Laser and beamexpander

[CurtisOliver]

Never mind your budget if you needed 20W. I believe 500mW will be enough if the beam specs are good to begin with and you use an appropriate ar coated beam expander. The only thing to note, is what Diachi said. Choose a model with high stability and a larger heat sinked host. Having a beam expander that will screw onto the laser will be handy. Remember that 10x would be fine as well. So if you have to stick to a 10x, don't worry about it.

Don't forget that you want to see a beam spot not back scattering.
After 8 miles the beam will be a mess. (it's not a vacuum but a real hot-cold moving air. A dike - higher humidity.)

20 W - might be not very safe to operate too.

Yes, atmospheric conditions don't normally play a part of everyday use of a laser, but in this situation it would. Check weather forecasts especially before you set this up. Too much heat and there will be haze. Check for fog/mist etc. As for the safety of using a 20W. There are considerable safety problems associated with that.

 

[steve001]

Glad to hear we dont need THAT much , it would be very expensive too probably. But Diachi , if we would go for the high stability laser( MGL) then what power do you think we would need ? 500 mW enough like Curtis said? Or do we need extra power ( the MGL -F-532 goes up to 2500 watts ) .

I have a 532nm laser with an output of 121mw, using a 5x expander I think I can see, naked eye, a spot on a whitish surface at about 14000 feet. I will double check the distance. With a scope or binoculars seeing a spot at greater distances won't be a problem.

 

[diachi]

I have a 532nm laser with an output of 121mw, using a 5x expander I think I can see, naked eye, a spot on a whitish surface at about 14000 feet. I will double check the distance. With a scope or binoculars seeing a spot at greater distances won't be a problem.

Not sure what OP is planning, but if he's planning on standing next to where the spot terminates then it'll be even easier to see since the light doesn't need to make the return trip as well.

 

[GIBSON 225]

Okay so if i understood it well both Curtis and Diachi agree that i should better go with a high stability laser (MGL series? ) instead of the PGL series ? And 500 mW should get the job done ... I will check for the 10x CNI laser , probably it matches well with their own products but i will check what you said about the coating etc. And 10 times may cause a bigger spot but advantage could be that i can see the result with my nikonP900 superzoom ( 83x optical zoom) and take pictures of it , and film it from 8 miles distance. I will post them on this forum , so you guys can see the results.

 

[diachi]

Okay so if i understood it well both Curtis and Diachi agree that i should better go with a high stability laser (MGL series? ) instead of the PGL series ? And 500 mW should get the job done ... I will check for the 10x CNI laser , probably it matches well with their own products but i will check what you said about the coating etc. And 10 times may cause a bigger spot but advantage could be that i can see the result with my nikonP900 superzoom ( 83x optical zoom) and take pictures of it , and film it from 8 miles distance. I will post them on this forum , so you guys can see the results.

The MGL have a flat base (with holes for bolting it down!) so they should be easier to mount if you're just going to be sticking it on a table or some such - they can also run indefinitely - especially if sat on top of a heatsink/chunk of aluminum plate. The PGLs are portable (handheld) and are round so you'd need to clamp them onto something - these cannot run indefinitely (few minutes at most is recommended) and you can't practically add additional heat sinking to improve that number. If you can live with the downsides of the PGL then that'd actually work. I'd still personally go with the MGL series.

CNI should be able to supply a beam expander with anti-reflective (AR) coatings for 532nm I'd imagine, I also imagine they'll be able to supply an adapter (if it's not built in) that lets you screw the expander directly onto the laser head. A large expander like that may need some support under it mind you.

The 10x will result in a larger near field beam than a 3x or 5x but a smaller far field beam as a result of the lower divergence.

 

[steve001]

Not sure what OP is planning, but if he's planning on standing next to where the spot terminates then it'll be even easier to see since the light doesn't need to make the return trip as well.

Won't even need glasses at that range - I hope.

 

[GIBSON 225]

Well , at CNI's they are persistent that i need more power than 500mW, strange... But i asked for the quotation of the whole MGL series so we can compare prices and maybe choose a high stability laser that is between 500mW and 1500 .. Will the difference be big between that range ? We also will need a generator .. Any advice or thoughts about that ? Thanks!!

 

[CurtisOliver]

The luminosity difference will obviously increase, but your quote will increase more. I honestly don't believe you need more than 500mW. If you do go for more power, then I wouldn't go more than 1000mW, as this will slightly hurt your budget.

 

[Encap]

Well , at CNI's they are persistent that i need more power than 500mW, strange... But i asked for the quotation of the whole MGL series so we can compare prices and maybe choose a high stability laser that is between 500mW and 1500 .. Will the difference be big between that range ? We also will need a generator .. Any advice or thoughts about that ? Thanks!!

If you are in USA you can't get a PGL ---CNI will not ship them to USA and some other places because it is illegal according to USA FDA laws, rules and regualtions.

When are you going to do this--what time of day---you may need a lot more power as CNI say if you want to do it in daylight.

YOu should have a look at this thread : http://laserpointerforums.com/f44/10-mile-distance-laser-92273.html

One poster comments:
" If your just doing this for fun, skip reading this post.

If you need a real measurement or this is a science fair project, read on...

