Patent ID: 12248150

DETAILED DESCRIPTION

Referring generally to the Figures, systems and methods relating to near-eye display or head up display systems are provided according to various embodiments. Holographic waveguide technology can be utilized in waveguides for helmet mounted displays or head mounted displays (HMDs) and head up displays (HUDs) for many applications, including military applications and consumer applications (e.g., augmented reality glasses, etc.). Switchable Bragg gratings (SBGs) may be used in waveguides to eliminate extra layers and to reduce the thickness of current display systems, including HMDs, HUDs, and other near eye displays and to increase the field of view by tiling images presented sequentially on a microdisplay. A larger exit pupil may be created by using fold gratings in conjunction with conventional gratings to provide pupil expansion on a single waveguide in both the horizontal and vertical directions. Using the systems and methods disclosed herein, a single optical waveguide substrate may generate a wider field of view than found in current waveguide systems. Diffraction gratings may be used to split and diffract light rays into several beams that travel in different directions, thereby dispersing the light rays.

In various embodiments, the grating used in the invention is a Bragg grating (also referred to as a volume grating). Bragg gratings have high efficiency with little light being diffracted into higher orders. The relative amount of light in the diffracted and zero order can be varied by controlling their refractive index modulation of the grating, a property which is used to make lossy waveguide gratings for extracting light over a large pupil. One class of gratings is known as Switchable Bragg Gratings (SBG). SBGs are fabricated by first placing a thin film of a mixture of photopolymerizable monomers and liquid crystal material between parallel glass plates. One or both glass plates support electrodes, typically transparent indium tin oxide films, for applying an electric field across the film. A volume phase grating is then recorded by illuminating the liquid material (often referred to as the syrup) with two mutually coherent laser beams, which interfere to form a slanted fringe grating structure. During the recording process, the monomers polymerize and the mixture undergoes a phase separation, creating regions densely populated by liquid crystal micro-droplets, interspersed with regions of clear polymer. The alternating liquid crystal-rich and liquid crystal-depleted regions form the fringe planes of the grating. The resulting volume phase grating can exhibit very high diffraction efficiency, which may be controlled by the magnitude of the electric field applied across the film. When an electric field is applied to the grating via transparent electrodes, the natural orientation of the LC droplets is changed causing the refractive index modulation of the fringes to reduce and the hologram diffraction efficiency to drop to very low levels. Typically, SBG Elements are switched clear in 30 μs. With a longer relaxation time to switch ON. Note that the diffraction efficiency of the device can be adjusted, by means of the applied voltage, over a continuous range. The device exhibits near 100% efficiency with no voltage applied and essentially zero efficiency with a sufficiently high voltage applied. In certain types of HPDLC devices magnetic fields may be used to control the LC orientation. In certain types of HPDLC phase separation of the LC material from the polymer may be accomplished to such a degree that no discernible droplet structure results. A SBG may also be used as a passive grating. In this mode its chief benefit is a uniquely high refractive index modulation.

SBGs may be used to provide transmission or reflection gratings for free space applications. SBGs may be implemented as waveguide devices in which the HPDLC forms either the waveguide core or an evanescently coupled layer in proximity to the waveguide. The parallel glass plates used to form the HPDLC cell provide a total internal reflection (TIR) light guiding structure. Light is coupled out of the SBG when the switchable grating diffracts the light at an angle beyond the TIR condition. Waveguides are currently of interest in a range of display and sensor applications. Although much of the earlier work on HPDLC has been directed at reflection holograms transmission devices are proving to be much more versatile as optical system building blocks. Typically, the HPDLC used in SBGs comprise liquid crystal (LC), monomers, photoinitiator dyes, and coinitiators. The mixture frequently includes a surfactant. The patent and scientific literature contains many examples of material systems and processes that may be used to fabricate SBGs. Two fundamental patents are: U.S. Pat. No. 5,942,157 by Sutherland, and U.S. Pat. No. 5,751,452 by Tanaka et al. Both filings describe monomer and liquid crystal material combinations suitable for fabricating SBG devices. One of the known attributes of transmission SBGs is that the LC molecules tend to align normal to the grating fringe planes. The effect of the LC molecule alignment is that transmission SBGs efficiently diffract P polarized light (i.e., light with the polarization vector in the plane of incidence) but have nearly zero diffraction efficiency for S polarized light (i.e., light with the polarization vector normal to the plane of incidence. Transmission SBGs may not be used at near-grazing incidence as the diffraction efficiency of any grating for P polarization falls to zero when the included angle between the incident and reflected light is small.

Waveguide Displays

In accordance with various embodiments waveguide displays may take on a variety of configurations. Illustrated inFIG.1there is provided a dual axis expansion waveguide display configuration100comprising a light source101a microdisplay panel102and an input image node (IIN)103optically coupled to a waveguide104. In such embodiments, the waveguide may comprise two grating layers104A,104B. In some embodiments, the waveguide is formed by sandwiched the grating layers between glass or plastic substrates to form a stack within which total internal reflection occurs at the outer substrate and air interfaces. The stack may further comprise additional layers such as beam splitting coatings and environmental protection layers. Each grating layer may contain an input grating105A,105B, a fold grating exit pupil expander106A,106B and an output grating107A,107B where characters A and B refer to waveguide layers104A,104B respectively. The input grating, fold grating and the output grating are holographic gratings, such as a switchable or non-switchable SBG. As used herein, the term grating may encompass a grating comprised of a set of gratings in some embodiments. In general, the IIN103integrates a microdisplay panel102, light source101and optical components needed to illuminate the display panel, separate the reflected light and collimate it into the required FOV. The IIN103projects the image displayed on the microdisplay panel such that each display pixel is converted into a unique angular direction within the substrate waveguide according to some embodiments. In the embodiment ofFIG.1and in the embodiments to be described below at least one of the input fold and output gratings may be electrically switchable. In many embodiments, all three grating types are passive, that is, non-switching. The collimation optics contained in the IIN103may comprise lens and mirrors which is some embodiments may be diffractive lenses and mirrors.

