Three important goals of lighting in an office are (Keeling and Kallaus 1996) : creating an appropriate and safe work area, provide for aesthetic and glare free pleasant vision and save energy.
Light has a direct correlation with ease of reading, lower eyestrain, reduced errors, better turnaround time, reduced risk of musculoskeletal injuries and psychological well being.
There is a vast amount of data indicating that light is one of the biggest challenges to workplace productivity and an area where investments have the fastest payback time and highest return on investment.
Bachner (2000) has demonstrated that employees working in good lighting conditions work faster and with fewer errors.
A 1983 study by Merck showed that 20 % employees were dissatisfied with indoor lighting conditions. Eyestrain has been cited as a leading cause of physical stress. IESNA (Illuminating Engineering Society of North America) recommends a horizontal illumination of 300 Lux if computer use is frequent and 500 Lux if computer use is infrequent. But these are average figures. They do not take into account the variation in individual preference for lighting levels. For example older people need more light. Similarly variation in the nature of job causes differences in individual light preference.
At Canada National Research Council (NRC), their construction scientist recently completed a four-year study with two overlapping activities: the conceptualization of new ideas for office lighting, and laboratory experiments assessing how people would use and respond to the colour-tuning capabilities of these systems.
NRC researchers built two types of LEDs (light-emitting diodes) luminaries in full scale to demonstrate the uses and future applications of this technology.
A corridor demonstration was designed to show how one might use LEDs to provide a visual fire alarm.
In an emergency, the LEDs flash red and guide occupants to the closest exit by scrolling through the corridor from one luminaries to another.
During normal office conditions, the LED luminaries function as regular indoor light sources and emit a high quality white light.
Researcher also built a 1.2 metre x 1.2 metre LEDs lighting panel and built to play back, in real time, a low resolution image of the sky captured from the outside with 289 individual LEDs.
Research shows that in a windowless space, having a sense of outside conditions contributes to occupants’ well being.
LEDs technology is radically different from existing light sources and opens new directions in lighting design although market acceptance will require that it be trusted as healthful and safe, and that its features be valued by users.
The first known report of a light-emitting solid-state diode was made in 1907 by the British experimenter H. J. Round.
The first practical LED was invented by Nick Holonyak, Jr., in 1962 while he was at General Electric Company. The first LEDs became commercially available in late 1960s.
Like a normal diode, LEDs consists of a chip of semi conducting material impregnated, or doped, with impurities to create a p-n junction.
As in other diodes, current flows easily from the p-side, or cathode, to the n-side, or anode, but not in the reverse direction.
Charge-carriers electrons and electron holes flow into the junction from electrodes with different voltages.
When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon.
The wavelength of the light emitted, and therefore its colour, depends on the band gap energy of the materials forming the p-n junction.
Source : Construction Innovation, Vol 17, No. 2, June 2012, Dou Bulb and Evolving Technologies limited
 Better work environment with Led lights Productivity Gains, MyLEDLightingGuide.com