Why don't they make LEDs like this?

[Kirk]

Why don\'t they make LEDs like this?

I have wondered for a while why LED manufacturers don't make some LEDs with the die facing "down" towards the leads. This way you could use a wide angle LED with a focusing flashlight. Is this feasible or would the LED heat up too much from lack of heat-sinking? Or, even better how about a chunk of the light-emitting stuff just stuck on the end of the lead inside the epoxy with no "focusing" die. This way the light would be emitted 360 degrees, just like a regular incandescent.
Kirk

 

[EMPOWERTORCH]

Re: Why don\'t they make LEDs like this?

Ideally the emitting surface of the LED (or any light source) should be cylindrical and mounted at the centre axially (like some LNB's on early satellite reciever dishes). I found out the difference was marked when I replaced a radially mounted filament bulb in my motorbike's spotlight with an axially mounted filament bulb. The beam produced by the axial filament bulb was a very fine "pencil" beam rather like a well focussed maglite torch beam but 100's of times brighter of course!!!
Radial filaments gave me a very much more diffused beam. I actuaslly prefer the diffused beam for motorcycling.
Coming back to torches... most filaments in PR torch bulbs are mounted radially, so some diffusion of the beam is bound to happen anyway!

 

[PlayboyJoeShmoe]

Re: Why don\'t they make LEDs like this?

If I understand the terms "radially" and "Axially" I may need to disagree.

I don't know of any bulb I've EVER seen that meets what I think Radially means. All bulbs I know of have a straight filiment (more or less) across two posts.

Enlighten me please?

 

[Kirk]

Re: Why don\'t they make LEDs like this?

I think radially means the filament runs "sideways" if looking down or into the bulb when mounted in a flashlight; in other words, shining into your face. Axially means the filament is mounted longways in the bulb and you'd see it as just a wire or a coiled "tube" if shining the light in your face. Radial filaments use the typical "Y"-shaped filament holder. Axial filaments have one end of the filament connected close to the base of the bulb, with the other filament holder looking sorta like a question mark and coming around the top.
Kirk

 

[RonM]

Re: Why don\'t they make LEDs like this?

An ideal light source would produce light from a single point. That would make it much easier to design lenses and reflectors for. Axial filaments are a compromise, but much better in terms of lens and reflector design, than radial filaments. If you think about it, its almost impossible to properly focus a radial filament.

Bringing this back to LEDs. There are LEDs that have cylindrical sides and concave top that send much of their light out sideways so they can make use of a focusing reflector.