Bharath Rajagopalan | STMicroelectronics: Can we shrink a full RGB laser beam scanning projector to less than 1 cubic centimeter?
04:36 - 06:00
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Can we shrink a full RGB laser beam scanning projector to less than 1 cubic centimeter?
STMicroelectronics has successfully shrunk laser beam scanning (LBS) optical engines from 1.7 cubic centimeters to a mere 0.6 cubic centimeters, making them compact enough to fit seamlessly into the temple of standard glasses frames. This massive footprint reduction was achieved through two key technological innovations.
First, they consolidated individual red, green, and blue laser diodes into a single, highly integrated RGB laser diode module in partnership with ams OSRAM. Second, they developed highly efficient, novel internal combining optics that minimize the volume of the internal beam splitters and collimating elements.
This architectural optimization enables high-brightness projection at low power consumption, proving that LBS is ready for consumer-grade AR smart glasses.
In this short video, you can learn:
* How STMicroelectronics achieved a 2.5x volume reduction in LBS light engines
* The role of integrated RGB laser diode modules in shrinking optical systems
* How custom internal combining optics facilitate temple integration for AR glasses
š **Clip Abstract** STMicroelectronics explains how they reduced the size of LBS optical engines to 0.6 cc by co-developing a singular RGB laser diode module and optimizing internal combining optics. This breakthrough enables highly compact, low-power display engines suitable for fashionable AR smart glasses.
š Link in comments š
#LaserBeamScanning, #RGBLaserDiode, #CombiningOptics, #LBSOpticalEngine, #ARSmartGlasses, #NearEyeDisplays
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11:29 - 13:04
Why does the Lagrange Invariant force AR designers to use 2D pupil expansion?
Why does the Lagrange Invariant force AR designers to use 2D pupil expansion?
The design of near-eye displays for AR wearables is heavily constrained by the Lagrange invariant, which presents major challenges for small-aperture display engines like Laser Beam Scanning (LBS). To ensure a comfortable user experience without requiring physical adjustments for different interpupillary distances (IPD), the system must expand the exit pupil to create a large enough eyebox.
While reflective cascaded beam-splitter waveguides typically offer pupil expansion in only one dimension, diffractive waveguides allow for two-dimensional pupil expansion directly within the grating structure. This makes diffractive optics highly attractive for LBS-based systems, as they can shape the light in both dimensions simultaneously.
Understanding these optical trade-offs is essential for designing AR hardware that balances aesthetic appeal, optical efficiency, and compatibility with diverse human facial structures.
In this short video, you can learn:
* The optical challenges imposed by the Lagrange invariant in small-aperture systems
* The difference between 1D and 2D pupil expansion in reflective vs. diffractive waveguides
* How 2D eyebox expansion accommodates interpupillary distance variations without system adjustment
š **Clip Abstract** STMicroelectronics discusses the optical challenges of small-aperture systems governed by the Lagrange invariant and details how diffractive waveguides solve this via 2D pupil expansion. This allows AR glasses to accommodate varying interpupillary distances without physical adjustments.
š Link in comments š
#LagrangeInvariant, #TwoDimensionalPupilExpansion, #DiffractiveWaveguides, #LaserBeamScanning, #NearEyeDisplays, #AROptics
16:18 - 17:52
Can sub-nanosecond laser pulses solve the optical interference issues in AR waveguides?
Can sub-nanosecond laser pulses solve the optical interference issues in AR waveguides?
Coherent laser light inside diffractive waveguides often generates unwanted interference patterns, such as Newton rings and coherence-induced intensity non-uniformity. To eliminate these artifacts, STMicroelectronics and its partners developed a novel method to break up laser coherency using ultra-narrow pulse injection.
By driving the laser diodes with extremely narrow electrical pulses, they induce a physical phenomenon known as spectral broadening. This broadens the spectral bandwidth of the green laser from a narrow 0.7 nanometers to over 1.2 nanometers, which effectively destroys the temporal coherence of the beam.
The visual result is a dramatic improvement in image quality, yielding near-perfect color uniformity and completely eliminating Newton rings without relying on bulky external optomechanical despeckling components.
In this short video, you can learn:
* How narrow pulse injection induces spectral broadening in laser diodes
* The physics behind reducing temporal coherence to eliminate Newton rings and interference patterns
* The quantitative improvements in spectral bandwidth required to optimize image uniformity in diffractive waveguides
š **Clip Abstract** STMicroelectronics demonstrates how ultra-narrow pulse injection can be used to broaden laser spectral bandwidth and destroy coherency in diffractive waveguides. This elegant modulation technique eliminates Newton rings and interference-induced non-uniformities for superior AR displays.
š Link in comments š
#SpectralBroadening, #NarrowPulseInjection, #CoherenceReduction, #DiffractiveWaveguides, #LaserBeamScanning, #AugmentedRealityDisplays