Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



how to focus a beam?

Encap

Well-known member
Joined
May 14, 2011
Messages
6,196
Points
113
The more I play with it the worse focus it seem to have, I must had the lens at an angle before to get “good” aim at 10feet because I think I finally have it now the burn focus is about 4 inches from the pointer. At 10 feet I get a huge circle showing all the dust on lens and glare ring :(. I need a new tip assembly, lens or both to get this focus the way I want.

I doubt what you want is ever going to actually happen--you can maybe get closer to it but ....
You can modify/shape the output with lenses and loss of power but only to an extent --- you can not fundamentally change what it is at the source.

All lasers exhibit divergence--divergence is never zero ---there never has been a laser either DPSS or direct diode the starts at 5mm wide and is 5mm at infinity--even the best beam quality DPSS laser which are much more "perfect" than any diode laser ever can be.
Typical divergence is 1mm per meter of distance.

You can see the divergence spec on the Osram data sheet for your diode--last page here: http://www.semicomvisual.com/wp-content/uploads/2016/02/PLT5-510.pdf
It can never be any better than that.

If you designed something that needs that, you are SOL due to not understanding the nature lasers in the real world.

See Alaskan's comment in post #10 here: https://laserpointerforums.com/f49/laser-diode-chip-aperture-lens-aperture-wavelength-relationships-divergence-92977.html

"Even with low divergence single mode diodes, after leaving the facet the beam will spread very fast and after a few millimeters will quickly become much wider, but you can focus it down, how small? Depends on a lot of factors. I've never tried to calculate that because I am not interested in cutting lasers, only low divergence collimated lasers. I just did a google search and you can find more info that way as well as some here, but someone might be willing to crunch some numbers for you to see if what you want is possible. Most members expect a full forum search as well as a google search first, but I don't mind helping some, here's a thread relating to your question regarding beam spot size: https://laserpointerforums.com/f38/how-focus-405nm-laser-diode-small-round-spot-81383.html "
 
Last edited:
  • Like
Reactions: GSS



lightforce

New member
Joined
Jun 12, 2008
Messages
21
Points
3
Thanks guys, I think I figured it out. The head piece is constructed of a tube that hold the lens, and when I disassembled it and put it back several times the tube thread got moved just a tiny bit up and down. So the lens is now not focused. Just a few fractions of a mm result in poor focus and because the way it was tighten, it was impossible to get to “4mm” focus that g7 required. Along the way I learned a few nuances with glare, lens handling, etc... I need to learn how to fabricate my own metal sleeve to get what I want. I wish there is a way to focus by moving a sleeve up and down while it is only adjusting fine movements of the lens. But that seems to require a huge and complicated housing.

I should clarify, I want to be able to move the sleeve like a shot gun loading style, by movement of centimeter or inches, now screw type where each turn is a fraction of a mm
 
Last edited:

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
19,345
Points
113
Most lasers are focusable. The lens has threads that mesh with the internal threads of the module where the diode is pressed. So, by turning the head piece you can often change the focus. But, it isn't always clear where the adjustment is located on lasers that you buy. I personally prefer to build my own lasers as that gives me the latitude to have it the way I want it.
 
  • Like
Reactions: GSS

GSS

Well-known member
Joined
Apr 28, 2015
Messages
5,073
Points
113
I'm going to gamble and think you need a lens focus ring?
https://sites.google.com/site/dtrlpf/home/glass-lenses like ones that are standard for are hobby lenses?
They only let the lens screw in 1 1/2 rotation on average, also on your existing tube you can carefully use plumbers teflon tape on the lens threads to hold the lens tight to the tube.
 
Last edited:

10fenny

Well-known member
Joined
Sep 10, 2014
Messages
1,054
Points
83
Agree on the focus lens... sometimes when the host has it's own focus ring... the lens will screw too far into this ring and makes it impossible to get a full focus. You could lock the lens into the orignial ring after a turn or two...
 

lightforce

New member
Joined
Jun 12, 2008
Messages
21
Points
3
Should I also paint the inside black? is the aluminum color causing the glare / flair effect, or am I completely wrong? How do you guys combat glare? I see the link has the focus ring unpainted.
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
19,345
Points
113
If you are seeing flare or splash, this is common and at distance is normally not an issue. The only way to eliminate it completely is by masking. This is where you put a tube at the diameter of the beam exiting the lens, extended about an inch to keep it from exiting the lens. It is not caused by a reflection of the inside of the host.
 

lightforce

New member
Joined
Jun 12, 2008
Messages
21
Points
3
thought i would post an update after I "played" around with it and read a lot more from here. The pointer I bought here actually appears to have a poor lens setting, there's no thread on the lens holder, so it was loose, but after me messing with it a few times, its totally loose now I might try the teflon tape. The lens is now also marred or scratched, I am not sure if I did it, or it came like that. I know all this because now, taking the tip from an old dx200mw pointer, I removed the lens and its holder (1 piece and the lens never came out nor had I tried to remove it) and install it on the cyan pointer, the cyan beam now can be aimed as a dot at over 10 feet away, there's no splashing or glare, very very nice beam.

