Directive 2006/25/EC of the European Parliament and of the CouncilShow full title

ANNEX II U.K. Laser optical radiation

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 the Tables 2.2 to 2.4. More than one exposure value and corresponding exposure limit can be relevant for a given source of laser optical radiation. U.K.

Coefficients used as calculation tools within the Tables 2.2 to 2.4 are listed in Table 2.5 and corrections for repetitive exposure are listed in Table 2.6.

Notes:

dP

power expressed in watt [W];

dA

surface expressed in square metres [m²];

E (t), E

irradiance or power density: the radiant power incident per unit area upon a surface, generally expressed in watts per square metre [W m^-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 [J m^-2];

t

time, duration of the exposure, expressed in seconds [s];

λ

wavelength, expressed in nanometres [nm];

γ

limiting cone angle of measurement field-of-view expressed in milliradians [mrad];

γ_m

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 [J m^-2 sr ^-1].

Table 2.1 Radiation hazards U.K.

Wavelength [nm]λ	Radiation range	Affected organ	Hazard	Exposure limit value table
180 to 400	UV	eye	photochemical damage and thermal damage	2.2, 2.3
180 to 400	UV	skin	erythema	2.4
400 to 700	visible	eye	retinal damage	2.2
400 to 600	visible	eye	photochemical damage	2.3
400 to 700	visible	skin	thermal damage	2.4
700 to 1 400	IRA	eye	thermal damage	2.2, 2.3
700 to 1 400	IRA	skin	thermal damage	2.4
1 400 to 2 600	IRB	eye	thermal damage	2.2
2 600 to 106	IRC	eye	thermal damage	2.2
1 400 to 106	IRB, IRC	eye	thermal damage	2.3
1 400 to 106	IRB, IRC	skin	thermal damage	2.4

Table 2.2 Exposure limit values for laser exposure to the eye — Short exposure duration < 10 s U.K.

Table 2.3 Exposure limit values for laser exposure to the eye — Long exposure duration ≥ 10 s U.K.

Table 2.4 Exposure limit values for laser exposure of skin U.K.

Table 2.5 Applied correction factors and other calculation parameters U.K.

Parameter as listed in ICNIRP	Valid spectral range (nm)	Value
CA	λ < 700	CA = 1,0
	700 — 1 050	CA = 10 0,002(λ - 700)
	1 050 — 1 400	CA = 5,0
CB	400 — 450	CB = 1,0
	450 — 700	CB = 10 0,02(λ - 450)
CC	700 — 1 150	CC = 1,0
	1 150 — 1 200	CC = 10 0,018(λ - 1 150)
	1 200 — 1 400	CC = 8,0
T1	λ < 450	T1 = 10 s
	450 — 500	T1 = 10 · [10 0,02 (λ - 450)] s
	λ > 500	T1 = 100 s

Parameter as listed in ICNIRP	Valid for biological effect	Value
αmin	all thermal effects	αmin = 1,5 mrad

Parameter as listed in ICNIRP	Valid angular range (mrad)	Value
CE	α < αmin	CE = 1,0
	αmin < α < 100	CE = α/αmin
	α > 100	CE = α2/(αmin · αmax) mrad with αmax = 100 mrad
T2	α < 1,5	T2 = 10 s
	1,5 < α < 100	T2 = 10 · [10 (α - 1,5) / 98,5] s
	α > 100	T2 = 100 s

Parameter as listed in ICNIRP	Valid exposure time range (s)	Value
γ	t ≤ 100	γ = 11 [mrad]
	100 < t < 104	γ = 1,1 t 0,5 [mrad]
	t > 104	γ = 110 [mrad]

Table 2.6 Correction for repetitive exposure U.K.

Each of the following three general rules should be applied to all repetitive exposures as occur from repetitively pulsed or scanning laser systems:

1.

The exposure from any single pulse in a train of pulses shall not exceed the exposure limit value for a single pulse of that pulse duration.

2.

The exposure from any group of pulses (or sub-group of pulses in a train) delivered in time t shall not exceed the exposure limit value for time t.

3.

The exposure from any single pulse within a group of pulses shall not exceed the single-pulse exposure limit value multiplied by a cumulative-thermal correction factor C_p=N^-0,25, where N is the number of pulses. This rule applies only to exposure limits to protect against thermal injury, where all pulses delivered in less than T_min are treated as a single pulse.

Parameter	Valid spectral range (nm)	Value
Tmin	315 < λ ≤ 400	Tmin = 10 -9 s (= 1 ns)
	400 < λ ≤ 1 050	Tmin = 18· 10 -6 s (= 18 μs)
	1 050 < λ ≤ 1 400	Tmin = 50· 10 -6 s (= 50 μs)
	1 400 < λ ≤ 1 500	Tmin = 10 -3 s (= 1 ms)
	1 500 < λ ≤ 1 800	Tmin = 10 s
	1 800 < λ ≤ 2 600	Tmin = 10 -3 s (= 1 ms)
	2 600 < λ ≤ 10 6	Tmin = 10 -7 s (= 100 ns)