Image and wavefield projection through diffuse media

Abstract

The present application relates to image and wavefield projection through a diffuse medium. Methods and systems for projecting wavefields use a diffuse medium, a wavefront shaper, an illumination source, and a control system. A system for projecting an object wavefield into a projection volume includes a wave scatterer, a wavefield projector configured to project a wavefield onto the wave scatterer, and a controller coupled to the wavefield projector. The controller is configured to cause the wavefield projector to project a wavefield that is redirected upon interaction with the wave scatterer to form an object wavefield that forms a predetermined pattern in the projection volume.

Description

[0001] Information about divisional applications

[0002] This case is a divisional application. The parent case of the divisional application is an invention patent application with application date of July 30, 2015, application number 201580050263.6, and invention name “Image and wave field projection through diffuse medium”.

[0003] Related Applications

[0004] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 031,702, filed on July 31, 2014, which is incorporated herein by reference in its entirety. Technical Field

[0005] The present technology is directed to wavefield projection through diffusive media, and more particularly to methods and systems for projecting images through non-conventional scattering elements. Background Art

[0006] Many methods for imaging through diffuse media have been described in the scientific and patent literature.However, there remains a need to achieve the exact opposite: projecting an image or other wavefield into a space that is not visible from the projector due to the diffuse medium.

[0007] Recent work in microscopy has shown that it is possible to pre-distort an optical wavefront in such a way that a diffuser reconstructs the wavefront to form a converging spherical wavefront that is focused to a point. For example, IM Vallekoop et al., "Exploiting disorder for perfect focusing" (ArXiv:0910.0873v1 [Physics. optics], Oct. 5, 2009), which is hereby incorporated by reference in its entirety, describes the use of a spatial light modulator to pre-distort the wavefront and launch the wavefront through a very strong diffuser to a finely focused spot via a learning algorithm.

[0008] Considerable work has been done to employ arrays of projectors to form so-called "light field displays," which essentially reverse the lens photography process. For example, Fellner and Hansen published the paper "Toward the Light Field Display: Autostereoscopic Rendering via a Cluster of Projectors" in EUROGRAPHICS 2006, which is hereby incorporated by reference in its entirety. In this paper, the authors describe projecting an image from an array of projectors onto a diffuse surface of a screen, the screen comprising an array of lenslets and diffuse surfaces separated by the focal lengths of the lenslets. The diffuse screen acts as an image relay for the back focal plane of the lenslets, which then projects a light field in the form of a pinhole projection array.

[0009] In U.S. Patent Application US 2014 / 0063077 (Wetzstein et al., "Tensor Displays", which is hereby incorporated by reference in its entirety), a 3D display involving a stack of spatially addressable light attenuating layers is described. Wetzstein et al. also describe a "compressed light field projector" that employs a highly structured lens screen and a spatial light modulator. The present technology employs one or more spatial phase modulators and one or more unconventional optical elements as described herein. Summary of the invention

[0010] The present application provides a method for manufacturing a near-eye display, which includes: manufacturing a waveguide having a holographic element; placing an optical coupler relative to the holographic element; placing a light field projector relative to the optical coupler, so that the light field projector is configured to project a first light field into the waveguide via the optical coupler for propagation to the holographic element; and providing a controller coupled to the light field projector. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It illustrates that the pre-distorted wavefield enters the diffuser and is then reshaped by the diffuser to converge into a focus.

[0012] Figure 2 A wavefield projector is illustrated emitting a pre-distorted wavefield which enters a diffuser and then forms a column of image points after being reshaped by the diffuser.

[0013] Figure 3 Illustrate the image visible through the eye box in the light field formed by the transmitted wavefront passing through the diffuser.

[0014] Figure 4 A projection system including a wavefield transmitter and two diffusers that together form an image in a projection volume is described.

[0015] Figure 5 is a flow chart illustrating steps in an embodiment using the techniques of the present invention.

[0016] Fig. 6A A projection system is described that includes an array of point light sources, a first volume holographic diffuser, a second diffuser, and an array of points in a projection volume.

[0017] Figure 6B A method for forming one component of the holographic diffuser in 6A is described.

[0018] Fig. 7A A method for calibrating a light field projector to form a series of focal points in a projection volume is described.

[0019] Figure 7B Some of the information flows involved when using a light field projector are described.

[0020] Figure 8 A method for calibrating a diffuser for use in a light field projector using one or more retro-reflective beads is described.

[0021] Fig.9A An alternative approach to calibrating a diffuser in a light field projector is described in which a convex spherical reflector is used.

[0022] Fig. 9B Another alternative approach to calibrating a diffuser in a light field projector is described in which a concave reflector is used.

[0023] Fig. 9C Another alternative approach to calibrating a diffuser in a light field projector is described in which a flat mirror is used.

[0024] Fig.10 Another alternative approach to calibrating a diffuser in a light field projector is described in which retro-reflective beads are used.

[0025] Fig.11A Illustrate the memory effect at a point in the diffuser.

[0026] Fig. 11B The memory effect on an image formed by a light field propagating through a diffuser or through a holographic device is described.

[0027] Fig. 12A Methods for using holographic elements in augmented reality glasses or in other near-eye displays are described.

[0028] Fig. 12B Instructions for making Fig. 12AA method of assembling a holographic element.

[0029] Fig.13 Description of the use Fig. 12A A pair of augmented reality glasses with a holographic element.

[0030] Fig.14 Illustration of a large reflective guided diffuser that directs light only to the eyebox when illuminated by a light field emitter.

[0031] Fig.15 An edge-lit directing diffuser for use in a light field projection display is described.

[0032] Fig.16 A large backlight guided diffuser for use in a light field projection display is described.

[0033] Fig.17 Several persons are shown viewing a three-dimensional light field display through eye boxes.

[0034] Fig.18A Illustration of a 3D image displayed on a laptop computer using a light field projector.

[0035] Fig.18B Illustration of rays from a light field emitter striking a diffuse screen on a laptop computer.

[0036] Fig.18C is a side view of the system illustrated in FIG. 18B , further showing the downstream light field formed by the diffusing screen.

[0037] Fig.19 A room-sized 3D display is illustrated in which light field emitters are located overhead and the diffuser is reflective.

[0038] Fig. 20 A camouflaged vehicle showing a 3D image of a background is illustrated.

[0039] Fig.21 An ultrasonic field projector and focusing of ultrasonic waves through a diffuse medium are described.

[0040] Fig. 22 A ray representation illustrating a portion of a light field that forms a true image of a cubic object and a point object, such that the cubic object appears to be an occluding point object.

[0041] Fig.23 A light field projector that displays both real and virtual images is described.

[0042] Fig.24 The range of viewing angles available for a projected image point from a diffuser is illustrated.

[0043] Fig.25is an alternative representation of a light field projector element suitable for use in a near-eye display, for example.

[0044] Fig.26 A user is illustrated gazing through a light field projector element in a near-eye display.

[0045] Fig. 27 The use of a light field projector to form an in-focus image on a non-planar surface is described.

[0046] The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.The sizes of the various depicted elements are not necessarily drawn to scale and these various elements may be arbitrarily exaggerated to improve readability. DETAILED DESCRIPTION

[0047] introduce

[0048] The linear nature of light propagation allows for a straightforward method for recovering an image from light emitted by an object and then diffused in emission through a diffusing medium. Essentially, the diffused or scattered pattern formed by light emitted by a single object point can be interpreted as an encoded version of the light from that object point. The diffused or scattered pattern formed by light emitted by multiple object points is simply a linear superposition of the encoded versions of all the individual object points in incoherent illumination.

[0049] Although well-known matrix algebra methods can be used to decode the composite diffused or scattered pattern when the individual component patterns are known, in practice it is much more efficient to use successive approximations to perform the decoding. However, it is not the mathematical technique used to decode the composite pattern that is important. Rather, the importance is twofold: first, that decoding is possible; and second, that the linearity of the problem implies that the process is reversible.

[0050] Embodiments of the present technology based on the recognition that the decoding process can be reversed form a coded light field that is decoded upon emission through a diffuse medium to form a desired light field that forms a complex image. In some embodiments, the complex image can be focused on a two-dimensional or three-dimensional surface of arbitrary shape. Similarly, the complex image can include a true three-dimensional image in free space.

[0051] As used herein, a "conventional scattering element" (CSE) is an element whose function is to add a substantially linear or substantially quadratic phase function (or a close approximation thereof) to the phase of an incident wavefield. Adding a linear phase function changes the direction of rays in the wavefield uniformly across the optical element, so (for example) a mirror comprises a single linear phase function CSE, while a prism comprises a pair of linear phase function CSEs (one at the entry surface and one at the exit surface). Adding a quadratic phase function changes the direction of rays in the wavefield in a manner that varies across the optical element. A parabolic mirror is a radially symmetric quadratic CSE, and an ordinary lens is a pair of radially symmetric quadratic CSEs (i.e., the front and back surfaces of the lens). Similarly, a single diffraction grating is suitable as a linear CSE, and a Fresnel zone plate is suitable as a quadratic CSE.

[0052] As used herein, a "non-conventional scattering element" (NCSE) is any optical element that transforms the incident wavefield in a substantially more complex manner than that performed by a CSE. Some examples of static NCSEs include: complex holographic devices, random ground glass diffusers, bathroom glass, diffuse reflectors, lenslet arrays, retro-reflective bead arrays, and transmissive elements made of scattering media. Some examples of programmable NCSEs include: micromirror arrays, liquid crystal spatial light modulators, and deformable mirrors.

[0053] An example non-conventional scattering element that may be incorporated into some embodiments of the present technology is a complex holographic element. A complex holographic element is any optical element that applies a substantially more complex transformation to a light field via diffraction than a CSE applies. In some embodiments, a diffuser may be used as a NCSE to transform a first type of incident wavefield into a second type of wavefield. For example, a wavefield that is approximately matched to a particular diffuser is transformed by the diffuser into a wavefield that is focused to a point.

