Focusing problems

[Frank T]

I have a fairly new GX3, 200mw green laser that I bought from Big Lasers. My current guess is that I over-payed for this unit....
It has a strong beam and I don't dispute it's advertised power.
The problem I am having is to get it to focus to a focal point.
I also have a 3000mw Sanwu blue laser that focuses precisely, so I know what I am looking for. The blue beam is also a big "chunkier", so seeing it taper to a precise point is easy. The green laser has a very tiny diameter to start with.....so seeing it constrict to a finer point doesn't seem as easy.
My guess is that the collimating lens of the green laser is not set correctly in the head.
I haven't gotten satisfactory answers from the owner of Big Lasers so I am determined to fix it myself.
Other than trial and error, is there a methodical way to adjust the collimating lens so I can obtain a focal point but also be able to then adjust the head back to an infinity beam?
I am able to rotate the lens freely within the head

 

[GSS]

I have basicly the same unit and mine does around 70mw..
I know your looking to focus as you asked the same question on your 1st or 2nd post. I wouldn't expect BigLasers to give any usable advice as they are just re sellers.
Did you try anything with the advice given from the first post, when you say you got the lens to turn freely, do you mean you loosend the glued lens on the head? 532nm are DPSS lasers and you will see a fine beam compared to the chunky 445nm blue which is a direct multi mode diode..

 

[Alaskan]

If there is enough thread for the collimating lens, should be very easy to focus to a point, but how close it can focus, with the lens being used, that is another question. Much depends upon how many threads you have in the lens holder to allow a wide adjustment range for the lens.

 

[GSS]

If there is enough thread for the collimating lens, should be very easy to focus to a point, but how close it can focus, with the lens being used, that is another question. Much depends upon how many threads you have in the lens holder to allow a wide adjustment range for the lens.

Chris, these style host's don't focus like the 301 styles do were they can focus somewhat wide and reverse to were you can see the fine point a inch or 2 away from the apature.
The head when tightened seems to be focused to infinity and when you un screw it the head falls off before the spot even comes close to spread wide.
If he loosens the glue in lens, he might find a good balance??
This is bascily the same unit the OP is talking about. If he can un glue the lens that is..

 

[Alaskan]

Well, that being the case what a pain to deal with. If it were out of focus enough, you could hold another lens in front of it to focus down to a point with, but not ideal and tedious.

 

[paul1598419]

You got to be kidding me! Just buy a 301 or 303 and be done with it. You can get them for as little as $6.00 each with free shipping or for ~$10.00 with crap battery and charger. Look on eBay. They are everywhere.

 

[Frank T]

For the person who asked if there was enough threads to adequately move the lens in and out; there seems to be plenty...and I was able to easily "break" the glue that was originally securing the lens. I can adjust the lens or head, or a combination of the two, so there is a very wide spot on the wall (about 6" in diameter) about 8 to 10 feet away. I can also adjust it so there is a small dot at the same distance. What I can seem to do is get to that point where I can "dial-in" a focal point the way I can see it happening with my blue laser. No one yet has offered any hard, detailed information on how to do this so I guess it's trial and error.....

 

[paul1598419]

For the person who asked if there was enough threads to adequately move the lens in and out; there seems to be plenty...and I was able to easily "break" the glue that was originally securing the lens. I can adjust the lens or head, or a combination of the two, so there is a very wide spot on the wall (about 6" in diameter) about 8 to 10 feet away. I can also adjust it so there is a small dot at the same distance. What I can seem to do is get to that point where I can "dial-in" a focal point the way I can see it happening with my blue laser. No one yet has offered any hard, detailed information on how to do this so I guess it's trial and error.....

The point here is to focus the beam down to a tiny spot about an inch or two from the aperture. That seems to be what this laser cannot do.

 

[Frank T]

That is the goal, exactly!...I can get a tiny point on the wall, 8 feet away, but I can't seem to get the same focus a few inches ahead of the aperture.

 

[paul1598419]

When I say tiny, I mean a small fraction of a mm. You aren't getting that on a wall 8 feet away.

 

[Frank T]

I just put a beam expander on it and was able to get the tiny focal point size in front of the laser head like I did with the 3000mw Sanwu blue unit.

 

[GSS]

You will lose some output with the beam expander.
I think the tight spot your looking for from a a inch from the laser head is doable if you play with the unglued lens some more.

 

[Frank T]

I believe you are correct. I will continue to close in on it. Thanks

 

[GSS]

Yeah, its just the balance of the lens turning and the head turning.
The pic I linked is a unit I broke trying to get the module out. I haven't touched the glued in lens yet but I have some similar hosts in black that I think the silver host head will fit on them. I can try also to see..

 

[Frank T]

The glue wasn't too hard to overcome. There is plenty of travel for the lens within the head.
It's going to be a matter of trial and error to zero-in on the lens position to get the focal point that I am looking for....the one that should have been pre-set by the manufacturer.

 

[GSS]

Are you getting a decent amount of turns both ways in the head itself? Before I dismantled mine, like I had mentioned when the head was fully tightened it would focus to infinity, and that's it.. So screwing the lens in or out and the combination of turning the head itself in theory should find that tight spot..Why I don't know.
The black host I mentioned is a different setup, the focus is fixed and the lens is in the module in the host, plus the silver host head won't fit..