Mixed Reality Combiner

Abstract

To provide an optical system of a practical XR display that is generally required to satisfy a complex mix of ergonomic, technical, and financial constraints.SOLUTION: An optical waveguide combiner has an output coupler that includes an array of embedded partially reflective dielectric mirrors expanding and coupling a virtual arbitrary color image generated by a laser display engine into a user EMB, in which the dielectric mirror is configured to have a wavelength band for each lasing band of the laser display engine that includes wavelengths of light in the lasing band, and in a range of a wavelength over which the lasing band is expected to drift, a reflectivity angular range indicative of first reflectivity, a transmittance angular range indicative of second reflectivity less than the first reflectivity, and a see-through angular transmittance range having high transmittance with respect to natural light incident on facets.SELECTED DRAWING: Figure 1E

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims the benefits under Section 119(e) of the U.S. Patent Act, relating to U.S. Provisional Application 62 / 980,469 filed on 24 February 2020 and U.S. Provisional Application 63 / 001,567 filed on 30 March 2020.

[0002] Embodiments of the present disclosure relate to an optical waveguide system configured to receive an image from a laser display engine at a relatively small input aperture, transmit the image out of the waveguide in an expanded output coupling region, and fill an enlarged eye-motion box for viewing by a user. [Background technology]

[0003] Proliferating head-mounted displays (HMDs) and smart eyewear that provide users with a variety of new forms of reality—augmented reality (AR), mixed reality (MR), and parallel reality—and are used to overlay computer-generated "virtual images" onto the "real images" of the real environment seen by the user within the user's field of view (FOV). The virtual images may, for example, provide the user with entertainment and / or informational material related to the real images, tasks performed by the user, and / or explicit or implicit user requests. Images presented to the user, including real and virtual images, may be referred to as augmented reality (XR) images, and any of the various hardware configured to provide XR images to the user may be generally referred to as XR displays.

[0004] In the optical system of an XR display, a computer-controlled display engine, such as a liquid crystal display (LCos), organic light-emitting diode (OLED), or laser-scanning (LBS) microdisplay on a silicon substrate, provides a virtual image. An optical element called a combiner is transparent to ambient light, allowing the user to see the real environment, but it receives the virtual image provided by the display engine and overlays it on the real image to provide the user with an XR image.

[0005] Generally, virtual images provided by a display engine are relatively small, having characteristic dimensions of approximately 5 millimeters or less. A combiner receives small virtual images through a relatively small input aperture, propagates the image to an output coupler, and outputs the virtual image through the combiner's exit aperture, placing it into the eye motion box (EMB). When the user's eyes are positioned within the EMB, the virtual image enters the user's retina through the user's aperture and appears in the XR image as a feature of the real image the user sees through the combiner. To fill the EMB so that the user can comfortably view the virtual image without having to struggle unnecessarily to align their eyes with the combiner, combiners are generally configured to have a relatively large, expanded aperture through which the combiner transmits many copies of the virtual image into the EMB.

[0006] Practical XR display optical systems generally need to satisfy a complex interplay of ergonomic, technical, and economic constraints. Ideally, the optical system should have a comfortably large EMB, be advantageously small, lightweight, and energy-efficient, and provide a clear virtual image free from overly distracting artifacts such as image ghosting. [Overview of the Initiative]

[0007] An aspect of one embodiment of the present disclosure relates to providing an optical waveguide combiner having an output coupler including an array of embedded dielectric partial reflection mirrors (hereinafter also referred to as facets) for extending and coupling a virtual arbitrary color image generated by a laser display engine into a user EMB. With respect to light in a wavelength band provided by a laser used by the engine to generate the virtual image, the facets are configured to reflect incident light in the user EMB with relatively high reflectivity at a first range of incident angles. At a second range of incident angles different from the first range, the facets are configured to have relatively low reflectivity and transmit light in substantially the same laser wavelength band with relatively high transmittance. The transmittance and reflectivity exhibit relatively small variability across the wavelength range of the laser wavelength band in the first and second angular ranges. The facets are formed to be substantially colorless and transmittant to visible light, also referred to as natural light from the environment. Optionally, the display engine includes at least one laser that provides the display engine with light in the red, green, and blue (RGB) bandwidths and processes the light to generate a virtual RGB color image. In one embodiment, the combiner introduces a color virtual image into the EMB with relatively high RGB image resolution and relatively low image artifact contamination.

[0008] In one embodiment, the waveguide combiner comprises a waveguide having first and second parallel internal total internal reflection (TIR) ​​surfaces. Light from the display engine enters the waveguide, is reflected from the TIR surfaces, bounces back and forth between the TIR surfaces, propagates within a waveguide field of view (wFOV) reduced along the waveguide, reaches and enters a facet. In one embodiment, the facets are parallel and evenly spaced, and are tilted at an angle of inclination measured between the normal to the TIR surfaces and the normal to the facet. The component of a ray in the wFOV parallel to the TIR normal reverses direction each time the ray bounces off the first TIR surface, and reverses direction each time the light bounces off the second TIR surface. A ray in the wFOV that has undergone an even or odd number of bounces (counted from any first bounce) before entering a given facet enters the given facet at an angle of incidence within a first range or a second range of angles of incidence, respectively. According to one embodiment of the present disclosure, a ray incident on just one facet of a first range and a second range of incident angles is selected, exits the waveguide, coupled, and incident on the EMB to provide the user with a virtual image generated by the display engine.

[0009] For convenience of presentation, the range of incident angles in which rays within the wFOV are selected to provide a virtual image may be referred to as the "image incident range." If the wFOV is oriented by TIR reflection in the waveguide to include rays propagating in the angular direction within the image incident range, it may be referred to as the "image wFOV." The range of unselected incident angles may be referred to as the "conjugate incident range," and if the wFOV is oriented by TIR reflection in the waveguide to include rays propagating in the angular direction within the conjugate incident range, it may be referred to as the "conjugate wFOV."

