LED based lamps are starting to show up in this market sector. Current LED-based projectors are mostly portable projectors that offer low brightness and poor image quality, but some home theatre models of decent quality are starting to appear. At present, they're expensive, less bright than most projectors based on traditional lamps, and still require fans for active cooling. However, as LED's become more power efficient and economical, these projectors will hopefully become brighter, passively cooled, and significantly cheaper.
Projectors are not appropriate in many environments, especially those with high ambient light levels, but LED's may help them make major inroads into the big-screen market.
"Plants mainly need blue and red light for photosynthesis and far-red, a colour not even visible to the human eye but visible to the plant….."
This makes LEDs very interesting for this purpose - the ideal light spectrum can be achieved with LEDs. This will make more and more sense over time as the world urbanises further and LEDs get ever cheaper.
http://www.bigpictureagriculture.com/2011/02/plantlab-nether...
Long answer: Typical projectors have two lenses. The one at the front is obvious, since it focusses the image of the LCD/film onto the wall. Just behind the LCD/film is a collimating lens (usually a Fresnel lens), which ensures that all the light produced by the lamp is focussed so that it passes through the first lens. Something like this:
|Collimating lens
||LCD
Lamp .-||-. |Main lens
| .-' || '-. | .-'
|.-' || '-.|.-'
O--------||--------|------
'-. || .-'|'-.
'-. || .-' '-.
'-||-'
It is conceivable that you could arrange an array of LEDs behind the LCD, but you would have to arrange that all their rays are focussed through the main lens. The prevents us from using a large array of LEDs in the same arrangement as above, as the light from the LEDs at the edge of the array would not pass through the main lens. An alternative would be to place the LEDs closer to the LCD, and give each LED a lens sufficient to focus its rays through the main lens. Something like this:
O.|LCD
LEDs |-. |Main lens
with | '-. | .-'
lenses | '-.|.-'
O-|--------|------
| .-'|'-.
| .-' '-.
|-'
O'|
It makes the compelling argument that people are addicted to light. "Tsao calculates that, as a result, light represents a constant fraction of per capita gross domestic product (GDP) over time; the world has been spending 0.72 percent of its GDP for light for 300 years now. If there are other energy markets that show a constant percentage of GDP expenditure over time, Tsao doesn’t know of them."
The first time I saw 100% adoption of compact fluorescents was in Cambodia. They pay $.40/KWhr. That is insanely expensive (unless you live in Germany).
Lighting technology disproportionally benefits the poor rather than than the rich. Anyone that works on it is my hero. My family bought power for $.04 KW/hr, so I could study at night.
But some datacentres are using 48V DC now and then just piping that through a switching regulators in the servers instead of going from AC to DC. That could be workable.
I'll soon be moving to a park home (a relatively-permanent mobile home) that is in need of a fair amount of renovation.
I'll be running all lighting, computers and the TV off 12v DV circuits powered by bank of vehicle batteries and where the batteries are charged from 12v solar panels.
They emit more blue light than incandescent bulbs [1]. If people light their households with LED lights at night, it might shift their circadian rhythms [2]. Screwed up circadian rhythms can have all sorts of negative health/productivity effects.
[1] http://www.designingwithleds.com/measuring-light-quality-phi... [2] https://justgetflux.com/research.html
I'd love to see more applications of LEDs providing the right color temperature and intensity for the time of day, as well as more applications that avoid the bulb form factor. I'd love for my ceiling to emit light like the sky...
http://www.maxspect.com/index.php?option=com_content&view=ar...
One of the models puts out UV, so be careful.
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New phones, tablets, TV's, etc. should come with a warning to keep them "dimmed down" in the evening, or better, keep use to a minimum late in the day. Sure, I know, the odds are about zilch people would actually heed such advice, but it ought to be out there anyway.
Another thing is the the relatively low CRI. For many purposes (industrial, medical, artistic) the spectral output of bright LEDs is far less than ideal. LEDs will probably get closer to "full-spectrum" over time, and no doubt will easily beat the discontinuous spectrum of fluorescent lamps.
LEDs now just need to get cheap enough, and really need to work with existing dimmer controllers.
Android: https://play.google.com/store/apps/details?id=com.vito.lux&h...
Regarding circadian rhythm, light from near-sleep-time television watching is much more of a concern, but that's been a problem for at least 30 years.
I started using F.lux too many years ago now to count, and honestly it really seemed to help. However getting similar kind of functionality on all of your other devices (e.g. Tablets, Phones, TV, etc) is near impossible right now.
As far as I know the "blue light ruins sleep" research is fairly decent, so hopefully it isn't a placebo.
[1] http://www.cool.conservation-us.org/byorg/us-doe/color_quali...
One (the?) reason for low power levels is they generate so much heat and are difficult to cool. LEDs are still primarily heaters - useful in the winter.
