).

Indeed, to provide for more control of the holographic image, the method <NUM> may include controlling the particular arrangement of the holographic panels <NUM> (block <NUM>). For example, the controller <NUM> may send instructions to the one or more actuators <NUM> to change parameters associated with arrangements and/or orientations of the panels <NUM>, such that adjacent hologram images of the holographic panels <NUM> are in-focus. These parameters may include, but are not limited to, the one or more gaps (e.g., gaps <NUM>, <NUM>, and <NUM>), the one or more tilt angles (e.g., tilt angles <NUM> and <NUM>), and the one or more separation distances (e.g., shifts <NUM> and <NUM>), or a combination thereof.

Claim 1:
A hologram image apparatus (<NUM>), comprising:
a plurality of holographic panels (<NUM>) including a reference holographic panel (<NUM>), each holographic panel (<NUM>) comprising a transparent panel encoded with an interference pattern corresponding to a portion of a composite hologram image (<NUM>); and
a light source (<NUM>) configured to illuminate each of the plurality of the holographic panels (<NUM>) from an incident angle to produce the composite hologram image (<NUM>);
wherein holographic panels (<NUM>) of the plurality of holographic panels (<NUM>) are stacked adjacent to one another to form a gap between adjacent holographic panels (<NUM>), the gap being defined with respect to a direction (<NUM>) normal to a major surface of the reference holographic panel (<NUM>), and wherein the respective depths of fields of the adjacent holographic panels (<NUM>) normal to the major surface of the reference holographic panel (<NUM>) overlap when the interference pattern encoded in each holographic panel is displayed upon illumination by the light source.