[0010] According to one embodiment, the tilt angle of the facet is determined to provide favorable angular separation between the image incidence range and the conjugate incidence range. The facet is configured to have a reflectance angle range, a transmittance angle range, and a facet wavelength band. For light having wavelengths in the facet wavelength band incident on the facet at an incidence angle in the reflectance angle range, the facet exhibits relatively high reflectance and relatively low dispersion with respect to changes in wavelength and incidence angle. Similarly, for light having wavelengths in the facet wavelength band incident on the facet at an incidence angle in the transmittance angle range, the facet exhibits relatively low reflectance and correspondingly high transmittance with respect to changes in wavelength and incidence angle. The facet wavelength band includes the range of wavelengths that include the laser oscillation bandwidth of the laser that the display engine processes to generate a virtual image, and the range of wavelengths over which the laser oscillation bandwidth may vary, for example, as a result of drift due to operating conditions and / or manufacturing tolerances.

[0011] This summary of the invention is provided in a brief form to introduce the selection of concepts, which will be further described in the following forms for carrying out the invention. This summary of the invention is not intended to identify the main or essential features of the subject matter of the claims, nor is it intended to be used to limit the scope of the subject matter of the claims. [Brief explanation of the drawing]

[0012] Non-limiting examples of embodiments of this disclosure are described below with reference to the accompanying drawings listed after this paragraph. Identical features appearing in two or more drawings may be labeled with the same label in the drawings in which they appear. Labels that label icons representing a given feature of an embodiment of this disclosure in a drawing may be used to refer to a given feature. Dimensions of features shown in the drawings are selected for presentation convenience and clarity and are not necessarily shown scaled.

[0013] [Figure 1A]This figure schematically illustrates a waveguide combiner according to one embodiment of the present disclosure, comprising a waveguide having an output coupler including an array of facets that expands the combiner's input aperture in one direction and provides an expanded output, the combiner transmits a virtual image received through the input aperture into the EMB. [Figure 1B] Figure 1A schematically shows a cross-section of a combiner, according to one embodiment of the present disclosure, which reflects light from a laser display engine into a user EMB. [Figure 1C] Figure 1B schematically shows an enlarged portion of the combiner in which light from the laser display engine enters the combiner, according to an embodiment of the present disclosure. [Figure 1D] Figure 1B schematically shows an enlarged portion of the combiner in which light from the laser display engine exits the combiner and enters the EMB, according to an embodiment of the present disclosure. [Figure 1E] In embodiments of this disclosure, a schematic graph of reflectance is shown as a function of the angle of incidence of light from the laser display engine on the facet shown in Figures 1A and 1C and the reflectance of the facet with respect to natural light. [Figure 1F] Figures 1A and 1B schematically show arbitrary laser oscillation bandwidths for the lasers in the display engine shown in the embodiments of this disclosure, and matching facet wavelength bands for the facets shown in the figures. [Figure 1G] In one embodiment of the present disclosure, a graph of reflectance as a function of the wavelength of the facets shown in Figures 1A and 1B is shown for the facet wavelength band of blue light. [Figure 2A] This figure schematically shows a cross-section of a waveguide combiner similar to the combiner shown in Figure 1A, according to one embodiment of the present disclosure, and includes facets tilted at an intermediate angle that reflect light from a laser display engine into the user EMB. [Figure 2B] A schematic graph of reflectance as a function of the angle of incidence of light on the facet shown in Figure 2A is shown according to one embodiment of the present disclosure. [Figure 3A]This figure schematically shows a cross-section of a waveguide combiner similar to the combiner shown in Figure 1A, according to one embodiment of the present disclosure, and includes facets tilted at a relatively large angle that reflect light from the laser display engine into the user EMB. [Figure 3B] A schematic graph of reflectance as a function of the angle of incidence of light on the facet shown in Figure 2A is shown according to one embodiment of the present disclosure. [Figure 4] A schematic perspective view of a waveguide combiner comprising a waveguide system providing two-dimensional aperture expansion according to an embodiment of the present disclosure is shown. [Modes for carrying out the invention]

[0014] In this description, unless otherwise stated, adjectives such as “substantially” and “about” that modify the condition or relational characteristics of one or more features of an embodiment of the present disclosure are understood to mean that the condition or characteristic is defined within a tolerance acceptable to the operation of the embodiment for its intended use. Where the general terms of the present disclosure are described by reference to an example instance or a list of example instances, the one or more instances referenced are by an unrestrictive example instance of the general term, and the general term is not intended to be limited to the specific example instance of the one or more instances referenced. Unless otherwise indicated, the word “or” in this specification and the claims is considered to be an inclusive “or” rather than an exclusive “or,” indicating at least one or any combination of two or more items from which it combines.

[0015] Figure 1A schematically shows a waveguide combiner 20 according to one embodiment of the present disclosure, which optionally comprises a waveguide 30 having two relatively large parallel face surfaces 31 and 32, an end face 34, and an output coupler 40 including an array of parallel, arbitrarily spaced facets 42 embedded in the waveguide. For convenience of presentation, the locations of the features of the waveguide combiner 20 may be referenced with respect to the x, y, and z axes of a Cartesian coordinate system 100.

[0016] The face surfaces 31 and 32, also referred to as the internal total internal reflection (TIR) ​​surfaces 31 and 32, are optionally assumed to be parallel to the xy plane of coordinate system 100. Facet 42 is parallel to the x-axis and, when viewed along the x-axis toward the yz plane, is rotated about the x-axis by an angle β in a counterclockwise direction. The input aperture of the waveguide 30, schematically represented by the dashed rectangle 35, is optionally parallel to the xz plane, and the output coupling region of the waveguide, schematically represented by the dashed rectangle 36, is optionally located on the face surface 32. Optionally, the waveguide combiner 20 includes a prism input coupler 50 for coupling light from a virtual image generated by the display engine 70 and entering the waveguide 30 through the input aperture 35. The output coupler 40, according to one embodiment of the present disclosure, expands the input aperture 35 in the y direction and operates to reflect light from the virtual image viewed by the user 102, which is received through the input aperture 35, propagated in the waveguide 30 to the output coupler, and enters the EMB 60 through the expanded output coupling region 36. In the following drawings, the user 102 may be represented only by the user's eyes. As an example, Figure 1 shows a waveguide combiner 20 that generates a virtual image schematically represented by a dashed rectangle 72. Natural light from the environment viewed by the user 102 through the waveguide 30 is schematically represented by a block arrow 74.

