Today, Enody announced our first release in the Enody Platform series of devices, EP01. Enody Platform devices are designed from the ground up to not only fix the shortcomings of existing LED lighting, but to dramatically increase the capabilities of consumer lighting products. Additionally, Enody Platform devices are focused on providing a stable and accessible development interface for customization and research.

While increased capabilities and an accessible interface are easy to claim, they are much harder to achieve. With this in mind, we are also launching the Enody Journal (of which this is the first entry). The Enody Journal will be the direct communication pipeline from us to you. It will provide background and insight into the technology, design, and considerations behind every Enody product. We're not interested in deceptive marketing to get customers. Instead, we're going to take the time to explain our goals, our interests in these goals, and what we have done to achieve them.

Over the next few months, we're going to take you on a deep dive into EP01. This compendium will eventually cover many topics including physics, evolutionary biology, color theory, optimization, and platform architecture. For our first issue, we are going to go over a brief history of lighting and introduce the flagship feature of EP01, Spectral Tuning.

Measure

Three years ago, I set out to fix LED lighting. I didn't know exactly what was wrong, or even how to properly measure lighting, but I did know that almost all LED lighting felt bad. I wasn't alone in this feeling either: Nearly everyone I talked to had a distaste for LED lighting. What was going on? What was causing this seemingly primal experience? Why couldn't we elaborate past it "feeling bad" ?

Before I could begin to address this shared feeling, I needed to build up my vocabulary and understanding of light itself. I needed to learn how to quantify and measure light's fundamental characteristics. Light effectively has three categories of measurable qualities:

Each of these qualities play an integral role in our perception of any light source. If any one of these qualities is degraded, the light will feel bad, regardless of how well the light source performs in the remaining qualities. For the rest of this journal entry, we're going to cover the spectral qualities of light.

Spectral

Light is a mixture of colors. Red light is a mixture that contains primarily red, blue light is a mixture that contains primarily blue, and white light is a relatively even mixture of all colors. This was famously shown by Isaac Newton in his prism experiments. When a beam of light hits the surface of angled glass, the mixture of light will separate by color.

With this simple device, we can observe the mixture of color within the light. While this experiment produces beautiful results, it doesn't give us a repeatable way to objectively measure the color mixture. Mostly red, and a lot of blue with a thin orange line aren't going to cut it. We need two exact measurements:

Each color has a property called wavelength that defines its position in the separated color mix. The smaller (and therefore shorter) the wavelength, the more the light bends when it hits the prism's angled glass surface. If we use a sensor to measure the power after the light has been separated, we can produce a plot that characterizes the contents of the light.

This plot is called a spectral power distribution (abbreviated as SPD). With an SPD, any mixture of light can be concretely measured and recorded. SPDs are the foundational measurement upon which all modern color theory is based (which we will explore in a future journal entry).

Blackbody

The name Enody comes from combining the words enhanced and blackbody. While enhanced is self explanatory, what is a blackbody? A blackbody is a naturally occurring emitter of light. When any physical object is heated up, it will emit light. Without a doubt, you have seen this many times throughout your life. A hot piece of metal, the wisps of a campfire flame, and even the Sun itself are all examples of blackbody emitters. Blackbody emission is by far the most common natural phenomenon that illuminates our world.

One defining characteristic of blackbody emission is that it produces a smooth, continuous SPD that is dependent on its temperature. When looking at a blackbody emitter's SPD, there will not be any sharp peaks or valleys. At low temperatures, a blackbody emitter will produce a smooth curve containing mostly red light. Some examples of low temperature blackbody emitters are glowing embers in a fire, a lava flow, and the coils in a toaster.

As the temperature of the blackbody emitter increases, the SPD shifts and transforms to contain increasing amounts of light in the blue/green region. Due to the existing presence of red within the mixture, this increase of light in the blue/green region means the mixture now contains all colors, which in turn results in a light that appears white. The best example of a higher temperature blackbody emitter is midday sunlight.

The temperature of a blackbody emitter is measured in Kelvin, which you may have seen it on light bulbs abbreviated as K (i.e. 2700K warm white). Light bulbs use this specification as the filament within incandescent bulbs is itself a blackbody emitter heated up by electricty flowing through it. In an admittedly confusing collision between scientific principles and our collective lighting vocabulary, warm white blackbody emitters are actually physically colder than cool white blackbody emitters.

