I think we lazed a projector to death

[The_Doctor]

A brief encounter with Marilyn Monroe explains that there is more to it than that. Search this forum, you'll find it.

[kecked]

10-20W.....That statement just demonstrates the lack of care people take with OTHERS eyes.

[silentgloves]

10-20W.....That statement just demonstrates the lack of care people take with OTHERS eyes.

Right? Entertainment should not involve physical harm. Just because someone "has" done it, doesn't mean it's appropriate or safe.

[mihai1880]

Personally I can say I didn't have just a brief encounter with lasers. I have done hundreds of shows, a lot of them with audience scanning, and at more then 80% of them I was actually in the front of house, so in the scanned audience. Using a high powered laser for audience scanning does not mean to have a projection zone set up over the people's eyes and do high power single beams.
By doing single colors except white, takes the total power to an average of 30%, by projecting smooth shapes without hot points, adding movement, that also lowers the power.Having the projection zone just with the lower end terminating in the audience and as far as possible from the laser projectors, and adding attenuation maps, that also makes it less brighter.

It's all up to the operator. For example I wouldn't be comfortable using a laser like in first photo Randomseed posted. It looks like the DJ is about 1-2meters away from the laser and right in the middle of the projection zone, even if the power is set to under 1W, if he turns around for any reason it's definitely not good for him.

Anyway, this thread is about something else. Video Projectors are a lot more sensitive then the human eye when it comes to lasers, it's been reported that powers as low as 50mW can damage them so even if the estimated power was at 75%, 900mw is more then enough to do the damage.

[norty303]

So much seemingly misinformed comment I this thread. Suffice to say that safe audience scanning is all about irradiance and only partly about actual power output.
You cannot evaluate how safe a show is knowing only how much power the module is making.

[norty303]

Oh, and it's not just DLP projectors that are susceptible to damage

[Randomseed]

Point taken but for ref that one was through scrim at about 20 ft running under 150mw/color. Overspill was minimal to none (terminated in the booth) except the artists themselves who where all prepped beforehand. 90% it was running text terminating near the artists feet. DJ scanning sure, crowd scan no way hose'. Other than the performer, projector, or possibly a person mounted to the ceiling nobody was in harms way.

[mixedgas]

Back when I worked for the university, a grad student fried a vidicon based camera with 5 mw CW from a HENE. He just happened to have a very good lens on the camera.
Probably the low end record, but it shows it can be done. Once I told him it was toast, he went back and carved his initials in the video. Silicon is a bit tougher then the Lead Oxide used in the Vidicon, but not much.

Steve

[buffo]

I've killed two CCD's in small point-and-shoot digital cameras (albeit older ones with lower resolutions - max of 3 megapixels) by scanning the beam from a 100 mw dpss green across the lens at 30Kpps. This was at distance of about 12-15 meters!

Electronics of all kinds can be damaged even by very low power beams. Cameras, DLP projectors, and LCD projectors are especially sensitive.

As for audience-scanning, if the laser operator is measuring the irradiance at the closest point of audience approach prior to each show and is otherwise properly trained in the specifics of audience scanning safety, I don't have a problem with it. (This also assumes the operator has an approved audience-scanning variance, if he is in the US.)

But far too many people simply say "I've been doing shows for years, so I know what I'm doing." Yet when you ask them how to calculate the MPE, they have no idea how to do it, and then you learn that they don't even own a meter with which to measure irradiance nor do they have any sort of scan-fail interlock on their projector. Then you ask to see their variance and they give you a blank stare...

Yeah, I have a problem with those type of people...

Adam

[planters]

When we were at MIT last winter for a mini-LEM, some of the" just walking by" grad students who were smart enough not to immerse themselves in the beam paths, immersed their phones into the beams to record the experience. One of the students remarked on the drive home that he had random dead pixels spread over the camera. He thought it was cool.