[0017] Figure 1B shows a schematic cross-sectional view of a waveguide combiner 20 along the plane AA shown in Figure 1A, according to one embodiment of the present disclosure, and the propagation of light from a virtual image 72 in the waveguide 30 to the wFOV supported by the combiner.

[0018] FIG. 1B schematically illustrates light from a virtual image 72 (FIG. 1A) within a dFOV of a display engine 70 that illuminates a face surface 51 of an input coupler 50, according to an embodiment of the present disclosure, wherein the input coupler couples the light into a waveguide 30 via an input aperture 35. A portion of the input coupler 50, the input aperture 35, and the waveguide 30, located within circle 202, is shown enlarged in FIG. 1C for easier viewing and reference. In plane A-A, the dFOV has a positive angle and a negative angle α′ + and α′ - respectively, by which the angle range Φ′=(α′ + -α′ - )=(|α′ + |+|α′ - |) is defined. The angles α′ + and α′ - are angles formed by light rays 81 and 82 (FIG. 1C), which limit the angle range of the dFOV, relative to a chief ray represented by arrow 83 of the dFOV. The light rays 81 and 82 in the waveguide combiner 20 and their respective reflections and refractions are represented by solid lines and dashed lines respectively, and may be referred to as positive and negative bounced light rays.

[0019] Relative to the chief ray 83, an angle of a light ray from the virtual image 72 (FIG. 1A) on plane A-A is considered positive when the light ray is rotated clockwise relative to the chief ray in FIG. 1B, or negative when rotated counterclockwise. The chief ray 83 is assumed to be perpendicular to the face surface 51 of the input coupler 50, and the refractive index of the material from which the input coupler and the waveguide 30 are fabricated relative to air is assumed to be equal to the same refractive index n g .

[0020] Upon entering the input coupler 50, as more clearly shown by the enlarged region 202 of the input coupler in FIG. 1C, refraction of the light reduces the angles α′ g and α′ + and α′ - and the accompanying angle range Φ′ of the dFOV by a factor that is a function of the refractive index n + and α′ -The corresponding reduction angles are α + and α - The reduced angular range that characterizes the field of view of the wFOV of light from the display engine 70 after it enters the waveguide combiner 20, is represented by Φ. Angle α + and α - This is the angle formed by the reflected rays 81 and 82 with respect to the principal ray 83 in the waveguide 30 after it has refracted and entered the input coupler 50. The reflected rays define the range of wFOV in the waveguide combiner 20, and the angle is the angle range of wFOV Φ = (|α + |+|α - The field of view wFOV is defined as follows: The field of view wFOV is shown in shaded form in Figures 1B and 1C, and in subsequent drawings.

[0021] α' + and α' - These are defined as positive and negative angles, respectively, and when they enter the input coupler 50, the corresponding angle α + and α - It should also be noted that these are defined as positive and negative angles, respectively. However, each reflection from the TIR surface 31 or 32 reverses the rotation of the bounce lines 81 and 82 relative to the principal ray 83. As a result, following the adopted convention that clockwise rotation is positive and counterclockwise rotation is negative, the bounce lines 81 and 82, after reflection from the face surface 31, each rotate at an angle α + and α - It is rotated clockwise only with respect to the principal ray 83. However, after reflection from the TIR face surface 32, the bounce lines 81 and 82 are each at an angle of -α with respect to the principal ray 83. + and -α - It is rotated counterclockwise only.

[0022] In waveguide 30, as schematically shown in Figure 1B, light rays within the wFOV are completely reflected by the TIR face surfaces 31 and 32, bounce back and forth between the TIR face surfaces 31 and 32, and reach and become incident on the facet 42 of the output coupler 40. With each bounce, the normal vector "n" to the waveguide is reflected. wThe component of a ray within the wFOV (not shown) along the line has its direction reversed. As a result, the ray within the wFOV after being reflected and bounced back from the face surface 31 has a z component in the positive z direction and may be considered in the figure as a “downward” ray propagating downward from the face surface 31 to the face surface 32. When a downward ray is included, the wFOV is oriented downward in the positive z direction. Similarly, the ray after being reflected and bounced back from the face surface 32 has a z component in the negative z direction and may be considered an “upward” ray propagating upward from the face surface 32 to the face surface 31. In the downward case, the wFOV may be distinguished and referred to as wFOV-Down, and is labeled as wFOV-D in Figure 1B and subsequent figures. Similarly, in the upward case, the wFOV may be distinguished and referred to as wFOV-Up, and is labeled as wFOV-U in Figure 1B and subsequent figures. The label "wFOV" generally refers to wFOV-U and wFOV-D.

[0023] Upon reaching output coupler 40, the upward rays within wFOV-U have normals to the facet "n f Light rays in a first range of incident angles (hereinafter also referred to as uprange) are incident on facet 42, and downward rays in wFOV-D are incident on a second range of incident angles on the facet (also referred to as downrange). According to embodiments of the present disclosure, a ray in either wFOV-U or wFOV-D is selected and reflected from the waveguide 30 by facet 42 through the output coupling region 36 and enters the EMB 60 for user viewing of a virtual image, such as a virtual image 72 (Figure 1A) generated by the display engine 70. For a ray in the selected wFOV-U or wFOV-D, facet 42 is configured to have a reflectivity that is relatively increased with respect to the incident angle of the corresponding uprange or downrange. For light waves in the unselected wFOV, facet 42 is configured to have a relatively increased transmittance. The selected wFOV may be referred to as the image wFOV, and the unselected wFOV may be referred to as the conjugate wFOV.

[0024] For example, in waveguide 30, facet 42 is oriented at a relatively small tilt angle β, and rays from wFOV-U and wFOV-D are incident on the facet from the opposite side. According to one embodiment of the present disclosure, wFOV-U is selected as the image wFOV, rays within wFOV-U are selected and reflected from waveguide 30 through the output coupling region 36, providing an output field of view O-FOV within the EMB 60 for viewing a virtual image generated by the display engine 70. For convenience of presentation and reference, the region in Figure 1B indicated by circle 204 is shown enlarged in Figure 1D.

