NOHD & Eye-Safety Calculator
Eye-safe is a claim, not a measurement. The measurement is the nominal ocular hazard distance: the range at which the beam has spread far enough to drop under the maximum permissible exposure. Inside it, a direct hit is over the limit; outside it, it is not. Three numbers set it — optical power, divergence and the beam diameter where it leaves the housing — and any seller who has them can print the distance. This works it out, and sizes the eyewear for where you actually stand.
Optical output, not draw. Run a plate rating through the optical watt calculator first.
450 blue, 520 or 532 green, 635–660 red, 808–980 invisible near-infrared.
A collimated pointer runs about 1–2 mrad; a self-levelling line head is far wider.
Measured where the beam leaves the housing.
The blink basis assumes a visible beam and a working aversion response. It is the wrong assumption for an alignment beam you are deliberately looking down, and above 700 nm it does not exist at all.
Optional — where you actually stand, so the eyewear can be sized.
Working the other way, from a machine’s plate rating down to its true output, is the optical watt calculator.