USB Scannersafety

[mccarrot]

assuming a beam diameter of 1cm^2, what is the maximum laser power that this device can safely blank before eye damage occurrs?

What?? MPE calculations got nothing to do with a scannersafety, except it must work as fast a the pulse time you used in the calculations.
The simplified approach uses 1ms as time, this scanfail is 2ms. But difference in MPE is very small between 1ms and 2ms



This device can work with any type of laser and any type of power, upto 6 colors... for most of us 6 colors is enough (I have not seen yellow in any of your projectors yet )

This device makes sure a beam can never be longer than 2ms (or 20ms depens on the setting) at one one location or it will blank the lasers.

This will make sure you never get a static beam in the audience due to a galvo PSU braking down, a galvo braking down, bad connection of a galvo cable, bad ILDA cable, a bad designed show, a bad operator, etc etc etc.

A scannersafety is MANDANTORY in any high power laser used for audiance scanning.

If you are not audience scanning and you are to cheap to invest 115 euro in safety you MUST use a mechanical cover in front of you aperture to block the audience so a beam can NEVER reach the audience.
A steel plate in front of your aperture is a cheaper solution for sure

[drlava]

Hi,
This is all new to me, can you show an example MPE calculation with 2ms static pulse?

It just seems to me that 2ms of 1W direct into an eye I would not feel safe (worst case scenario), so at what laser power is 2ms safe?

edit:
sorry, maybe I misunderstand the purpose of the device, is it to minimize, not eliminate damage.. then OK 2ms greatly minimizes possibility of damage, but damage is still possible.

[mccarrot]

I say again, a scannersafety got NOTHING to do with MPE calculations.
It will only assures you stay below MPE in case of a problem (see 2 posts back)


MPE is directly related to the time of exposure, using the formula of 1.8 x 10^-3 x t^3/4 Joules/centimeter squared. Solving this for a "t" of 1 millisecond ( a scanned beam this is pretty conservative as a normal effect is between the 20 and 500 microsecond) gives a result of 10 millijoule/cm^2, which is equivalent to 10 milliwatt/cm^2 for the 1 milisecond of exposure.


for a "t" of 2 milisecond gives a result of 8,5 millijoule/cm^2, which is equivalent to 8,5 milliwatt/cm^2 for the 2 millisecond of exposure. (in case of a problem)

(To do this with the scientific calculator provided with Microsoft Windows, enter 0.001, press the X^Y key, enter 0.75 (equivalent of 3/4), press *, enter 0.0018, press /, enter 0.001, and press =.)

So as you can see the increase from 1ms to 2ms in the calcuation will increase the exposure of less than 1.2x.

Because MPE calculations are pretty conservative (no accidents have been reported at 100x MPE shows) 1.2xMPE is not a big issue in case of a scanner failure or other problem.
But in the US where it's simply not allowed to scan above MPE you should not go higher than 8,5mw/cm2 at the closest point in the audiance.

In europe these MPE safe shows are simply to dim, therefor we (the laserist with sense) use the 10x approch, where we have 100mw/cm2 at the closest point the audiance.

To measuere this you need to measure the power at the closest point in the audicance and increase the divrigence or lower the power using the Beam Attenuation Map.

If you do not have a power meter which can measure mw/cm2 you can use the following formula:

I = p/(π[d/20]²)

Where I is the average intensity in mW/cm², p is power, and d is the diameter of a round spot in mm.

Its best to use a 7mm aperture in front of the detector, as this is also your pupil diameter.

Its all so simple...

[mccarrot]

Hi,
This is all new to me, can you show an example MPE calculation with 2ms static pulse?

It just seems to me that 2ms of 1W direct into an eye I would not feel safe (worst case scenario), so at what laser power is 2ms safe?

edit:
sorry, maybe I misunderstand the purpose of the device, is it to minimize, not eliminate damage.. then OK 2ms greatly minimizes possibility of damage, but damage is still possible.

It will eliminate damage in case of a scanner failure or other problem. (saying you use 8,5mw/cm2) thats why a scanfail is so important on high powered lasers.

[edison]

Thanks for making everything so clear Mccarrot I,m stil suprised that you can mount a projector without safety to a ceiling of a club with couple of watts and point it directly in the crowd without being checked by some sort of organisation in the netherlands. I also find it strange that you can buy a high powered laserprojector without scanfailure. Its like selling a car without safety belts.

[drlava]

mccarrot, thank you for the great explanation, I think this should be in the user's manual, as it is important to make sure users understand the limits in general

I did understand that this device does not ensure a safe show, only that a safe show stays safe in case of a failure.

So, this device will ensure viewer safety (in case of scanner failure) for projectors that emit a maximum crowd irradiance of 8.5mW/cm2 or, using 10x MPE approach, 85mW/cm2.

similarly, a theoretical expensive scanfail device that has a response time of 100us could theoretically only raise the irradiance maximum to 18mW/cm2 (180mW/cm2 at 10x) assuming that the rest of the show fell within the safety guidelines.

[mccarrot]

similarly, a theoretical expensive scanfail device that has a response time of 100us could theoretically only raise the irradiance maximum to 18mW/cm2 (180mW/cm2 at 10x) assuming that the rest of the show fell within the safety guidelines.

No, in the USA, and many other countries (not mine ) 10mw/cm2 is not allowed, so a faster scanfail than 1ms makes no sense.

The only system I know which is faster is PASS, but this will cost you more than 500USD

[Gento]

My authoritative (Referenz) Show to the Safety is Betternow (Pangolin)

Besides, the Safety intervenes more than >3000 sometimes. @30K Speed

Luckily, but one has black holes in augen.

Gento

[kl79]

Count me in for one board....thank's !

[buffo]

mccarrot, thank you for the great explanation, I think this should be in the user's manual, as it is important to make sure users understand the limits in general

Maybe the people that are buying it for use in an audience-scanning show ought to be sure they understand what scan-fail protection is really for, before they ever consider doing audience scanning shows...

So, this device will ensure viewer safety (in case of scanner failure) for projectors that emit a maximum crowd irradiance of 8.5mW/cm2 or, using 10x MPE approach, 85mW/cm2.

Exactly, because if you're above that irradiance level your show isn't safe - period. A scan-fail board won't make an unsafe show safe. It is only there to ensure that an otherwise safe show will remain safe in the event of a scanner failure. That's all.

Adam