Non-directional light sources

Since non-directional light sources emit equal light levels in all directions, a good measure for the efficiency of the product is its luminous lux (lm) and overall lamp efficacy (lm/W).

The luminous lux, expressed in lumen (lm), is the total quantity of light emitted from a lamp in all directions. Since the human eye is not equally sensitive to all wavelengths within the visible spectrum, the emitted spectrum is weighted by the eye sensitivity curve and integrated over the visual wavelengths 380 – 760 nm.

Although wavelengths below (UV) and above (IR) the 380 – 760 nm range are not taken into account as they do not contribute to the visual spectrum, they can still have a damaging impact in sensitive applications such as museums, art galleries or food illumination. With this in mind, MEGAMAN^®’s LED range of products do not emit any light in the UV and negligible in the IR region and are therefore the preferred choice in UV/IR critical applications.

As overall lamp efficacy (lm/W) of a light source is calculated as the ratio between visible light and the consumed electrical power, the higher the efficacy number, the more efficiently the product converts electrical power into visible light.

Directional light sources

However, the efficacy measurement used for non-directional light sources cannot be transferred to directional ones, as light pollution needs to be taken into account; the glare from the edges of an LED lens, although not useful light, does contribute to a higher efficacy number. So, with directional light sources a new form of measurement is required to show how well a lamp is directing light where it is wanted.

Therefore, the measurement for showing the efficacy of a directional source is luminous intensity (cd). Luminous intensity quantities the light emitted in a particular direction per solid angle and characterises the output for a directional light source.

Luminous intensities in different directions, measured by means of a goniometer, are plotted in polar diagrams. These show the light distribution of the direction light source and enable the beam angle to be determined.

The beam angle of a directional light source is defined as the angle at which the luminous intensity is half of the maximum luminous intensity. The maximum luminous intensity can also be obtained with the use of a lux diagram, since the maximum luminous intensity equals the lux level at a distance of 1 metre.

MEGAMAN^® directional LED light sources

Although the majority of LED products on the market today use lenses to direct light, MEGAMAN^® has developed its unique axial geometry reflector technology. MEGAMAN^® LED reflector technology allows light to be directed without the need for a lens, resulting in better beam control, excellent efficiency and low glare lighting solution.

Diagram 1 : Spectral Response Curve

Diagram 2: Lux Diagram

Diagram 3: Polar Diagram