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Thread: will fatter beam change beam throw distance?

  1. #1
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    Default will fatter beam change beam throw distance?

    lets say same divergence and wavelength, but the 2nd beam is twice the diameter and power higher accordingly.
    Will the 2nd beams throw distance be more than the first?
    I think no. It's the same amount of photons shot for each cubic mm, just more cubic mms. Am i wrong?

  2. #2
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    Sir blue, you've already answered your own question: Divergence is Divergence.

    If you're talking 'perceived brightness' at a given distance, due to the differentials you've spec'd well.. That's a different question / discussion.

    j
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  3. #3
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    Will the 2nd beams throw distance be more than the first?
    Throw distance is not a commonly used term and so it might be that what you are thinking is not what someone else is thinking. But consider this. If the second beam was 10 times the diameter and 100 times the power it is unlikely by any conceivable definition that it will not be more visible, impressive, dangerous and expensive to generate.

  4. #4
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    "Throw" is a term used in flashlight forums. For a laser, it would be visibility distance. The larger the beam diameter, the less visible it is at the equivalent power. For twice the diameter, you would need 4 times the output power to have equivalent brightness. This is all considering that the divergence is exactly the same for both beams.

  5. #5
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    Quote Originally Posted by steve-o View Post
    For twice the diameter, you would need 4 times the output power to have equivalent brightness. This is all considering that the divergence is exactly the same for both beams.
    Thanks all.
    Now say you have 4 times the output power and twice the diameter (and same divergence). Will visibility distance be the same?
    On one side I want to say yes because for each cubic mm the power and so the brightness is the same. But on the other hand even if they dim at the same distance the second beam is bigger so might be more noticeable to the human eye when dimmed. I hope I'm making sense

  6. #6
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    Blue,
    I answered exactly that question above in post # 3. What did you think I meant?

  7. #7
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    Oh, sorry planters.
    I misunderstood. I didn't know when you said brighter you also meant the visibility distance will change, just that the second beam would appear brighter in the visibility range of the 1st beam.

  8. #8
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    ... what's with changing the beam divergence and farfield 'visibility' with a beam-expander and better focussing?

    Viktor

  9. #9
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    You mean whats wrong with changing the beam divergence to increase visibility distance?
    Well I'm just beginning to learn the internals of lasers and stuff, but as far as I know you can't get 0 divergence and even if the beam can be focused better, unless in a vacuum the particles in the air/fog/haze are the reason you see the beam but are also the reason the beam gets dimmer over distance, it's not only caused by divergence so I guess only improving divergence without increasing power and/or beam diameter won't be a solution for getting longer visibility distance.

  10. #10
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    ... it's all related to energy density in a volume -- or here, more specific, in the beam diameter in a specific distance.

    If you only want a 'visible beam', then you can work with fog or play with the laser in the morning, when the air is misty ... if it's more the distance, in which the beam should be visible from your starting position, then you can expand the beam to a maximum (with lesser to no 'visibility') and try to focus it in a distance, where it would have more energy density and so would be better visible.

    All other aspects are related to shear power, initial beam diameter and 'beam quality' or divergence over distance ...

    Viktor

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