Guidelines for the Safe Use of the LRMS,
LRIS, and LCMS Laser Products (Rev. 3)
February 2012
INO
2740, Einstein Street
Quebec (Quebec)
Canada, G1P 4S4
Tel.: (418) 657-7006
Fax.: (418) 657-7009
www.ino.ca
Copyright © 2010 by INO. All rights reserved.
Reproduction in whole or part in any way without
written permission from INO is strictly prohibited.
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
2
TABLE OF CONTENTS
TABLE OF CONTENTS ...................................................................................................................................... 2
LIST OF FIGURES ............................................................................................................................................. 3
LIST OF TABLES ............................................................................................................................................... 4
1
INTRODUCTION ........................................................................................................................................ 5
1.1
Purpose and scope of this manual ................................................................................................ 5
1.2
Acronyms and symbols used in this manual ................................................................................. 6
1.3
References .................................................................................................................................... 7
1.4
Order of precedence...................................................................................................................... 7
1.5
Important Notice ............................................................................................................................ 7
2
EMISSION CHARACTERISTICS OF THE LASER EQUIPMENTS ........................................................................ 9
2.1
Basic characteristics of the laser radiation .................................................................................... 9
2.1.1
Overview: The concept of laser line ..................................................................................... 9
2.1.2
Laser safety class and emission wavelength of the equipment ............................................ 9
2.2
General considerations about the laser safety issues ................................................................. 10
2.2.1
Transparency and refractive properties of the main structures of the eye: Some
consequences ..................................................................................................................................... 10
2.2.2
Maximum Permissible Exposure (MPE) .............................................................................. 11
2.2.3
Nominal Hazard Ocular Area (NOHA) ................................................................................. 11
2.3
Typical viewing scenarios and related laser hazards .................................................................. 12
2.4
Emission characteristics and laser safety parameters of each laser equipment ........................ 15
3
DETAILED SPECIFICATION OF THE NOMINAL OCULAR HAZARD AREAS ..................................................... 18
3.1
NOHA for the LRMS .................................................................................................................... 18
3.2
NOHA for the LRIS ...................................................................................................................... 22
3.3
NOHA for the LCMS .................................................................................................................... 24
4
RECOMMENDED CONTROL MEASURES AND SAFETY PRECAUTIONS ......................................................... 27
4.1
Risk assessment ......................................................................................................................... 27
4.2
Case #1: Operation of the laser equipments in a moving inspection vehicle............................. 28
4.3
Case #2: Operation of the laser equipments with the inspection vehicle temporarily stopped .. 29
4.4
Case #3: Operation of the laser equipments when the inspection vehicle is at rest (indoor and
outdoor settings) ...................................................................................................................................... 30
4.4.1
Recommended administrative/procedural control measures and safety precautions ........ 30
4.4.2
Recommended personal protective equipment ................................................................... 34
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
3
LIST OF FIGURES
Figure 1: Schematic illustration of a portion of the electromagnetic spectrum that spans from the near
ultraviolet up to the near infrared. The correspondence between the wavelength scale and the
perceived color of the visible light is illustrated. The vertical red arrow locates the 808-nm emission
wavelength of the laser equipments. ................................................................................................... 10
Figure 2: Schematic illustration of four representative viewing scenarios labeled from A to D, with the
associated risks of laser hazards decreasing with increasing order. .................................................. 13
Figure 3: Illustration of the typical setup of the LRMS installed in an inspection vehicle. .......................... 19
Figure 4: Schematic front view of a LRMS laser profiler showing the geometry of the laser beam for its
propagation path from the output window down to the road pavement. The drawing is not to scale
and the inspection vehicle is not shown. ............................................................................................. 20
Figure 5: Schematic side view of a LRMS laser profiler showing the geometry of the laser beam for its
propagation path from the output window down to the road pavement. The drawing is not to scale.
