DIY Beam Expander

[Gryphon]

Here is my attempt a your basic beam expander. The whole thing consists of
just two double concave lenses and a dichro. All three of these optics
have been taken from an A140 projector. The laser is an Aixiz 50mW labby,
with which i have removed the final lense from and in its placed glued on one
of the projector lenses. In the interest of saving space and making this as
compact as possible i reflected the beam 90 degrees off a dichro before
passing it through the second lense. The second lense is mounted to a
threaded pipe cap and which is screwed into a small peice of threaded pipe.
This allows for a small amout of adjustablity in its focus. The dichro and final
lense are then held in place by some angle brackets.

 

[Gryphon]

The last pic is the dot profile at 60ft. Without a flat clean surface to project the dot
on it was hard to find the best focus for the laser and get the abosolute smallest point.

 

[lowell389]

Man. That is a nice set up. I have a box of projector lenses in my shop somewhere, seeing what you have done there has given me the drive to get out there and dig it out. Lol

 

[Tech_Junkie]

Nice work. :beer:

Whats the reasoning using a dichro over a FS mirror?

 

[Gryphon]

Whats the reasoning using a dichro over a FS mirror?

I didn't have any FS mirrors. It does a pretty decent job, my eye ball LPM say its reflecting up 80% of the laser :tinfoil:

 

[Bionic-Badger]

This is good work. Can you make a short tutorial on this? I've been wanting to make a green laser beam expander so that the beam would be roughly the same size as diode laser beams. If you have some parts from the A140, you could also use the FS mirrors from it.

 

[Gryphon]

I've been wanting to make a green laser beam expander so that the beam would be roughly the same size as diode laser beams. If you have some parts from the A140, you could also use the FS mirrors from it.

The good thing about having the projector parts is that there are plenty of different lenses to choose from. What i ended up doing was using one with the shortest focal length i could find to expand the beam, and then a lense with the longest focal length to re-collimate it. Im sure with some experimenting you could find one to expand the beam only ever so slightly.

Yes, i could have used the FS mirrors that were in the projector but unfortunately the only ones i have left from the projector are the thin ones placed in front of the diode block and they seem to have under gone some degradation. The mirror coating seems to be dieing and turning into a purple frost, when i run my finger over it i wipes off easily leaving the clean and clear glass under it exposed.

 

[Tech_Junkie]

Thats strange. Never seen mirrors do that before. Maybe they do that on purpose so when they degrade you have to buy another projector.

 

[Gryphon]

What i wanna know is if it is something that could be fairly common with the projectors made around the same time mine was. Could you imagine buy one for use as a projector and having those mirrors fade away like that, its gonna throw the color balance way off.