Beam along with flashlight circle

[Bob Cole]

My laser seems to be engraving/cutting like normal but I've noticed on the piece that I am working on a circle of light (about the diameter of the focusing lens). I don't remember seeing this before and assumed lenses were dirty. I looked at all the lenses and cleaned if necessary and ran again, no difference.

Am I losing it and this was always there or has something changed?

[Dan Hintz]

This is usually a sign the final tube optics is misaligned. Watch it closely, and pay close attention to temp of the tube...

[Mike Mackenzie]

Bob,

What are you engraving? It almost sounds like you are getting a reflection of Visible light coming through the lens. Some materials will do this.

[Bob Cole]

It shows on wood and corian and I am sure it wasn't there the last job I ran.

I was trying to think back on what I have been doing that could have caused this. I did reconfigure my dessicant/air filtration and installed an additional shut off valve and air pressure valve. I am really hoping that the air pressure valve is working correctly and not too much pressure went to the laser. Warnings in the book discuss too much pressure can cause damage.

I also put on and take off the cone dependant on what I am doing. Wonder if I did something.

I looked at my number 1 optics. with a flashlight and it almost looks like there is a smudge on the inside. I am wondering how anything got on the inside as it looks like it is sealed. I am wondering though if what I am seeing is a reflection from the flashlight to something inside and back. I don't have the proper tools to remove this optic and wanted to verify with you and ULS that it won't cause any issues If I do remove and inspect.

[Mike Mackenzie]

Bob,

If you take the cone off does this Beam go away?

You can remove the beam window without much trouble. just keep your fingers off of the optic itself.

This may be the cause you can also run a quick job without the beam window and see if the Spot goes away.

Don't do anything large with the beam window out. You don't want a lot of debri getting into this area.

[David Fairfield]

I've noticed this phenominon too, when cutting at very high power. There is a circle of greenish light around the center of the beam. As long as the laser is cutting as normal and the lens is clean, I believe its just a case of more stray photons reflecting back to the viewer than when the laser is at low power. Its always happening but its more noticable at higher power.

Why some proportion of photons go astray is very complicated and has been explained by the strange theory of Quantum Electro Dynamics (QED)

http://en.wikipedia.org/wiki/Quantum_electrodynamics

Very few people can wrap their brains around that, but the important thing is, what you're seeing is probably not due to a mechanical failure. :)

Dave