JP2019053289A - Transparent waveguide display - Google Patents

Abstract

To provide a method for sampling an input image field to make efficient, coupling of an output image of an input image node into a wave guide path.SOLUTION: An apparatus for displaying an image is provided that comprises: a first optical substrate comprising at least one waveguide layer 101 configured to propagate light in a first direction, wherein the at least one waveguide layer of the first optical substrate comprises at least one grating lamina configured to extract the light from the first substrate along the first direction, and a second optical substrate comprising at least one waveguide layer 102 configured to propagate the light in a second direction, wherein the at least one waveguide layer of the second optical substrate comprises at least one grating lamina configured to extract the light from the second substrate along the second direction, wherein at least one grating lamina of at least one of the first and second optical substrates comprises an SBG (Switchable Bragg Grating) in a passive mode.SELECTED DRAWING: Figure 2

Description

RELATED APPLICATIONS This application is a US provisional application 61 / 796,632 filed on November 16, 2012 and a US application filed February 4, 2013, each of which is incorporated herein by reference in its entirety. This is a continuation-in-part of US Application No. 13/844456, filed on March 15, 2013, claiming priority of provisional application 61 / 849,853.

  There is a need for a compact transparent data display capable of displaying image content ranging from symbolic and alphanumeric arrays to high resolution pixelated images. Examples of the transparent display include HMD, HUD, and HDD. In any case, one important factor is that the display must be very transparent and must be clearly visible when the displayed image content is superimposed on a bright background scene. It is. The display must give all colors an extended color gamut for optimal data visibility and impact, but black and white is sufficient for many applications. One important factor in helmet mounted displays is that the display must be easily attached to a standard helmet or a replica of a helmet designed for training. The pupil distance and pupil must be large enough to avoid image loss even during head movements for demanding military and sports activities. The image generator must be compact, solid state, and have low power consumption. In automotive applications, the ergonomic requirements are equally demanding, and aesthetic considerations bring additional demands on display form factors that should ideally be able to be hidden in the dashboard when not in use. In many other applications, there is a growing need for more compact, cheaper and more efficient structures. We note the increasing demands on airplanes and small aircraft HUDs. Car manufacturers are also looking to install HUDs and HDDs in their future models. The system described herein augments augmented reality immersive team training (AITT), essentially indirect aiming and aircraft launches required to qualify or cultivate observer skills or It may be applicable to a helmet-mounted head-mounted display used in a live simulation training system for observer training to replace them.

  Said goal is not achieved by current technology. Current structures only provide the proper pupil, pupil distance, and field of view to show through, and at the same time provide high brightness at the expense of cumbersome form factors. In many helmet mounted display structures, the weight is distributed to the worst possible location in front of the eye. The most common approach to providing a transparent display relies on a reflective or diffractive visor illuminated by off-axis light. A microdisplay having a high resolution image generator on an extremely small flat panel does not always help miniaturization. This is because the need for very high magnification results in a large diameter optical element. An ideal transparent display is a display that first preserves situational awareness by providing a transparent view of the whole scene with high transparency and secondly provides a high-resolution, wide-field image. Such a system must be modest, ie, compact, lightweight and comfortable. In this case, comfort is sufficient exit pupil and eye movement box / exit pupil (> 15 mm), proper pupil distance (≧ 25 mm), ergonomic center of mass, infinity focus, and fit with protective headgear It is brought about by having sex. Currently, in the future, conventional refractive optical elements cannot meet this series of requirements. Other important identifiers include full color capability, field of view, pixel resolution, see-through (transparency), brightness, dynamic gray scale, and power consumption level. Even after years of very competitive development, head-mounted displays based on refractive optics have a limited field of view and are not sufficiently compact and lightweight or comfortable.

Displays based on waveguide technology substrate guide displays have demonstrated the ability to meet many of these basic requirements. The concept has been around for over 10 years. Of particular relevance, how light can be coupled into a waveguide by using a diffractive element at the input, and how light can be coupled from the same waveguide by using a second diffractive element at the output. There is US Pat. No. 5,856,842 issued to Kaiser Optical Systems in 1999, which teaches what can be combined and released. According to US Pat. No. 5,856,842, light incident on a waveguide needs to be collimated to maintain its image content as it propagates along the waveguide. That is, the light must be collimated before it enters the waveguide. This can be achieved in various ways and is not relevant here. Using this design approach, the light exiting the waveguide is necessarily collimated, which is the state needed to bring the image into focus at infinity. Light propagates along the waveguide only over a limited range of internal angles. Light propagating parallel to the surface travels along the waveguide without being bounced (naturally). Light that does not propagate parallel to the surface travels along the waveguide while bouncing back and forth between the surfaces if the angle of incidence relative to the surface normal is greater than a critical angle. In the case of BK-7 glass, this critical angle is about 42 °. This critical angle can be slightly reduced by using a reflective coating (but unfortunately reducing the see-through performance of the substrate) or by using a high index material. In any case, the interior angle range in which light propagates along the waveguide does not change significantly. Therefore, in the case of glass, the maximum interior angle range is ≦ 50 °.
This translates into an angular range exiting the waveguide (ie, angles in the air), which is smaller than 40 ° and is generally smaller when other design factors are taken into account. To date, substrate guide optical element (SGO) technology has not been widely accepted. This is mainly due to the fact that waveguide optical elements can be used to enlarge the exit pupil, but these optical elements cannot be used to expand the field of view or improve the digital resolution. That is, the underlying physical process that constrains the range of internal angles that can undergo TIR within the waveguide limits the field of view that can be achieved using the waveguide optics to approximately 40 ° and the associated imaging device with the digital resolution that can be achieved. Limit it to that. Nevertheless, the appeal of compact and lightweight HMDs based on waveguide optics continues to arouse interest. One way to create a very large field of view is to divide the field of view into a set of smaller fields of view (each of which can be matched to the optical limits of the waveguide) and analyze the eye Displaying the small fields of view in time series sufficiently quickly to recognize the small fields of view as an integrated wide-angle display. One way to do this involves a holographic element that can be switched on and off continuously very rapidly, such as a switchable Bragg grating (SBG).

  The optical structural advantages of diffractive optical elements (DOEs), including the inherently efficient form factor and the ability to encode complex optical functions such as refractive power and diffusion into thin layers, are well known. Bragg gratings (commonly referred to as volume phase gratings or holograms) that give the highest diffraction efficiency have been widely used in devices such as head-up displays (HUD). An important class of Bragg grating devices is known as a switchable Bragg grating (SBG). SBG is a diffractive device formed by recording a volume phase grating or hologram in a polymer dispersed liquid crystal (PDLC) mixture. In general, SBG devices are manufactured by first placing a thin film of a mixture of photopolymerizable monomer and liquid crystal material between parallel glass plates or substrates. Techniques for forming and filling glass cells are well known in the liquid crystal display industry. One or both glass substrates support electrodes, typically a transparent indium tin oxide film, to apply an electric field across the PDLC layer. Other types of transparent conductive coatings may be used. The volume phase grating is then recorded by irradiating the liquid material with two mutually coherent laser beams that interfere to form the desired grating structure. During the recording process, the monomers polymerize and the holographic polymer dispersed liquid crystal (HPDLC) mixture undergoes phase separation, thereby forming a region that is densely packed by liquid crystal droplets interspersed with transparent polymer regions. The The fringe surface of the lattice is formed by alternately switching the liquid crystal rich region and the liquid crystal depletion region. The resulting volume phase grating can have a very high diffraction efficiency that may be controlled by the magnitude of the electric field applied across the PDLC layer. When an electric field is applied to a hologram (eg, a properly optimized hologram) via a transparent electrode, the natural directionality of the LC droplet is changed, thereby reducing the fringe's refractive index modulation and the hologram The diffraction efficiency drops to a very low level. It should be noted that the diffraction efficiency of the device can be adjusted over a continuous range using applied voltage from nearly 100% efficiency where no voltage is applied to nearly zero efficiency where a sufficiently high voltage is applied. SBG may be used to form transmissive or reflective gratings for free space applications. The SBG may be implemented as a waveguide device, in which case the HPDLC forms either a waveguide core or an evanescent coupling layer proximate to the waveguide. In one particular structure, referred to herein as a substrate guide optical element (SGO), parallel glass plates used to form the HPDLC cell provide a total internal reflection (TIR) light guide structure. . Light exits “coupled” from the SBG when the switchable grating diffracts the light at an angle that exceeds the TIR state. SGO is currently targeted in a range of display and sensor applications. While most of the previous work on HPDLC has been directed to reflection holograms, transmission devices have proven to be quite versatile as optical building blocks.

  In general, HPDLC used in SBG comprises a liquid crystal (LC), a monomer, a photoinitiating dye, and a coinitiator. The mixture often includes a surfactant. The patent and scientific literature includes many examples of material systems and processes that may be used to manufacture SBG. Two basic patents are US Pat. No. 5,942,157 by Sutherland and US Pat. No. 5,751,452 by Tanaka et al. Both of these applications describe combinations of monomers and liquid crystal materials that are suitable for manufacturing SBG devices.

  One of the known attributes of transmissive SBG is that the LC molecules tend to align perpendicular to the lattice fringe plane. The effect of LC molecular alignment is that transmissive SBG efficiently diffracts P-polarized light (ie, light having a polarization vector in the plane of incidence), while S-polarized light (ie, perpendicular to the plane of incidence). The effect is that the diffraction efficiency is almost zero with respect to light having a pole vector. In some cases, the transmission type SBG is not used at a grazing incidence. This is because the diffraction efficiency of an arbitrary grating in P-polarized light decreases to zero when the angle included between incident light and reflected light is small. Glass light guides in air propagate light by total internal reflection when the internal incident angle is greater than about 42 °. Thus, if the internal incident angle is in the range of 42 to about 70 °, the present invention may be implemented using a transmissive SBG, in which case the light extracted from the light guide by the grating is Mainly p-polarized. Typically, SBGs diffract when no voltage is applied, and sometimes switch to their optical passive state when a voltage is applied. However, the SBG can be designed to operate in a reverse mode so that the SBG diffracts when a voltage is applied and otherwise the SBG remains in an optically passive state. A method for manufacturing reverse mode SBG is described in US Provisional Patent Application No. 61/573, filed August 24, 2012 by the present inventors entitled IMPROVEMENTS TO HOLOGRAPIC POLYMER DISPRED LIQUID CRYSTAL MATERIALS AND DEVICES. , 066 specification. The same document also discloses how SBGs can be manufactured using flexible plastic substrates to provide the benefits of increased durability, reduced weight, and safety in near eye applications.

  In a previous application, the inventors analyzed the large field of view by dividing it into smaller fields of view (each of which can be matched to the optical element limitations of the waveguide) and the eye integrated these small fields of view. Disclosed are waveguide (SGO) displays that provide a large field of view by quickly displaying their small fields of view in time series. This process is sometimes referred to as field tiling. One way of doing this involves a holographic element that can be switched on and off continuously very rapidly. COMPACT HOLOGRAPIC EDGE ILLUMINATED EYEGLASS DISPLAY, a previous PCT application No. PCT / GB2010 / 000835 having an international filing date of April 26, 2010 by the inventors, which is hereby incorporated by reference in its entirety. (Also referred to by Applicant's serial number SBG073PCT), the inventors have provided a high resolution and ultra-wide field of view by stacking multiple SBGs together in the same waveguide and driving them rapidly and continuously. The method of tiling in time series is shown. Each partial field of view also has the full digital resolution of the associated imaging device, thereby allowing the formation of an image that approaches or exceeds the vision limit of the human eye. The tiling disclosed in this earlier application overcomes two defects of the standard waveguiding structure: limited field of view and limited pixel resolution, but this tiling is vertical and over a large field of view. There is a limit when you need to tile horizontally. For black and white displays with moderate FOV and magnification in only one direction, tiling can be achieved by simply laminating the lattice planes. However, when the field of view is magnified in both directions and colors are added, the number of layers required using this approach becomes immediately impractical. Each partial field is limited by the diffraction efficiency and angular bandwidth of the SBG. SBG grating devices generally have an angular bandwidth of about ± 5 ° in air (constrained by material properties, refractive index modulated beam morphology, and thickness). We have found that large angles can actually be achieved by using thinner SBGs, typically less than 3 microns. Increased bandwidth due to thinner SBGs results in even lower peak diffraction efficiency. Therefore, it is usually necessary to increase the refractive index modulation. One way to avoid the need to separate RGB SBGs is to use multiple SBGs, in which case illumination is done from both ends of the light guide as R illumination and B / G illumination, thereby The color gamut is somewhat impaired. However, multi-grating causes problems of manufacturing complexity and crosstalk.

  Superior to the tiling problem disclosed in the US provisional patent dated April 25, 2012 by the present inventors entitled WIDE ANGLE COLOR HEAD MOUNTED DISPLAY, also referenced by applicant's docket number SBG109 The solution is to compress the laminate by making the SBG interlaced or mosaic, as opposed to simply laminating the grid. The display disclosed in application 61 / 687,436 has two components: a multilayer waveguide device comprising a layer of mosaic SBG called DigiLens first, and Second, an optical system for providing input image data from one or more microdisplays referred to as an input image node (IIN), the input image node (IIN) being laser irradiated in addition to the microdisplay A module, a collimating relay optical element waveguide link, and a grating device. For purposes of describing the present invention, the same terminology is noted. In very basic terms, a DigiLens provides an eyepiece, while an IIN provides a compact image generation module that is generally positioned on the top or side of the DigiLens according to the ergonomic constraints of the application. In application 61 / 687,436, all SBG elements sharing a given prescription are driven simultaneously so that they diffract the collimated guided image light into a given FOV tile. The number of images that can be tiled is limited only by the input display refresh rate. SBG elements are typically a few millimeters in size. This approach achieves considerable savings with respect to layers, but illumination ripple due to the mosaic grid pattern used in DigiLens, scattering from the electrodes, and general optical and electrical complexity I am hit by a problem.

  The motivation behind this disclosure is to reduce the need to mosaic the DigiLens. A further problem with the prior art is that the coupling of the IIN output image to the waveguide is very inefficient, resulting in a thick waveguide. To overcome this problem, a more efficient method of sampling the input image field is needed.

  In view of the foregoing, the inventors have recognized and understood the advantages of a display, particularly a transparent display that combines a substrate guide optical element (SGO) and a switchable Bragg grating (SBG).

  Thus, in one aspect of some embodiments, a first optical substrate comprising at least one waveguide layer configured to propagate light in a first direction, the first optical substrate comprising: A first optical substrate comprising at least one grating lamina, wherein the at least one waveguide layer is configured to extract light from the first substrate along a first direction; and light in a second direction. A second optical substrate comprising at least one waveguide layer configured to propagate, wherein at least one waveguide layer of the second optical substrate transmits light from the second substrate in a second direction. There is provided an apparatus for displaying an image comprising a second optical substrate comprising at least one grating lamina configured to extract along. At least one grating lamina of at least one of the first and second optical substrates may comprise a passive mode SBG.

  In one embodiment, at least one waveguide of at least one of the first and second optical substrates comprises a plurality of grating laminae, and at least two of the plurality of grating laminae have the same surface grating frequency.

  In one embodiment, the at least one grating lamina of at least one of the first and second optical substrates is a non-switched Bragg grating recorded on the HPDLC material of at least one of the forward and reverse modes Is provided. The lattice sheet may be SBG, but in certain cases it need not be. Other types of suitable materials may be used.

  In one embodiment, the first and second optical substrates comprise passive mode SBGs.

  In one embodiment, at least one of the first and second optical substrates comprises a plurality of waveguide layers, each of the plurality of waveguide layers being red light, green light, blue light, blue / green mixed. It is configured to propagate at least one of light and one of a plurality of partial fields of view (FOV). In some cases, when at least one of the first and second optical substrates comprises a plurality of waveguide layers, and the plurality of waveguide layers comprises three waveguide layers, the three waveguide layers are Configured to propagate red light, green light, and blue light. Alternatively, when the plurality of waveguide layers include two waveguide layers, the three waveguide layers are configured to propagate red light and blue / green mixed light.

  In one embodiment, at least one waveguide layer of at least one of the first and second optical substrates comprises a hologram with different color prescriptions superimposed.

  In one embodiment, at least one waveguide layer on at least one of the first and second optical substrates is lossy.

  In one embodiment, at least one grating lamina of at least one of the first and second optical substrates has a thickness of less than about 3 microns. For example, the thickness may be less than about 2.5 microns, 2 microns, 1.5 microns, 1.2 microns, 1 micron, 0.5 microns, or less.

  In one embodiment, at least one grating lamina of at least one of the first and second optical substrates has a thickness that varies along a respective light propagation direction.

  In one embodiment, the apparatus described herein is part of a device, and the device is part of at least one of HMD, HUD, and HDD.

  In another aspect of some embodiments, an apparatus for displaying an image, the input image node for providing image modulated light, and at least configured to propagate the modulated light in a first direction A first optical substrate comprising one waveguide layer, wherein at least one waveguide layer of the first optical substrate is configured to extract modulated light from the first substrate along a first direction. A second optical substrate comprising: a first optical substrate comprising at least one grating thin plate; and a second optical substrate comprising at least one waveguide layer configured to propagate modulated light in a second direction; An apparatus comprising: at least one waveguide layer of the substrate; and a second optical substrate comprising at least one grating lamina configured to extract modulated light from the second substrate along a second direction. Provided. At least one grating lamina of the first optical substrate may be configured to couple the modulated light to the first substrate. At least one grating lamina of the second optical substrate may be configured to couple the modulated light extracted from the first substrate to the second substrate. At least one grating thin plate of at least one of the first and second optical substrates may have a k vector that varies along the respective light propagation direction.

  In one embodiment, the input image node comprises at least one of a microdisplay, a laser, and collimating optics. The microdisplay may be any commonly used type of microdisplay including, for example, radioactive microdisplays. The emissive microdisplay may be OLED, QPI, and the like.

  In one embodiment, at least one grating lamina of at least one of the first and second optical substrates has a varying thickness. For example, the thickness may increase in a direction that is at least one of (i) parallel to the light propagation direction and (ii) perpendicular to the light propagation direction. Alternatively, the thickness may decrease after increasing along the aforementioned direction (or vice versa). The geometric form is not limited.

  In one embodiment, at least one grating lamina of at least one of the first and second optical substrates comprises an SBG that is in a switching mode or a passive mode.

  In one embodiment, the at least one grating lamina on at least one of the first or second substrates comprises a multi-grating of at least two different monochromatic recipes.

  In one embodiment, the apparatus comprises a plurality of grating lamellas having the same surface grating frequency but different k vectors, wherein the plurality of grating lamellas are configured to divide the input image field into a plurality of angular intervals. The

  In one embodiment, at least one of the first and second optical substrates is curved in at least one orthogonal plane.

