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'[EE]:: Batwing LED radiation pattern - why does it'
2008\01\27@214601 by Apptech

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The "Batwing" LED radiation pattern has lobes either side of
centre with increasing light intensity with angle, up to a
limit, whereafter it falls off sharply.

I find this light distribution pattern extremely useful for
certain applications, and it is not uncommon for lens makers
to make lenses which provide a tight beam, using this
pattern as input. But, it is inobvious what the motivation
was for designing this pattern initially.

Can anyone provide an authoritative comment on this or,
failing that, hazard any half likely guesses.


           Russell

2008\01\28@072900 by Dave Tweed

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Apptech <spam_OUTapptechTakeThisOuTspamparadise.net.nz> wrote:
> The "Batwing" LED radiation pattern has lobes either side of centre with
> increasing light intensity with angle, up to a limit, whereafter it falls
> off sharply.
>
> I find this light distribution pattern extremely useful for certain
> applications, and it is not uncommon for lens makers to make lenses which
> provide a tight beam, using this pattern as input. But, it is inobvious
> what the motivation was for designing this pattern initially.
>
> Can anyone provide an authoritative comment on this or, failing that,
> hazard any half likely guesses.

Even illumination of a flat surface -- in particular, backlighting?

I seem to recall that bare LED chips prefer to emit light from their edges
anyway, so creating a reflective cup in which to mount them that fine-tunes
this pattern is probably relatively easy.

-- Dave Tweed

2008\01\28@082241 by Apptech

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>> Can anyone provide an authoritative comment on this or,
>> failing that,
>> hazard any half likely guesses.

> Even illumination of a flat surface -- in particular,
> backlighting?

Is that an authoritative comment or a half likely guess :-)

FWIW, my prognostications suggest that for my application a
1/COS^3 wrt angle from centre response is desirable.

Plotting that against Batwing out to around say 60 degrees
gives a suspiciously similar if not identical result :-).



       Russell

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