usefulness of beam expanders

[BKarim]

they are not as useful as resellers claim: the minimum angle at which a good naked eye can separate 2 points is 1' = 0.3 mRad.

so there is no need to reduce the beam divergence below 0.3mrad since whatever the real size the dot will be, it will be seen as a thin point if you stand near your laser.
apparent range will not be increased with a div of 0.03 mRad compared to 0.3 mRad (it will only be increased if you move close to the dot)

as the average divergence of laser pointers is 1.5 mRad, a 5x beam expander is sufficient until you stay near your laser.


i think this text should be rewritten in correct english and put in the FAQ

 

[Asherz]

While this is true, the only use of a beam expander is not just for the user.

For example if you wanted to shine your green laser on a land mark far away, and have a person at that land mark observe and see if they could see the dot, seeing a dot 2" in size would be easier than a light green dim 5 feet wide.

Another use is burning, that small divergance comes in VERY handy for long range burning or poping of baloons

Thanks for the info though, and your English seems to be fine.

 

[BKarim]

For example if you wanted to shine your green laser on a land mark far away, and have a person at that land mark observe and see if they could see the dot, seeing a dot 2" in size would be easier than a light green dim 5 feet wide.
.

sure, but i was telling about "fixed" use: what divergence you need (or don't need) to see your dot the farthest away without travelling towards the dot

 

[Greenmechanic]

they are not as useful as resellers claim: the minimum angle at which the average naked eye can separate 2 points is 1' = 0.3 mRad.

so there is no need to reduce the beam divergence below 0.3mrad since whatever the real size the dot will be, it will be seen as a thin point if you stand near your laser.
apparent range will not be increased with a div of 0.03 mRad compared to 0.3 mRad (it will only be increased if you move close to the dot)

as the average divergence of laser pointers is 1.5 mRad, a 5x beam expander is sufficient.

I also find that a 5X beam expander works fine for most laser applications.
While it is true that the 10X, 20X, 30X do a better job then the lower powered ones, the difference in function do not justify the (much) higher cost.
Others may have a different opinion then mine, depending on their usage of their B/E, but this is just my 2¢

 

[Deleted member 10578]

they are not as useful as resellers claim: the minimum angle at which the average naked eye can separate 2 points is 1' = 0.3 mRad.

so there is no need to reduce the beam divergence below 0.3mrad since whatever the real size the dot will be, it will be seen as a thin point if you stand near your laser.
apparent range will not be increased with a div of 0.03 mRad compared to 0.3 mRad (it will only be increased if you move close to the dot)

as the average divergence of laser pointers is 1.5 mRad, a 5x beam expander is sufficient.


i think this text should be rewritten in correct english and put in the FAQ

Hi BKarim,
I don't think this should be put into the FAQ as the information is not correct or I should say is being applied in the wrong way.
True, the human eye can only distinguish two separate points of light if they are separated by a large enough angle; but this has nothing what so ever to do with beam expanders.
The beam from a laser is one beam of light, not two. Stars are perfect points of light and we can still see them. A 10x, 20x or 50x beam expander will allow the beam from a laser to spread out less and be seem from a greater distance.
The person pointing the laser may not see much or any difference between 5x and 10x from his point of view, but a person 30 or 40 miles away will be able to see the difference as the spot size will be much smaller and bright for the 10x expander (provided the output power and begining divergence of the 2 lasers are equal).

 

[BKarim]

bootleg you are confusing with power of separation and power of detection (this is translated from french, i don't know if they are the correct expressions in english).
sure you can still detect two points (or one disk within these two points) that are below 0.3 mRad but you can't distinguish them: you will only see one point.

and i was only telling about usefullness of beam expander when you stay close to your laser (i will precise it in my first post)