The inspection vehicle is not shown. ................................................................................................... 21
Figure 6: Illustration of the laser controlled area as recommended for a LRMS installed in an inspection
vehicle. The drawing is not to scale. .................................................................................................. 22
Figure 7: Illustration of the typical setup of the LRIS installed on an inspection vehicle. A photograph of a
free laser sensor unit is also shown to locate the output windows for the camera and laser line
projector. .............................................................................................................................................. 23
Figure 8: Schematic front view and side view of a LRIS mounted on an inspection vehicle, showing the
geometry of the laser beam during its propagation path from the output window of a laser sensor
down to the road pavement. The drawing is not to scale. .................................................................. 24
Figure 9: Photograph of the rear view of an inspection vehicle on which both laser sensor units of a
LCMS have been installed. A photograph of a free laser sensor unit is also shown to locate the
output windows of the camera and laser line projector. ...................................................................... 25
Figure 10: Schematic front view and side view of a laser sensor unit of a LCMS as it would be mounted
on an inspection vehicle. The geometry of the laser beam during its propagation path from the
output window of a laser sensor down to the road pavement is illustrated. The drawing is not to scale
and the inspection vehicle is not shown. ............................................................................................. 26
Figure 11: Two examples of area warning signs that convey rapid visual hazard-alerting messages. ..... 31
Figure 12: Photographs showing an IR viewer (left) and IR viewing cards (right). The photographs have
been reprinted from the Newport Corp. and Melles Griot online catalogs. ......................................... 33
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
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LIST OF TABLES
Table 1: Summary of the key emission characteristics and laser safety parameters of the LRMS, LRIS,
and LCMS products. ............................................................................................................................ 16
Table 2: Summary of the results of a risk assessment of the potential laser hazards that could occur for
the three dominant use cases involving the use of the LRMS, LRIS and LCMS equipments. ........... 28
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
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1 Introduction
1.1 Purpose and scope of this manual
This manual is intended to provide in-depth information and reasonable guidance about the various laser
safety issues related to the operation of three laser equipments manufactured by INO (Québec city,
Canada) for the inspection or road pavements. These equipments include:
1. The Laser Rut Measurement System (LRMS),
2. The Laser Road Imaging System (LRIS), and
3. The Laser Crack Measurement System (LCMS).
A large part of this manual is inspired from the content of four relevant laser safety standard documents,
these documents being the international standard IEC 60825-1 Edition 2.0 2007-03 [1], the technical
report IEC/TR 60825-14 First edition 2004-02 [2], and both American national standard documents ANSI
Z136.1-2007 [3] and ANSI Z136.6-2005 [4]. Section 1.3 gives the complete reference to each of these
documents. These standard documents are very detailed and they must have a broad coverage in order
to account for the characteristics of nearly all types of laser sources made available on the market. As a
result, it can be difficult for the inexperienced user to readily find in these documents the laser safety
information relevant to its own laser product. In addition, a rigorous laser safety assessment for any given
laser product requires that some emission parameters be calculated, which is not at the reach of many
individuals that do not possess a minimum technical background in this field. The present manual then
aims at providing laser safety information and data to the user so that the three laser systems can be
safely used and maintained without having to browse through the laser safety standards mentioned above
and without the need to perform complicated and lengthy calculations.
Because the three laser equipments covered by this manual are Class 3B laser products, Section 3.3 of
Ref. [2] recommends that a laser safety officer (LSO) be appointed in organizations that make use of
these laser products. The LSO should take responsibility, on behalf of its organization, for the
administration of day-to-day matters that relate to laser safety. The present manual is then intended to
serve as a sourcebook for the LSO that will have the responsibility to enforce adequate laser safety
practices and to set up the appropriate control measures for the safe use of either of the LRMS, LRIS or
LCMS laser equipments owned and/or used by its organization. The LSO may rely on the content of the
present manual, particularly in the absence of national or local laser safety regulations.