  In one embodiment, the light extracted from the first and second substrates provides uniform illumination in any viewing direction.

  In another aspect of some embodiments, a method of displaying an image comprising coupling modulated light from an input image to a first optical substrate; extracting light from the first substrate; Coupling the light extracted from the first substrate to the second substrate. The first optical substrate may comprise at least one waveguide layer configured to propagate light in the first direction, and the at least one waveguide layer of the first optical substrate transmits light in the first direction. At least one grid lamina configured to extract from a substrate along a first direction. The second optical substrate may include at least one waveguide layer configured to propagate light in the second direction, and the at least one waveguide layer of the second optical substrate transmits light to the first At least one grid lamina configured to extract from a second substrate along a second direction. At least one grating lamina of at least one of the first and second optical substrates may comprise a passive mode SBG.

  In one embodiment, the method further comprises sampling the input image into a plurality of angular intervals, each of the plurality of angular intervals having an effective exit pupil that is a portion of the overall pupil size. In one aspect, this surprisingly provides the advantage that the thickness of the first waveguide can be significantly reduced compared to existing devices. Thus, the size and placement of the input grid can be beneficially affected.

  In one embodiment, the method includes at least one of at least one of the following: a grating thickness, a refractive index modulation, a k-vector rotation, of at least one of the first and second optical substrates. The method further includes improving the display of the image by changing at least one of the profile, the surface grating period, and the hologram substrate refractive index difference.

  In another embodiment, an apparatus for displaying an image, comprising: an input image node for providing image modulated light; first and second optical waveguide substrates; and image modulated light on the first substrate. An apparatus is provided comprising first optical means for coupling to and second optical means for coupling light extracted from the first substrate to the second substrate. The first optical substrate comprises at least one waveguide layer that propagates light in a first direction. Each waveguiding layer includes at least one grating lamina adapted to extract light from the first substrate, the light extraction taking place along the first direction. The second optical substrate includes at least one waveguide layer. Each waveguiding layer propagates light in the second direction. Each waveguiding layer includes at least one grating lamina adapted to extract display light from the second substrate, the light extraction taking place along the second direction. In one embodiment, the first optical substrate selectively samples portions of the image modulated light, each portion being characterized by either an angular region or a spatial region.

  Needless to say, all combinations of the aforementioned concepts with further concepts described in more detail below (as long as such concepts do not contradict each other) are part of the subject matter of the invention disclosed herein. Is considered. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It is also to be understood that the terminology explicitly used herein, which may appear in any disclosure incorporated by reference, has the meaning most consistent with the specific concepts disclosed herein. Should be given.

  As will be appreciated by those skilled in the art, the drawings are primarily for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily drawn to scale, and in some cases, various aspects of the inventive subject matter disclosed herein are shown in the drawings to facilitate understanding of different features. It may be shown exaggerated or enlarged. In the drawings, like reference numbers generally indicate similar features (eg, functionally similar and / or structurally similar elements).

FIG. 1A is a schematic diagram of the optical structure of a Bragg grating in the tangential plane. FIG. 1B is a schematic view of the optical structure of a Bragg grating in the sagittal plane.

FIG. 2A is a schematic side view showing a first operating state in one embodiment. FIG. 2B is a schematic side view illustrating a second operating state in one embodiment. FIG. 2C is a schematic front view of one embodiment.

It is a schematic three-dimensional view of the components of one embodiment.

2 is a schematic side view of components of one embodiment. FIG.

6 is a flowchart illustrating image formation in one embodiment.

1 is a schematic side view of one embodiment.

1 is a schematic side view of one embodiment.

1 is a schematic side view of one embodiment.

It is a chart which shows the diffraction efficiency characteristic of one embodiment.

1 is a schematic cross-sectional view of a horizontal beam expander in one embodiment.

6 is a table giving diffraction efficiency characteristics of SBG used in one embodiment.

FIG. 12A is a schematic three-dimensional view showing a first operating state of one embodiment. FIG. 12B is a schematic three-dimensional view showing a second operating state of one embodiment.

FIG. 13A is a schematic three-dimensional view showing a third operating state of one embodiment. FIG. 13B is a schematic three-dimensional view showing a fourth operating state of one embodiment.

FIG. 14A is an impression of an expert in the first orientation of the HMD device of the present invention. FIG. 14B is an impression of a second orientation expert of the HMD device of the present invention. FIG. 14C is an impression of a third orientation expert of the HMD device of the present invention.

1 is a schematic cross-sectional view of a wedge-shaped waveguide grating used in one embodiment. FIG.

1 is a schematic side view of one embodiment.

It is a chart which shows the diffraction efficiency versus angle characteristic of one embodiment.

1 is a schematic side view of one embodiment.

FIG. 19A is a schematic side view illustrating a first operational state of one embodiment. FIG. 19B is a schematic side view illustrating a second operational state of one embodiment.

FIG. 20A is a schematic side view illustrating a first operational state of an input image node in one embodiment. FIG. 20B is a schematic side view illustrating a second operational state of the input image node in one embodiment.

It is a schematic plan view of HBE containing the inclined lattice stripe.

FIG. 3 is a schematic three-dimensional view of one embodiment using HBE with tilted plaid.

FIG. 23A is a schematic side view illustrating a first operational state of a HUD provided by one embodiment. FIG. 23B is a schematic side view illustrating a second operational state of the HUD provided by one embodiment.

1 is a schematic side view of a HUD provided by one embodiment. FIG.

1 is a schematic side view of a HUD provided by one embodiment. FIG.

1 is a schematic view of a prior art collimated image display. FIG.

1 is a schematic side view of a HUD according to the principles of the present invention.

It is a schematic side view of a holographic mirror.

1 is a schematic side view of a HUD provided by one embodiment. FIG.

1 is a schematic side view of a HUD provided by one embodiment. FIG.

1 is a schematic side view of a HUD provided by one embodiment. FIG.

FIG. 32A is a three-dimensional view of a color display provided by one embodiment. FIG. 32B is a chart showing the spectral characteristics of a light source used in a color display provided by one embodiment. FIG. 32C is a table showing the spectral characteristics of the light sources used in the color display provided by one embodiment.

It is sectional drawing of HUD integrated in the windscreen in one embodiment of this invention.

It is sectional drawing of HUD integrated in the windscreen in one embodiment of this invention.

FIG. 3 is a three-dimensional view of a display provided by one embodiment.

FIG. 3 is a three-dimensional view of a display provided by one embodiment.

1 is a schematic side view of a color display provided by one embodiment. FIG.

FIG. 3 is a schematic three-dimensional view of a color display provided by one embodiment.

FIG. 39A is a schematic side view of one embodiment. FIG. 39B is a schematic front view of one embodiment.

It is sectional drawing of HUD integrated in the windscreen in one embodiment.

It is a flowchart which shows the image formation in HUD of one Embodiment.

FIG. 42A is a chart showing first diffraction efficiency versus angular characteristics of a multiple digi lens in one embodiment. FIG. 42B is a chart showing second diffraction efficiency vs. angle characteristics of the multiple digi lens in one embodiment.

FIG. 2 is a schematic three-dimensional view of a color multiplex display in one embodiment.

It is a schematic side view of the DigiLens used in the color multiplex display in one embodiment.

FIG. 3 is a three-dimensional view of one embodiment of a display in one embodiment in which three HBE waveguides and three DigiLens waveguides are provided.

It is a schematic side view which shows formation of the projection stop by IIN.

It is a schematic plan view showing the coupling of light from the IIN to the HBE waveguide.

48 shows details of the HBE waveguide of FIG. An image input that shows the interaction between the beam and the grating.

It is a schematic sectional drawing of 4 layer HBE in one embodiment.

FIG. 50 is a table showing a grid used in the embodiment of FIG. 49.

FIG. 50 is a chart showing a polymerization DE versus angle profile in the embodiment of FIG. 49. FIG.

FIG. 3 is a three-dimensional view of a wedge SBG grating in one embodiment.

FIG. 53A is a schematic diagram of a first operational state of an HBE in one embodiment. FIG. 53B is a schematic diagram of the second operational state of the HBE in one embodiment. FIG. 53C is a schematic diagram of a third operational state of the HBE in one embodiment.

FIG. 54A shows a projection scheme in one embodiment that does not result in a projection pupil of the type described earlier in the specification, where the pupil is formed inside the projection lens. FIG. 54B shows a projection scheme in one embodiment that does not result in a projection pupil of the type previously described herein, formed in front of a projection lens that uses a stop 562.

FIG. 6 shows a schematic diagram of the use of a rotating k-vector grating to maximize the in-coupled light peak DE in one embodiment.

FIG. 6 shows a schematic diagram illustrating exemplary ray propagation through a waveguide portion 580 that includes a rotated k-vector grating in one embodiment.

FIG. 6 shows a top view showing HBE590 and VBE591 in one embodiment.

FIG. 3 shows a schematic side view of HBE and VBE in one embodiment.

FIG. 6 shows an exploded view of HBE showing beam propagation inside a waveguide in one embodiment.

1 illustrates an apparatus for manufacturing HBE using a contact printing process in one embodiment.

FIG. 61A shows a Z = L end cross-section of HBE590 with the wide end of the cone-shaped lens in one embodiment positioned on the upper side. FIG. 61B shows a plan view of a lens in one embodiment. FIG. 61C shows the Z = 0 end of the HBE with the narrow end of the lens in one embodiment positioned on the upper side.

FIG. 62A shows the formation of a conical section from the cone at the apex 620 and base 621, with the cone shown in side view. FIG. 62B shows the formation of a conical section from the apex 620 and the base 621 cone, with the cone shown in front view. FIG. 62C shows the formation of a conical section from the cone of apex 620 and base 621 where a view of the cutting optics projected from the base along the cut line is shown.

1 shows the basic structure of a waveguide in one embodiment.

It is a figure of the waveguide by which the input gratings 635A-635C are laminated | stacked. In one embodiment, each lattice has a unique k vector 636A-636C.

FIG. 5 illustrates that in one embodiment the input gratings are arranged adjacent to each other along the waveguide propagation direction.

FIG. 6 illustrates that in one embodiment the principles shown in FIGS. 64-65 may be applied to the output grating.

2 is a flowchart representing a process of one embodiment.

Fig. 4 shows a ray trace of a monochromatic version of the structure in one embodiment.

FIG. 64 shows the approximate dimensions of the IIN of FIG. 63 in one embodiment.

FIG. 64 provides a development view of the optical layout of FIG. 64 in one embodiment.

FIG. 71A shows the formation of a projection stop inside the HBE in one embodiment using a simplified thin lens representation of the microdisplay projection optics. FIG. 71B shows the formation of a projection stop inside the HBE in one embodiment using a simplified thin lens representation of the microdisplay projection optics.

FIG. 6 shows one embodiment where the HBE is provided with a coupling grid at its input and the alternating SBG stripes of two different prescriptions are tilted at 45 °.

FIG. 6 shows beam propagation from an IIN through a single layer of DigiLens showing four direction changes that occur along the path to the exit pupil in one embodiment.

FIG. 6 shows a plan view of a near eye configuration of a proposed helmet mounted display in one embodiment.

FIG. 6 shows a side view of the near eye configuration of the proposed helmet mounted display in one embodiment.

FIG. 6 shows a front view of the near eye configuration of the proposed helmet mounted display in one embodiment.

FIG. 6 shows the relationship of FOV, pupil distance, and DigiLens® aperture to eyebox in one embodiment. FIG.

Fig. 4 shows partial binocular overlap in one embodiment.

Fig. 6 shows partial binocular overlap in another embodiment.

1 illustrates a transparent waveguide display in one embodiment.

  Hereinafter, various concepts related to the transparent display of the present invention and embodiments of the transparent display of the present invention will be described in more detail. Of course, since the disclosed concepts are not limited to any particular embodiment, the various concepts introduced above and the various concepts discussed in more detail below may be implemented in any of a number of ways. . Examples of specific implementations and uses are given primarily for illustrative purposes.

  The present invention will now be further described by way of example only with reference to the accompanying drawings. As will be appreciated by one skilled in the art, the present invention may be practiced with some or all of the invention disclosed in the following description. For the purpose of illustrating the present invention, well-known features of optical technology known to those skilled in the art of optical design and visual display have been omitted or simplified so as not to obscure the basic principles of the present invention. . Unless otherwise stated, the term “on-axis” with respect to the direction of a ray or beam refers to propagation parallel to an axis perpendicular to the surface of the optical component described in connection with the present invention. It is. In the following description, the terms light, light beam, beam, and direction may be used interchangeably with each other to indicate the direction of propagation of light energy along a linear trajectory. Some of the descriptions below are given using terminology commonly used by those skilled in the art of optical design. It should also be noted that in the following description of the present invention, repeated use of the phrase “in one embodiment” does not necessarily refer to the same embodiment.

  The present invention provides two basic properties of SBG that have not been used so far: first, a relatively wide angular bandwidth of a Bragg grating in a plane orthogonal to the diffractive surface; , And the wide angular bandwidth that results from making the SBG very thin. As a result, the constraint that limits the size of the FOV tile to about 10 ° × 10 ° is not applied in this case, which results in the mosaic approach described above. Here, as a result, fewer, larger tiles can be used. As will be shown in the following description, the required FOV may be divided into two tiles, each having one DigiLens. Other numbers of tiles may be possible. With respect to optical design, this new approach can minimize the problem of illumination ripple, if not completely eliminated. By making the DigiLens passive, it is possible to avoid the problem of scattering from the electrodes and the non-light problem of connecting wires to a large matrix of mosaic elements. A passive SBG is not different from a switched SDBG with respect to its HPDLC formation and recording process. The only difference is that no electrode is required. The diffraction characteristics of SBG are usually specified in the tangential plane. In a grating structure for diffracting light in one plane, the tangent plane is a plane including a light vector and a grating vector that are incident and diffracted. According to geometrical optical theory, the plane perpendicular to the tangent plane is called the sagittal plane. FIG. 1 shows a basic geometric optical element of a transmissive SBG 90 that includes an inclined fringe such as 91, where the grating vector K is aligned perpendicular to the fringe. In a Bragg grating, a large number of input rays and output rays satisfy the Bragg condition if the angle between the incident ray, the k vector diffracted ray and the K vector satisfies the Bragg equation. (Note that, indeed, according to the cogelonic theory of Bragg gratings, fairly high diffraction with small angular or wavelength shift from the on-Bragg ray direction is obtained at off-Bragg angles). In FIG. 1, these off-bragg rays are indicated by ray cones 902 and 903 that surround on-bragg rays 900 and 901 (in the plane of the drawing). As shown in FIG. 1A, the locus of the on-Brag ray fringe intercept is a circle 904. As shown in FIG. 1B, rays 905 and 906 are also on-braggs. Considering the geometry of FIG. 1A, it goes without saying that the Bragg diffraction angular bandwidth in the tangent plane is limited by the projection of the cones 902, 903 onto the tangential plane. However, as is apparent with reference to FIG. 1B, the effective angular bandwidth (“ABW”) in the sagittal plane is very large, which is given by the projection of the cone 904 into the sagittal plane. In practice, the sagittal bandwidth is limited primarily by the TIR angle constraints set by the waveguide. As a result of the angular bandwidth (typically about 4 x tangential bandwidth) of the large sagittal plane (ie, the horizontal plane for our purposes) of the Bragg grating, the current horizontal FOV target is achieved in most display applications it can. In practice, the bandwidth is limited only by the TIR angle range that can be maintained in the waveguide.

  The inventors have already demonstrated that a thin SBG grating provides a very wide angular bandwidth. Experimental SBG waveguides fabricated using low index modulation SBG RMLCM formation have been found to have a 21 ° FWHM bandwidth with a 1 micron thick SBG layer.

  In the following description, many references will be made to a grating that should be understood to generally mean a Bragg grating, preferably SBG. In many cases, SBGs are operated in their normal switching mode as described above. However, in some cases, the SBG is used in a passive (eg, fully passive) mode, ie, the SBG cannot be switched. Non-switching SBGs are superior to conventional passive holograms. This is because the LC component of HPDLC provides significantly higher refractive index modulation than can be achieved with conventional holographic photopolymers. In certain embodiments of the invention, the display uses a mixture of switched and non-switched SBGs. However, the DigiLens output grating is always in a passive state (not switched). In one particular class of embodiments, all displays use passive SBGs.

  A transparent display according to the principles of the present invention is schematically illustrated in FIG. DigiLens® with a thin and highly transparent eyepiece (or HUD combiner) has two waveguides 101 for projecting the upper half and the lower half of the field of view into an eyebox (not shown). 102. Each waveguide comprises a non-switchable SBG layer sandwiched between transparent substrates. Each waveguide has a switchable input grating, designated DIGI-I1, DIGI-O1 and DIGI-I2, DIGI-O2, also indicated by numerals 107, 109 and 108, 110, respectively, and a non-switchable (passive) output. And a lattice. The waveguides are separated by a half-wave film (HWF) 106. (Note that in other embodiments to be described below, the HWF is placed between the DIGI-I gratings and the DIGI-O gratings are separated by air (or a low index material)). The input image node (IIN) 103, discussed below, includes a microdisplay, a laser module, beam expanding optics, collimating optics, and relay optics. A schematic side view is given in FIGS. 2A and 2B, and a front view is given in FIG. 2C. 2A and 2B show the ray path from the IIN through the DigiLens layer for the two switching states of the display. In the first state, the grating DIGI-I 1 is active and diffracts the incident P-polarized light 1000 from the IIN 103 into the TIR path 1001. TIR light is diffracted out of the waveguide along the light, as indicated by 1002. The output grating is lossy, i.e. the diffraction efficiency is much less than 1, so that part of the guide light is diffracted out by each beam-grating interaction. The remaining light continues to undergo TIR and diffraction repeatedly until all the light is extracted from the waveguide. Careful optimization of diffraction efficiency (depending on refractive index modulation, grating thickness, and other parameters) achieves uniform illumination across the output aperture. Generally, the lowest diffraction efficiency is required at the end of the waveguide closest to the IIN, and the highest efficiency is required at the forefront. Note that due to lossy extraction, more peak energy (at an angle of 0 °) is coupled to the DigiLens than at higher angles. Therefore, a wide angle of light is available for extraction at the end of the lossy grating. The phrase “lossy grating” is used in some embodiments, but this phrase encompasses “lossy waveguides”. While not to be bound by any theory, this is because “lossy” may be due to not a combination of waveguiding and grating efficiency that can result in uniform loss along the waveguide.

