F110[Part 1

Non-Coherent 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 range of radiation emitted by the source and the results should be compared with the corresponding exposure limit values indicated in Table 1.1. More than one exposure value and corresponding exposure limit can be relevant for a given source of optical radiation.

Numbering (a) to (o) refers to corresponding rows of Table 1.1.

For the purposes of these Regulations, the formulae above can be replaced by the following expressions and the use of discrete values as set out in the following tables:

Table 1.1: Exposure limit values for non-coherent optical radiation

Note 1: The range of 300 to 700 nm covers parts of UVB, all UVA and most of visible radiation; however, the associated hazard is commonly referred to as blue light hazard. Blue light strictly speaking covers only the range of approximately 400 to 490 nm.

Note 2: For steady fixation of very small sources with an angular subtense < 11 mrad, L B can be converted to E B . This normally applies only for ophthalmic instruments or a stabilised eye during anaesthesia. The maximum “stare time” is found by:t max = 100 / E B with E B expressed in W m -2 . Due to eye movements during normal visual tasks this does not exceed 100 s.

Table 1.2: S () [dimensionless], 180 nm to 400 nm

Table 1.3: B (), R () [dimensionless], 380 nm to 1400 nm

F111[Part 2

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.

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.

Table 2.1: Radiation hazards

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

a If the wavelength of the laser is covered by two limits, then the more restrictive applies.

b When 1400 < 10 5 nm: aperture diameter = 1 mm for t 0.3 s and 1.5 t 0.375 mm for 0.3 s < t < 10 s; when 10 5 < 10 6 nm: aperture diameter = 11 mm.

c Due to lack of data at these pulse lengths, ICNIRP recommends the use of the 1 ns irradiance limits.

d The table states values for single laser pulses. In case of multiple laser pulses, then the laser pulse durations of pulses falling within an interval Tmin (listed in table 2.6) must be added up and the resulting time value must be filled in for t in the formula: 5.6 10 3 t 0.25

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

a If the wavelength or another condition of the laser is covered by two limits, then the more restrictive applies.

b For small sources subtending an angle of 1.5 mrad or less, the visible dual limits E from 400 nm to 600 nm reduce to the thermal limits for 10 s≤ t<T₁ and to photochemical limits for longer times. For T₁ and T₂ see Table 2.5. The photochemical retinal hazard limit may also be expressed as a time integrated radiance G = 10⁶ C_B [J m^-2 sr^-1] for t > 10s up to t = 10000 s and L=100 C_B [W m^-2 sr^-1] for t> 10000 s. For the measurement of G and L_γm must be used as averaging field of view. The official border between visible and infrared is 780 nm as defined by the CIE. The column with wavelength band names is only meant to provide better overview for the user. (The notation G is used by CEN; the notation L t is used by CIE; the notation L_P is used by IEC and CENELEC.)

c For wavelength 1400 — 10⁵ nm: aperture diameter = 3.5 mm; for wavelength 10⁵ — 10⁶ nm: aperture Diameter = 11 mm.

d For measurement of the exposure value the consideration of γ is defined as follows: If α (angular subtense of a source) > γ (limiting cone angle, indicated in brackets in the corresponding column) then the measurement field of view γ_m should be the given value of γ. (If a larger measurement field of view is used, then the hazard would be overestimated). If α < γ then the measurement field of view γ_m must be large enough to fully enclose the source but is otherwise not limited and may be larger than γ.

Table 2.4: Exposure limit values for laser exposure of skin

a If the wavelength or another condition of the laser is covered by two limits, then the more restrictive applies

Table 2.5: Applied correction factors and other calculation parameters

Table 2.6 Correction for repetitive exposure

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 singlepulse exposure limit value multiplied by a cumulative-thermal correction factor Cp=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 Tmin are treated as a single pulse.

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F112[Part 3

Assessment, Measurement and Calculation of Exposure

The methodology applied in assessment, measurement and/or calculations shall follow the standards of the International Electrotechnical Commission (IEC) in respect of laser radiation and the recommendations of the International Commission on Illumination (CIE) and the European Committee for Standardisation (CEN) in respect of non-coherent radiation.

In exposure situations which are not covered by these standards and recommendations, and until appropriate EU standards or recommendations become available, assessment, measurements and/or calculations shall be carried out using available international science-based guidelines. In both exposure situations, the assessment may take account of data provided by the manufacturers of the equipment when it is covered by relevant Community Directives.]