risk assessment according to the effective range of visual ... · pdf fileoptics and...

Fachhochschule KölnCOLOGNE UNIVERSITY OF APPLIED SCIENCES

Institute of Applied Optics and Electronics

Risk assessment according to the effective range of visual impairment due to afterimages as a result

f t bli diof temporary blinding

Prof. em. Dr. Hans-Dieter Reidenbach, Cologne University of Applied Sciences

Faculty of Information, Media and Electrical TechnologyInstitute of Applied Optics and Electronics

R h L b t M di l T h l d N I i i R di tiResearch Laboratory Medical Technology and Non-Ionizing Radiation

10-11 October 2011 EUROCONTROL

Fachhochschule KölnCOLOGNE UNIVERSITY OF APPLIED SCIENCES

Institute of Applied Optics and Electronics

Content

1. Introduction: Laser pointers and hand-held laser products – Use and misuseheld laser products Use and misuse

2. Hazards due to laser pointers in air traffic 2.1 Deterministic hazards 2 2 Hazards from temporary blinding 2.2 Hazards from temporary blinding

3. Summaryy


1. Introduction: Laser pointers and hand-held laser products – Use and misuse

Laser pointer: Hand-held laser product key ring- or ballpoint pen-likekey ring or ballpoint pen likeDesign:

LD Module Driver Batteries

Laser diode

LD-Module Driver BatteriesSolid state laser

Battery Pump-Diode Driver DPSS Laser Module


Wavelengths : 405, 445, 473, 532, 635, 650 nmPower output : 5 – 500 mW or even morepRange: up to 20 miles or even more

Which one is the best laser pointer?

Vi l t (405 )150 WViolet (405nm)150mWGreen (532nm) 50mWRed (650nm) 100mW


Hobby application – Astronomy?

All we need now is an aircraft


2. Hazards due to laser pointers in air traffic

In mid-2011, Rockwell Laser Industries analyzed 6,903 FAA reports from 2004 to mid March 2011

Incidents by Type (cockpit illumination, intentional exposure, eye effects & injuries)

FAA reports from 2004 to mid-March 2011. They found that the cockpit was illuminated only in about

1 875 incidents (27%)1,875 incidents (27%).

Of these, the exposure appeared intentional in about 350 incidents (19% of cockpit illuminations), defined as multiple exposures or the beam tracking the aircraft.

There were about 100 incidents (1.5% of all incidents) where eye effects or injuries were reported The RLI analysis was done

b K i D ll


where eye effects or injuries were reported, i.e. a very few confirmed claims of retinal injury.

by Kevin Donnelly, and was supervised and presented in August 2011 by RLI president Bill Ertle.

2.1 Deterministic hazards (risk of permanent damage)

Laser Pointer become cheaper and cheapercheaper and cheaper

Increasing power (5 mW100 mW1000 mW )100 mW1000 mW ….)o Easy to get via Interneto Easy to buy in foreign

countries


Rough estimates only

Laser power and exposure duration in order to estimate a threshold damage (minimal lesion) from a laser beam:

0.4 mW and 10 s equals the exposure limit value: 1 0 mW/cm2 = 10 W/m2

a threshold damage (minimal lesion) from a laser beam:

1.0 mW/cm = 10 W/m1 mW and 0.25 s equals the exposure limit value: 2 5 mW/cm2 = 25 W/m22.5 mW/cm 25 W/m1 mW and „(very) long“ exposure duration eventually yields to a damage?eventually yields to a damage?5 mW und 15 min (red, i.e. 632.8 nm) no damagegca. 5 mW and 60 s (532 nm, i.e. SHG Nd:YAG) damage g10 mW (532 nm) and 0.25 s might result in a damage (100 %)

10-11 October 2011„safety factor (reduction factor)“ 10

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Powerful pointer exist: E2 Evolution Series

The future has already arrivedalready arrived


What‘s about safety?

S3 Spyder III Arctic

200 mW (405 nm 532 nm 650 nm) and 1000 mW (445 nm) 200 mW (405 nm, 532 nm, 650 nm) and 1000 mW (445 nm)

Reality: 1 Watt laser pointer at 445 nmMPE-value for 445 nm: 0.039 mW (10 s) Ratio: 1000 mW/0 039 mW = 25 641 Ratio: 1000 mW/0.039 mW = 25,641 ….