  This helps to equalize peak and edge angle changes, especially at the thick end of the waveguide where the DE curve is narrowed. The polarization of the diffracted light 1002 is rotated by 90 ° (becomes S-polarized) by the HWF, and therefore passes through the second waveguide 102 without being biased. This is because SBG has a relatively low DE for S polarization. One DigiLens (registered trademark) layer emits S-polarized light, and the other DigiLens layer emits P-polarized light. However, each SBG layer is P diffracted.

  A horizontal beam expander (HBE) indicated by the displays HBE1, HBE2 (also referred to by the numbers (104, 105)) is a multilayer SBG waveguide that uses a lossy high ABW grating to expand the image light over a large pupil. It is a waveguide. In the embodiment described above, the HBE extends along the upper edge of the DigiLens. HBE is discussed in more detail below. There is a gap between the front DigiLens (registered trademark) element and the rear DigiLens (registered trademark) element. This may be replaced by a suitable material with a low refractive index (close to 1). When the output image light is a mixture of P-polarized light and S-polarized light, it is necessary to provide a 1/4 wavelength film on the output surface of the DigiLens for compatibility with Polaroid (registered trademark) eyewear There is. Otherwise, you lose half your vision.

  Although attached to HBE (and earlier VBE), the terms horizontal and vertical in this context only are important for purposes of describing the present invention. Indeed, the present invention allows many different forms of comments and allows several different implementations where the beam making up the beam expansion may be vertical or horizontal. With respect to the term waveguide, it should be noted that they may comprise a plurality of separate waveguides that are actually stacked in layers. Finally, with respect to lattice elements, each of the three lattice elements may include a plurality of layered lattice stacks arranged adjacent to form a single layer or holographically multiplexed to form a single layer. Needless to say. The basic building block of the display disclosure is a waveguide containing a grating, usually a Bragg grating. Of course, the function may be achieved with only one waveguiding layer in certain embodiments. However, the number of waveguiding layers depends on the size of the field of view and the required color. The grid may be switchable (SBG) or may be passive, i.e. not switchable. In principle, any type of Bragg grating may be used to provide a passive grating. There are significant advantages to using SBG without an electrode. SBG materials have the advantage that mixing LC and polymer gives a higher refractive index modulation than that of conventional holographic polymer materials. In a preferred embodiment of the present invention, the output waveguide component uses only non-mosaic passive gratings. This minimizes the possible problems of electrode scattering and illumination non-uniformity. The term lattice is used to denote a Bragg lattice unless specified otherwise. Passive grating means a grating that is not electrically switched.

  3 and 4 show the display in more detail. As a further aid in understanding how collimated displays (eg, HMDs) work, the initial focus is focused on the black and white version of the design. Structurally, the black and white and color implementations of HMD are very similar. Needless to say, an important difference can be achieved in that the black and white configuration can be used with fewer waveguiding layers and the possibility of using several passive grating components in IIN and HBE, whereas the color implementation is red, green And, because it is very difficult to manage the angular content of the blue light channel simultaneously, it requires most of the components of IIN and HBE to be switchable. In both cases, the DigiLens® remains a passive component.

The present invention has many applications in the field of transparent visual displays, but first considers a helmet mounted display in one particular application, namely augmented reality (AR) applications. The purpose in this case is a 52 ° H × 30 ° V monocular field of view while achieving all of the original goals of high transparency, high resolution, ultra-compact (thin) form factor, light weight, and sufficient exit pupil. Meet the specification. The target specifications are summarized in Table 1.

  The important components of the display are shown in the schematic three-dimensional view of FIG. 3 and the side view of FIG. The display divides the FOV into upper FOV tiles and lower FOV tiles (indicated by reference numerals 1 and 2 in the drawing display). Note that the Digilens waveguide substrate and HBE components are not shown for the sake of simplicity. The display includes a DigiLens (registered trademark) composed of two waveguide layers sandwiching the HWF, and the DigiLens is divided into an input component DIGI-I and an output component DIGI-O. Note that the wide sagittal angular bandwidth of the SBG eliminates the need to tile the tiles horizontally. Two horizontal beam expanders HBE with an input grating HBE-I and an output grating HBE-O are respectively provided. The expanded output light from the HBE-O1 enters the first daisy lens waveguide via the DIGI-I11, and the same applies to the second waveguide. In FIGS. 3 and 4, the components are also referred to by numerals 130-145. Two IINs are provided, one for the upper FOV and one for the lower FOV. The display panel in each IIN is a 1080p 5 mm × 3 mm LCoS device. One laser module may be used to illuminate both display panels. However, the present invention does not limit the number of microdisplays to be used. A single microdisplay with a sufficiently fast refresh rate and a sufficiently high resolution would be sufficient for all display applications except the most demanding display applications.

  DIGI-I is the most challenging grid in the system because it requires high input coupling efficiency over the entire angular range at the pupil output point projected from HBE-O. The DIGI-I grating switches, thereby sampling the 52 ° horizontal × 30 ° vertical field of view output to the two DigiLens waveguides by HBE-O. It is desirable that this grating requires a high angular bandwidth and a high DE. DIGI-I comprises two SBGs each operating over an 8.5 ° angular bandwidth overlap to provide at least 15 °. DIGI-I uses two 3 micron SBGs with a DE of about 87% with an angular bandwidth of 8.5 ° to 9.0 ° in air. The vertical field of view of -15 ° to 0 ° is switched by DIGI-I1, and the vertical field of view of 0 ° to + 15 ° is switched to DIGI-2. Therefore, DIGI-I1 gives 52 ° horizontal × −15 ° vertical, and DIGI-I2 gives 52 ° horizontal × + 15 ° vertical. All gratings in DIGI-O are passive and can therefore be thin gratings. One of each pair is for red and the other pair is for blue / green. The DIGI-O1 or rear grid giving the lower 15 ° and the front grid or DIGI-O2 giving the upper 15 ° gives a total of 52 ° horizontal × 30 ° vertical. As shown in FIG. 4, DigiLens® is tilted at a rake angle of ˜8-10 °. This is found from ray tracing analysis to give a better DE than simply projecting image light vertically onto a DigiLens.

  A flow chart representing the interaction between IIN, HBE and DigiLens in the image forming process is given in FIG. Because the diffractive optical element is dispersive, it is desirable to configure the gratings in a complementary manner so that the dispersion caused by the gratings is canceled when multiple gratings are combined. Complementarity is typically achieved by designing the gratings to have the same grating pitch (ie, the spatial frequency at the intersection of the Bragg grating and the substrate is the same). In the above-described embodiment, HBE-I2 and HBE-O2 need to be complementary. However, HBE-I1 and HBE-I2 need not be complementary.

  In one embodiment shown in FIG. 6, the HWF between the DigiLens waveguides (overlapping with the DIGI-O grating) is removed and the HWD is inserted into the space between the DigiLens DIGI-I input gratings. The void left by the HWP may be filled with a low refractive index nanoporous material. A quarter-wave film (QWF) is attached to the front and back waveguide facing surfaces 157, 158 so that each TIR bounce results in a 90 ° polarization rotation, thereby allowing a grating that is about four times thinner Thus, the interaction between the front DigiLens (registered trademark) and the rear DigiLens (registered trademark) can be eliminated. FIG. 7 shows the propagation of the upper and lower FOV light in the two DigiLens waveguides represented by the ray paths 1010, 1012, 1014 and 1011, 1013, 1015 in the first waveguide. The components shown in FIGS. 6 and 7 are also referred to by numerals 150-159. FIG. 8 is a diagram of one of the DigiLens waveguides 160 showing the function of the QWF layer 162 in more detail. Input light from the HBE 1020 is deflected to the TIR path 1021 by the DIGI-I grating 161. Rays such as 1022 incident on the QWF coating have their polarization converted from P-polarized light to circularly polarized light in a first direction. At the time of reflection, the polarized light remains circularly polarized, but in the opposite direction, so that after passing through the QWF, the second light appears as S-polarized light 1023. S light is not diffracted by the SBG and therefore continues to undergo TIR. At the next reflection at the QWF film, the light is converted to P-polarized light 1024, which is off Bragg relative to DIGI-I and therefore is not diffracted towards the original HBE. Thereafter, the TIR of the beam proceeds to the DIGI-O grating, where the TIR of the beam is gradually extracted from the waveguide described above.

  In one embodiment, two stacked DIGI-I gratings may be provided in each DigiLens waveguide to increase the angular bandwidth. FIG. 9 shows individual DE angles to form an upper and lower FOV of about 15 ° (FWHM) in air using two grids with an angular bandwidth of 8.5 ° (FWHM) in air. It is a chart which shows the effect which combines a bandwidth. In other embodiments of the present invention, the DigiLens can comprise more layers, for example three DIGI-I layers combined with two DIGI-I layers in each waveguide. The DIGI-I lattice and the DIGI-O lattice need not be on the same plane. However, for manufacturing, it is beneficial to limit the number of gratings, substrates, electrode layers, and low index material layers in order to minimize material costs and process steps.

  FIG. 10 shows the HBE for the DigiLens 170 in cross section. There are two HBE waveguides 171, 172, each HBE waveguide 171, 172 having three stacked gratings (HBE-I1A-C and HBE-I2A-C) and two lossy output gratings (HBE). -O1A-B and HBE-O2A-B). The HBE is coupled to the DigiLens 170 and two IINs (IIN1 and IIN2) are provided. The path of light from the IIN to the DigiLens is indicated by light rays 1030, 1031, 1034 and 1032, 1033, 1035. Components are also referenced by the numbers 170-183. Each LCoS gives an FOV of 26 ° H × 30 ° V. Each HBE-I includes three gratings that act on P-polarized light in 8.5 ° ABW steps to give a 26 ° half horizontal field of view. The 30 ° field of view is combined in its entirety due to the great increase in ABW in the sagittal plane. HBE-I SBG is a thick grid that allows high DE but narrow ABW. Two HBE-I implementation options: firstly lower DE, 26 ° H sampled by two HBE-I gratings giving higher duty cycle SBG, or secondly 3 × 8. Consider 26 ° H sampled by three HBE-I gratings giving a 5 ° angular bandwidth. This gives a higher DE, lower duty cycle SBG. The grating generally has a thickness of 1-2 microns and is lossy so that light is extracted with uniform efficiency along the length of the grating. The lossy grating has a large ABW and a low DE. The lattices of HBE-I1 and HBE-I2 need not be complementary (ie, chromatic dispersion correction). The lattices of HBE-I1 and HBE-O1 (and HBE-I2 and HBE-O2) need to be complementary. In passive HBE-I, a single switched grating needs to be thin to obtain a higher angular bandwidth. With current materials, the current material has a peak DE of about 30% and 60% is within the range where the expected material improvement can be obtained. In the case of switched HBE-I, a thicker grating with a reduced angular bandwidth can be obtained. Using current material refractive index modulation, the grating thickness is increased from 1.4 microns to 2.0 microns, so the angular bandwidth is almost halved and the DE is doubled. The typical DE and ABW characteristics for thin and thick SBGs are summarized in the table of FIG.

  12 and 13 provide a step-by-step description of the process of projecting image light from one (left eye) IIN to an eyebox that provides ± 15 ° vertical field of view and 0 ° -26 ° horizontal field of view. The components are the same as those shown in FIGS. FIG. 12A shows a path 1040 from the LCoS panel to the output of the IIN. FIG. 12B shows the light path through the HBE representing the TIR path 1042 in one waveguide and the light extraction 1043 along its length. FIG. 13A shows the coupling of light 1044 extracted from HBE (via DIGI-I) to the DigiLens. Finally, FIG. 13B shows the downward propagation of light 1045 in the digi lens, where the output image light 1046 provides the lower half of the FOV.

  14A-14C show three 3D views of the above-described invention as implemented in HMD 190. FIG. Three different perspective views 191-193 are shown. The display module includes a horizontal hinge 194. In the deployed position, the user can see through the entire view with high transparency. In the storage position, the user is free to use a distance meter, night vision system, or other such equipment. As shown, the spectacle wearer is accepted and the design can also accept the use of Polaroid® eyewear. In another embodiment, a simple display pull-in mechanism can hide the display in a compact module under the helmet forehead when not in use. In yet another embodiment of the invention, the display is pulled vertically into the helmet when not in use. The presently preferred implementation uses a custom helmet, which is coupled to the belt pack via a feed fiber optic communication link and a feed connection. For training applications, the belt pack is connected wirelessly to the training center.

  An important feature of the optical design is that the grating used in one or both of the HBE and DigiLens is a tailored DE profile obtained by varying the grating thickness along the propagation direction as shown in FIG. It is a point which has. The wedge-shaped lattice 203 is provided by including a small wedge in the lattice substrate 201. The second substrate 202 may be rectangular. Other ways of obtaining a wedge grating will be apparent to those skilled in the art of optics. If two stacked gratings are used, the DE profiles of the two gratings extend in opposite directions. Desirably, the grating thickness may vary from 1.0-1.2 microns up to 2.8-3.0 microns, with the lower thickness being the largest bandwidth in a given output direction 1053 And the lowest DE. A higher thickness results in the lowest bandwidth 1050 and higher DE in a given output direction 1051. Note that the wedge angle is very small and has minimal impact on illumination uniformity and image quality.

  A refractive index of about 1.585 is required to support a waveguide TIR angle of generally less than 70 ° relative to the TIR surface. In general, it is desirable to limit the use of higher angles in the waveguide to avoid a reduction in the interaction between the outcoupling grating and the light flux, which creates gaps in the waveguide. Higher angles (about 85 °) can lead to image folding when the grating is formed to give a very high angular bandwidth. Polycarbonate allows a TIR angle of up to about 72 °.

  Black and white displays can be achieved with almost passive grating components, but for full color displays, HBE-I and HBE-O and DigiLens input grating DIGI-I are active, in which case the only passive The grid is the output grid DIGI-O. A further difference between black and white HMDs and color HMDs is that in the latter, separate waveguides are used in HBE to cover the red and blue / green wavelengths. FIG. 16 shows a DigiLens used in one embodiment of the present invention for a color display with two DigiLens doublet waveguides. Each doublet waveguide is similar to the embodiment of FIGS. However, in each DigiLens waveguide doublet, one of the waveguides acts on the red light and the second waveguide acts on the mixture of blue light and green light. In each doublet, the red lattice is arranged after the B / G lattice, that is, close to the eye. The input and output DigiLens gratings are represented by DIGI-IR and DIGI-OR for red doublets and DIGI-IB / G and DIGI-OB / G for blue / green doublets. Is represented by The output grating portion of the waveguide sandwiches the HWF. The input grating portion may have a gap in between as shown, or preferably a low refractive index material in between. QWF may be applied to the opposing surface of the waveguide in each doublet. The components are also numbered 210-227. The red waveguide and the blue / green waveguide are optically separated by air or a low refractive index (approximately 1) material such as mesoporous silica (not shown), which will be described later. The HWF converts the rear output from P to S. Since the SBG grating has good P sensitivity, this prevents recombination of the front grating and light. The rake angle (8 ° -10 °) gives a higher angular bandwidth and a lower chromatic dispersion that allows sharing of the blue / green lattice. In most cases, color images may require a high index substrate and a special coating to increase the blue TIR angle range.

  The ray path for red light is indicated by rays 1071, 1073, 1075. The ray path for blue / green light is indicated by rays 1070, 1072, 1074. As shown in the drawing, a portion of this light couples into the second waveguide doublet, ie, the optical path indicated by 1076, 1078 (blue / green) and 1077, 1079 (red). In our HMD structure, the risk that light diffracted from the rear waveguide interacts with light entering the upper layer and couples back into the original waveguide is avoided. The red and blue / green gratings do not cross-couple due to polarization management. Each color channel may cross-couple with itself. However, this is mitigated by the TIR occurring in the forward grating and the interdependence that ensures that the outcoupling is in the correct output direction. The front and back outcoupled beam offset due to the staggered path helps to uniform the output light. The impact on the throughput of the light that is recombined into the original DigiLens® is negligible. To provide an exemption from lattice coupling, HWP can be introduced into one layer of the passive waveguide stack. The ½ wavelength delay layer converts the output light on the rear side from P to S. Since the SBG grating only has P sensitivity, this prevents recombination of the front grating with light. A 10 ° rake angle alleviates the requirement for a grid formulation that results in higher ABW and lower chromatic dispersion. This allows sharing of the blue / green grid. However, in most embodiments of the invention, red may require a separate grid.

  The graph of FIG. 17 shows the relationship between the calculated DE and angle for each photon, and the output DE in the subtracted layer coupled to the original TIR. Assume that this light returns again and is not coupled. The composite output of a lattice containing a single interaction coupling loss is represented by a circular symbol. Note that an effective doubling in the FWHM of a single grating is obtained when considering the recombination effect of the back grating to the front grating with a 2 * 1 / e offset of the peak DE profile. Due to the secondary output coupling of the recombined light, the profile approaches a lossless composite grating profile (triangle symbol).

  FIG. 18 shows a further embodiment of the invention in a color image. The DigiLens are divided into two separate monochromatic doublet waveguides 230, 231: a monochromatic doublet waveguide for red (DIGI-O1A, DIGI-O1B) and a monochromatic doublet waveguide for blue-green (DIGI-O2A, DIGI-O2B). The input SBG (DIGI 1A to 1D, DIGI 2A to 2D) comprises a stack of four monochromatic red or blue-green lattices indicated by AD. In all other respects, the structure is very similar to the embodiment of FIG. HWF and QWF are arranged similarly to FIG. The doublet may be air separated or may have a low refractive index material in between. Components 230 are also numbered 230-246.

  In another embodiment of the present invention similar to the embodiment of FIG. 1 shown in FIG. 19, each DigiLens waveguide comprises a single SBG layer that supports red, green, and blue TIRs. Starting from IIN, the path is indicated by the numbers 1080, 1082, 1083 in the first waveguide 250 and by the numbers 1081, 1084, 1085 in the second waveguide. In any case, the red path, the green path, and the blue path are referred to by the letters R, G, and B. System components are labeled as in FIG. 1 and are further referenced by numerals 250-258 in FIG. Needless to say, such an implementation of the present invention requires careful control of the TIR angle to ensure that the diffracted light paths for the three colors overlap exactly. We have found that additional coatings may be required to enhance reflection at the blue end of the spectrum. In another embodiment of FIG. 19, the DIGI-O grating can be implemented as a multi-grating.

