How to fix - laser fades out from the center. lens is clean

I am using a JPT M7 60W MOPA Galvo Laser. The blank is 4.5" long and I am using a f=254 lens.
I am doing the same thing that I have done since I have purchased this machine. But today is different.

Today my marks get lighter as the laser moves away from the center of the blank. The blank is anodized aluminum.
I took off the lens and inspected it and it is clean as a whistle.
The last thing I did with this laser where I might change any settings was to install a camera and align the camera but that was all camera related stuff,
Please assist.
Thanks, Wes

The source goes to the galvo heads, then through the lens. I doubt the souce knows where you are, so that’s eliminated. That only leaves the galvo, as it can’t be the feed to the galvo.

Do you have multiple lenses? Could you be running a configuration setup for another lens?

That’s about all I can think of.


Could be “focus shifting” this happens when a lense or mirror is broken or dirty, it gets hot and will shift your focus after a few seconds the laser is working.

You can check that when moving your sheet up and down when your beem seems weak. is it stronger when you move it further up or down you have focus shifting.

Check your lense, beam combiner lense or the lense on the collimator, one should be dirty or broken.

Are these in the source?


Nope, between galvo and the part where the beam comes out of the fiber

Never had mine apart, it just went out of warranty.

Is that in the box on top before the small tube to the galvo?

Hunted around on the Internet, but didn’t see anything that looked like this…


There are two lenses and it’s a real butt pucker moment for me to touch either of them. But is this what you had in mind?

Good to know. I do not know what those are or where to find them. Also, I don’t konw if I can touch them or what is the best solvent to use…Isopropyl alcohol?
Thanks for your reply.

So it’s in the head?>

If they look clean, put the lens back. There is no reason they should get dirty.


…did that immediately after the photo. Thanks.

Please send us a video or photo of marking results

Yesterday it was fading toward the bottom. I attached a photo comparison on the left is the performance I am accustomed to. On the right is the fade it was making.

Today it seems the shade of white engraveing is more consistent from top to bottom but now it is grainy and unclear. I did check the focus.
short video

In the video below I did a fill over the whole area to illuminate the weak spots.
Long video

Thanks for responding.

Have you tried this with another lens?

It seems to still follow that the source doesn’t know the machines location so what’s happening has got to be after the output of the source. That leaves on the galvo and lens…

I think you’ve stumped us… my only though is a difference lens, even with the same focal length…

I know it’s a crap shoot, but I don’t have any other suggestions to ask you to try that might help isolate the issue in more detail.


Please check the level of lens and table, it dosnt seems to “thermal lens”.

You may have nailed it. Still checking but I saw this video and it also took me down this path.
Solution to fading How to Set Up A New Fiber Laser or Lens