Mar 24, 2020

Quality of Light and LED Systems

Category: Illumination
The LUXEON Fusion and Matrix Platform are just two of Lumileds' approaches to advanced LED and component technology that enable luminaire manufacturers to more easily and quickly develop lighting solutions.

The LUXEON Fusion and Matrix Platform are just two of Lumileds' approaches to advanced LED and component technology that enable luminaire manufacturers to more easily and quickly develop lighting solutions.

What is Quality of Light?

Poets and painters have long rhapsodized about the beautiful qualities of light. And though opinions vary as to what makes light beautiful, our minds almost always reference some form of natural light. It might be the crispness of a clear sunrise, the brightness of mid-day light, the warmth of a sunset, or the flicker of an evening flame. Even when we can’t accurately describe quality of light, we know it when we see it. The longstanding challenge for the lighting industry is to replicate the experience of natural illumination with artificial light. Today, LED innovators and scientists are not only capable of reproducing natural light as we see it throughout the course of a day, they are engineering light to provide healthful, manageable, full-spectrum illumination.

Elements of Quality Light
Detailing what constitutes high quality of light from LEDs could make for a doctoral thesis with chapters about semiconductors, phosphors, color spaces and human visual perception. Lumileds engineers and scientists work in all these areas – and more – and maintain a strong focus on energy efficiency and overall sustainability. To simplify, we generally consider the following factors as critical to the illumination of spaces with high quality light.
            • The color of the light
            • Color fidelity and rendering
            • Color consistency
            • Color control

The color of the light
When we talk about the color of light and illumination, we’re really talking about the many possible shades of white light. If you’ve ever been to a paint store you know that there are dozens of shades of white to choose from. The same is true of white light. As with paint colors, people describe various colors of white with a “feeling”: it’s warm, it’s cool, it’s comfortable. Further, humans react physiologically to the color of the light. They might be energized or relaxed by the color of white light selected. So being able to produce the right color, with the right properties and spectrum, for a specific application is essential. The appropriate color of white light for a classroom is very different than the ideal color of light for a romantic restaurant.

Clearly, high quality of light starts with being able to choose the right color for every individual space or environment.

Color Fidelity and Rendering
Color fidelity is an all-encompassing approach to how we see people, objects, and color. The total range of color that we can view far exceeds what light sources have historically allowed us to see. If you’ve ever tried to match blue socks and black socks under incandescent or halogen light, then you’ve experienced the challenge of color fidelity. When Lumileds considers color fidelity, we engineer and evaluate the spectra of the light, the color gamut, and color saturation, as well as industry standard measurements of color. Though imperfect, the most commonly referenced metric for color is color rendering.

Color rendering describes how we see the color of illuminated objects, and multiple metrics exist to describe and measure this rendering. CRI, the color rendering index, is the most common specification used with LEDs. It’s comprised of 15 different color measurements that are combined into a 0-100 scale. Some of the components represent red tones, some represent skin tones and some represent pastels. With so many contributing measurements, different products can have the same CRI and yet render colors differently. Lumileds focuses its efforts on achieving very high CRI scores and it considers the needs of individual product lines and programs before “tuning” its phosphor and LED technologies to ensure that the reds are red, and skin tones look natural.

In addition to achieving high CRIs for its LEDs, Lumileds has developed technologies that can affect how specific colors are perceived. Some of our products increase the saturation of whites, reds, and blues so that they “pop” on a store shelf. White t-shirts might appear brighter and whiter and blue jeans might have a richer blue color than they might under natural light.

Ultimately, color rendering is only one of the indicators of color fidelity. Throughout Lumileds illumination portfolio, color saturation, color gamut, color space, and TM-30 are considered, reported, and engineered to maximize color fidelity in shops, homes, on the street, and even for stadium lighting and high definition television broadcast.

Color Consistency
Color consistency too has many aspects. A lighting manufacturer wants a specific LED to deliver the same color, behavior, and quality of light from piece to piece, order to order, and month to month. Lighting designers and building operators want the light from luminaires to be consistent from fixture to fixture so that there’s no visible difference between them when they’re in the same space. Consistency over time is also critical – visual differences between luminaires should not occur as they age. Increasingly important is consistent behavior as the lighting is changed. In addition to dimming, lighting can be programmed to change from cool to warm and shades in-between.

Every color consistency factor has a direct impact on quality of light, and each requires that the production process, materials, and controls are designed to deliver LEDs with consistent color and behavior in each of the intended use environments. Consistency of color between LEDs over time and temperature – the two of the most impactful factors – depends on experience and expertise in materials science as it relates to the LED semiconductor material and phosphors. No company has more experience, expertise, and success in the development and management of these systems than Lumileds. In fact, auto manufacturers overwhelmingly choose Lumileds for their daytime running lamps and headlights because they know that they can count on Lumileds color consistency to ensure that every light on every car looks the same, even in the harshest conditions. The stringent standards Lumileds achieves for color consistency of automotive headlamps carry over to deliver color consistency to LED solutions for classrooms, offices, homes, and shops.

Color Control
The promise of light emitting diode technology to open a new world of digital lighting is coming to fruition. It’s now possible to dynamically tune the color of white light in virtually any space and to control lighting through commands issued by voice, from a mobile device, or a traditional switch. In this never-before-possible world of lighting, LEDs must respond to commands in a reliably consistent fashion for years and possibly decades. Color and intensity consistency is critical as the human eye can easily detect differences in tone and brightness. Complicating matters is the fact that there are myriad lighting hardware and software combinations in the market with few standards. Regardless of the solution implemented to control the light, the LEDs must respond appropriately and consistently.

The LUXEON Fusion and Matrix Platform are just two of Lumileds’ approaches to advanced LED and component technology that enable luminaire manufacturers to more easily and quickly develop lighting solutions that are not only IoT-ready, but ready to deliver light for the lives and lifestyles we desire.

Quality of Light Realized
We all want quality light. In fact, we expect to see it wherever we are. We know when it’s absent. Delivering quality of light is a complex technology endeavor. Some technologies from previous lighting eras remain and others are still being developed in order to deliver the most natural, comfortable light possible. Gone are the days of simply living with analog illumination. Lumileds continues to drive the concept that never-before-possible lighting is, in fact, possible.