You still need a laser power meter to do that safely, and you cant trust the filter to be what is specified on the label. Low cost Optical coatings and commercial grade filters are rarely checked at the factory for performance, let alone performance across 3 wavelengths. They might do twenty coating runs of sixty pieces before they stop and take a witness sample for measurement.. Did I mention that many coated filters can be angle sensitive?
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I've seen "one watt" RGB lasers ship at two point four watts, too.. You cannot assume you have roughly one Watt of Laser Power.
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It is best to turn down the diode drive. Then obtain a proper power meter and measure the results. You only have one set of eyes, and they are not replaceable.
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There is a good reason that no one uses ND filters for audience scanning commercially.
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I'll put a plug in here for Pangolin's "Safety Scan" calibrated lenses to increase your divergence, too. While one lens will not make you "safe" at very short distances, it will go a long way towards reducing your MPE.
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YOU HAVE TO MEASURE THE MPE BEFORE YOU SCAN YOURSELF OR OTHERS.
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Steve
Qui habet Christos, habet Vitam!
I should have rented the space under my name for advertising.
When I still could have...