Senior Member
To be fair, the new '10xMPE' guidelines have sort of said that having gathered some decades worth of evidence, it's possible to safely crowd scan at higher than previous MPE levels. However, that doesn't get away from the fact the OP doesn't actually know what his MPE is from his projector, or have any device to cope with scanner failure when crowd scanning.
Senior Member
Movement through the crowd yes as it spreads the exposure time over the whole audience and not one section. However, this just reduces cumulative heating effects from affecting one section of a crowd from a laser already within safe MPE limits.Originally Posted by pimm87
However, scanner movement in terms of repetition does not spread the output. If you have a fanned effect you have a pencil beam scanning left to right at x speed. You don't have a wide fan with the power output spread along its width. Every part of that fan is at full power. Whatever the speed of the scan you still have a pencil tight beam and your exposure to the beam is the duration the beam takes to pass the eye times the number of repetitions. Or to put it another way, the duration the pencil beam isn't on the eye is the time taken from it passing the eye to rescanning onto it again - milliseconds per pass. Compensate by increasing scanner spead to reduce the time spent on the eye and itsalmost entirely cancelled out by the fact that there's a corresponding increase in repetitions of the scan in any given time period. So compared to a static beam there is some reduction in exposure but its absolutely miniscule and especially when lasers of Laser IV or above can cause eye damage in only milliseconds itself. Have a high power fan in the audience for 4 secs and their exposure is potentially 4 secs minus the milliseconds between scans across the eye times the number of scan repetitions. Whatever way you look at thats still seconds of exposure to a beam that could potentially damage in thousandths of one second.
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