Waveguide display: Difference between revisions
Xinreality (talk | contribs) Created page with "{{Infobox technology | name = Waveguide Display | image = | caption = | type = Optical display technology | inventor = Multiple (Lumus, Nokia, others) | inception = Early 2000s | manufacturer = Microsoft, Magic Leap, Lumus, DigiLens, Dispelix, WaveOptics, Vuzix | available = Commercial (enterprise), Limited (consumer) | field_of_view = 30-70° (current), 90°+ (projected 2030) | efficiency = 1-5% (current), 10% (target) | thickness = 0.5-2mm | weight = 2.7-15g | re..." |
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* '''Out-coupler''': Gradually extracts light from the waveguide toward the user's eye while expanding the exit pupil | * '''Out-coupler''': Gradually extracts light from the waveguide toward the user's eye while expanding the exit pupil | ||
Total internal reflection occurs when light traveling in an optically denser medium (refractive index n₁) strikes the interface with a less dense medium (n₂) at an angle exceeding the critical angle θ<sub>c</sub> = sin⁻¹(n₂/n₁).<ref name="coherent">Coherent. "High Index Waveguides for AR." https://www.coherent.com/news/blog/ar-displays-high-index-material</ref> For typical glass-to-air interfaces with n=1.5, this critical angle is approximately 42°. Higher refractive index materials enable wider fields of view by allowing a broader range of propagation angles. | Total internal reflection occurs when light traveling in an optically denser medium (refractive index n₁) strikes the interface with a less dense medium (n₂) at an angle exceeding the critical angle θ<sub>c</sub> = sin⁻¹(n₂/n₁).<ref name="coherent">Coherent. "High Index Waveguides for AR." https://www.coherent.com/news/blog/ar-displays-high-index-material</ref> For typical glass-to-air interfaces with n=1.5, this critical angle is approximately 42°. Higher refractive index materials enable wider fields of view by allowing a broader range of propagation angles.<ref name="schott">SCHOTT. "Waveguides for augmented reality." https://www.schott.com/en-gb/expertise/applications/waveguides-for-augmented-reality</ref> | ||
=== Exit Pupil Expansion === | === Exit Pupil Expansion === | ||
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! Technology !! Working Principle !! Key Advantages !! Key Disadvantages !! Efficiency !! Max FOV !! Key Proponents | ! Technology !! Working Principle !! Key Advantages !! Key Disadvantages !! Efficiency !! Max FOV !! Key Proponents | ||
|- | |- | ||
! Geometric (Reflective) | ! [[Geometric]] (Reflective) | ||
| Arrays of embedded partially reflective mirrors guide and extract light | | Arrays of embedded partially reflective mirrors guide and extract light | ||
| • Excellent color uniformity<br>• Minimal rainbow artifacts<br>• High brightness<br>• Achromatic operation | | • Excellent color uniformity<br>• Minimal rainbow artifacts<br>• High brightness<br>• Achromatic operation | ||
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| [[Lumus]], [[Google Glass]] | | [[Lumus]], [[Google Glass]] | ||
|- | |- | ||
! Diffractive (SRG) | ! [[Diffractive]] (SRG) | ||
| Surface relief gratings with 300-500nm periods diffract light | | Surface relief gratings with 300-500nm periods diffract light | ||
| • Scalable manufacturing<br>• Thin form factor<br>• Established supply chain<br>• Low cost potential | | • Scalable manufacturing<br>• Thin form factor<br>• Established supply chain<br>• Low cost potential | ||
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| [[Microsoft HoloLens]], [[Magic Leap]], [[Vuzix]] | | [[Microsoft HoloLens]], [[Magic Leap]], [[Vuzix]] | ||
|- | |- | ||
! Holographic (VHG) | ! [[Holographic]] (VHG) | ||
| Volume holograms recorded in photopolymers | | Volume holograms recorded in photopolymers | ||
