Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B6/13—Integrated optical circuits characterised by the manufacturing method
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
  • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
  • G02B6/0065—Manufacturing aspects; Material aspects
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
  • G02B26/0875—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more refracting elements
  • G02B26/0883—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more refracting elements the refracting element being a prism
  • G02B26/0891—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more refracting elements the refracting element being a prism forming an optical wedge
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/01—Head-up displays
  • G02B27/017—Head mounted
  • G02B27/0172—Head mounted characterised by optical features
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
  • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
  • G02B6/0033—Means for improving the coupling-out of light from the light guide
  • G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
  • G02B6/0045—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it by shaping at least a portion of the light guide
  • G02B6/0046—Tapered light guide, e.g. wedge-shaped light guide
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B6/122—Basic optical elements, e.g. light-guiding paths
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B6/122—Basic optical elements, e.g. light-guiding paths
  • G02B6/1221—Basic optical elements, e.g. light-guiding paths made from organic materials
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B2006/12035—Materials
  • G02B2006/12038—Glass (SiO2 based materials)
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B2006/12035—Materials
  • G02B2006/12061—Silicon
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B2006/12035—Materials
  • G02B2006/12069—Organic material
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B2006/12166—Manufacturing methods
  • G02B2006/12197—Grinding; Polishing
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/01—Head-up displays
  • G02B27/017—Head mounted
  • G02B2027/0178—Eyeglass type

Definitions

• This invention relates to biased total thickness variations in waveguide display substrates.
• Optical imaging systems typically include one or more eyepieces that present projected images to a user.
• Eyepieces can be constructed using thin layers of one or more refractive materials.
• eyepieces can be constructed from one or more layers of highly refractive glass, silicon, metal, or polymer substrates.
• an eyepiece layer can be patterned (e.g., with one or more light diffractive nanostructures) such that it displays received light incoupled from an external projector.
• multiple eyepieces layers can be used in conjunction to project a simulated three-dimensional image.
• multiple waveguides— each having a specific pattern— can be layered, and each waveguide can relay specific light information of a portion of a volumetric image (e.g., wavelength or focal distance) such that in the aggregate of specific light information from each of the waveguides, the entire coherent volumetric image is viewable.
• the eyepieces can collectively present the full color volumetric image to the user across three-dimensions. This can be useful, for example, in presenting the user with a“virtual reality” environment.
• Unintended variations in an eyepiece can reduce the quality of a projected image. Examples of such unintended variations include wrinkles, uneven thicknesses, and other physical distortions that can negatively affect the performance of the eyepiece.
• a first general aspect includes a plurality of waveguide display substrates, each waveguide display substrate having a cylindrical portion having a diameter and a planar surface, a curved portion opposite the planar surface defining a nonlinear change in thickness across the substrate and having a maximum height D with respect to the cylindrical portion, and a wedge portion between the cylindrical portion and the curved portion defining a linear change in thickness across the substrate and having a maximum height W with respect to the cylindrical portion.
• a target maximum height Dt of the curved portion is 10 7 to 10 6 times the diameter, D is between about 70% and about 130% of Dt, and W is less than about 30% of Dt.
• an average of D is Dmean
• a maximum D for the plurality of waveguide display substrates is Dmax
• a minimum D for the plurality of waveguide display substrates is Dmin
• a maximum W for the plurality of waveguide display substrates is Wmax.
• a second general aspect includes fabricating the plurality of waveguide display substrates of the first general aspect.
• Implementations of the first and second general aspects may include one or more of the following features.
• the nonlinear change in thickness is a quadratic change in thickness.
• the curved portion may be in the form of a dome. In some cases, the dome is spherical.
• An average thickness of the plurality of waveguide display substrates is typically between about 200 microns and about 2000 microns.
• An average diameter of the plurality of waveguide display substrates is typically between about 2 centimeters and about 50 centimeters.
• Wmax/Dmean is typically less than about 0.3.
• (Dmean - Dmin)/Dmean is typically less than about 0.3.
