High-luminance directional lighting (HLDL) refers to light sources that provide bright illumination (luminance) and are designed to focus (collimate) light rays into a beam shape that points in a specific direction. Compared to more diffuse or general-purpose lighting, HLDL offers designers the ability to create lighting schemes that support demanding visual tasks, accent specific objects or features of a building or environment and illuminate the darkest nights or underground spaces (Figure 1).
Figure 1 - Everyday examples of directional lighting.
Flashlights and bike lights that illuminate the path ahead; task lights that shine down on the work area in kitchens, offices, and factories; lighting that enhances architectural features of a building or spotlights works of art; lights for surgical operating rooms and your dentist’s chair; outdoor streetlamps and sports field illumination—these are all examples of high-luminance directional lighting that we encounter every day.
LEDs offer a wide range of characteristics to meet virtually any of today’s lighting needs from the lowest to highest levels of source flux/flux density, from diffuse ambient light to focused task lighting (Figure 2), from broad flood lights to narrow spotlights (Figure 3). Many LED products can be very effective for HLDL applications, combining brightness, energy efficiency, reliability, and flexibility compared to other types of lighting technologies.
Performance Requirements for High Luminance Directional Lighting
Depending on their intended application, HLDL devices can have a wide range of performance requirements that need to be addressed in the design. Various LED structural and design factors can be selected to deliver the desired HLDL on performance, including
- LED chip size and shape (emitting surface)
- LED composition (e.g., white phosphor)
- Optical design
- Beam shape and emitting angle
- Color performance (e.g., CRI)
Colloquially, people refer to the ‘brightness’ of a light source when they want to characterize the amount of light emitting from it; the scientific name for this is luminance. Thus, a high-luminance light source simply means it’s very bright.
Directional means that the light from a source is collimated towards a specific target such as an object or area. Collimation means altering the light beams emitted from the source, so they are parallel, for example, sending the beams through a lens that refracts them at a different angle than their original trajectory (Figure 2 and Figure 3). A lens and/or any other elements that are used to shape the light distribution pattern in this way are called secondary optics.
Figure 2 - Collimation uses an optical element such as a convex lens (left), parabolic reflector, or TIR (Total Internal Reflection) element (right) to reshape light from an LED source so that the light beams are reshaped and focused so they are closer to parallel, as if coming from and shining into an infinite distance.
Figure 3 - Illustration of how a parabolic reflector reshapes an LED beam distribution pattern (represented by the colored shapes) from a broader spherical shape into a directional beam.
Applications of Directional Lighting
High-brightness directional lighting is used in a wide range of indoor and outdoor environments to serve multiple purposes. For all of these applications, secondary optics such as reflectors or lenses are used to shape the light and deliver a specific beam pattern and brightness.
Some common indoor directional lighting applications are spotlights, wall washers, task lights, and track lighting. Directional lighting is often used outdoors for roadway lighting, street lighting, sports fields and stadiums, and canopy lighting, which shines light downwards to illuminate human activity.
Another large category of directional lighting is portable lighting such as flashlights, bicycle lights, and headlamps. In transportation, directional fixtures are used for vehicle forward lighting such as light bars for off-road vehicles. Portable LED work lights are also very common, mounted on vehicles for agriculture or construction.
There are many medical applications of HLDL also. For example, in a surgical operating room directional light helps create a shadowless environment, or headlamps worn by surgeons and dentists. Industrial uses of HLDL include high-speed camera illumination that requires a narrow angle of the light distribution for machine vision applications.
Many of the typical HLDL applications are summarized in Table 1 and illustrated in Figure 4.
Table 1 - Examples of High-Luminance Directional Lighting Applications
Figure 4 – Applications of high-luminance directional lighting include (clockwise from upper left) premium portable lighting such as bicycle lights, indoor directional lighting such as museum/gallery spotlights, outdoor lighting such as streetlamps, automotive auxiliary lights, work lights, and industrial lighting.
Learn more about how to optimize lighting device design and components to achieve the best HLDL performance in the white paper High-Luminance LEDs for Directional Lighting Applications.
Guidance on selecting the right LED for your HLDL application can be found in the Help Center article, “How Do I Select the Right LED for my Directional Lighting Product?”
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