  The IIN structure for use with the present invention is shown in FIG. The optical system includes waveguides 260 including overlapping SBG elements 261, 262, overlapping SBG elements 263, 264, beam splitter layer 265, curved mirror 266, prism 267, projection lens 268, and microdisplay panel 269. An air gap 270 between the curved mirror elements is provided to allow TIR of the reflected light. As shown, separate SBG input and output grids are provided for each image region. The waveguide 260 and the gratings 263 and 264 may in particular form an HBE input grating. Alternatively, the waveguide 260 may be used to couple light to the input grating of the HBE. Of course, the IIN may be configured in many different ways to meet space, cost, and optical efficiency constraints. In the illustrated embodiment, half of the image from the microdisplay is continuously imaged into HBE. Thus, in FIG. 20A, the gratings 261, 264 are in their active state and the other gratings are inactive. Light from the image portion 1090 is projected onto the path 1091 by the projection lens. Thereafter, the light is reflected by the prism to the light path 1092, reflected by the curved mirror 266 to the path 1093, diffracted by the grating 261 to the path 1094, and subjected to TIR into the path 1095. It is diffracted out of the waveguide by the grating 264. FIG. 20B shows the light path from the second image region 1097. Here, the grids 261, 264 are switched to their inactive state, and the grids 262, 263 are switched to their active state. The path from the microdisplay is indicated by 1098-1104. In some embodiments of the invention, IIN combines the entire image into HBE. However, splitting the input image in two allows more optimal coupling of the image to the waveguide path. In the following, the discussion only considers black and white implementation. Initial design calculations by the inventors show that the basic approach is sound, which is the projection pupil (20 mm, in front of the grid junction), telecentricity, re-imaging aperture, less than 2% While satisfying features such as the geometric distortion of the image, the diffraction limiting performance is almost satisfied over the field of view with a compact structure. The design wavelength for IIN black and white implementation is 532 nm. The resolution is adapted vertically to 1080pLCoS (LCoS pixel pitch: 2.8 microns; Nyquist frequency 178 lp / mm). Note that the design feature is that the IIN / HBE can be positioned on the same waveguide side as the eye without compromising the lattice interdependency.

Light is projected from each LCoS at F / 2.8 (focal length: 5.65 mm) to give a 26 ° H × 30 ° V FOV. Light enters the HBE-I grating at an angle of 0 ° to + 26 °. The IIN is tilted at an angle of 13 °. In a typical 0 ° (input) / 52 ° (in glass) grid, this angular increase increases the angular bandwidth by about 20%. Note that the red ray in FIG. 13 collides with HBE-I at 0 ° and is diffracted into TIR. The green light beam strikes the SBG at about 26 ° / n, where the refractive index n is 1.592 (polycarbonate). It should be noted that S-BAL25 glass having a refractive index very similar to polycarbonate can be used for prototype production. The design can be extended to two and three colors. Initial results show that the basic approach is sound, which is the projection pupil (20mm, in front of the grid junction), telecentricity, re-imaging stop, less than 2% geometric distortion, etc. The diffraction limiting performance is almost satisfied over the field of view with a compact structure. The design wavelength is 532 nm. The resolution is adapted vertically to 1080pLCoS (LCoS pixel pitch: 2.8 microns; Nyquist frequency 178 lp / mm). A preliminary specification in IIN is given in Table 2.

  In one embodiment, there is no hard physical stop in the projection optic, but instead a projection stop is provided. The advantage of the projection stop is a reduction in waveguide thickness. In one embodiment, the stop is projected midway above the HBE to minimize the aperture diameter in the waveguide, so that the aperture width of the DigiLens waveguide coupler is minimized.

  In one embodiment, the stepped reflection profile below the SBG layer is used to control (or help) the grating DE change along the length of the DigiLens waveguide. This is usually achieved with an SBG grating using refractive index modulation. This can benefit HBE when a low percentage of light is out-coupled at the first bounce but a high percentage is out-coupled at the other end of the waveguide.

  The volume of the IIN structure is currently 20 × 40 cubic millimeters. However, there are many different ways to reduce the total volume of the IIN structure, as will be apparent when considering the drawings. For example, refractive elements with structures such as bird bath mirrors and projection lens systems can be replaced with diffractive optical elements. A polarization grating beam for illuminating the microdisplay by introducing an SBG waveguide in front of the microdisplay so that the rotated and reflected polarized light can travel through the waveguide towards the curved mirror A splitter can be provided.

  In one embodiment shown in FIGS. 21 and 22, the HBE 281 is provided with a coupling grating 283 at its input end (eg, HBE-I of the previous embodiment) and is typically two different formulations that are tilted at 45 °. An output grid (e.g., HBE-O) with 284,285 alternating SBG stripes is provided. Although fringes are shown equally spaced, their size and spacing may be varied for better illumination and image sampling control. However, making the fringes very narrow can reduce the system MTF. In general, the stripe geometry may require careful optimization. FIG. 22 shows an HBE incorporated into a display having a DigiLens 287 with DIGI-I288 and DIGI-O289 and an IIN286. The ray paths from IIN are indicated by 1105-1110, in which case the TIR paths in HBE and DIGI-O are indicated by 1107, 1109. The HBE output light coupled to the DigiLens (DIGI-I) is indicated by 1108. Output light from the display from DIGI-O is indicated by 1110.

  FIG. 80 provides another embodiment of a transparent waveguide display. In this embodiment of waveguide 8001, the magnitude of the refractive index modulation of at least one of input grating 8003 and output grating 8002 varies by a small amount along the x direction. In this embodiment, the pitch of the input and output grids must be the same to meet the interdependency requirements. The refractive index modulation may be changed in the z direction. In one case, the structure of this embodiment can help control the output light uniformity. The principles described in this embodiment may be applied to horizontal and vertical beam expanders. In one case, if a switchable grating is used, the refractive index modulation may be changed in time to match the time change of the input image content.

In any embodiment of the invention, efficient guiding may require the TIR beam to be confined between low index media. Currently available low refractive index materials such as magnesium fluoride (1.46) and silicon dioxide (1.39) are too high in refractive index to meet the strict TIR angle constraints required for full color implementation of HMD. If this is not possible, it is difficult to form and maintain voids. The proposed solution is to use a nanoporous material (mesoporous silicon). Nanoporous materials (eg, mesoporous silicon) are currently used in many optical applications, including antireflective coatings and planar optical waveguides. Their high porosity allows the formation of high quality and low dielectric constant thin films. Nanoporous materials can be formed into thin layers in a single step. In order to obtain a very low refractive index of approximately unity, the porosity needs to be very high and close to 95%. High transparency and low refractive index can be achieved simultaneously with these films. These membranes absorb water very efficiently and must be carefully sealed against moisture. The best approach may be to seal the passive grating, HWP, and material together. The SBG laboratory is also studying the potential role of nanoporous materials as high refractive index media. This increases the range of TIR angles that can be maintained in our waveguides with the potential to increase the horizontal FOV from 40 ° to about 45 °. Nanoporous materials are currently used in many optical applications including antireflective coatings and planar optical waveguides. Therefore, it makes sense to assume that the technology is accessible for our project. The manufacturing process must be convertible to the desired specification. Nanoporous materials can be formed in a single coating step. Alternatively, a multilayer structure with a stepped refractive index can be used. The SBG laboratory is also studying the potential role of nanoporous materials as high refractive index media. This increases the range of TIR angles that can be maintained in our waveguide. In summary, the main advantage is a monolithic structure that provides greater mechanical stability and durability and better beam confinement resulting in higher FOV.
Embodiment for automotive HUD

  As already discussed, the present invention may be used in many different applications. Some embodiments of the present invention are specifically directed to automotive HUDs, which are discussed in the following paragraphs.

  FIG. 23 is a schematic side view of a car HUD 300 having multiple exit pupils that incorporate DigiLens waveguides for driver 301 and occupant 302. The display may be based on any of the embodiments described above. Digilens elements are incorporated into the shared waveguide structure, in which case the input image is generated by the IIN 303 as described above. The ray path toward the driver exit pupil is indicated by rays 1110-1113, in which case the pupil is indicated by 1113. The ray path toward the occupant exit pupil is indicated by rays 1114-1116, in which case the pupil is indicated by 1117.

  FIG. 25 is a schematic side view showing an embodiment of the present invention similar to the embodiment of FIG. , 306 are tiled. The ray paths toward the pupil are indicated by 1118-1120.

  FIG. 25 is a schematic side view of a further embodiment of the present invention based on the embodiment of FIG. Used to tile the FOV indicated by 1131 along with tile 1132.

  In one embodiment of the waveguide, a DigiLens may be used to form a pixelated collimated image. A simple traditional analog of such a display shown in the schematic side view of FIG. A waveguide holographic version of this display is shown in FIG. The input image is provided by a pixelated SBG 323 comprising a two-dimensional array of switchable elements, such as an array labeled 324. Each element diffracts incident parallel light into the TIR path in the waveguide. The SBG array is illuminated by parallel light indicated by 1142 and 1143 from an external light source (not shown). Pixel 324 is illuminated by parallel light 1145. Preferably, the SBG pixel has diffusion characteristics. The DigiLens elements 325, 326 are not simple planar gratings, such as the gratings described so far, but have a refractive power so that the light generated at points on the surface of the SBG array is collimated, thereby the pupil 1148. A switchable field of view (FOV tile) bounded by rays 1146 and 1147 for viewing through is provided. As such, the DigiLens element provides a diffractive analog of the lens of FIG. The DigiLens element is configured to tile the FOV as in the embodiment of FIG.

  In one embodiment, the aforementioned DigiLens may be configured to provide a mirror. FIG. 28 shows how a rear-view mirror for automotive applications can be provided using a transmissive SBG 333 sandwiched between substrates 330 and 331 and a mirror coating 332 located on the DigiLens. The SBG diffraction angle follows the path of R1 and R2, and the light incident on the DigiLens is diffracted by the SBG layer and reflected by the mirror layer, while R3 and R4 leading to the driver eyebox. The reflection path that is labeled is designed to be off Bragg, i.e., out of the angular range for diffraction by SBG. Also, numerals 1151-1154 are attached to the optical path. As will be apparent when considering FIG. 28, the DigiLens can be configured to provide different ranges of reflection angles depending on the appropriate choice of grating prescription.

  FIG. 29 shows a HUD 335 for relaying an external image to the observation pupil near the driver. The light 1155 from the external image source enters the waveguide through the DigiLens 338 and receives TIR indicated by 1156 to 1157 and is coupled out of the waveguide as the light 1158 by the DigiLens 336 and exits the viewer. Head towards. This embodiment can help to see blind spots. The apparatus of FIG. 29 further comprises a beam splitter layer 337, which splits the incident TIR light into multiple paths, thereby increasing uniformity and minimizing gaps in the output illumination. be able to. This principle may be applied to any of the other embodiments of the present invention.

  FIG. 30 is a front view of a HUD 340 comprising an IIN 341 and a DigiLens 342 in accordance with the principles of the present invention, the HUD 340 sensing a structured light source 343 that emits infrared light 1159 and a driver's hand movement. And a detector 344 for detecting return infrared light 1159 for controlling the display.

  FIG. 31 is an embodiment of the present invention similar to the embodiment of FIG. 26, in which the information contained in the view tiles (FOV tiles 1, 2) is given in different ranges indicated by D1, D2. . Image light from the IIN 351 is converted into waveguide light 1170. The DigiLens 354 forms an image with a range D2 having a 1174 FOV centered in the direction 1173, and the DigiLens 355 forms an image with a D1 having a 1171 FOV centered in the direction 1172. Two FOV tiles are observed through pupil 1175.

  In most applications of the present invention, the preferred light source is a specific laser, in which case constraints on collimation and waveguide confinement need to be met. However, the present invention may be applied using LEDs and other relatively narrowband incoherent light sources with some modifications. FIG. 32A shows an embodiment of the invention in which SBG is used to compensate for the spectral bandwidth of RGB LEDs in a color HUD. The illustrated red LED has a peak output at 639 nm and a FWHM bandwidth defined by wavelengths 634 nm and 644 nm, as shown in FIG. 32B. The DigiLens includes a laminate of RGB diffraction layers, and each layer includes an input grating and an output grating. In each layer, the SBG is recorded to give a relationship between peak diffraction efficiency and wavelength characteristics (along the waveguide) shifted by small increments from the peak wavelength as shown in the table of FIG. 32C. Techniques for recording Bragg gratings that give a wavelength shift upon reproduction, usually with control of the constituent wavelength and recording angle, are well known to those skilled in holography. The RGB SBG layer is continuously switched in synchronization with the RGB LEDs. As shown in FIG. 32A, the color display 360 includes red, green, and blue Digi-Lens waveguides indicated by symbols R, G, and B, and DIGI-I indicated by 360R, 360G, and 360B. A diffractive lens or a DIGI-O grating indicated by the grating and 361R, 361G, 361B, a red, green, and blue light source 362R, 362G, 362B that provides light 1180, a microdisplay 363, and a parallel light 1182 A beam expander including holographic lenses 364 and 365. After being coupled to the DigiLens element, the light undergoes a TIR represented by 1183 as described above and is diffracted out of the DigiLens as red light, green light, blue light 1184R, 1184G, and 1184B.

  In one embodiment shown in FIGS. 33 and 34, a DigiLens is combined with a windscreen. DigiLens is very suitable for such an implementation. This is because the DigiLens can be designed to work in a curved waveguide and is very thin using a substrate as thin as 100 microns with an SBG layer 1.8 to 3 microns thick in between. It is because it can form from a layer. DigiLens are separated by a thin layer of mesoporous material of the type described above. It should also be noted that typical car windscreens typically have a radius of curvature of a few thousand millimeters that does not pose significant challenges for maintaining the waveguide.

  In one embodiment, the DigiLens is formed as a flexible layer 371 that can be adhered to the inner or outer surface of an existing windscreen 370 as shown in FIG. The IIN 372 is generally located below the dashboard.

  Alternatively, the DigiLens layer can be incorporated into the windscreen as part of the screen manufacturing process as shown in FIG. Generally, the windscreen comprises an outer tempered glass layer 373, two or more PVB layers 374, 376 for UV blocking, and an inner tempered glass layer 377. The DigiLens 375 is sandwiched between two of the PVB layers. In one embodiment, the DigiLens built-in windscreen manufacturing process uses a second PVB film to sandwich the RMLCM before injecting the RMLCM onto the PVB film and recording the SBG in the holographic recording step. Steps.

  In one embodiment shown in FIG. 35, a transparent display is provided comprising waveguide components DIGI-I, DIGI-O, HBE-I, HBE-O and IIN similar to the IIN described above. In this case, however, each of the waveguide components comprises a single SBG layer. Only the SBG layer of the waveguide is shown and the substrate and electrodes are omitted. The ray path from the IIN is indicated by 1200 to 1203, which are the TIR path 1201 in the HBE, the expanded beam extraction 1202 from the HBE, the TIR 1203 in the DigiLens, and the display from the DigiLens. A light extraction 1204 for. Components are also referenced by the numbers 390-394.

  In one embodiment shown in FIG. 36, a transparent display DIGI-O, HBE-I and an IIN similar to the IIN described above are provided. The two waveguide components HBE-O, DIGI-I are incorporated into a single waveguide component labeled HBE-O / DIGI-I that performs the dual function of beam expansion and beam rotation. An advantage of this configuration is that a change in beam direction is achieved without having to exit the waveguide grating and enter the waveguide grating again, as in, for example, FIG. 35 and most other embodiments. This may require that the DIGI-I grating be tilted in the plane of the drawing, in most cases of practical objects, tilted at an angle of 45 °. Therefore, the TIR path is rotated 90 ° in the DIGI-I waveguide and proceeds to DIGI-O. The ray path from IIN is indicated by 1205-1208. The components of the display are also referenced by numbers 400-403.

  As is apparent from the drawings and previous description, in this case, in most of the embodiments of the present invention, HBE-I and HBE-O and DIGI-I and DIGI-O are in a single SBG layer. It may be realized. However, this reduces the overall number of layers, but has the disadvantage of increasing the overall size of the display. The width of HBE and DIGI-O is largely bounded by the microdisplay dimensions and the required field of view. In HUD and HDD applications, if the space required to implement DIGI-O and HBE components is small relative to the size of DIGI-O, a similar sized microdisplay can be used to further The trade-off becomes even more difficult in near-eye and HMD applications that have stringent FOV requirements and further increase the relative widths of HBE and DIGI-I waveguides.

  In a further embodiment of the invention directed to the color display shown in FIG. 37, the DigiLens comprises separate red, green and blue waveguides. Preferably, the waveguides are optically separated from each other, which may require that the waveguides be separated by air or by a thin layer of low refractive index film. A preferred option is to use nanoporous materials. A DigiLens waveguide is shown in FIG. 37, and the layers are referenced by the numerals 1-3 on the DIGI-I and DIGI-O designations (waveguide components are also referenced by numerals 415-420). ). The components of IIN and HBE are not shown in detail, but are simply indicated by 421.

  In general, the DigiLens are tilted at a rake angle of about 10 ° to allow the most advantageous diffraction angle in the waveguide as shown in FIG. The IIN and HBE may be on the side of the display closest to the eye 422 as shown in the figure. However, it will be appreciated that many other forms are possible. The ray path toward the eye is indicated by rays 1210-1212. FIG. 3 is a three-dimensional view of the same display showing three DigiLens.

  FIG. 38 shows a color display according to the embodiment of FIG. This implementation has three DigiLens layers 410-412, one for each color, where DIGI-I and HBE-I are incorporated into a rotating / beam expanding grating, such as the grating indicated by 436, and IIN The red, green, and blue ray paths from are indicated by 1220-1223, where red, green, and blue are indicated by the symbols R, G, B. Note that the HBE-I component not shown is similar to the component shown in FIG. 35, but with separate layers for red, green, and blue.

  In a car HMD, the field of view is relatively small compared to the field of view of a HMD where a 10 ° vertical × 25 ° horizontal field of view is considered a long-term goal. Such angular content can be easily handled by waveguides using single layer SBGs. However, since there is an interest in color, this brings further demands on the information processing capabilities of the waveguide. In one embodiment shown in FIG. 39, a passive single SBG layer digi lens is provided that uses holographic multiplexing to guide and diffract at least two colors into the waveguide. Multiplexing is the ability to record multiple Bragg gratings on the same layer. First, multiplexing is an improved angular profile by combining two gratings of similar prescription to broaden the diffraction efficiency angular bandwidth and provide better brightness uniformity and color balance across the exit pupil and field of view. Can be used to produce Second, multiplexing encodes two separate diffraction prescriptions that may be designed to project light into separate field regions or to diffract light of two different wavelengths into a given field region. May be used for Multiplexing also provides the great advantage of reducing the number of layers in the waveguide structure. Care must be taken to ensure that there is no contention between the lattices during recording and that there is no crosstalk between the lattices during playback, resulting in unbalanced Des. The apparatus of FIG. 39 is similar to the apparatus of FIG. 35, except that the DIGI-O component is here a multiplexed grid. Components are also referenced by the numbers 470-474, and the ray path from the IIN through the HBE and DigiLens is referenced by the numbers 1240-1243. Preferably, a horizontal beam expander (HBE) extends along the lower edge of the DigiLens® so that the IIN can be hidden under the dashboard. In general, such a HUD has a 145 mm horizontal x 80 mm vertical eye box with a pupil distance of 800-900 mm. The target field of view is 10 ° -15 ° vertical × 10 ° -15 ° horizontal. Windscreens have transparency greater than 75%. Generally, the wind screen has a curvature of horizontal 3000 mm; vertical 9000 mm. IIN can be received in a volume of 1-2 liters.

