LED technology

[Ketil B]

I wood think that its a lack of optc's in the lantern so the beam spreds more!

[NickLee]

I wood think that its a lack of optc's in the lantern so the beam spreds more!

Or - because LEDs are "point sources" much more than bulbs, much light dissapates around the LED itself - hence the need for some kind of focusing within the LED itself?

[tonymaslen]

As LED are not a point source, and emitt light they are impossible to to focus. placing a focusing lens would be tricky as currently the only way of producing enough light is to cluster LED together in groups.

[Ketil B]

what if you put the LED's in a mirrored box with a sem-mirrored panel a one end so the light becomes more parallel, like in a laser. somme one whit a better idea of optic's cud tell me if this wood work?

[Stig]

Putting a reflector round the led could work but you would have to do it to every led. This would then make the led clusters bigger thus reducing light output.

 

Good idea though. If they could incorperate the reflector in the led itself you may be on a winner.

[Guest lightnix]

LEDs come much closer to approximating a point source than postage stamp sized tungsten filaments. With most commercially available LEDs, the majority of the light is thrown out of the front and focussed by the "dome" of the LED, with very little light escaping out of the side. The beam angle is usually quite narrow (about 6-15°) although wider angle versions are fairly readily available. Some people do put reflectors around their LEDs to boost output, although the effect is minimal. There is "no need" for additional optics because they are already incorporated into the LED package. There is little point in building a reflector into the LED as hardly any light comes out of the back of one anyway.

 

This is surely one of the theoretical advantages of using LEDs in luminaire design - you don't need a reflector and can cut down on lenses, thereby saving on weight, space and cost. It is possible to cluster the light emitting chips into one package and there are some LEDs that do this, although they do need heatsinking to protect them from the effects of thermal runaway. I know at least one major manufacturer has patents relating to applying this idea to stage lighting technology.

 

All light falls off "very quickly", due to the inverse square law relating to the intensity of light over distance (double the distance from the source and get a quarter of the light intensity).

 

As I said before, it's early days for this technology and new developments are taking place all the time. My own vision is that in twenty years time there will be LED moving lights which are brighter than the discharge ones available today, with all colour, gobo, iris, and shutter functions handled by one "LCD" type plate. They will be a third of the size and one tenth of the weight. You'll easily be able to run a 100 head system from a 13A supply and the power / data distribution rack for such a system will take up the space currently occupied by a twelve way dimmer rack.

 

What that will do to crewing levels and the amount of work there is, is another story...

[James C]

What that will do to crewing levels and the amount of work there is, is another story...

Shouldn't make too much difference - there'll still be plenty of work to go round, as long as the ABTT are still reccommending 4 people at the bottom of each tallescope :D :D