In some embodiments, the IIN may be based on the embodiments and teachings disclosed in U.S. patent application Ser. No. 13/869,866 entitled HOLOGRAPHIC WIDE ANGLE DISPLAY, and U.S. patent application Ser. No. 13/844,456 entitled TRANSPARENT WAVEGUIDE DISPLAY, the disclosures of which are incorporated herein by reference. In some embodiments, the IIN contains beamsplitter for directing light onto the microdisplay and transmitting the reflected light towards the waveguide. In one embodiment, the beamsplitter is a grating recorded in HPDLC and uses the intrinsic polarization selectivity of such gratings to separate the light illuminating the display and the image modulated light reflected off the display. In some embodiments, the beam splitter is a polarizing beam splitter cube. In some embodiment, the IIN incorporates a despeckler. Advantageously, the despeckler may be a holographic waveguide device based on the embodiments and teachings of US Patent No. US8, 565,560 entitled LASER ILLUMINATION DEVICE, the disclosure of which is incorporated herein.

The light source can be a laser or LED and can include one or more lenses for modifying the illumination beam angular characteristics. The image source can be a micro-display or laser based display. LED will provide better uniformity than laser. If laser illumination is used there is a risk of illumination banding occurring at the waveguide output. In some embodiments laser illumination banding in waveguides can be overcome using the techniques and teachings disclosed in U.S. Provisional Patent Application No. 62/071,277 entitled METHOD AND OPTICAL DISPLAY FOR GENERATING INPUT IMAGES FOR HOLOGRAPHIC WAVEGFUIDE DISPLAYS, the disclosure of which is incorporated herein. In some embodiments, the light from the light source101is polarized. In one or more embodiments, the image source is a liquid crystal display (LCD) micro display or liquid crystal on silicon (LCoS) micro display.

The light path from the source to the waveguide via the IIN is indicated by rays1000-1003. The input grating of each grating layer couples a portion of the light into a TIR path in the waveguide once such path being represented by the rays1004-1005. The output waveguides107A,107C diffract light out of the waveguide into angular ranges of collimated light1006,1007respectively for viewing by the eye108. The angular ranges, which correspond to the field of view of the display, are defined solely by the IIN optics. In some embodiments, the waveguide gratings may encoded optical power for adjusting the collimation of the output. In some embodiments, the output image is at infinity. In some embodiments, the output image may be formed at distances of several meters from the eye box. Typically, the eye is positioned within the exit pupil or eye box of the display.

In some embodiments, similar to the one shown inFIG.1each grating layer addresses half the total field of view. Typically, the fold gratings are clocked (that is, tilted in the waveguide plane) at 45° to ensure adequate angular bandwidth for the folded light. However, some embodiments of the invention may use other clock angles to satisfy spatial constraints on the positioning of the gratings that may arise in the ergonomic design of the display. In some embodiments, at least one of the input and output gratings have rolled k-vectors. The K-vector is a vector aligned normal to the grating planes (or fringes) which determines the optical efficiency for a given range of input and diffracted angles. Rolling the K-vectors allows the angular bandwidth of the grating to be expanded without the need to increase the waveguide thickness.

In some embodiments, the fold grating angular bandwidth can be enhanced by designing the grating prescription provides dual interaction of the guided light with the grating. Exemplary embodiments of dual interaction fold gratings are disclosed in U.S. patent application Ser. No. 14/620,969 entitled WAVEGUIDE GRATING DEVICE, the disclosure of which is incorporated herein.

In some embodiments, at least one of the input, fold or output gratings may combine two or more angular diffraction prescriptions to expand the angular bandwidth. Similarly, in some embodiments at least one of the input, fold or output gratings may combine two or more spectral diffraction prescriptions to expand the spectral bandwidth. For example, a color multiplexed grating may be used to diffract two or more of the primary colors.

FIG.2is a plan view of a single grating layer similar to the ones used inFIG.1. The grating layer111, which is optically coupled to the IIN103, comprises input grating105, a first beamsplitter114, a fold grating115, a second beamsplitter116and an output grating107. The beamsplitter are partially transmitting coatings which homogenize the wave guided light by providing multiple reflection paths within the waveguide. Each beamsplitter may comprise more than one coating layer with each coating layer being applied to a transparent substrate. Typical beam paths from the IIN up to the eye118are indicated by the rays1010-1014.

By using the fold grating, the waveguide display may use fewer layers than previous systems and methods of displaying information according to some embodiments. In addition, by using fold grating, light can travel by total internal refection within the waveguide in a single rectangular prism defined by the waveguide outer surfaces while achieving dual pupil expansion. In another embodiment, the input grating, the fold grating and the output grating can be created by interfering two waves of light at an angle within the substrate to create a holographic wave front, thereby creating light and dark fringes that are set in the waveguide substrate at a desired angle

FIG.3illustrates a plan view of a two grating layer configuration similar to the ones used inFIG.1. The grating layers121A,121B which are optically coupled to the IIN103comprise input gratings105A,105B, first beamsplitters114A,114B, fold gratings115A,115B, second beamsplitters116A,116B and output gratings107A,107B, where the characters A, B refer to the first and second grating layers and the gratings and beams splitters of the two layers substantially overlap.

In many waveguide configurations, the input, fold, and output gratings are formed in a single layer sandwiched by transparent substrates.FIG.1illustrates such stacking in reference to items104A and104B. In some embodiments, the waveguide may comprise just one grating layer. In some embodiments, the cell substrates may be fabricated from glass. An exemplary glass substrate is standard Corning Willow glass substrate (index 1.51) which is available in thicknesses down to 50 micron. In other embodiments the cell substrates may be optical plastics.