[0054] Other examples of the present invention will now be described. The following description provides certain specific details to achieve a thorough understanding of these examples and to enable the description of these examples. However, it will be appreciated by those skilled in the relevant art that the present invention can be practiced without many of these details. Similarly, it will be appreciated by those skilled in the relevant art that the present invention may include many other distinct features not described in detail herein. In addition, some well-known structures or functions may not be shown or described in detail below to avoid unnecessarily obscuring the relevant description of various examples.

[0055] The terms used herein should be interpreted in their broadest reasonable manner, even if they are used in conjunction with the detailed description of certain specific examples of the present invention. In fact, certain terms may even be emphasized below; however, any term intended to be interpreted in any limited manner will be openly and explicitly defined as such in this detailed description section. In general, the brief definitions of several terms used herein take precedence over the terms enclosed in double quotes. Such definitions, while experimental, will help those skilled in the relevant art to more fully understand the various aspects of the present invention based on the detailed description provided herein. Such definitions are further defined by the description of the present invention as a whole (including the claims) and are not necessarily defined solely by such definitions.

[0056] Wavefield projection through diffuse media

[0057] Figure 1 The predistorted wavefield 101 is illustrated entering the diffuser 103, then being reshaped by the diffuser 103 into a second wavefield 105 and the second wavefield 105 converging to a point 107. This illustrates the projection of a single point in the projection volume. This method can be generalized to produce more complex images. A linear superposition of other wavefields configured to illuminate other points in the projection volume can be provided simultaneously to produce a complex image comprising many points (voxels) in the projection volume.

[0058] The contrast of a focused point in the light field formed by a diffuser is proportional to N / M, where N is the number of degrees of freedom in the light field and M is the number of points focused into the light field. This means that the image will degrade as the number of points in the image increases; and the only way to obtain a high content image will be to have a very large number of degrees of freedom. However, an image displayed as a raster scan or line scan, or in general as a rapid succession of different parts of an image, will not suffer the same contrast loss as a complete image displayed as a whole. Instead, such an image will have a contrast proportional to N / R, where R is the number of points in the portion of the image displayed at each moment of the scan.

[0059] There are several possible ways to exploit the principles described in order to obtain higher contrast images of high content objects when projected through a diffuser. One such approach, "sub-frame projection," is to rapidly project many sub-frame light fields sequentially, each of which includes a portion of the image to be projected. For example, a sub-frame light field may include several columns or rows of pixels in the image. Alternatively, a sub-frame light field may include image segmentation, where the image is segmented into regions where the contrast or resolution has different levels of visual importance, such as faces versus background or important alphanumeric updates versus ongoing image content. In another example, the image may be segmented according to the region of viewer attention.

[0060] Figure 2A wavefield projector 201 is illustrated emitting a predistorted wavefield 203 which enters a diffuser 205 and then forms an image 207 after being reshaped by the diffuser 205. The wavefield 203 propagates generally along an optical axis direction 209. The light passing through the diffuser 205 illuminates a plurality of voxels in the projection volume to produce a column 211 of voxels in the image 207, here having the shape of the letter "F". I refer to this projection method in which only a relatively small portion of the total number of voxels in the image is projected at any one time as a "sub-frame projection". The entire image 207 is produced by sequentially producing each of the columns of voxels that make up the image 207.

[0061] One way to optimize the visual quality of an image projected according to the present techniques is a combination of a) providing a large number of degrees of freedom in the light field projector (e.g., using multiple spatial light modulators or an array of OLEDs), b) designing and constructing the diffuser to direct light preferentially to the array of pixels that will be displayed, c) further designing and constructing the diffuser to direct light only to the eye frame where the viewer's glasses will reside, and d) matching the degrees of freedom of the light field projector controller with the diffuser so that a set of control states corresponds to a set of light field configurations, which in turn corresponds to predetermined columns or rows of pixels in the displayed image.

[0062] When using sub-frame projection, a light field projector can be used that can switch configurations much faster than standard video projection frame rates. Most liquid crystal devices cannot do this switching fast enough. However, MEMS devices such as micro-mirror projectors can switch on a microsecond time scale. Preferably, the light field projector has very short switching times so that it can project sub-frame image components quickly.

[0063] Figure 3 Illustrates an image that can be seen through the eye box 313 in the light field formed by the transmitted wavefront 203 passing through the diffuser 205. The components are similar to Figure 2 207, except that an eye box 313 is added to represent the intended viewing area from which a viewer will see image 207.

[0064] Figure 4 A system 400 is illustrated that includes a wavefield generator 401 coupled to a controller 403. A first wavefield 405 is emitted from the wavefield generator 401 toward a first diffuser 407 that is a transmissive diffuser. Through interaction between the first wavefield 405 and the first diffuser 407, a second wavefield 409 is emitted from the first diffuser 407 toward a second diffuser 411 that is a reflective diffuser. Light reflected from the second diffuser 411 is focused into a projection volume 413 to produce an image visible to an observer 415.

[0065] The wavefield generator 401 may have any of several different forms, such as a conventional projector array or a plurality of wavefront shaping converters illuminated by coherent or incoherent waves. The terms "wavefield generator" and "wavefront shaper" are interchangeable because a wavefront shaper can form an arbitrary wavefield by being illuminated by an initial wavefield, such as a collimated monochromatic laser beam, and reshaping the initial wavefield as needed. The first diffuser 407 and the second diffuser 411 may have any of several different forms, such as a frosted glass diffuser, a "bathroom glass" diffuser, a rugged reflective surface, corrugated glass, or a medium with a non-uniform refractive index or propagation velocity. In some embodiments, the diffuse properties of the diffuser may be random. The diffuser may be transmissive, reflective, or both. The scattering within each diffuser may be single or multiple. The diffuser may have any shape, such as flat or curved.

[0066] To produce the desired image, the wavefield generator 401 may be calibrated to adapt to the characteristics of the first diffuser 407 and the second diffuser 411. While some methods of correlating the light field at the input of a complex optical system with the light field at the output of the optical system (i.e., methods for calibrating the optical system) are known, such correlations are only used in existing methods to see through optical systems, such as in microscopy, photography through turbid media, astronomy, and telephotography. In contrast, embodiments of the current technology may achieve the opposite result: projecting an image through a diffuse or scattering optical system. This may be achieved by calculating the input light field required to form the desired output light field after passing through a given complex scattering or diffusing optical system. For example, the desired object light field may be represented as a linear sum of plane waves, and the light field that must be projected into a diffuse medium to form the desired object light field will be the linear sum of the corresponding component light fields.

[0067] Figure 5An example process 500 for projecting an image through a diffuse medium and into a projection volume is described. The process begins in box 501 by calibrating a light projector to determine a light field corresponding to a number of points in the projection volume. As mentioned above, this calibration can be achieved using several different methods. The process continues in box 503 to provide an image to be displayed in the projection volume as a sum of the points to be illuminated in the projection volume. The process continues in box 505 to determine a light field corresponding to each of the points to be illuminated in the projection volume. For example, if a static image to be displayed in the projection volume consists of 1000 points to be illuminated, a corresponding light field can be calculated for each of those 1000 points. Next, in box 507, a linear superposition of the determined light fields is calculated. Using the above example, the process would involve calculating a linear superposition of 1000 light fields corresponding to the illumination of the 1000 identified points in the projection volume. Next, in box 509, a light field corresponding to the calculated linear superposition is projected. Thus, each of the indicated points in the projection volume will be illuminated, producing the desired image in the projection volume.The image may be three-dimensional or three-dimensional, and may be static or dynamic (eg, video).

[0068] Fig. 6A and 6B A projection system is described in which a holographic diffuser is constructed to provide desired optical properties for image projection. Fig. 6A A projection system according to the present technology is illustrated, comprising an array of point light sources 601, a first volume holographic diffuser 603, a second diffuser 605, and an array of points 607 in the projection volume. As illustrated, light 604 from the point light sources 601 is reflected by the holographic diffuser 603 and redirected as light 610 toward the second diffuser 605, which focuses the light 608 onto a particular point 607. Figure 6B Description used to form Fig. 6A A method of providing a component of a holographic diffuser 603. Figure 6B As shown in FIG. 6 , light 609 from a coherent laser source is directed toward a specific point 611 corresponding to a point to be positioned at Fig. 6A At the same time, light 613 is emitted from the corresponding Fig. 6A The reference beam 609 is emitted from a point 615 at the location of the point 607 in the projection volume of the holographic diffuser 603 and is coherent with respect to the light 609. The light emitted from the point 615 is scattered as light 614 via the transmissive diffuser 605 and propagates toward the holographic diffuser 603. The interference between the light 613 from the point 615 and the reference beam 609 enables the construction of specific components of the holographic diffuser 603; the components will be as shown in FIG. Fig. 6A607. To construct the complete holographic diffuser 603, a separate exposure can be performed for each pair of point locations 611 and 615. Fig. 6A This is because the holographic element 603 automatically shapes the wavefront 610 to form the necessary image components 607.

[0069] In use Figure 4 When the system described in the drawings is used, a calibration step will generally be performed first. Various calibration techniques are possible, and several calibration techniques are described in detail below. One such calibration technique for a light wave field projector is to place a plurality of retroreflective particles in the area where the image is to be formed, such as Figure 8 A random light field is projected through a diffusing medium. Some of the light falls on the retroreflective particles and returns to the light field projector. The light field is varied under the control of an optimization algorithm until a light field is found that directs the maximum amount of light onto a single retroreflective particle.