[0025] The enlarged region 204 in Figure 1D shows an enlarged portion of the waveguide 30, including facet 42, EMB 60, and O-FOV, as seen by user 102, the angles relevant to the embodiments of this disclosure, and a virtual image such as the virtual image 72 provided by the display engine 70, as seen by the user. The figure schematically shows light from upward positive and negative reflected rays 81 and 82 that are reflected by a given facet 42 in the output coupler 40 (Figure 2A) as positive and negative reflected output rays 91 and 92 and enter the EMB 60. Rays 91 and 92 define the range of the output field of view O-FOV as seen by user 102. As an example, the O-FOV is assumed to have the same angular range Φ' as the field of view dFOV (Figure 1C) and includes light received by the prism input coupler 50 which is introduced into the waveguide 30 through the input aperture 35 by the input coupler. The reflected output lines 91 and 92 within the waveguide 30 are at an angle α with respect to the O-FOV output principal ray 93 reflected from the principal ray 83 by facet 42, respectively. + and α - This constitutes the following. Optionally, output lines 91 and 92 are also normals n of face surfaces 31 and 32. w For this, angle α + and α - The reflected output lines 91 and 92 are refracted as they enter the EMB60, at an angle α' relative to the light of the main output line 93. + and α' - It constitutes.

[0026] The negative reflected ray 82, which is incident on facet 42 and becomes a negative reflected output ray 92 when the facet reflects the light, has a normal vector n w Angle γ - Similarly, the positive reflected ray 81 that enters facet 42 and is reflected by the facet to form a positive reflected output ray 91 is normal to n w Angle γ + It forms an angle γ. - and γ + These are the inclination angle β and angle α, respectively. - and angle α + It is a function of and may also be written as follows: 1)γ - =(2β-α - ) and 2)γ + =(2β-α + ) Here, by definition, the angle α is "counterclockwise". - α has a negative value and represents a "clockwise" angle α + Note that has a positive value. The relationships provided by equations 1) and 2) are valid for any ray in the wFOV, and if α represents the angle that any ray in the wFOV makes with respect to the principal ray 83, then for any α, the angle γ may be written as follows: 3) γ = (2β - α) Therefore, the rays in wFOV-U are normal to the facet n f The angle of incidence φ u It is incident on facet 42 and may be given by the following formula. 4)φ u =(γ-β)=(β-α) The associated uprange of the incident angle selected as the incident range of the image is (β-α + ) and (β-α - This includes all angles of incidence between ) and , and may be given by the following formula. 5) Uprange = {∀φ u |(β-α + )≦φ u ≤(β-α - )} Similarly, the ray from wFOV-D has a normal nf The angle of incidence φ d The beam is incident on the facet and may be given by the following formula. 6)φ d =(γ+β)=(3β-α) The associated downrange, selected as the conjugate incidence range, may be described as follows: 7) Downrange = {∀φ d |(3β-α + )≦φ d ≤(3β-α - )}

[0027] According to embodiments of the present disclosure for moderating the appearance of artifacts associated with the virtual image in EMB60, it is advantageous that all rays in wFOV-U are incident on the same side of facet 42, and all rays in wFOV-D are incident on the same side of facet 42. The side on which rays in wFOV-U are incident on facet 42 may, according to one embodiment, be the same side or a different side of the facet on which rays in wFOV-D are incident.

[0028] For example, the waveguide combiner 20 and the field of view wFOV are configured such that all rays in wFOV-U are incident on the side of facet 42 facing the face plane 32, and all rays in wFOV-D are incident on the opposite side of the facet, i.e., the side facing the face plane 31. To provide opposite-side incidence, the waveguide combiner 20 is configured such that for any ray in the wFOV supported by the waveguide combiner, the complementary angle of γ is greater than the tilt angle β of facet 42. In notation, this is as follows: 8)(90-γ)>β When substituting γ, α + >α - It should be noted that the inclination angle β within the combiner 20 must satisfy the first constraint according to one embodiment of the present disclosure, which is given by the following formula. 9)β<(30°+α - / 3) To provide the internal total internal reflection of light in the wFOV from face surfaces 31 and 32, for any ray in the wFOV, angle γ is the critical angle θ of waveguide 30. c It must be greater than this, which is the second constraint that the inclination angle β in the combiner 20 satisfies the following: 10)γ + =(2β-α + )>θ c ⇒β>(θ c +α + ) / 2 The constraints given by equations 9) and 10) may be combined into the following single equation which provides a restriction on the tilt angle β of the combiner 20. 11)(θ c +α + ) / 2<β<(30°+α - / 3) For example, |α + |=|α - Assuming |=Φ / 2, the constraint on the tilt angle β within the combiner 20 may be expressed as a function of the field of view wFOV as follows: 12)(θ c (+Φ / 2) / 2 < β < (30° + Φ / 6) With respect to the angular range Φ' of the output field of view O-FOV seen by user 102 within EMB60, the constraint on β may be approximated by equation 11) as follows: 13)(θ c +Φ' / 2n g ) / 2<β<(30°+Φ' / 6n g ) Here, n g This is the refractive index of the material on which the waveguide combiner 20 is formed.

[0029] As a numerical example, for green light with a wavelength of approximately 550 nanometers, n g It is equal to 1.51, and the absolute value is |α + | and |α -Assume that both | and Φ' are equal to approximately 13°, and that Φ' has a paired angular range of approximately 30° and an aspect ratio of 16:9. For β equal to approximately 26°, the uprange, angle of incidence reflectance angular range favorably extends from approximately 17° to 35°, and the downrange transmittance angular range favorably extends from approximately 66° to approximately 84°. Favorably, the reflectance of rays in the uprange is approximately 9% to approximately 11%, and optionally greater than approximately 10%, and the reflectance of rays in the downrange is less than approximately 1.5%, and optionally less than approximately 1%. The angular "see-through" range for ambient natural light 74 (Figure 1A) incident on the facet favorably extends from approximately 5° to approximately 45°, exhibiting substantially colorless transmittance of approximately 85% or more.

[0030] Figure 1E shows a graph 210 of the reflectance of facet 42, which may be manufactured to substantially match the numerical specifications described above. The graph includes a reflectance curve 212 that gives the reflectance of facet 42 in waveguide 30 as a function of the angle of incidence of light on the facet. Reflectance (percent) is shown along the vertical axis of graph 210, and the angle of incidence of light on facet 42 is shown along the horizontal axis. The uprange and reflectance angle range of the angle of incidence selected to be the image wFOV is schematically represented by a shaded region 218. The downrange of the angle of incidence selected to be the transmittance angle range and conjugate wFOV is schematically represented by a shaded region 216. The dashed hat function 214 shows the “see-through” angle range of the facet of natural light 74 (Figure 1A) according to embodiments of the present disclosure.