In some embodiments, the grating layer may be broken up into separate layers. For example, in some embodiments, a first layer includes the fold grating while a second layer includes the output grating. In some embodiments, a third layer can include the input grating. The number of layers may then be laminated together into a single waveguide substrate. In some embodiments, the grating layer is comprised of a number of pieces including the input coupler, the fold grating and the output grating (or portions thereof) that are laminated together to form a single substrate waveguide. The pieces may be separated by optical glue or other transparent material of refractive index matching that of the pieces.

Some embodiments may comprise a grating layer be formed via a cell making process by creating cells of the desired grating thickness and vacuum filling each cell with SBG material for each of the input coupler, the fold grating and the output grating. In one embodiment, the cell is formed by positioning multiple plates of glass with gaps between the plates of glass that define the desired grating thickness for the input coupler, the fold grating and the output grating. In one embodiment, one cell may be made with multiple apertures such that the separate apertures are filled with different pockets of SBG material. Any intervening spaces may then be separated by a separating material (e.g., glue, oil, etc.) to define separate areas.

In other embodiments, the SBG material may be spin-coated onto a substrate and then covered by a second substrate after curing of the material. In some embodiments, the grating in a given layer is recorded in stepwise fashion by scanning or stepping the recording laser beams across the grating area. In many embodiments the gratings may be recorded using mastering and contact copying process currently used in the holographic printing industry.

The embodiment illustrated inFIG.1represents a monochrome waveguide display. As an improvement one may utilize a stack of monochrome waveguides to derive a color display as illustrated inFIG.4.FIG.4illustrates a dual axis expansion waveguide display130comprising a light source101a microdisplay panel102and an input image node (IIN)103optically coupled to red, green and blue waveguides104R,104G,104B, which each comprise two grating layers. In order that wave guiding can take place in each waveguide the three waveguides are separated by air gaps. In some embodiments, the waveguides are separated by a low index material such as a nanoporous film. The red grating layer labelled by R contains an input grating135R,136R, a fold grating exit pupil expander137R,138R and an output grating139R,140R. The grating elements of the blue and green waveguides are labeled using the same numerals with B and G designating blue and green. Since the light paths through the IIN and waveguides in each of the red green and blue waveguides are similar to those illustrated inFIG.1they are nots shown inFIG.4. In some embodiments, the input, fold and output gratings are all passive, that is non-switching. In some embodiments, at least one of the gratings is switching. In some embodiments, the input gratings in each layer are switchable to avoid color crosstalk between the waveguide layers. In some embodiments color crosstalk is avoided by disposing dichroic filters141,142between the input grating regions of the red and blue and the blue and green waveguides.

In some embodiments, a color waveguide may use just one grating layer in each monochromatic waveguide, as illustrated inFIG.5. The embodiment illustrated inFIG.5represents a similar configuration as that shown inFIG.4with each of the red, green, and blue waveguides (104R,104G, and104B) comprising only a single grating layer. Each grating layer having an input grating (152R,152G, and152B), a fold grating (153R,153G,153B), and an output grating (154R,154G,154B) for each of the respective red, green, and blue layers.

Some embodiments of the waveguide may include an eye tracker. One such embodiment is illustrated inFIGS.6,7, and8. The teachings of the various embodiments of the eye tracker configuration may be further illustrated in PCT/GB2014/000197 entitled HOLOGRAPHIC WAVEGUIDE EYE TRACKER, PCT/GB2015/000274 entitled HOLOGRAPHIC WAVEGUIDE OPTICALTRACKER, PCT Application No.: GB2013/000210 entitled OPTICAL DISPLAY FOR EYE TRACKING, U.S. Provisional Patent Application No. 62/176,572 entitled ELECTRICALLY FOCUS TUNABLE LENS, and U.S. Provisional Patent Application No. 62/125,089 entitled HOLOGRAPHIC WAVEGUIDE LIGHT FIELD DISPLAYS, the disclosures of each of which are incorporated herein by reference. Some embodiments may additionally comprise a dynamic focus lens as illustrated inFIG.7the effect of which is to provide a multiplicity of image surfaces.

In various embodiments of the invention the IIN is optically matched to the waveguide. Waveguides raise optical interfacing issues that are not encountered in conventional optical systems in particular matching the input image angular content to the angular capacity of the waveguide and input grating. The optical design challenge is to match the IIN aperture variation as a function of field angle to the rolled K-vector input grating diffraction direction. In various embodiments the waveguide is designed to make the waveguide thickness as small as possible while maximizing the spread of field angles at any given point on the input grating, subject to the limits imposed by the angular bandwidth of the input grating, and the angular carrying capacity of the waveguide.

It should be appreciated that coupling collimated angular image content over the full field of view and without significant non-uniformity of the illumination distribution across the pupil requires a Numerical Aperture (NA) variation ranging from high NA on one side of the microdisplay falling smoothly to a low NA at the other side. NA is defined as being proportional to the sine of the maximum angle of the image ray cone from a point on the microdisplay surface with respect to an axis normal to the microdisplay. Other equivalent measures may be used for the purposes of determining the most optimal IIN to waveguide coupling. Controlling the NA in this way will ensure high optical efficiency and reduced banding and other illumination non-homogeneities in the case of LED-illuminated displays. Laser-illuminated displays will also benefit from the control of NA variation across the microdisplay particular with regard to homogeneity.

In many embodiments, as illustrated, inFIG.9the IIN103comprises a microdisplay panel251a spatially-varying NA component252and microdisplay optics253. The microdisplay optics accepts light1060from an illumination source which is not illustrated and deflects the light on to the microdisplay in the direction indicated by the ray1061. The light reflected from the microdisplay is indicated by the divergent ray pairs1062-1064with NA angles varying along the X axis.

