Pulsed Laser MPE
Eye exposure limit of a pulse train, 180 nm to 1 mm: the three repetitive-pulse rules, which one binds, and the eyewear OD needed.
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.
Max energy per pulse
385 nJ
Retina, thermal, rule 3: C_P × single pulse
Your pulse / max
2.60×
Exceeds: eyewear OD 0.415 needed
Pulses in the exposure
10,000
10.0 s from the start of the first pulse to the end of the last
Max average power
385 µW
Yours: 1.00 mW
| Limit | 1. Single pulse | 2. Pulse groups (average) | 3. C_P × single pulse | Max per pulse | Your pulse / max |
|---|---|---|---|---|---|
| Retina, thermal | 770 nJ | 1.95 µJfull train: 10,000 pulses | 385 nJC_P = 0.500, n = 10,000 | 385 nJ | 2.60× (exceeds) |
| Anterior eye (skin limit, 2 × in the IR) | 19.3 mJ | 189 µJfull train: 10,000 pulses | — | 189 µJ | 5.30e-3× (within) |
Energies per pulse in the beam (1/e² Gaussian, averaged over each limit's aperture). Rule 3 applies to the retinal thermal limit only; "—" means the rule doesn't apply (rule 2 needs two pulses).
ICNIRP 2013 (Health Phys. 105:271, p. 287) applies three rules to every repetitively pulsed or scanned exposure, and the lowest wins: (1) each pulse within the limit for one pulse of its duration; (2) every group of pulses within the limit for the time it spans, up to the whole exposure, which is the average-power rule; (3) for the retinal thermal limit (400–1400 nm), each pulse within C_P times the single-pulse limit, with n the number of pulses within T₂ (10 s for a small source).
C_P: pulses longer than T_i (13.0 µs here) from a source up to 5 mrad get no reduction (C_P = 1); larger sources get n^−0.25, but not below 0.4 (α ≤ α_max) or 0.2 (α_max < α < 100 mrad), and none from 100 mrad. Pulses of T_i or shorter get C_P = 1 up to 0.25 s and 5 n^−0.25 beyond (more than 600 pulses); in the visible ICNIRP applies that only to intentional viewing, so use 0.25 s for an accidental glance (the blink reflex) and 10 s for invisible near-infrared beams. Pulses closer together than T_i count as one pulse for C_P, as in IEC 60825-1:2014 (rule 2 already adds their energies). IEC 60825-1:2014 also floors the 5 n^−0.25 at 0.4; ICNIRP gives no floor, so none is used here.
Below 1 ns ICNIRP Table 5 gives retinal limits of 1 mJ/m² (× C_C above 1050 nm) from 100 fs to 10 ps; shorter pulses, and the corneal limits below 1 ns, keep the irradiance of the shortest tabulated duration; the cornea is also kept below 10 % of its 1 ns limit, ICNIRP's conservative interim guideline (p. 287). The beam is a round Gaussian centred on each aperture (7 mm for the retina, 1–3.5 mm for the cornea). 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). Not modelled: irregular trains and bursts, scanned beams, skin.
Largest energy per pulse against the repetition rate for this pulse duration, exposure and beam: the single-pulse limit is flat, the C_P rule falls as n^−0.25 once it applies, and the average-power rule falls as 1/f at high rates. The thick line is the lowest; your pulse is within the limits where it lies below it.
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 repetitive-pulse rules 1–3 (C_P with T_i grouping) on the eye limits, sub-ns rows included; regular train, round Gaussian beam over each aperture. Not modelled: bursts, scanning, skin.
- 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. Repetitive pulse exposures (p. 287), Tables 4, 5 and 8. doi:10.1097/HP.0b013e3182983fd4
- Schulmeister, K. (2017). The new edition of the international laser product safety standard IEC 60825-1. White paper, Seibersdorf Laboratories. Multiple pulses, C₅ and pulse groups. seibersdorf-laboratories.at