Laser Safety

[norty303]

Do not put too much emphasis on James' tool. It is part of the arsenal of laser safety but not a magic bullet. The fundamentals of show analysis are the same regardless of whether you have this software. It is heartening to hear you have been conversing with James already and that he has told you pretty much what we have here.
There are no real short cuts with this unfortunately.

[norty303]

If you have an iOS device, download James' NOHD or Laser Show Safety app and play around with parameters to get feel for how changes in parameters such as diameter, divergence, power and exposure timeframe affect the NOHD and MPE values.

[m0f]

I definitely second the recommendation on James' Iphone app, it's great for getting a rough estimate of what kind of divergence you'll need for your distance, and so works as a great tool for choosing the appropriate safety lens for your intended distance. From there you can fine tune with measurements. And as mentioned definitely a great tool for getting a feel for how each parameter affects the result.

Your divergence can be measured easily enough, so I'd start with that. And if you do get a safety lens set, you can measure your divergence with each lens for future reference. Which can then be plugged into James' tool, along with measured power to get an estimate of safe distance.

If you can only afford to buy just 1 or 2 safety lenses rather than a set, initial beam size of each wavelength and divergence can help you calculate a rough idea of how each lens will affect the beam. Generally speaking, I find initial beam size seems to affect things the most. So when using the safety lenses, particularly the higher powered ones, the results are much better when the initial beam sizes of each wavelength match up closely.

[gandalfthegrey]

I have the app on my iPhone already. @2.5W Beam Divergence 1.5mr, the NOHD is a very long way away @ 236m (774.1ft). When I saw that it seemed very far away which is when I got on the case to see whats going on... All the input here is very helpful. So thanks all.

[White-Light]

As said several times, divergence is your best friend.

Speak to Pangolin with the additional specifics ie distance to audience and beam diameter and they should be able to recommend the correct lens as a ballpark, for your application.

If you have multiple scenarios, then you might need more than 1 lens.

At a recent trade show Pangolin tamed a Kvant 1.6W laser (from memory), to be safe from a distance of 5m at full power using their lenses!

The other useful facet is if you're using their software, you can combine a lens with a BAM (Beam Attenuation Map), if you're unable to use a lens to fully render the output safe.

However, the key thing throughout all of this is measurement. Take James' course when you can afford to and take advice on the right power meter for measuring MPE as assuming values is a dangerous game to play. Lasers often don't match their stated spec eg. My 2.1W Kvant makes a measured 2.8W! So to assume it's factory value would put you over MPE.

[gandalfthegrey]

does anyone know roughly how much I'd expect to pay for a meter? I already have the price for the lenses. Thanks

[gandalfthegrey]

Update!

I have some more info if it helps but am still waiting to hear if a scan fail device was fitted

Divergence / diameter

Red 2mRad/ 2mm dia
Blue 2mRad/ 3mm dia
Green 1.2mRad/ 1.5mm dia

Thanks

[norty303]

If you can project a static beam then there's a pretty good chance no scan fail is fitted

[gandalfthegrey]

@Laser Wizardry. I',m quite concerned you think my unit is probably a cheap Chinese RGB laser, because the red is 1000mW of 650, like I said it was built in the UK and I thought they were reputable. What should the red be please? I am only just staring to understand all this. Would I have any justification for sending the laser back?

[norty303]

650nm red is not really the red of choice these days, although a perfectly ok product to supply. They tend to have very square beams, wider divergence and less visibility compared with the shorter wavelengths, but budget will dictate a lot of that.
Maybe you got a good discount because it used the cheaper/less trendy/popular red unit. We don't know the circumstances of the sale unfortunately, but with lasers it pays to know what you're buying to ensure you get what you expect/hope.