New Laser MPE Limits published

[The_Doctor]

For what little it's worth:

Part one.
First, laser diameter at 1234 metres, by transposing the Wikipedia expression for divergence gives 2.0353 metres as beam width. Area of illumination is 3.253471 square metres. 25W spread like that is 7.6841 W per square metre. 7mm pupils have area 0.0000384845 square metres. Ratio of areas is 0.0000118, which multiplied by 25W is 0.295 mW. So Marylin is eye-safe, and the exposure class at her face is class 2M because the beam is so wide, and because if it lights her up it must be visible.

I suspected she was eyesafe anyway just from having seen how big a beam at 0.5mr gets after just a few hundred feet. By playing the man, not the game, as good chess players apparently do, I assumed his bunch of youthful geezers is a very studious gathering who know exactly what they are doing, despite his attempts to make us assume they are dangerous morons, so the numbers don't surprise me.

Part two.
25W must be spread over as little as 50 cm2 to get as much as 0.5W per cm2. Diameter would have to be 7.9788 cm. Subtract 0.08 cm at aperture, so 0.078988 metres used in transposed Wikipedia divergence expression gives a distance of 47.8715 metres for burn risk.

Part three.
I quit at this point. Here's why:
http://www.optique-ingenieur.org/en/...ontenu_09.html
If wavelength is important there, they didn't say, you presumably have to plug in all that MPE bit got from somewhere else as if there isn't enough unwarranted opacity there already! I went as far I was willing to. No-one's ever going to have to run crying from my lasers. And not everyone on PL is trying to act like a daredevil flying a plane under a bridge. Come to that, not everyone admires the fools who do. When I take risks I prefer not to subject others to them. So I may die alone one day. But who doesn't?

[White-Light]

There is already an easy way of setting MPE - Some pc based power meters allow you enter in the sensor diameter and once this is set, can be put into mw cm 2 display mode. They will then autoatically display the read power in mw cm 2 with no calculation needed on behalf of the user as the meter calulates it internally on the fly.

So all you need to know is your published sensor diameter and all you need to do is ensure the meter is in that mode and the beam fully covers or overspills the sensor. Almost idiot proof.

[The_Doctor]

Excellent. Now if the big show guys want to impress the legislature, all they have to do is the mother of all group buys and build the damn thing for everyone.

[White-Light]

It can already be bought off the shelf for less than a physical meter - around £800 including the sensor (although the price does depend on what sensor its paired with).

It's being evaluated on my behalf atm and if its any good I was thinking of buying one and posting a review here.

I haven't mentioned it before because I'm awaiting the verdict from those in the know.

[Laser Electronics Ltd]

Hi Doc
I think on this post you missed the point I was trying to make. There are current products available that exceed the MPE for home use that are available, lets get some people on board like Casio or Sony to revauate the original bunny data. They have the budget to do this.
We as individuals don't.
I'm not doing this for profit, everyone who knows me, knows that I want to expand technology and create new concepts.
We do however have to ensure that commercial products that can cause detrimental health issues, that could be attributed to our industry are highlighted.

[Laser Electronics Ltd]

Hi James
The AOR directive sets out in the onset to cover visible, Uv and Ir.
The mandate for this was set back in 2005.
I agree this was a backstep, but the HSG 95 was always about safety, I have never said it was about crowd scanning.
The HSG 95 was a guideline set up using Data based on Ion laser tech and not point light source emissions.
However I'm sure with all the work that's being done and the new articles that have been made available regarding the collateral radiation emissions, we'll see some new values soon.
I am with everyone on here in regard to the blatant disregard for safety that happens sometimes.
This is purely down to some people using technology they don't understand.

[The_Doctor]

Hi Doc
I think on this post you missed the point I was trying to make. There are current products available that exceed the MPE for home use that are available, lets get some people on board like Casio or Sony to revauate the original bunny data. They have the budget to do this.
We as individuals don't.
I'm not doing this for profit, everyone who knows me, knows that I want to expand technology and create new concepts.
We do however have to ensure that commercial products that can cause detrimental health issues, that could be attributed to our industry are highlighted.

Sounds good to me. If Casio (and of all firms, those guys could really do this) make some cheap way to get an MPE meter together for general public use, it can help. I won't repeat myself, I'll just say that 800 quid is a hell of a price for guys who'd rather buy Chinese lasers for cheap, and are scared of spending over fifty bucks on a diode driver. It needs to cost about the same as a good first aid kit, or a small CO2 fire extinguisher at most. We could argue all day that priorities are not what they should be, but human nature being what is is, maybe it's easier to build that box. Eventually I'm sure someone will, too. If it happens before governments start shoving people around, so much the better. More freedom that way.

[White-Light]

There is always a laser check (Coherent) or some of the more diy meters. The problem then comes though not from using it but understanding how to make the calculations. Anyone can read the power, very few can calculate MPE, myself included.

I do agree a £100 MPE meter that you simply chuck into the beams and get mwcm2 values out would be nice, but even then you'd have to know to fill /overfill the whole sensor (I wonder how many home users would take a reading with a partial sensor if the beam was too narrow and they didn't have lenses?), plus I've not seen any indication that a cheap accurate mass produced meter is even possible for those sort of prices. Even 2nd hand commercial sensors without a meter seem to come in at £200-500 on ebay depending on the sensor.

If Casio could come up with the MPE meter equivolent of their maths calculators, everyone would be laughing. I think the issues though are low volume, cost and the fact that they've never seemed to want their diodes to be used in lasers in the 1st place - I seem to remember users posting stories of them allegedly increasing security in their cinema projectors several times to try to prevent harvesting, things such as security screws and even epoxies.

[JStewart]

The AOR Directive contains two sets of limits; coherent and non-coherent optical radiation. The 'coherent' limits are of course for laser. The exposure limits published in HS(G)95 didn't exclusively come from ion laser sources. They are the standard coherent limits derived through ICNIRP at the time of publication, which, slightly confusingly, also cover UV,vis, and IR.

Re Casio and the like, I'm still not really understanding why they would have any interest in getting involved with a problem that has nothing to do with the intended use of their own products. The risk associated with devices that use laser sources to create a homogenised output is completely different from that of a flying-spot projection device. This is why laser projection manufacturers have teamed up to form their own association, and there is separate IEC laser safety standard in the works for this type of device.

Maybe Laserscope should be invited, because some people poorly hack their products and sell them as laser show projectors... The point being, it is not the component manufacturer, (and less so, when it's a finished product being bought and ripped apart for components), that has the responsibility. It is the manufacturer/supplier of the final product, that makes it available for market that has the responsibility to ensure it incorporates the minimum safety features and user information.

[Laser Electronics Ltd]

Hi James
Find below the replies to your post, not in chronological order but in relevance.

If you take a current Casio video projector that uses 20+, 3 watt 445nm laser diodes as their primary light source that is spread over an aperture of 3cm, do you not think the power density is greater than the current HSG95 regs, and have you actually measured it.

This is a product that is commercially available, I was only making the association that people use these components because they have been made available commercially.

Your comment about LaserScope is noted, but is not relevant, they have never made a product that is commercially available to the general public, they have always produced equipment over the latter years for medical and research.

The HSG95 as you know was an update to the PM19 document, there was no new research included except from the Military Laser Safety committee that was implemented regarding the use of Q-Switch/Quasi Pulsed laser and Point Emission Light Sources from data researched from 1993-1994.