Aixiz lens modification - "Stopper"

One thing that has always bothered me about the Aixiz modules & lenses is that they are easy to move out of focus.
I don't do a lot of burning stuff and am a fixed focus kinda guy. Sometimes it is difficult to re-focus the laser to "infinity" after the lens budges. Getting it right on takes some time and lots of fiddling. With 405nm and 445nm it is even more difficult since at long distances, chromatic aberration makes it hard to tell whether or not the beam is at minimum divergence or not.

So the other day I came up with a solution to this problem.

Materials needed:

• Focusable laser with Aixiz lens.
• Spare Aixiz lens (acrylic or glass)
• Some tools
• That's all

Essentially what I did is cut off a piece of an Aixiz lens nut to fill up the extra space in the module so that the lens stops threading in when it reaches the point that the beam is focused at infinity.

Here are some pictures (click for larger size):



As you can see here, I used a brass lens nut, cut it down to the right size and then installed it in the module. Notice that I cut off some of the bottom of the Aixiz lens to make more room for the "stopper" and to prevent the black paint from chipping and scraping off, possibly contaminating the diode window.

Another method I tried, but liked less, was this:



Here, the threaded brass ring is epoxied in position. This one in the picture I made a little too short so it doesn't meet flush with the focus ring.
Perhaps some of the guys with machining skills can make focus rings that do just this (if they don't exist already).

Now, the lens stops turning when it's focused for lowest divergence. No more fiddling or guessing! This modification is very easy and I think anyone with patience can do it. The hardest part is making the stopper just the right length and not too short. This can also be done with the Acrylic lens. Just pop out the lens and cut the black plastic lens "holder" to size. The stopper never needs to be removed unless you want to use a 405-G-1 lens or similar. The focal length of those lenses requires it to be very close to the diode window.
I hope some of you find this useful.
Thanks for reading.

Good idea.. The trick I use is once the focus is set, loosen the set screw for the
heatsink / aixiz module and push the module further into the H/S.

When there is no more slack, tighten the set screw. When the focus is turned
clockwise to tighten, it will come to rest on the face of the heatsink and
not allow further travel.

Teflon on the threads and a taunt spring also make the lens nice and stable..

I use teflon, but I hate the spring.
I do use the method you describe above when I can. There wasn't enough space in this build for it, though. You can see in one of the pictures that the Aixiz module is recessed in the heat-sink. That's as far as it would go without smashing the driver.

I don't do a lot of focusing anyway, so I'm not worried about the threads being really tight. I actually prefer it to turn without a lot of resistance. This is just so that optimal collimation is easy to find. :beer:

Thanks for your tricks guys. :wave:

I'm sure both approaches are very helpful, depending on the the host and the preferences. Especially when you don't have a focus ring, it's very bothering to adjust minimum divergence.

I have a similar problem: somehow stopping my beam expander at minimum divergence - in this case I will try an adjustable ring with set screws as stopper.

Pretty slick idea Daniel good on you bud

RA_pierce said:

I use teflon, but I hate the spring.

Click to expand...

I usually use the glass lenses in the metal threads, those work fine with some telfon tape and without the spring. It just takes a bit of fiddling to get to the right amount of tape so that it still turns, but won't move out of alignment.

As far as stopping it from focussing to a wider than infinite beam i prefer the second solution - if that goes wrong, you only use the lens, not the aixiz module with the LD in it.