pangolin safety lense?

[Pangolin]

Whilst it is possible to have faster than 1ms response, I think that impact on genuine patterns may be too adversely affected.

Actually no. When we played around with dwell time years ago, we found no visible difference at 1.5 milliseconds, and started to see some visible differences in shows, here and there at 1 millisecond. But that was only in some shows and in some parts. I suspect 1 millisecond is a better number to use for most people. Plus, for a real installation or tour, the show programming *should* be done specially for that installation or tour, so the scan-fail should not be doing anything to interfere with that show content.

For a theme park in Japan, we actually had to adjust this all the way down to 100 microseconds, and then had to adjust the minimum velocity all the way up as high as it would go. This particular theme park wanted the laser projector to be safe even if someone put their face around 10 centimeters from the exit aperture of the projector, even though spectators on the theme park rides were tens of meters away. They wanted to do this because they wanted an extra, added, added, added level of safety that they could defend. (In addition to PASS and a laser projector, additional things were used to help reduce the exposure -- additional things I can't talk about. But if you envision a projector with PASS and one of our lenses, you'll be in the right ballpark of what was done.)

The whole operation (including my own adjustments and an entire review of the PASS system) was being continually examined by a company called Exponent, who evaluates risk for large companies. They're also the company that got involved when news of Toyota brake systems were failing (something that was never proven by the way -- and I confidently drive a Toyota)...

Bill

[The_Doctor]

For a theme park in Japan, we actually had to adjust this all the way down to 100 microseconds, and then had to adjust the minimum velocity all the way up as high as it would go.

That's what I had in mind.. By (very) crude analogy, it is like raising a shutter up to prevent the beam going too low into a crowd, then writing the show so it never hits the shutter. That way, with software taking care of timing, the scanfail does nothing unless the software fails. And presumaby the power (and brightness) can be increased in a show that does not have critical demands on extreme safety limits.

[Pangolin]

By the way, I wanted to say that that the additional comments from James really helps to fill in the blanks. I felt my post was already long, even though it lacked detail. I wholeheartedly agree with everything James wrote.

[JStewart]

To hopefully help clarify a couple of questions raised:

Why 1ms? - There is no particular reason why 1ms has to be used. It is simply a convenient figure, with a 1ms exposure equating to an MPE of 10mW per square centimetre. It also tends to be below the trigger threshold for the majority of ‘sensible’ scanned effects that could be pointed at an audience.

It is certainly possible to effectively use devices that trigger at faster velocities.

Sadly, just like the majority of laser systems, (and I’m talking some of the pro systems too), that have emerged in the last few years all quoting a divergence of ‘0.8mr’, scan-fails seem to all be converging to a mythical 1ms reaction time for some reason. Such figures look good on product datasheets, but like divergence, which can be drastically different from the published spec in real life, such claims have to be tested. In any event, 1ms may still be too long to poke at someone’s face.

The 7mm diameter aperture – This dimension is used because the safety standards consider this to the size of a ‘standard’ dark-adapted eye. The MPEs are also based on this assumption.

Dazzle – light may enter the eye for only 1ms (or any other short duration you wish to choose), but the after effects caused through saturation of the photoreceptors lasts considerably longer.

James