| • High angular selectivity<br>• Good transparency<br>• Curved substrate compatible<br>• Roll-to-roll capable | | • High angular selectivity<br>• Good transparency<br>• Curved substrate compatible<br>• Roll-to-roll capable | ||
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| [[DigiLens]], [[Sony]] | | [[DigiLens]], [[Sony]] | ||
|- | |- | ||
! Polarization (PVG) | ! [[Polarization]] (PVG) | ||
| [[Liquid crystal]] structures with helical rotation | | [[Liquid crystal]] structures with helical rotation | ||
| • High diffraction efficiency<br>• Wide bandwidth<br>• Electrically switchable<br>• Simple fabrication | | • High diffraction efficiency<br>• Wide bandwidth<br>• Electrically switchable<br>• Simple fabrication | ||
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| Research stage | | Research stage | ||
|- | |- | ||
! Metasurface | ! [[Metasurface]] | ||
| Subwavelength nanostructures manipulate light | | Subwavelength nanostructures manipulate light | ||
| • Achromatic potential<br>• Ultra-thin<br>• Multifunctional<br>• Aberration correction | | • Achromatic potential<br>• Ultra-thin<br>• Multifunctional<br>• Aberration correction | ||
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=== Diffractive Waveguides === | === Diffractive Waveguides === | ||
'''Diffractive waveguides''' employ periodic nanostructures to manipulate light through [[diffraction]]. These dominate commercial products due to their manufacturing scalability.<ref name="optofidelity">OptoFidelity. "Comparing and contrasting different waveguide technologies." https://www.optofidelity.com/insights/blogs/comparing-and-contrasting-different-waveguide-technologies-diffractive-reflective-and-holographic-waveguides</ref> | '''[[Diffractive waveguides]]''' employ periodic nanostructures to manipulate light through [[diffraction]]. These dominate commercial products due to their manufacturing scalability.<ref name="optofidelity">OptoFidelity. "Comparing and contrasting different waveguide technologies." https://www.optofidelity.com/insights/blogs/comparing-and-contrasting-different-waveguide-technologies-diffractive-reflective-and-holographic-waveguides</ref> | ||
==== Surface Relief Gratings (SRG) ==== | ==== Surface Relief Gratings (SRG) ==== | ||
Surface relief gratings feature nano-ridges etched or embossed 100-300nm deep into the waveguide surface. Common profiles include: | [[Surface relief gratings]] feature nano-ridges etched or embossed 100-300nm deep into the waveguide surface. Common profiles include: | ||
* '''Binary gratings''': Rectangular grooves with vertical walls | * '''Binary gratings''': Rectangular grooves with vertical walls | ||
* '''Slanted binary gratings''': Inclined walls (slant angle β) to suppress unwanted diffraction orders | * '''Slanted binary gratings''': Inclined walls (slant angle β) to suppress unwanted diffraction orders | ||
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==== Volume Holographic Gratings (VHG) ==== | ==== Volume Holographic Gratings (VHG) ==== | ||
Volume holographic gratings record diffraction patterns as refractive index modulations (Δn ≈ 0.03-0.1) within 5-50μm thick [[photopolymer]] layers.<ref name="pmc2020">Liu, S. et al. "Analysis of the Imaging Characteristics of Holographic Waveguides Recorded in Photopolymers." Polymers 12(8), 1666 (2020). https://pmc.ncbi.nlm.nih.gov/articles/PMC7408443/</ref> These gratings operate according to [[Bragg diffraction]], providing high wavelength and angular selectivity. | [[Volume holographic gratings]] record diffraction patterns as refractive index modulations (Δn ≈ 0.03-0.1) within 5-50μm thick [[photopolymer]] layers.<ref name="pmc2020">Liu, S. et al. "Analysis of the Imaging Characteristics of Holographic Waveguides Recorded in Photopolymers." Polymers 12(8), 1666 (2020). https://pmc.ncbi.nlm.nih.gov/articles/PMC7408443/</ref> These gratings operate according to [[Bragg diffraction]], providing high wavelength and angular selectivity. | ||