• (Dmax - Dmin)/Dmean is typically less than about 0.3.
• D is typically in a range of about 0.1 microns to about 5 microns.
• W is typically in a range of 0 to about 1.5 microns.
• An average total thickness variation of the plurality of substrates is typically between about 0.1 microns and about 6.5 microns.
• the waveguide display substrates comprise a molded polymer. In certain implementations, the waveguide display substrates comprise a polished glass, silicon, or metal substrate.
• Implementations of the second general aspect may include one or more of the following features.
• fabricating the plurality of waveguide display substrates may include polishing the waveguide display substrates, where the waveguide display substrates are formed of glass, metal, or silicon.
• fabricating the plurality of waveguide display substrates includes molding polymeric waveguide display substrates.
• the second general aspect may further include forming one or more waveguides on each of the waveguide display substrates.
• the one or more waveguides may include at least two waveguides, and the waveguides may be positioned in a radial pattern on each waveguide display substrate.
• FIG 1 depicts a sample waveguide display substrate with waveguide areas.
• FIGS. 2A-2C depict polished waveguide display substrates having flat, convex, and concave cross-sectional shapes, respectively.
• FIGS. 3A and 3B depict total thickness variation (TTV) comparisons of waveguide display substrates.
• FIG. 4 depicts TTV of a polished waveguide display substrate with a convex surface.
• FIG. 5 shows a cross section of a waveguide display substrate with a biased TTV having linear (wedge) and nonlinear (dome) components.
• FIGS. 6A-6C show waveguide display substrate yield versus TTV, dome height, and wedge height for ultra-low TTV waveguide display substrates.
• FIGS. 6D-6F show waveguide display substrate yield versus TTV, dome height, and wedge height for biased TTV waveguide display substrates.
• FIG. 7 shows waveguide eyebox efficiency versus“dome” height TTV (nm) of a spherical waveguide display substrate on a 6 inch waveguide display substrate for a typical diffractive waveguide display with 300 pm average thickness and 0 nm“wedge” TTV.
• Total thickness variation is one metric for improving performance of an optical waveguide.
• TTV generally refers to the difference between the maximum and minimum values of the thickness of the waveguide or the waveguide display substrate on which the waveguide is formed.
• variations in the thickness alter the light propagation path(s). Angular differences in the light propagation path(s) can affect image quality with field distortions, image blurring, and sharpness loss.
• Waveguide preparation and processing typically occurs by arranging a number of waveguides to designated areas onto a waveguide display substrate (e.g., a wafer).
• FIG. 1 depicts waveguide display substrate 100 with a radial arrangement of waveguides 102.
• TTV can be reduced by fabricating a flat waveguide display substrate (i.e., a waveguide display substrate with zero TTV), for example, by polishing the substrate (e.g., a metal, glass or silicon substrate) or originally molding the substrate (e.g., a polymer substrate) with high- precision. However, polishing can produce a certain amount of curvature upon the waveguide display substrate and the resultant waveguides formed thereon.
• FIG. 2A depicts polished flat waveguide display substrate 200.
• FIG. 2B and 2C depict polished convex waveguide display substrate 202 and polished concave waveguide display substrate 204, respectively. Though polishing can yield convex or concave curvatures, embodiments described herein are explained with reference to a convex curvature, such as that depicted in FIG. 2B.
• TTV ⁇ 2 pm there exists a thickness shape or profile to the substrates that varies (e.g., randomly) from part to part.
• “thickness shape” generally refers to the 3D mapping of the height difference between the substrate’s top and bottom surfaces.
• a typical plano-convex lens has a thickness shape that is a convex spherical or positive“dome”.
• a meniscus lens with the same radius of curvature on each surface e.g., non-prescription sunglasses
• waveguide display substrate 300 is shown having a TTV, measured as the highest point to the lowest point of the curved portion of the polished waveguide display substrate.
• Perfectly flat waveguide display substrate 302, depicted in FIG. 3B has a zero TTV.
