The concept off LEDs technology seems to have been discovered by pioneers in technology and have been applied by companies engaged to designing and manufacturing lightings. The use of LEDs in the field of lighting is moderate and will be expected to increase, because their benefits are superior compared to those of incandescent and fluorescent lamp.
What is LED?
LED, Light-Emitting Diode, consists of a chip of semiconducting material doped with impurities to create a p-n junction. A semiconductor is a material that behaves as a conductor or as an insulator depending on various factors, in the case of the LEDs depending on the polarity as it is connected. When an electron meets a hole, it falls into a lower energy level and releases energy in the form of a photon. And the chip emits light.
Warm lighting or Cool Lighting
The most common method involves coating LEDs of one color with phosphor of different colors to form white light; the resultant LEDs are called phosphor-based white LEDs. The blue photons emitted by High-brightness LED either passes through the phosphor layer without alteration, or they are converted to the yellow photons in the phosphor layer. The combination of blue and yellow photons leads to white light.
The efficacy of LED lighting fixtures is ratio between net lumen output and input power (in watts) of a luminaire, or lm/W. LEDs with the highest efficacy are the coolest whites – 5000 K and above. Highest LED luminaire efficacies are currently in the 100 lm/W range and daily increasing.
Color Rendering Index-CRI
Color rendering index measures the ability of a light source to render colors of illuminated objects faithfully in reference to an ideal light source – sun or incandescent bulb. By definition, ideal light source has CRI equal to 100. Therefore CRI varies from 0 to 100, higher means better.