5 ms·

> Engineers need to build LEDs that more efficiently convert electrons into light, if the devices are to become the future of artificial lighting, as many expec

> Engineers need to build LEDs that more efficiently convert electrons into light, if the devices are to become the future of artificial lighting, as many expect they will. I was under the impression that LEDs were already the present of artificial lighting...

eecc 9y ago
Later on it says we don't really know how to optimize the light emission process. This mathematical tool provided a means to develop better simulations and explore the parameters more efficiently
slackingoff2017 9y ago
LED's are nearing theoretical max efficiency, somewhere near 220lm/watt for pure white light. Essentially the perfect light source. The most efficient white LED's are actually blue ones with a white phospor but it's still pretty close. I wish we could do the same with sound and cameras, a place where our efficiency is still laughable theoretically and compared to the natural human sensors.
- Zak 9y ago
  Most commercially produced white LEDs are a phosphor over a blue or occasionally violet LED. The alternative is to mix the light from red, green and blue LEDs, which produces a very peaky spectrum that distorts colors badly. Regardless of efficiency, the phosphor approach is more popular because it produces white light that's tolerable to use. Even phosphor spectra have peaks and valleys though, and evening them out usually reduces efficiency. The most common representation of this is color rendering index (CRI), which measures color accuracy. I think that's usually the right tradeoff, as a little less light with a broad spectrum is usually more effective illumination, but the market is driven by the mighty lumen-per-watt.
  - euyyn 9y ago
    > The alternative is to mix the light from red, green and blue LEDs, which produces a very peaky spectrum that distorts colors badly What does the phosphor emit? There's no "white" wavelength. So a more homogeneous spectrum?
    - slackingoff2017 9y ago
      Roughly, if the average color of something is white your eyes will make it look white. Since we only have three color receptors you only need red green and blue in the proper amounts. The rest of the visible spectrum is naturally interpolated. An approximation of white doesn't work for reflections which is the main reason this method isn't ideal. Real world objects can reflect different wavelengths very unevenly so even if these sources appear white directly their reflections take on a variety of strange hues. The phospor spreads out the peaks so the light spectrum emitted is smoother, closer to black body radiation which is the type of light emitted by the sun. Humans are wired for sunlight so this makes things look better.
      - mortenjorck 9y ago
        Yep. Imagine a spectral histogram. Pure white light looks like this: R G B _=============_ A surface that reflects the wavelength at “x” will look fully saturated and bright: R G B _=============_ x But now imagine a “peaky” white. The histogram has peaks at pure R, G, and B, but the other wavelengths are underrepresented or absent. R G B _=_ _=_ _=_ The light will look white to the eye, and surfaces that reflect a wide spectrum will look relatively normal. But look at our hypothetical narrowly-reflective surface from before: It falls in between the peaks, and thus will have a washed-out appearance. R G B _=_ _=_ _=_ x
- lightedman 9y ago
  "LED's are nearing theoretical max efficiency, somewhere near 220lm/watt for pure white light." Cree has already hit 300+ lumens per watt at room temperature and 1W power throughput, and are showing no signs of slowing. The problem with LEDs is not wave issues, but the Auger Effect where electrons recombine with the LED junction material instead of going through the electron hole. However, CRI is still meh. For gem work, you want sunlight or incandescent, nothing else is acceptable because you need a true blackbody radiator. LEDs work fine for isolating and orienting stars, adularescence, schiller, and sheens, but are horrible for tenebrescent gems, some dichroic gems, and such. Also, some LED-covered wavelengths are still utterly useless when compared to other sources. UVB LEDs at their best are only about 2% efficient. You might as well stick with a raw phosphor-less fluorescent tube with glass filters for UVC and UVA on it at that point, you'd still push roughly 30% efficiency. Red LEDs are also still rather meh on the efficiency scale.
