With my 40-year background in LED technology, Editor Keith Dawson asked me to provide a historical overview of the development of LED technology and the applications it was suited for at each stage. To start, the LED chip, or Light Emitting diode, was first invented over 100 years ago. But at that time, scientists felt it was useless, put it aside and focused on other things.
Finally, in the 1960s, the tiny dot of LED (in deep red only) which is the diode and barely visible at just 1 or 2 millicandela, came back. One company called Monsanto made the chip, and another company called Fairchild, molded the chip. That tiny dot of LED started appearing in wristwatches which were used as giveaways at gas stations, store openings, etc. It was very exciting to see that red dot at the time!
Then, in the beginning of the 70’s, when I had the opportunity to look at packaging LED technologies, chips came out using gallium phosphide and gallium arsenide phosphide. With these chemicals, gallium arsenide phosphide provided red, and gallium phosphide gave us green and yellow and the first, commercial LEDs. These were very low intensity, like 10 or 15 millicandela, .015 or .012.
In 1972, when I was one of the junior partners of my elder brother’s company, I worked with molded LEDs in the three colors. The encapsulation epoxy was transparent, and I noticed that they were giving a narrow beam. Plus, it looked like the filament-technology bulb without the base. That’s when I got the idea of putting a base and a resistor and everything else on the LED so that it could be run at a certain voltage.
The only problem was that the beam angle was a little too narrow. I played with it in terms of modifying the unit to give out wide angles. In the 70’s, you had this first generation of commercial LEDs that started becoming suitable for extremely low levels of lighting indicators. That means you didn’t project light. You just saw it.
Then in the 80's, gallium aluminum arsenide and gallium aluminum phosphide were used in LEDs. With these new semiconductors as diodes, the intensity became 100 to 200 millicandela. Everything was moving at a pace of about 10 years and becoming 10 times brighter.
These LED brightness levels could be used for new applications the lower level intensities were not suitable for.
Now, you could see a dot with a higher brightness, and these low-level illuminators were used in flashlights and panel indicators. This is when I started developing clusters where a few LEDs bunched together could be more useful.
For example, one of the biggest advantages of LEDs over the older filament technology was that there was no mechanical or electrical shock. If you had the original filament technology and the application was such that it saw mechanical shock and electrical shock when turning it on and off too many times, the filament would crystallize, and the lights would constantly go out.
With this in mind, I converted the old bulbs into LED bulbs. This way, you could press an on/off LED light many times, and it would never fail. I started working with Otis Elevator (which was one of the first companies to start using our direct incandescent replacement LEDs at that time), along with power plants, utility businesses, and the military which were now using LED lighting in their illuminated push-button switches and indicators. These buttons were for critical functions and could not fail.
Next came the 90’s when LEDs went up to 1000 lumens with gallium nitride technology in various colors. Suddenly, we had very bright colors of green, red, yellow, and blue. Then, scientists started using phosphorous coating over the blue chip, and white light came out of it. That was the breakthrough of the LED white light, which I thought would take another hundred years, and it happened much faster. This light was used in small flashlights, marker lights, large indicators, third brake-lights, machine status indicators in factories, and much more.
Today’s LED Light Growth
The explosive growth of LEDs in the last 10 years has now become 25,000 lumens. Today, over 90% of indoor and outdoor lighting applications can now be done with LEDs with a major reduction in energy. (Commercial LEDs are reaching 150 lumens per watt, while fluorescents are only 50 lumens per watt.)
Efficiency, the amount of light coming out and the lumens-per-watt are increasing. And in the early 2000’s, the cost was very high, but now, 10 years later, the cost is coming down.
The advancement of LEDs is very exciting, and I look forward to see what’s ahead.
What are your thoughts on the future of LED lighting process? Please comment below or write to me at www.ledtronics.com.
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Posted at All LED Lighting, 8/9/13
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