[0070] Various optimization methods are possible, as will be appreciated by those skilled in the art. Methods using a wavefront shaper can often be optimized by simply varying one element of the wavefront shaper at a time, seeking maximum brightness of the return signal (e.g., from retroreflective particles). The algorithm cycles through all elements of the wavefront shaper multiple times, seeking maximum return for each element, until no further improvement is found.

[0071] A purely mathematical approach typically starts with a guess at the phase component of the scattering pattern, and represents the light field at the camera as "sqrt(brightness of the scattering pattern) x exp(i xθ)", where θ is the phase (a function of x and y at the camera sensor array). The amplitude (sqrt(brightness of the scattering pattern)), which is known from the camera image of the scattering pattern, is the first constraint. A mathematical transformation is performed to move the representation to the Fourier domain, where other constraints are applied, such as requiring the scattering pattern to be autocorrelated with a delta function. A further constrained estimate of the scattering pattern light field is transformed back to the spatial domain, where the amplitude constraint is again applied, and so on, cycling between the spatial and Fourier domains and reapplying constraints each time, until the quality of the solution is good enough. The quality of the solution corresponds to the degree to which both sets of constraints are satisfied.

[0072] The optimal light field is an encoded version of the image point corresponding to the position of the individual retroreflective particles. The process is repeated until an encoded version is found for each of the retroreflective particles. Note that this calibration process is very similar to the calibration process outlined in reference 1 Physical Review Letters 193905 (May 2011) "Scattering lens resolves sub-100nm structures with visible light". It is also similar to the method used in reference 2 Optics Express Vol. 32 No. 16 (August 15, 2007) "Focusing coherent light through opaque strongly scattering media". Each of these documents is hereby incorporated by reference in its entirety.

[0073] To project an image into an area beyond the diffuse medium, a light field projector projects a linear superposition of the light fields corresponding to each of the points in the image. In practice, it may not be practical to place retroreflective particles everywhere in the area where an image is to be formed; so based on first considerations, it would appear that no detailed image could be formed. However, the so-called "memory effect" ensures that if the projected light field corresponding to a point is slightly tilted, then the resulting focused point is still focused but displaced approximately in proportion to the sine of the tilt angle. The memory effect is illustrated in Fig.11A and 11B In Figure 11A, light pattern 1109 is formed by ray 1107 incident on diffuser (or holographic device) medium 1103. Tilting the angle of incidence of ray 1107 (to form ray 1101) but keeping the incident position unchanged will move light pattern 1109 to a new position 1105.

[0074] Fig. 11B Illustrated is an image 1115 formed by a diffuser 1103 acting on light from a source 1113 (which may be a point source or a more complex wave field). Slightly moving the source 1113 to a new position 1117 causes the image 1115 to move to a new position 1111 in accordance with the memory effect.

[0075] By modifying the curvature of the light field rather than just applying a simple uniform tilt, the focus can be moved along the z-axis (i.e., in a direction toward or away from the diffuse medium). This can be understood as follows. The light field that converges to a given point in the projection area necessarily includes a spherical wave. In order to make the field converge to a new point farther from the diffuse medium, the spherical wave can be reshaped to form a spherical wave centered at the new point. Therefore, it is straightforward to calculate the light field that encodes any point in the 3D area around the retroreflective particles. Therefore, it is not necessary to use retroreflective particles for calibration at every possible point in the image projection volume. If retroreflective particles are used in the calibration, only the following operations are necessary: ​​use retroreflective particles that are positioned densely enough to ensure that the memory effect allows the calculation of the light field corresponding to all points between the particles in the projection volume.

[0076] While retroreflective particles provide one method for calibration as described herein, it is also possible to calibrate in other ways, such as using point light sources at an array of locations of the projection volume. In this case, it is actually simpler to find the input light field corresponding to a point in the projection volume, because the light field formed at the light field generator by light emitted from a point in the projection volume through the diffuse medium in the reverse direction is the conjugate light of the light field that will be focused at that point after passing through the diffuse medium in the forward direction. An alternative calibration method has been called "emission matrix measurement" (well described in Chaigne et al., "Controlling light in scattering media non-invasively using the photoacoustic transmission matrix" (Nature Optics 8, 58–64 (2014), which is hereby incorporated by reference in its entirety) and is fundamentally equivalent to the simpler case described above. If the emission matrix of a complex diffuse optical system is known, it is possible to extract the source object whose light has passed through the optical system and has been recorded at the other end of the optical system. To measure the emission matrix, a plane wave can be projected from the projection volume into a diffuse medium, and the resulting light field (or portion thereof) recorded on the projector side of the diffuse medium. The plane wave is projected into the diffuse medium at many different angles, and the light field (or portion thereof) is recorded at each angle. Since any object can be analyzed as a linear superposition of component plane waves and since the emission matrix comprises linear transformations, the recorded light field from the object comprises, after passing through the optical system, a linear superposition of component light fields, each corresponding to a different plane wave component of the object.

[0077] Another alternative calibration method involves illuminating calibration patterns on surfaces in the projection volume, where the patterns are selected to sum to a basis set, so that suitable arbitrary patterns can be composed as a linear sum of calibration patterns. Suitable sets of patterns include grids of various spacings and angles, Gabor wavelets, and other such pattern sets well known in the field of image and signal processing. Several calibration methods are described in more detail below.

[0078] First calibration method

[0079] The first calibration method uses a known image (e.g., a point source of reflected light) that is propagated back through a diffuser to the photosensor array and combined with a reference beam at the photosensor array to obtain an intensity distribution from which the phase and / or amplitude at the location toward which the light field will be projected can be calculated.

[0080] Fig. 7A A method for calibrating a diffuser for use in a light field projector according to a first calibration method is described. A laser 701 illuminates a point on a scattering screen 703. Scattered light 705 from the screen passes through a diffuser 707 to a camera 709. Light 711 from the same laser 701 enters the camera via a beam splitter 713. The camera 709 detects the interference between light 705 and light 711, from which the phase of light 705 is inferred. By scanning the laser 701 to different points on the scattering screen 703 and by moving the screen 703 to different positions along an axis 715, calibration can be performed for the entire projection volume.

[0081] A light field projector including a phase-only spatial light modulator, an amplitude spatial light modulator, or a combined phase and amplitude spatial light modulator positioned precisely in the same location as the camera 709 that projects the conjugate light field as a calculated light field will produce a light field that, when incident on the diffuser, will emerge to form a focus at the location of the light spot on the screen 703. Similarly, if the image is projected onto the screen 703 using coherent laser light, the phase and / or amplitude distribution of the scattered light 705 can be calculated from the intensity distribution at the camera 709. The conjugate light field can then be projected by the light field projector to form a focused image on the surface 703 downstream of the diffuser 707.

[0082] Figure 7B Some of the information flows involved when using a light field projector are illustrated. As illustrated, a predetermined image 717 and a calibration pattern 719 for a particular system are taken as input to compose a linear sum 721 of the calibration pattern 719 for the individual points that make up the predetermined image 717. This linear sum is then provided to a light field projector 723.

[0083] Second calibration method

[0084] In the description of Figure 8 In the second calibration method in FIG. 8 , a light field projector 801 directs a first light field 803 onto a diffuser 805. In some embodiments, for example, the light field projector 801 may be a spatial light modulator illuminated by a laser beam emitted from a point. The first light field 803 is scattered by the diffuser 805, thereby forming a second light field 807 downstream of the diffuser.

[0085] Some portion of the second light field 807 illuminates the retroreflective bead 809, which retroreflects only the light that illuminates the bead. The light returns through the diffuser to form a light field on the photodetector array 813, from which the phase and amplitude of the light field can be inferred. When the light returned to the detector 813 is maximized, the transmitted light field 803 is the light field that will be focused to the center of the retroreflective bead 809.

[0086] The light field projector 801 may be of a reflective or transmissive type, and changes the phase of the reverse path light to form a conjugate light with the light that first illuminates the light field projector 801. The beam splitter 811 directs the reverse path light to the photodetector 813.

[0087] A variation on this approach is shown in Figures 9A to 9C In. Fig.9A In, a spherical convex mirror 917 is used to retroreflect light converging toward a focus 919 corresponding to the center of curvature of the spherical surface; and in Fig. 9B In , a spherical convex mirror 921 is used to retroreflect light that converges toward a focal point 923 corresponding to the center of the mirror's curvature. A photodetector array 913 is used to detect the returning light field, which when optimized will be a conjugate light field of the light field emitted by the light field projector 801. Another variation on this approach is shown in Fig. 9C and uses a plane mirror 925 (which, from a mathematical point of view, is simply a spherical mirror whose radius of curvature is infinite) and produces a calibration pattern corresponding to a point at infinity.

[0088] Third calibration method

[0089] The third calibration method is described in Fig.10 This method is similar to the second calibration method described above, except that instead of directing the return light to a single photosensor 813 ( Figure 8), the return light is directed to the photosensor array 1027, the location and positioning of which is equivalent to the reflection of the spatial light modulator which is the active component of the light field projector 1001. If the light field 1013 projected by the light field projector 1001 is perfectly focused onto the retro-reflective beads 1009 via the diffuser 1005 as the light field 1016, then retro-reflected back as the light field 1018 and passes through the diffuser 1005 as the light field 1015, then substantially all of the light will return to the beam splitter 1011 and propagate to the photosensor array 1027 and will have the same phase distribution as the light field at the projector 1001. However, the photosensor array 1027 will detect the intensity distribution of the return light, and not the phase distribution of the return light. To detect the phase, a reference beam, such as 711( Fig. 7A ).