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
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The exposure to laser radiation emitted from Class 3B laser equipments such as the LRMS, LRIS, and
LCMS can be hazardous to the eyes, particularly if the exposure duration exceeds a few seconds while
the viewer’s eyes are at close proximity of the aperture from which the laser radiation is emitted (worst-
case viewing scenario). In addition, the level of laser radiation emitted by both LRIS and LCMS
equipments is sufficient to be considered unsafe for skin exposure. Fortunately, a short laser safety
training of the laser personnel along with the application of a few control measures that do not require
costly equipment will reduce the risks of laser hazards to an acceptable level. The specification of the
control measures is adapted to the specific laser emission characteristics of the equipments discussed in
this manual, and some of these characteristics help greatly in reducing the risks of laser hazards. It is our
opinion that the knowledge of these laser emission characteristics for the laser personnel will largely
contribute to decrease the general level of anxiety that is normally felt by any individual present in a
workplace that poses some health hazards.
1.2 Acronyms and symbols used in this manual
ANSI American National Standards Institute
CW Continuous wave
IEC International Electrotechnical Commission
IR Infrared
LCMS Laser Crack Measurement System
LED Light-emitting diode
LRIS Laser Road Imaging System
LRMS Laser Rut Measurement System
LSO Laser Safety Officer
MPE Maximum permissible exposure
N/A Not Applicable
NIR Near-infrared
NOHA Nominal Ocular Hazard Area
NOHD Nominal Ocular Hazard Distance
Hz Hertz (a unit of frequency)
J Joules (a unit of energy) Related units
*
: mJ (1 mJ = 10
−3
J)
*
Only the related units used in the manual are listed.
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
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m Meters. Related units: nm (1 nm = 10
−9
m), µm (1 µm = 10
−6
m), mm
(1 mm = 0.001 m), and cm (1 cm = 0.01 m)
W Watts (a unit of power) Related units: mW (1 mW = 10
−3
W)
s Seconds. Related units: µs (1 µs = 10
−6
s)
1.3 References
The documents listed below form part of the present manual to the extent specified herein. Each
document is referenced throughout the text of the present manual by its reference number enclosed in
brackets.
1. IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements,
International Electrotechnical Commission, Edition 2.0, 2007-03.
2. IEC/TR 60825-14, Safety of laser products – Part 14: A user’s guide, International
Electrotechnical Commission, First Edition, 2004-02.
3. American National Standards Institute, ANSI Z136.1-2007 American National Standard for Safe
Use of Lasers (Laser Institute of America, Orlando, FL, 2007).
4. American National Standards Institute, ANSI Z136.6-2005 American National Standard for Safe
Use of Lasers Outdoors (Laser Institute of America, Orlando, FL, 2005).
5. Laser Rut Measurement System Installation Manual Rev. 23, INO, Sept. 2008.
6. Laser Road Imaging System Installation Manual Rev. 13, INO, Oct. 2007.
7. Laser Crack Measurement System – Installation Manual Rev. 4, INO, Dec. 2009.
8. R. Mannix, “Human behavioral factors in laser safety”, J. Laser Appl., vol. 14, pp. 128-133, May
2002.
1.4 Order of precedence
In the event of conflict between the content of this manual and any of the reference documents listed in
Section 1.3, the reference documents take precedence.
1.5 Important Notice
This laser safety manual addresses hazards associated only to laser radiation emitted from the LRMS,
LRIS, and LCMS Class 3B laser equipments manufactured by INO. Other types of health hazards may
occur when using these laser equipments, and the reader is then invited to review the page entitled
GENERAL SAFETY WARNING in the installation manuals of the LRMS and LCMS equipments. At the
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
8
time of drafting the present version of this laser safety manual, the page cited above is still missing in the
installation manual of the LRIS. The present manual is provided for the sole convenience of the users and
appointed LSO. INO expressly disclaims liability for any injury to a person or damages of any nature
resulting from the use of or reliance on the content of this manual. In addition, INO makes no guarantee
as to the accuracy or completeness of the information contained in this manual.
