Posted on 12/06/2007 5:00:32 PM PST by decimon
They wink at us every day from computer screens and stereos. But the humble LED is heading for a brighter future.
New generation Light Emitting Diodes will purify water, make lights that mimic the colour of sunshine, and keep private data immune from hackers.
Dr Rachel Oliver, an LED researcher from the University of Cambridge, thinks that they could easily succeed tungsten bulbs as the main way to light our homes.
"LEDs have enormous benefits over standard light bulbs because they're a great deal more efficient, come in a range of different colours and have a very long lifetime. They are also good at saving energy too," she told BBC Radio 4's The Material World programme.
"We could also light up out of the way places where normal bulbs are unsuitable," she added. "Because they last such a long time, architects could cover the side of a building with exciting lighting effects without worrying about constantly replacing the bulbs."
LEDs are made from two halves of a special material called a semiconductor. One half is filled with negatively-charged electrons and the other with positively-charged areas called holes.
Where the two halves meet, the positive and negative charges join together - causing the electrons to emit energy as photons of light.
'Holy grail'
The colour of this light, and thus the LED, depends on the material that is used. Gallium arsenide gives off red light, while gallium nitride produced blue.
"Blue LEDs were the holy grail for a long time," said Professor Jan Evans-Freeman, head of the Centre for Electronic Devices and Materials at Sheffield Hallam University.
"But now blue LEDs are used everywhere, including the backlighting on mobile phones. Gallium nitride has proved to be a very effective material."
Researchers are now using gallium nitride to move beyond blue and into the ultraviolet. The hope is to convert this into white lighting suitable for our homes.
White light is produced in an LED when UV light reacts with a phosphor coating on the inside of the bulb.
As LEDs are around 40% efficient, this makes them an attractive alternative to the 5% efficiency of tungsten bulbs. The problem is the type of white light they produce.
'Cold light'
"The white light they give off is a cold light because it contains lots of blue," said Prof Evans-Freeman. "It's hard to know whether people will accept this kind of light in their living room."
But active research into phosphor chemistry could provide a solution.
Dr Oliver said: "We're aiming for white light that looks like sunshine, and there are scientists trying to mix phosphors in just the right proportions. If we can achieve this, the white will not only look warmer, but could also be useful for people with Seasonal Affective Disorder."
Ultraviolet LEDs also have the potential to revolutionise water quality in the developing world.
A high-energy form of ultraviolet light known as deep-UV kills bacteria and viruses without the need for chemicals. For this reason, deep-UV is commonly used for sterilising water.
But conventional UV lamps are bulky and need replacing regularly. LEDs are significantly smaller, cheaper and have lower energy requirements.
"It's especially exciting from a third world perspective because LEDs could run off solar power or even by some sort of clockwork mechanism. This would bring water purification to people in remote areas," said Dr Oliver.
"But making deep-UV LEDs is a big technological challenge," she said. "Deep-UV can't be made from the combination of materials we're used to, although I certainly think it's possible."
LEDs are currently expanding into the realms of computer security through a method known as quantum cryptography.
It involves sending out a stream of individual photons from one computer to another.
Information can be encoded onto each photon. But the laws of quantum cryptography mean that once someone reads the information, the data on the photon changes.
If one of the photons in the stream is intercepted by a hacker, the information is altered and the message corrupted.
"This will immediately alert the sender and recipient that someone is trying to read the secret message," said Oliver. "The sender can then recode the message and send it again."
Quantum cryptography is not yet sufficiently advanced to be used as a standard technology, but shows promise for ultra-secure internet banking and online data protection in the future.
"People could be using it for financial transactions over the internet in the next 10 or 20 years," she said.
The six and ten clusters in new flashlights are unbelievably birght.
Schroedinger, is that you?
.....and last almost forever. LED’s are not loved by the Energizer Bunny.
bump
“LEDs are made from two halves of a special material called a semiconductor. One half is filled with negatively-charged electrons and the other with positively-charged areas called holes.
Where the two halves meet, the positive and negative charges join together - causing the electrons to emit energy as photons of light.”
Yup, according to the article, no batteries are even necessaary! /nitpick
Well, it was famously just used in the October elections in Geneva, Switzerland so perhaps it's not quite as pie-in-the-sky as the BBC article makes it out to be. For instance, from http://www.physorg.com/printnews.php?newsid=115571103:
Cryptic messages boost data security
The Swiss national elections in October 2007 provided the opportunity to witness quantum cryptography in ‘real-life’ action for the first time. Geneva was first in line to test the unbreakable data code developed by Swiss start-up company id Quantique, paving the way for a new era in data security.
The canton of Geneva became a world pioneer when it decided to use quantum cryptography to protect the dedicated line used for counting votes in the October national elections. The world’s first commercial quantum random number generator and quantum cryptography system was developed by the Swiss company id Quantique – a spin-off company of the University of Geneva – so the choice of Geneva to test the system in action was only appropriate.
...
(Not everyone was so impressed; Bruce Schneier certainly didn't rate this usage very highly in this article.)
Say that again.....I can't see ya....
The security folks at work had these, I asked to borrow a "flashlight".....when I returned it, I said, "You didn't tell me I needed to wear my sun glasses when using this thing..."
Holy crap that thing was bright.
And for a 'what the heck' - I bought out the local Rite Aid supply of multi-color LED Christmas lights - half off.
I thought it was a rather bright idea!
I have one wind-up LED flashlight. Its light is not very bright but it's adequate and needs no batteries. It cost five dollars.
I was but now that you've noticed me I've changed to a cat.
I just bought an Eveready flashlight at Target. It has a single 1-watt LED. It puts out just about as much light as my old 3 D-cell Maglite, but in a white rather than yellowish light. The 2 AAs will last something like 25 hours. It cost $10.
What an improvement over the older tech!
Related:
http://www.freerepublic.com/focus/f-news/1804814/posts
Planet Earth banning common light bulbs
I just bought a Streamlight Stinger-LED rechargeable flashlight. WOW! Different modes —— hi,med,lo plus strobe.
The local Wal-Mart was clearing out some Brinkman LED replacement bulbs for their aluminum flashlights. They were marked down from around $20 to $5. I replaced the Krypton bulb in two of them and the LED is quite a bit brighter. Also last practically forever and use far less battery power.
I just changed out a months-old CFT and wondered why we don’t have LED lights that fit into regular sockets.
They are available but hard to find and expencive.
Currently they are not suited for that application.
After getting his EE degree in the early 80s my Nephew’s first job at HP was designing a machine to sort LEDs for brightness and color spectrum.
Yet the government is in the process of enshrining use of CFLs as the law of the land.
BTW, I haven’t seen much discussion of why LEDs are so much more efficient. Tungsten bulbs put out something like 95% of the energy they use in the infrared spectrum and only 5% in visible light. Fluorescents are something like 65% visible light, while at least some LEDs are above 90%, I believe.
I work with infrared imaging systems, and incandescent bulbs are amazingly bright in infrared, while LEDs are just about invisible.
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