• FIG. 4 depicts waveguide display substrate 400 having a minimum thickness X.
• TTV thickness in addition to X.
• the greatest thickness is h
• TTV specifications are typically expressed as a maximum allowed TTV (TTVmax), and product specifications target a TTV (Y) below TTVmax (i.e., 0 ⁇ Y ⁇ TTVmax).
• TTVmax maximum allowed TTV
• Y product specifications target a TTV (Y) below TTVmax (i.e., 0 ⁇ Y ⁇ TTVmax).
• “ultra-low TTV” waveguide display substrates refers to waveguide display substrates for which the target TTV is zero (or as close to zero as practically possible).
• image quality and uniformity can be sensitive to a particular shape or profile of a polished waveguide display substrate as TTV approaches zero.
• the comparative difference of image quality (as measured by uniformity) of waveguides produced on a 20 nm TTV and a 40 nm TTV waveguide display substrate can be much higher than the comparative quality of waveguides produced on a 100 nm TTV substrate and a 120 nm waveguide display substrate, despite both pairs being only 20 nm different.
• a 100 nm TTV waveguide and a 120 nm waveguide can yield a more similarly uniform image than a 20 nm TTV waveguide and a 40 nm TTV waveguide (the former pair being more dome shaped as compared to the latter pair).
• the 100 nm TTV waveguide and 120 nm TTV waveguide can thus produce lower image variation and more consistent image uniformity across a product line.
• Path length differences in the light propagation path(s) within a waveguide produced on a non-flat waveguide display substrate can also affect image quality with luminance pattern non-uniformities and color non-uniformities.
• the source of the luminance pattern non-uniformities includes electromagnetic interference patterns produced by numerous pathways through a pupil-replicating waveguide display substrate.
• a unit-cell of a typical pupil-replicating waveguide resembles a Mach-Zender interferometer, where there exist two pathways per unit-cell from the input to an output replicated pupil location.
• Pathlength differences between the two pathways are influenced by the pathlength through the thickness of the waveguide display substrate, which is defined by the TTV metric and thickness profile (whether the thickness changes linearly or quadratically and at an angle with respect to the light in total-intemal-reflection within the waveguide display). If the pathlengths have equal or opposite phase, there may be constructive or destructive interference, respectively. Hence, the thickness shape may affect the magnitude within pupil- replicated copies and ultimately the output image outcoupled by the waveguide display.
• n and n are nonnegative integers with n > m. is the azimuthal angle
• p is the radial distance
• R m n are the radial polynomials defined below.
• Zemike polynomials have the property of being limited to a range of -1 to +1, i.e. .
• the radial polynomials R m n are defined as
• Image quality in particular luminance uniformity, is nonlinearly sensitive to thickness shape as TTV approaches zero.
• TTV decreases below certain thresholds, image quality becomes increasingly varied among waveguides exhibiting even minor changes in thickness shape.
• a biased TTV with a consistent thickness shape can be incorporated into substrate processing.
• a “biased” TTV generally refers to a TTV having a nonzero target. More specifically, a “biased” TTV generally refers to a substrate thickness shape having one or more coefficients of Zemike fit polynomials with nonzero targets and all remaining coefficients of Zemike fit polynomials having zero targets.
• Consistency of thickness shape within a plurality of waveguide display substrates generally refers to a plurality of waveguide display substrates having a low variation of coefficients of Zemike fit polynomials.
• consistency of thickness shape refers to a set of waveguide display substrates having (i) all nonzero-targeted Zemike coefficients having minimal variation from their target magnitudes, for example the nonzero-targeted coefficients of all waveguide display substrates being about 70% to about 130% of their target magnitude, and (ii) all zero-targeted Zemike coefficients having an absolute magnitude substantially less than the nonzero-targeted Zemike coefficients, for example the zero-targeted coefficients being 0 to about 30% of the nonzero-targeted coefficients.
• An example of biased TTV and consistent substrate thickness shape is a substrate that is substantially polished (or molded) to a spherical shape with a TTV many times larger than the typical minimum TTV range of a substrate polishing (or molding) process.