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
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2 Emission Characteristics of the Laser Equipments
2.1 Basic characteristics of the laser radiation
2.1.1 Overview: The concept of laser line
The LRMS, LRIS and LCMS laser equipments manufactured by INO acquire transverse profiles of the
surface of the road pavement by illuminating it with laser radiation emitted from devices referred to as
either laser profiler units or laser sensor units, depending on the specific equipment. Each equipment
includes two identical laser profiler (or sensor) units, each unit enclosing a specific type of high-speed
camera and an emission module referred to as a laser line projector. The primary component of each
laser line projector is a high-power semiconductor laser diode rated for emission of about 7 watts (W) to
10 W of average output power. Prior to exiting from the output window of the laser line projector, the laser
beam emitted by the semiconductor laser diode passes through a properly designed optical system that
shapes the laser beam and then projects it in the form of an elongated thin line. The “laser line” has a
thickness (shortest dimension) of about 7 mm at the output window while its length (longest dimension) is
in the range of 4 cm (LRIS) to about 7 cm (LRMS and LCMS). The laser line spreads rapidly along its
length as it propagates away from the output window, so that it gets more and more elongated.
Depending on the specific mounting of the laser equipment, the laser line hits the road pavement after
propagation over a distance of about 2 m in the air. At the surface of the road pavement the laser line is
about 2-m long while its thickness gets reduced to a minimum of approximately 1 mm (LRMS and LCMS)
to 10 mm (LRIS). The laser lines projected from both laser profiler units superpose in such a way that
they illuminate a zone of about 4-m long on the road pavement.
2.1.2 Laser safety class and emission wavelength of the equipment
Depending on the specific laser equipment, each projected laser line carries a total average output power
that may vary from about 0.4 W to 7.5 W. This means that each laser profiler/sensor unit is a Class 3B
laser product, as determined by the manufacturer from the application of the laser classification
procedures detailed in either of the laser safety standards documents [1] or [3]. The classification of a
laser system gives a gross indication of its potential hazard resulting from exposure (both ocular and skin)
to the emitted laser beam. For instance, the level of laser radiation emitted by a Class 3B laser product is
such that incidental direct exposure of the eyes can be hazardous when left unprotected, even when the
exposure is brief. The risks of eye injury resulting form inadvertent ocular exposure are increased by the
fact that the emitted laser radiation is invisible when observed with the unaided eye. As a result, a viewer
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
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may be unaware that laser radiation is reaching his eyes, at least during a certain moment. The laser
profiler/sensor units emit laser radiation having a very narrow spectrum that peaks at a wavelength of 808
nanometers (nm). This emission wavelength is located in the near-infrared (NIR) spectral region, as seen
in the rightmost portion of the electromagnetic spectrum depicted in Figure 1 below. The figure also
shows that the visible region of the electromagnetic spectrum spans roughly from 400 nm (perceived as a
dark blue color) to 700 nm, this latter wavelength being perceived as a dark red color. The vertical red
arrow in the figure indicates the location in the electromagnetic spectrum of the 808-nm emission
wavelength of the laser profiler/sensor units. Although the 808-nm wavelength lies in close proximity of
the red boundary of the visible region of the spectrum, the spectral sensitivity of the human eye at this
wavelength drops by a factor of more than 100 000 as compared to its maximum sensitivity, which occurs
for yellow-green light at the 550-nm wavelength in daylight conditions (photopic vision). This explains why
the 808-nm laser light is not generally detectable by the unaided human eye.
Figure 1: Schematic illustration of a portion of the electromagnetic spectrum that spans
from the near ultraviolet up to the near infrared. The correspondence between the
wavelength scale and the perceived color of the visible light is illustrated. The vertical red
arrow locates the 808-nm emission wavelength of the laser equipments.