[0031] Assuming that the display engine 70 includes a laser diode (LD) that provides R, G, and B light to be processed by the display engine to generate a virtual image, the facets 42 are designed such that the reflectivity of the facets is relatively constant as a function of the up-range and down-range wavelengths of the incident angle for each R, G, and B laser oscillation bandwidth in which the LD is expected to laser oscillate. Optionally, the dispersion of the facet's reflectivity with respect to wavelength in each R, G, and B facet wavelength band is less than 5%. In one embodiment, the dispersion is less than 2%.

[0032] LDs typically oscillate at wavelengths with a relatively narrow wavelength bandwidth between 1 and 2 nm (nanometers) FWHM (full width at half maximum). However, the LD laser oscillation bandwidth can shift by, for example, 0.1 to 0.35 nanometers for every change in degrees Celsius (°C) of the LD operating temperature, and the operating temperature can easily vary by 20°C. Furthermore, manufacturing tolerances can allow for a dispersion of as much as 5 nanometers in the central laser oscillation wavelength at which the same type of LD oscillates. According to one embodiment, facet 42 is advantageously configured to have facet wavelength bands for each of the R, G, and B light generated by the LD for incident angles of uprange and downrange of about 20 nanometers or more. Advantageously, for each facet wavelength band, the change in reflectance with respect to wavelength within the band is less than 3% of the average reflectance, providing a gamut chromaticity difference radius "ΔCG" in the CIE 1931xy chromaticity space of about 0.02 or less.

[0033] As an example, Figure 1F schematically shows the laser oscillation bandwidths 120R, 120G, and 120B of the R, G, and B laser oscillation bandwidths of the LD in the display engine 70, as well as the corresponding facet wavelength bands 121RW, 121GW, and 121BW of facet 42, according to one embodiment of the present disclosure. Figure 1G shows graph 230 of curve 232, which gives the reflectance of facet 42 as a function of wavelength for the blue wavelength range in the visible spectrum. In inset 234, a portion of curve 232 is magnified in inset 234 and marked to show a region of the curve centered on a blue wavelength of about 450 nanometers between about 445 nanometers and about 455 nanometers, graphing the reflectance as a function of wavelength in facet wavelength band 121BW. The reflectance of facet 42 for the wavelength in facet wavelength band 121BW is equal to about 4.8%, and the change with respect to wavelength in this wavelength band is less than about 5%.

[0034] The facets 42 having the see-through range at the incident angle, the up-range, and the down-range reflectance shown in FIG. 1E, and the R, G, B facet wavelength bands shown in FIG. 1F may comprise partially reflecting dielectric mirrors. The partially reflecting dielectric mirror may be manufactured by depositing a partially reflecting coating on the surfaces of pre-formed prisms and bonding the prisms to each other. The prisms may be manufactured by grinding and polishing a silicate material such as BK-7 into a desired shape, or by injection molding a suitable polymer or sol-gel. The coating may be formed from any of various suitable materials such as, for example, hafnium dioxide (HfO2), magnesium fluoride (MgF2) and / or tantalum pentoxide (Ta2O5).

[0035] FIG. 2A schematically illustrates another waveguide combiner 320 according to an embodiment of the present disclosure. Waveguide combiner 320 is similar to waveguide combiner 20, and has wFOV-U and wFOV-D selected for image wFOV and conjugate wFOV, respectively. However, waveguide combiner 320 comprises a waveguide 330 having facets 342 that are tilted at a tilt angle β greater than the tilt angle of facets 42 in waveguide combiner 20. Further, unlike waveguide combiner 20, waveguide combiner 320 is configured such that light rays of both wFOV-D and wFOV-U are incident on the same side of facet 242, that is, the side facing the TIR face surface 32.

[0036] To provide the same-side incidence illustrated by waveguide combiner 320, calculations similar to those performed to form waveguide combiner 20 result in the following constraints for waveguide combiner 320. For all γ, 14) β>90-γ⇒β>30°+α + / 3 15) γ=(2β-α - )<90°⇒β<(90°+α - ) / 2 16)(30°+α + / 3)<β<(45°+α - / 2) or (30°+Φ / 6)<β<(45°-Φ / 4) The angle up-range and down-range for the waveguide combiner 32 are as follows. 17) Up-range={∀φ u |(β-α + )≦φ u ≦(β-α - )} and 18) Down-range={∀φ d |(180°-3β+α - )≦φ d ≦(180°-3β+α + )} Here, φ u and φ d are incident angles of light waves in wFOV-U and wFOV-D, respectively.

[0037] As a numerical example for a waveguide 330 of Φ' having n equal to about 1.5 at a wavelength of about 550 nanometers g , absolute values |α + | and |α - | equal to about 13°, a diagonal range of about 30°, and an aspect ratio of 16:9, β may be equal to about 35°. The up-range of incident angles selected for the image wFOV, that is the reflectance angle range, advantageously extends from about 26° to about 44°, and is optionally characterized by an average reflectance between about 9% and 11%, optionally 10% or more. The down-range selected for the conjugated wFOV, that is the transmittance angle range, advantageously extends from about 66° to about 84°, and is characterized by an average reflectance of about 5% or less, optionally 2% or less. The see-through range advantageously extends from about 15° to about 55°, and is characterized by a transmittance of about 85% or more.

[0038] Figure 2B shows a graph 350 of the reflectance of facet 42 and facet 242, which may optionally be manufactured similarly, in substantial agreement with the numerical specifications described above. The graph includes a reflectance curve 312 that gives the reflectance of facet 242 in waveguide 330 as a function of the angle of incidence of light on the facet. Reflectance (percent) is shown along the vertical axis of graph 351, and the angle of incidence of light on facet 242 is shown along the horizontal axis. The uprange and reflectance angle range of the angle of incidence selected to be the image wFOV is schematically represented by shaded region 351. The transmittance angle range and the downrange of the angle of incidence selected to be the conjugate wFOV are schematically represented by shaded region 352. The dashed hat function 353 shows the “see-through” angle range of the facet of natural light 74 (Figure 1A) according to embodiments of the present disclosure.

