Led laser?

[GatoX]

Hi everyone, recently I have an idea.

The idea is put a 5mm Led in a 5.6mm module with lenses. That's going to make a cheap but dirty blue "Laser". What do you think?

Thanks

 

[oahu99]

It won't work
The short answer is that led lights are not coherent like laser diodes, and thus couldn't create a laser.

http://en.m.wikipedia.org/wiki/Coherence_(physics)

 

[zyxwv99]

A basic laser is usually something that emits light, then two mirrors so that the light can bounce back and forth. The mirrors have to be perfectly flat and perfectly aligned. A central spot in one of the mirrors is only half silvered and lets some of the light out. The light-emitting material has to be capable of being strongly influenced to emit photons in the same direction that the other photons are going. It' s something like a guitar, where the strings make a faint sound but the wooden box part makes the sound waves resonate. At least that's the version I learned as a kid.

 

[GatoX]

A laser no, but a spot how lasers? Is going to be very ugly, but can be good experiment. Or a RGB spot from a RGB led

 

[ChaosLord]

That's called a focusable flashlight. That's pretty much what you would be making.

 

[BShanahan14rulz]

The goal is to use as big of a lens as you can without having the focal length be so large that it doesn't collect light from the LED. The smaller the optical source is, relative to the size of the lens, the more control you will have over where the light from that source goes.

You will notice that the LED already has a "lens" built-in to the clear plastic. As you can see, a lens this small is not able to focus the light into a laser-like beam because the source is quite large, relative to the lens.

 

[KrowBar]

If you use a very large and high quality lens, you could at best focus the light from the LED to a spot no smaller than about twice the size of the LED itself at a moderate distance of say 1m (and that would require this huge lens to be located about halfway to the target). With a smaller lens on the order of what we usually use for lasers or even flashlights, you are looking at best case of a spot diameter of at least 50 times that of the LED at 1m away. There is a reason that lasers are used for laser pointers.... The effective emitter size of the LED is so large compared to a laser that you can never get good divergence because of diffraction limitations even assuming everything else is "perfect".

 

[GatoX]

I have seen this project, and I think that I'm going to make a similar but with a dot instead a arrow