LED colour patterns

I'm finding that using a collimator as opposed to aspherics produces a far better tint to the output light. After having a look at the light pattern from the unfocused LED it appears that the LED light is bluish towards the center, and gets lower in colour temp closer further and further from the centre.

From this I conclude that the improved colour tint from collimator lenses is due to the fact that the light is "mixed" from the whole of the LED output, whereas as ashperic lenses placed in front of the LED collect light primarily from the centre of the output and miss the low K light far to the sides.

The comparisons that I've done were made using the DX parts:
http://www.dealextreme.com/details.dx/sku.1920
http://www.dealextreme.com/details.dx/sku.13903
Both of those perform very well as far as optics go, and are excellenetly priced.

Does this sound like a reasonable hypothesis? If so, is there a way to combine the all-collecting properties of a colimator with the throwing power of an aspheric? Is it possible to get a collimator to perform as well as an aspheric, or evennearly as well, without being overly large?

MrNaz said:

From this I conclude that the improved colour tint from collimator lenses is due to the fact that the light is "mixed" from the whole of the LED output, whereas as ashperic lenses placed in front of the LED collect light primarily from the centre of the output and miss the low K light far to the sides.


Does this sound like a reasonable hypothesis? If so, is there a way to combine the all-collecting properties of a colimator with the throwing power of an aspheric? Is it possible to get a collimator to perform as well as an aspheric, or evennearly as well, without being overly large?

Click to expand...

You are on the right track. The reason it is more yellow to the sides where it would hit a reflector is due to the fact that the phosphor layer over the die is has thickness to it. The light that travels to the sides goes through more phosphor than if it went straight out.

A TIR optic combines both the qualities of a reflector and the collimating of a lens in one unit. That may be what you are looking for.

saabluster said:

You are on the right track. The reason it is more yellow to the sides where it would hit a reflector is due to the fact that the phosphor layer over the die is has thickness to it. The light that travels to the sides goes through more phosphor than if it went straight out.

A TIR optic combines both the qualities of a reflector and the collimating of a lens in one unit. That may be what you are looking for.

Click to expand...

Great! Any idea where I can get good TIR optics from ?