  The incorporation of a DigiLens into a windscreen is shown in FIG. The stack of layers in the windscreen comprises glass (outside) 1.60 mm; PVB (3 layers): 0.8 mm; glass (inside): 2.0 mm. The total is 4.4 mm. The SBG layer comprises a 5 micron SBG sandwiched by a 50-100 micron substrate and the SBG cell is sandwiched by a low refractive index layer 0.5-2 microns thick. The UV adhesive gasket line limits the SBG material filling that bounds the effective area of the display. Clear gaps between the lattice regions are filled with transparent acrylic, and the acrylic is UV cured for complete transparency. This multilayer structure allows very strong lamination and does not depend on the SBG film at all for lamination strength. FIG. 41 is a flowchart illustrating the implementation of the embodiment of FIG. 39 in an automobile HUD.

  The color multiplexing used in the embodiment of FIG. 39 is in two ways: first, using two multigratings, eg red and blue / green gratings, or secondly. This can be done using three multiplexed grids, ie using multiplexed red, green and blue grids. The design problem is to use two or more multiple grids to determine the optimal recipe for a 10 ° vertical (or more precisely tangential) field of view. Design variables are the Bragg wavelength and TIR angle, DE profile (ie, grating thickness and modulation) in each color. Because the DigiLens are coupled to the windscreen or in some cases embedded in the windscreen, the waveguide is sandwiched by a low index material (if the air gap cannot be tolerated). It has been assumed that the refractive index of the nanoporous material layer is 1.2. At an SBG index of 1.52, this corresponds to a minimum TIR angle of 52 °. When designing a multi-grating, special care may be required to obtain the shape of the DE profile, which is important, and a narrower DE profile to avoid crosstalk between colors. Is preferred. The desired DE profile can be achieved by optimizing the grating thickness and refractive modulation. The relationship between simulated diffraction efficiency (DE) and TIR angle process based on cogelonic diffraction theory for typical red, green, and blue gratings multiplexed into a single SBG layer is shown in FIG. 42A. And shown in FIG. 42B. The curve represents the DE profile in each of the three multigratings. The rectangular area represents the approximate RGB TIR angle range. FIG. 42A shows a case where the multiple grating is illuminated with red light. FIG. 42B shows a case where green light or blue light illuminates the grid. The curve shifts. This is because the angle that satisfies the Bragg condition shifts as the illumination wavelength changes. Since the TIR range in the blue-green band is below the TIR range in red, there is no crosstalk between the two color bands.

  43 and 44 show IIN, two HBE components each comprising HBE-I and HBE-O, two DigiLens components each comprising DIGI-I and DIGI-O, and a beam splitter ( B / S), DIG-I sandwiches a half-wave film (HWF) in between. FIG. 43 shows a three-dimensional view. FIG. 44 is a cross-sectional view of only the DigiLens showing the light path. The HBE-O and DIGI-O gratings multiplex the red and blue-green diffraction gratings as shown by the solid and dashed rays in FIG. Red light rays in the rear DigiLens waveguide 460 follow paths 1231, 1232, and 1239. Blue-green rays in the same waveguide follow paths 1230, 1233, 1239. Numbers 1234 to 1237 are attached to the light beam paths in the front waveguide. The rear and front waveguide components are referenced by numerals 1 and 2, respectively, as well as by numerals 440-447. The HBE comprises two waveguide elements (ie, two switchable SBG layers separated by a suitable substrate), each waveguide element supporting 20 ° horizontal × 22.5 ° vertical. HBE is switchable. Each HBE waveguide is separated from other HBE waveguides by a low refractive index layer. IIN uses HD 1366x768 (eg, 0.37 "diagonal LCoS microdisplay as supplied by Himax. Another microdisplay is the Syndiont 720P (0.37" display) supplied by Syndiant. is there. This gives a resolution of 1.76 arc min / pixel (over 40 ° × 22.5 ° FOV). Each grid provides an angular width of about 10 ° in air for a single color (equal to about 6.5 ° in glass). There is a slight bias in the angular space due to the HBE rake angle (at the side entrance of the IIN), so the field of view becomes slightly uneven. For example, 18 ° and 22 °. Note that switching of adjacent grids in the angle space prevents cross coupling from occurring between adjacent grids. The angle in each waveguide is minimized. Green is arranged near the TIR angle with a small allowable margin (for example, + 0.5 ° to 1.0 °). Each waveguide is a narrow band blue mirror that is coated over the waveguide angular range. The light output from each HBE to the DigiLens is −20 to 0 ° horizontal (approximately) × ± 11.25 ° vertical and 0 to + 20 ° horizontal (approximately) × ± 11.25 ° vertical. This gives a composite field of view of −20 to + 20 ° horizontal × ± 15 ° (ie, 40 ° × 22.5 °). A preferred material is polycarbonate (n = 1.585) or equivalent. The substrate thickness is 0.5 mm. Each cell is 1.0 mm thick, so each HBE waveguide is 2.0 mm thick. Both HBE waveguides are 4.0 mm thick with small air gaps or low index material gaps. HBE is multiplexed with respect to color as described above. The HBE dimension is 70 mm wide x 11 mm high. Note that the height includes a 1 mm margin at the vertical edge. The IIN used in the embodiment of FIGS. 43 and 44 has a focal length of 1.3 mm. The microdisplay (LCoS) pixel pitch is 6.0 microns. The F value of the optical element is 4.6. By adapting the Airy disk to the LCoS pixel pitch, approximately 75% contrast is obtained at the Nyquist limit. The opening of the IIN is 2.4 mm. The optical structure of FIGS. 43 and 44 may require two DigiLens waveguides (ie, two SBG layers separated by a suitable substrate), each DigiLens waveguide being 11.25 °. Supports vertical x 40 ° horizontal. The input DIGI-I element is switchable. The DIGI-O element is passive. Both the input and output gratings are the multiplexed red and green-blue gratings described above. The dimensions of the DigiLens substrate are 50 mm wide × 61 mm high. In one embodiment, the input grid is switchable and not multiplexed. That is, in this case, four switchable input grids are used. Importantly, the input recipe and the output recipe are interdependent. The input light must be P-polarized (since the DigiLens only diffracts P-polarized light). Each waveguide has a QW film below its entire length. This allows a waveguide that is twice as thin. The TIR reflection is rotated by half a wavelength (since it passes double through the QW film). Therefore, ray extraction from the waveguide only occurs with every other interaction with the SBG. The output of the rear digi lens (ie, the digi lens closest to the IIN as shown in FIGS. 43 and 44) undergoes two QW film interactions and rotates to S, thus Does not interact. Therefore, the output from the display is a mixture of P-polarized light and S-polarized light.

In one embodiment shown in FIGS. 45-52, a transparent display based on fully passive HBE and DigiLens waveguide components is provided. As will be elucidated in the following description, this embodiment uses HBE-I configured to sample the aperture and / or FOV of the image light from the IIN. This embodiment will now be described in the context of a 52 ° × 30 ° FOV black and white display that may be used, for example, to provide an HMD. However, as will be apparent from the following description and drawings, this embodiment may be used to provide a wide range of different FOVs, with the advantages of the techniques provided herein.
Embodiment using all passive SBGs

  FIG. 45 is a three-dimensional view of one embodiment of a display in one embodiment in which three HBE waveguides and three DigiLens waveguides are provided. The HBE waveguide is indicated by numeral 541 and the DigiLens waveguide is indicated by 542. In this case, the HBE waveguide is marked with symbols W to Z as before, and the DigiLens waveguide is marked with the symbol. P to R are attached. Each HBE waveguide includes HBE-I and HBE-O, also referenced by 543,544 respectively, and each DigiLens is DIGI-I and DIGI-O, also referenced by 545,546, respectively. including. IIN is indicated by 394. The ray path from IIN through HBE waveguide 541Z and DigiLens waveguide 542R is shown using rays 1330-1334. Note that the pupils are combined in front of DIGI-I, so that a total 52 ° horizontal × 30 ° vertical FOV exists at this stage.

  One embodiment relates to a projection stop. FIG. 46 is a schematic side view showing the formation of a projection stop by IIN. Light from image pixels at the center and edge of the image displayed on microdisplay 500 passes through stop 502 to provide peripheral beams 1300, 1302 and on-axis beam 1301. The projection lens 501 collimates this light and provides collimated beams 1303 to 1305 that overlap at the projection stop 1306. Light from other points at the input is similarly focused to the projection stop. Note that the projection optical element is simplified in FIG. 46, and actually the projection lens is a multi-element system as described above. As will be appreciated by those skilled in the art of optical design, the need for a physical stop 502 is minimized by limiting the numerical aperture (NA) in the microdisplay with the appropriate structure of the illumination supply optics. Be suppressed (or even eliminated). Note that the distance from the lens to the projection aperture is very large compared to the thickness of the HBE laminate.

  FIG. 47 is a schematic plan view showing the coupling of light from the IIN to the HBE waveguide 503. The input grating or HBE-I comprises two gratings 504 and 505 having a small distance spacing along the waveguide propagation axis. Importantly, the two gratings have DE versus angular properties that do not substantially overlap. The HBE-O grating is positioned further down the waveguide as indicated by 506. In contrast to the input grid, the output grid is multiplexed with two different grid prescriptions as described below. The advantage of this coupling scheme is that it allows the mapping of the angular content of the input light to a given grating region 504, 505, thereby separating the HBE input grating (HBE-I) along the waveguide optical axis. That is the point. This effect is accentuated by having a small entrance pupil diameter. For simplicity, only two ray paths through the waveguide are shown here. In the first path, incident light 1307 is diffracted by the first grating element 504 of HBE-I into the first TIR path 1309. In the second path, incident light 1308 is diffracted by the second grating element 505 into the second TIR path 1308.

  The interaction between the beam and the grating is shown in more detail in FIG. 48, which shows a portion of the HBE waveguide that includes the input grating of FIG. The incident light beam 1307 is diffracted by the first grating 504 into the light beam path 1311. After the first TIR reflection, the reflected ray 1312 is off Bragg and therefore passes through the first grating without any deviation. After the second reflection, the light beam avoids the diffraction by passing through the trailing edge of the first grating. At this time, the TIR advances to the next lattice. After the third reflection, ray 1314 passes away from the leading edge of the second grating. After the fourth reflection, the resulting ray 1315 is off Bragg. Finally, after the fifth reflection, ray 1316 passes through the second grating's trailing edge and proceeds to HBE-O. Obviously, this simplified explanation applies only to the main rays and does not adequately describe the behavior of the diverging beam that results in unwanted diffraction of the rays that capture the grating. However, narrow beam angles in the waveguide reduce the effects of unwanted beam-grating intersections.

  FIG. 49 is a schematic cross-sectional view of the four-layer HBE shown in FIG. Following the previous description, each waveguiding layer comprises an HBE-I grating with two separate gratings and an HBE-O with multiple gratings. The waveguides may be separated by voids or preferably by a thin layer of nanoporous low refractive index material. The input grating is numbered 511, 512 and the output grating is numbered 510, where the waveguiding layer is referenced by the symbols W, X, Y and Z. The figure shows the input rays from the projection lens 514 interacting with each of the input gratings in each layer. Note that the output light from the waveguiding layer W may interact with one or more of the layers X-Z. However, as already discussed, the property of lattice interdependence maintains the beam angle for any such interaction. The resulting beam shift due to such interlayer interaction may provide a beam splitter or homogenizer. For example, consider the input ray 1320. This ray is diffracted by the first grating 511W into the TIR path 1321, which propagates through the second grating 512W without a shift and continues its TIR path 1322. In the output grating 510W, a part of this light is diffracted into the light beam 1323 in the waveguide 510X. When part of this light enters the second waveguide, it is diffracted to TIR longitude 1324 and the remaining light travels in direction 1323. Further interaction with grating 510Y is indicated by rays 1325 and 1326.

  FIG. 50 is a table showing multi-grating pairing used in each waveguide layer of the embodiment of FIG. Each pair of grids must have a DE versus angular bandwidth with sufficient distance spacing to avoid large overlaps. Since the grating is a lossy thin grating characterized by a low DE peak and a wide angular bandwidth, this distance spacing needs to be quite large. FIG. 51 is a chart showing one possible scheme for the polymerization DE versus angle profile in the embodiment of FIG. Each pair of gratings corresponds to a 26 ° principal ray angular distance. It is assumed that the total horizontal FOV is 52 °. For a thin (low peak DE, high ABW) grating, the ABW is about 13 °. Assume that the input HBE grating has an ABW of 6.5 °. In this case, the angle range is −6.6 ° to 0 ° as A, and the angle range is 0 ° to 6.5 ° as B. It will be appreciated that A and B should not be used in the same waveguide, first due to DE versus angular overlap and secondly due to lack of interdependence. Lattice separation is based on FWHM. However, other means may give better optimization of the overall lighting profile. For example, lattice overlap is possible at 30% of the peak angle. Assuming FWHM, this gives 8 grids to span a 52 ° FOV (ie, 8 × 6.5 °).

  Obtaining high illumination uniformity is an important issue in SGO design. The main design parameters are thickness and refractive index modulation. As described above, by applying a small wedge angle to the grating layer, the peak DE and angular bandwidth can be adjusted along the waveguide. However, the light remaining in the waveguide at the end of the propagation path tends to accumulate at large angles resulting in non-uniform output illumination. At present, the present inventors consider that this effect is not so great. A more sophisticated method when very strict lighting control is required is to shape the grating layer by applying a gradient in two directions. As a further improvement, the surface of the grating can be curved. The required grating thickness changes are very small and are typically 1-2 microns across the waveguide, so the impact on collimation and MTF is negligible in most implementations. FIG. 51 is a three-dimensional view of the SBG grating 530 characterized by two orthogonal slopes. Four different corner heights relative to the plane of the waveguide due to orthogonal tilt are indicated by 531-532. However, the preliminary ray-tracing analysis by the inventors has shown that the optimal DE profile required in the waveguide is a one-dimensional function and is not the number of beam bounces in the waveguide, but the length of the waveguide. Produced some evidence that it was a function. The ray angular displacement (ie, ± angle) near the chief ray would require the same grating thickness profile as the chief ray (depending on the length of the waveguide). This suggests that a 2D profile may not be required for optimal uniformity. Note that the primary DE must be scaled as the interdependence of the difference between the waveguide length and the distance traveled by the beam.

  53A-53C are schematic diagrams of three operating states of the HBE in one embodiment. The projections of the waveguide 551 and the IIN projection lens 550 are in each case shown using three collimated beam portions indicated by 1341-1342. The shaded area is in the HBE cross section seen by each DigiLens waveguide for each of three separate 10 ° Vertical FOV bands that are coupled to one of the DigiLens waveguides to give a 30 ° full vertical FOV. Correspond. The shaded areas in FIGS. 53A to 53C also show a part of DIGI-I that receives light from HBE-O in the three vertical FOV areas. Only 1/3 of the aperture is collected by DIGI-I in each state. By keeping the effective aperture low in this way, it is ensured that the DigiLens waveguide does not require a large thickness. Using the above aperture method (and polarization management referred to earlier in the specification), it is estimated that the total thickness required for the three DigiLens waveguides results in a total thickness of 6 mm. The This assumes a rectangular exit pupil. If a circular pupil is allowed, the need to achieve extreme oblique angles is eliminated, thereby reducing the overall thickness.

  Although all the passive gratings described above are feasible in black and white, it seems necessary to introduce switching in order to give full color and crosstalk can be overcome.

It is important to note that a unique feature of the embodiment is how HBE selectively samples portions of the input image, each portion being characterized by either an angular region or a spatial region. is there. This approach allows the waveguide, especially the DigiLens, to be very thin. This is a particularly important feature in HMD and near eye. The process of sampling the input image described above should be distinguished from the process of switching the entire input image to a waveguide used in FOV tiling as disclosed in the prior application.
Typical features

  In one embodiment, the refractive power may be provided by at least one of the gratings used in HBE and DigiLens waveguides. The recording of lens prescriptions in diffractive optical elements is well known. In the present invention, this gives the possibility of fine tuning the display focus without the need for an auxiliary lens. Such a lens can also be used to correct aberrations. Switching holograms offer the possibility for a solid-state (no moving parts) solution to give images in different ranges. This may require multiple layers. This provides an attractive feature in HUD and HDD applications. The recording of a high refractive power hologram lens may require careful consideration for overcoming off-axis holographic aberrations. The constituent optical elements are potentially more complex, but once the master hologram is formed, the contact printing process is the same as any other hologram.

  In one embodiment, a multilayer thin film coating is applied to the reflective surface of the DigiLens waveguide to increase the waveguide range beyond the TIR range. Glass and plastic do not allow the range of TIR angles required for large fields of view. For example, light below 39 ° is not supported by polycarbonate TIR (refractive index at 532 nm = 1.585). The problem is to achieve a minimum waveguide angle of 30 °, which is far below the critical angle in plastics and low cost glass. The challenge in coating design is to achieve a reflective coating formulation that obtains the required reflective power without image quality degradation or loss of see-through transmission. The coating may require optimization for loss from wavelength polarization, angle, scattering, absorption. One advantage of adding a dielectric film on the substrate is to significantly reduce the amount of diffractive power required, thereby improving the grating angular bandwidth. The dielectric coating has the following properties: a) high reflectivity for S & P light at angles from 30 ° (in glass) to 39 ° (TIR angle), b) 0 ° ± 13 ° for P light (in glass) High transmittance at; equal to 35 ° × 20 ° corner area in air, c) good angular control of reflectivity can be achieved due to the narrow bandwidth of the light source, d) non-laser notch for all layers Having high see-through at the wavelength.

  In one embodiment, the input gratings in at least one of the HBE or DigiLens, i.e. the gratings HBE-I and DIGI-I, are characteristically uniformly distributed over a range of beam angles to be transmitted through the HBE and DigiLens. In order to give the DE versus angle, a stack of grids with different k vectors is provided. In general, the gratings are spaced apart by a 200 micron (or even 100 micron) substrate to keep the stack as thin as possible. Finally, we believe that the minimum practical grid stack thickness can be obtained using spin coating techniques.

