LED color quality and purity Q's

[Canuke]

LED color quality and purity Q\'s

While I was at the local Party City with my girlfriend picking up some items, I ran across one of those cheap doodads with 10 LED's in it, that spins around inside a sphere to create patterns. In addition to red/yellow LED's, most had 470nm blue ones at the "equator". All but one, that is, that instead had a much lighter blue, tending towards the green -- but definitely still blue, not "traffic light green".

My first question is: why don't I see this color more often? I find that I like it a lot more than the 470nm blue. I'm thinking of finding some to substitute for regular blue in a number of places, in particular computer parts with LED's in them.

My second question is: how much variation in color purity is there in LED's? I ask this question because of the idea of obtaining the above color via color mixing. I've noticed with green LED's in particular, that there's a fair bit of yellow and blue alongside the green, and this seems to wash out blue-to-green mixing. What are the options for applications that demand very pure colors -- other than lasers? Filtration?

 

[idleprocess]

Re: LED color quality and purity Q\'s

In the case of the gadget you saw, I think you already answered your own question:
[ QUOTE ]
I ran across one of those cheap doodads with 10 LED's in it

[/ QUOTE ]

Odds are they weren't too tight on their specifying, and their suppliers were more interested in cutting their costs...

Monochromatic LEDs are typically good about holding to a specified dominant wavelength and are fairly tight on the spectrum they emit - usually better than filtering a broadband light source.

 

[Canuke]

Re: LED color quality and purity Q\'s

[ QUOTE ]
idleprocess said:Odds are they weren't too tight on their specifying, and their suppliers were more interested in cutting their costs...

[/ QUOTE ]

Right... that would mean they just took whatever they could get for cheap. I'd like to know whether anybody supplies this color on purpose.

IIRC, the color I mean is what was called "Tokyo blue", and it's hard to find now because all the manufacturers are trying to hit "traffic light green" instead. In three years I've only seen it three times: in a nifty Apple G5 acrylic pendant, in one case fan at Fry's, and now in this thing. /ubbthreads/images/graemlins/frown.gif

 

[idleprocess]

Re: LED color quality and purity Q\'s

"Tokyo blue" might be easy to get in Japan - their traffic signals use that color (aside: I hear "blue" and "green" are often synonymous to the Japanese).

I'm not sure, but that color might have been a stepping stone on the way to "true" blue LEDs.

 

[The_LED_Museum]

Re: LED color quality and purity Q\'s

"Tokyo Blue" has fairly long ago since been phased out in favour of "traffic signal green", so I would expect that color of LED to be very, very, very difficult to find, as manufacturers don't make that color on purpose anymore.

From my website, comes the following text:
A fan of the website - someone who's work I trust - emailed me last night (11-04-03) with additional info regarding this and other blue-green LEDs. I don't have room on the server to put his whole email here, but the crux of the matter is that manufacturers of blue-green LEDs are trying to produce these on the greener side of blue-green, rather than having them greener by accident. The older style "Tokyo blue" (490-500nm) blue-green LEDs are less favoured by traffic light manufacturers than these more greenish (505-510nm) models. These greener LEDs emit closer to the photopic peak of human vision than the older bluish versions do, so that green traffic signals made with these LEDs are more easily visible. Yet they'll still emit enough blue to be visible to somebody with red/green color blindness.

 

[Canuke]

Re: LED color quality and purity Q\'s

That's what I was afraid of. Figures.. of all the single-wavelength LED colors, this is the one I like best. Reg, green and blue are common as dirt, as are amber and violet.

Oh well, I found a nifty case mod called the Chameleon, which comes with four RGB LED's and a control panel with pots for the three colors. I'll probably just dial up the color I want that way.

I'm thinking of building my next workstation in an acrylic case like you see here, but with a frosted surface instead of see-through (not sure yet how I plan to achieve that). The idea is that it will look like a block of ice.