Although a particular configuration of the IIN103is illustrated inFIG.9, it should be understood that a variety of configurations may be used to ensure the most efficient image quality is produced. By way of example the spatially-varying NA component may be located adjacent to the output surface. Additionally, the microdisplay may function as a reflective device, as illustrated inFIG.9, or may function as a transmission or emissive device.

Furthermore, the spatially-varying NA component may take on a variety of configurations having a uniformly varying NA characteristic. Various exemplary embodiments are illustrated inFIGS.10-13. Some embodiments may include a wedge as illustrated inFIG.10while others may be variations of such.FIG.11illustrates a spatially-varying NA component in a curved wedge format.FIG.12illustrates an exemplary embodiment wherein the NA component comprises an array of a plurality of prismatic elements having differing prism angles. Additionally, some NA components may comprise an array of lenses with various apertures and optical powers, as illustrated inFIG.13.

In addition to the various profile characteristics illustrated inFIGS.10-13, spatially-varying NA components may comprise a variety of surface features or internal substrate configurations designed with a variety of scatter elements.FIG.14Aillustrates a spatially-varying NA component having a scatter element integrated with the surface texture.FIG.14Billustrates a substrate of the spatially-varying NA component having scattering properties as part of the base substrate. Such properties may come from a variety of configurations that may include individual scatter components suspended within the body of the substrate.

In some embodiments, such as the one illustrated inFIG.14Ca spatially-varying NA component286comprises a birefringent substrate287having a spatially varying birefringence as represented by the uniaxial crystal index functions288A,288B. In some embodiments, the substrate provides a continuous variation of birefringence. In some embodiments, the substrates comprise discrete elements each have a unique birefringence. In some embodiments, a spatially-varying NA component is a scattering substrate with birefringent properties. In some embodiments, a spatially-varying NA component is based on any of the embodiments ofFIGS.10-13implements using a birefringent substrate. In some embodiments, the NA variation across the field is performed using a birefringent layer having comprising a thin substrate coated with a Reactive Mesogen material. Reactive Mesogens are polymerizable liquid crystals comprising liquid crystalline monomers containing, for example, reactive acrylate end groups, which polymerize with one another in the presence of photo-initiators and directional UV light to form a rigid network. The mutual polymerization of the ends of the liquid crystal molecules freezes their orientation into a three-dimensional pattern. Exemplary Reactive Mesogen materials are manufactured by Merck KgaA (Germany).

In some embodiments, such as the one illustrated inFIG.14Da spatially-varying NA component286comprises an array of diffractive elements each characterized by a unique K-vector and diffraction efficiency angular bandwidth. For example element289A at one end of the component has k-vector K1and bandwidth Δθ1configured to provide a high NA while element289B at the other end has k-vector K2and bandwidth Δθ2configured to provide a low NA. In some embodiments, the grating characteristics vary continuously across the substrate. In some embodiments, the gratings are Bragg holograms recorded in HPDLC materials. In some embodiments, the gratings are surface relief gratings. In some embodiments, the gratings are computer generated diffractive structures such as computer generated holograms (CGHs).

In some embodiments, the IIN design addresses the NA variation problem, at least in part, by tilting the stop plane such that its normal vector is aligned parallel to the highest horizontal field angle, (rather than parallel to the optical axis). As illustrated inFIG.15the IIN287is configured to provide an output field of view of half angle θ defined by the limiting rays1086A,1086B disposed symmetrical about the optical axis1087. The stop plane1088is normal to the limiting ray1086B. It is assumed that the waveguide input grating, which is not illustrated, couples the horizontal field of view into the waveguide (not shown).

Although the present application does not assume any particular configuration of the microdisplay optics253, further embodiments may be further represented in U.S. patent application Ser. No. 13/869,866 entitled HOLOGRAPHIC WIDE ANGLE DISPLAY, and U.S. patent application Ser. No. 13/844,456 entitled TRANSPARENT WAVEGUIDE DISPLAY, the disclosures of which are incorporated herein. In some embodiments, the microdisplay optics contains at least one of a refractive component and curved reflecting surfaces or a diffractive optical element for controlling the numerical aperture of the illumination light. In some embodiments, the microdisplay optics contains spectral filters for controlling the wavelength characteristics of the illumination light. In some embodiments, the microdisplay optics contains apertures, masks, filter, and coatings for controlling stray light. In some embodiments, the microdisplay optics incorporate birdbath optics.

FIG.16shows schematic front views of two waveguide grating layouts that may be provided by the invention. In the embodiment ofFIG.16Athe waveguide300comprises a shaped waveguide comprising in a single layer indicted by1086an input grating302, a fold grating303and an output grating304. The K-vectors of the three gratings (that is the normal vector to the fringes shown inside each grating) are indicated by1083-1084. Note that in each case the K-vector is projected in the plane of the drawings. In the embodiment ofFIG.16Bthe waveguide310comprises a shaped waveguide comprising in a single layer indicted by1090an input grating313, a fold grating314and an output grating315. The K-vectors of the three gratings (that is the normal vector to the fringes shown inside each grating) are indicated by1087-1089. In each case the K-vector is projected in the plane of the drawings.