[0090] Although Fig. 7A The interference arrangement shown in can be used to infer the phase distribution fairly directly, but the use of an interferometer is not necessary. Alternatively, it is possible to exploit the close mathematical relationship between the known phase distribution of the light field at projector 801 and the intensity distribution of the light field at photosensor array 1027. Since the light field at projector 801 is known, well-known techniques in the optical arts can be used to calculate the intensity distribution of the light field at any plane within the light field. When the light field is precisely adjusted so that it reaches the focus at the retroreflective beads 809, the intensity distribution close to the projector 801 and the intensity distribution close to the photosensor 813 will be almost the same. A method called the GS algorithm can be suitable for performing the optimization relatively quickly and in a highly parallelizable form, as follows:

[0091] Project arbitrary light fields

[0092] - Subtracting the calculated intensity distribution at the spatial light modulator from the received intensity distribution at the photosensor array to obtain an intensity error distribution.

[0093] • Project a new light field calculated by subtracting the square root of the intensity error distribution multiplied by a damping constant from the amplitude / phase distribution at the spatial light modulator.

[0094] • Loop through steps 2 and 3 until the received intensity distribution at the photosensor array closely resembles the calculated intensity distribution at the spatial light modulator.

[0095] Fourth calibration method

[0096] In the process of image construction described above, the magnitude of individual object points is multiplied by the corresponding calibration pattern and the results for all object points are summed to obtain the light field pattern, which forms the image of the object when projected through the diffuser. This would require recalling all calibration patterns for non-zero object points in order to form each projection frame; and the number of such calibration patterns can easily be in the range of one to ten million. Therefore, a method that does not require recalling so many calibration patterns is desirable. The fourth calibration method is described in Fig.11A and 11B middle.

[0097] The memory effect can be exploited to reduce the amount of data transfer required to construct and project an image using current technology. Referring to FIG. 11A , the memory effect refers to the principle that when a light ray 1101 is scattered by a diffuser 1103 to form a pattern 1105, different light rays 1107 incident on the same point but at different angles in the diffuser 1103 are scattered to form substantially the same pattern 1109 that is shifted according to the change in the angle of incidence. This principle holds true as long as the change in the angle of incidence is relatively small. “Relatively small” means that the angle change is small compared to the wavelength of the light divided by (pi x L), where L is the thickness of the diffuser. For example, a frosted glass diffuser has virtually zero thickness. Fig. 11B The memory effect on an image formed by a light field propagating through a diffuser or holographic device is illustrated. For example, a light field projector 1111 projects the light field toward a diffuser 1103, which scatters the light field and forms an image 1113. Positioning the light field projector 1115 at a different location can produce an image 1117 that is substantially the same but in a translated position depending on the properties of the diffuser 1103.

[0098] This means that to a reasonably good approximation, if the light field is focused to a point after passing through the diffuser so that the focus is on the optical axis at a distance D (x=0, y=0) beyond the diffuser, then the light field at the diffuser can be focused by simply tilting the light field at an angle θ (where θ=sin -1 (sqrt(Δx 2 Δy 2 ) / D 2 )) to move the focus to a new point (x=Δx, y=Δy). Furthermore, the focus can be moved to a new distance D+ΔD from the diffuser by applying a tilt that varies linearly with respect to the distance from the axis. Thus, if the diffuser is thin enough so that θ is less than the wavelength of light divided by (pi x L), then it is not necessary to recall or even record a separate calibration pattern for each point in object space. Instead, several calibration patterns can be maintained in local memory and mathematically transformed or interpolated to produce the calibration pattern necessary to form any desired image in object space.

[0099] Selected Embodiments of Augmented Reality Glasses

[0100] Fig. 12A and 12B Element 1200 is illustrated for use in compact augmented reality glasses. The glasses may include a holographic guided diffuser, a two-dimensional waveguide spatial light modulator, a laser source, and a controller for the modulator. In particular, Fig. 12A A method for using a holographic element in augmented reality glasses is illustrated. A laser 1201 illuminates a coupler 1203 along an optical axis 1205. The light propagates through a modulator 1207 via total internal reflection (TIR), enters the holographic element 1200, and is converted by a component 1209 of the holographic element 1200 into a collimated beam 1211 that enters the pupil of the user's eye at 1213 shown as being oriented along an axis 1215. A second component 1217 of the holographic element 1200 is also shown that will direct light from a different direction 1215 to the pupil of the user's eye. Fig. 12B Description of the method for producing a laser beam 1219 using an object beam 1219 and a reference beam 1221 from a coherent light source 1223 Fig. 12A A method of assembling a holographic element.

[0101] Inside a multimode waveguide, propagating modes are superimposed but travel in different directions with different total internal reflection angles. Therefore, an optical modulator element acting on a small portion of the waveguide will have a different effect on each mode, even if the modulated element acts with only one degree of freedom. An array of many such modulator elements acting at different points in the waveguide will affect all modes, with each element providing an independent degree of freedom. Although it would be difficult to control any mode using a single such element, the linearity of light propagation ensures that in the case where the number of such elements is sufficiently greater than the number of modes to be controlled, some combination of control parameters applied to the various control elements will effectively control any selected mode while eliminating effects on other modes.

[0102] Any display or projector can be characterized by its number of degrees of freedom. A typical flat panel display with N pixels has N degrees of freedom. A light field projector with N projection elements, each of which projects M independently controllable rays of light, has N x M degrees of freedom.

[0103] When a light field with N degrees of freedom illuminates a diffuser, the light field that emerges from the diffuser has N degrees of freedom. If the diffuser scatters each component of the illuminating light field into M different directions, then the resulting exiting light field still has only N degrees of freedom. If M is greater than N, then the quality of the exiting light field that can be constructed therefrom is reduced, with noise in the ratio of approximately (MN) / M. Therefore, the quality of a light field projected using a diffuser in such a technique can be significantly improved by using a diffuser that only scatters light into a number of directions comparable to the number of degrees of freedom possessed by the light field projector that illuminates the diffuser.

[0104] Such a diffuser is called a "guided diffuser". An example of a guided diffuser is a holographic optical element. Methods for producing a holographic guided diffuser are described in Fig. 12B In the embodiment of the present invention, a holographic recording medium having the shape of a glasses lens is illuminated by collimated laser light of a selected wavelength, and light from a light field projector simultaneously illuminates the same recording medium. The collimated light and the projected light field are temporally interfering with each other. A series of N exposures are made, each exposure utilizing collimated light with a different angle of incidence and utilizing a projected light field with a different configuration. In some embodiments, each of the light field configurations is orthogonal to the other configurations in the sense that the cross correlation of any configuration with any other configuration is zero. Fortunately, any two light fields with random phase distributions are very close to being mutually orthogonal.

[0105] Fig. 12A and 12B The use and construction of a particular type of guided diffuser suitable for projecting a light field with relatively few degrees of freedom, yet still capable of conveying wide parallax three-dimensional images, are described separately. The resulting holographic diffuser, when illuminated with any of the light field configurations, will only diffract light into the directions of the collimated light used with that configuration when the holographic diffuser was recorded. When two or more such illumination configurations are used, the diffuser emits a linear superposition of corresponding beams (e.g., beam 1211). The degree to which light "leaks" into undesired directions depends primarily on the degree of orthogonality of the different light field configurations.

[0106] exist Fig. 12B In the arrangement of , the collimated light fills the eyebox or aperture associated with the holographic element 1209 in each exposure step. It is not necessary to fill the entire recording medium. If the entire recording medium is filled, the resulting holographic diffuser will diffract light to areas outside the pupil of the eye. In some embodiments, the collimated light only fills the "eyebox" and is therefore emitted from only a relatively small portion of the recording medium.

[0107] In some embodiments, the incident direction of the collimated light used to construct the holographic diffuser is selected to form a rectangular angular array of n×m=N different angles, n angles high and m angles wide. Since light scattering, at least as used in the current technology, is a linear process, illuminating the holographic diffuser with a linear superposition of any subset of the light field configurations used to construct the holographic diffuser will produce an exit light field that constitutes a linear superposition of the exit light fields corresponding to the illumination configurations. Therefore, to construct a virtual image of a two-dimensional image at infinity, the holographic diffuser is illuminated by a superposition of the light field configurations corresponding to each of the points in the image. Of course, a point at infinity corresponds to a collimated beam traveling toward that point.

[0108] The light field projector in this embodiment is an array of waveguide modulators with a minimum of N = nxm elements. For best results, N can be much larger than nxm (approximately 100 times larger). Larger N enables higher resolution and higher contrast in the projected image.

[0109] Fig.13 An augmented reality eyewear system 1300 is illustrated having a holographic device 1207 as an eyewear lens, a waveguide modulator array 1301, and a controller 1303 integrated into a temple arm 1305 of the eyewear 1300. Two such systems operating together, each acting as one lens of a pair of eyewear, can project one of a pair of stereo images to each eye, thereby providing a three-dimensional image. With a sufficiently fast controller, the images can be updated at 30 frames / second or more to provide a three-dimensional video display. A camera 1307 is embedded in the temple arm 1305 of the eyewear system 1300 and can be oriented to capture images (still or video) in the direction the wearer is facing. In some embodiments, in applications such as augmented reality, data from the camera 1307 can be included to provide information about the environment and the position and orientation of the eyewear 1300 relative to the environment to the controller 1303. It should be noted that if the source 1223 is an array of independently addressable sources (such as an OLED array), the modulator 1207 can be omitted.

[0110] In some embodiments, the holographic element may be formed in a volume holographic recording medium such as dichromated gelatin, holographic polymer dispersed liquid crystal, or photopolymer. As is well known in the art of holographic optical elements, a volume holographic device may be transparent to ambient light when properly recorded, but diffracts light of specific wavelengths at high angles and spectrally selectively. If the holographic diffuser is such a volume holographic device, then the glasses may be transparent to ambient light and provide a clear view of the environment, but simultaneously provide a three-dimensional computer-generated view or a remotely recorded view superimposed on the environment.