Information – sense and nonsense (1)

Wicked Laser Spyder III Arctic

The August 14 Glendale arrest is the first known time that such a powerful blue handheld laser has been confirmed to be used against an aircraft.

Let‘s have a closer look on the accompanied information and the

// f / / /

accompanied information and the various statements

10-11 October 2011

http://www.laserpointersafety.com/news/news/aviation-incidents_files/2b82415da7bb86a713c26619995ea04b-244.php

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Most laser/aviation incidents involve green l lasers. During the first half of 2011, in 93% of incidents

reported to the FAA, the pilot said he or she saw a green light.

Blue light reports were less than 1% of incidents.



1 watt of power is 1000 milliwatts. That means a 1 watt is 200 times more powerful

than lasers sold as pointers in the U.S. The 1-watt blue lasers being sold can be eye

hazards to a distance of approximately 750 feet.pp y? That is, under ideal conditions of a non-movingThat is, under ideal conditions of a non moving

beam, a person 750 feet away could have a spot or spots burned onto their retina. , but there exists a p ,safety factor of about 10?

The closer the person is to the laser, the greater the The closer the person is to the laser, the greater the chance of a burn.



The beam would not have the same effect on il t’ d i i ti i id t ha pilot’s eye during an aviation incident where

the laser device is hundreds or thousands of feet away. This is because

$1) laser beams spread out over distance so the power density (irradiance) is greatly reduced,

$2) it is nearly impossible to keep a laser fixed on one area of the cockpit window, and 3) h ll bli k f 1/4 d f$3) a human naturally blinks after 1/4 second of exposure to a bright light. No, only about 20% blink or avert!

$(Of course no one should aim a laser of any power at or$(Of course, no one should aim a laser of any power at or near an aircraft, no matter how low the chance of injurious or bright-light effects.)



However, when it comes to non-injurious visual hazards a 1-watt 445 blue laser is equal to only ahazards, a 1-watt 445 blue laser is equal to only a 35 milliwatt (0.035 watt) green laser. ???

Thi th t ft i l d di t ti This means that afterimage, glare and distraction effects are only in the range of a 35 mW green laser. ??????

The reason is that the human eye is much less iti t 445 bl l li ht d tsensitive to 445 nm blue laser light, compared to

common 532 nm green laser light. and no!Said another way, a blue laser appears 29 times less

bright to the human eye than a green laser of the same power. and no!

„At least no scientific prove exists as far

10-11 October 2011

as these statements are concerned.“EUROCONTROL

Guinness World Record – That‘s it!


1 Watt green

What is the intended use? In the meantime even a 2-watt laser pointer is available. The lasers come in three colours: green (532 nm) blue The lasers come in three colours: green (532 nm), blue

(450 nm), and violet (405 nm).10-11 October 2011 EUROCONTROL

NOHD – nominal ocular hazard distance

1

MPEP4 NOHD

Eye hazard distance

Safety

Visual impairmentMPE

Safety distance

Divergence Θ: 1 mrad = 1 mm/1 m = 1 m/1 km

Θ Θ

Laser

AfterimagePotential for retinal

Afterimage

Glare

Startle, dis-tractionFlashblindess

10-11 October 2011

damage Glare traction

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NOHD as a function of power P and divergence Θ

Θ1P 0.36 s)NOHD(10 λ 500 nm:

Θ1P 0.226 s)NOHD(0.25

Exposure duration: 10 s

Exposure duration: 0.25 s

Laser beam power mW

MPE-value: 10 W/m2 MPE-value: 25 W/m2

NOHD/m NOHD/m NOHD/m NOHD/mNOHD/m

for 1 mrad

NOHD/m

for 0.1 mrad

NOHD/m

for 1 mrad

NOHD/m

for 0.1 mrad5 25 250 16 1605 25 250 16 16010 36 360 23 22550 80 800 50 50050 80 800 50 500100 113 1,128 71 710500 252 2,525 160 1,600

1,000 360 3,570 225 2,250A 1000 mW (1 watt) laser is not 100 times more hazardous than a 10 mW laser.Damage might happen only if the MPE is effectively exceeded

10-11 October 2011But don‘t forget: IR-radiation has to be considered too.