2.2 General considerations about the laser safety issues
2.2.1 Transparency and refractive properties of the main structures of the eye: Some
consequences
Similarly to visible laser radiation, a large part of the ocular safety issues posed by NIR laser radiation at
the 808-nm wavelength comes from the high transparency of the major structures of the human eye
(cornea, aqueous body, lens, and vitreous body) at this wavelength. The laser light entering into the eye’s
pupil is then free to propagate without attenuation throughout the eye to possibly inflict damage to the
retina. In fact, the main structures of the eye transmit electromagnetic radiation in the wavelength range
from 400 nm to about 1400 nm without significant attenuation, defining the so-called Retinal Hazard
Region, as illustrated in Figure 1. Moreover, the risk of damages to the retina increases dramatically due
800
Visible
Near Infrared
Ultraviolet
808 nm
Retinal Hazard Region 1400 nm
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
11
to the refractive properties of the eye’s lens and cornea combined with the high spatial coherence
properties of laser radiation. Both properties act together to allow laser radiation incident on the eye’s
pupil to get focused in a very small spot on the retina. The diameter of the laser spot can be as small as a
few tens of µm (micrometers) in some cases. As a result, laser light carrying an optical power of just a
few mW, as for most laser pointers for example, can produce an optical irradiance (or optical power
density) in the range of several kW/cm
2
(i.e., several thousands watts per squared cm) on the retina!
2.2.2 Maximum Permissible Exposure (MPE)
The ability of the eye’s lens and cornea to focus laser light on the retina and the transparency of the main
structures of the eye at wavelengths in the retinal hazard region has been properly accounted for in the
determination of the maximum optical irradiance levels that would be considered safe for direct exposure
of the eye to laser light, namely in conditions of direct intrabeam viewing. These safe irradiance levels,
generally referred to as the Maximum Permissible Exposures (MPEs), are tabulated in Tables 5a, 5b, and
7 of Ref. [3] as well as in Tables A.1 through A.3 of Ref. [1]. The MPE can be expressed either in units of
irradiance (W/cm
2
) or in units of radiant exposure (energy per pulse, J/cm
2
), depending on the specific
operation regime of the laser source. The MPE applicable for a particular situation depends on factors
such as the laser emission wavelength, the temporal operation regime (continuous wave, single pulsed, or
repetitively pulsed), and the transverse size of the laser source as seen with the eye (point source versus
extended source). The determination of the applicable MPE can be relatively involved, particularly when
dealing with a laser source operated in repetitively-pulsed regime and that qualifies as an extended
source.
2.2.3 Nominal Hazard Ocular Area (NOHA)
The fact that the LRMS, LRIS and LCMS equipments are Class 3B laser products means that the laser
lines projected from these systems have optical irradiance levels that largely exceed the applicable MPE
within a certain zone around their output window. The three-dimensional region of space wherein the
local irradiance (or radiant exposure) levels exceed the applicable MPE is denoted as the Nominal Hazard
Zone (NHZ) in Ref. [3] and as the Nominal Hazard Ocular Area (NOHA) in Ref. [1]. For the sake of
consistency, we will make use only of the latter acronym throughout the present document. The
dimensions and shape of the NOHA vary according to the specific laser equipment, and they are
described at length in Section 3. It is essential that any individual that has to work with these laser
equipments be aware of the NOHA determined for the specific laser equipment in use. In addition
to the engineering control measures implemented in a laser product, some safety precautions and control
measures must be taken when operating a Class 3B laser product to prevent inadvertent laser exposures
to the eyes of individuals standing within the NOHA. The safety precautions and control measures include
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
12
administrative/procedural controls (policies, laser safety instructions, training, hazard warning signs) as
well as personal protective equipment such as laser protective eyewear. The extent and nature of the
recommended safety precautions and control measures vary according to a few typical use cases that we
have identified. These use cases are detailed at length in Section 4 of this document.
As stated in Section C.2 of Annex C of Ref. [1], Class 3B laser products are normally hazardous when
intrabeam ocular exposure occurs, including accidental short-time exposure. On the other hand, viewing
diffuse reflections is normally safe. A diffuse reflection occurs for example when a laser beam hits a
matte, non glossy surface. The most powerful Class 3B lasers may even produce minor skin injuries or
even pose a risk of igniting flammable materials. However, this could happen only when the laser beam
has a very small diameter or is focused, which is not the case for any of the LRMS, LRIS, or LCMS laser
equipment.
