Strona główna LED Technology
About LED

Although we often do not realize that, LED lights have been commonly used in our everyday life for many years and soon their presence in various devices will be a necessity. Why? Because soon they will replace traditional bulbs, fluorescent lamps and all other known lighting systems.

LED lights (Light Emitting Diode) are electroluminescent diodes and belong to the 4th generation of light source. The name comes from the method of light creation. Traditional light sources use the effects of burning, glowing or electric discharge in couples of gases or metals. LED diodes emit electromagnetic waves in the spectrum which is visible for a human eye (light) thanks to the phenomenon of electroluminescence in semiconductor crystal induced by the external electric field.

The list of advantages of LED light should start with its energy-saving functioning or, to put it in a different way, its energy efficiency (performance), which is a power of emitted light in relation to power consumption. Nowadays white LED diodes reach the performance of over 130 lm/W, but soon the diode XLamp XM from CREE company will appear on the market, with the performance of over 160 lm/W (currently used LED frames reach the performance of approx. 80 lm/W — losses on the power and control systems, optics, thermal conditions etc.). Today, the only light sources that have better efficiency are low and high pressure sodium lamps. But, the yellow-orange light emitted by them proves very bad color rendition (ability to reproduce colors of lighted items faithfully), which is the reason why their usage has been limited almost only to lighting highways, fast traffic roads and tunnels where there are no pedestrian sidewalks. Besides, according to the OIDA report (Optoelectronics Industry Development Association) from 2002, the electroluminescent diodes will reach the highest performance of all known artificial light sources in a few years, but, contrary to sodium lights, they will be able to provide white light of any tone (cool, natural, warm) and very high color rendition. It means that the traditional 100 W bulb or 22 W compact fluorescent lamp will soon be replaced by merely 8 W LED light. What shows how important it is for the global economy is the fact that 20% of the total energy production on the earth is used for lighting purposes.

The other significant feature of the 4th generation light source is its longevity. Unlike the other sources that cease to emit light abruptly, LED diodes „burn out” gradually in a way which is unnoticeable for a human eye. The reliability period after which the light output drops by 30% (to reach 70% its initial output) is indicated by L70 parameter, defined as lumen depreciation of LED diodes. This period depends on many factors (e.g. the quality of materials that a LED chip is made of, a diode casing construction and working temperature) and fluctuates between 30 000 and 100 000 hours, which is a period sometimes several dozens times longer than the longevity of traditional lights. It is also worth mentioning that lumen depreciation by 30% will be barely noticeable for a human eye, so we can say that the diodes life span in many applications is much longer and it is up to us when to replace the lights with the new ones.

Another advantage of LED technology is the abovementioned possibility to produce diodes emitting white light of any tone (color temperature) and high color rendition (Ra > 95%). These parameters are crucial in many industries where the color of the lighted items is very important for making decisions, e.g. in medicine (surgical lamps — to recognize tissue condition), in automotive industry (street lights, dipped headlights — better visibility in the night), in commerce (product lighting — some products look better in a warm, others in a cool color tone). The color temperature can influence our wellbeing, so it is very important for daily use in generally used lighting. In cool tone light people show better ability to focus attention, while warm tone light is perceived as more pleasant and creates ambience where is it easier to relax.

LED diodes are also the only source of light that can directly emit color light (red, green, blue, yellow, amber). Thanks to this feature there is no need to use color filters, which could lower the light output and quality, to gain colorful effects (e.g. in advertising signage lighting, building illumination, automotive and street lights). Now LED RGB diodes provide us with unlimited light effects thanks to the possibility to mix colors in required proportions. LED RGB lighting allows to achieve almost every color, e.g. purple or pink, by appropriate mixing of three basic colors: red, green and blue.

Nowadays ecology is another important factor to consider, and also here the LED diodes outpaced the competition in every respect. Electroluminescent diodes do not contain harmful substances (e.g. mercury), do not require a special utilization methods and do not emit undesirable UV or IR radiation. The last feature makes the diodes available for usage in museums and to light food, cosmetics or medicaments, because they do not heat up the items being lighted and do not harm their structure with UV radiation.

LED lights are also fully resistant to frequent turning on/off and low temperature. These two parameters have particular significance for currently used fluorescent lights because of their huge impact on light performance (at the temperature of 0°C the fluorescent light flux performance drops by 30%) and life span (turning a light on/off 10 times a day shortens its life span by 25%).

Contrary to most other light sources, LED diodes are powered with low-voltage, safe, direct current. Other light sources, e.g. the incandescent lamps or bulbs, are powered by electrical network of 230 V voltage, and neon lights can be powered with a current of many thousands volts! The light emission in LEDs excludes any spark production, which makes them available for usage in areas where high fire or explosion risk exists. The small size of the diodes and their high durability against mechanical damages/shocks are another important factors (there are no easily broken glass parts, no leaks can occur).

There is no doubt that LED diodes are the most perfect source of light that has been discovered in history and even the largest light industry producers admit off the record that diodes, now making 5% turnover in the industry, will make 95% of the total light market volume in several years. In many industries, like advertising, it is impossible to manage without diodes because they are the only reasonable solution.

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