Damage might happen only if the MPE is effectively exceeded.

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Problem: Missing IR-Filter

„All Lines“ of a green laser pointer

1064 nm

Own measurements:20-mW laser pointer: maximum 20 mW at 1064 nm additionally 50-mW laser pointer: maximum 60 mW at 1064 nm additionally

In addition to 532 nm problems might arise from infrared radiation for the following 532 nm

808 nm

gDPSS: red (671 nm), yellow (593,5 nm), yellow (589 nm) blue (473 nm)

10-11 October 2011

yellow (589 nm), blue (473 nm) and 404 nm (violet)

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Estimation of a permanent damage

Assumption: B di 1 d t 0 1 dBeam divergence: 1 mrad up to 0.1 mradExposure duration: 0.25 s up to 10 sCancelation of a 10fold safety/reduction factor

would result in a NOHD less by a factor of 10 3.16 Without a safety/reduction factor a 1 W-laser will be

relatively non-hazardous/safe in a distance of more thanyca. 225 m/10 70 m (for 1 mrad) or

1000 mW in 7 cm diameter is equivalent to 10 mW in 7 mm for 250 ms

ca. 2,250 m/10 700 m (for 0.1 mrad) resp.for short-time exposure (0.25 s).

for 250 ms.

For an exposure duration of 10 s these would beca. 113 m (for 1 mrad) or ca. 1,128 m (for 0.1 mrad) resp.( ) ( ) p

A damage is little likely. 10-11 October 2011 EUROCONTROL

2.2 Hazards from temporary blinding

Visible laser radiation might result in temporary effects:Distraction startleDistraction, startle,Dazzle, glare (blinding), Flashblindness and Afterimages.

Vision might be handicapped temporarily more or lessor less.

This might result in indirect hazards, whose d i ht d th ti d fdegree might exceed the respective degree of direct harm completely.

A crash of an airplane can not be excluded.10-11 October 2011 EUROCONTROL

After image formation


Temporary blinding means: Glare during the exposure and after effects afterwards


Glare during the exposure and after effects afterwards

Result

Before Later

10-11 October 2011 EUROCONTROL after Blinding

Temporary blinding and (effective) range

Glare and its outcome might appear beyond the NOHDNOHD

Range – definition:g a.) Range in the sense of a safety distance

(NOHD) (NOHD)

b ) Ranges/Zones in the sense of blinding b.) Ranges/Zones in the sense of blinding (visual hazard distances)$$ Ranges according to ANSI/FAARanges according to ANSI/FAA$$ Ranges according to ANSI/FAARanges according to ANSI/FAA$$ Range according to the Cologne modelRange according to the Cologne model. .


Range/distance calculation

1P4RW

1P4NOHD

MPERW

AZAZ

MPE

NOHD

where P is laser power,MPEAZ is the maximum permissible exposure

(here irradiance, ie. power density at the cornea) for the respective zone and

Θ is the beam divergence (full angle, far field angle of the laser beam).

The Index „A“ is chosen for the respective zone.


Zones – according to ANSI Z136.6

MaximumTemporary Adverse Visual Effects

Range Name of range or zone (effect)

Maximum permissible

exposure

Equivalent laser power in 7 mmexposure

RWLZ„laser-free zone”(No distraction)

50 nW·cm-2 = 0 510-3 W/m2 19.25 nW(No distraction) 0.5 10 W/m

RWC

„critical zone”(Distraction

5 μW·cm-2

1 925 μWRWCZ (Distraction hazard; glare) = 5010-3 W/m2

1.925 μW

sensitive zone“ 2RWSZ

„sensitive zone(Flashblindness,

after-image)

100 W·cm-2 = 1 W/m2 38.5 μW

after image)

NOHD Nominal ocularhazard distance 25 W/m2 1 mWhazard distance


Photos from the FAA study to illustrate four test scenarios

No laser exposure. This gives a baseline for a “normal” approach. Example:

0 5 µW/cm²: This corresponds to a 5 mW

5 mW, 532 nm, 1 s

0.5 µW/cm²: This corresponds to a 5 mW (milliwatt) laser pointer at 3,700 feet, or a 50 mW pointer at 2.2 miles.