• This substrate shape can be described as having wedge (linear change in thickness) and dome (quadratic change in thickness) components.
• FIG. 5 depicts waveguide display substrate 500 with wedge component 502 having height W, dome component 504 having height D, and cylindrical component 506 with planar surface 508 and having a thickness t and a diameter d.
• an average thickness of the waveguide display substrate is Zo°
• the height of the“wedge” component of TTV can be defined as sqrt(Zr' + Zi 1 )
• the height of the convex“dome” component of TTV can be defined as -2 c Z2 0
• An average thickness of the waveguide display substrate is typically between 200 pm and 2000 pm.
• the waveguide display substrates may have a target“dome” height Dt in the range of 10 7 to 10 6 of the substrate diameter, and each substrate may have a“dome” height less than 30% of the target “dome” height and a“wedge” height less than 30% of the target“dome” height.
• a plurality of waveguide display substrates having a diameter of 150 mm, a mean “dome” (Dmean) height of 1000 nm, a range of“dome” height (Dmin to Dmax) of 700 nm to 1300 nm, and a maximum“wedge” height (Wmax) of less than 300 nm will have increased efficiency, luminance uniformity and color uniformity and a reduced part-to-part variation in efficiency, luminance uniformity, and color uniformity compared to a plurality of waveguide display substrates having close-to-zero targeted TTV with“dome” and“wedge” height in the range of 0 to 300 nm.
• the biased TTV with consistent shape can be applied to the waveguide display substrate in numerous methods. For glass or crystalline substrates, it may be applied by polishing to a biased shape or by applying a coating with non-uniform thickness (of consistent shape and magnitude) to an ultra-low TTV waveguide display substrate with small but random thickness shape variation.
• the biased thickness profile can be designed into the mold that produces the waveguide display substrate.
• FIGS. 6A-6C show waveguide display substrate yield versus TTV, dome height, and wedge height for ultra-low TTV waveguide display substrates.
• the magnitude of dome height and wedge height are typically similar to each other.
• the range of variation of dome height is similar in magnitude to the mean of the dome height.
• FIGS. 6D-6F show waveguide display substrate yield versus TTV, dome height, and wedge height for biased TTV waveguide display substrates. In these biased TTV waveguide display substrates, the magnitude of the dome height is larger than the magnitude of the wedge height, and the variation of the dome height is smaller than the mean dome height.
• FIGS. 6D-6F represent depict a biased relationship without reference to specific values.
• a specification for a biased TTV tolerance can be expressed as:
• FIGS. 6A-6C show a set of waveguide display substrates that result in higher values of X, Y, and Z than the set of waveguide display substrates shown in FIGS. 6D-6F.
• X, Y, and Z approach zero, as opposed to having TTV itself approach zero, overall efficiency of a plurality of waveguides produced on numerous subsections of numerous waveguide display substrates both increases and has fewer variations.
• luminance uniformity and color uniformity among the resultant waveguides also increases and has fewer variations.
• Ultra-low TTV waveguide display substrates typically have X, Y and Z in the range of 1-10, and biased TTV waveguide display substrates have X, Y and Z in the range of 0 to 0.3, so a biased (or nonzero target) TTV can contribute toward improved waveguide display image quality.
• FIG. 7 shows waveguide eyebox efficiency versus“dome” TTV (nm) of a spherical waveguide display substrate shape on a 6 inch wafer for a typical diffractive waveguide display with 300 pm average thickness and 0 nm“wedge” TTV.
• eyebox efficiency is a maximum between a TTV of 400 nm and a TTV of 600 nm.
• Waveguide eyebox efficiency here refers to the sum of light entering a 15 x 20 mm 2 rectangular area 15 mm 2 away from the eye-side of a diffractive waveguide display’s output grating relative to the sum of light incident on the waveguide display’s input coupling grating as calculated by a typical diffractive waveguide simulation.

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• Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
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