==== Polarization Volume Gratings (PVG) ==== | ==== Polarization Volume Gratings (PVG) ==== | ||
PVGs utilize [[cholesteric liquid crystal]] structures with spatially varying director orientations. Key parameters include: | [[PVGs]] utilize [[cholesteric liquid crystal]] structures with spatially varying director orientations. Key parameters include: | ||
* Pitch: 200-700nm for visible wavelengths | * Pitch: 200-700nm for visible wavelengths | ||
* Thickness: 1-10μm | * Thickness: 1-10μm | ||
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=== Geometric Waveguides === | === Geometric Waveguides === | ||
'''Geometric waveguides''' (also called reflective waveguides) employ cascaded partially reflective mirrors embedded within the substrate. [[Lumus]] pioneered this Light-guide Optical Element (LOE) architecture, achieving 5% system | '''[[Geometric waveguides]]''' (also called reflective waveguides) employ cascaded partially reflective mirrors embedded within the substrate. [[Lumus]] pioneered this Light-guide Optical Element (LOE) architecture, achieving 5% system efficiency, significantly higher than diffractive approaches.<ref name="lumus">Wikipedia. "Lumus." https://en.wikipedia.org/wiki/Lumus</ref> | ||
The manufacturing process involves: | The manufacturing process involves: | ||
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3. Slicing the bonded stack at precise angles (tolerance <10 arcseconds) | 3. Slicing the bonded stack at precise angles (tolerance <10 arcseconds) | ||
4. Polishing to optical quality (surface roughness <1nm RMS) | 4. Polishing to optical quality (surface roughness <1nm RMS) | ||
Lumus announced their next-generation Z-Lens 2D architecture at CES 2023, promising improved field of view and efficiency.<ref name="prnewswire">PR Newswire. "Lumus Launches Next Generation 2D 'Z-Lens' Waveguide Architecture." https://www.prnewswire.com/news-releases/lumus-launches-z-lens-301713879.html</ref> | |||
=== Holographic Waveguides === | === Holographic Waveguides === | ||
'''Holographic waveguides''' record optical elements as three-dimensional interference patterns within volume materials. [[DigiLens]] developed Holographic Polymer-Dispersed Liquid Crystal (HPDLC) technology, enabling switchable gratings through electrical control of LC droplet orientation.<ref name="digilens">DigiLens. "Technology Overview." https://www.digilens.com/technology</ref> | '''[[Holographic waveguides]]''' record optical elements as three-dimensional interference patterns within volume materials. [[DigiLens]] developed Holographic Polymer-Dispersed Liquid Crystal (HPDLC) technology, enabling switchable gratings through electrical control of LC droplet orientation.<ref name="digilens">DigiLens. "Technology Overview." https://www.digilens.com/technology</ref> | ||
== Manufacturing == | == Manufacturing == | ||
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* [[Apple Inc.|Apple]] acquired [[Akonia Holographics]] (2018) | * [[Apple Inc.|Apple]] acquired [[Akonia Holographics]] (2018) | ||
* [[Google]] acquired [[North Inc.]] and its waveguide technology (2020) | * [[Google]] acquired [[North Inc.]] and its waveguide technology (2020) | ||
* [[Vuzix]] announced large-format waveguide manufacturing capabilities (2024)<ref name="vuzix2">Vuzix. "Large Format Waveguide Manufacturing." https://www.vuzix.com/blogs/press-releases/large-format-waveguide</ref> | |||
== Historical Development == | == Historical Development == | ||
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== References == | == References == | ||
{{reflist}} | |||
[[Category:Terms]] | |||
[[Category:Display technology]] | [[Category:Display technology]] | ||
[[Category:Optical devices]] | [[Category:Optical devices]] | ||