Size of a focused spot

[Cyparagon]

When focusing a "beam" on the other hand, the source element is irrelevant.

Ever tried getting a beam from a fluorescent tube? If you have, you'd know this is utter bullsht.

 

[KreAture]

Ever tried getting a beam from a fluorescent tube? If you have, you'd know this is utter bullsht.

Can't you read?
I am talking about focusing a beam, and creating a single spot.
Not creating a beam from a emissive element.

Assuming you have a very wide element like a tube you will get a beam that has an odd shape, that's true, and your spot will also have a asymetric shape. However, the size of the lenses and original beam diameter determine the actual size of the spot. You run into other optical issues and at large enough lenses and focual ranges you even get rayleigh-scattering, but the formulas are simple and the actual emissive element size is not part of them.

No industrial lasercutter would ever dream of using those crappy 3-6mm dia lenses used in these toys we build here.

 

[BShanahan14rulz]

How come we use laser diodes? Why not LEDs? And how come you can focus lasers down to a spot and not LEDs?

 

[Cyparagon]

Can't you read?
I am talking about focusing a beam, and creating a single spot.
Not creating a beam from a emissive element.

They're pretty much the same thing anyway. If you focus the output from a fluorescent lamp, you cannot get anything you'd call a spot. You only get an image of the lamp.

 

[KreAture]

They're pretty much the same thing anyway. If you focus the output from a fluorescent lamp, you cannot get anything you'd call a spot. You only get an image of the lamp.

You ned to collminate it first. If you don't all you do is project a picture of the lamp.

Focusing and Collimating
If you ignore wave optics and look at the ray optics you have your claim that you cannot get a smaller dot than the emissive element mentioned, and it's wrong. You can, but it will be limited by divergence and practical physics in lenses. You can however expand the beam to make it focus to a smaller point, or use a larger lense.

 

[Cyparagon]

I am talking about focusing a beam, and creating a single spot.
Not creating a beam from a emissive element.

You ned to collminate it first.

 

[BShanahan14rulz]

btw, I never focus my lasers to beams. Instead, I focus to projection for a suitably long distance. It's easier for me.

 

[Living Laser]

How come we use laser diodes? Why not LEDs? And how come you can focus lasers down to a spot and not LEDs?

^
Well from what I know LEDs, the same in flashlights will generate the light but not the heat. There are LED lasers out there with a variety of WL.


In Manufacturing Circuit board they often use 1 CO2 Laser (dont know exact power) and split the beam into alot of individual beams in the form of a Stensile and the beams are focused into fractions of microns (Depends on Circuit Board).

If your asking what is the minimum beam diameter possible and what would power be relative to as if a 10mm 50mW laser condensed into Microns smaller than a hair, the power stays the same put the density of it is increased. Possibly it can be relative to a 500mW -/+ if burning a e.g. Wood and see it burns at the same rate but different radius.

I have not tested any of this nor researched so I may not be accurate.