FIG.17shows a further general waveguide grating layout that may be provided by the invention. The waveguide320comprises a rectangular waveguide comprising in a single layer an input grating322, a fold grating323and an output grating324. The K-vectors of the three gratings (that is the normal vector to the fringes shown inside each grating) are indicated by1091-1093. In each case the K-vector is projected in the plane of the drawings. The fold grating in this case has Bragg fringes aligned at 45 degrees in the plane of the grating

Embodiments of Wearable HUDs

Turning now toFIGS.18A and18B. In many embodiments, the waveguide display is coupled to the IIN103by an opto-mechanical interface thereby allowing the waveguide to be easily retracted from the IIN assembly. The basic principle is illustrated inFIG.18Awhich shows a dual axis expansion waveguide display200comprising the waveguide201containing the input grating105, fold grating106and output grating107and the IIN103. The optical display further comprises an optical link206connected to the waveguide, a first optical interface207terminating the optical link and a second optical interface208forming the exit optical port of the IIN. The first and second optical interfaces can be decoupled as indicated by the gap209illustrated inFIG.18B. In some embodiments the optical link may be a waveguide itself optically designed to work with the main waveguide display104. In some embodiments, the optical link is curved. In some embodiments, the optical link is a GRIN image relay device. In many embodiments, the optical connection is established using a mechanical mechanism. In some embodiments, the optical connection is established using a magnetic mechanism. The advantage of decoupling the waveguide from the IIN in helmet mounted display applications is that the near eye portion of the display be removed when not in used. In some embodiments where the waveguide comprises passive gratings the near eye optics can be disposable

As discussed above, in some embodiments such as the one illustrated inFIGS.18A-19Cthe waveguide display is coupled to the IIN by an opto-mechanical interface that allows the waveguide to be easily retracted from the IIN assembly.FIG.19Ashows a removable near eye display290comprising a near eye waveguide component291and an IIN103. The waveguide component includes an opto-mechanical interface292configured to optically match the IIN and removably connect to the opto-mechanical interface of the IIN294. The waveguide component291can have at least two configurations with respect to the IIN. As illustrated byFIG.19Athe waveguide component291is in a removed or retracted configuration. The waveguide is shown retracted from the IIN assembly.FIG.19Bshows a second 3D view of the HMD296with the waveguide component retracted.FIG.19Cillustrates a connected position of the waveguide component291wherein the component is opto-mechanically connected to the IIN103.

FIG.20A-21Billustrate an exemplary embodiment of a waveguide display that may be integrated into a helmet.FIGS.20A-20Dillustrate front, plan, side, and three-dimensional views of one eyepiece of a dual axis expansion display that may be used in a helmet mount display. One such embodiment may be in a motorcycle helmet. The display comprises the waveguide104, input grating105, fold grating106, output grating107; which were previously described in more detail. Additionally, the waveguide display ofFIGS.20A-20Dmay include a hinge mechanism235for attaching the display to the helmet and the waveguide coupling mechanism236configured to opto-mechanically couple to the IIN assembly.

FIG.21AandFIG.21Bshow a frontal view and a side view of a HUD eyepiece integrated in a helmet. Although a particular helmet configuration is shown it should be understood that any acceptable configuration may be implemented.

Turning now toFIG.22, an exemplary embodiment of a HUD330waveguide display is thus illustrated.FIG.22illustrates a waveguide display in the form of a near eye display. The near eye display comprises an IIN assembly331and a waveguide component291opto-mechanically coupled to the IIN assembly331. The waveguide component further comprises an input grating105a fold grating106and an output grating107. Although not shown here the waveguide component is further configured with an opto-mechanical interface353for coupling the waveguide to the INN assembly331. The waveguide path from entrance pupil2000through the input grating, fold grating and output grating and up to the eye box2005is represented by the rays2001-2004.

FIGS.23A and23Bprovide illustrations of various operational positions according to the invention whereby the HUD330, as illustrated inFIGS.22and19A-19C, is provided as a HMD integrated in a helmet. In such an embodiment the IIN assembly331may form part of the helmet or may be added aftermarket. Similar toFIGS.19Aand19B,FIG.23Aillustrates a HUD display330in a first operational state341in which the waveguide component291is fully retracted from the IIN assembly331. Similarly,FIG.23Billustrates the display in a second operational state342with the waveguide component291coupled to the IIN assembly.

In many embodiments, such as the one illustrated inFIG.24, a display according to the principles of the invention comprises an IIN assembly331a waveguide eyepiece352(which is part of the overall waveguide component previously described) and prismatic relay optics353. The IIN contains at least the microdisplay panel351A illuminated by a light source which is not shown and projection optics2010which typically comprises refractive optics. The IIN assembly331is coupled to the prismatic relay optics by a coupler assembly354which provides mechanical support and an optical connection to admit light from the IIN assembly331into the prismatic relay optics353. The prismatic relay optics comprises a reflective surface353A which may be a TIR surface or may alternatively support a reflective coating. Light from the prismatic relay optics353is coupled into the waveguide eyepiece352via the optical interface layer355which in some embodiments provides polarization selectivity. In some embodiments, the optical interface layer355provides one of spectral or angular selectivity. In some embodiments, the optical interface layer355is a diffractive optical element. In some embodiments, at least one of the transmitting or reflecting surfaces of the prismatic relay optics has optical power. In some embodiments, at least one of the transmitting or reflecting surfaces of the prismatic relay optics supports at least one coating for controlling at least one of polarization, reflection or transmission as a function of wavelength or angle. The image light from the IIN is expanded in the prism to produce sufficient beam width aperture to enable a high efficiency “Roll-K Vector” input aperture-thus preserving efficiency and brightness.

In some embodiments, the waveguide eyepiece352comprises input, fold and output gratings disposed in separate red, green and blue diffracting layers or multiplexed into fewer layers as discussed above. For simplicity, the gratings inFIG.24are represented by the input grating352A, fold grating352B and output grating352C. The light path from the projector through the prismatic relay optics and the waveguide is represented by the rays2010-2013. The output image light viewed by the eye356is represented by the rays2014and2015. The rays2016and2017illustrate the transparent of the waveguide to external light forward of the eyepiece and the transparency of the prismatic relay optics to external light in the periphery of the display wearer's field of view.

In some embodiments, based on the above described display architectures, may also implement a photodetector for detection of ambient light levels for the purpose of matching the display image luminance to the external scene luminance. Although, not shown in in the figures, such photodetectors may be integrated into the helmet structure or electromechanically connected to the HUD display.