[0039] Figure 3A schematically shows another waveguide combiner 420 according to an embodiment of the present disclosure. Waveguide combiner 420 is similar to waveguide combiner 320 shown in Figure 2A, but includes waveguide 430 having facet 442 that is tilted at a tilt angle β greater than the tilt angle of facet 342 in waveguide combiner 330. Furthermore, waveguide combiner 420 is configured, like waveguide combiner 320, so that rays in both wFOV-D and wFOV-U are incident on the same side of facet 342 (the side facing the face surface 32), but unlike waveguide combiner 320, in waveguide combiner 420 wFOV-D is the image wFOV and wFOV-U is the conjugate wFOV.

[0040] Regarding the waveguide combiner 420, 19)γ ± =180°-2β-α ± Alternatively, γ = 180° - 2β - α, and for combiner 420, γ - >γ + Therefore, please note that the following constraints must be met in order to provide a waveguide combiner 420 configuration in which wFOV-D, not wFOV-U, is the image wFOV. 20)(90°-γ - )>0⇒ 21) β>45°-α - / 2 and 22)γ +> θ c ⇒ 23)β<90°-(α + +θ c ) / 2 Combining equations 21 and 23, we obtain the following equation regarding the constraint on β. 24) 45°-α - / 2<β<90°-(α + +θ c ) / 2 The angular uprange, which is the transmittance range, and the downrange, which is the reflectance range of the waveguide combiner 420, may also be described as follows: 25) Uprange = {∀φ u |(180°-3β-α + )≦φ u ≤(180°-3β-α - )} and 26) Downrange = {∀φ d |(β+α - )≦φ d ≤(β+α + )}

[0041] Figure 3B provides a graph 450 showing the angular position and range of the uprange (transmittance range) 451, downrange (reflectance range) 452, and see-through range 453 for facet 442 within the waveguide combiner 430.

[0042] As a numerical example for waveguide 430, for a wavelength of 550 nanometers, n g This is approximately equal to 1.51, and the absolute value is |α|. + | and |α -Assuming | is equal to approximately 13° and Φ' has a diagonal range of approximately 30° and an aspect ratio of 16:9, β may be equal to 63.5°. The incident angle uprange, the transmittance angle range, favorably extends from approximately 2° to approximately 20°, favorably with a relatively low average reflectance of less than approximately 5%, and optionally less than approximately 2.0%. The reflection angle range and downrange selected for the image wFOV favorably extends from approximately 55° to approximately 75°, and optionally with a relatively high average reflectance of 10% or more, between approximately 9% and approximately 11%. The see-through range favorably extends from approximately 40° to approximately 80°, and is characterized by a transmittance of 85% or more.

[0043] Figure 3B shows a manufacturing method for facet 42 and a graph 450 of the reflectance of facet 342, which may optionally be manufactured similarly, in substantial agreement with the numerical specifications described above. The graph includes a reflectance curve 412 that gives the reflectance of facet 342 in waveguide 430 as a function of the angle of incidence of light to the facet. The reflectance (percent) is shown along the vertical axis of graph 351, and the angle of incidence of light to facet 342 is shown along the horizontal axis. The uprange and transmittance angle range of the angle of incidence selected to be the conjugate wFOV is schematically represented by shaded region 451. The reflection angle range and the downrange of the angle of incidence selected to be the image wFOV are schematically represented by shaded region 452. The dashed hat function 453 shows the see-through angle range of the facet with respect to natural light 74 (Figure 1A) according to embodiments of the present disclosure.

[0044] More generally, v u This represents the normalized vector in the propagation direction of upward rays contained in wFOV-U within waveguides 30, 330, or 430 of waveguide combiner 20, 320, or 420, but is not necessarily included in plane AA shown for the waveguide combiners in Figure 1B, Figure 2B, or Figure 3B, respectively. Next, the angle of incidence φ of upward rays on the facets of the waveguide with respect to the normal to the facets. u This may also be given by the following formula. 27)φ u =cos-1 (v u .n f ) Here, n f v is a vector perpendicular to the facet. Similarly, v d However, if the downward ray propagation direction included in wFOV-D is not necessarily included in plane AA, then the angle of incidence of the ray to the waveguide facet φ d It may also be written as follows: 28)φ d =cos -1 (v d .n f )=cos -1 ((v u -2V u .n w ).n f ) Here, n w This is a vector perpendicular to the TIR face plane of the waveguide.

[0045] The above constraints apply to one embodiment of the present disclosure, with reference to plane AA on a waveguide combiner, v u and / or v d It may be generalized as a function of . For example, for waveguide combiner 420, equations 24) and 25) may be rewritten as follows: 29) Uprange = {∀φ u |(-180°+3β+α - )≦cos -1 (v u .n f )≦(-180°+3β+α + )} and 30) Downrange = {∀φ u |(β+α - )≦cos -1 ((v u -2V u .n w ).n f )≦(β+α + )}

[0046] It should be noted that in the above description, each facet in the combiner waveguide according to one embodiment is designed to have reflectance and transmittance angular ranges for each of R, G, and B light. However, the practice of one embodiment of the present disclosure is not limited to facets having angular ranges for each of R, G, and B light. Facets according to one embodiment may be designed to function for colors other than R, G, and B, and may be configured to function for four or more or two or fewer colors. For example, each facet may be designed to function for only one or two of R, G, or B.

[0047] Furthermore, the interval between facets, referred to as the facet pitch "P", may be defined by the equation P = ηLcosβ, where L is the length of the facets between TIR face planes and η is a coefficient, typically less than 1, and may differ from, for example, those favorably shown in Figures 1B, 2A, or 3A. In Figures 1B and 2A, η is substantially equal to 1, and the pitch P is shown to be substantially equal to P = Lcosβ. In Figure 3A, η is substantially equal to 0.7, and P = 0.7Lcosβ. A smaller pitch P may be advantageous, according to one embodiment, for providing spatial consistency to the virtual image provided by the waveguide combiner.

