Change to US rules - how many of you missed this? (I did...)

[Doc]

As Buffo stated; I interpreted it as meaning if the beam can possibly come in to contact with a person due to mechanical or other failure; you need scan fail interlock.

[greenalien]

Thanks Doc

[mccarrot]

I also found this tekst:
for projectors that use solid-state lasers, it might be argued that between the fast and complete extinction offered by the laser diode driver itself, coupled with the fact that the projector interlock actually removes the power from the laser diode drivers, a shutter is therefore not needed

http://www.laserist.org/laserist2008...onnections.htm

Is this still applicable?

[mixedgas]

I also found this tekst:
for projectors that use solid-state lasers, it might be argued that between the fast and complete extinction offered by the laser diode driver itself, coupled with the fact that the projector interlock actually removes the power from the laser diode drivers, a shutter is therefore not needed

http://www.laserist.org/laserist2008...onnections.htm

Is this still applicable?

Its defense in depth. Ie the more passive mechanisms you have to protect your viewers, the better off you are.

You need to frame the need for the master shutter into one context, most people in the US who are professionals have their beams masked above the audience as a condition of their manufacturers report and variance, the theory being if the shutter fails, the masking stops the beam from hitting the crowd. Our two meters horizontal and three meters vertical rule.
Our projector design should inhibit the beams from touching the audience
with the masking, and if that fails, you have the shutter.

In Europe where you are EXPECTED to audience scan, you have a different situation.

Therefore, when you audience scan, you DO NOT want to depend on a Euros worth of Far Eastern chips to ensure your laser can be shut down. Lasers can fail on, just as much as they fail off.

The mechanical shutter on its own circuit with its own keyswitch, and not on DMX or your control software is really a critical part of laser safety. This is why the loops are wired normally on, in a interlock loop, too.
Redundancy, you can shut off no matter what else fails. Its a good thing to have the shutter, as by definition, you do not have the mask.

Steve

[JStewart]

The requirement for a 'Scanning Safeguard' for the purposes of 60825-1 is intended to cover the situation where you have a laser product that produces a lower 'accessible emission' by using a scanning system in its normal operation than would be present if the scanning system in the product were to fail or not be present. An example would be a barcode scanner, where a Class 3R source maybe used, but when the product is operating normally the actual 'accessible emission' is Class 2; therefore allowing the product to be classified as a Class 2 Laser Product. Therefore in this instance, if the product using a higher power source is classified on the basis of its scanned emission, then there needs to be a suitable scan fail function to prevent the laser product from emitting the higher Class 3R source emission levels under a fault condition.

Applying this to laser display products, most products will be either Class 3B or Class 4 by design. There is no '60825-1 product standard requirement' to include a scan fail monitoring device in these products if in close proximity their emissions are always going to remain in the these higher classes even when scanned. However there would be an operational recommendation to use such a device for audience scanning applications, where normally there is a requirement to ensure that the emissions hitting anybody in the face would be Class 2 levels.

Hope this helps,

James Stewart

[mccarrot]

Yes, thank you.

If you have a scanfail with double redundancy is there still a need for a mechanical shutter?

[allthatwhichis]

I think with what we are doing there is always a need for a mechanical shutter; especially if you are trying to be as safe as you can be. It may not be needed for a varience, but to put forth as much effort as you can to be safe, I would, and will, install a shutter.

[buffo]

If you have a scanfail with double redundancy is there still a need for a mechanical shutter?

Under IEC rules? I don't think so, but I'd check with James to be sure.

But if you're certifying strictly under CDRH rules, then yes, you need a shutter - period.

More to the point, a shutter is just a good idea in general for a projector. (No matter what the regs will allow.)

Adam

[Jem]

A shutter is a good thing as (amongst other things) it allows you to warm up the lasers without having any output

Jem

[JStewart]

Under 60825-1 there is no specific requirement to put 'mechanical shutter' into the Laser Product that is Class 3B or Class 4. Only the term 'Beam Stop or Attenuator' is used, which allows some degree of flexibility in how you achieve the intended purpose of preventing human access to the beam.

Now if you are 100% certain that you have reliable alternative method that can terminate the beam output with, other than a mechanical shutter, then the standard allows you to go with that option. From experience though relying on the modulation inputs having no signal or not being connected is not 100% reliable. Therefore with the relatively small given cost involved, like others have already mentioned, I'd always recommend using a mechanical shutter, and better still, one that will always fail safe.

Remember, the safety features set out in 60825-1 are a list of the minimal features required for a particular Class of laser product. The standards are made up from international consensus at the time of publication, and are under constant review. If there are features that you feel will make your product safer, then manufacturers are free to add more levels of safety.

James Stewart