Additionally, although it is largely represented in the figures in one configuration it should be noted that the prismatic relay optics may take on any suitable configuration. As illustrated inFIGS.24and27, the prismatic relay optics comprise an elongated prism form whereas for exampleFIGS.40A-40Fillustrate a prismatic relay optics as being largely flat. In some embodiments the prismatic relay optics may be integrated within or right next to the IIN assembly.

One exemplary embodiment of the invention for use in a helmet HUD is illustratedFIGS.27-39which illustrate details of the waveguide eyepiece, IIN, and associated prismatic relay optics linking the IIN and waveguide eyepiece. Design specifications in accordance with many embodiments of the invention are illustrated by the table inFIG.25. Such specifications include the Eye box size, focal distance and image resolution, and are presented for exemplary purposes only.

FIG.26AandFIG.26Bprovide a schematic front and side elevation views a helmet HUD. As described in other figures, the display comprises a waveguide eye piece352, prismatic relay couple353and the IIN assembly331. Additionally,FIGS.26A and26Billustrate one embodiment of the HUD integrated with a helmet where the HUD's spatial relation with respect to the Helmet visor373is shown. In accordance with many embodiments of the invention, where the HUD is integrated with a helmet as illustrated inFIGS.26A and26B, the waveguide eyepiece352may be tilted (rake angle) to the horizontal plane to avoid the visor. In various embodiments the rake angle may be at least 20 degrees, in accordance with many embodiments, the rake angle is at least 25 degrees, which enables eye-relief at least 25 mm while providing generous visor clearance. In many embodiments the design allows the eyepieces to translate between the left and right sides of helmet.

In accordance with other embodimentsFIG.27illustrates a detail of the headpiece HUD comprising the waveguide eyepiece352, the prismatic relay optics353, and a frame or coupler354, which may serve as the opto-mechanical coupling between the waveguide component and the IIN. In accordance with some embodiments the frame or coupler354may comprise a mechanical attachment point that may be selected from a group consisting of a magnet, hinge, or USB connection. In many embodiments the prismatic relay optics are visually transparent to allow ambient light and ensure increased field of vision of the user. In accordance with many embodiments the prism assembly also comprises a corner coupler molding and beam splitter window355and a prism window353B.

In accordance with many embodiments of the invention the opto-mechanical coupler354that couples the prismatic relay optics353to the IIN331as illustrated inFIGS.26-30represents a component of the HUD display. The coupler354may comprise a plurality of alignment characteristics such as magnets, pins, or other physical characteristics to ensure the proper optical alignment of the IIN, the prismatic relay optics, and the waveguide. Under the principles previously discussed the alignment of the image produces by the IIN with the waveguide may be used to ensure a quality image via the output grating. In many embodiments, the angle at which the image is projected from the IIN through the prismatic relay optics and subsequently to the waveguide display is maintained at an input angle configured for the particular optical characteristics desired such that total internal reflection is thus maintained. Therefore, the opto-mechanical coupler354, in accordance with many embodiments, may be fabricated to accurately align the optical output of the IIN with the input grating of the waveguide at an input angle thus ensuring total internal reflection is maintained. Such alignment in accordance with some embodiments is thus illustrated inFIG.27by way of the mechanical design of the coupler with an optical window376B and mechanical magnetic connection points376A. Additional alignment methods are thus illustrated for example inFIGS.40A-40Fwhere the prismatic relay optics comprises a relatively flat component.

FIG.28illustrates an opto-mechanical coupling between the IIN and the waveguide component. In accordance with many embodiments, the IIN assembly331may also comprise a HDMI, DigiLens switch, power on/off switch and a photodiode PCB as generally indicated by331B through331E. As shown inFIG.28the IIN also comprises a microdisplay connector377.

In accordance with many embodiments of the invention,FIG.29shows an exploded view detail of the HUD display without the IIN. The figure shows the waveguide eye piece352, prismatic relay optics and coupler353and354respectively. The prism relay optics353provides a path linking the IIN to the waveguide eyepiece and due to its transparency also provides an enhanced peripheral field of view. The waveguide eyepiece, shown in exploded view, further comprises red, green and blue layers352R,352G,352B encased between two layers of optical film352A,352B. Such film may consist of a polymer type material such that it provides wipe-clean, ballistic anti-shatter protection. Additionally, the optically sound waveguide eyepiece352may be encased by a clear surround molding3352D. In accordance with many embodiments and to connect the power inputs of the IIN with that of the waveguide eyepiece components, a flex cable374E may be used.

Turning now toFIG.30and in accordance with many embodiments an illustrative view of the HUD in a helmet is represented.FIG.30illustrates the HUD with the waveguide eyepiece352opto-mechanically connected to the prismatic relay optics353which opto-mechanically connect to the IIN331via an opto-mechanical coupling. Additionally,FIG.30illustrates the optimal field of view both horizontally and vertically with respect to the HUD when attached to a helmet, as illustrated via the blue and red degree lines. Maintaining adequate Field of View (FOV) angles is another element in the design of the prismatic relay optics.FIG.31further illustrates a preferred embodiment of the prismatic relay optics wherein the peripheral FOV is at least 25 degrees.

In accordance with many embodiments of the invention the IIN may comprise various optics and communications components. As illustrated inFIG.33, many embodiments of the IIN may include a power switch331L, various communication cables331J, a cooling fan331E, and other PCB components331K that are electrically connected to the picoprojector and other optical components of the IIN. As described previously the IIN operates to generate an image and project the image through the prismatic relay optics at the preferred angle such that the image is ultimately displayed via the output gratings of the waveguide eyepiece.