[0111] The eyeglass lens 1207 may be a holographic element constructed using at least three wavelengths of laser light in the red, green and blue ranges (at least 3xN exposures total). Substantially the same wavelengths are then used in a waveguide lightfield projector to provide a full color three dimensional display. Due to the high angular and spectral selectivity of the holographic diffuser, there is negligible crosstalk between the red, green and blue image components.

[0112] An obvious advantage of using a holographic element in this and other embodiments of the technology is that the diffuser does not have to be calibrated (e.g., as described above) because it is constructed from the outset in such a way that there is a one-to-one correspondence between a set of light field projector controller states and the desired projected image pixels. Another obvious advantage of using a holographic diffuser is that the diffuser is easily designed and constructed to maximize image contrast and resolution and to maximize light efficiency.

[0113] The embodiments described herein are provided as examples of the technology for informative purposes. They do not define limitations on the scope of the technology. Many variations of the structures and methods described are possible without departing from the scope of the technology. For example, the diffuser need not be holographic. It may be random or non-random. It may be transparent as in the case of a volume holographic diffuser, or opaque as in the case of densely suspended light scattering particles. It may be a wide-angle diffuser or a narrow-angle diffuser; and it may be a transmissive diffuser (e.g., bathroom glass) or a reflective diffuser (e.g., a movie projection screen). For example, a light field projector illuminating the diffuser may be a waveguide light field projector, an array of lenses each supported by an emitting array (e.g., an LED array or a VCSEL array), an array of lenses each supported by a transmissive array (e.g., an LCD), or an array of reflective arrays (e.g., an LCOS display). For example, the light source may be an external laser, an array of lasers, or an array of LEDs.

[0114] In augmented reality glasses, visual information about the environment may be provided, for example, via a video camera mounted on the glasses frame or by direct vision through transparent diffuser glasses lenses.

[0115] exist Fig.13In the illustrated embodiment of , a light field projector and glasses lenses together constitute a projection system that projects a light field that is perceived by the wearer as an image at a distance. Note that the image does not have to be at infinity or at any particular fixed distance, and the image can be a 3D image. In this case, the system projects a virtual image to the wearer's eye. The glasses lenses can be a diffusing material or a volume hologram. The use of a volume hologram is advantageous because it only diffuses light of a predetermined wavelength and propagation angle (or several predetermined wavelengths and angles). Therefore, most of the ambient light is transmitted through the glasses lenses without being modified, while the light from the light field projector is redirected to the user's pupil. Therefore, the wearer can see through the glasses lenses (as if they were simple transparent lenses), but the virtual image projected by the glasses is perceived as overlaid on the surrounding scene. Therefore, the glasses lenses can independently perform the function of vision correction.

[0116] If the wearer's eyes are considered part of the optical system and if the light field components correspond to specific patterns (such as a grid or dots) on the retina of the eye, then virtual reality or augmented reality glasses can compensate for aberrations in the eye and even cataracts and other such complex optical defects.

[0117] The embodiments as described above are not limited to use as augmented reality displays. For example, they can be used to watch videos or as head-mounted instrument displays or as communication devices. And, for example, they can be used in virtual reality systems or in telepresence systems (such as systems for operating drones or robots).

[0118] Selected Embodiments of Three-Dimensional Display Panels

[0119] The technology of the present invention also provides a three-dimensional display panel. Fig.14 , a large guided diffuser 1401, such as a holographic diffuser, can be illuminated by a light field projector 1403 to provide a wide angle, full parallax 3D display through an eye box 1405 through which a viewer 1407 views the image. The illumination can be as Fig.14 Through reflection, such as Fig.15 As described in the total internal reflection and input coupler 1509 or as Fig.16 The diffuser diffuses light only into the eyebox aperture where the viewer's eye will reside (e.g. Fig.17 ) is advantageous, both to maximize power efficiency and to reduce the number of degrees of freedom that must be controlled. Since constructing a holographic diffuser large enough to be used as a three-dimensional display panel can be cumbersome and expensive, it can be desirable for this embodiment to manufacture the diffuser in the form of a surface relief structure that can be mass-produced by well-known methods such as UV casting, injection molding, or pressure molding.

[0120] An advantage of current technology in providing a three-dimensional display is that each image point can be formed by converging or diverging rays from a wide range of angles. Therefore, any image point can be viewed from a wide range of angles. This is in contrast to three-dimensional displays that project stereoscopic views into a narrow range of angles or positions, so that the image appears to jump as the viewer moves from side to side.

[0121] When a light field projector has a large number of degrees of freedom, it is possible to construct an image point using beams of rays from selected directions. In this way, an image point can be given an opaque or transparent appearance. This is described in Fig. 22 , where light that may appear from a point behind projected object 2208 becomes non-existent when viewed from area 2205 and becomes present when viewed from area 2207, thereby making object 2208 appear opaque.

[0122] Fig. 22 A ray representation illustrating a portion of a light field that forms an actual image. Light propagates from a diffuser 2200 toward a focus 2201 and reaches a viewing plane 2203. A first portion 2205 of the light field forms an actual image that can be viewed from the viewing plane 2203, while a second portion 2207 of the light field does not form an actual image visible from the viewing plane 2203.

[0123] It should be noted that any subset of the projected light field will form a corresponding subset of the desired light field in the projection volume, and that resolution improves as the projected subset is made larger, either by using a greater sampling density or by using a wider sampling angle range. The current technology is not limited to projecting light wavefields. It is applicable to projecting any kind of wavefield, including optical wavefields, ultrasound wavefields, seismic wavefields, water surface wavefields, surface plasma wavefields, microwave fields, terahertz wavefields, x-ray wavefields, audible sound wavefields, and even quantum wavefields of atomic and subatomic particles. In each case, a wavefront shaper is needed that is capable of shaping that type of wave in the projected wavefield.

[0124] Reflective wavefront shapers are possible for all types of waves for which there is a reflective interface. For example, deformable mirrors are often used in adaptive optics. For example, deformable mirrors or arrays of small mirrors individually driven by piezoelectric devices can perform wavefront shaping for light, microwaves, x-rays or acoustic waves. Arrays of phase modulators can perform wavefront shaping for light, microwaves, acoustic waves, surface plasmon waves, electron quantum waves or electron waves.

[0125] A common type of wavefront shaper comprises an array of individually electrically addressed liquid crystal filled elements. By varying the voltage across the elements, the retardation of the liquid crystal layer with respect to a particular polarization direction can be varied, resulting in a controllable phase shift of light passing through the element and having that particular polarization. There are two types of liquid crystal wavefront shapers, reflective and transmissive.

[0126] Wavefront shapers are not limited to phase shifting. Amplitude-only wavefront shapers can work well, although less efficient than phase-only wavefront shapers. Diffusing media are used to diffuse waves of the type being projected. For example, titanium dioxide particles suspended in a gel, glass, or polymer slats can be used to diffuse light. Microbeads suspended in a gel can diffuse light or sound waves. Media such as frosted glass, bathroom glass, or an uneven reflective surface can be used to diffuse light. Similarly, an uneven slat of any material in which the propagation velocity is different from the surrounding material can act as a diffuser of waves. For example, microwaves have a different propagation velocity in paraffin than in air. Surface topography, doping patterns, and other such features that locally affect the propagation velocity of surface plasma waves can diffuse surface plasma waves.

[0127] The "projection volume" may refer to a three-dimensional area, a two-dimensional area, or even a one-dimensional area. For example, surface plasmon waves travel along a surface, as do surface waves on water and surface acoustic waves. In embodiments of the current technology, a wavefield projector may project surface waves that are redirected through a diffusing medium to form an object wavefield that forms a predetermined pattern within a projection volume, which is the area on the surface over which the surface waves propagate.

[0128] Additional Applications

[0129] The ability to form a predetermined focused image by propagating an appropriate light field through (or reflecting an appropriate light field from) a diffuse medium enables heretofore impossible image projection applications. Some examples include: projecting images onto surfaces of arbitrary shapes, projecting wide-angle real and virtual 3D images, virtual reality glasses, augmented reality glasses, immersive virtual reality environments, camouflage, acoustic surgery, and beam steering. Some of these practical applications deserve further explanation.

[0130] Projecting an image onto an arbitrary shape is advantageous in photolithography in order to form a pattern that conforms to a surface, such as a missile nose cone, wing, or lens. For example, an array of light sensors on the curved back surface of a spherical refractive ball can be made into a very wide angle camera.

[0131] Figures 18A to 18CA laptop computer 3D display implemented by current technology is illustrated. As illustrated, a laptop computer 1800 includes a light field projector 1801 disposed above a keyboard 1803. The light field projector 1801 projects light toward a diffuse screen 1805, which then scatters the light, which is focused to form an image 1807 in the space in front of the screen 1805.

[0132] Immersive virtual reality environments can be constructed based on current technologies, such as Fig.19 The diffuse panels 1901 are located on all walls and the light field projector 1903 is located in the panel above the head. The system can project any 3D scene anywhere in the room via the projector and the diffuse panel, and the user 1905 can move freely within the scene.

[0133] If the inventive technique is used to project a 3D image relatively close to a large diffuse panel, the viewing angle of the 3D image depends on the width and position of the panel relative to the 3D image rather than the width and position of the light field projector relative to the 3D image. Thus, even if the diffuse panel is reflective and the light field projector is located behind the viewer, the viewer will at best cast a very diffuse shadow on the panel.