One issue with blackbody emitters is the amount of their power that falls outside of the range visible to humans. For a typical campfire (~1300K), only 0.04% of the emitted light is visible to the human eye. The remaining 99.96% is emitted as infrared light. Infrared light cannot be seen, but it can be felt on the skin. While the infrared emissions of a campfire can feel good on a cool summer's night, it's wasted energy when the goal is illumination. Even when considering the much more evenly spread 2700K incandescent light bulb, 91% of the emitted light is invisible.

Past

Spending 10x more energy emitting infrared light than emitting visible light didn't sit well with humanity, so we invented our own non-blackbody light sources. First, in the 1940s, fluorescent lighting took over as the preferred form of energy-efficient lighting. Fluorescent lighting differs from blackbody emitters in that it does not rely on heating an object to produce light emissions. Instead, mercury atoms are excited until they release energy. This released energy is absorbed by a coating on the inside of the bulb and is converted into visible light through fluorescence.

Hang on, that SPD looks nothing like the SPD of a blackbody emitter. Instead of a smooth, continuous curve, fluorescent lighting emits a series of very distinct peaks. Through proper mixing, these peaks can combine to produce a light that appears white when looked at directly, but contains a significantly less smooth distribution than a comparable 4100K blackbody emitter.

Any object being observed under fluorescent lighting will suffer from significant discoloration. Overpowered regions will exhibit oversaturation of the color, while underpowered regions will exhibit desaturation and apparent greying. The difference between these SPDs is what gives fluorescent lighting a distinctly sharp feeling.

Present

In 1993, Shuji Nakamura succeeded in creating the first blue Light Emitting Diode (LED), opening the door to LED-based lighting. Similar to fluorescent lighting, LED bulbs achieve a white mix by converting a portion of a blue LED's energy light to the green, yellow, and red regions, while leaving a portion as blue. This conversion is performed by materials that absorb one type of light and output another, also know as phosphors.

While this spectral power distribution is much more even than fluorescent lighting, it still doesn't match the spectral power distribution of a blackbody emitter. This is due to limitations in the process of converting blue light to other colors.

In most modern LED bulbs, the phosphors used to convert this blue LED light into the other colors leave artifacts in the spectrum. These artifacts present themselves as sharp spikes in the SPD of the emitted light. Additionally, blue light can easily be converted to green light and beyond, but it cannot easily be converted into the neighboring cyans. This results in near universal absence of cyan light in LED lighting, regardless of the blackbody emitter being emulated.

Future

As humans, we have spent the entirety of our evolutionary history under the illumination of a blackbody emitter. Our visual system is constantly attempting to balance the lighting in the room to best differentiate color. When a light source is emitting non-blackbody light, different colors are muddled and washed out, ruining our ability to properly judge the color of objects in the environment. This leaves us in a state of visual unease, never able to fully relax in a space due to our subconscious visual system working overtime.

Accurate recreation of blackbody emitter SPDs is critical to the performance of any artificial lighting system. As shown above, non-blackbody emitters have been chasing this quality for the last century, but have fallen short. Precise, dynamic, and full-spectrum control is needed in lighting systems to recreate the visual appeal of natural blackbody emitters, while still maintaining the energy efficiency of existing artificial light sources.

EP01 solves this problem as the first spectrally tunable light source for consumers. Spectrally tunable lighting shapes the underlying SPD of the light source, resulting in a light that looks incredibly natural, and provides illumination the human visual system expects.

Instead of relying on a single energy source and fluorescent conversion, EP01 contains individually controlled LEDs with colors across the entire visible spectrum. These LEDs are precisely controlled to produce a mixture that not only achieves a target color, but shapes the underlying SPD to accurately match any target, including blackbody emitters.

As you can see above, EP01 contains no white LEDs. Instead, EP01 recreates the spectral power distribution for blackbody emitters of any temperature. EP01 can emulate the emissions of a candle (1200K) just as easily as the mid-day sun (6500K).

EP01 isn't perfect. There are clearly still peaks and valleys in the animation above. Over time, LED lighting technology will progress further and these peaks and valleys will continue to shrink. In the meantime, EP01 will provide the highest quality dynamic light ever available to consumers.

Spectrally tunable lighting is the next generation of lighting, and there are many more fascinating topics to cover. In the next journal we'll cover how the Enody optimization process generates custom mixes for every EP01 produced.

Until next time,
Carter