Maintaining ideal temperatures of the electrical optical components may be implemented to ensure the waveguide eyepiece function. Therefore, in accordance with many embodiments a cooling fan331E is illustrated inFIGS.33-35. An exemplary fan for use with the invention is the model UF3A3-700manufactured by Sunonwealth Electric Machine Industry (China). The fan which has a volume of 10×10×3 mm provides an air flow of 3.43 liter/minute. The noise level is 21.0 dB (A)/30 cm. Using a cooling fan of this specification it is possible to meet current 40-degree thermal requirement specifications for motorcycle helmets.

Additionally, as illustrated inFIGS.31-35and38-39, in many embodiments the components of the IIN assembly are collocated within a housing that facilitates the opto-mechanical coupling between the waveguide component and the IIN. In accordance with many embodiments the housing has a minimum wall thickness (e.g., less than 2 mm) to enhance the conduction heat away from the internal components. In many embodiments the IIN assembly may be integrated with the helmet itself or may be subsequently attached thereto.

In accordance with many embodiments, a method of attaching the HUD unit to a helmet is presented. Turning toFIGS.36and37a method of attaching the HUD is illustrated.FIG.36illustrates the use of a supporting headband473that surrounds the users head and has a plurality of securing fixtures471attached thereto. The securing fixtures are configured to interconnect the supporting headband to the inside of a helmet. The securing fixtures may consist of a variety of devices including temporary hook and loop fasteners or more permanent type fasteners. The supporting headband is additionally configured to receive the HUD by way of an interconnection bracket. The interconnection bracket474may be configured to be adjustable along the length of the supporting headband473such that the position of the HUD can be adjusted to the most comfortable position of the user. Additionally, in accordance with many embodiments the interconnection bracket may be configured to allow multiple axis of adjustment2040of the HUD such that when the IIN connects thereto it would thereby allow the user to adjust the position of the HUD to maintain the greatest FOV.FIGS.36and37illustrate the desired FOV through the various adjustments positions of the HUD. Although a particular configuration is illustrated inFIGS.36and37it should be understood that any suitable configuration may be adopted. In accordance with many embodimentsFIG.38illustrates a manner of configuration of the HUD integrated with a helmet such that the desired user FOV is maintained.

In accordance with many embodiments the IIN comprises a picoprojector group378as illustrated inFIG.39(other views are also illustrated inFIGS.31-35). The picoprojector group may further comprise a first projection lens group378A, a second lens group378B for collimating the light reflected from the microdisplay378C. Although not shown in the figures the picoprojector may further comprise an LED illuminator and LED illumination optics. In addition to the optical components, the IIN may further comprise an LED Heatsink379that may coordinate with the aforementioned fan to maintain the optimal thermal specifications. The IIN also comprises a microdisplay video controller PCB377E. In some embodiments the IIN may contain separate rechargeable power cells for powering the various internal components. Ray paths through the projector are indicated by2030and in the prismatic relay element by2031, thereby illustrating the projected optimal path of the image.

In accordance with many embodiments of the invention the HUD may be configured to be removable from a helmet configuration such that when not in use it may be properly stored and if applicable charged for future use.FIGS.40A-40Fillustrate an exemplary embodiment of the invention in which the IIN is configured to be removable from an electromechanical attachment point collocated in/on the helmet. In some embodiments the IIN may attach to the helmet via a magnetic connection. In other embodiments the connection may involve a variety of attachment configurations including a hinge or a USB type connection. Additionally, the IIN assembly may be configured with a communication port such that it may be in communication with other components of a helmet including Bluetooth connectivity and/or GPS. In other embodiments, although not illustrated inFIGS.40A-40F, the attachment/detachment point may be between the waveguide component and the IIN. In such embodiments the waveguide component may be fully removed and properly stored when not in use.

In accordance with many embodiments the prismatic relay optics353as illustrated inFIGS.41A-41B, projects the beam from the pico projector located within the IIN331. The beam will expand in the prism to allow for sufficient aperture to enable a high efficiency “Roll-K Vector” input aperture, thus preserving the efficiency and brightness of the projected image. The brightness of the image is also maintained through the various controllers in the IIN. For example, as illustrated inFIG.50B, light and temperature sensors,640and650respectively, may be located within the IIN to accommodate for changes in ambient temperature and light.

According to many embodiments the IIN331, as mentioned previously also includes mechanisms such as fans and LED heatsinks that help to regulate the temperature to ensure the most efficient image production.FIG.42Aillustrates an ambient air intake410situated within the housing of the IIN. Additionally,FIG.42Billustrates a conditioned air outtake420situated within the IIN housing. Furthermore, the IIN may include internal passive heat dissipation components480as illustrated inFIG.49B. Such passive components may include fins or LED heatsinks as mentioned previously. Additionally, to ensure the most efficient image production the IIN and the opto-mechanical connection may include alignment magnets440and precision electrical connections430. The electrical connections may, according to some embodiments, create the power connections between the various red, green, blue, or mono-color grating layers within the waveguide. Such connection may be configured to maintain an image quality from the IIN to the output grating. In accordance with many embodimentsFIG.43Aillustrates the magnetic and electrical connections between the IIN and the prismatic relay.

FIG.43Bfurther illustrates the magnetic and electrical connections located within the IIN in accordance with some embodiments of the invention. Such connection may be one of several that exist on the IIN. The connection, in accordance with many embodiments of the invention may be configured to avoid a ghosting effect on the final image. Ghosting is spurious colors in the image due to inaccuracies in the individual waveguide light path (as created via the opto-mechanical connections) including glass flatness and can be affected by poor connections. Although specific embodiments of interconnection are shown, it will be understood that the electrical and alignment connections may take on any suitable form that produces a precise alignment.

In accordance with many embodiments the HUD may be configured to mount on a helmet or other headpiece. As illustrated inFIGS.44A-44B, one embodiment is shown where the power and other communication connections480are housed within a bracket470. The bracket may have an alignment feature that correlates to a feature on the IIN such that the IIN securely aligns and connects to the helmet. Such connection may take on any number of forms and may include a magnetic connection445/446on either side of the connection. As further illustrated inFIG.45the alignment bracket470may be adjustable such that it can be configured to attach to any number of suitable head pieces or helmets.

