Short range laser pointer

[callump]

Hi Nigel,

would be interested to see how you get on with the interferometer.

Yes, I agree - green laser pointers SHOULD have good IR blocking in-built - unfortunately it's impossible for an ordinary person to tell. You can buy verified ones (that come with a spectrum) - but they cost at least 4X or more than shop / ebay ones. 

Its a long time since I did laser physics, but I guess the green laser pointers have a good coherence length because of the crystal that does the frequency doubling can be (or has to be) made with some precision. 

Cheers, Callum

[Astrobits]

Hi Nigel,

would be interested to see how you get on with the interferometer.

Yes, I agree - green laser pointers SHOULD have good IR blocking in-built - unfortunately it's impossible for an ordinary person to tell. You can buy verified ones (that come with a spectrum) - but they cost at least 4X or more than shop / ebay ones. 

Its a long time since I did laser physics, but I guess the green laser pointers have a good coherence length because of the crystal that does the frequency doubling can be (or has to be) made with some precision. 

Cheers, Callum

Yes, that thought ( the effect of the frequency doubler crystal) had crossed my mind also.

The interferometer that I plan is of the Ceravolo design. The reference lens is the most problematic and I hope to find a camera lens that I can take apart to give me single lens that only needs one surface re-grinding to provide the reference, the other surface staying A-R coated.

Nigel

[101nut]

The danger with many Green lasers is that they also emit a lot ( several times the listed power of the laser ) of Infra-Red light which can damage the retina, 

Nigel

I think this statement is a bit scaremongering. Because of the method used to generate the colour, the original source is infra red and, if incorrectly manufactured, misaligned or damaged the system *may* emit infra red. However they should not and are not designed to emit infra-red by default as it proportionately reduces the effective visible output power. 

The biggest problem is that the lasers themselves are often significantly in excess of their rated output ...

AndyG 

[Mr TamiyaCowboy]

Ok to answer your question 

How far will the beam travel, it would be very unfair for me to say, how long is a piece of string

but that is the truth. 

power does not equal distance, given the fact dispersion , batterys, voltage, current and the Laser driver curcit (sp)

the variety is huge, small things affect in a big way. 

laser power is just that, how powerful a beam is energy wise. higher the mw the more powerful the laser,

not in terms of beam length but heat. party tricks are lighting matches and popping ballons.

lensing is where the beam length comes from, but again for every gain you will loose something. 

1 - 5 - 500mw  dont matter on the power its the lensing that gives the beam direction,

as for beam length only you can really know that by finding out. problem also lays with the cheap lasers sold

you can by very powerful things these days, rated alot more than specs given, so you also have that danger to

backyard/sweatshop electronics

[Astrobits]

I think this statement is a bit scaremongering. Because of the method used to generate the colour, the original source is infra red and, if incorrectly manufactured, misaligned or damaged the system *may* emit infra red. However they should not and are not designed to emit infra-red by default as it proportionately reduces the effective visible output power. 

The biggest problem is that the lasers themselves are often significantly in excess of their rated output ...

AndyG 

Not scaremongering at all.

Just read the last post.... "party tricks, popping balloons, lighting matches" are all due to the IR emitted.

Even those that claim to be the best manufacturer only claim to remove >96% of the IR. Their 5mw green laser pointer has a 250mw source laser diode so emitting 4% of that is 10mw emitted IR. i.e twice as much IR as visible.

http://www.optotronics.com/green-laser-pointers.php

Also check the previous link in my posts here.

Nigel

[RT65CB-SWL]

My opinion is that any laser (red, green, blue, etc) irrespective of the output, viewed 'head-on' is blinding to, or dazzles the recipient. No wonder aircraft pilots and crew start creating waves when they are 'under attack' from them.

And slghtly off topic, why do we have private and commercial vehicles on our roads equipped with those damn 'Ice-White' & 'Ice-Blue/White' headlamp bulbs? I would not mind them fitted or limited to emergency vehicles only. But for private and commercial vehicle use... come on! What or where is the logic in their use?

[Mr TamiyaCowboy]

problem is how these things are made. 

lets take a PS3 game system, its got a laser a class 1 beast. its powerful enough to pop

ballons and set fire to matches, 

lets skip to the military USA , hmmm shove a big laser on a truck, aim it at a jet fighter

couple it with gyroscopes and IR tracking. near instant melting of aircraft alloy. and a blown up craft. 

these laser have had plenty of R&D, they have strict testing.

take your ebay pointer a class 3 laser, so it says, but is that true, 8-10 time no

the laser can be as powerful as a class 1. it just depends on the choice and price of the used electronics at the time.

and this is not good stuff, its electronics that failed the strict testing, but its sold on and used else where.

namely your cheap laser pointer. 

i am in the same boat, i live very close to both military and civi airports and have a flight line over my village.

so i do not use laser pointer myself for this reason, so not scaremongering just pointing out the facts

they can be handy items but with use there is always that danger of the local bobbys knocking on your door.

[callump]

I think that green laser pointers are really useful for pointing out constellations and stars and planets to the general public at viewing evenings.

Beyond that, i think they have little utility.

Used with care there should be no problem with them - but people need to be aware of what's happening around them when they are used, which is the main reason why i am not keen on them as finders on telescopes - too easy to be distracted looking for what you are looking for, and not what your laser is pointing at...

Callum

[Digz]

Beyond that, i think they have little utility.

I beg to differ. They are great for getting my parents cats running about the lounge like maniacs

[justinroz]

I think green lasers will be better at visibility than red/blue ones. Look at this 5mw green laser:

"NOTE: Even though it's low power as only 5mW but still can cause damage if you make the laser beam toward the eyes."

But I don't think that power can cause fire...

[TCWORLD]

Jut to add to the 'distance' side of things. I have a laser spirit level which even in daylight you can see the dot it is projecting from 30m away, and that is a red <1mW laser with a diverging beam.