Visibility vs distance

[Dridapada]

I have compared the beam diameters of two high range lasers(see pic)
Assuming zero lumen drop , see the lux levels at different distances.

Clearly , the LD - low divergence of .5 mrad is having twice the range .

This exercise was an attempt to find our the visibility of white beam.

Assuming the factors such as light pollution, environmental factors are all considered to be favourable to have long visibility.

I m new to the forum..Please need your help

https://drive.google.com/file/d/17dgfJ9B_UQWuYIUcDhJoVdM5dKu0m7OT/view?usp=sharing

 

[Dridapada]

Any one out here in LPF who can help me out?

 

[lasersbee]

I have compared the beam diameters of two high range lasers(see pic)
Assuming zero lumen drop , see the lux levels at different distances.

Clearly , the LD - low divergence of .5 mrad is having twice the range .

This exercise was an attempt to find our the visibility of white beam.

Assuming the factors such as light pollution, environmental factors are all considered to be favourable to have long visibility.

I m new to the forum..Please need your help

https://drive.google.com/file/d/17dgfJ9B_UQWuYIUcDhJoVdM5dKu0m7OT/view?usp=sharing

1) What is a 'high range laser ??
2) You haven't given the power of the Lasers
3) You haven't given the wavelength of the Lasers
4) What exactly is a 'Favorable environmental factor ??
5) As to 'long visibility' do you want to see the beam
for a long time or do you want to see the beam from
the transmitting point for a long distance ??
6) what is the purpose of this project ??


Bad info in = no info out.


Jerry

 

[steve001]

1) What is a 'high range laser ??
2) You haven't given the power of the Lasers
3) You haven't given the wavelength of the Lasers
4) What exactly is a 'Favorable environmental factor ??
5) As to 'long visibility' do you want to see the beam
6) what is the purpose of this project ??

a for a long time or do you want to see the beam from
the transmitting point for a long distance ??

Bad info in = no info out.


Jerry

On top of all that theý want to know the visibility of a white beam.

 

[Alaskan]

This guy might be sincere, but too many newbies showing up with all of these random questions lately to challenge us, me thinks.

 

[steve001]

This guy might be sincere, but too many newbies showing up with all of these random questions lately to challenge us, me thinks.

I think they are, but have not communicated their goal clearly. One thing I've wondered for a longtime is how would the apparent brightness of a white laser compare to a 532 nm laser? All things being equal of course.

 

[Alaskan]

That's something I hadn't considered before, but considering more cones are being used for white than a single color, hmmm.... maybe more sensitive? Very interesting question.

 

[Dridapada]

Sorry about the lack of detailed specs in my query..
The guaranteed power is 29 W
Red - 637nm - 8000mW
Green - 520 nm - 10000 mW
Blue - 460+445nm -11000 mW (not sure of the power split up between the two blues)

The purpose of this project is
1. Create a "Pillar of Light"
2. And to provide a aerial mark to our location

 

[Dridapada]

http://www.kguttag.com/2011/12/16/diode-green-lasers-part-1-wavelength-and-efficiency/

I referred the above link for checking the lux level of laser beam at various distances (attachment in first query)

But unsure if these values hold true for Green- OPSL + Blue & Red - DPSS

Will the beam be visible from 30 km away?
I came to know that favorable environmental factors such as high humidity / dew /mist in the air will amplify the brightness to a viewer.

 

[Alaskan]

30 miles away is beyond the curvature of the earth, unless on a high tower or mountain top. What is the divergence for each wavelength? At that power, 30 miles isn't nothing, unless the outputs diverge a whole lot.

 

[diachi]

30 miles away is beyond the curvature of the earth, unless on a high tower or mountain top. What is the divergence for each wavelength? At that power, 30 miles isn't nothing, unless the outputs diverge a whole lot.

Curvature? What curvature? That's just what they want you to believe!

:crackup:

 

[Alaskan]

Flat earth? When I flew from Anchorage, Alaska to Dubai, UAE, the jet didn't need to turn around at the edge of a flat plane of earth, go upside down and then fly to theDubai, it can't be flat.

 

[Dridapada]

The visibility needed is only 19 miles (30km)
Back to my original question- would a 10 w green opsl be more visible than a 29 W white ?

Beam diameter is 5.5 x 6mm at source and beam divergence is 1 mrad (a full angle)

 

[Alaskan]

oops, km... 1 mRad, no problem line of sight in normal clear smog free atmosphere. if that white already has ten watts of green and you add a few watts of red and blue to it, then the white light has more power, thus is brighter. You could figure this out fairly easily but you need to define white, produced from combined RGB? If so, what wavelengths? However, for something to be perceived as white, you can assume an approx. ratio, when produced that way..

 

[Dridapada]

Yes. The white will be brighter.. But in terms of visibility how to compare white (composite of all wavelengths) and a 520 nm beam?

2 corrections in my data inputs :
1. Visibility needed is only 15 miles (aerial distance ) - my bad.

2. The angle at which the laser will be projecting is a critical factor for visibility. Because the intention is to create a vertical pillar of light.

Thanks!

 

[Alaskan]

Due to the air usually being far cleaner at higher elevations above the ground, in a normal high visibility atmosphere a vertical pillar of light which travels less distance to get to high altitude air will have less attenuation than a horizontal beam cutting through dirty air, so that is in your favour for delivering maximum light into the distance when pointed strait up, but without the particles in the air, you won't see a beam reflecting off of particles as brightly, if that is what you want to do. Thus, a vertical column of light can disappear quicker when pointed straight up than a horizontal, or an angled partially horizontal beam direction, but more people should see it due to going straight up. However, much depends upon the amount of power and divergence too, if you have enough power and a low enough divergence the beam will be uber bright regardless of traveling straight up, or out horizontally. Of course, if heavy smog or dust in the air, the beam might not be visible very far away, but should be much brighter for a shorter distance

It stands to reason a composite of different individual wavelengths (at a greater power than one wavelength alone), when combined to produce white or other color hue will always be brighter than any one color component at a lower total power. The following isn't the info you were after, but to compare the visibility of different colors, you must factor in the sensitivity of the eye to different wavelengths, this online calc will give you comparisons between colors and powers for relative brightness. Sure, just it is just comparing two colors, but you can get an idea, i.e. power for power, 450 nm blue is about 11 percent as bright to the eye as 520 nm green and 650 red also approximately 6% as bright: http://lsrtools.1apps.com/RelativeBrightness/?nm1=630&mw1=1&nm2=532&mw2=1&useRaleigh=on



To make white, you don't need to add 89 percent more blue and 94% more red with 520 nm green to make what is perceived as white, much less.