Lens recommendation required please

[zartoop]

I have made a 635nm - 670nm 250mw handheld laser for light plastic welding. Yes it does work!

Used standard Aixiz module, DVD diode etc
I have Aixiz acrylic and glass lenses, plus empty Aixiz lens holders.

I am not happy with the collimation of the lenses that I have although I might be expecting too much.

For practical purposes I am ignoring lens divergence in the following.

I assumed that a collimated beam if it was 2mm dia at lens would be 2mm + divergence at distance (for all practical purposes I am not too worried about divergence)

It seems that the lenses that I have do not produce a true collimated beam but rather one that focuses at infinity to a point (~2+mm) at distance and the beam diameter at lens is ~3-4+mm.

To get a 1 - 2 mm spot at ~50mm from the lens (which is needed for the plastic welding) I have to unscrew the lens almost completely and the spot at 5 mtrs is 300+mm.

I want a true ~2mm collimated beam that is 2mm from the lens to about 300mm ...

What lenses do I need with the holders that I have?

 

[Johntabby]

What glass lens do you have? aiXiz glass? 3 element glass? 650-G-2?

 

[zartoop]

all aixiz lenses

 

[zartoop]

so no optics experts here at all?

 

[Eudaimonium]

So you basically want to have a 2mm wide beam at aperture exit?

I don't think you can achieve that without some heavy improvising, and divergence will be worse. Divergence is inversely proportional to width of the beam at aperture.

I don't believe I've seen a M9 x 0.5mm threaded lens pack (Aixiz standard) that gives a tight beam at aperture, most are designed for 5mm wide beams that you already have.

You can try experimenting with various optic pieces found in sled drives, but beyond that, nothing is commercially available, as far as I know.

 

[steve001]

I have made a 635nm - 670nm 250mw handheld laser for light plastic welding. Yes it does work!

Used standard Aixiz module, DVD diode etc
I have Aixiz acrylic and glass lenses, plus empty Aixiz lens holders.

I am not happy with the collimation of the lenses that I have although I might be expecting too much.

For practical purposes I am ignoring lens divergence in the following.

I assumed that a collimated beam if it was 2mm dia at lens would be 2mm + divergence at distance (for all practical purposes I am not too worried about divergence)

It seems that the lenses that I have do not produce a true collimated beam but rather one that focuses at infinity to a point (~2+mm) at distance and the beam diameter at lens is ~3-4+mm.

To get a 1 - 2 mm spot at ~50mm from the lens (which is needed for the plastic welding) I have to unscrew the lens almost completely and the spot at 5 mtrs is 300+mm.

I want a true ~2mm collimated beam that is 2mm from the lens to about 300mm ...

What lenses do I need with the holders that I have?

No one can tell you off the cuff and it's a lot of work. That has to be figure out either by trail and error on your part or by using an application this one for example. So if you want to do the work have at it. If you need guidance I can assist
gausian beam rev 2.0.xls

 

[Bionic-Badger]

I have made a 635nm - 670nm 250mw handheld laser for light plastic welding. Yes it does work!

That's a wide wavelength range. Depending on the diode you're using, it may not be possible to have the beam specs you're asking for. For example, if you're using one of those Mitsubishi 638nm laser diodes, they have terrible beam specs and you can't produce a round dot without very special optics. It's a lot easier with a 660nm laser diode, however, and you can usually get a pretty decent dot at 300m.

As for a "true" collimated beam, it's going to be hard to do that with 2mm. The smaller the beam at aperture, the wider the divergence. You'll probably need to settle on a wider beam if you want things to stay collimated. Even if it were reasonable, you're also looking at having to use some precision optical mounts and lenses. You're not going to get that out of optics made for handheld lasers; they're just not made for it. You would also probably end up spending more on the optics than your laser, much like Lazeerer has with his work into beam correction.

 

[zartoop]

Thanks for your suggestions guys - I really appreciate it. I done a lot of reading since posting and your comments and advice are really helping. Thanks for the links and tips - I'll get back once I've researched your links and advice. Thanks