The entire light spectrum of the sun in one LED

The entire light spectrum of the sun in one LED

Technology News |
By Julien Happich

Sunlight has made an essential contribution to the development of life since the creation of the earth, through the evolution of all living beings and into our society today. It influences the entire dynamics of the earth. The sun not only provides light for all living creatures to see, but also serves as a fundamental source of energy that makes life and growth possible in the first place.

Fig. 1: Evolution of light: from sunlight and artificial light
to LEDs, which reproduce the color spectrum of the sun.

With the possibility of generating artificial, electric light, the living space of humans has increasingly shifted to buildings. According to one study, a European spends on average 90% of the day indoors. Since the use of artificial lighting, however, people have been confronted with light that no longer corresponds to natural lighting conditions. The filament lamp was the first large-scale industrial light source to be introduced. Today we use light sources such as fluorescent tubes, energy-saving lamps and increasingly LED lamps. This has made artificial light as energy-efficient and durable as possible. However, the effect on humans was not considered. After all, people are used to the rhythm of day and night. For example, an unnaturally high amount of artificial light at any time of day or night can cause sleep disturbances, as it has properties that differ significantly from those of sunlight. In the long run, this in turn can lead to diabetes, gastrointestinal and cardiovascular problems and other health problems.

Fig. 2: The colour spectrum of sunlight is quite balanced
over the whole spectrum.

The different light sources and their characteristics Sunlight contains the entire color spectrum in an even distribution and provides people with electromagnetic radiation – from the ultraviolet to the visible range and far into the infrared spectrum – thus creating the best possible conditions for well-being and health.

Fig. 3: In comparison, the spectrum of an incandescent lamp.

Visual comfort and color vision also remain unsurpassed in natural sunlight, and it is the ideal light source for high color temperatures with a maximum color rendering index (Ra) of 100. Like the sun, the incandescent lamp is a temperature radiator. The light is generated by heat and therefore the bulb has the full light spectrum. It comes close to the warm-white light of the sun in the evening. In comparison to sunlight (Fig. 2), the colour spectrum of the incandescent lamp (Fig. 3) has a much lower blue component, and the light distribution rises sharply and continuously towards the red and infrared components. These properties make the incandescent lamp the ideal light source for warm-white color temperatures.

Too much heat radiation from the incandescent lamp

The problem with incandescent lamps, however, is that they emit more than 90% of the energy they absorb as thermal radiation in the invisible infrared and therefore have a lower luminous efficacy of around 9 to 15 lm/W compared with other light sources. Under this aspect, many versions of the incandescent lamp may no longer be sold in the EU and other countries. The positive effects of infrared radiation on the human body are disregarded in this one exclusively on efficiency and visually limited evaluation.

Fig. 4: The typical spectrum of a fluorescent lamp with three
distinct bands.

However, other currently available light sources based on the light generation principle of gas discharge and electroluminescence emit a light spectrum that differs significantly from the ideal light spectrum, i.e. in high colour temperatures from that of the sun and in low colour temperatures from that of the light bulb. The widely used fluorescent tubes and energy-saving lamps have large gaps in the color spectrum compared to the ideal sunlight spectrum, because they only emit light in the wavelengths of the excited gas, as can be clearly seen in the comparison of the spectra.

Figure 4 shows a typical light spectrum of a fluorescent lamp, which mainly shows three distinct bands in the blue (at 440 nm), green (at 545 nm) and red (at 610 nm) spectrum. These gas discharge lamps also have the problem of flickering. Even though the flickering is usually not visually detectable, these light impulses can be detected in the brain and can subconsciously trigger stress in humans.

White LED with unbalanced color spectrum

Today, LEDs are installed in almost all light sources. Due to their small size, they offer the advantage that they can be used almost without restriction in terms of luminaire design compared to conventional incandescent and fluorescent lamps. In addition, LEDs make it possible to generate significantly more luminous flux in a very small area and achieve a luminous efficacy of over 200 lm/W.

Fig. 5: With a conventional LED, the peak in the blue
spectrum at around 450 nm is clearly visible.

But even conventional white LEDs differ from the natural, even spectrum of the sun. The white light is produced by conversion from a blue LED with yellow phosphor, which produces an unbalanced color spectrum with a strong blue component at around 450 nm (Fig. 5). The cyan area, which primarily ensures optimal contrast vision, and the red area, which is responsible for energy supply and regeneration via the skin cells, are hardly present here. Although the currently used artificial lighting with gas discharge lamps and conventional LED lights seems to meet the visual needs of humans, this conventional lighting lacks important parts of the spectrum compared to natural full spectrum light. As a result, this unbalanced, artificial light is gradually causing health problems for people, which can range from sleep problems to short-sightedness and serious illness. Under these conditions it is difficult to take into account both the physiological and psychological needs of people.

Special phosphor mixture

euroLighting’s LED products are based on the concept of physical lighting that meets both visual needs – such as natural color vision and easy contrast discrimination – and physiological needs – such as promoting well-being and health, under the name Human Sun Lighting.

Fig. 6: The spectrum of the daylight LED distributed by
euroLighting has an almost ideal sunlight spectrum at
colour temperatures above 5000 K.

By using blue and violet chips and a specially developed phosphorus mixture instead of yellow phosphor, it is possible to produce a light spectrum that comes close to the even sunlight spectrum – without the pronounced blue peak. LEDs such as the Daylight series from Smart Eco Lighting offer an almost ideal sunlight spectrum at a color temperature of over 5000 K (Fig. 5) and also at lower color temperatures. This is achieved by a very similar spectrum to that of the ideal thermal light source over the entire visible range.

Fig. 7: The colour spectrum of the broadband sunlight LED
extends into infrared.

It contains all the important components of light as provided by sunlight. This means that the LEDs can be used in offices, schools and workplaces. They create the conditions to meet the natural needs of humans, but also those of plants and animals. New developments worldwide include broadband solar spectrum LEDs that reproduce the entire visible light spectrum of the sun and additionally emit light down to infrared of 1000nm (Fig. 7).

This means that the healing and regenerative wavelengths already used in medical phototherapy to heal wounds and promote blood flow can be integrated into the lighting – following the example of sunlight.

In the future, not only the visible components of light for the promotion of physical and mental health, but also the infrared wavelengths, which are so important for the energy balance, can be used directly in everyday lighting. LED specialist euroLighting offers a comprehensive range of products and services for lighting, from LEDs as small components and LED modules with and without directly integrated driver technology to finished LED lighting systems such as customer-specific luminaires or the implementation of lighting projects for industry, offices, care or educational facilities.

About the author:

Simone Hettinger is Product Manager for LEDs at euroLighting GmbH –


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