First post! Unique request.

GeoBruin · Jan 25, 2011

Greetings everyone!

I've read up a bit on some of the focusable options out there, but I'm not sure if I have things clear in my head. As I understand it, a commonly desirable trait of a focusable laser is to focus the beam on a convergent point some distance from the head which allows for burning and such. I'm looking for something different.

I would like to increase the divergence of the beam, making the spot larger when it reaches my target. I realize that after a beam converges on a point, it will then diverge but I don't like the idea of having a point just a few feet or so from me that is capable of getting hot etc. I would prefer to let the beam begin diverging at the lens, where it would never create a point of convergence down range.

If such a thing does not exist, I may have to reconsider, but I'm hoping that some of the experts on this forum can point me in the right direction. Also, I should mention that I am looking for a green laser in the <30mW range.

Thank you!

rhd · Jan 25, 2011

I may be misunderstanding you, but I believe any lens should be able to accomplish this (or no lens at all). When you first put the lens on, without screwing it in very much, it should be doing what you're looking for.

anselm · Jan 25, 2011

^^^ What he said.
If you are able to adjust the lens on you laser at all, chances are you can achieve the effect
you are looking for.

When the lens is "far" away from the diode, it will have the effect you want.
As you screw the lens closer to the diode, you reach the point where the beam is focussed
parallel, to infinty.
If you continue turning the lens closer, the beam will "cross" and create than thin spot that you don't want.

RA_pierce · Jan 25, 2011

The most common focusable lasers are built with the Aixiz modules.
These allow the beam to be adjusted to converge, remain parallel over large distances, or to diverge rapidly without convergence.

All you have to do is thread the lens in all the way.
Another method, if you are using a laser that is not already focusable, is to place a concave lens at the laser's aperture.

And to correct those above, when the lens is "far away" from the diode, the beam will be focused. The further away the lens is from the diode, the closer the focal point will be to the aperture. Bringing the lens closer to the diode extends the focal point into the far field and eventually to "infinity" (which means the least divergence). When the lens is moved closer still, the beam will start to diverge rapidly with point of convergence.
I'm not sure what anselm means by "the beam will cross," though.

GeoBruin · Jan 25, 2011

Okay, so from what I understand, almost any laser with a dedicated focusing ring will allow me to make the beam converge and diverge right out of the lens. If that is the case, can someone recommend a focusable green laser for me? As previously stated, I'm looking for something in the <30mW range (though I understand it is probably harder to find one in this range than at higher powers). I have looked at the Ray Foss 50mW 532nm focusable laser but that's a bit too much oomph for me. I would love one in a pen format (AAA or AA) but I realize there are probably very few focusable lasers that small.

Your help is appreciated.

RA_pierce · Jan 25, 2011

Hmm...
I have not personally tried out any of the focusable green lasers. I don't think they are capable of being focused as you want.

One option as I stated above is to place a concave lens in the aperture.
Another option that would not require any additional optics would be to adjust the lens that is already installed.
This would mean that the beam would be fixed, though. So once you set it where you want, you would not be able to adjust it on the fly.

This laser is particularly easy to modify. It requires no special skills or tools.
All you need to do is pop off the silver aperture cap (careful not to scratch it) and then screw in the lens and test it to make sure you are getting the desired divergence angle.
http://ledshoppe.com/Product/ledp/LP1076.htm

Meatball · Jan 25, 2011

Your standard run of the mill DPSS green pointer is not a focusable device. They are built to emit the beam while focused out to "infinity". The beam remains very close to parallel until you get further and further away from the source. A typical full angle divergence rate is 1.3 milli Radians.

GeoBruin · Jan 25, 2011

You make good point and it's something I forgot to mention. I would like to be able to adjust the divergence on the fly. I guess when I say "focusable" I mean that there is a dedicated focus ring.

Thank you,

rhd · Jan 25, 2011

My strongest green is (who knows what mW, but probably ~150mW) in an SDLaser 301 host.

Without the lens on, it VERY quickly diverges. Like - 1 foot circle by the time it hits a wall 10 feet away.

Now, this may be unique. Perhaps because they intended the module to be used in a focusable host, they used different optics in the module itself (optics that didn't focus the beam to any great extent) However, it is definitely possible to find this ability in a green focusable laser.

rhd · Jan 25, 2011

I might recommend the 50mW dealextreme SD 301 laser.

It has been tested on these forums. I bet you could add an IR filter, and you'd probably have ~30mW of 532nm. That host can definitely accomplish your goal. I'm staring at it doing so now.

(though I didn't buy mine from DX, so your mileage may vary)

rhd · Jan 25, 2011

Ok, I'm even more convinced that the SD301 in a 50mW version would be the laser for you. Approx $30 - is that in your budget?
(lol, to clarify in case that was confusing - I was suggesting you order a similar laser - I'm not selling mine, haha)

If you'd like, in an hour or so when I get home, I'll take a couple photos to show you.

GeoBruin · Jan 25, 2011

Photos would be great! I guess I'm interested in seeing how big I can make the dot at say, 10 feet, and 15 feet. Also, I'd be interested in knowing where you got yours, as I'm in the U.S. and can't order a >5mW laser from DX.

Thank you,

benmwv · Jan 25, 2011

Yeah just take the lens off any green and you will get what you want.

What is the application of this?

chipdouglas · Jan 25, 2011

i recommend a beam expander from dragonlasers. they are like 80 bucks.

michael.

anselm · Jan 25, 2011

RA_pierce said:
And to correct those above, when the lens is "far away" from the diode, the beam will be focused. ......
I'm not sure what anselm means by "the beam will cross," though.

Of course, it is just like you said, what was I thinking?:beer:
I was imagining it the other way 'round, silly me.
What I meant was that "hourglass" shaped beam.

rhd · Jan 26, 2011

I happened to be playing around with it tonight anyway, so I snapped a couple photos. Cameraphone only, so the best way I could illustrate the beam was by shining it parallel across a table.

In the first beam photo, I don't even have the focus lens on, and you can see how quickly the beam (if it's even considered a beam at that point) diverges.

In the second photo I have the lens on, but "furthest" out away from the point of laser emission.

There's a long story to mine. Keeping it brief, I wasn't supposed to be sent this laser. I bought something else, the seller shipped the wrong laser (this). I complained, and got the remedy of a partial (60%) refund, plus was allowed to keep this laser.

I'm sure someone else can speak to where you purchase lasers from if you live in the US. I do not, so I'm not much help here. However, I don't think this is a hard laser to find.

First post! Unique request.

GeoBruin

0

rhd

0

anselm

0

RA_pierce

0

GeoBruin

0

RA_pierce

0

Meatball

0

GeoBruin

0

rhd

0

rhd

0

rhd

0

GeoBruin

0

benmwv

0

chipdouglas

0

anselm

0

rhd

0

Attachments

Online statistics

Forum statistics

Share this page