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

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

homemade optics

cds

0
Joined
Oct 22, 2008
Messages
8
Points
0
hey!

I am quite new to lasers, but I have understood everything about it.
I plan to build a LM317-driven DVD-burner laser module.

I have access to small glass lenses from old cameras, both concave and convex.
Now I could not found a serious tutorial about building a optical system to
archive a long and thin beam that will be visible over several 100 meters.

It should be possible to to this with 2 lenses, like in the picture.

Although I found articles that use the lenses in an other direction.

So how to do it REALLY?

Thanks
 

Attachments

  • collimator.jpg
    collimator.jpg
    46.2 KB · Views: 569





Joined
Jul 24, 2008
Messages
1,415
Points
36
i would recommend using a simple aixiz lense since it holds the diode in there and has an adjust able lenses already :)

they are about 4 dollars and im sure you will be very happy with them
 
Joined
Jun 3, 2007
Messages
2,560
Points
113
cds said:
hey!

I am quite new to lasers, but I have understood everything about it.
I plan to build a LM317-driven DVD-burner laser module.

I have access to small glass lenses from old cameras, both concave and convex.
Now I could not found a serious tutorial about building a optical system to
archive a long and thin beam that will be visible over several 100 meters.

It should be possible to to this with 2 lenses, like in the picture.

Although I found articles that use the lenses in an other direction.

So how to do it REALLY?

Thanks

The first lens in this drawing converges light. The second diverges light. What this drawing does not show is what happens to the beam of light after it passes the negative focal point, it starts exanding.

To do what you want the lenses must be in reverse order, even then it is probably not achievable if the converging lens has a short focal length. Do a real world experiment at night and see what happens.
 
Joined
Oct 2, 2008
Messages
266
Points
0
steve001 said:
The first lens in this drawing converges light. The second diverges light. What this drawing does not show is what happens to the beam of light after it passes the negative focal point, it starts exanding.

To do what you want the lenses must be in reverse order, even then it is probably not achievable if the converging lens has a short focal length. Do a real world experiment at night and see what happens.

Technically that is not true. If the two lenses were positioned exactly as calculated from perfect precision lens focal points, then the beam will be almost perfectly parallel and narrow. The only problem is that this is really rare, for the focal length of the lens must be specifically tailored to that particular laser.
 

cds

0
Joined
Oct 22, 2008
Messages
8
Points
0
Technically (from the view of a physics student) converging and then parallizing (does that word exist??)
should work.

If I put the concave lens in front of the laser, the beam will diverge even more that it does without lenses.
If I then add a convex lens in front of the concave lens, I could focus the beam for burning in small distance
OR creating a parallel, but wide beam.

does axiz ship to germany? I cannot imagine a nice laser beam after hammering out the original laser diode
and hammering in my DVD diode...


edit: just done massive forum reading here and elsewhere, and decided to give the aixiz module a try,
since everyone seems to be very happy with them.
well, if stonetek ships to germany. otherwise, I will play around with different glass lenses until success....
 
Joined
Jun 3, 2007
Messages
2,560
Points
113
Tw15t3r said:
[quote author=steve001 link=1224710394/0#2 date=122473012]
The first lens in this drawing converges light. The second diverges light. What this drawing does not show is what happens to the beam of light after it passes the negative focal point, it starts exanding.

To do what you want the lenses must be in reverse order, even then it is probably not achievable if the converging lens has a short focal length. Do a real world experiment at night and see what happens.

Technically that is not true. If the two lenses were positioned exactly as calculated from perfect precision lens focal points, then the beam will be almost perfectly parallel and narrow. The only problem is that this is really rare, for the focal length of the lens must be specifically tailored to that particular laser.[/quote]


Explain further please. How would the beam stay almost perfectly parallel and narrow after it exits a diverging lens ?
 

Switch

0
Joined
Dec 9, 2007
Messages
3,327
Points
0
It won't be even near parallel even if the lenses are built exactly for the purpose.Because of how light works, a thin beam is gonna diverge more.That's why we use beam expanders(devices that make the beam thicker) to get better divergence in return.The "beam quality" can be characterized by its M[sup]2[/sup] factor(typically 1.2 for good green DPSS lasers IIRC, 1 being a perfect beam, dunno about red lasers).You can trade off beam diameter for divergence using optics such that the M[sup]2[/sup] will remain constant.So if you have a 1mm beam with 1.5mRad, you can make it into a 1.5mm beam with 1mRad, and so on. :p

As for the lenses, I think you'll be happy with an aixiz module, but a collimating lens from a cheap pointer is going to work just as well. :p
 

cds

0
Joined
Oct 22, 2008
Messages
8
Points
0
Okay thanks for the explanation and endurance :D

So I guess aixiz modules also just work with a single convex lense,
and by moving the focal point into the center of the diode we get
a nice low-mrad beam that is still capable of burning some stuff.
 




Top