[0134] Vehicle camouflage system 2000 is described in Fig. 20 , which includes a diffuse panel 2001 and an overhead light field projector 2003 configured to direct light onto the diffuse panel 2001. It is possible to use current technology to project an arbitrary 3D image using the side of the vehicle 2005 as the diffuse panel 2001 and thereby disguise the vehicle. If the projected image corresponds to a 3D scene behind the vehicle 2005, then the vehicle will not actually be visible. Fig. 20 In the diagram of FIG. 2004 , a flat diffuser panel 2003 is shown for simplicity, however, in some embodiments, the diffuser panel may be replaced by a complex curved surface (for example, a surface that follows the contour of the vehicle 2005 ).

[0135] It is important to note that the current technology is not limited to static projections. By frequently updating the projected image, it is possible to project 3D video. On a larger scale, it is possible to project 3D images in theaters. An advantage of a 3D image projected by a current system is that the image is visible from all positions within the viewing volume with full viewing angle and parallax, as if it were an actual 3D object.

[0136] The current technology can also be used advantageously in ultrasonic surgery because it enables precise selection of specific areas of tissue where the ultrasound is to be focused. Fig.21An ultrasonic surgical system 2100 is illustrated in which an ultrasonic field projector 2101 generates ultrasonic waves 2103 that are focused in a focal region 2109 (eg, at a surgical site) as they are diffused by a diffusing medium 2105 and pass through tissue 2107 .

[0137] Current technology can be used to project underwater acoustic images that appear to unfriendly acoustic sensors as real ships, submarines, or obstacles. Similarly, it can be used to project microwave wave fields via reflections from static ground features so that they appear to unfriendly radar sensors as real aircraft, vehicles, or other objects.

[0138] Current technology can be used to project a visible 3D image via a diffuse surface (such as the wall of a building) to give the impression that a person or object is present when in fact they are not.

[0139] Fig.23 A light field projector 2301 is illustrated with light 2303 incident on a first diffuser 2305 which scatters a second light wave 2307 and causes the second light wave 2307 to propagate toward a second diffuser 2309. When the second light wave 2307 interacts with the second diffuser 2309, both a real image 2311 and a virtual image 2313 are displayed. The light field 2303 is a combination of fields 2311 and 2313.

[0140] Fig.24 The range of viewing angles available for images projected from diffuser 2401 at points 2403 and 2405 is illustrated. As illustrated, the image at point 2403 will have a much larger viewing angle 2407 than the viewing angle 2409 associated with the image at point 2405 because point 2403 is closer to diffuser 2401.

[0141] Fig.25 is an alternative representation of a light field projector element 2500 in a slab-like form factor. In use, light 2501 impinges on a coupler 2503, passes through a modulator array 2505 via total internal reflection, and is diffracted by a holographic element 2507 to form an image 2509. This is a preferred form factor for eyewear applications.

[0142] Fig.26 User 2601 is shown gazing through one light field projector element 2603 in a near eye display. Images 2605 and 2607 appear in the far field to user 2601. Light from light source array 2620 is emitted through total internal reflection waveguide 2615 and shaped by modulator 2610, then enters holographic glasses lens element 2603 where it is then diffracted to form images 2605 and 2607.

[0143] Fig. 27 The use of a light field projector 2701 is illustrated to form an in-focus image 2703 on a non-planar surface 2705. As illustrated, light from the projector 2701 passes through a diffuser 2707 and is then focused onto the surface 2705 to produce the image 2703.

[0144] In various embodiments, beam steering using current technology may be advantageous when it is desirable to direct an optical, ultrasound, or microwave beam to multiple targets simultaneously. In such a case, the "image" formed by the object wavefield may be multiple foci, one on each target.

[0145] It should be noted that while the above description of current technology deals only with light fields that do not change rapidly, it is possible to control the spatial and temporal phase of light fields on a micron and femtosecond scale using today's technology. A light pulse that is tens of femtoseconds long has only a longitudinal extent of about one micron. If this pulse is spread widely across a diffuser that is substantially larger than one micron, the resulting light field will arrive at any given point downstream not as a single pulse but as illumination whose intensity and direction of incidence vary widely and rapidly. If the light field is coherent, all light incident at any point simultaneously will interfere, but the interference pattern will change rapidly. If the light field contains multiple frequencies of light, the spectrum at that point will change rapidly.

[0146] In the calibration process of the current technology, it is possible to control both the spatial and temporal shape of the light pulse to maximize both the spatial and temporal convergence of the light field onto the reflective particles in the projection volume or onto a predetermined pattern (e.g., a grid on an arbitrary surface) after passing through (or reflecting off) a diffuse reflector. The spatial / temporal shape of the light pulse thus comprises a component pattern for forming an arbitrary spatiotemporal pulsed light field or image in the projection volume.

[0147] Similarly, current technology makes it possible to control the polarization and spatial and temporal shape of a light field (as described in U.S. Pat. No. 7,352,469 to McGrew, entitled "Quantum Resonance Analytical Instrument," which is hereby incorporated by reference in its entirety). Thus, current technology enables the projection of a predetermined pulsed light field having a controlled spatial and temporal shape and polarization.

[0148] Hardware and software considerations

[0149] The wavefield or lightfield projector, the photodetector and / or the photoelectric sensor array may be coupled to a processing unit for controlling the projector and / or for analyzing the output of the photodetector or photoelectric sensor array. The processing unit may be a computing device that includes a suitable processor or central processing unit (CPU) that processes data according to computer-readable instructions stored on a system memory. For example, the CPU may control the execution of the various routines described herein and may provide input to control the wavefield or lightfield projector. The CPU may be any logical processing unit, such as one or more CPUs, digital signal processors (DSPs), application specific integrated circuits (ASICs), etc. The CPU may be a single processing unit or multiple processing units in a device or distributed across multiple devices. The CPU is connected to a memory and may be coupled to other hardware devices (for example, by using a bus (e.g., PCI Express or Serial ATA bus)). By way of example, the CPU may include a standard personal computer ("PC") or other types of embedded computers running any suitable operating system (e.g., Linux, Windows, Android, iOS, MAC OS, or embedded real-time operating system). In some embodiments, the CPU may be a small form factor PC with an integrated hard disk drive ("HDD") or solid state drive ("SSD") and a universal serial bus ("USB") or other port to communicate with other components. In other embodiments, the CPU may include a microprocessor with a separate motherboard that interfaces with a separate HDD. The memory may include read-only memory (ROM) and random access memory (RAM) or other storage devices such as a disk drive or SSD that stores executable applications, test software, databases, and other software required to implement the various routines described herein, for example. In some embodiments, the processing unit may be connected to the wavefield or lightfield projector via a hardwired connection, while in other embodiments, the processing unit may be remote from the projector.

[0150] In the worst case, where the diffuse media are multiple and far apart, the light field pattern encoding each image point is uncorrelated. In other words, the memory effect is so small that it is useless. Therefore, in that case, each point in the projection volume will be individually calibrated to the diffuse medium.

[0151] Statements herein referring to a light field projector may be interpreted as referring to a general wave field projector, provided that the projector projects a wave field of a certain type, the diffuse or scattering medium redirects waves of said type, and the object wave field is of said type. Wherever the word "diffuse" or its derivatives are used, the word "scatter" or its corresponding derivatives have the same meaning and vice versa. In the case of a holographic element, the projected image or image points are formed by diffraction rather than ordinary diffusion, but for convenience, I refer in some cases to light being "diffused" by a holographic element rather than being "diffracted" by the element. In those cases, the meaning is effectively the same.

[0152] A light field projector can easily accommodate millions of independent elements, so the light field corresponding to one point in the projection volume is typically represented by millions of values. In order to project a given 3D image that constitutes N points, it may be necessary to overlay N sets of component light fields. This may require the manipulation of tens to hundreds of billions of necessary component light fields and the storage and retrieval of all necessary component light fields. In order to project a 3D video image at full resolution, approximately 30 composite light fields would need to be calculated per second. Available computer hardware, such as multi-CPU / multi-GPU computers, can process tens of thousands of video frames per second.

[0153] There are many ways to find light field patterns that, when used to illuminate a diffuser, result in the formation of a desired image downstream of the diffuser. The process of finding those light field patterns is referred to herein as "calibration" of the diffuser, but it should be understood that it is in fact a calibration of the combination of the diffuser, light field projector, and controller.

[0154] Summarize

[0155] A "light field" refers to a collection of light rays in a volume of space. Equivalently, a "light field" refers to a collection of light wavefronts in a volume of space or through and propagating from a surface. In the case of a display, a "light field" may consist of a series of light fields that are perceived by an observer as if they were collectively a single light field (such as in sub-frame projection).

[0156] A "wavefield" refers to the set of wavelengths and propagation vectors of any selected type of waves propagating in a volume of space or through and from a surface.

[0157] A wavefield projector is any device that projects a wavefield of a predetermined type that can be controlled or prescribed by a controller.

[0158] A "light field projector" is any device that projects a light field that can be controlled or specified by a controller. For example, a light field projector can be one or more coherent or incoherent light sources, projection optics, and a spatial modulator for each light source. The spatial modulator can modulate any of phase, amplitude, and / or polarization.

[0159] Although a lens or multiple lenses may be incorporated into the light field projection system, the light field generator does not necessarily need any lenses. For example, a light field projector may be a large phased array of laser diodes, each of which emits a spherical wave. Alternatively, it may be an array of liquid crystal elements or deformable mirror elements illuminated by a plane light wave. Many other types of light field generators are available and possible. The present technology does not depend on the type of light field generator used.

[0160] The term "scatterer" refers to a wave scatterer. Typically, but not always, the term "scatterer" means a wave scatterer whose scattering function varies on a very short length scale. For example, a light diffuser or scatterer can be opal glass, ground glass, suspended scattering particles, an array of small lenslets, an array of small prisms, or generally any medium that randomly or quasi-randomly redirects light at every point on the medium. Another example of a scatterer is a holographic element. A holographic element that converts each of a set of arbitrary point source light fields into a corresponding specific light field component is also referred to herein as a "holographic diffuser", but it is not the traditional meaning of a "diffuser".

