Blog

Post 1: Battery anxiety.

Every smart glasses product on the market runs into the same wall: battery life. Emissive microdisplays and waveguides waste most of the light they generate before it reaches the eye, so the battery ends up dictating the size, weight, and runtime of the whole device. A few hours of use, then back on the charger.

At L-EPD we took the opposite approach and made energy autonomy the first design requirement.

The display is reflective, bistable e-paper. It holds an image with zero power and uses ambient light rather than competing with it, so readability improves as conditions get brighter. For evenings and indoors, a low-power front light takes over. Integrated photovoltaics harvest the same ambient light the wearer is already in.

The result is an energy budget that runs positive outdoors in daylight: the device charges while you use it. Indoors and after dark it draws down a small buffer cell, which the next day outdoors refills. In its intended use, it never needs to be plugged in.

That makes it a fit for people who value runtime over features: skiers, cyclists, hikers and trail runners, field and industrial workers, and anyone spending long days outside who needs glanceable information without managing another battery. Over the next few weeks we'll share more about the physics and where we're taking it first. If you work in optics, displays, eyewear, or hardware investing, we would be glad to connect.

Post 2: Why reflective, bistable EPD

Electrophoretic displays (EPDs) have two properties that matter enormously for a wearable.

1. Bistable. Once an image is written, it stays with zero power. Energy is spent only when content changes. For AR heads-up information like navigation, speed, altitude, time, and notifications, the display is static most of the time. 

2. Reflective. E-paper doesn't make light. It modulates ambient light. In bright conditions, where emissive displays wash out and burn battery to compete with the sun, a reflective display gets more readable. The known trade-offs are refresh speed and color, and we designed around them. We are not trying to replace video AR. We are building glanceable, always-on information that works best exactly where conventional AR works worst: outdoors, in full sun. In twilight and dim indoor settings, a low-power front light can be engaged to keep the display readable. Paired with a birdbath or holographic (HOE) combiner, the EPD image is relayed to the eye while the wearer keeps a clear view of the world.

Post #3: Harvesting the light you’re already standing in

Most AR wearables spend a large share of their energy budget making light. We decided not to make it at all, at least in daylight.

Our approach uses ambient light twice.

First, it forms the image. The display is reflective, so the AR image is built from ambient light the display modulates, not from photons generated on board. The brighter the surroundings, the more light there is to work with, at no energy cost.

Second, it powers the electronics. Photovoltaic cells integrated into the frame convert ambient light into the small amount of electricity the system needs: updating the bistable display (which draws power only when content changes), the controller and Bluetooth link, and, in dim outdoor conditions or indoors, a low-power front light.

Because the image itself costs nothing to illuminate in daylight, the electrical load is small enough for the frame to cover it. Outdoors in daylight the device runs energy-positive, harvesting more than it uses and storing the surplus in a small buffer cell. In twilight, indoors, and at night that buffer carries it until the next time outside. Over a typical day of intended use, the budget balances to neutral or better, with no charger.

L-EPD has built a patent portfolio around this architecture.

Post #4: Why we’re starting on the mountain

Our first product is Ambient Light AR™ smart ski goggles.

The slopes are close to an ideal environment for this technology:

• Intense ambient light, with snow reflecting sunlight from below

• Cold that cuts lithium battery capacity and hurts products that depend on it

• A heavy battery on the head is gone, which matters for comfort over a full day on the hill

• No battery life anxiety on the mountain, far from the nearest outlet

• A user who needs glanceable information (speed, vertical, run and location data, friends’ positions) without pulling out a phone with gloves on

• A form factor that already has room for the optics and a frame-integrated harvesting surface

Just as important is what we left out. There is no camera, no video, no voice assistant, and no Wi-Fi, only a Bluetooth link to your phone. Nobody on the lift wonders whether they’re being recorded. Every radio and sensor we removed is energy we don’t need to harvest. And the goggles show you what you need, when you need it, and otherwise stay out of the way. We think the next wave of AR adoption will come from devices people forget they’re wearing.

Goggles let us prove the platform in a demanding, well-defined market before extending it to cycling, running, other outdoor sports, and eventually everyday eyewear.

Post #5 Adaptive Light, Autonomous Energy: Rethinking AR Wearables

Most AR wearables treat light as something to generate, and they pay for it in battery life. We designed Ambient Light AR™ the other way around: use the light that’s already there, and add only what’s missing.

On a sunny day the mountain is flooded with light, from the sky, from the scene in front of you, and from the snow reflecting it back up. Our reflective e-paper display captures that ambient light and turns it directly into the AR image. In those conditions the image costs almost no energy, and it gets more readable as the sun gets brighter, exactly where emissive displays wash out.

Real conditions change constantly. Clouds roll in, you ski into tree shade, a turn puts the sun behind you. That’s where the adaptive low-power LED front light comes in. It measures how much light the display is actually receiving and fills in only the difference, so the image stays at a steady brightness. In overcast it complements the ambient light. At dusk or night riding it replaces it entirely.

Energy is handled the same way. A solar strip built into the goggle frame harvests far more energy in daylight than the display needs, and banks the surplus in a small battery. That reserve powers the front light through overcast, evenings and night sessions. The result is net energy-positive operation: an AR wearable designed to never need a charger.

Ambient light first. Front light only when needed. Energy from the sun.