The Use and Importance of Phosphors in Lighting Design

The similarity between Citizen Array chip based LED light sources and fluorescent light sources is that they both initially produce essentially monochromatic light and then use a group of PHOSPHORS to execute a “Stokes shift” on the original light wavelength to create longer wavelength colors spectrums. The similarities end there. The differences between the qualities of the two types of light are striking and lead to vastly improved lighting with fixtures using the Citizen LED Array chip vs any fluorescent lighting technology.

A Fluorescent light uses a current conducted through the mercury vapor contained in the fluorescent bulb to produce light in the UV range of the light spectrum and must shift it down to the visible range in order to be useful. It uses a PHOSPHOR coating on the inside of the entire length of the tube to do this. An LED light source based upon the Citizen Array starts out creating light at the far end of the visible spectrum in the light blue area and then uses PHOSPHORS to shift the light down into the visible range by the same Stokes shift mechanism. However, the LED produces light at the very top end of the visible spectra in the light blue region. This makes the shift easier and more energy efficient.

The Citizen LED array chip PHOSPHOR area is also very small compared to the entire inner surface area of a fluorescent tube. A 32 watt 4 ft. T8 flourescent tube has more than 2 orders of magnitude more phosphor surface area than a comparable LED chip with a similar lumen output. The fluorescent tube manufacturers are constrained by cost to use fewer and cheaper PHOSPHORS. The fluorescent tubes that offer better phosphors and therefore better quality light are currently 10- 20 times the price of standard fluorescent bulbs, costing as much as $40/bulb. The better phosphors used by the Citizen LED Array chip creates a much more efficient, healthy and beautiful broad spectra light source than a fluorescent tube. Elimination of the frequency spikes associated with fluorescent lighting allows the eye to be more relaxed and to actually see better at lower light levels, as well as creating a more relaxed and vividly colorful environment. See figures 1 and 2 for light spectrum comparisons of the Citizen LED Array based lighting product vs. the fluorescent lighting product spectrum.

This difference between fluorescent lighting and LED lights based on the Citizen Array chip is easily demonstrated by installing both types of light into the same room and then alternately viewing the same room under the 2 different systems. The difference is strikingly obvious. In one school classroom with Citizen LED Array chip based fixtures, where the adjacent 1st grade classroom lit by fluorescent troffer fixtures was clearly visible from a connecting hallway, an independent electrical contractor who had installed the LED system joked that all the good artists were in the classroom lit by the LED system. The difference in the color vividness was that great between the 2 rooms.

The Citizen LED Array chip based light is actually designed to provide a natural spectrum of light for the human eye. The UV and Infrared portions are omitted, and the visible spectrum is smoothly spread over the entire visible light spectrum. This is similar to the continuous smooth spectrum of sunlight, moonlight, and firelight. In fact, the LED PHOSPHORS can be designed to mimic any of these 3 natural light sources, with the exception that the UV and IR portions are omitted in the Citizen LED Array light spectrum as they are unnecessary and in many instances even harmful.

There are no naturally occurring light sources that mimic the 3 monochromatic spikes of the typical fluorescent light. We do not see well with fluorescent light, but we accept fluorescent light because we have gotten used to it. No user would choose fluorescent light if they actually had a choice, since the fluorescent color spectrum is such a poor match to the eye function. Fluorescent lights are one of the leading causes of headaches due to their unnatural spectrum, flicker, and hum.

These inherent shortcomings of fluorescent lighting make trying to improve fluorescent lighting systems by doing such things as installing better bulbs, or more efficient or smarter ballasts about as effective as putting expensive lipstick on a pig. No matter how much lipstick you put on the pig, or how expensive it is, you are still stuck with a pig.

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