[0161] The term "waveguide" refers to any structure, device, or component whose function is to confine light to a narrow path range. For example, a waveguide can be an optical fiber (which confines light to multiple total reflection modes inside the fiber), a planar waveguide (such as a glass plate, which confines light to the interior of the plate by total internal reflection at the glass / air interface).

[0162] The term "input coupler" means any structure or component that redirects light from a light field outside the waveguide into the waveguide. For example, a prism or bevel at one edge of a glass sheet may redirect light from a specific range of incident angles in air into a total internal reflection mode within the glass sheet and thus may be an input coupler. Another example of an input coupler is a grid or holographic optical element that diffracts external incident light into a total internal reflection mode inside the sheet.

[0163] The term "output coupler" means any structure or component that redirects light incident from a total internal reflection mode in a waveguide to a light field propagating outside the waveguide. The output coupler is typically identical in structure to the input coupler, except that the light propagates in opposite directions relative to the input coupler and the output coupler.

[0164] The term "three-dimensional image" may refer to a non-planar image, a point cloud, or a planar image in a three-dimensional volume.

[0165] In the context of the present invention, the term "modulator" means any device, component, structure, or element that, when activated, controllably affects the phase, amplitude, direction, or polarization of light passing through an active area of ​​the device, structure, or element. For example, the following items may be considered "modulators": transmissive liquid crystal displays, reflective liquid crystal displays, deformable mirrors, electrically or optically controlled absorbers, acousto-optic modulators, electrochromic displays, and micromirror arrays.

[0166] The term "near-eye display" means any device whose function is to produce a controllable light field that constitutes a virtual image, so that when the device is placed at a small distance from the eye (typically less than about 3 inches), the eye perceives the virtual image as being at a much greater distance (typically ranging from 2 feet to infinity).

[0167] Unless the context clearly requires otherwise, the words "comprise", "comprising", etc. throughout the description and claims should be interpreted as being inclusive, as opposed to exclusive or exhaustive; that is, in the sense of "including but not limited to". As used herein, the terms "connect", "couple" or any variation thereof mean any connection or coupling, direct or indirect, between two or more elements; the coupling or connection between elements may be physical, logical, or a combination thereof. In addition, when used in this application, the words "herein", "above", "below", and words of similar meaning should be considered as a whole rather than any particular part of this application. Where the context permits, words used in the singular or plural in the above detailed description may also include the plural or singular, respectively. The word "or" referring to a list containing two or more items encompasses all of the following interpretations of the word: any one of the items in the list, all of the items in the list, and any combination of the items in the list.

[0168] The specific implementation of the examples of the present invention above is not intended to be exhaustive or to limit the present invention to the precise form disclosed above. Although the specific examples of the present invention are described above for illustrative purposes, various equivalent modifications can be made within the scope of the present invention as will be recognized by those skilled in the relevant art. For example, although processes or blocks are presented in a given order, alternative embodiments can also perform routines with steps or adopt systems with blocks in different orders, and some processes or blocks can be deleted, moved, added, subdivided, combined and / or modified to provide alternatives or sub-combinations. Each of these processes or blocks can be implemented in various different ways. And, although processes or blocks are sometimes shown as continuous execution, these processes or blocks can be alternatively executed or implemented in parallel, or can be executed at different times. In addition, any specific numbers mentioned herein are only examples: alternative embodiments can adopt different values ​​or ranges.

[0169] The teachings provided herein may be applied to other systems, not necessarily the systems described above. The elements and actions of the various examples described above may be combined to provide other embodiments of the present invention. Some alternative embodiments of the present invention may include not only additional elements to those embodiments mentioned above, but also fewer elements.

[0170] Any patents and applications mentioned above and other references (including any references that may be listed in the attached papers in which the application is filed) are incorporated herein by reference. Aspects of the present invention may be modified, if necessary, to adopt the systems, functions, and concepts of the various references described above to provide some embodiments of the present invention. When statements or subject matter in an application incorporated by reference conflict with statements or subject matter in the present application, the present application shall control at that time.

[0171] These and other changes can be made to the present invention according to the above specific embodiments. Although the above description describes certain examples of the present invention and describes the expected best mode, no matter how detailed the above is presented in the text, the present invention can be practiced in many ways. The details of the system can be greatly changed in its specific embodiment but still covered by the present invention disclosed herein. As mentioned above, the specific terms used should not be regarded as implying that the terms are redefined in this article to be limited to any specific characteristics, features or aspects of the present invention associated with the terms when describing certain features or aspects of the present invention. In general, the terms used in the attached claims should not be regarded as limiting the present invention to the specific examples disclosed in the specification, unless the above specific embodiments chapter clearly defines these terms. Therefore, the actual scope of the present invention not only covers the disclosed examples, but also covers all equivalent ways of practicing or implementing the present invention according to the claims.

[0172] In order to reduce the number of technical solutions, some aspects of the present invention are presented in the form of specific technical solutions below, but the present application covers various aspects of the present invention in any number of technical solution forms. For example, although only one aspect of the present invention is described as a component plus function technical solution according to Section 112 (f) of Chapter 35 of the United States Code, other aspects can be embodied as component plus function technical solutions or in other forms (e.g., embodied in computer-readable media). (Any technical solution intended to be processed according to Section 112 (f) of Chapter 35 of the United States Code will start with the word "component for...", but the use of the term "for" in any other context is not intended to call for processing according to Section 112 (f) of Chapter 35 of the United States Code). Therefore, the applicant reserves the right to continue additional technical solutions after applying for the present application to continue such additional technical solution forms in the present application or in a follow-up application.

[0173] Examples

[0174] 1. A system for projecting an object wavefield into a projection volume, comprising:

[0175] wave diffuser;

[0176] a wavefield projector configured to project a wavefield onto the wave diffuser; and

[0177] A controller is coupled to the wavefield projector, wherein the controller is configured to cause the wavefield projector to project a wavefield that is redirected upon interaction with the wave diffuser to form an object wavefield, the object wavefield forming a predetermined pattern in the projection volume.

[0178] 2. The system of example 1, wherein:

[0179] The wave field projector comprises a light field projector,

[0180] The wave diffusing medium includes a light diffuser, and

[0181] The object wave field includes an object light field.

[0182] 3. A three-dimensional image projector comprising the system according to Example 2, wherein the object light field forms a three-dimensional image.

[0183] 4. A camouflage system comprising the system according to example 2.

[0184] 5. A heads-up display comprising the system according to example 2.

[0185] 6. The heads-up display of example 5, wherein the light diffuser comprises a volume hologram configured to diffuse light of a plurality of predetermined wavelengths, and

[0186] Wherein the light field projector is configured to project a light field comprising the predetermined wavelength.

[0187] 7. An acoustic surgical system comprising the system of example 1, wherein:

[0188] The wave field projector includes an acoustic field projector;

[0189] The wave diffuser comprises an acoustic diffuser; and

[0190] The object wave field includes an object sound field.

[0191] 8. A near-eye display, comprising:

[0192] a holographic element configured to be positioned in front of an eye of a wearer;

[0193] a light field projector configured to project a first light field into the holographic element via an optical coupler; and

[0194] a controller coupled to the light field projector, wherein the controller is configured to determine the first light field and cause the light field projector to project the first light field,

[0195] causing the holographic element to redirect the first light field to form a second light field that is directed into an eye of the wearer, and

[0196] Such that the second light field can be perceived by the wearer as a virtual image at a distance from the eye and the holographic element.

[0197] 9. A near-eye display according to Example 8, wherein the holographic element is contained within a flat or curved strip of translucent material.

[0198] 10. The near-eye display of example 8 wherein the holographic element is configured to redirect light of predetermined colors and transmit light of other colors without substantial redirection.

[0199] 11. The near-eye display of Example 8, wherein the second light field further forms a three-dimensional image.

[0200] 12. An eyeglass assembly comprising the near-eye display according to Example 8, the eyeglass assembly comprising:

[0201] A frame configured to be worn on the wearer's head, the frame comprising first and second edges in which lenses are secured and first and second temple arms extending away from the first and second edges.

[0202] 13. An eyeglass assembly according to example 12, wherein the holographic element is integrated into at least one of the first and second lenses.

[0203] 14. The eyeglass assembly of example 12, wherein the light field projector and the controller are integrated into one of the first and second temple arms.

[0204] 15. The eyeglass assembly of example 12, further comprising a second near-eye display.

[0205] 16. A method of manufacturing a near-eye display, comprising:

[0206] manufacturing a holographic element configured to be positioned in front of a wearer's eye;

[0207] positioning an optical coupler relative to the holographic optical element;

[0208] disposing a light field projector relative to the optical coupler such that the light field projector is configured to project a first light field onto the holographic element via the optical coupler; and

[0209] A controller is provided that is coupled to the light field projector.

[0210] 17. The method of clause 16, wherein manufacturing the holographic element comprises:

[0211] providing a holographic recording medium;

[0212] The holographic recording medium is illuminated with a reference beam from a first angle of incidence while the holographic recording medium is illuminated with light from the light field projector in a first configuration, wherein the light from the light field projector is temporally coherent with the collimated reference beam.

[0213] 18. The method according to example 17, further comprising:

[0214] The holographic recording medium is illuminated with the reference beam from a second angle of incidence, wherein the second angle is different from the first angle, while the holographic recording medium is illuminated with light from the light field projector in a second configuration, wherein the second configuration is different from the first configuration.

[0215] 19. The method of example 18, wherein the first configuration is orthogonal to the second configuration.

[0216] 20. The method of example 17, wherein the holographic recording medium is embedded in a strip of translucent material.