  In one embodiment, another scheme of multi-grids with different k vectors avoids the need for stacking.

  Any of the previously described embodiments using laser illumination may incorporate a despeckle device to eliminate laser speckles placed at any point in the illumination path from the laser path to the glasses. Good. Preferably, the despeckler is an electro-optic device. Desirably, the despeckler is based on an HPDLC device.

  In one embodiment, the display incorporates a homogenizer that combines beam shaping and speckle exclusion. Desirably, the SBG arrays used to perform the function are themselves diffractive waveguide devices that can be seamlessly implemented as additional SBG layers in one or more of the waveguides or within the IIN. Speckle rejection is achieved by a combination of angle diversity and phase diversity. Exemplary waveguide homogenizers include US Provisional Patent Application No. 61 / 796,795 entitled COMPACT LASER ILLUMINATOR INCORPORATION A DESPCKLER having a filing date of November 20, 2012, and LASER ILLUMINATION DEVICE. PCT Application No. 2008/001909 having an international filing date of July 22, 2008, entitled As will be apparent from consideration of the drawings and specification text, the present invention provides several opportunities for incorporating such devices into the IIN and waveguide components of a display.

  The present invention provides a transparent display based on a DigiLens comprising one or more passive SBG waveguides, each of which projects a vertical field of view or a portion of a particular color. The present invention is made possible by the improved diffraction efficiency angular bandwidth obtained by using the thinner SBGs and taking advantage of the inherently wide sagittal angular bandwidth of the Bragg grating. The present invention provides a large field of view, for example 52 ° horizontal, without sacrificing any of the usual goals of high transparency, high resolution, ultra-compact (thin) form factor, light weight, and sufficient eyebox. X30 ° vertical can be provided. Waveguide components and compact input image nodes meet the goals of small form factors, paths to curved visors, and slimlines. It is believed that the FOV can be increased with the expected improvement in angular bandwidth and optical efficiency. The display module design approach allows for rapid growth from black and white to color without the need for large structural redesigns. A reasonable imaging performance of 1.0 cyc / mr can be provided in both color and black and white solutions. Optical performance in black and white exceeds 1.4 cyc / mr display pixel resolution. The best resolution is achieved in black and white, but good performance can also be achieved in color displays. In HMD, the present invention can provide a 25 mm wide eye box with a pupil distance of 25 mm. This allows 90% of the population to be accepted without any adjustments. The substrate guide diffractive optical element is used anywhere except within the input image node (IIN). However, in future developments of the design, refractive components can be replaced with diffractive elements to create additional form factor compression and manufacturing advantages. The IIN may be mounted on the upper side, side portion, front side, or rear side of the DigiLens. Thereby, a series of ergonomic requirements can be satisfied while maintaining the core DigiLens functionality. The design may not require near-idigi lens segmentation or mosaicking, thereby eliminating the problem of illumination ripple and discontinuities and scattering from the electrodes. A transparent display according to the principles of the present invention is filed on August 24, 2012 by the inventors, entitled IMPROVEMENTS TO HOLOGRAPIC POLYMER DISPLIED CRYSTAL MATERIALS AND DEVICES, also referred to by applicant's serial number SBG104. We also benefit from the plastic SBG technology disclosed in US Provisional Patent Application No. 61 / 573,066 having

  The present invention is premised on the teaching contents of the prior application specified as described above. In particular, the present invention relates to US Provisional Patent Application No. 61/61, filed April 25, 2012 by the present inventors entitled WIDE ANGLE COLOR HEAD MOUNTED DISPLAY, also referred to by applicant's serial number SBG109. The polarization recycling method disclosed in the '687,436 specification may be used. This particular feature is due to the properties of the SBG material (current or future developed material) or intentionally introducing a polarization rotation component into the waveguide, thereby improving device efficiency through polarization recycling and polarization recycling. May be relevant when the polarization is not maintained by the SBG outcoupling waveguide. Specifically, linearly polarized light is input to the DigiLens waveguide (ie, p-light coupled from the HBE to the waveguide) and the light is converted to a mixture of S-polarized light and P-polarized light. If so, thinner DigiLens waveguides can be used. This may allow a factor of up to twice the thinness of the waveguide.

  The present invention may incorporate a beam splitter layer into the waveguide to achieve uniformity. As a further improvement, a beam splitter offset in the waveguide may be obtained. That is, it is offset from the midpoint of the waveguide rather than in the middle of the waveguide surface, thereby maximizing uniformity after multiple bounce interactions. Yet another improvement is to use different reflectivities in the beam splitter to optimize and adjust beam mixing. The concept is to optimize and optimize pupil filling by changing the reflectivity% of the beam splitter to something other than 50/50, or by changing the t × / R × split along the B / S length It can be done.

  Note that the thickness of the hologram shown in the drawings is exaggerated. In general, the grating is 1.8-3 microns thick sandwiched by 100-200 micron thick substrates. Transparent electrodes applied to both sides of the substrate are measured in nanometers.

  In one embodiment, a holographic brightness enhancement film or other narrow band reflector is attached to one side of the display, the purpose of which is to reflect only the display illumination wavelength light, making the see-through display the opposite viewing direction. Can be invisible (and therefore safe). Here, the reflected display lighting is effectively projected and thus blocked in one direction, which makes the lighting ideal for transparent desktop display applications in customer or personal interview settings that are common in banking and financial services settings It becomes the target.

  An important performance parameter in this context is the see-through transparency of the display. Variables affecting transmission are the ITO coating (0.995), the AR coating (0.99), and the absorption of the substrate and holographic layer. Fresnel loss also exists at the interface between the waveguide and the low index coupling layer. The transmittance required for a color display exceeds 70% with the aim of exceeding 90%. Assuming three waveguides per display and two substrates per waveguide, the calculated transmission is 93%, thus meeting the required objective. It is our intention to implement this structure using a 100 micron glass substrate. Even with three waveguides and three substrates per waveguide (note that two holographic layers may require three substrates), the overall thickness of the display of the color display It is still less than 1 mm. The thickness of the holographic layers (including the coating) is negligible and each holographic layer contributes only 4-5 microns to the overall thickness. This is a very important feature of our approach because weight is always a problem. If plastic is used, the weight can be further reduced.

  In a preferred embodiment, the SBGs operate in a reverse mode so that they diffract when voltage is applied and otherwise remain optically passive. The SBG is implemented as a continuous SBG sheet separated by a thin (as thin as 100 microns) substrate layer as shown. Ultimately, the design goal is to use a plastic substrate with a transmissive conductive coating (to replace ITO). Plastic SBG technology suitable for this application has been developed in the parallel SBIR project. This is a planar monolithic structure that takes full advantage of narrowband laser irradiation using monolithic holographic optical elements.

  The present invention has a series of advantages that are ideally suited for substrate guide optics. First, the cost of the component is greatly reduced. Optical complexity is included in various holographic optical elements. Once the non-repetitive engineering (NRE) associated with the formation of a set of masters is complete, the replication cost is relatively small compared to the iterative material cost associated with a separate refractive component. Second, assembly time is greatly reduced. Not only is the number of parts greatly reduced, but the assembly process is much faster. Planar structures can be stacked cost-effectively with each other with very high optical accuracy using alignment criteria. The contact effort is greatly reduced compared to the effort to form a one-part assembly to strict standards. Third, the optical accuracy is quite high. One of the biggest challenges in designing a new optical structure is controlling the increase in tolerances for one-part, mechanical housing, and assembly procedures. With holographic optical elements (HOE), “determination criteria” can be compiled by senior engineers, and this level of quality can be captured by the HOE master during the NRE stage. In addition to the fact that optical alignment of HOE can be achieved with high accuracy, individual HOEs tolerate greater alignment changes. Therefore, the overall yield of high quality devices is very high. Finally, size and weight are greatly reduced by this monolithic structure, as is the durability of the entire subsystem.

  Obviously, in any of the above embodiments, the eye lens and retina may be replaced with any type of imaging lens and screen. Any of the aforementioned embodiments of the present invention may be used in either a direct viewing display or a virtual image display. Possible applications range from small displays such as those used in viewfinders to large area public information displays. The embodiments described above may be used in applications where a transparent display is required. For example, the present invention may be used in applications where displayed images are superimposed on a background scene, such as a head-up display or a teleprompter. The present invention may be used to provide a display device positioned at or near the internal imaging surface of the optical system. For example, any of the embodiments described above may be used to provide symbol data display for a camera viewfinder. In the camera viewfinder, the symbol data is projected onto the intermediate image plane and then magnified by the viewfinder eyepiece. It will be clear that the invention may be applied in binocular or monocular displays. The present invention may be used in a stereoscopic mounted display. Any of the above-described embodiments of the present invention may be used in a rear projection television. The present invention may be applied in avionics displays, industrial displays, and medical displays. There are also applications in entertainment systems, simulation systems, virtual reality systems, training systems, and sports.

  The preferred light source for the display is a laser that is ideally suited for diffractive optics, thus unleashing all the capabilities of our HMD, HUD, and HDD structures. With respect to brightness, resolution, and color gamut, the present invention is also possible in some applications where optical performance is less important to be applied using LEDs.

Currently, the SBG used in one embodiment is manufactured using stand-off exposure. However, the process can be easily converted to a contact printing process. The IIN may be implemented as an assembly of separate refractive components. However, it is highly desirable to convert the structure into a stack of planar holographic elements. With a sufficient amount, such an implementation of IIN achieves a very attractive price point. Preferably, the substrate used in the waveguide is manufactured from a ballistic-quality plastic substrate. Proof of feasibility has been established and process optimization activities are ongoing. Replacing the refractive component with a laminated plastic-based planar holographic element makes the display according to the invention essentially more robust.
Further embodiments

  The following embodiments relate to displays that use a single waveguide HBE. This particular embodiment is currently considered more suitable for low field devices such as HUD. However, recognizing that it is likely that the size of the HBE can be managed, there is theoretically no reason why the same embodiment cannot be used for high FOV applications such as HMD. As will be described later, the necessary condition is a non-projection pupil.

  FIG. 54 shows a projection scheme that does not result in a projection pupil of the type previously described in the specification text. The pupil may be formed inside the projection lens as shown in FIG. 54A, or may be formed in front of the projection lens using an aperture 562 as shown in FIG. 54B. Such a projection scheme provides angular diversity at a distance along the z-axis or optical axis that is less than the total FOV. For example, referring to FIG. 54A, when light from the image point sources 1350A to 1350C collimated by the lens 560 to the collimated light bundles 1351A to 1351C is considered, the light bundles 1351A and 1351B and the light bundle 1351B are considered. , 1351C. From basic geometry, the angular diversity relative to the first order is given by the projection lens exit pupil aperture D and the distance along the optical axis z.

  FIG. 55 shows a schematic diagram of the use of a rotating k-vector grating (eg, HBE-I grating) to maximize the peak DE of in-coupled light. The k vector rotation in the grating elements 572A-572C of the waveguide portion 570 is indicated by the different orientations of the k vectors 573A-573C. The surface grating pitch P is constant along the length of the waveguide. The grating vector is optimized to diffract rays 1360A-1360 representing the chief and off-axis rays with high diffraction efficiency. The use of a rotational k-vector allows for high-efficiency input coupling to the grating and optimizes the beam divergence angle so that the waveguide thickness can be minimized. This requires balancing the waveguide thickness, the input grating angular bandwidth, and the viewing angle spread at any given point on the input grating. The low angular response of the grating as the k-vector is rotated (surface pitch is maintained) prevents output coupling, thereby minimizing the waveguide thickness.

  FIG. 56 is a schematic diagram illustrating exemplary ray propagation through a waveguide portion 580 that includes a rotated k-vector grating. The dimension separating points X and Y is approximately twice the waveguide thickness at the 45 ° TIR angle of the waveguide. The propagation path is indicated by rays 1370-1371. Point X corresponds to the point at which ray 1370 couples into the grid. The chief ray angle may be required to change by more than the FWHM angular bandwidth of the grating. At point Y, the ray angle is off Bragg. Therefore, an interdependent output coupling cannot be obtained with Y. The design objective is to ensure maximum input coupling at X, while at the same time designing the distance along z to minimize angular diversity and to minimize grid thickness without mutual outcoupling at position Y. Is to be able to do it.

  57-59 show perspective views of an embodiment that uses k-vector rotation to provide exit pupil magnification in an orthogonal direction. FIG. 57 is a plan view showing HBE590 and VBE591. FIG. 58 shows a schematic side view of HBE and VBE. FIG. 59 shows a developed view of HBE showing beam propagation inside the waveguide. A Cartesian XYZ coordinate system is provided for reference. The lossy output grid of HBE is indicated by 592. The input grid is indicated by 593. The input and output gratings have a common surface grating pitch. For Z = 0 and Z = L along the HBE, it may be desirable to have high input coupling within the VBE. Since the angular diversity decreases as the limit Z = L is approached (the angular diversity scales as 1 / L), the grating thickness can be increased. This is because the beam filling W at Z = L is much larger than at Z = 0, so that the light that is incoupled into the VBE with thickness t is larger in the waveguide after the incoupling. It is beneficial because it works. A thicker grid reduces outcoupling. Angle diversity can be used to fine tune the thickness of the VBE.

  60-62 show an apparatus for manufacturing the waveguide shown in FIGS. 57-59. Referring to FIG. 60, all points along ray 1390A, such as 600A-602C, must have the same surface grid pitch and a parallel k-vector. The k vector is rotated in a plane orthogonal to the z axis. FIG. 60 shows an apparatus for manufacturing HBE using a contact printing process. FIG. 61A shows a cross section of the Z = L end of HBE590 with the wide end of the cone-shaped lens positioned on the upper side. FIG. 61B shows a plan view of the lens, and FIG. 61C shows the Z = 0 end of the HBE where the narrow end of the lens is positioned on the upper side. The lattice layer is indicated by 611 and the rotated lattice is indicated by details 612. The paths of the collimated recording beam incident on the lens are indicated by 1391, 1393. The convergent rays used to form the rotated grating are indicated by 1392, 1394. The lens is shown as a refractive element. In one embodiment, an equivalent prescription diffractive lens may be used. Cone-shaped lens contact print setups may require careful consideration to overcome holographic off-axis aberrations that may need to be compensated for during the recording stage.

  FIG. 62 shows the formation of a conical section from the cone at the apex 620 and the base 621. The cone is shown in side view in FIG. 62A showing the cut optical elements and cut lines, and in front view in FIG. 62B showing the cut optical elements as well. A view of the cutting optics projected from the bottom along the cut line is shown in FIG. 62C. A conical section is obtained by cutting parallel to the cone edge. At this time, the light beam parallel to the z-axis remains unpolarized on the y-axis (that is, does not involve a refraction component). The magnitude of deflection (refraction) on the x-axis is a function of the position at which the light ray collides with the y-axis.

  63 to 66 show the principle of k-vector rotation. FIG. 63 shows the basic structure of a waveguide according to the principles of the present invention. The waveguide 630 includes a plurality of grating thin plates that can be grouped into an input grating 631 and an output grating 632. In any case associated with each Bragg grating, there is a surface grating indicated by 633,634. Input image light is represented by collimated beams 1400 to 1402, where letters A and B indicate the excessive rays of each beam. The corresponding output image light is represented by three collimated beams 1410-1412 with letters A and B that also indicate excessive rays. The output beam has a pupil that is greatly enlarged due to the extraction of light along the waveguide as described above. In general, the output grating is very long and extends over most of the length of the waveguide. The DIGI-I and HBE-I gratings described with respect to particular embodiments are examples of input gratings, while the DIGI-O and HBE-O gratings are examples of output gratings. In each group, a plurality of lattices may be stacked adjacent to each other or arranged in layers. FIG. 64 is a diagram of a waveguide in which input gratings 635A to 635C are stacked. Each lattice has a unique k vector 636A-636C. The k vector 636A provides high diffraction efficiency for the field of view centered in the beam direction 1401. The k vectors 636B and 636C are optimized for high diffraction efficiency near the respective incident beam directions 1400 and 1402. Thus, the input image is sampled into a plurality of angular intervals. Each angular interval is associated with an effective exit pupil that is part of the entire pupil.

  In one embodiment shown in FIG. 65, the input gratings are arranged adjacent to each other along the waveguide propagation direction. The waveguides are indicated by 637A-637C and the k vector is indicated by 638A-638C. The present invention has created the term "rotated k vector" to describe the changing directionality of the k vector along the waveguide propagation direction.

  The principles shown in FIGS. 64-65 may be applied to the output grid shown in FIG. Here, the output grid comprises a plurality of adjacently arranged grids, such as 639A-639C with k vectors 640A-640C. In another embodiment of the present invention, the output grating may be composed of a stacked grating based on the principle of FIG.

  The method of displaying an image is one embodiment of the present invention according to the basic principles of the present invention and is illustrated in the flow diagram of FIG. Referring to the flow diagram, the method may comprise the following steps.

  Step 650 includes providing a first optical substrate for propagating light in a first direction, a second optical substrate for propagating light in a second direction, and an input image node (IIN); The first and second optical substrates comprise at least one waveguiding layer, each of the at least one waveguiding layer comprising at least one grating lamina and at least one grating lamina comprising a passive mode SBG.

  In step 651, IIN is used to provide image modulated light.

  In step 652, coupling image light to a first optical substrate;

  In step 653, light is extracted from the first optical substrate along a first direction;

  In step 654, image light is coupled to the second optical substrate;

  Step 655 extracts light from the first optical substrate along a second direction;

In step 656, image light for a display is provided.
Summary of some embodiments

  At least some embodiments provided herein use separate vertical and horizontal beam expansion waveguides to provide an expanded exit pupil (or eyebox). Each waveguide includes an input Bragg grating and an output Bragg grating. Each of the waveguides may include a plurality of waveguide layers. In color embodiments, a separate monochromatic waveguide may be used for each primary color. Another option for providing color is to record in the waveguide a multi-grating where holograms with different color recipes are superimposed.

  The collimated image light is supplied to a horizontal beam expanding waveguide having a field of view (FOV) defined by the microdisplay and collimating optics. The present invention allows input or “coupled” optical elements to be constructed in many different ways, ranging from traditional optical lens-mirror structures to more compact structures that are entirely based on diffractive (holographic) optical elements. To do.

  Horizontal beam expanding waveguides are lossy. That is, the horizontal beam expanding waveguide uniformly extracts light from the waveguide along its length. The extracted light is then coupled into a vertically expanding waveguide.

  Similarly, a lossy vertical expanding waveguide completes the beam expansion to provide an exit pupil that is expanded vertically and horizontally.