  - slackingoff2017 9y ago
    Yeah, the main problem with LEDs is that you only get max efficiency if you can find something with the right bandgap. Right now that means deep blue. 220 w/lm is theoretical max for a smooth spectrum of white light. If you get to choose a spectrum you can get much higher using green centered at 555nm. If any "white" light advertises close or above 220 lm/watt the CRI suffers. It means they're using light that activates the human retina better but isn't actually a pure white. Lumens are calculated based on human eye response https://en.m.wikipedia.org/wiki/Luminosity_function https://en.m.wikipedia.org/wiki/Luminosity_function Looked at this way blue lights are pretty terrible. But if you look at mw of photons vs energy input deep blue LED's are close to 80% efficient.
wlesieutre 9y ago
I work at an architectural lighting manufacturer, and yes, they definitely are. It killed incandescent/halogen first, then CFL. Metal halide (especially high wattage) and linear fluorescent are still hanging on by a thread, but everybody in the industry acknowledges that they're on the way out. When I was in college (class of 2012) LED lighting was on the rise but the industry imagined they would take over much more slowly than what actually happened. We were still taking about CFLs as something that might come up more than once after we graduated.
- hammock 9y ago
  And at the same time, lots of (anec?)data coming out that LEDs have adverse health effects
  - danmaz74 9y ago
    Example?
    - hammock 9y ago
      http://www.ledsmagazine.com/articles/2010/11/light-and-human-health-led-risks-highlighted.html http://www.ledsmagazine.com/articles/2010/11/light-and-human... http://www.cnn.com/2016/06/21/health/led-streetlights-ama/index.html http://www.cnn.com/2016/06/21/health/led-streetlights-ama/in...
      - Retric 9y ago
        That has little to do with LED's just a subset of cheap LED's.
        wlesieutre 9y ago
        Pretty much all white LEDs are going to have high blue content. It goes back to how they work, these are actually phosphor converted blue LEDs where they pump out a ton of blue light and then use a phosphor layer to absorb and re-emit some of it at other wavelengths. See spectral distributions here: http://cdn2.goughlui.com/wp-content/uploads/2013/06/spectraldist.gif http://cdn2.goughlui.com/wp-content/uploads/2013/06/spectral... Even down at 2700K (blue line, "warm white") there's a substantial blue spike over on the left. The LEDs being used in most streetlights are cool white, probably 4000K+, definitely a lot of blue in that. There are high CRI LEDs available (Color Rendering Index - at warm colors it basically means "how similar do colors look under this vs under incandescent"), but they're much less efficient in terms of how much light you get per watt, and they tend to be a pretty niche product for lighting stuff where reds are important (brick walls, fruit, art, etc). Still some blue in that, but much less. https://www.yujiintl.com/img/graphics/warm-white-high-cri.png https://www.yujiintl.com/img/graphics/warm-white-high-cri.pn... As to health effects, from what I've heard the jury is still out, but there's a definite push toward "tunable white" in the industry. Whether anyone actually wants to pay for that when it comes time to choose between that or the cheaper fixed color temperature that we've been doing forever, things are less certain...
voidmain0001 9y ago
I believe HN reported the return of the incandescent light bulb over a year ago: https://news.ycombinator.com/item?id=11771001 https://news.ycombinator.com/item?id=11771001 which I believe is based on this Nature article: http://www.nature.com/nnano/journal/v11/n4/full/nnano.2015.309.html http://www.nature.com/nnano/journal/v11/n4/full/nnano.2015.3... What's old is new again...
- danmaz74 9y ago
  So, maybe the future of light will be incandescent again. But the present is led :)

