5mm LED's?

[Mike, Lord of the Spammers!]

I was chatting Neil recently about the Infinity (shocking I know ) and he was saying that he just wasn't keen on the way that the LED cast a blue tinge

Now I know most 5mm LED's do the same, and while it doesn't bother me too much, I'd like to know why that is

So why (in relative simple terms, because I am ) do they have a blue tinge rather than pure white

Thanks in advance guy's n girls

[Screwtape]

Does this answer anything   

http://ledlightsathome.com/2007/12/07/a-lesson-in-color-temperature/

[Mike, Lord of the Spammers!]

Does this answer anything   

http://ledlightsathome.com/2007/12/07/a-lesson-in-color-temperature/

Perfect, thanks very much

Even I could get my head around that

[NutSAK]

That's a good article, but it's not the full story... 

Thing is, there's no such thing as a "white" LED.  The "white" LEDs in our torches (regardless of color temp) all start out life as a blue-emitting diode.  In the manufacturing process, yellow phosphor is added to the die to shift the spectrum of the LED toward white.  This is not only why some LEDs are bluer or some are yellower, depending on the amount of phosphor applied, but also why the die of the LED is yellow in color.  You are seeing the phosphor sitting on top of the die.

I can show you some white 5mm LEDs that are very blue or purple, and I can show you some that are quite yellow.

[Mike, Lord of the Spammers!]

Thanks for muddying the water's Terry

But i get you

[ringzero]

That's a good article, but it's not the full story... 

Thing is, there's no such thing as a "white" LED.  The "white" LEDs in our torches (regardless of color temp) all start out life as a blue-emitting diode.  In the manufacturing process, yellow phosphor is added to the die to shift the spectrum of the LED toward white.  This is not only why some LEDs are bluer or some are yellower, depending on the amount of phosphor applied, but also why the die of the LED is yellow in color.  You are seeing the phosphor sitting on top of the die.

I can show you some white 5mm LEDs that are very blue or purple, and I can show you some that are quite yellow.

Good explanation.

One minor quibble is that the phospor isn't really shifting the frequency of light from the blue LED.  Frequency shifting is an optical technique, but that's not what is happening here.

Rather the phosphor is absorbing photons emitted from the LED, then emitting photons at more desirable frequencies centered around yellow.

Small variations in the amount of phosphor applied and its distribution with respect to the LED will have big visible effects on the output.

.

[Mike, Lord of the Spammers!]

Just so you know I do understand how it works now (I'm really not that much of a thicky )

But I had no idea it was such an involved process

[John]

This is all very interesting  but remember you can have the following tint variants:


White
green(yucky)
yellow
blue
pinkish
red
brownish

and one of my favourites ANGRY BLUE  any led can be tint shifted to blue if over driven 

[NutSAK]

That's a good article, but it's not the full story... 

Thing is, there's no such thing as a "white" LED.  The "white" LEDs in our torches (regardless of color temp) all start out life as a blue-emitting diode.  In the manufacturing process, yellow phosphor is added to the die to shift the spectrum of the LED toward white.  This is not only why some LEDs are bluer or some are yellower, depending on the amount of phosphor applied, but also why the die of the LED is yellow in color.  You are seeing the phosphor sitting on top of the die.

I can show you some white 5mm LEDs that are very blue or purple, and I can show you some that are quite yellow.

Good explanation.

One minor quibble is that the phospor isn't really shifting the frequency of light from the blue LED.  Frequency shifting is an optical technique, but that's not what is happening here.

Rather the phosphor is absorbing photons emitted from the LED, then emitting photons at more desirable frequencies centered around yellow.

Small variations in the amount of phosphor applied and its distribution with respect to the LED will have big visible effects on the output.

.

Thanks RZ.  I did not know that. 

..and it make a lot of sense.

[NutSAK]

This is all very interesting  but remember you can have the following tint variants:


White
green(yucky)
yellow
blue
pinkish
red
brownish

and one of my favourites ANGRY BLUE  any led can be tint shifted to blue if over driven 

I've seen variation of all of those too.

It should also be mentioned that, although this thread is specifically about 5mm LEDs, these tint variations can occur with all types.  Blue and purple are the tints most frequently seen from the Nichia 5mm LEDs in lights such as the Gerber UI, ARC AAA-P and Fenix E01.  I'm not sure why the Nichias in particular are manufactured that way.  There are "snow" white 5mm LEDs available from other sources.