  An inherent feature of the present invention is that all of the above can be achieved using a passive grating (however, in some applications, the use of a switchable grating is still optional). Traditional passive gratings are useless. The main advantage of using a passive SBG is that the refractive index modulation of the grating can be adjusted with a wide range of diffraction efficiencies corresponding to very low to very high values. The high refractive index modulation of SBG results from the band where the polymer rich region and the LC rich region forming the Bragg fringe are alternately switched.

  While lossy gratings are known in the prior art, the present invention is unique in that it achieves efficient and uniform extraction from the waveguide by varying the thickness (and modulation) across the grating. In its simplest case, this entails forming a wedge-shaped grating (by tilting the cell wall) so that the hologram thickness increases in the propagation direction. In general, the grating thickness may vary from 1.0-1.2 microns up to 2.8-3.0 microns, with the lowest thickness at the lowest efficiency (maximum angular bandwidth) Bring. The present invention is more sophisticated by using two wedge angles to change the thickness in orthogonal directions, or in a more general manner, by applying curvature to one or both faces of the grating. Allows extraction control.

  Further inherent features of the beam expansion gratings can make them very thin (much less than 3 microns), thereby providing a very wide diffraction efficiency angular bandwidth, resulting in FOV Is that it becomes wider. By optimizing the thickness and refractive index modulation, all the required grating properties required for the display, i.e. very high efficiency for coupling to the grating, and efficient and uniform required for beam expansion A large dynamic range for extraction can be satisfied.

  A very important feature of the present invention that affects the inefficiency and form factor of image transfer is the use of image sampling. The coupling of image light into a waveguide with a wide FOV usually results in some loss of image angle content due to the limited angular range that can be efficiently propagated under the waveguide. Some of this light may be coupled out of the waveguide. The present invention overcomes this problem by sampling the input image into multiple angular intervals, each angular interval having an effective exit pupil that is part of the size of the entire pupil, and the thickness of the waveguide. Is correspondingly reduced.

  Independently, the present invention combines a fixed frequency surface grating with a rotating k vector along the waveguide at the input and output of each waveguide. The surface grating is the intersection of the Bragg fringe and the substrate edge and corresponds (almost) to the basic light beam optical element of the waveguide. The k vector is a direction perpendicular to the Bragg grating and corresponds to the diffraction efficiency vs. angular characteristics of the grating. By changing the k-vector direction along the waveguide propagation direction (k-vector rotation), first, it is possible to efficiently couple image light to the waveguide, and secondly, it is necessary for in-coupling. All angular content can be transmitted under the waveguide with high efficiency. The k-vector rotation is preferably augmented by the lattice thickness control described above. To our knowledge, this principle does not apply in the prior art.

  For color imaging, color can be implemented in separate waveguides without crosstalk by having the input and output gratings of each waveguide have the same surface grating frequency as described above. This is considered an inherent feature of the present invention.

  In general, propagation of angular content under the waveguide is one or more of the following: grating thickness, refractive index modulation, k-vector rotation, surface grating period, and hologram-substrate refractive index difference. It can be optimized by fine-tuning one or more.

The apparatus and method described herein may be applied to HMD, HUD, and HDD.
Exemplary embodiments

  Various aspects of the devices, systems, and methods described herein may be further described in various embodiments given below.

  In one embodiment, the first optical substrate selectively samples a portion of the image modulated light, each portion being characterized by either an angular region or a spatial region.

  In one embodiment, at least one grating lamina on each optical substrate diffracts light from the TIR path and an input grating adapted to diffract light coupled to the substrate into the TIR path. An output grid adapted to exit from the substrate.

  In one embodiment, the extraction from the second substrate is performed through the front surface of the waveguiding layer.

  In one embodiment, the extraction from the second substrate is performed through the waveguide layer edge.

  In one embodiment, the lattice vector of the lattice sheet on the first substrate is in a plane that is substantially orthogonal to the front surface of the first substrate.

  In one embodiment, the lattice vector of the lattice sheet on the first substrate is in a plane that is substantially parallel to the front surface of the first substrate.

  In one embodiment, the waveguiding layer is a transparent dielectric.

  In one embodiment, the waveguiding layer propagates monochromatic light.

  In one embodiment, the first, second, and third waveguide layers are on at least one of the first or second substrate for the purpose of propagating red light, green light, and blue light. Provided.

  In one embodiment, the first and second waveguide layers are provided on at least one of the first and second substrates for the purpose of propagating red light and blue / green mixed light.

  In one embodiment, at least one waveguide layer of the first or second substrate sandwiches a half-wave film therebetween.

  In one embodiment, at least one waveguide layer of the first or second substrate has an air gap therebetween.

  In one embodiment, the grid sheets on at least one of the first or second substrates multiplex at least two different monochromatic recipe grids.

  In one embodiment, the grating lamina on at least one of the first or second substrates multiplex at least two different color gratings.

  In one embodiment, the first substrate performs pupil magnification along a first direction, and the second substrate performs pupil magnification along a second direction.

  In one embodiment, the light extracted from the first and second substrates provides uniform illumination in any viewing direction.

  In one embodiment, each grating on at least one of the first substrate or the second substrate has first and second diffraction states. The first diffraction state is characterized by a high diffraction efficiency, and the second diffraction state is characterized by a low diffraction efficiency.

  In one embodiment, the diffractive state occurs when an electric field is applied across the grating, and the non-diffractive state exists when no electric field is applied.

  In one embodiment, the non-diffractive state occurs when an electric field is applied across the grating, and the diffractive state exists when no electric field is applied.

  In one embodiment, the first and second propagation directions are orthogonal.

  In one embodiment, at least one of the substrates is curved in at least one orthogonal plane.

  In one embodiment, at least one of the waveguiding layers includes a beam splitter sheet.

  In one embodiment, a quarter wave film is added to at least one front surface of the waveguiding layer of either the first substrate or the second substrate.

  In one embodiment, a reflective thin film coating is applied to at least one front surface of the waveguiding layer of either the first substrate or the second substrate.

  In one embodiment, the first coupling means comprises at least one lattice lamina that substantially overlaps a portion of the first substrate.

  In one embodiment, the first coupling means comprises at least one grating lamina disposed in the waveguiding layer.

  In one embodiment, the first coupling means comprises at least one grid sheet. Each grid sheet comprises at least two multiple grids of different formulations. Each lattice sheet substantially overlaps a portion of the first substrate.

  In one embodiment, the second coupling means comprises at least one lattice lamina that substantially overlaps the first substrate.

  In one embodiment, the second coupling means comprises at least one grid sheet. Each grid sheet comprises at least two multiple grids of two different formulations. Each lattice sheet substantially overlaps a portion of the first substrate.

  In one embodiment, the second coupling means is disposed in the second substrate.

  In one embodiment, the lattice vector of the lattice sheet in the first substrate is in a plane substantially parallel to the front surface of the substrate, and the first substrate lattice provides the second coupling means.

  The present invention may be used to provide one eyepiece for HMD, HHD, or HUD.

  In one embodiment, at least one grating in the first or second substrate encodes the refractive power.

  In one embodiment, the second substrate is embedded in the wind screen.

  In one embodiment, the waveguiding layer has at least one front surface that contacts the nanoporous membrane.

  A display according to the principles of the present invention may further comprise an eye tracker.

  A display according to the principles of the present invention may further comprise a beam homogenizer.

  In one embodiment, the input image node comprises a microdisplay, a laser, and collimating optics.

  In one embodiment, the grating lamina is a switchable Bragg grating.

  In one embodiment, the grating lamina used on at least one of the first or second substrates is a non-switchable Bragg grating recorded on HPDLC material.

  In some embodiments described herein, a POLYMER LIQUID CRYSTAL POLYMER SLICE (“POLICRYPS”) may be used instead of HPDLC material.

  HPDLC materials are characterized by alternating the bands of LC rich materials (eg, high and low polymer concentrations) and polymer rich materials (high and low LC concentrations). May be. Since LCs often have droplet morphology, HPDLC has two problems: scattering from LC droplets and low lattice constants (which can ultimately limit peak diffraction efficiency) You may be hit. A new class of materials, an example of which is POLICRYPS, combines LC and polymers to give a more uniform morphology that overcomes both of the previous problems. The lattice is formed by a diffusion process similar to that produced in HPDLC, but the end result in POLICRYPS is a lattice with bands that alternate between uniform highly aligned LC and uniform polymer. May be. Particulate scattering losses can be nearly eliminated if not completely due to the lack of LC droplets. The grating may have a very high contrast with refractive index modulation close to the theoretical limit set by bulk LC birefringence. As a result, diffraction efficiency values as high as about 98% (or even higher in some cases) can be easily obtained.

  A grid pitch that covers the target area in a practical display can be obtained without difficulty, and in one embodiment, in one embodiment, the material maintains a small pitch on the order of 0.2 microns and a high pitch on the order of 15 microns. Also good. Electro-optically, POLICRYPS can be similar to conventional HPDLC. In some cases, the POLICRYPS switching speed may be higher than HPDLC, and the switching voltage is at least equal to or lower than the HPDLC switching voltage. In one embodiment, like a HPDLC grating, a POLICRYPS grating may be utilized for both transmission and reflection, and may be implemented in a waveguide. The holographic recording process in POLICRYPS may be the same as that in HPDLC and may involve standard commercial monomers and LC. In one embodiment, one challenge with POLICRYPS is that high temperature processes may be required. In this embodiment, the temperature must be high enough to maintain isotropic mixing and to prevent an isotropic-nematic transition during exposure.

  POLICRYPS was developed at LICRYL (Liquid Crystals Laboratory, IPCF-CNR), Center of Excellence and Department of Physics, University of Calabria, Italy). An example of POLICRYPS is described in Capto, R. et al., Journal of Display Technology, Vol. 2, no. 1, 2006, pages 38-50. Further details of POLICRYPIS can be found in the title “Holographic Diffraction Gratting, Process for Its Preparation and Opto-Electronic Incorporation” published on January 25, 2007, which is incorporated herein by reference in its entirety. , R. et al. In US Patent Application No. 2007/0019152.

  Another uniform-form grid technology that may be used is the Polymer Liquidar PolymerElectricalHolePolymerHyperMlMlMlPlM.Essentially developed by Fraunhofer Institute for Applied Polymer Research, Potsdam (Germany). In one embodiment, POLIPHEM is similar to POLICRYPS in basic morphological and electro-optical. One advantage of using POLIPHEM over POLICRYPS is that POLIPHEM can in some cases avoid the high temperature processes required by POLICRYPS by optimizing LC and monomer properties and ratios in material formulation. Is a point. Details of materials and methods for making POLIPHEM grids are published in January 2006, “Method for the Preparation of High Efficient, Tunable and Switchable Element Elements,” which is incorporated herein by reference in its entirety. Can be found in International Patent Publication No. 2006002870 (PCT / EP2005 / 006950) by Stumpe, J et al. Entitled “Liquid Crystal Compositions”.

  In one embodiment, it may be desirable for the gratings described herein to provide both high diffraction efficiency and a wide angular bandwidth. However, in one embodiment, these two goals mean that the grating must be thin over a wide angular bandwidth, but as the thickness is reduced, the thinner grating becomes a gradual decrease in diffraction efficiency. Conflict in that it can be hit. One solution is to stack a plurality of thin gratings so that each grating can diffract the zeroth order light from the grating beneath it, thereby ultimately diffracting most of the input light. be able to. In some embodiments, the lattice layers may be separated by spacers. Such a layered grating structure is equivalent to diffraction by a thick or volume (ie Bragg) grating with at least one advantage of a fairly wide bandwidth provided by using a thin grating such as a basic building block. It may be considered to be.

  In one embodiment, the thin grating may desirably operate in a Bragg form (rather than a thin grating according to the Ramanus form) to avoid higher order diffraction. In one embodiment, when thin gratings act in a Ramanus form, the relative phase matching of the diffraction orders as they propagate through the layers results in a + 1st order intrinsic notch diffraction response (of Bragg incidence). Careful optimization of thickness and pitch may be used to do so. In other embodiments, the Bragg grating may be recorded with a layered grating structure known as a layered volume holographic optical element (SVHOE). An example of SVHOE is Nordin, G., which is incorporated herein by reference in its entirety. J. et al. Opt Soc. Am. A. , Vol. 9, NO. 12, December 1992, described on pages 2206 to 2217

A more complete understanding of the present invention can be obtained by considering the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like parts, and in which: For the purpose of clarity, details regarding technical materials known in the technical field related to the present invention have not been described in detail.
Further embodiments

  The following embodiments are cited from the claims of provisional application 61 / 849,853 filed Apr. 2, 2013, which is incorporated herein by reference in its entirety.

  1. In an apparatus for displaying an image, a first optical substrate comprising an input image node for providing image-modulated light and at least one waveguide layer, each of the waveguide layers delivering light to a first A first optical substrate comprising at least one grating lamina propagating in a direction, each of the waveguide layers adapted to extract light from the first substrate along the first direction; A second optical substrate comprising at least one waveguide layer, wherein each of the waveguide layers propagates light in a second direction, and each of the waveguide layers transmits light from the second substrate to the A second optical substrate comprising at least one grating lamina adapted to extract along a second direction; and first optical means for coupling the image modulated light to the first substrate , The light extracted from the first substrate is the second And a second optical means for coupling the plate, device.

  2. The apparatus of embodiment 1 wherein the first optical substrate selectively samples a portion of the image modulated light, wherein each portion is characterized by either an angular region or a spatial region.

  3. The at least one grating thin plate in each of the optical substrates diffracts light from the TIR path out of the input grating configured to diffract light coupled to the substrate into the TIR path. 2. The apparatus of embodiment 1 comprising an output grid configured as described above.

  4). The apparatus of embodiment 1, wherein the extraction from the second substrate is performed through the front surface of the waveguiding layer.

  5. The apparatus of embodiment 1, wherein the extraction is performed from a second substrate through a waveguide layer edge.

  6). The apparatus of embodiment 1, wherein the lattice vector of the lattice lamina on the first substrate is in a plane substantially orthogonal to the front surface of the substrate.

  7). The apparatus of embodiment 1, wherein the lattice vector of the lattice lamina on the first substrate is in a plane substantially parallel to the front surface of the substrate.

  8). The apparatus of embodiment 1 wherein the waveguiding layer is a transparent dielectric.

  9. The apparatus of embodiment 1 wherein the waveguiding layer propagates monochromatic light.

  10. The apparatus of embodiment 1, wherein the first, second, and third waveguide layers are provided on at least one of the substrates for propagating red light, green light, and blue light.

  11. The apparatus of embodiment 1, wherein the first and second waveguide layers are provided on at least one of the substrates for propagating red light and mixed blue / green light.

  12 The apparatus of Embodiment 1 wherein at least one of the first and second substrates has a half-wave film in between.

  13. The apparatus according to Embodiment 1, wherein at least one of the first and second substrates has a gap therebetween.

  14 The apparatus of embodiment 1, wherein the grating lamina on at least one of the first or second substrates comprises a multiple grating of at least two different monochromatic recipes.

  15. The apparatus of embodiment 1, wherein the grating lamina on at least one of the first or second substrates comprises at least two multi-gratings of different colors.

  16. The apparatus according to embodiment 1, wherein the first substrate performs pupil enlargement along the first direction, and the second substrate performs pupil enlargement along the second direction.

  17. The apparatus according to Embodiment 1, wherein the light extracted from the first and second substrates performs uniform illumination in any viewing direction.

  18. Each grating in at least one of the first substrate or the second substrate has a first diffractive state, the first diffractive state is characterized by a high diffraction efficiency, and the second diffractive state The device of embodiment 1, wherein the is characterized by low diffraction efficiency.

  19. The apparatus of embodiment 17, wherein the diffractive state occurs when an electric field is applied across the grating, and a non-diffractive state exists when no electric field is applied.

  20. The apparatus of embodiment 17, wherein the non-diffractive state occurs when an electric field is applied across the grating, and the diffractive state exists when no electric field is applied.

  21. The apparatus of embodiment 1, wherein the first and second propagation directions are orthogonal.

  22. The apparatus of embodiment 1, wherein at least one of the substrates is curved in at least one orthogonal plane.

  23. The apparatus of embodiment 1, wherein at least one of the waveguide layers comprises a beam splitter sheet.

  24. The apparatus of embodiment 1, wherein a quarter-wave film is added to at least one front surface of the waveguide layer of either the first substrate or the second substrate.

  25. The apparatus of embodiment 1, wherein a reflective thin film coating is applied to at least one front surface of the waveguiding layer of either the first substrate or the second substrate.

  26. The apparatus of embodiment 1, wherein the first coupling means comprises at least one lattice lamina that substantially overlaps a portion of the first substrate.

  27. The apparatus of embodiment 1, wherein the first coupling means comprises at least one grating lamina disposed in the waveguiding layer.

  28. Implementation wherein said first coupling means comprises at least one grid lamina, each grid lamina comprises at least two multiple grids of two different formulations, each grid lamina substantially overlapping a portion of said first substrate. Apparatus of form 1.

  29. The apparatus of embodiment 1, wherein the second coupling means comprises at least one lattice lamina that substantially overlaps the first substrate.

  30. The embodiment of Embodiment 1 wherein the second coupling means comprises at least one grating lamina, each grating lamina comprises at least two multiple gratings of two different prescriptions, and each grating lamina substantially overlaps the first substrate. apparatus.

  31. The apparatus of embodiment 1 wherein the second coupling means is disposed within the second substrate.

  32. The apparatus of embodiment 1 wherein the lattice vector of the lattice lamina on the first substrate is in a plane substantially parallel to the front surface of the substrate, and the first substrate lattice provides the second coupling means.

  33. The apparatus of embodiment 1, wherein the apparatus forms one eyepiece of HMD, HHD, or HUD.

  34. The apparatus of embodiment 1, wherein at least one grating in the substrate encodes refractive power.

  35. The apparatus of embodiment 1, wherein the second substrate is embedded in a windscreen.

  36. The apparatus of embodiment 1, wherein the waveguiding layer has at least one front surface in contact with the nanoporous membrane.

  37. The apparatus of embodiment 1, further comprising an eye tracker.

  38. The apparatus of embodiment 1, further comprising a beam homogenizer.

  39. The apparatus of embodiment 1 wherein the input image node comprises a microdisplay, a laser, and collimating optics.

  40. The apparatus of embodiment 1, wherein the lattice lamina on at least one of the first or second substrates is SBG.

  41. The apparatus of embodiment 1, wherein the grating lamina on at least one of the first or second substrates is a non-switchable Bragg grating recorded in HPDLC material.