eecc 9y ago

Later on it says we don't really know how to optimize the light emission process. This mathematical tool provided a means to develop better simulations and explore the parameters more efficiently

slackingoff2017 9y ago

LED's are nearing theoretical max efficiency, somewhere near 220lm/watt for pure white light. Essentially the perfect light source. The most efficient white LED's are actually blue ones with a white phospor but it's still pretty close. I wish we could do the same with sound and cameras, a place where our efficiency is still laughable theoretically and compared to the natural human sensors.

Zak 9y ago
Most commercially produced white LEDs are a phosphor over a blue or occasionally violet LED. The alternative is to mix the light from red, green and blue LEDs, which produces a very peaky spectrum that distorts colors badly. Regardless of efficiency, the phosphor approach is more popular because it produces white light that's tolerable to use. Even phosphor spectra have peaks and valleys though, and evening them out usually reduces efficiency. The most common representation of this is color rendering index (CRI), which measures color accuracy. I think that's usually the right tradeoff, as a little less light with a broad spectrum is usually more effective illumination, but the market is driven by the mighty lumen-per-watt.
- euyyn 9y ago
  > The alternative is to mix the light from red, green and blue LEDs, which produces a very peaky spectrum that distorts colors badly What does the phosphor emit? There's no "white" wavelength. So a more homogeneous spectrum?
  - slackingoff2017 9y ago
    Roughly, if the average color of something is white your eyes will make it look white. Since we only have three color receptors you only need red green and blue in the proper amounts. The rest of the visible spectrum is naturally interpolated. An approximation of white doesn't work for reflections which is the main reason this method isn't ideal. Real world objects can reflect different wavelengths very unevenly so even if these sources appear white directly their reflections take on a variety of strange hues. The phospor spreads out the peaks so the light spectrum emitted is smoother, closer to black body radiation which is the type of light emitted by the sun. Humans are wired for sunlight so this makes things look better.
    - mortenjorck 9y ago
      Yep. Imagine a spectral histogram. Pure white light looks like this: R G B _=============_ A surface that reflects the wavelength at “x” will look fully saturated and bright: R G B _=============_ x But now imagine a “peaky” white. The histogram has peaks at pure R, G, and B, but the other wavelengths are underrepresented or absent. R G B _=_ _=_ _=_ The light will look white to the eye, and surfaces that reflect a wide spectrum will look relatively normal. But look at our hypothetical narrowly-reflective surface from before: It falls in between the peaks, and thus will have a washed-out appearance. R G B _=_ _=_ _=_ x
lightedman 9y ago
"LED's are nearing theoretical max efficiency, somewhere near 220lm/watt for pure white light." Cree has already hit 300+ lumens per watt at room temperature and 1W power throughput, and are showing no signs of slowing. The problem with LEDs is not wave issues, but the Auger Effect where electrons recombine with the LED junction material instead of going through the electron hole. However, CRI is still meh. For gem work, you want sunlight or incandescent, nothing else is acceptable because you need a true blackbody radiator. LEDs work fine for isolating and orienting stars, adularescence, schiller, and sheens, but are horrible for tenebrescent gems, some dichroic gems, and such. Also, some LED-covered wavelengths are still utterly useless when compared to other sources. UVB LEDs at their best are only about 2% efficient. You might as well stick with a raw phosphor-less fluorescent tube with glass filters for UVC and UVA on it at that point, you'd still push roughly 30% efficiency. Red LEDs are also still rather meh on the efficiency scale.
- slackingoff2017 9y ago
  Yeah, the main problem with LEDs is that you only get max efficiency if you can find something with the right bandgap. Right now that means deep blue. 220 w/lm is theoretical max for a smooth spectrum of white light. If you get to choose a spectrum you can get much higher using green centered at 555nm. If any "white" light advertises close or above 220 lm/watt the CRI suffers. It means they're using light that activates the human retina better but isn't actually a pure white. Lumens are calculated based on human eye response https://en.m.wikipedia.org/wiki/Luminosity_function https://en.m.wikipedia.org/wiki/Luminosity_function Looked at this way blue lights are pretty terrible. But if you look at mw of photons vs energy input deep blue LED's are close to 80% efficient.

wlesieutre 9y ago

I work at an architectural lighting manufacturer, and yes, they definitely are. It killed incandescent/halogen first, then CFL. Metal halide (especially high wattage) and linear fluorescent are still hanging on by a thread, but everybody in the industry acknowledges that they're on the way out. When I was in college (class of 2012) LED lighting was on the rise but the industry imagined they would take over much more slowly than what actually happened. We were still taking about CFLs as something that might come up more than once after we graduated.

hammock 9y ago
And at the same time, lots of (anec?)data coming out that LEDs have adverse health effects
- danmaz74 9y ago
  Example?
  - hammock 9y ago
    http://www.ledsmagazine.com/articles/2010/11/light-and-human-health-led-risks-highlighted.html http://www.ledsmagazine.com/articles/2010/11/light-and-human... http://www.cnn.com/2016/06/21/health/led-streetlights-ama/index.html http://www.cnn.com/2016/06/21/health/led-streetlights-ama/in...
    - Retric 9y ago
      That has little to do with LED's just a subset of cheap LED's.
      - wlesieutre 9y ago
        Pretty much all white LEDs are going to have high blue content. It goes back to how they work, these are actually phosphor converted blue LEDs where they pump out a ton of blue light and then use a phosphor layer to absorb and re-emit some of it at other wavelengths. See spectral distributions here: http://cdn2.goughlui.com/wp-content/uploads/2013/06/spectraldist.gif http://cdn2.goughlui.com/wp-content/uploads/2013/06/spectral... Even down at 2700K (blue line, "warm white") there's a substantial blue spike over on the left. The LEDs being used in most streetlights are cool white, probably 4000K+, definitely a lot of blue in that. There are high CRI LEDs available (Color Rendering Index - at warm colors it basically means "how similar do colors look under this vs under incandescent"), but they're much less efficient in terms of how much light you get per watt, and they tend to be a pretty niche product for lighting stuff where reds are important (brick walls, fruit, art, etc). Still some blue in that, but much less. https://www.yujiintl.com/img/graphics/warm-white-high-cri.png https://www.yujiintl.com/img/graphics/warm-white-high-cri.pn... As to health effects, from what I've heard the jury is still out, but there's a definite push toward "tunable white" in the industry. Whether anyone actually wants to pay for that when it comes time to choose between that or the cheaper fixed color temperature that we've been doing forever, things are less certain...

voidmain0001 9y ago

I believe HN reported the return of the incandescent light bulb over a year ago: https://news.ycombinator.com/item?id=11771001 https://news.ycombinator.com/item?id=11771001 which I believe is based on this Nature article: http://www.nature.com/nnano/journal/v11/n4/full/nnano.2015.309.html http://www.nature.com/nnano/journal/v11/n4/full/nnano.2015.3... What's old is new again...

danmaz74 9y ago
So, maybe the future of light will be incandescent again. But the present is led :)