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ArcticMyst Security by Avery

how to... reduce the mRAD of a laser?

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need a smaller mrad, a better collimation. is there lens that can do this for me? for sell? :p
 





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thanks for translating! i'm not english.
so, is this that i'm looking for, but it is very expensive and will be hard to fit one of these in a aixiz module.
maybe someone at the LPF could machine one look alike with 445nm and sell cheaper than 80 bucks? :S they would sell very well in here...
thanks :)
 

udanis

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Well you are looking for precision optics. Anything thing with "precision" in it's name is going to be expensive.

So you want a custom beam expander (well reducer in this case) for less than $80?
good_luck-2691.gif
 
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Well you are looking for precision optics. Anything thing with "precision" in it's name is going to be expensive.

So you want a custom beam expander (well reducer in this case) for less than $80?
Hi udanis,
No he doesn't need a beam reducer, it's a beam expander. The beam expander will expand ie increase the beam diameter, but also reduce divergence by the same X factor.
 

udanis

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Hi udanis,
No he doesn't need a beam reducer, it's a beam expander. The beam expander will expand ie increase the beam diameter, but also reduce divergence by the same X factor.

Okay beam expander to reduce the diameter of the beam :p
 
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yeah, I think a custom beam expander that fits an aixiz module cheaper than 80 bucks.
well.. if it is more expensive than 50 bucks i'll only buy it on december. lol
 
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Okay beam expander to reduce the diameter of the beam :p
Hi udanis,
No, a beam expander increases the diameter of the beam, while at the same time reduces the divergence.

Divergence is how much the beam spreads out and it's inversely proportional to the diameter of the beam.
 

udanis

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Hi udanis,
No, a beam expander increases the diameter of the beam, while at the same time reduces the divergence.

Divergence is how much the beam spreads out and it's inversely proportional to the diameter of the beam.

Oops my bad. Should of googled that a bit more :thinking::thinking::thinking:
 
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How come beam expanders aren't being used on the majority of the lasers here on LPF? I mean if they work on most lasers, it would be very useful in order to reduce the laser's divergence especially in the case of 445 nm lasers such as the spartan, on which the dragon lasers' beam expander can be installed.
 

udanis

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because most people don't want a larger beam to gain better divergence. I think....bootleg2go?
 
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It depends on the application.

For example, lets assume a 1.5mrad beam with 3mm diameter at aperture. At 10 meters the dot/beam will be 15mm in diameter. At 100 meters the dot/beam will be 150mm in diameter.

Now put that same laser through a 10X expander and you will have a 30mm beam at aperture with only 0.15mrad divergence. So at 10 meters the dot/beam will be 31.5mm in diameter. But @ 100 meters the dot/beam will be 45mm in diameter... less than HALF the size of the unmodified laser beam. This means energy density and intensity are MUCH greater at longer distances.

There's a balance point for deciding if a beam expander is helping or hurting your beam charactaristics. In the above example, the distance is 20 meters. At 20 meters, the beams above would project the same dot size. Less than 20 meters and the unmodified beam would project a tighter beam/dot. Greater than 20 meters and the "expanded" beam would project a tighter beam/dot.

The reason most people don't bother with beam expanders is the expense and lack of need to point at "long distances". Most people here are calibrating projectors for certain distances, using laser pointers at room distances, or burning things. How many people here really care about beam profile & dot further than we can accurately perceive it or burning at long distances?

This is an illustratoin of what I'm talking about (regular beam vs 10X expanded beam):
|x|= intersection point in meters
Theta = milliradians
D = aperture diameter in millimeters

d763983d.jpg
 
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JLSE

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Great explanation, this would be an answer given from experience
and not regurgitation of a google result...



+1 :beer:




It depends on the application.

For example, lets assume a 1.5mrad beam with 3mm diameter at aperture. At 10 meters the dot/beam will be 15mm in diameter. At 100 meters the dot/beam will be 150mm in diameter.

Now put that same laser through a 10X expander and you will have a 30mm beam at aperture with only 0.15mrad divergence. So at 10 meters the dot/beam will be 31.5mm in diameter. But @ 100 meters the dot/beam will be 45mm in diameter... less than HALF the size of the unmodified laser beam. This means energy density and intensity are MUCH greater at longer distances.

There's a balance point for deciding if a beam expander is helping or hurting your beam charactaristics. In the above example, the distance is 20 meters. At 20 meters, the beams above would project the same dot size. Less than 20 meters and the unmodified beam would project a tighter beam/dot. Greater than 20 meters and the "expanded" beam would project a tighter beam/dot.

The reason most people don't bother with beam expanders is the expense and lack of need to point at "long distances". Most people here are calibrating projectors for certain distances, using laser pointers at room distances, or burning things. How many people here really care about beam profile & dot further than we can accurately perceive it or burning at long distances?

This is an illustratoin of what I'm talking about (regular beam vs 10X expanded beam):

d763983d.jpg
 
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I wish this forum suported TeX

z_0 is called the Rayleigh range and is an intrinsic property of a laser. It tells you the distance the beam will travel from the location of the beam waist (the narrowest part of the beam) before the width of the beam will be Sqrt(2) or 1.414 times the width at the waist.
Alternatively you can think of the Rayleigh range as the distance the beam will travel from the location of the beam waist before the cross sectional area of the beam is 2x (not Sqrt(2)) the cross sectional area at the beam waist.

More in depth here because I can't write neat looking equations here Rayleigh length - Wikipedia, the free encyclopedia
Basically you want to use a short wavelength (blue is good so you don't need to worry about that) and a large beam waist. So like people said, get or make a beam expander.

I wouldn't worry about it unless you intend to point down the street with little divergence, or measure the distance to the moon :p

That said, I'd like a wide ish beam too. probably 5mm in width. Too bad I can't make it a clean Gaussian without some seriously expensive equipment lol.
 

IsaacT

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that Dragon lasers Beam Expander says that

Dragonlasers said:
The beam expander can be connected to our Viper, Aurora and Spartan Series lasers using optional adapters.

Are there any companies that manufacture beam expanders for a custom size? Or do you have to get a tripod or two or set up an optics table if you don't have one of "their" lasers?
 

Blord

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Hi udanis,

Divergence is how much the beam spreads out and it's inversely proportional to the diameter of the beam.

This is true in real world. I have a green laser with a thick beam at the output, 5/6mm I think, but it is the only laser that can project a bright dot in the clouds. The ones with much smaller beams around 1mm never did this no matter how good I collimate it.
 




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