Annex 4: Optical radiation from lasers

The biophysically relevant exposure values to optical radiation can be determined with the formulae below. The formulae to be used depend on the wavelength and duration of radiation emitted by the source and the results should be compared with the corresponding exposure limit values indicated in Tables 4.2 to 4.4. More than one exposure value and corresponding exposure limit can be relevant for a given source of laser optical radiation.

Coefficients used as calculation tools within Tables 4.2 to 4.4 are listed in Table 4.5 and corrections for repetitive exposure are listed in Table 4.6.

Notes

dP	power, expressed in watts [W];
dA	surface, expressed in square metres [m²];
E(t), E	irradiance or power density, the radiant power density per unit area upon a surface, generally expressed in watts per square metre (Wm^-2 ). Values of E(t), E come from measurements or may be provided by the manufacturer of the equipment;
H	radiant exposure: the time integral of the irradiance, expressed in joules per square metre (Jm-2);
t	time, duration of the exposure, expressed in seconds [s];
λ	wavelength, expressed in nanometres [nm];
γ	limiting cone angle of measurement in field-of-view, expressed in milliradians [mrad];
γm	measurement field of view, expressed in milliradians [mrad];
α	angular subtense of a source, expressed in milliradians [mrad];
	limiting aperture the circular area over which irradiance and radiant exposure are averaged;
G	integrated radiance: the integral of the radiance over a given exposure time expressed as radiant energy per unit area of a radiating surface per unit solid angle of emission, in joules per square metre per steradian [Jm^-2 sr^-1].

Table 4. 1 Radiation hazards Table 4. 2 Exposure limit values for laser exposure to the eye – Short exposure duration < 10 s Table 4. 3. Exposure limit values for laser exposure to the eye – Long exposure duration ≥ 10 s Table 4. 4. Exposure limit values for laser exposure of skin Table 4. 5 Applied correction factors and other calculation parameters Table 4. 6 Correction for repetitive exposure