We've discussed the need for someone to come up with an inexpensive way to drive LEDs from the power line before (We Need Cheap LED Drivers). And to make them dimmable. Smoothly and reliably. And be inexpensive and make things look right.
If you read the blogs on All LED Lighting regularly, you know that the important issue regarding these (or any) light sources has to do with color temperature and color rendering/CRI. What color is the light, and how does it make stuff look compared to some ideal source?
It's quite straightforward to make an LED lamp with three-color emitters. Then by adjusting the drive current, you can get the full color spectrum. But this adjustment becomes completely arbitrary unless there is some attached calibration device or method.
To tell what the color temperature is, we need an integrated three-color measurement system on a chip (SoC). Making phototransistors or photodiodes is nothing new — they are readily available. All that's needed is a closed loop system to produce a very tight tolerance accuracy spec. Oh — and three separate, good-quality color filters.
Put all this on a chip and — voilà! — you can accurately produce a light source that's the right color. This will address concerns regarding the color temperature of the light source in general. More importantly, it will permit continuous adjustments: As the LEDs age, their output drops. To deal with these age-related variations, you can tweak the drive current based on a control signal (well, actually three control signals) from this color temperature controller IC.
Note that the issue of the CRI is not completely addressed by this solution. But it is a good starting place.
Have you worked on the issues of color temperature and CRI? What solutions did you come up with?