As a modern culture, we crave artificial white lights — the brighter the better, and ideally using less energy than ever before. To meet the ever-escalating demand for more lighting in more places and to improve the bulbs used in sports stadiums, car headlights and street lamps, scientists are scrambling to create better light-emitting diodes (LEDs) — solid state lighting devices that are more energy efficient than conventional incandescent or fluorescent light sources.
Just one thing stands in the way: “droop,” the term for a scientific problem related to LEDs currently in use. Droop refers to the fact that LED efficiency falls as operating currents rise, making the lights too hot to power in large-scale applications. Many scientists are working on new methods for modifying LEDs and making progress toward cooler, bigger and brighter bulbs.
Now investigators at University of California, Santa Barbara, led by material scientists Kristin A. Denault and Michael Cantore, have devised an alternative means of creating high-power white light by using a different excitation source — a laser diode in combination with inorganic phosphors, instead of the traditional LEDs.
Their laser-based lighting options are high in efficiency and high in performance metrics, according to their study, which is described in the journal AIP Advances, which is produced by AIP Publishing.
“We found two ways to create high-intensity ‘cool’ white light, explained Denault. “In one we used a blue laser diode and yellow-emitting phosphor powder with a luminous flux of 252 lumens, which is comparable to current high-brightness white LEDs. For our second method, we used a near-ultra-violet laser diode and a combination of red-, green-, and blue-emitting phosphors.”
They also achieved a variety of other color temperatures with high color rendition, broadening the range of applications for these new lights, she said.
Such continuing advances in LED technology are impressive and welcome, matching and even exceeding my expectations.
Nonetheless, I am evermore concerned with the lack of public presentations regarding optical SAFETY of widely used LED devices.
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Concerns needing to be addressed:
_* LEDs are small-source Lasers.
_* They tend to produce largely coherent, relatively bight and narrow light beams.
_* Lenses, such as in our eyes, focus point sources onto small spots, e.g. on eye retinas.
_* Coherent sources when focused tend to add constructively, resulting in much higher concentration than ordinary incoherent sources.
_* !! In other words, looking toward a laser from within the beam’s illuminated area can result in eye damage.
_* Oncoming automobile headlights (especially high beams), especially when approaching close by (or from mirrored tail-gators), concern me.
_* Note: Laser labs always have warning lights and signs!
_* Headlights, floodlights, and even nearby flashlights are high intensity illuminators.
_
_* Under what conditions and methods of use are they safe?
_* Under what conditions and methods of use are they NOT safe?
_* How likely will common usage be safe?
_* Consider long-term accumulation of eye damage, even if severe only infrequently. How serious can this be?
_
Notes:
_* Truly white light (i.e. broadly mixed frequency distribution) spreading the focal lengths, may reduce constructive intensification.
_* _* The above is much less true if distribution is limited to a small selection of narrowly-spread colors.
_* Fracturing the generated beam reduces the intensity of lens-focused spots, although it multiplies the number of spots affected.
_* Diffusing the generated beam can significantly reduce the intensity.
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Summary:
_* Perhaps LED usage has been thoroughly tested regarding private and public hazards.
_* Perhaps LED light sources are indeed harmless in all possible uses.
_
_* But, since LEDs have come into common usage, I have not seen general public risk advisories as to their safe use.
_* Nor have I seen publications regarding conditions and procedures for their safe use — nor for potential hazards.
_* Nor have I seen Safe Use or Risk Potential alert notices on packaging or user guides!!!
_
_* If I have erred in fact or in implication above, please correct my mistakes, preferably with specifics.
_* I would happy to find reassurance in discovering
_* _ that all is good and safe (at least in this aspect of life),
_* _ and/or that I had somehow overlooked clear sufficient evidence that has always been directly available.
_
_ I reiterate my high interest and encouragement for scientific and technological advances such as these.
_ But I also am unhappily astonished at the careless lack of Hazard and Safety reviews provided — or, if elsewhere, at least referenced.
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__ __ — >>>>>>>>> PUBLICATIONS such as yours SHOULD ADDRESS
__ __ — >>>>>>>>> or at least Reference and Summarize these concomitant ISSUES.
__ __ — ^^^^^^^^^^^^^^