First I want to say really nice post!
You asked several questions so I will try to address them all.
I wonder if this is what they're using in the Oslon EQ white?
Unfortunately, not. The EQ white emitters are highly efficient, but they are basically just a yellowish-green phosphor that is a little off-white tinted.
They are very deficient in cyan.
I started a thread about this:
http://www.candlepowerforums.com/vb...-EQ-white-LED-emitters-now-available-for-sale
Sounds like I really need to try an Oslon SSL 4000K source!
The SSL family comes in three different levels of color rendering. Be sure to get the high CRI version.
I just went back and played with my 5600K Yuji VX COB,, because I have yet to swap it into a desk lamp I made still containing its original XR-E cools! I can confirm what you have said. It reminds me very much of my days before daylight fluorescents, when I would gel 90W halogens to about 5000K for my work desk! It got replaced with linear fluorescent due to heat issues(!) being in the desert, but I lost a lot in color rendering! Granted the incan and gels (cine CTB filters) aren't perfect either but they were a TON better than triphosphor! This Yuji also reminds me of Sylvania silver Star headlamps, though they're 4000K.
Yes, the very best quality of light comes from filtered halogen, but unfortunately this is very inefficient in terms of energy, and produces a large amount of heat to generate a small amount of light when you want to go up to 4000K.
A little extra heat is not a bad thing in cold climates, where in the winter it can start to get cold and dark early in the evenings, but if there is sweltering heat, you have good reason not to want to leave a 200 Watt filtered halogen lamp on.
That does seem to make it look like the new phosphors are a partial way out of this problem, compared to the older phosphors that resulted in the SPD graph going almost to 0 between the pump and the converted parts.
Yes, phosphors are a
partial way out of the problem. It is still not going to be completely perfect because there will always be a dip between the blue and the peak green emission (unless you put some sort of filter over it I suppose). It is a little too complicated to go into an explanation why that is.
On the other hand, a little dip in the spectrum is a desirable thing, it helps compensate to some extent for the lack of deeper indigo wavelengths to better be able to render saturated blue hues.
I'm thinking of a bad example of this in a (unfortunately lighting) store here. They have WW LEDs at the front counter, but they're the 80 CRI variety, at best. All the blue objects on display look a strong royal blue, even though the overall lighting appearance is warm. It's an odd sensation!
I agree with you. It's probably something many people do not notice, but it just does not look quite right. I actually think just a very small amount of LED light in a room can accentuate the deeper blue colors, but it does not take more than 20-30%. Once you add too much LED light in the room, all the blue hues start looking the same.
Of course a full solution for the blue spike problem is to have the pump be outside the visible spectrum, into the UV, and don't pass it through the phosphors at all. But I realize there are still severe efficiency issues with this approach and I don't even know if it's possible in any form that could be used commercially.
They can be used commercially, but typically only in small spotlights for much higher end applications. Even the high CRI blue-pumped LED spotlights found now in many commercial spaces are usually not used as the
main source of lighting. Using a violet emitter to pump the phosphors results in a decrease in efficiency of about 20-30%. Using deep red phosphors for higher CRI LEDs also results in a substantial loss in efficiency, although they are working to develop more efficient red phosphors (Nexxus Lighting has made commercially available an
R30 lamp with remote phosphor that uses quantum dots in the formulation for higher efficiency).
I just thought of another possible solution: have a blue pump composed of many smaller blue chips, spread out in spectrum over the 435nm to 460 nm or so range
Unfortunately there are no commercially available LEDs that emit over the 485-490nm (greenish-blue/azure) range, which is what you would probably need to truly balance out the shorter deeper blue wavelengths. It is not easy to get around this, if it was you would think that one of those custom D.I.Y. reef lighting hobbyists would have stumbled on a combination that produces light that feels exactly like daylight, which I have yet to hear happening.
If you want to discuss the topic further of combining separate emitters to produce a better spectrum, I suggest we take the discussion to this thread:
problems encountered trying to make a DIY super high CRI array
I know many phosphors have a fairly wide possible pump range, so I wonder how that would affect the phosphor-converted portion of the spectrum?
Not a problem. Phosphors generally do not have a problem being excited by shorter wavelengths. In fact, if you look at a phosphor excitation spectrum graph, the excitation efficiency typically decreases much more rapidly at increasing wavelengths than decreasing.
so as to more closely mimic the black body spectra at that point on the Planckian locust.
When it comes to higher color temperatures, I actually do not think mimicking the black body spectrum is what we should be aiming for.
Natural sunlight (after being attenuated through the atmosphere) does not have quite the same spectral distribution as a true blackbody curve, the violet and shorter blue wavelengths tend to get a truncated off to some degree, Rayleigh scattering being mathematically proportional to the
fourth power of the wavelength in question.
Many people say that they find higher color temperature artificial inside lighting to be too harsh, but I think a 4000K light source might be a lot more popular in people's homes if it more closely tried to approximate the spectrum (and color tint) of
natural light rather than a
true 4000K blackbody source.