Yochay Danziger | Lumus: How can changing a waveguide's input aperture increase microLED efficiency by a factor of nine?
00:09:36 - 00:10:55
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Summary of the clip:
How can changing a waveguide's input aperture increase microLED efficiency by a factor of nine?
This analysis provides a quantitative comparison of coupling efficiency for a microLED light engine paired with two different waveguide types: diffractive and geometric. The key differentiating factor is the size of the input aperture, which is physically limited in diffractive designs to around 1mm but can be much larger (e.g., 3mm) in geometric designs. This aperture acts as the primary bottleneck for collecting the wide-angle, Lambertian light emitted from the microLED source.
Using a back-of-the-envelope etendue calculation, the speaker demonstrates the dramatic impact of this aperture difference on system performance. For a typical microLED panel, a small 1mm input aperture, characteristic of a diffractive waveguide, might only achieve a coupling efficiency of 0.25%. By simply increasing the aperture to 3mm, as enabled by Lumus's geometric waveguide technology, the efficiency is boosted to over 2.25%, a nine-fold improvement.
The physics behind this gain is straightforward: the input aperture is a two-dimensional area. Therefore, a 3x increase in its linear dimension (from 1mm to 3mm) results in a 3-squared, or 9x, improvement in the area available to collect light. The speaker confirms that this theoretical factor-of-nine improvement is not just a calculation but is consistent with experimental results observed when comparing real-world geometric and diffractive systems, highlighting a critical performance advantage.
In this short video, you can learn:
* How input aperture size is the primary bottleneck for microLED coupling efficiency.
* A quantitative comparison of efficiency for a 1mm vs. a 3mm aperture.
* Why the larger aperture in geometric waveguides can yield a 9x efficiency gain over diffractive ones.
π **Clip Abstract** This clip quantifies the benefit of a large input aperture, a key feature of geometric waveguides, for microLED-based AR systems. The speaker calculates that increasing the aperture from a typical 1mm (diffractive) to 3mm (geometric) can improve light coupling efficiency by a factor of nine.
π Link in comments π
#WaveguideInputAperture, #MicroLEDCouplingEfficiency, #GeometricWaveguides, #DiffractiveWaveguides, #ARDisplays, #MicroLEDDisplays
This is a highlight of the presentation:
Optical efficiency of reflective waveguides for microLEDs
MicroLEDs, AR/VR Displays, Micro-Optics 2025: Innovations, Start-Ups, Market Trends
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MicroLED Connect
More Highlights from the same talk.
00:05:22 - 00:07:40
Why is a "simpler" microLED light engine often less efficient than a complex LCoS system for AR?
Why is a "simpler" microLED light engine often less efficient than a complex LCoS system for AR?
The optical architecture for a Liquid Crystal on Silicon (LCoS) based light engine is a multi-stage, pupil-imaged system. It begins with LED sources that are fed into a homogenizer to create a uniform plane of light. This homogenized plane is then imaged by a series of optics directly onto the input aperture of the waveguide. This design ensures that the light is highly collimated and efficiently directed into the waveguide, maximizing the percentage of light that is successfully coupled.
In stark contrast, a microLED-based light engine is architecturally simpler, consisting mainly of the microLED panel itself and a collimating lens. The microLEDs emit light in a wide, near-Lambertian pattern, meaning light is scattered over a large angular range. The collimating lens can only capture a small fraction of this emitted light and direct it into the waveguide's input aperture. This results in significant inherent optical losses before the light even enters the waveguide.
This fundamental difference in light delivery has major consequences for system design. While microLED projectors are smaller and less complex, they struggle with poor coupling efficiency due to the un-directed nature of their light emission. Furthermore, the large amount of uncollected light can scatter within the projector housing, which may create stray light artifacts and degrade the final image contrast, an issue that is less prevalent in the more controlled, pupil-imaged LCoS system.
In this short video, you can learn:
* The optical architecture of a pupil-imaged LCoS light engine.
* Why direct-emitting microLEDs suffer from low light-coupling efficiency.
* The potential impact of stray light from microLEDs on system contrast.
π **Clip Abstract** This clip contrasts the optical architectures of LCoS and microLED light engines for AR waveguides. The speaker explains how the pupil-imaging design of LCoS systems enables high efficiency, while the Lambertian emission of microLEDs leads to significant light loss and potential contrast issues.
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#LCoSLightEngine, #MicroLEDLightEngine, #LambertianEmission, #OpticalCouplingEfficiency, #AugmentedReality, #ARDisplayTechnology
01:14:23 - 01:16:11
If you shrink a microLED panel by 50%, why do you need 400% more brightness to get the same result?
If you shrink a microLED panel by 50%, why do you need 400% more brightness to get the same result?
The speaker addresses the major industry trend of shrinking microLED panels to create smaller AR projectors, explaining a critical and often overlooked consequence. The final brightness perceived by the user is determined by the total luminous flux (measured in lumens) entering the waveguide, not the luminance (measured in nits) of the panel itself. Total flux is the product of the panel's luminance and its area.
This relationship creates a significant challenge. If a panel's linear dimensions are halved, its area decreases by a factor of four. To deliver the same total lumens into the system and maintain eye-box brightness, the panel's luminance (lumens per unit area, or nits) must therefore increase by a factor of four. This pushes luminance requirements from already-high levels (e.g., 250k nits) to extreme levels (e.g., 1 million nits), a massive technical hurdle for microLED manufacturers.
A more elegant solution is presented that avoids the need for impossibly bright panels. Instead of simply scaling down the entire optical system, one can use improved optics with a lower F-number to collect a wider cone of light from the smaller panel. This strategy compensates for the smaller emission area by capturing a larger percentage of the total light emitted. This approach is only feasible if the waveguide has a large enough input aperture to accept this wider, lower F-number cone of light, directly linking the benefits of geometric waveguides to solving this critical design problem.
In this short video, you can learn:
* Why final AR brightness depends on total lumens, not panel nits.
* The physics explaining why halving a panel's size requires a 4x increase in its luminance.
* How to use improved optics (lower F-number) to overcome this challenge, enabled by large-aperture waveguides.
π **Clip Abstract** The speaker explains the "smaller panel, higher nits" dilemma in AR design, where shrinking a microLED panel requires a squared increase in its luminance to maintain brightness. He then proposes a solution: using superior, low F-number optics to collect more light, a strategy enabled by the large input aperture of geometric waveguides.
π Link in comments π
#MicroLED, #LuminanceScaling, #LowFNumberOptics, #GeometricWaveguides, #AugmentedReality, #AdvancedDisplays