5.0 µW/cm²: This corresponds to a 5 mW5.0 µW/cm : This corresponds to a 5 mW pointer at 1,200 feet, or a 50 mW pointer at 3,800 feet.

50 µW/cm²: This corresponds to a 5 mW µ ppointer at 350 feet, or a 50 mW pointer at 1,100 feet. The animation simulates flashblindness and a slowly fading afterimage

10-11 October 2011

flashblindness and a slowly fading afterimage.

EUROCONTROLModified; http://www.pangolin.com/faa/laser-aircraft-animation-and-explanation.htm

Zones or Ranges

Ranges for different zones as a function of laser beam power; beam divergence Θ = 1 mrad 1P4g

1

MPEP4RW

AZAZ

Laser beam power/mW

Range RWSZkm

Range RWCZkm

Range RWLZkm

5 0.08 0.357 3.56810 0.113 0.505 5.046

50 0 252 1 128 11 28450 0.252 1.128 11.284

100 0.357 1.596 15.958

500 0.798 3.568 35.682

1000 1 128 5 046 50 46310-11 October 2011

1000 1.128 5.046 50.463EUROCONTROL

Some details on „limit values“

It has been shown that power densities above 50 W 2 i l t t l f50 μW·cm-2, equivalent to a laser power of 20 μW, is unacceptable in the „laser free zone“ above the runway.

5 µW/cm² i e 2 μW are considered as so-called 5 µW/cm , i.e. 2 μW, are considered as so called „flight safe exposure value“ (FAA).

In our own investigations test persons were not g pwilling to participate in tests with a laser power above 30 μW and exposure durations longerabove 30 μW and exposure durations longer than 10 s.

20.09.2011 Reidenbach NIR 2011

Research on temporary blinding

We started our research in Nov/Dec 2005 First final report (2008): 408 pagesp gOnly in German

Additional topics Additional topics have been

bli h d i j lpublished in journals and/or conferenceproceedings.

Number of test persons:Number of test persons: 191191Number of test persons: Number of test persons: 191191Number of trials: Number of trials: 1,7361,736


Some important results: Relationship between after image and visual impairment

After image duration tAI 300 s to 350 s equivalent to:equivalent to:

Reading disability: timpVis 35 s to 70 sp

and Visual acuity disturbance t 60 s to 90 sVisual acuity disturbance tVA 60 s to 90 s.

The impaired vision lasts about The impaired vision lasts about 10 to 30 % of the total after image duration.

Valid for one wavelength (632.8 nm) to begin with.g ( ) g

20.09.2011 Reidenbach NIR 2011

Red vs. Green – Exposure duration: 0.25 s

632.8 nm, 0.25 s25 Subject 1

532 nm, 0.25 s25

dura

tion

/ s

20

Subject 1Subject 2Subject 3Subject 4Subject 5Subject 6Subject 7 ur

atio

n / s

20Subject 2Subject 10Subject 3 Subject 4

mpa

irmen

t d

10

15Subject 8Subject 9Subject 10Subject 11Subject 12

pairm

ent d

10

15

im

5

10

im

5

10

optical power / mW0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

0

optical power / mW0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

0

class 1

10-11 October 2011

class 1

EUROCONTROLThe factor between green and red is about 1.5 instead of 3.3 according to V-lambda.

