Multiple Wavelength MPE
Eye exposure to a beam with several wavelengths on the ICNIRP 2013 limits: lines absorbed in the same tissue add, while the retina and the cornea count independently.
Educational only — not compliance-grade
These pages implement the published exposure limits for the cases each one states, but they are educational tools: no laser safety officer has signed them off.
- Do not use these results alone for PPE selection, NHZ / NOHD approval, controlled-area sign-off, enclosure/interlock approval, or formal classification.
- Always verify against ANSI Z136.1, IEC 60825-1, your local procedures, and the responsible laser safety officer / CLSO.
0.25 s (the blink reflex) only protects against visible beams; use 10 s or more when a line is invisible.
Retina: sum of shares
1.22
Exceeds the limits
Anterior eye (cornea and lens): sum of shares
0.637
Within the limits
Whole beam
Exceeds the limits
Attenuate every line by 1.22× (OD 0.09) at least
Retina
Anterior eye (cornea and lens)
| λ (nm) | Power | Limit | Largest power alone | Share (P / largest) |
|---|---|---|---|---|
| 450 | 400 µW | Retina, thermal | 980 µW | 0.408 |
| Retina, photochemical (blue light) | applies from 10 s | 0 | ||
| 520 | 400 µW | Retina, thermal | 980 µW | 0.408 |
| Retina, photochemical (blue light) | applies from 10 s | 0 | ||
| 638 | 400 µW | Retina, thermal | 980 µW | 0.408 |
| 1550 | 10.0 mW | Cornea (IR) | 15.7 mW | 0.637 |
| Same limit, all lines | Retina, thermal: 1.22 · Retina, photochemical (blue light): 0 · Cornea (IR): 0.637 | |||
ICNIRP 2013 (Health Phys. 105:271, p. 279): wavelengths absorbed in the same tissue add; wavelengths absorbed in different tissues, such as the retina and the cornea, are assessed independently. Each line's share of a limit is its power over the largest power that stays within that limit for every exposure up to t, averaged over the limit's aperture (7 mm for the retina; 1–3.5 mm for the cornea; 3.5 mm for the anterior-segment limit at 1150–1400 nm). A beam under 1 mm (1/e diameter, d/√2 for the 1/e² d) is held to its peak on the cornea below 0.35 s (ICNIRP 2013 Table 5 note c). A line's share of a tissue is its largest share there (one line's thermal and blue-light retinal limits are met separately); the shares then add over the lines, and each tissue's sum must stay at or below 1.
All lines are taken as one co-aligned beam of the diameter above, viewed for the same time. The retinal limits are for a point source (the conservative case). Not modelled: skin, pulses and pulse trains.
Model and references
Exact. The equations are exact within the stated assumptions, or are a standard's tabulated values. The results are as good as the inputs. About the tiers
ICNIRP 2013 eye limits per line (point source, averaged over each aperture or, under 1 mm (1/e) on the cornea below 0.35 s, the peak (Table 5 note c), exposures up to t); shares add per tissue (retina; cornea and lens) as on p. 279. Not modelled: skin, pulses, lines of different beam size.
- ICNIRP (2013). Guidelines on limits of exposure to laser radiation of wavelengths between 180 nm and 1,000 µm. Health Phys. 105(3), 271–295. p. 279 (multiple wavelengths), Tables 5 and 8. doi:10.1097/HP.0b013e3182983fd4