Save your money and hire a surveyor.
Here is why:

So at 10 miles you will have atmospheric scintillation and refraction that does not quit.
Coherent light is subject to interference at the detector for each photon's beam path.

You get horrid low and high frequency noise. This is why light bulbs or Leds are used as sources for long distance light communications.

Next Question. How will you accurately find the centroid of the LARGE blob down range? Helps if your Blob is Guassian with a brighter center, but you would still have to find the center some how. This is going to need some serious robotics.
Or at least a photodiode/photomultipler sliding on a calibrated arm and a piece of graph paper."

 

[diachi]

If you are in USA you can't get a PGL ---CNI will not ship them to USA and some other places because it is illegal according to USA FDA laws, rules and regualtions.

When are you going to do this--what time of day---you may need a lot more power as CNI say if you want to do it in daylight.

YOu should have a look at this thread : http://laserpointerforums.com/f44/10-mile-distance-laser-92273.html

One poster comments:
" If your just doing this for fun, skip reading this post.

If you need a real measurement or this is a science fair project, read on...

Save your money and hire a surveyor.
Here is why:

So at 10 miles you will have atmospheric scintillation and refraction that does not quit.
Coherent light is subject to interference at the detector for each photon's beam path.

You get horrid low and high frequency noise. This is why light bulbs or Leds are used as sources for long distance light communications.

Next Question. How will you accurately find the centroid of the LARGE blob down range? Helps if your Blob is Guassian with a brighter center, but you would still have to find the center some how. This is going to need some serious robotics.
Or at least a photodiode/photomultipler sliding on a calibrated arm and a piece of graph paper."

Oooh, good point on the PGL! The scintillation/refraction noise shouldn't be an issue - it becomes an issue when you're using the laser to send some sort of data, but if basically all you're doing is using the beam to draw a line it shouldn't be a big problem.

 

[Encap]

Oooh, good point on the PGL! The scintillation/refraction noise shouldn't be an issue - it becomes an issue when you're using the laser to send some sort of data, but if basically all you're doing is using the beam to draw a line it shouldn't be a big problem.

Gibdon says: "Well we want to measure a long dike to see how level it is , but the dike is more than 8 miles so it probably has to be a green laser because of the visibility . It might be another wavelength but the main thing is that the beamspot will be visible after that long distance"

Still there is the centriod problem.
Depends what accuracy he want to have.
So question is still, how will you accurately find the centroid of the LARGE blob down range? Helps if your Blob is Guassian with a brighter center, but you would still have to find the center some how.

Gibson should look into how surveryers would accomplish the task, I would think. No need to reinvent the wheel if you just want to see how level a dyke is?

 

[diachi]

Gibdon says: "Well we want to measure a long dike to see how level it is , but the dike is more than 8 miles so it probably has to be a green laser because of the visibility . It might be another wavelength but the main thing is that the beamspot will be visible after that long distance"

Still there is the centriod problem.
Depends what accuracy he want to have.
So question is still, how will you accurately find the centroid of the LARGE blob down range? Helps if your Blob is Guassian with a brighter center, but you would still have to find the center some how.

Gibson should look into how surveryers would accomplish the task, I would think. No need to reinvent the wheel if you just want to see how level a dyke is?

Deliberately didn't mention the second problem because I didn't have an answer for it . Though, assuming you have a reasonably round beam, I imagine you could get an accurate enough measurement with a measuring tape or meter stick.

 

[GIBSON 225]

Thanks guys but we are definately going to try it with a laser because of several reasons. We will do the experiment in the evening , so the dike can still be seen but the laser will not have to travel through bright daylight. No problem with delivering probably cause we're living in Holland. When the spot will be reasonably round that will be okay . We will put a big white board on the end of the dike so the laser spot will be clearly visible. We will film the spot with superzoom camera from where the laser stands and also from nearby where the board is . We might deliberately choose the 10x expander because of the bigger diameter compared to the 20 x - it then will be easier to photograph and film from this long distance.

 

[steve001]

Thanks guys but we are definately going to try it with a laser because of several reasons. We will do the experiment in the evening , so the dike can still be seen but the laser will not have to travel through bright daylight. No problem with delivering probably cause we're living in Holland. When the spot will be reasonably round that will be okay . We will put a big white board on the end of the dike so the laser spot will be clearly visible. We will film the spot with superzoom camera from where the laser stands and also from nearby where the board is . We might deliberately choose the 10x expander because of the bigger diameter compared to the 20 x - it then will be easier to photograph and film from this long distance.

You may like this experiment. The red dot in the photo is a low divergent 10,5 or 3 mw laser beam.
Crossing 'The Channel' on 670nm
The English channel may only be a 22 mile stretch of water separating England from France, but over the years, there have been many and varied attempts to cross it. From the first successful flight by Louis Bleriot in 1911 to channel swimmers, wind surfers, hang gliders, even an attempt to drive across in a converted VW beetle - which sank half way. Our chosen method was to cross it using lasers and to have a 2 way QSO which would also be a first between England and France. Link: crossing the channel

 

[CurtisOliver]

Cool, a laser experiment on home territory that I didn't know about. Nice find Steve

 

[steve001]

Cool, a laser experiment on home territory that I didn't know about. Nice find Steve

I'd like to see more experiment instead of lasers burning stuff.