Dose relationship

Laser irradiation (632.8 nm) in the fovea (glare angle 0°)

t = 2·{t /s 25 3 ln[(P t )/µJ] 6 7} 50 6 ln[(P t )/µJ] 13 4taf,fovea = 2·{taf,5°/s 25.3ln[(Ptexp)/µJ] – 6.7} 50.6ln[(Ptexp)/µJ] – 13.4

urat

ion

200

240

280

ta = 50.6•ln(P•texp) - 13.4

rimag

e d

t a/s

120

160200

Class 2: Class 1:

Aft

er

40

80 Class 2: 1 mW, 0.25 s

Class 1: 0.39 mW, 1 s

0 50 100 150 200 250 300 350 400P•texp / µJ

From t f f 50.6ln[(Pt )/µJ] – 13.4 = 0 it follows1 303t 50 613.4 From taf,fovea 50.6 ln[(P texp)/µJ] 13.4 0 it follows

for the threshold value of exposure duration texp,th = 1.3 s for 1 μW or texp,th = 0.13 s for 10 μW ort = 13 ms for 100 μW or t = 1 3 ms for 1 mW

μWP

1.303

μWP

e s

t 50.6exp

10-11 October 2011

texp,th = 13 ms for 100 μW or texp,th = 1.3 ms for 1 mWμμ

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Relationship – we have found

ce Temporary Permanent

rban

c Temporary blinding

Permanentdamage

Dis

tu

Saturation behaviourbehaviour

RapidRapid increase

Tolerable?

Optical powerThreshold?

Tolerable?

10-11 October 2011

Optical power

EUROCONTROL

Correlations – Function and derivative

taf,fovea(P, texp) 50.6ln[(Ptexp)/µJ] – 13.4 For P = constant:

t’ f f (P t ) 50 6/tRapid change

t af,fovea(P, texp) 50.6/texp

For texp = constant:exp

t*af,fovea(P, texp) 50.6/P

With: y = [taf,fovea(P, texp) + 13.4]/50.6 x = Ptexp

Slow change

exp


Even a short exposure duration results in a remarkable impairment

Short exposure duration and low power

Temporary blinding happens as a result of short d ti l d h th li dexposure duration already when the applied

power is sufficiently high enough


Comparison between sunlight exposure and laser irradiation

G i hGaze into the Sun

51mW/1.3 cm Impairment

632.8 nm 532 nm

cm(without IR)

Impairment duration

0.5 s 1 s 0.5 s and 25 µW 0.5 s and 10 µW

1 s 3 s 1 s and 50 µW 0.5 s and 30 µW

2 s 7 s 1 s and 80 µW 0 5 s and 70 µW2 s 7 s 1 s and 80 µW 0.5 s and 70 µW

3 s 11 s 1 s and 400 µW 0.25 s and 600 µW

4 s 13 s 1 s and 500 µW 0.25 s and 780 µW

5 s 16 s 5 s and 370 µW 1 s and 300 µW5 s 16 s 5 s and 370 µW 1 s and 300 µW


Range in the sense of blinding –Range according to the Cologne model

Range RWVI (range with vision impairment, range with reading handicap)range with reading handicap)

dP

P

req

LVI

dPPRW

where req

PL is the laser beam power, Preq is the power required in a 7-mm pupil q

to result in a vision impairment durationbetween 0 s and 10 s,

dP is the pupil diameter (here 7 mm) and Θ is the beam divergence (full angle,

10-11 October 2011

g ( g ,far field angle of the laser beam).

EUROCONTROL

Range according to the Cologne model

Laser beam power Preq in a 7-mm pupil, which is required to result in a vision impairment durationrequired to result in a vision impairment duration between 0 s (= threshold) and 10 s and respective ranges RWVI for different laser powers PL andranges RWVI for different laser powers PL and a beam divergence Θ of 1 mrad

Range RW /km

ExposureRequired

laser beam

Range RWVI/km

P P P Pduration/s power Preq/μW

PL = 5 mW

PL = 50 mW

PL = 100 mW

PL = 1000 mW

0.25 5.2 … 400 0.217 - 0.025 0.684 - 0.078 0.971 - 0.111 3.07 - 0.35

1 1.3 … 100 0.434 - 0.049 1.373 - 0.157 1.941 - 0.221 6.139 - 0.7

2 0.65 … 50 0.614 - 0.07 1.941 - 0.221 2.746 -0.313 8.682 - 0.99


Conversion of ranges

reqreq

AZ P2.6AP

MPE P

req

LVI

dPPRW

AZreq

P

MPE0.385PA

exp

req

PμJ100....μJ1.3t

Example: P = 5 mW, Preqtexp = 1.3 μJ … 100 μJAll other ranges are achieved by multiplication with

