Linked by weildish on Wed 4th Feb 2009 04:54 UTC
In the News Yes, actually. The old-school, inefficient, heat-generating incandescent bulbs are all but history, CFL (compact florescent) bulbs taking the pedestal what with how relatively inexpensive and efficient they are when it comes to both electricity consumption and overhead cost. However, even these may have a short-lived supremacy as British scientists developed a new way of "growing" the material needed for LEDs on silicon instead of sapphire wafers, which was the original and somewhat expensive way of doing it. Because of this, household-grade lights of LED nature can be produced for under $5.00 and last up to sixty years. LEDs are three times more efficient than CFLs, last substantially longer, and contain no mercury, so they're even more environmentally friendly. These wonder-bulbs are supposed to be available to consumers within two years. It is estimated that if these new bulbs were to be installed in every home and office, it would cut electricity used on lighting by 75%. I'll take twenty of those, please.
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Be careful what you wish for
by Machster on Wed 4th Feb 2009 14:49 UTC
Member since:

There are significant disadvantages (besides the cost) with the current LED technology:

Light quality: Most cool-white LEDs have spectra that differ significantly from a black body radiator like the sun or an incandescent light. The spike at 460 nm and dip at 500 nm can cause the color of objects to be perceived differently under cool-white LED illumination than sunlight or incandescent sources, due to metamerism,[48] red surfaces being rendered particularly badly by typical phosphor based cool-white LEDs. However, the color rendering properties of common fluorescent lamps are often inferior to what is now available in state-of-art white LEDs.

Area light source: LEDs do not approximate a “point source” of light, but rather a lambertian distribution. So LEDs are difficult to use in applications requiring a spherical light field. LEDs are not capable of providing divergence below a few degrees. This is contrasted with lasers, which can produce beams with divergences of 0.2 degrees or less.

Blue Hazard: There is increasing concern that blue LEDs and cool-white LEDs are now capable of exceeding safe limits of the so-called blue-light hazard as defined in eye safety specifications such as ANSI/IESNA RP-27.1-05: Recommended Practice for Photobiological Safety for Lamp and Lamp Systems.

Blue pollution: Because cool-white LEDs (i.e., LEDs with high color temperature) emit much more blue light than conventional outdoor light sources such as high-pressure sodium lamps, the strong wavelength dependence of Rayleigh scattering means that cool-white LEDs can cause more light pollution than other light sources. It is therefore very important that cool-white LEDs are fully shielded when used outdoors. Compared to low-pressure sodium lamps, which emit at 589.3 nm, the 460 nm emission spike of cool-white and blue LEDs is scattered about 2.7 times more by the Earth's atmosphere. Cool-white LEDs should not be used for outdoor lighting near astronomical observatories.

Edited 2009-02-04 14:50 UTC

Reply Score: 2

rexstuff Member since:

All of those are pretty easy to solve, though, through the use of filters, diffusers, etc.

Edited 2009-02-05 08:40 UTC

Reply Parent Score: 1

Machster Member since:

Actually is isn't so easiy. If the peaks in waveform, are filtered, as you suggest, that would also take away from the perceived brightess. This in turn would require more LED's and more power. In addition filters can not fix the dips in the waveform, therefore, the quality will continue to be subpar to non-LED. Diffusers can not completely solve the inherent problems and they can also decrease the brightness.

Reply Parent Score: 1