[0048] As an example, the waveguide combiner described above expands the input opening 35 in one direction along the y-axis (for example, as shown in Figure 1A) according to the embodiments of the present disclosure. A waveguide combiner that expands the input opening along two directions, for example, the x-direction and the y-direction, according to one embodiment of the present disclosure, may be provided by replacing the input coupler 50 in the waveguide combiner shown in Figure 1A with a waveguide combiner that expands the input opening in the x-direction.

[0049] Figure 4 schematically shows a waveguide combiner 500 according to one embodiment of the present disclosure, in which the input aperture 535 is extended in two arbitrarily orthogonal directions to provide an extended output coupling region 536 in which the waveguide combiner guides light into the EMB 560.

[0050] In one embodiment of the present disclosure, the waveguide combiner 500 optionally comprises a prism input coupler 550, a first waveguide 530, and a second waveguide 630. The input coupler 550 receives light from a virtual image generated by a laser display engine 570 through an input aperture 535 and inputs the light into the waveguide 530. The waveguide 530 comprises a first TIR face surface 531 and a second TIR face surface 532, and top and bottom surfaces 532 and 534, respectively, which are optionally parallel to the xy plane of coordinate system 100. The waveguide has an output coupler 540 including a plurality of parallel facets 542 according to an embodiment of the present disclosure. Optionally, the facets are perpendicular to the face surfaces 531 and 532 and have an inclination angle β * It is rotated only about the z-axis. Optionally, the facets are evenly spaced. Rays in the light received from the input coupler 550 are repeatedly totally reflected between the TIR face surfaces 531 and 532, bouncing back and forth, and reaching and incident on facet 542 of the output coupler 540. Facet 542 is positioned over a distance relatively extended in the x-axis direction, reflecting rays from waveguide 530 in the general direction of the negative y-axis and causing them to enter waveguide 630 through an extended output aperture 545 that extends the input aperture 535 in the x-direction. Waveguide 630 may be any waveguide configured to receive light from an image generated by a display engine through an input aperture such as the input aperture 535 and project light received from the waveguide through an output coupling region such as an output coupling region 545 that is substantially extended in one direction.

[0051] Waveguide 630 is assumed, for example, to be similar to waveguide 30, and is parallel to the xy plane, and optionally comprises facets 42 and TIR facets 31 and 32 continuous with facets 531 and 532, respectively. Waveguide 630 extends the image in waveguide 530 545 in the negative y direction and reflects light received from waveguide 530 into EMB 560 through an output coupling region 536 extended in both the x and y directions. While waveguide 630 is assumed to be similar to waveguide 30 shown in Figure 1A, it should be noted that waveguide 630 may be similar to various waveguides, for example, waveguide 330 (Figure 2A) or waveguide 430 (Figure 3A), which include facets and are configured according to one embodiment of the present disclosure.

[0052] Equations 25) and 26) may be chained together to relate to desired constraints on the output field of view that the waveguide combiner 500 provides to the EMB 560. Upward and downward rays propagating in the waveguide 530 toward face planes 531 and 532 are given by vector v u (530) and v d If expressed by (530), it would be as follows: 31)v d (630) = (v u (630)-(2v u (630).n w )n w , Here, n w is the normal to the face planes 531, 532, 31, and 32 in the waveguide combiner 500, and the upward and downward rays are considered to be moving in the negative and positive z directions, respectively. One of the upward and downward groups of rays propagating in waveguide 530 is reflected into waveguide 630 by facet 542. For example, v u (530) Assume that the light ray is reflected into waveguide 630. Next, since the reflection by facet 542 does not change the component of the light ray propagation in the z direction, the v after reflection by facet 542 u(530) The rays enter the waveguide 630 as upward rays relative to the face surfaces 31 and 32. The upward rays after entering the waveguide 630 are v u (630) is used to represent this. Next, as a result of reflection to waveguide 630 by facet 542 in waveguide 530, when the light ray v is incident on waveguide 630, u (630) has a direction given by the following equation. 32)v u (630) = v u (530)-2(v u (530).n f (542)n f After reflection by the face surface 32, an upward v u (630) is a downward-pointing ray v d (630) and "naru". Here, 33)v d (630) = v u (630)-2(v u (630).n w )n w

[0053] Upward and downward rays within waveguide 630 are included in the upward field of view wFOV-U and downward field of view wFOV-D, respectively, as schematically shown in Figures 1A, 2A, and 3A. Furthermore, according to one embodiment, rays in one of wFOV-U and wFOV-D within waveguide 630 are selected for reflection into the EMB 560 by facet 42 through the output coupling region 536 within the output field of view O-FOV. Desired constraints on rays within O-FOV are the tilt angles β and β characterizing facets 42 and 542 within waveguides 30 and 530. * It may be propagated backward to match.

[0054] In the description and claims of this application, the verbs “include,” “include,” and “have,” and each of their conjugates, are used to indicate that one or more objects of a verb are not necessarily a complete list of components, elements, or parts of one or more subjects of a verb.

[0055] The descriptions of embodiments of the Disclosure in this Application are provided as examples and are not intended to limit the scope of the Disclosure. The embodiments described include different features, not all of which are required in all embodiments. Some embodiments utilize only some of the features or possible combinations of features. Variations of the embodiments of the Disclosure described, and of the embodiments including different combinations of features mentioned in the embodiments described, will be conceivable to those skilled in the art. The scope of the Invention is limited only by the claims.

Claims

1. Waveguide combiner, Normal vector "n" w A first waveguide including first and second parallel internal total reflection face surfaces having '', An input opening through which light passes and enters the first waveguide, In relation to the output coupling region, the input opening is expanded in at least one direction, and the output coupling configuration includes an output coupling configuration in which light entering the first waveguide passes through and exits the first waveguide, An output coupler configured for use with at least one laser, which is embedded in the first waveguide, n w and the normal vector "n" for the facet f An output coupler comprising a plurality of parallel facets having a facet tilt angle β between and , wherein the facets propagate along the first waveguide and reflect light incident on the facets outward through the output coupling region, and each of the facets is A laser oscillation band and a facet wavelength band of each laser oscillation band of light provided by at least one laser, including wavelengths of light in the range of wavelengths in which the laser oscillation band is expected to change, wherein the laser oscillation band includes a facet wavelength band that includes red, green, and blue laser oscillation bands, A reflectance angle range that exhibits a first reflectance for light having a wavelength in the facet wavelength band that propagates within the first waveguide and is incident on the facet at a first range of incident angles, A transmittance angle range that exhibits a second reflectance lower than the first reflectance for light having a wavelength in the facet wavelength band that propagates within the first waveguide and is incident on the facet at a second range of incident angles, The coating has a see-through angle transmittance range that has high transmittance with respect to natural light incident on the facet at a third range of incident angles, For each of the aforementioned facet wavelength bands, the reflectance of the wavelengths within that facet wavelength band changes by 3% or less relative to the average reflectance in that facet wavelength band, and as a result, the gamut chromaticity difference radius "ΔCG" in the CIE 1931xy chromaticity space becomes 0.02 or less. A waveguide combiner in which, when the average reflectance of a wavelength in the facet wavelength band is represented by R, and the maximum difference between the reflectance of a wavelength in the facet wavelength band and R is represented by ΔR, |ΔR| / R is 3% or less.

