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Real focusing adapter

Moe Ron

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Greetings,

Have a question that will show me as the noob that I am; Why hasn't someone fabricated a actual focusing adapter ? A beam expander will allow some focus capability as long as you do not want to focus any further then a foot or 2. To really have a focus capability as I understand it would take 2 lenses seperated by a distance and the ability to move one lens closer or further from the other.
There must be a reason like it would kill the laser's power or cause some type of feedback back into the laser. Seems like if there is a way to focus your laser at 100' away someone would have already made such a device. Unless of course the power is less than that to be warm to the skin let alone light a match.

Moe Ron
 

rhd

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What I don't understand, is why nobody has made a beam expander with a female M9x0.5 thread on the input end.

Seems like a no-brainer to me. Attach it to the focus-knob-end of your three element glass lens. Would work with 99% of builds.
 

justinjja

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I have a custom beam expander on my 635nm laser.
But the divergence is bad on these diodes
it is still only about as good as say a 445 with a regular lens LOL.
 

Ozzy357

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What I don't understand, is why nobody has made a beam expander with a female M9x0.5 thread on the input end.

Seems like a no-brainer to me. Attach it to the focus-knob-end of your three element glass lens. Would work with 99% of builds.
 

DrSid

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Any single lens will allow you to focus to any distance, as long as the lens can be moved. Most custom builds, and most high-power builds do have such lens.
Problem is, that there is limit to how small the spot can be at the distance. With small aperture, you simply cannot focus the beam into pinhead over 100m for example. Diffraction prevents that. That's why beam expanders are made. Spot size is limited by wavelength and aperture size. Shorter wavelength and bigger aperture size makes smaller dot. If you have beam expander which increases the aperture 10 times, the dot will be 10 times smaller at any distance. Of course any additional optics will absorb some power. Also such optics would be large - thus expansive.
 

Moe Ron

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Greetings,

Thanks for all the explanations on how and why there are no real focusing adapters. I was thinking it would need to be something similar to a expensive zoom type lens for a camera. Still, regardless of expense I cannot understand why no one has made something that would at least focus 40' to 50' away and be able to pop a black balloon !

Again, thanks for the schooling,

Moe
 

DrSid

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I've seen video where someone used green laser of unspecified power and astronomic telescope to light firecracker over 100m or so.
 




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