2.3 Typical viewing scenarios and related laser hazards
Figure 2 shown below depicts four representative viewing scenarios along with the associated risks of
ocular injuries resulting from exposure to laser radiation emitted from a laser line projector. Although the
basic configuration illustrated in the figure pertains to the LRMS equipment, the information holds for the
LRIS and LCMS equipments as well.
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
13
Figure 2: Schematic illustration of four representative viewing scenarios labeled from A
to D, with the associated risks of laser hazards decreasing with increasing order.
As expected, the greatest laser hazards occur during direct intrabeam viewing (scenario A in the figure),
with the eyes of the observer located in the NOHA associated to the laser equipment. Note that ocular
injuries could result even if the observer is not looking right at the output window of the laser line projector.
In fact, the precise direction of the observer’s gaze will determine the region of its retina hit by the laser
light that enters in its pupil. Laser hazards of nearly the same severity could occur when an object located
in the NOHA has a surface that reflects laser light in a specular manner (i.e., like a mirror), as illustrated
by the scenario B in the figure. For both scenarios A and B, the severity of the potential ocular injuries
increases as the laser exposure lasts longer and as the observer’s eyes get closer to the output window
from which the laser radiation is emitted.
Road pavement
Laser
profiler
unit
C:
Looking at
the laser line
projected on the
ground is not
hazardous.
DANGER
CLASS 3B LASER
D:
Looking at the
output window
from a location
outside of the
NOHA is not
hazardous.
B: DANGER
Indirect
intrabeam viewing. The laser
light directed to the eyes after
reflection from any object with a
highly-
reflecting surface and lying
within the NOHA is hazardous.
A: DANGER
Direct
intrabeam viewing. Having
the laser radiation directly
projected in the eyes is
hazardous, even if the
observer is not looking at
the output window.
Illuminated
line area on
pavement
Invisible
laser
radiation
Reflectin
g
object
Output window
of the laser
line projector
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14
Note that some peculiar features of the laser radiation emitted from the LRMS, LRIS, and LCMS laser
equipments help in reducing the risks of ocular hazards. For instance:
• The projected laser lines spread with a divergence angle in the order of 50° along the direction
parallel to their length. Stated otherwise, the length of the laser line increases rapidly as one
moves away from the output window of the laser radiation source. This means that the local
irradiance of the laser lines decreases rapidly with the distance from the output window. Note that
the local irradiance is nearly uniform along the length of the projected laser lines.
• Although the NOHA for each of the three laser equipments is fully detailed in Section 3, it can be
said that it corresponds to the region of space delimited on one end by the surface area of the
output window from which the laser line is projected, and on the other end by the surface area of
the zone of the road pavement that is illuminated by the laser line. From the area depicted in red
in Figure 2, the outer shape of the NOHA can then be imagined as a triangular thin sheet of a few
mm thick, with its summit located at the output window and its base on the road pavement. Note
that the triangular thin sheet extends vertically for both LRIS and LCMS laser equipments.
• The laser radiation propagates unenclosed (open path) over an on-axis distance that does not
exceed 1.9 m to 2.3 m before hitting the road pavement. The exact distance depends upon the
specific laser equipment and its installation on the inspection vehicle. The on-axis distance at
which the local irradiance of the laser beam has reduced to the applicable MPE is referred to as
the Nominal Ocular Hazard Distance (NOHD). Beyond this distance there is no hazard to the
unaided eye, although laser exposure should always be avoided. As stated in Section 5.5.2 of
Ref. [2], for outdoor applications, it the beam is terminated by the ground, a tree line or other
terrain features, the NOHD cannot exceed the line of sight of this opaque feature.
• Viewing scenario C in Figure 2: A dry road pavement has a matte gray-black surface, which
reflects laser light mostly in a diffuse manner. The laser power incident on the road pavement is
then redirected over a broad angular extent. For the specific LRMS, LRIS, and LCMS Class 3B
laser equipments, viewing directly the area illuminated on the road pavement is not hazardous to
the eyes for any viewing duration and distance from the illuminated area.
