Added bounce effects, video and safety question.

[polishedball]

While I get that no one can say for certain, I added a couple bounce effects to spice up the just beam bounces in my basement, the one effect is fully over head, the other washes the seating area. I am looking for information on how one would determine the safety of the diffracted beams. On two meters when stopping the rotation none of the beams have measurable power meters resolution is 1mw. The beams are large you can see my hand in one picture for reference. Also you can see how the center main beam is well overhead. I am just interested in the diffracted beams safety.

Thoughts and opinions please, or info on how to better measure. It is 1w total leaving the beam table.

[m0f]

If I understand correctly it's a single beam through a rotating grating, not scanned through a grating ? If that's the case, the measurement should be accurate. As the beam is split into many by the grating, and divergent, they should be fairly low power especially towards the outsides. If it is scanned, probably the only way to be sure about the measurements is to put a static beam through the grating and measure the results.

[polishedball]

If I understand correctly it's a single beam through a rotating grating, not scanned through a grating ? If that's the case, the measurement should be accurate. As the beam is split into many by the grating, and divergent, they should be fairly low power especially towards the outsides. If it is scanned, probably the only way to be sure about the measurements is to put a static beam through the grating and measure the results.

That is correct it is a single beam off a rail, into the spinning diffraction mirror bounced back. You can see the thinner solid white beam that hits the effect on the left side in the video.

[mixedgas]

If the beam is spinning in a circle and you know within a few percent the rep rate and actual power, I can post the math for a circular scan in a day or two.
You'll need a small area photodiode and a oscilloscope. I'm recovering from my jet lag. I'm done with the net for a day. 15 hour flights beat you up pretty bad.

Steve

[m0f]

Couldn't you just count it as a static, since it's moving so slowly anyhow and likely won't always be moving the same speed. The limit will be a bit lower but probably not enough to be worth all the extra math

[norty303]

You should measure it as a static unless you've got some sort of scanfail interlock on the rotating mirror.
Worst case scenario and all that jazz

The zero order beam is the one to go for, but it sounds like you've already done that and confirmed it's ok.

I think Steve's suggestion is relating to a rotating mirror with a tilt on it so it projects a cone.

[polishedball]

The zero order beam is always overhead. I didn't measure it, only tried to measure the static defracted beams when I stopped the rotation.

Ah the cone effect, that is position 1, position 8 is the machida. Basic, but pretty cool setup for the basement and it is all controlled manually, or by LSX.



And I added another bounce send in beams back forward, from just the overhead line grating.



Thanks for all the input so far.

You should measure it as a static unless you've got some sort of scanfail interlock on the rotating mirror.
Worst case scenario and all that jazz

The zero order beam is the one to go for, but it sounds like you've already done that and confirmed it's ok.

I think Steve's suggestion is relating to a rotating mirror with a tilt on it so it projects a cone.

[Galvonaut]

I second the static beam measurement suggested by Norty. It saves lots of mathematics, expensive sensors and scan fail devices.

Keith

[buffo]

You should measure it as a static unless you've got some sort of scanfail interlock on the rotating mirror.

Exactly. Not to mention the fact that the grating is turning so slowly that you won't see any appreciable change by calculating it as a moving effect anyway.

2.5 mw/cm^2 is the limit. If the beam is smaller than ~ 7mm in diameter, then the entire beam falls within one square centimeter, so all you need is the power measurement. If it's over 2.5 mw, you're hosed.

(Note that this assumes you can never have more than one beam entering the eye at any given time, which seems plausible based on the pictures John posted.)

Adam