I am waiting for more g2 lens that's in a holder to come (ebay bought), so hopefully I can then have a true g2 lens (with no defect) installed on my nicer pointer, and also on my dx200mw pointer. I also bought a solarforce body, and 2 el cheapo pointers to mod, now the journey begins :)
 

trinh hong phuoc

Well-known member
Joined
May 12, 2017
Messages
959
Points
93
I'm sorry for reading the topic late, I'm the laser seller, actually I fixed the beam But that could easily be removed by hand, he contacted me but maybe I was not enthusiastic, I see the problem was resolved.About a g7 lens, it's a clean lens, maybe you're not familiar with rectangular objects
 
Last edited:

lightforce

New member
Joined
Jun 12, 2008
Messages
21
Points
3
The issue was that after I received it, the beam and focus was terrible, no matter how I adjust it (out of focus and terrible splash). That's why I had to take it apart and started cleaning the lens hoping to get rid of the splash, no matter what i tried, I can't get rid of the splash, then I tried to focus it. That's when I realize the lens appears marred. I also found out the focus needs to have the lens quite close to the diode window, your cap/adapter appears not capable of getting that close. Either way, it is fixed now with an alternate lens and lens holder. It is able to project a focused dot, not a line (nor a rectangle) at over 10 meter. So I just saying the focus or how you set it might be bad, or it could have gotten changed during shipment, not the rest of the pointer. I am happy with the purchase regardless, thanks!
here's the beam now, minimal splash, and great focus.https://imgur.com/a/g7j4RqY
 

trinh hong phuoc

Well-known member
Joined
May 12, 2017
Messages
959
Points
93
The issue was that after I received it, the beam and focus was terrible, no matter how I adjust it (out of focus and terrible splash). That's why I had to take it apart and started cleaning the lens hoping to get rid of the splash, no matter what i tried, I can't get rid of the splash, then I tried to focus it. That's when I realize the lens appears marred. I also found out the focus needs to have the lens quite close to the diode window, your cap/adapter appears not capable of getting that close. Either way, it is fixed now with an alternate lens and lens holder. It is able to project a focused dot, not a line (nor a rectangle) at over 10 meter. So I just saying the focus or how you set it might be bad, or it could have gotten changed during shipment, not the rest of the pointer. I am happy with the purchase regardless, thanks!
here's the beam now, minimal splash, and great focus.https://imgur.com/a/g7j4RqY
Thank you
Maybe the lens was dirty, did you replace the other one?
 

GSS

Well-known member
Joined
Apr 28, 2015
Messages
5,073
Points
113
Wow didn't realize you registered in 2008:)
Most have figured out the splash effect with these newer pretty 495nm's and such but using that old DX lens, you could be on to something..
 

lightforce

New member
Joined
Jun 12, 2008
Messages
21
Points
3
I am always a geek, and was into laser earlier but life got in the way I guess :D
I will report back once i am able to fit it with the new g2 lens that's coming (hopefully it is true g2 since I am buying off ebay, one never knows for sure)
I did notice some very light (soft?), and very wide splashing last night after I posted, I didn't even see it at first. So its not totally gone, however, its way better than out of focus/marred lens. I am curious what is causing any splashing if everyone is having issue? All I can think of is the diode window causing the issue, or is this physics do to the wavelength interacting with the window or lens?
 
  • Like
Reactions: GSS

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
19,345
Points
113
I have a great deal of experience with this diode and your photo is not better than what we normally expect. You will still see some splash if you have your beam stop within 6 feet and it tends to disappear once you get out about 20 feet. If your old lens was marred, you likely did that yourself. These powers are low enough to use acrylic lenses which are soft when compared to glass. Very short FL aspheris lenses cause a rectangular artifact to appear next to the dot which is the reason for using an acrylic lens which doesn't. Glad you are now satisfied with your laser's beam profile.
 




Top