• Viewing scenario D in Figure 2: By definition, the local irradiance level of the projected laser lines
is below the applicable MPE out of the NOHA determined for the laser equipment. As soon as the
observer is standing outside of the NOHA and that uncontrolled specular reflections of the laser
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
15
lines do not take place, there is no risk of ocular injuries even when looking at the output window
of a firing laser line projector.
• The accidental direct intrabeam viewing of the laser lines by using magnifying visual instruments
such as binoculars or telescopes is not reasonably foreseeable, even though the laser lines
propagate unenclosed in an outdoor setting. This is due to the specific locations of the laser
projector/sensor units when properly installed on an inspection vehicle combined with the peculiar
geometry of the laser lines projected downward.
2.4 Emission characteristics and laser safety parameters of each laser
equipment
The key emission characteristics and laser safety parameters pertaining to the three laser equipments are
reported in Table 1 below. The numbers printed in superscript refer to informative notes appended to the
table. Unless otherwise stated, the data reported in the table holds for a single laser profiler/sensor unit.
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16
Specification LRMS LRIS LCMS
Emission Characteristics
Laser class
1
: 3B 3B 3B
Emission wavelength: 808 nm 808 nm 808 nm
Number of profiler/sensor units: 2 2 2
Emission regime: Repetitively pulsed CW CW
Peak output power: 5 W 7.4 W 4.9 W
Average output power: 1.25 W 7.4 W 4.9 W
Total energy per laser pulse: 5 mJ N/A N/A
Pulse repetition rate: 250 Hz (max.) N/A N/A
Duration of each laser pulse: 1 ms N/A N/A
Laser beam divergence (L × T)
2
: ∼52° × −0.15° ∼45° × 0.06° ∼50° × −0.17°
Size of laser line at output window: 7.5 × 0.7 cm
2
4.25 × 0.8 cm
2
7.3 × 0.7 cm
2
Size of laser line on road pavement: ∼233 × 0.1 cm
2
∼190 × 1 cm
2
∼200 × 0.1 cm
2
Laser Safety Parameters
Applicable MPE (irradiance units)
3
: 2.3 mW/cm
2
1.6 mW/cm
2
1.6 mW/cm
2
Applicable MPE (radiant expos. units)
3
: 0.0093 mJ/cm
2
N/A N/A
Accessible irradiance level
4
: 50 mW 304 mW 160 mW
Accessible radiant exposure level
4
: 0.2 mJ N/A N/A
NOHD (normal use)
5
: 2.3 m 2.2 m 2.2 m
NOHD (unobstructed beam): 5.7 m 14.3 m 11.3 m
Optical density for safety eyewear
6
: 2.0 or higher 3.1 or higher 2.8 or higher
Skin exposure to the laser beam
7
: Safe Safe beyond 35 cm
Safe beyond 17 cm
Table 1: Summary of the key emission characteristics and laser safety parameters of the
LRMS, LRIS, and LCMS products.
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17
Notes:
1. The laser classification of each system has been carried out according to the ANSI Z136.1-2000
Standard document. The laser classes do not change when classifying according to the latest
editions ANSI Z136.1-2007 [3] and IEC 60825-1 Ed. 2.0 2007-03 [1].
2. (L × T) means Length × Thickness. The negative values reported for the beam divergence along
the thickness dimension means simply that the thickness of the laser line decreases for the laser
beam propagation path from the output aperture of the laser projector down to the road pavement.
3. MPE for intrabeam ocular exposure. The reported values apply only for the unaided viewing
condition, and they were calculated using a total expected or anticipated exposure duration of 10
s for near-infrared wavelengths, as recommended in Table 2 and in Par. 8.2.2 of Ref. [3]. The
determination of the MPE applicable to each laser profiler unit of the LRMS made use of the
extended source condition, leading to the introduction of a multiplicative correction factor C
E
having a value of 4. The MPEs expressed in radiant exposure units are determined on a per-
pulse basis.