[0217] 21. A three-dimensional image projection system, comprising:

[0218] Light diffuser;

[0219] a light field projector configured to project light onto the light diffuser; and

[0220] a controller coupled to the light field projector, wherein the controller is configured to:

[0221] determining a first light field; and

[0222] causing the light field projector to project the first light field onto the light diffuser,

[0223] wherein when the first light field is scattered by the light scatterer, the first light field forms a second light field, and

[0224] The second light field forms a predetermined three-dimensional image.

[0225] 22. A three-dimensional image projection system according to Example 21, wherein the predetermined three-dimensional image includes an actual image.

[0226] 23. A three-dimensional image projection system according to Example 21, wherein the predetermined three-dimensional image is a virtual image.

[0227] 24. A three-dimensional image projection system according to Example 21, wherein the predetermined three-dimensional image is conformally focused onto a non-planar surface.

[0228] 25. The 3D image projection system of Example 21, wherein the light field projector comprises:

[0229] light source;

[0230] waveguide;

[0231] an input coupler configured to receive light from the light source and couple the light into the waveguide such that the coupled light propagates within the waveguide via total internal reflection;

[0232] an array of modulators located within the waveguide, the modulators configured to alter the phase, amplitude, or polarization of the light propagating within the waveguide; and

[0233] An output coupler is configured to redirect the modulated light out of the waveguide.

[0234] 26. A three-dimensional image projection system according to Example 25, wherein the modulator array includes a spatial light modulator.

[0235] 27. A three-dimensional image projection system according to Example 21, wherein the light diffuser is an unconventional optical element.

[0236] 28. A three-dimensional image projection system according to Example 27, wherein the unconventional optical element includes a volume holographic device.

[0237] 29. A system for projecting an object wavefield into a projection volume, comprising:

[0238] wave diffuser;

[0239] a wavefield projector configured to project a wavefield onto the wave diffuser; and

[0240] A controller is coupled to the wavefield projector, wherein the controller is configured to cause the wavefield projector to project a wavefield that is redirected upon interaction with the wave diffuser to form an object wavefield that forms a predetermined complex functional pattern in the projection volume.

[0241] 30. The system of example 29, wherein:

[0242] The wave field projector comprises a light field projector,

[0243] The wave diffusing medium includes a light diffuser, and

[0244] The object wave field includes an object light field.

[0245] 31. A system according to Example 30, wherein the predetermined complex functional pattern includes an image in the projection volume.

[0246] 32. A computer monitor comprising the system according to example 30.

[0247] 33. A three-dimensional image projector comprising the system according to Example 30, wherein the object light field forms a three-dimensional image.

[0248] 34. A lithography system comprising the system of example 30, wherein the object light field is configured to form a predetermined image in a photosensitive medium that is consistent with a surface in the projection volume.

[0249] 35. A camouflage system comprising the system according to example 30.

[0250] 36. A heads-up display comprising the system according to example 30.

[0251] 37. The heads-up display of example 36, wherein the light diffuser comprises a volume hologram configured to diffuse light of a plurality of predetermined wavelengths, and

[0252] Wherein the light field projector is configured to project a light field comprising the predetermined wavelength.

[0253] 38. The system of example 29, wherein:

[0254] The wave field projector includes an acoustic field projector;

[0255] The wave diffuser comprises an acoustic diffuser; and

[0256] The object wave field includes an object sound field.

[0257] 39. An acoustic surgical system comprising the system according to Example 38.

[0258] 40. A near-eye display comprising:

[0259] a holographic element configured to be positioned in front of an eye of a wearer;

[0260] a light field projector configured to project a first light field onto the holographic element via an optical coupler; and

[0261] a controller coupled to the light field projector, wherein the controller is configured to determine the first light field and cause the light field projector to project the first light field,

[0262] causing the holographic element to redirect the first light field to form a second light field that is directed into an eye of the wearer, and

[0263] Such that the second light field can be perceived by the wearer as a virtual image at a distance from the eye and the holographic element.

[0264] 41. A near-eye display according to Example 40, wherein the holographic element is embedded in a flat or curved strip of translucent material.

[0265] 42. The near-eye display of example 40, wherein the holographic element is configured to diffuse light of a predetermined color and transmit light of other colors without substantial scattering.

[0266] 43. A near-eye display according to Example 40, wherein the second light field further forms a three-dimensional image.

[0267] 44. An eyeglass assembly comprising the near-eye display of example 40, the eyeglass assembly comprising:

[0268] A frame configured to be worn on the wearer's head, the frame comprising first and second edges in which lenses are secured and first and second temple arms extending away from the first and second edges.

[0269] 45. The eyeglass assembly of example 44, wherein the holographic element is positionable over one of the first and second lenses.

[0270] 46. ​​An eyeglass assembly according to example 44, wherein the holographic element is integrated into one of the first and second lenses.

[0271] 47. The eyeglass assembly of example 44, wherein the light field projector and the controller are coupled to the frame.

[0272] 48. The eyeglass assembly of example 47, wherein the light field projector and the controller are integrated into one of the first and second temple arms.

[0273] 49. The eyeglass assembly of Example 44, further comprising a second near-eye display.

[0274] 50. A method of projecting an image through a diffuser using a light field projector and into a projection volume, the method comprising:

[0275] determining a light field corresponding to a plurality of points in the projection volume;

[0276] providing the image to be displayed in the projection volume as a sum of points to be illuminated in the projection volume;

[0277] determining the light field corresponding to each of the points to be illuminated in the projection volume;

[0278] calculating a linear superposition of each of the determined light fields; and

[0279] A light field corresponding to the calculated linear superposition is projected onto the diffuser, thereby forming the image in the projection volume.

[0280] 51. The method of example 50, wherein determining the light field corresponding to the plurality of points in the projection volume comprises calibrating the light field projector.

[0281] 52. The method of example 51, wherein calibrating the light field projector comprises:

[0282] placing a point light source in the projection volume;

[0283] placing a photosensor in a position to receive light from the point light source that first passes through the diffuser;

[0284] The photosensor is illuminated with a reference beam that is temporally coherent with the point light source.

[0285] 53. A method according to example 52, wherein a beam splitter redirects at least a portion of the light from the point light source toward the photosensor after it passes through the diffuser.

[0286] 54. The method of Example 51, wherein the photosensor comprises a photosensor array.

[0287] 55. The method of example 51, wherein calibrating the light field projector comprises:

[0288] placing a retroreflector in the projection volume;

[0289] placing a photosensor in a position to receive light retroreflected from the retroreflector that passes through the diffuser; and

[0290] The retroreflector is illuminated with light from the light field projector.

[0291] 56. A method according to example 55, wherein a beam splitter redirects at least a portion of the retroreflected light toward the photosensor after it passes through the diffuser.

[0292] 57. A system for projecting an object wavefield into a projection volume using a wavefield projector and a diffuser, the system comprising:

[0293] means for determining a plurality of input wavefields that, when projected by the wavefield projector onto the diffuser, are redirected to form corresponding component wavefields in the projection volume,

[0294] wherein the component wavefields include a set of wavefields by which the object wavefield in the projection volume can be formed as a linear superposition;

[0295] means for defining a wavefield of an object projected into said projection volume;

[0296] means for determining linear decomposition coefficients of the object wave field into component fields;

[0297] means for computing a linear superposition of said input wave fields corresponding to said component fields; and

[0298] Means for projecting a wavefield corresponding to the linear superposition of the input wavefields onto the diffuser.

[0299] 58. The system of example 57, wherein the wavefield projector comprises a lightfield projector and the wavefield comprises a lightfield.

[0300] 59. The system of example 57, wherein the coefficients of the linear superposition of the prescribed object wavefield are proportional to the coefficients of the linear decomposition.

Claims

1. A method of manufacturing a near-eye display, comprising: Fabricating waveguides with holographic elements; positioning an optical coupler relative to the holographic element; disposing a light field projector relative to the optical coupler such that the light field projector is configured to project a first light field into the waveguide via the optical coupler for propagation to the holographic element; and providing a controller coupled to the light field projector, wherein the light field projector has N projection elements and each of which projects M independently controllable light rays, and The holographic element scatters light into a number of directions comparable to the number of degrees of freedom of the light field projector.

2. The method of claim 1 , wherein manufacturing the holographic element comprises: providing a holographic recording medium; The holographic recording medium is illuminated with a reference beam from a first angle of incidence while the holographic recording medium is illuminated with light from the light field projector in a first configuration, wherein the light from the light field projector is temporally coherent with the reference beam.

3. The method according to claim 2, further comprising: The holographic recording medium is illuminated with the collimated reference beam from a second angle of incidence, wherein the second angle of incidence is different from the first angle of incidence, while the holographic recording medium is illuminated with light from the light field projector in a second configuration, wherein the second configuration is different from the first configuration. The method of claim 3 , wherein the first configuration is orthogonal to the second configuration.

5. The method of claim 2, wherein the waveguide comprises a slab of translucent material.

6. The method of claim 1 , wherein the controller is configured to determine the first light field and cause the light field projector to project the first light field into the waveguide, wherein the holographic element redirects the first light field to form a second light field that is directed to an eyebox, and wherein the second light field is perceived within the eyebox as a virtual image at a distance from the holographic element. The method of claim 6 , wherein the second light field generates a plurality of voxels in a projection volume.

8. The method of claim 6, wherein the holographic element comprises a plurality of holographic components within different locations along the waveguide, wherein the first light field is projected into the waveguide in a plurality of propagation modes, and wherein each of the plurality of holographic components redirects a different one of the propagation modes of the first light field from the different locations along the waveguide.

9. The method of claim 1, wherein the waveguide is a flat or curved slab of translucent material.

10. The method of claim 1, wherein the holographic element is configured to redirect light of predetermined colors and transmit light of other colors without substantial redirection.

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