Side emmission of LEDs

[SMSAlmer]

I am considering building a bike light with MC-Es, and was thinking how much light is 'lost' out from the sides, for example at the junction between LED and lens.

Is it worthwhile to make a light which lets this light out to illuminate the surroundings (eg for better peripheral vision)?

 

[TooManyGizmos]

It won't have much throw out the front without a reflector.

Don't know how you can do both ?
.

 

[SMSAlmer]

What I mean is, if you have a reflector, or lens, how much side spill of light AT THE LED would you still have?

I.e. this light is not going in the optic.

 

[TooManyGizmos]

I'm not sure - I'll let someone else answer.

 

[Th232]

I think you'd probably have to tell us what kind of reflector, TIR or lens you're using, as they'll vary considerably. For reflectors and TIRs, look up the datasheet, that'll tell you how much light is emitted at what angle.

If you're looking at just a plain lens, you'll have to look up the emission pattern for the MCE, see how far you're placing the lens from the LED and then do some trig to get a rough approximation. Generally though, they'll have much less light out the front than a reflector or total internal reflection optic because of the gap between the LED and the lens, which reflectors and TIRs shouldn't have.

Edit: Re-reading your post, I might have mis-read the question. If you're asking how much light is emitted at around, say, 80-90 deg from "straight forward", my answer would be that reflectors will have none of it in that direction, since they completely enclose that area around the LED. TIRs should theoretically emit none, but will still emit some, check the datasheets for specifics. For a plain lens, see the previous paragraph.

 

[SMSAlmer]

Thanks for the replies. I think you got want I meant, but perhaps this explains things better:

The thing outlined in red is a model of a Ledil Eva, and the casing has the middle part made out of polycarbonate.

The idea is that most of the light will be projected forward, but there is still some spill to light up the near surrounding.

Please bear with me, newbie here!

 

[Th232]

Ahh, that makes things a fair bit clearer. I haven't played around with those optics so I can't comment on their efficiency. That said, I can point you to this thread on the Gatlight, which has a similarly exposed optic.

The design looks quite nice.:thumbsup: That Autodesk Inventor you're using?

 

[SMSAlmer]

Yes, it is...too much time on the computer!
Thanks for the link!

 

[taschenlampe]

http://www.ledil.fi/datasheets/DataSheet_Eva.pdf

As for reflectors:

Shallow and wide reflector => more sidespill, less throw
Deep and narrow reflector => less sidespill, more throw

tl

 

[Christexan]

There is "some" sidespill from those type optics, keeping in mind that you have around 90%+ efficiency from acrylic (typical rating) lenses, and of the rest, some of it is lost "in" the acrylic (absorption), the actual "spill" out of the lens is probably less than 5%.
Of that, (nice design, by the way), only a small fraction would have an incident angle allowing it to "exit" your side lens, maybe 1-2% of the total lumens, over a 360* dispersion, so not a lot. I'd recommend if doing something like this, to "frost" the lens (rough the exterior if acrylic) turning it more into a "marker" light than a transmission light, because not much will project out (and what does, would be a very faint "halo" on the surroundings, rather than a smooth flood lighting up the area).
Anyhow, just my $0.02, I've tested similar ideas in-house (a variety of lenses), and in all cases, it's best as a weak marker (or even "on-indicator" of sorts), rather than any useful area lighting.