42. The apparatus of embodiment 1, wherein the lattice lamina on at least one of the first or second substrates is an SBG recorded in reverse mode material.
Cited references

  The following patent applications are hereby incorporated by reference in their entirety:

  US Provisional Patent Application No. 61 / 687,436, filed April 25, 2012 by the present inventors entitled WIDE ANGLE COLOR HEAD MOUNTED DISPLAY, also referenced by applicant's serial number SBG109 ;

  US Provisional Patent Application No. 61 / 689,907, filed April 25, 2012 by the present inventors entitled HOLOGRAPIC HEAD MOUNTED DISPLAY WITH IMPROVED IMAGE UNIFORMITY, also referenced by applicant's docket number SBG113A Specification;

  PCT Application No. US2008 / 001909 having an international filing date of 22 July 2008 entitled LASER ILLUMINATION DEVICE;

  PCT application US 2006/043938 entitled METHOD AND APPARATUS FOR PROVIDING A TRANSPARENT DISPLAY;

  PCT Application No. PCT / GB2010 / 001982 entitled COMPACT EDGE ILLUMINATED EYEGLASS DISPLAY;

  US Provisional Patent Application No. 61/573, filed August 24, 2012 by the present inventors, entitled IMPROVEMENTS TO HOLOGRAPIC POLYMER DISPRED LIQUID CRYSTAL MATERIALS AND DEVICES, also referenced by applicant's docket number SBG104 No. 066;

  PCT Application No. PCT / GB2010 / 002023 filed on November 2, 2010 by the present inventors entitled APPARATUS FOR REDUCING LASER SPECKLE;

  PCT Application No. PCT / GB2010 / 000835 having an international filing date of 26 April 2010 entitled COMPACT HOLOGRAPIC EDGE ILLUMINATED EYEGLASS DISPLAY (also referred to by applicant's docket number SBG073PCT);

  U.S. Patent No. 6,115,152 entitled HOLOGRAPIC ILLUMINATION SYSTEM, issued September 5, 2000;

US Provisional Patent Application No. 61 / 796,795, entitled COMPACT LASER ILLUMINATOR INCORPORATION A DESPCKLER, having a filing date of November 20, 2012.
Further examples

  FIG. 68 is a ray trace of a monochromatic version of the structure. FIG. 69 shows the approximate dimensions of the IIN of FIG. FIG. 70 provides a development view of the optical layout of FIG.

  The IIN stop is formed by controlling the profile of the input illumination. Currently, there is no hard physical aperture in the projection optics. The advantage of the projection stop is a reduction in waveguide thickness. The stop is projected midway above the HBE to minimize the aperture diameter in the VBE, thereby minimizing the VBE aperture width relative to the DigiLens waveguide coupler. That is, the reduction in the width of the first axis expander limits the thickness of the second axis expander optical element. 71A and 71B illustrate the formation of a projection stop inside the HBE using a simplified thin lens display of a microdisplay projection optic.

In one embodiment, the stepped reflection profile below the SBG layer is used to control (or help) the grating DE change along the length (usually achieved with an SBG grating using refractive index modulation). ) This can be beneficial in cases such as HBE, where a low percentage of light is outcoupled at the first bounce but a high percentage is outcoupled at the other end of the waveguide.
Embodiment using striped HBE

In one embodiment, the HBE has a coupling grating at its input, and the alternating SBG stripes of two different recipes are tilted at 45 ° in the plane shown in FIG. Although fringes are shown equally spaced, their size and spacing may be varied for better illumination and image sampling control. However, the fringes should not be made very narrow as this can affect the MTF. In general, the stripe geometry may require careful optimization. This is because, for example, there are rays from the fringe tips that can cause a phase difference in the pupil. The input SBG requires a large angular bandwidth and high efficiency, while the DigiLens passive grating is lossy. Although the angular bandwidth of the grating has a significant center-to-edge variation, extraction from the passive grating causes more light to be diffracted from the center of the extraction beam, thereby increasing the effect of the illumination profile at the end of the waveguide. Is found to result in a general reversal. This effect can be used to benefit in balancing the entire lighting profile. FIG. 73 shows beam propagation from the IIN through a single layer of DigiLens showing the four direction changes that occur along the path to the exit pupil. Numbers 1 to 7 are attached to the optical path.
Geometric properties of FOV, eyebox and pupil distance

The near eye geometry of the proposed helmet mounted display is shown in the plan view of FIG. 74, the side view of FIG. 75, and the front view of FIG. FIG. 77 also shows the relationship between FOV, pupil distance, and DigiLens (registered trademark) aperture with respect to the eye box. Note that the DigiLens (registered trademark) aperture scales with the pupil distance.
Binocular overlap

As shown in FIGS. 78 and 79, partial binocular overlap may be provided using converging or diverging optical elements. In any case, the binocular overlap can give a contrast improvement of up to 1.4 times. Convergence overlap may be better to avoid binocular conflict. As a very rough guide, most wide-angle functions may require only a low overlap, while most magnification functions (typically arm length) may require a high overlap. In general, published data versus work outcomes for FOVs are often anecdotal or limited to a few specific samples. Extrapolation of data from one application area to another application area can be dangerous. There are no studies that consider the trade-off between FOV and work output for a particular type of display. As a result, the effects of eyeboxes, geometric distortions, form factors, etc. are not reflected in the literature at all. The eye tends to stay within the impulsive eye movement range (from 0 ° up to about ± 10 ° to ± 15 °). Beyond this range, the head tends to move to re-center the image. If a head tracker is provided, all important information must be related to the saccade area. Some applications require a balance between proper perimeter cue display and central image quality. One study suggests that binocular rivalry, such as running (shadowing near the edge of the overlap area), will begin to be a problem for a significant number of users when the binocular overlap is below about 20 °. To do. HWD overlap in the range of 20-25 has been selected to maximize the entire horizontal field of view while minimizing the risk of binocular conflict.
Medial interpupillary distance (IPD)

The medial interpupillary distance (IPD) target is designed to have no medial interpupillary distance adjustment in the majority (90%) of the adult population. More than 90% of the adult population has an IPD in the range of 57 mm to 70 mm (± 6.5 mm range). The change in pupil position due to eye roll ± 20 ° is ± 4.5 mm. The allowable range (budget) of helmet placement / visor slip is ± 6.4 mm. Alignment uses the formula: Alignment = √ [(IPD 90% + Eye Roll) 2 + Slip2] = √ [(6.3 mm + 4.5 mm) ² +6.4 mm ² ] = + / − 12.5 = 25.0 mm May be estimated. In 10% of the population whose IPD is out of range, sufficient vision is given. For optimal alignment, only one side of the field is lost for only one eye. The other eye still sees the other side of the field of view. That is, 90% of the population gets 100% overlap. The remaining 10% of the population (within 52mm to 75mm IPD) gets 100% of the field of view with some overlap depending on IPD and display alignment. In conclusion, a 25 mm wide eyebox will be able to accept 90% of the population without any adjustment taking the alignment parameters. Increased alignment tolerance of the visor / headgear to the eye allows for a reduction in eyebox dimensions as needed. This can later make a trade-off for system brightness.
Low refractive index material

Efficient guiding requires that the TIR beam be confined between low index media. Currently available low refractive index materials such as magnesium fluoride (1.46) and silicon dioxide (1.39) are too high in refractive index to meet the strict TIR angle constraints required for full color implementation of HMD. If this is not possible, it is difficult to form and maintain voids. The proposed solution is to use a nanoporous material (mesoporous silicon). Nanoporous materials (eg, mesoporous silicon) are currently used in many optical applications, including antireflective coatings and planar optical waveguides. Their high porosity allows the formation of high quality and low dielectric constant thin films. Nanoporous materials can be formed into thin layers in a single step. In order to obtain a very low refractive index of approximately unity, the porosity needs to be very high and close to 95%. High transparency and low refractive index can be achieved simultaneously with these films. These membranes absorb water very efficiently and must be carefully sealed against moisture. The best approach may be to seal the passive grating, HWP, and material together. The SBG laboratory is also studying the potential role of nanoporous materials as high refractive index media. This increases the range of TIR angles that can be maintained in our waveguides with the potential to increase the horizontal FOV from 40 ° to about 45 °. Nanoporous materials are currently used in many optical applications including antireflective coatings and planar optical waveguides. Therefore, it makes sense to assume that the technology is accessible for our project. The manufacturing process must be convertible to manufacturing needs. Nanoporous materials can be formed in a single coating step. Alternatively, a multilayer structure with a stepped refractive index can be used. The SBG laboratory is also studying the potential role of nanoporous materials as high refractive index media. This increases the range of TIR angles that can be maintained in our waveguide.
Conclusion

  All documents and similar materials cited in this application, including but not limited to patents, patent applications, papers, books, technical books, and web pages, are subject to the format of such documents and similar materials. Rather, the entirety of which is expressly incorporated herein by reference. One or more of the incorporated literature and similar materials may differ from this application, including, but not limited to, certain terms, terminology, techniques described, or the like. In case of conflict, this application will prevail.

  Although the present technology has been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various substitutions, modifications, and equivalents, as will be appreciated by those skilled in the art.

  While various embodiments of the invention have been described and illustrated herein, one of ordinary skill in the art will understand that the functions described herein may be performed and / or the results described herein. Various other means and / or structures to easily obtain and / or obtain one or more of the advantages described herein are easily recalled, and such variations and / or modifications Each is considered to be within the scope of the embodiments of the invention described herein. More generally, as will be readily appreciated by those skilled in the art, all parameters, dimensions, materials, and configurations described herein are intended to be exemplary and actual parameters The dimensions, materials, and / or forms may depend on the particular application or applications in which the teachings of the invention are used. Those skilled in the art will recognize many equivalents to the specific embodiments of the invention described herein. Therefore, it is to be understood that the foregoing embodiments are given by way of example only, and that, within the scope of the appended claims and their equivalents, embodiments of the present invention have been specifically described and are within the scope of the claims. It may be implemented in ways other than those described. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. Also, any combination of two or more such features, systems, articles, materials, kits, and / or methods is such that such features, systems, articles, materials, kits, and / or methods are mutually related. If not inconsistent, they are included in the scope of the present disclosure.

  Also, the techniques described herein may be embodied as a method, and at least one embodiment of such a method has been given. The acts performed as part of the method may be ordered in any suitable manner. Accordingly, embodiments may be configured in which acts are performed in a different order than the illustrated order, and such embodiments may be implemented in any number of ways, even if shown as a continuous act in the illustrated embodiment. It may also include performing these actions simultaneously.

  All definitions defined and used herein are understood to govern over dictionary definitions, definitions in the literature incorporated by reference, and / or the ordinary meaning of the defined terms. Should be.

  The indefinite articles "a" and "an" as used herein in the specification and claims mean "at least one" unless the contrary is clearly suggested. Should be understood to do. Any ranges listed herein are inclusive.

  The terms “approximately” and “about” as used throughout this specification are used to represent and take into account slight variations. For example, the terms are ± 5% or less, such as ± 2% or less, such as ± 1% or less, such as ± 0.5% or less, such as ± 0.2% or less, such as ± 0.1% or less, such as ± 0.05% or less can be shown.

  As used herein in the specification and in the claims, the phrase “and / or” refers to the elements so coupled, ie, in some cases connected, and in others disconnected. It should be understood to mean “one or both” of the elements present. Multiple elements described with “and / or” should be construed in the same manner, ie, “one or more” of the elements so conjoined. Optionally, other elements than those specifically identified by the “and / or” clause may be present whether or not related to those elements specifically identified. Good. Thus, as a non-limiting example, a reference to “A and / or B” when used in conjunction with an unconstrained language such as “comprising” is only A (optionally B) in one embodiment. In other embodiments, only B (optionally including elements other than A) is shown, and in still other embodiments both A and B (optionally including other elements) are shown. Including).

  As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” should be construed comprehensively, ie include at least one of many elements or lists of elements. It should be construed to include a plurality, and optionally to include items not listed further. Only terms explicitly suggesting the opposite, such as “only one of” or “exactly one of” or “consisting of” when used in the claims, Indicates to contain exactly one of many elements or lists of elements. In general, the term “or” as used herein is “any”, “one of”, “only one of”, “exactly one of”, etc. Should be construed only as indicating an exclusive option (ie, one or the other but not both). “Consisting essentially of” as used in the claims should have its ordinary meaning as used in the field of patent law.

  The phrase “at least one” as used herein in the specification and claims in connection with a list of one or more elements is at least one selected from any one or more elements in the list of elements. Should be understood to mean one element, but does not necessarily include at least one of each and every element specifically listed in the list of elements, and Do not exclude any combination of elements. This definition also applies regardless of whether an element other than the element specifically identified in the list of elements referenced by “at least one” is related to or not related to the element specifically identified. Allow that it may optionally be present. Thus, as a non-limiting example, “at least one of A and B” (or equivalently, “at least one of A or B”, or equivalently “of A and / or B At least one of them ”) can indicate at least one A optionally including a plurality (optionally including elements other than B) in the absence of B in one embodiment, In embodiments, at least one B can optionally be shown (optionally including elements other than A) in the absence of A, and in still other embodiments, optionally included. At least one A and optionally at least one B (optionally including other elements) can be shown, etc.

  In the claims and in the specification, “comprising”, “including”, “carrying”, “having”, “including”, “with”, “holding”, “consisting of”, And all transition phrases, such as the like, should be understood in a non-constraining manner, ie, including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” are not included in each of the closed transitional or semi-closed transitional phrases, as described in Section 2111.03 of the US Patent Office Manual of Patent Examination Procedures. There must be.

The claims should not be read as limited to the described order or elements unless stated to that effect. It will be appreciated that various changes in form and detail may be made by those skilled in the art without departing from the scope and spirit of the appended claims. All embodiments that fall within the spirit and scope of the following claims and their equivalents are required.

Claims (21)

In an apparatus for displaying an image,
A first optical substrate comprising at least one waveguide layer configured to propagate light in a first direction, wherein at least one of the waveguide layers of the first optical substrate transmits light to the A first optical substrate comprising at least one grating lamina configured to extract from the first optical substrate along the first direction;
A second optical substrate comprising at least one waveguide layer configured to propagate light in a second direction, wherein at least one waveguide layer of the second optical substrate transmits light to the A second optical substrate comprising at least one grating lamina configured to extract from the second optical substrate along the second direction;
The apparatus in which at least one of the lattice laminae of at least one of the first and second optical substrates comprises a passive mode SBG.   The at least one waveguide of at least one of the first and second optical substrates comprises a plurality of grating thin plates, and at least two of the plurality of grating thin plates have the same surface grating frequency. Equipment.   At least one of the grating thin plates of at least one of the first and second optical substrates is at least one of HPDLC, POLICRYPS, POLIPHEM, and SVHOE of at least one of a forward mode and a reverse mode. 2. The apparatus of claim 1 comprising a non-switching Bragg grating recorded on one.   The apparatus of claim 1, wherein both the first and second optical substrates comprise passive mode SBGs.   At least one of the first and second optical substrates includes a plurality of waveguide layers, and each of the plurality of waveguide layers includes red light, green light, blue light, blue / green mixed light, and The apparatus of claim 1, configured to propagate at least one of one of a plurality of partial fields of view (FOV).   The apparatus of claim 1, wherein at least one waveguide layer of at least one of the first and second optical substrates comprises a hologram with different color prescriptions superimposed.   The apparatus of claim 1, wherein at least one waveguide layer in at least one of the first and second optical substrates is lossy.   The apparatus of claim 1, wherein the at least one grating lamina of at least one of the first and second optical substrates has a thickness of less than about 3 microns.   The apparatus of claim 1, wherein at least one of the lattice sheets of at least one of the first and second optical substrates has a thickness that varies along a respective light propagation direction.   A device comprising the apparatus of claim 1, wherein the device is part of at least one of an HMD, a HUD, and an HDD. In an apparatus for displaying an image,
An input image node for providing image modulated light;
A first optical substrate comprising at least one waveguide layer configured to propagate modulated light in a first direction, the at least one waveguide layer of the first optical substrate comprising modulated light A first optical substrate comprising at least one grating lamina configured to extract from the first optical substrate along the first direction;
A second optical substrate comprising at least one waveguide layer configured to propagate modulated light in a second direction, wherein at least one waveguide layer of the second optical substrate is modulated light A second optical substrate comprising at least one grating lamina configured to extract from the second optical substrate along the second direction;
At least one grating lamina of the first optical substrate is configured to couple modulated light to the first optical substrate;
At least one of the grating thin plates of the second optical substrate is configured to couple modulated light extracted from the first optical substrate to the second optical substrate;
The apparatus wherein at least one of the grating thin plates of at least one of the first and second optical substrates has a k-vector that varies along a respective light propagation direction.   The apparatus of claim 11, wherein the input image node comprises at least one of a microdisplay, a laser, and a collimating optical element.   The apparatus of claim 11, wherein at least one of the lattice sheets of at least one of the first and second optical substrates has a varying thickness.   The apparatus of claim 11, wherein at least one of the grating laminae of at least one of the first and second optical substrates comprises an SBG that is in a switching mode or a passive mode.   12. The apparatus of claim 11, wherein at least one of the grating lamellas in at least one of the first or second optical substrates comprises a multi-grating of at least two different monochromatic recipes.   12. The apparatus of claim 11, comprising a plurality of grating lamellas having the same surface grating frequency but different k vectors, wherein the plurality of grating lamellas are configured to divide the input image field into a plurality of angular intervals. .   The apparatus of claim 11, wherein at least one of the first and second optical substrates is curved in at least one orthogonal plane.   The apparatus according to claim 11, wherein the light extracted from the first and second optical substrates performs uniform illumination in an arbitrary viewing direction. A method of displaying an image,
Coupling modulated light from an input image to a first optical substrate;
Extracting light from the first optical substrate;
Coupling the light extracted from the first optical substrate to a second optical substrate;
The first optical substrate includes at least one waveguide layer configured to propagate light in a first direction, and the at least one waveguide layer of the first optical substrate transmits light to the Comprising at least one grating lamina configured to extract from a first optical substrate along the first direction;
The second optical substrate comprises at least one waveguide layer configured to propagate light in a second direction, and the at least one waveguide layer of the second optical substrate transmits light to the Comprising at least one grating lamina configured to extract along a second direction from a second optical substrate;
The method wherein at least one of the grating laminae of at least one of the first and second optical substrates comprises a passive mode SBG.   20. The method of claim 19, further comprising sampling the input image into a plurality of angular intervals, each of the plurality of angular intervals having an effective exit pupil that is a portion of the overall pupil size. At least one of at least one of the grating sheets of at least one of the first and second optical substrates: grating thickness, refractive index modulation, k vector, surface grating period, and hologram The method of claim 19, further comprising improving display of the image by changing at least one of the substrate refractive index differences.

Images