4. Used mainly for laser classification purpose. This parameter represents the laser beam power (or
energy per pulse) enclosed within a 7-mm diameter circular aperture placed at a distance of 10
cm from the exit aperture of the laser projector and centered on the cross-sectional area of the
laser line.
5. The NOHD for normal use of the system is given by the length of the laser beam centerline
segment starting at the exit aperture of the laser profiler unit and terminating on the surface of the
road pavement. The exact NOHD value then depends on the height of the laser profiler relative to
the ground floor.
6. The reported optical density values have been determined according to the worst-case scenario of
direct intrabeam viewing with the observer’s eyes located in close proximity of the exit aperture of
the laser projector unit. Refer to Section 4.4.2 for further details about the laser protective
eyewear.
7. Based on a MPE of 330 mW/cm
2
for skin exposure to an 808-nm wavelength laser beam. The
local irradiance level for the LRIS is below this MPE at distances z beyond 35 cm from the exit
aperture of each laser projector, while the corresponding minimum distance is 17 cm for the
LCMS.
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
18
3 Detailed Specification of the Nominal Ocular Hazard Areas
This chapter provides a detailed description of the NOHAs associated to the laser profiler/sensor units that
form part of the LRMS, LRIS, and LCMS laser equipments. Each of these equipments is discussed in a
separate section of the present chapter, so the reader is invited to refer to the section that relates to its
own equipment. The descriptions are mostly visual since they rely on figures that show schematic front
views and side views of the NOHAs, and they start with a view showing the setup configuration of the
product as typically installed on the inspection vehicle.
3.1 NOHA for the LRMS
Each LRMS include two identical laser profiler units mounted in an inspection vehicle the way as depicted
schematically in Figure 3 below. The zones depicted in light blue color in the figure indicate the field of
view of the camera enclosed in the upper part of the laser profiler units. During operation of the LRMS,
invisible laser radiation is emitted from the laser line projector enclosed in each laser profiler unit. The
laser radiation is depicted in light red color in Figure 3. The laser radiation escapes from the bottom
output window and it propagates towards the road pavement with a tilt angle of about 21° relative to the
horizontal. This means that the projected laser line strikes the surface of the pavement at a horizontal
distance of about 2.2 m from the rear panel of the inspection vehicle when the bottom of each laser
profiler unit is set at the nominal height of 0.85 m above the ground floor.
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
19
Figure 3: Illustration of the typical setup of the LRMS installed in an inspection vehicle.
The schematic front view and side view illustrated in Figure 4 and Figure 5, respectively, detail the shape
and dimensions of the NOHA defined for each laser profiler unit of the LRMS. The NOHA corresponds to
the zone depicted in red color. Note that the inspection vehicle is not shown in these figures. The length
of the projected laser line expands progressively with the distance to reach a value of about 2.33 m when
hitting the road pavement. For both regular and tilted mounting configurations (see Section 3.1 of Ref. [5]
for further details), the laser lines projected by the pair of laser projectors are oriented such that the overall
length of the illuminated area on the pavement attains about 4.1 m.
In Figure 5, the factor by which the local optical irradiance exceeds the applicable MPE is given by the
labeling depicted in red color. This factor has been determined for the zones around both limits of the
laser line propagation path.
Laser profiler
unit (panel
cover removed)
Field of
view of th
e
camera
Invisible laser radiation
Typical setup for the LRMS
LRMS, LRIS, and LCMS Laser Safety Manual (Rev. 2)
20
Figure 4: Schematic front view of a LRMS laser profiler showing the geometry of the
laser beam for its propagation path from the output window down to the road pavement.
The drawing is not to scale and the inspection vehicle is not shown.
∼
0.85 m
∼2.33 m
Laser
profiler
Laser beam
centerline
Road
pavement
Output window
of the camera
Output window
of the laser line
projector
Schematic Front View (LRMS)
∼
52°
NOHD
= 2.3 m
DANGER
CLASS 3B LASER
Warning lights
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