| Author |
Message |
Lift-off
55mW Advanced Wicked Laser
Joined: 26 Aug 2005
Posts: 67
|
 Posted: 9/20/05, 2:36 PM Post subject: What Beam |
 |
|
Hi and thanks for reading,
Wicked Lasers are stated to have a beam divergence <1.5mrad.
Well, suppose it's =1.5mrad.
What's its definition exactly? I have 2 possible explainations and i'd like someone to confirm the first or the second:
1) Divergence=angle formed between the beam axis and one lateral conical front. This means that if divergence is 1.5mrad, we have a 1.5meters radius dot at 1000meters distance (3 meters diameter).
2) Divergence=angle formed between the two opposite lateral conical fronts, that is the same to say the cone vertex. This means that if the divergence is 1.5mrad, we have a 1.5meters diameter at 1000meters distance.
From my point of view, i think it's the second, but i need an official confirmation.
Thanks a lot.
Byyeee |
|
| Back to top |
|
 |
Steve0000
Wicked Lasers Master
Joined: 27 Aug 2005
Posts: 573
|
| Posted: 9/21/05, 9:33 PM Post subject: |
|
|
I don't understand what your saying but your math is right. It also means the beam diameter at 1000cm is 1.5 cm it also means the beam diverges 1.5 mm per meter of travel.
Before you asked did you look up the definition for beam divergence? |
|
| Back to top |
|
|
Athoul
Wicked Lasers God
Joined: 13 Sep 2005
Posts: 7544
Location: Canada
|
| Posted: 9/21/05, 10:24 PM Post subject: |
|
|
I think he wants to know if it's the radius or the diameter or the beam. Beam divergence is the diameter or width of the beam.
cheers, |
|
| Back to top |
|
|
Steve0000
Wicked Lasers Master
Joined: 27 Aug 2005
Posts: 573
|
| Posted: 9/22/05, 10:23 AM Post subject: |
|
|
Here's an answer.
"Beam Divergence
As a collimated laser beam propagates, the size of the beam increases. This rate of increase of beam size is called the beam divergence. Beam divergence is typically measured in milliradians (mrad). When making a comparison of beam divergence, it is important to specify whether the divergence stated is the 'half' or 'full' angle divergence. Half angle is a measure of the increase of the radius of the beam, wheras the full angle is a measure of the increase of the diameter.
e.g. a beam divergence of 1 mradian (full angle) is equivalent to a beam increasing by 1mm in diameter for every meter of propagation.
Beam Diameter
At any point along a laser beam, the width of the beam can be characterised. Most laser beams have a symmetric beam profile with the light intensity peaking in the centre of the beam and reducing with distance away from the centre. The beam diameter must be defined in terms of reference points on the intensity profile of the laser beam. Two common references are the 'half maximum' and '1/e^2' points.
In simple terms, the beam diameter is the spot size of the laser at any given point along the laser beam.e.g. the beam diameter could be expressed as the 'full width half maximum (FWHM)' i.e. whereby the beam diameter is defined as the separation of the points where the beam intensity has dropped to half of that in the centre of the beam.
Collimation
Collimation is a term used to characterise the divergence of a laser beam. A collimated laser beam will propagate with the lowest possible beam divergence for a given beam size. Physical laws limit the divergence specifications that can be achieved. Sophisticated telescopes are utilisied to optimise the collimation of a laser system" |
|
| Back to top |
|
|
|
|
