Edward Tang | Avegant: How do reflections within diffractive waveguides compromise the visual integrity of microLED-based AR displays?
04:08 - 06:27
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How do reflections within diffractive waveguides compromise the visual integrity of microLED-based AR displays?
Diffractive waveguides, a common choice for AR systems, inherently suffer from back reflection at the input coupler, which can return up to 20% of the projected light back towards the display engine. When combined with the significant reflectivity of microLED panels, which can range from 30% to 60%, this interaction generates undesirable ghost images. These multiple reflections within the system severely degrade the visual quality and user experience by introducing spurious artifacts into the augmented reality overlay.
To mitigate ghosting in microLED systems, a prevalent solution involves mechanically tilting the entire display engine, often by an angle equivalent to half the field of view. While this reduces reflections, it necessitates a larger physical volume within the glasses frame, impacting industrial design and overall form factor. In contrast, advanced LCO systems employ non-telecentric optical designs that effectively trap reflected light within the system, preventing ghosting without sacrificing efficiency or imposing mechanical constraints on engine placement, thus offering greater design flexibility.
* In this short video, you can learn:
* The primary causes of ghosting in microLED AR systems using diffractive waveguides.
* The role of waveguide back reflection and panel reflectivity in generating ghost images.
* Common mitigation techniques for ghosting, such as engine tilting, and their volumetric implications.
* How LCO non-telecentric systems offer an alternative solution for ghosting control.
#DiffractiveWaveguides, #MicroLEDReflectivity, #GhostImageMitigation, #NonTelecentricOptics, #AugmentedReality, #MicroLEDDisplays
This is a highlight of the presentation:
AR’s Display Dilemma - LCoS v MicroLED
More Highlights from the same talk.
02:18 - 04:08
Does the advertised "micro" size of microLED engines truly reflect their integrated volume in AR glasses?
Does the advertised "micro" size of microLED engines truly reflect their integrated volume in AR glasses?
Initial claims for full-color microLED engines often cite optical volumes as small as 0.2 to 0.4 cubic centimeters. However, this figure typically represents only the core optical components, excluding critical elements necessary for functional integration into an AR product. When considering the complete system, additional components such as memory chips for DMU correction, multiple connectors for multi-panel solutions, and robust thermal mitigation systems (like heat sinks) significantly expand the overall footprint.
Furthermore, microLED panels can exhibit considerable reflectivity, leading to ghosting issues when coupled with diffractive waveguides. To counteract this, engineers often resort to angling the entire engine or cutting light from the pupil, both of which further increase the effective volume and compromise optical performance. A real-world example of a "0.4 cc" engine from a shipping product revealed an integrated volume exceeding 2.3 cubic centimeters, demonstrating a substantial discrepancy between theoretical and practical size.
* In this short video, you can learn:
* Why advertised microLED engine sizes are often misleading.
* The impact of essential support components on integrated volume.
* How thermal management and ghosting mitigation strategies affect the final product size.
* A practical example of microLED engine volume expansion.
#MicroLEDEngineVolume, #ARSystemIntegration, #ThermalMitigation, #GhostingMitigation, #MicroLED, #AugmentedReality
07:16 - 08:15
Is your AR display's inherent Atondue limiting its effective light output when coupled with a waveguide?
Is your AR display's inherent Atondue limiting its effective light output when coupled with a waveguide?
Atondue, a fundamental optical invariant, is defined as the product of a display's emission angle and its emission area. This value is fixed for any given light source and cannot be reduced. In the context of AR systems utilizing waveguides, particularly diffractive waveguides, the input coupler introduces a critical limitation: it acts as an aperture, restricting the maximum Atondue that can be efficiently coupled into the system.
Consequently, if a display engine possesses an Atondue larger than the waveguide's acceptance aperture, any excess Atondue represents inherent light loss. This means that even if a display is intrinsically bright, a significant portion of its light may not be effectively transmitted through the waveguide if its Atondue characteristics are mismatched. Understanding and optimizing Atondue is crucial for maximizing the efficiency and perceived brightness of AR displays, especially given the already inefficient nature of waveguides.
* In this short video, you can learn:
* The definition and significance of Atondue in display optics.
* How waveguide input couplers impose Atondue limits on AR display systems.
* The implications of Atondue mismatch between a display and a waveguide.
* Why excess Atondue from a display results in unavoidable light loss.
#Atondue, #WaveguideCoupling, #OpticalEfficiency, #DiffractiveWaveguides, #AugmentedReality, #NearEyeDisplays