Laser Power Meters

[wmodes]

Found it: http://www.lvrlimited.com/lasersafety.htm

[norty303]

http://www.lvrlimited.com/ios.htm

[wmodes]

Super helpful. The only thing I was confused about was the Duration value. Murphy and Makhov say the highest exposure (per pulse) that can be assumed is 250mS. But presumedly, during a show, the laser will be scanning. But the Level 2 audience scanning proposal already takes this shortened exposure time into account, and therein lies the additional latitude for a 10x (100 mW/cm2) show. I don't want to calculate safety in a way that takes the limited exposure time while scanning into account twice (double dipping).

What value should I use for the exposure if the expectation is that the laser will be scanning (and has reasonably fast scanfail circuitry).

Wes

[norty303]

If you have scanfail (which you should) then you use the response time of that, as it will be the maximum duration a person could be exposed in a worst case scenario (which is always what we are calculating for, not what our typical scanning show exposure would be)
If you don't have scanfail, then you must use the aversion response time of 250ms.

Note that you should be using 1xMPE as the 10x of the paper is just a proposal. Reduced exposure times below 250ms allow increases, but not significantly (e.g. 1ms max exposure only means 4x)
10ms only allows 2x

As you're seeing, scans with raw beams, even using very fast scanfail, doesn't really buy you much in terms of usable power.

Add in a diverging lens such as Pangolin's SafetyScan, and the impact is significant in terms of power and brightness.

[wmodes]

I was assuming that I would be doing a series of things to make audience scanning safe(r):

• Position the laser as far from the audience as practical
• Reduce the output power of the laser
• Use a diverging lens
• Use a scanfail device

Since most of the lasers, I've been looking at have <3mm beam diameter, I'll likely be using a diverging lens. Is there a diverging lens that is made for the full output (not just half like the SafetyScan?

I know I've wandered a bit off subject for my original post title.

Wes

[norty303]

Are going to be in a venue with a balcony or something? I'm trying to understand why you would want a full lens.
If you do, try contacting Pangolin, I seem to recall something about maybe being able to supply full lenses.

[wmodes]

It will be overhead mounted.

[norty303]

By overhead, do you mean pointing straight down? Will you get enough spread like that, or is it going to be quite high up?
And will people be actually looking up at it, or is it more to put patterns on the ground?

[wmodes]

It will be relatively high. At 26 feet, a 70 degree scan angle allows me to project on a 36 foot diameter area.

[jors]

So, anyone can point an affordable meter suitable for mpe? I've read lots of posts about mpe and don't know which meter yet