In accordance with many embodiments, as previously discussed, the HUD may be configured to be adjustable within the helmet or head piece.FIGS.46-47Bas well asFIGS.36-38illustrate embodiments of adjustable HUDs. In many embodiments the wearer may be wearing corrective lenses and thus would need to adjust the HUD accordingly so as not to interfere with the lenses and further provide the highest quality of image. As illustrated inFIG.36the attachment points may be fully adjustable. As illustrated inFIGS.46-47B, the rake angle may be adjusted such that the HUD does not interfere with the corrective lenses as applicable. Additionally, as can be seen inFIGS.47A-47Bthe waveguide352and the IIN331can be adjusted to not interfere with corrective lenses500or the internal face shield372of the helmet. In some embodiments the IIN can be adjusted horizontally (e.g., up to 10 mm) as needed. Additionally, in some embodiments the rake angle can be adjusted (e.g., to be within 25-28 degrees).

FIG.48in accordance with some embodiments of the invention illustrates the movement of the HUD with respect to the installation bracket of the desired headpiece. It should be understood that the bracket may take on any suitable form depending on the headpiece. According to many embodiments the bracket470and the IIN331may contain power cables and other communication connections such as HDMI or USB. For example, in some embodiments the IIN may contain a USB-C or other connection built within the PCB and other controllers, as shown inFIGS.49A and49B.

In accordance with some embodiments the HUD may be configured to attach to a head piece that may be retrofitted to a helmet or other device. As illustrated inFIGS.50A and50B, the HUD may connect to a headband that could be used while running or may be used as a retrofit to any helmet.

Because the IIN requires power to control the projectors and produce the image on the waveguide, many embodiments may include a separate power supply. As illustrated inFIG.51, a separate power supply600unit may be located at the rear of the helmet or head piece. The power supply may contain electrical connections between the IIN and the power supply. Such connections may also be integrated within the headband or may be separate and routed through the internal portion of a helmet610. Additionally, the power supply600, being mobile, may be configured with a charging port such that it may be recharged as needed.

In some embodiments, a waveguide display according to the principles of the invention may provide a HUD for use in road vehicles in which image light is reflected off the windscreen into the driver's eye box.FIG.52is a schematic view of a waveguide display embodiment540for car HUD application with a correction element for compensating for windscreen curvature distortion in one embodiment. The optical display for configuration within a car interior541comprises the IIN542, a waveguide543for projecting image light onto a windscreen544and a correction element545which has a prescription designed to balance the wavefront distortion of light reflected off the windscreen. In some embodiments, the correction element is a refractive element. In some embodiments, the correction element is a diffractive element. In some embodiments, the correction element is a plastic optical element. In some embodiments, the waveguide contains at least one birefringence compensation layers designed to balance the birefringence of a plastic correction element place in the path between the waveguide and the eye box. The light path from the waveguide to the eye via the reflection off the windscreen is illustrated by the rays1050,1052. The intersection of the image light with the windscreen and the eye box is indicated by1051,1053. The virtual ray path1054up to the virtual image1055is also shown.

In some embodiments, a dual expansion waveguide display according to the principles of the invention may be integrated within a window, for example, a windscreen-integrated HUD for road vehicle applications. In some embodiments, a window-integrated display may be based on the embodiments and teachings disclosed in U.S. Provisional Patent Application No. 62/125,064 entitled OPTICAL WAVEGUIDE DISPLAYS FOR INTEGRATION IN WINDOWS and U.S. Provisional Patent Application No. 62/125,066 entitled OPTICAL WAVEGUIDE DISPLAYS FOR INTEGRATION IN WINDOWS, the disclosures of which are incorporated herein by reference. In some embodiments, a dual expansion waveguide display may include gradient index (GRIN) wave-guiding components for relaying image content between the IIN and the waveguide. Exemplary embodiments are disclosed in U.S. Provisional Patent Application No. 62/123,282 entitled NEAR EYE DISPLAY USING GRADIENT INDEX OPTICS and U.S. Provisional Patent Application No. 62/124,550 entitled WAVEGUIDE DISPLAY USING GRADIENT INDEX OPTICS, the disclosures of which are incorporated herein by reference. In some embodiments, a dual expansion waveguide display may incorporate a light pipe for providing beam expansion in one direction based on the embodiments disclosed in U.S. Provisional Patent Application No. 62/177,494 entitled WAVEGUIDE DEVICE INCORPORATING A LIGHT PIPE. In some embodiments, the input image source in the IIN may be a laser scanner as disclosed in U.S. Pat. No. 9,075,184 entitled COMPACT EDGE ILLUMINATED DIFFRACTIVE DISPLAY, the disclosures of which are incorporated herein by reference. The embodiments of the invention may be used in wide range of displays including HMDs for AR and VR, helmet mounted displays, projection displays, heads up displays (HUDs), Heads Down Displays, (HDDs), autostereoscopic displays and other 3D displays.

Some of the embodiments and teachings of this disclosure may be applied in waveguide sensors such as, for example, eye trackers, fingerprint scanners and LIDAR systems.

It should be emphasized that the drawings are exemplary in nature and even though particular embodiments are illustrated the design may take on any suitable configuration. Optical devices based on any of the above-described embodiments may be implemented using plastic substrates using the materials and processes disclosed in PCT Application No.: PCT/GB2012/000680, entitled IMPROVEMENTS TO HOLOGRAPHIC POLYMER DISPERSED LIQUID CRYSTAL MATERIALS AND DEVICES, the disclosure of which is incorporated herein by reference. In some embodiments, the dual expansion waveguide display may be curved.

The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (for example, variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure

Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of the invention. Various other embodiments are possible within its scope. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.