Preq

exp P

RWAZ MPEAZ Preq/μW RWVI (0 s – 10 s)

All other ranges are achieved by multiplication with mW5

RWLZ 3570 m 50 nW·cm-2

= 0.510-3 W/m20.01924 3,570 m

(texp = 67.5 s – 5,200 s)RW 357 m 5 μW·cm-2 1 924 357 m (0 68 s – 52 s)RWCZ 357 m 5 μW cm

= 5010-3 W/m21.924 357 m (0,68 s – 52 s)

RWSZ 80 m 100 W·cm-2 = 1 W/m2 38.5 80 m (0.34 s – 2.6 s)RWRWSZSZ 800 m800 m 100100 W·cmW·cm--22 = 1= 1 W/mW/m22 38.538.5 800 m (0.34800 m (0.34 s s –– 2.6 s)2.6 s)NOHD 16 m 25 W/m2 962 16 m (0.0014 s – 0.1 s)

500 mW500 mW

NOHDNOHD 160 m160 m 2525 W/mW/m22 962962 160 m (0.0014160 m (0.0014 s s –– 0.1 s)0.1 s)10-11 October 2011

500 mW500 mWEUROCONTROL

The burden with the „range“

Parameters are:Beam divergenceWavelengthWavelengthMode pattern or profile

(power density distribution in the cross section) and )

We‘ve found M2 1.2 – 1.6 f i t ifor green pointers, i.e. roughly TEM00

certainly the range of sight (dependent on the atmospheric attenuation)(dependent on the atmospheric attenuation)


Increased range

A laser beam has a divergence, ie. the beam di t i ith di tdiameter increases with distance.

But the divergence and diameter might be g gdecreased with a beam expander.

1m1m3.3f3.3f


Power density as a function of distance

For a given irradiance E = 100 µWcm-2

a laser power P = 100 mWa laser power P = 100 mW

results in a safety distance:

1P4z results in a safety distance:

A ) beam divergence = 1 mrad z = 356 m

π E z

zA.) beam divergence 1 mrad z 356 mB.) beam divergence = 100 µrad z = 3.56 km

A beam divergence of 100 µrad might be easily achievedwith a 10:1 telescopep


Ideal blinding tool: Laser class 1M and 2M

500 mW requires a minimum beam diameter d 25 cm (t 10 s) or MZB

S EπP4d

dS 25 cm (t 10 s) or dS 16 cm (t = 0.25 s), resp.

Collimated beam Nearl perfect conditions“ if mis se

MZB

Collimated beam: Nearly „perfect conditions“ if misuse of laser pointers as a blinding device is concerned.

If instead of the usual beam divergence of 1 mrad only 0.1 mrad do exist a far ranging laser pointerwould be available.

With such a laser pointer a vision pimpairment duration between 0 s and10 s would result in a range between g21.705 km and 2.475 km, namely if the exposure duration is as short as p0.25 s.


Look into the future – Beam expander

10-11 October 2011

Interchangeable Adapter Rings For Laser Pens and Portable Lasers - FREE

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Increased range(1)


Increased range (2) – and variable too


3. Summary

A real risk exists due to various laser pointers D t i i ti i t d i lik l Deterministic, i.e. permanent damage is unlikely,

but might not be excluded completely due to increasing laser powerlaser power

Nominal ocular hazard distances (NOHD) b l l t d f ti f d dican be calculated as a function of power and divergence

Non-injurious, i.e. temporary effects like glare, flash blindness after-images have been dealt with and respective zones might be designated

The reading impairment is explained as a research result in order to quantify the indirect effect associated with a laser illumination in the cockpit

Increasing laser power and application of beam expanders increase the current threat further


Thank you for your attention!Thank you for your attention!Prof. em. Dr. Hans-Dieter Reidenbach, C l U i it f A li d S i F lt f I f ti M di d El t i l T h l

EUROCONTROL

Cologne University of Applied Sciences, Faculty of Information, Media and Electrical TechnologyInstitute of Applied Optics and Electronics, Research Laboratory Medical Technology and Non-Ionizing RadiationBetzdorfer Str. 2, 50679 KOELN/[email protected]

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