Beam expander lenses position.

[Hermes]

It's been a while since I last posted, it's good to be back!

I bought a beam expander a while ago, and I finally got it installed this week, however, some problems arise when I try to work over a wider area on my machine, the laser beam seems to grow larger the further away it gets from the laser source. I must confess, I dissasembled the lenses to make adaptations to the aluminum tube containing them so I could adapt them to the customizations I've made to my gravograph, so there's a chance I've misplaced them, even though I identified them and re-installed them in the same positions.

The expander is this one;

http://www.lightobject.com/2X-Beam-Expa ... -P757.aspx

Ideas and suggestions are welcome.

Hermes Sandoval

[Tech_Marco]

Hi Hermes:

What is the power of your laser tube? How about the diameter of the reflection mirror, laser head inlet hole size, and the focus lens diameter. It is all counted toward to the proper type combiner being used.


Marco

[Hermes]

The tube is a Synrad Firestar, 40 watts.
The first reflection mirror is 6mm in diameter.
laser head inlet hole is 9 mm.
Focus lens diamter is 20mm (I'm meassuring the laser ray's diameter by burning a piece of masking tape before de focus lens at different positions.
The diameter of the laser ray coming out of the tube is 3mm aprox.
the diameter of the laser ray doubles at 60 cms away from the source.

I may try to reassemble the expander's lenses, just wanted to be sure about it.

Thahk you for your response, Marko.

[Tech_Marco]

Hermes:

Then the 2.0x is not a good one for you. Here is the reason:

1) 40W laser usually has beam diameter in 4~5mm. For Synrad, if I'm wrong, it is a RF laser tube. The beam size could be as small as 2mm to 3mm. After 2.0x beam expander, the beam diameter is now 4~6mm

2) 6mm mirror is too small. After minus the mount area. You may get 4~5mm. When a mirror placed in 45 degree angle for 90 degree reflection, the actual workable diameter is "diameter of the mirror * 0.707". So, let's say you got 5mm diameter after mounted, the actual diameter you have is 5mm * 0.707 =3.5mm. So.... how could it handle 4~6mm beam?!


I just need to make things clear here. When you mentioned that the mirror was "6mm". Was it the actual mirror diameter or the diameter you could measure when installed on the mirror mount? Either way, 2.0x beam combiner is not suitable for you in this case.
Let me know the actual mirror size and the useable diameter (installed)


Marco

[Hermes]

The 6mm mirror is located right after the laser beam's inlet hole, then goes the beam expander, I've meassured the laser beam right out of the laser tube by burning a pulse on a piece of MDF and it's around 3mm, +/- 15%. After the 6mm mirrror it's the beam expander, the beam grows only if I use the beam expander. I still get a stunning quality and good output power, but only close to the beam source.

Did I mention I had to dissasemble the lenses to work on the beam expander's tube?

Thank you for your kind attention.

Hermes