Laser Safety, ANP 6 nov. 2014.1 Working with lasers.

Laser Safety, ANP 6 nov. 2014. 1

Working with lasers.

Can I use these goggles?



The sun is the brightest source.


Eye “reference” values:

• Sunlight: 1000 W/m2 (= 1 mW/mm2)

• Pupil range Ø: 3 – 7 mm (7 –38 mm2)

• Optical power received by the eye:7 – 38 mW

• Eye blink reflex: 0.25 sec.(only applicable in the visible area)


The human eye (simplified).

Types of photoreceptors


Distribution of rods and cones



Wavelength (λ) and impact.


Classification EN 60825-1

• Class 1: always safe

1M: always safe without focusing• Class 2: safe, due to the blink reflex, <1mW

2M: safe, without focusing• Class 3R: low risk of injury, restricted beam

viewing, <5mW 3B: direct exposure = eye hazard, <0.5W

• Class 4: ALL OTHER LASERS


(il)legal? purchases…

Dutch legislationSource: Informatieblad 26 / 4 september 2006, Voedsel en Waren Autoriteit:

• Laserpointer: no selling of class 3R, 3B and 4.

• Lasergadget: no selling of class 2, 2M, 3R, 3B and 4.


Not always a laser…..


Maximum Permissible Exposure• Typically set at 10% of the dose creating damage with a

probability of 50%, worst case conditions.• Basis for selecting laser goggles.

Warning symbol class 2 and up.


MPE in W/cm2 .


MPE in J/cm2.


MPE in J/cm2.


Eye protection terminology.Example of EN 207 specifications


EN 207 laser working modes.

EN 207 specifies four laser working modes:

Working mode Letter Pulse length

Continuous mode D > 0.25 sPulsed mode I >1 μs–0.25 sGiant pulsed mode R 1 ns–1 μsModelocked M < 1 ns


EN 207 scale numbers.Range: L1-L10, Ln means that OD > n; n=0: no protection.


Example 1, Q

• A laser operates at 1064 nm and has a pulse duration of 10 ns, 103 J/m².You have goggles that are specified asDIR 1064 L5

• Do these goggles offer suitable protection for this particular laser?


Example 1, A

The pulse durationindicates that we shouldlook at theR specification,with scale number n=5,which gives an upperlimit of 5×102 J/m²,which means that thesegoggles do not offersuitable protection forthis particular laser.

1064nm/10ns/ 103 J/m²

DIR 1064 L5 ??


Example 2, Q

• A laser operates at 780 nm, is continuous wave with a power density ofP = 500 W/m².

• Does a D 780 L2 rated goggle offer suitable protection for this particular laser?


Example 2, A

• You need a D protection level oflog(500) − 1 = 1.69, which isrounded up to 2.In other words, the safety goggles should be at least

• D 780 L2.

780nm CW, P=500W/m2

D 780 L2 ??

Case: Fianium SC400-4What goggles to buy ????


Case: Fianium SC400-4

• Pulse width: 6 ps

• Total power: > 4 W

• Rep. Rate: 40 MHz

• Beam diameter at 633 nm: 1.5 mm


Peak power = 17 kWPeak Energy = 100 nJ

Case: Fianium SC400-4• MPE curve not directly applicable (λ dependancy)

• Calculate energy density for open pupil area: 100e-9 / 0.39 = 25e-8 J/cm2 = 25e-4 J/m2 .

In 0.25 s, 10e6 (=N) pulses occur, thermal correction factor N1/4

applies (EN 60825). Cp=(10e6)0.25 = 56. Attenuation needed = log(E/1.5)+4= 3.0.

• DC calculation: log(P)-1 = log(4/0.39*1e4)-1 = 5.0-1 = 4.0 (!)




Transmitted: ~7 mW , still not safe.

Case: Fianium SC400-42. LaserVision T1L01, VLT = 30 %, € 860.-


Transmitted: 60 mW , OD needed = 2.2Conclusion: still not safe.

From 1400 nm to 2400 nm: ~OD4.

Case: Fianium SC400-43. Thorlabs LG2, VLT = 19 %, € 156.-


Transmitted (vis): 105 mW , OD needed 2.4Conclusion: still not safe.


100 % protection



Goggles, summary.

• Consult the laser manufacturer

• Consider the Visible Light Transmittance

• Consider comfort

• Keep the goggles in good shape


Enclosure, black cloth curtain





Good practice in beampath design.









Top 14 of laser related injuries,Rockwell Laser Industries

• Unanticipated eye exposure during alignment.• Misaligned optics and upwardly directed beams. • Available laser eye protection was not used.• Equipment malfunction.• Improper method of handling high voltage.• Intentional exposure of unprotected persons.• Operators unfamiliar with laser equipment.• No protection provided for associated hazards.• Improper restoration of equipment following servicing.• Incorrect eyewear selection and/or eyewear failure.• Accidental eye/skin exposure during normal use.• Inhalation of laser-generated fume or viewing of secondary radiation (UV, blue light).• Laser ignition of fires.• Photochemical eye or skin exposure.



Laser accidents are:

• - High impact

• - Low probability


To err is human

• Key to safety: Protocol, multiple lines of defense.


Thank you!



Luminosity function of the eye.

Wavelength [nm]


Good practice in beampath design.

Enclosure, black plastic curtain


Laser Safety, ANP 6 nov. 2014.1 Working with lasers.

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