White Luxeon Colors
The following is only my observations, and may be totally incorrect; I leave that for the reader to decide and comment on in the candlepowerforums.
I will try to explain the different colors (tints) of white Luxeon emitters, and how they are used impacts the final results.
I have used basically three groups of white Luxeons, pink/violet, blue/green, and pea green is how I characterize them. My observations are:
The blue/green seem to be the brightest overal, producing more light at any given current.
The pink/violet seem to be almost as bright as the blue/green, producing slightly less light at any given current - the small difference may be just my eyes responses to the color temperature difference.
The pea green produce less light than the other two at any given current.
When used with a flashlight reflector:
The pink/violet in a flaslight reflector produce a bright violet corona, and a slightly pink tinted spot.
The blue/green in a flashlight reflector produce a bright moonlight blue corona, and a bright pure white spot with slight green halo.
The pea green in a flashlight reflector produce a light colored pea green corona, and a light pea green tinted spot.
When using the Luxeon optics, things look completely different:
The pink/violet produce a bright white/violet center beam, with a slightly pink corona.
The blue/green produce a bright blue center beam, with a light pea green corona.
The pea green produce a less bright blue center beam, with a pea green corona.
I believe the pink/violet Luxeons use a different phosphor mix than the other two; with the only difference between the blue/green and pea green being the thickness of the phosphor coating.
The different results with reflectors and lenses has to do with the Luxeon’s design. It is a square blue LED chip, with a round phosphor cap. More ‘green light’ is produced at the edges of the Luxeon by the phosphor, and more ‘blue light’ is produced in the center of the chip from the underlying blue LED shinning through the phosphor coating.
Due to the ‘batwing’ emission pattern of the Luxeon, the brightest part of the light emitted comes from the phosphor at the edges of the chip (green tinted). The amount of blue tinted light (and overall light output) produced is directly proportional to the thickness of the phosphor coating; the thicker the phosphor coating, the less blue light is emitted, and less total light emitted. Thicker phosphor becomes self absorbing, blocking some of the light produced by both itself and the LED chip.
Luxeon beam shaping:
As Barbarian and others have noticed, when using the Luxeon optics, some light is wasted out the sides (green tinted). The lens is really an optical light pipe which ‘pipes’ the light straight up, projecting the ‘blue’ from the LED chip in the middle of the beam, and the ‘green’ from the chip edges as the corona.
When used with a flashlight reflector, the brightest part of the light output from the edge (green tinted) is focused by the reflector into a spot. The blue light from the center of the chip forms the corona.
Somewhere in between the Luxeon lens and flashlight reflector lays the perfect Luxeon optics.
I have made some photos of pink/violet, blue/green and pea green Luxeon beams with reflector and optics they show this effect fairly well. I will post them for reference with this document at http://lambda10.tripod.com/
Does this make any sense?
Now, if Lumileds would only sort by color or phosphor type or thickness........................