2. The waveguide combiner according to claim 1, wherein the facet wavelength band for the laser oscillation band has a bandwidth of three times or more the bandwidth of the laser oscillation band.

3. (90°-γ)>β, γ>θ C And, γ is n w This represents the angle between the direction of incidence of a ray of light propagating within the first waveguide and the direction of incidence of the ray of light that the output coupler reflects outward from the first waveguide through the output coupling region to the face surface. Here, θ C The waveguide combiner according to claim 1, wherein is the critical angle of the first waveguide for light having wavelengths within the facet wavelength band.

4. The facet inclination angle β satisfies the constraint (θ c +α + ) / 2 < β < (30°+α - / 3), Here, α + and α - Each of these is an angle in a plane perpendicular to the face plane and the facet, where the normal to the face plane makes an angle with respect to the direction in which the facet reflects incident light outward from the first waveguide. Here, α + is, α - It is greater than and is positive when rotated clockwise with respect to the normal, and negative when rotated counterclockwise. α + and α - The waveguide combiner according to claim 3, wherein the minimum and maximum values ​​of γ+ and γ- that define the field of view wFOV of light propagating in the first waveguide are determined, respectively.

5. The aforementioned reflectance angle range is (β-α + )≦φ≦(β-α - A waveguide combiner according to claim 4, which spans the range of the incident angle φ of ).

6. The aforementioned transmittance angle range is (3β-α + )≦φ≦(3β-α - A waveguide combiner according to claim 4, which spans the range of the incident angle φ of ).

7. A waveguide combiner according to claim 1, wherein β > (90° - γ).

8. The facet tilt angle β is constrained by (30° + α + / 3)<β<(45°+α - A waveguide combiner according to claim 1, satisfying (2) / .

9. The aforementioned reflectance angle range is (β-α + )≦φ≦(β-α - A waveguide combiner according to claim 8, which spans the range of the incident angle φ of ).

10. The transmittance angle range is (180°-3β+α-)≦φ≦(180°-3β+α + A waveguide combiner according to claim 8, which spans the range of the incident angle φ of ).

11. The facet tilt angle β is constrained by 45°-α - / 2<β<90°−(α + +θ c A waveguide combiner according to claim 7, satisfying ) / 2.

12. The aforementioned reflectance angle range is (β + α - ). ≦ φ ≦ The waveguide according to claim 11, extending over the range of an incident angle φ of (β + α +).

13. The aforementioned transmittance angle range is (180° - 3β - α + )≦φ u ≦(180°−3β−α - A waveguide combiner according to claim 11, which extends over a range of incidence angles φ.

14. A waveguide combiner according to claim 1, comprising: a second waveguide having a second input aperture; and a second output coupling region through which light received through the second input aperture exits the second waveguide and enters the first waveguide, wherein the second output coupling region is expanded relative to the second input aperture in a direction different from at least one direction in which the output aperture of the first waveguide is expanded.

15. Waveguide combiner, Normal vector "n" w A first waveguide including first and second parallel internal total reflection face surfaces having '', An input opening through which light passes and enters the first waveguide, In relation to the output coupling region, the input opening is expanded in at least one direction, and the output coupling configuration includes an output coupling configuration in which light entering the first waveguide passes through and exits the first waveguide, An output coupler configured for use with at least one laser, which is embedded in the first waveguide, n w and the normal vector "n" for the facet f An output coupler comprising a plurality of parallel facets having a facet tilt angle β between and , wherein the facets propagate along the first waveguide and reflect light incident on the facets outward through the output coupling region, and the facets are A laser oscillation band and a facet wavelength band of the laser oscillation band of light provided by at least one laser, which includes the laser oscillation band and the wavelengths of light in the range of wavelengths in which the laser oscillation band is expected to change, A reflectance angle range that exhibits a first reflectance for light having a wavelength in the facet wavelength band that propagates within the first waveguide and is incident on the facet at a first range of incident angles, A transmittance angle range that exhibits a second reflectance lower than the first reflectance for light having a wavelength in the facet wavelength band that propagates within the first waveguide and is incident on the facet at a second range of incident angles, It has a see-through angle transmittance range that has high transmittance for natural light incident on the facet at a third range of incident angles, (90°-γ)>β, γ>θ c And, γ is n w This represents the angle between the direction of incidence of a ray of light propagating within the first waveguide and the direction of incidence of the ray of light that the output coupler reflects outward from the first waveguide through the output coupling region to the face surface. Here, θ c This represents the critical angle of the first waveguide for light having wavelengths within the facet wavelength band, The aforementioned facet tilt angle β is constrained by (θ) c +α + ) / 2<β<(30°+α - / 3) satisfies, Here, α + and α - Each of these is an angle in a plane perpendicular to the face plane and the facet, where the normal to the face plane makes an angle with respect to the direction in which the facet reflects incident light outward from the first waveguide. Here, α + is, α - It is greater than and is positive when rotated clockwise with respect to the normal, and negative when rotated counterclockwise. α + and α - However, the minimum and maximum values ​​of γ that define the field of view wFOV of light propagating within the first waveguide are determined, The aforementioned reflectance angle range is (β-α + )≦φ ≦ Over the range of the incident angle φ of (β-α-), The aforementioned transmittance angle range is (3β-α + )≦φ≦(3β-α - A waveguide combiner that operates over a range of incidence angles φ.

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