LIA NEWS
NEWS FROM LIA T
he classification of lasers by the product’s manufacturer – from class 1 to class 4 – is a valuable means to provide the end user with simplified information about the potential
hazards to the eyes and skin. Te concept of product classification can be considered a success story. Developed in the USA by the Center for Devices and Radiological Health (CDRH) in the 1970s, it has been accepted internationally for more than 30 years, based on the standard IEC 60825-1. While the basic system of classification has
remained unchanged, some adjustments were necessary over the years and will be in the future, when reacting to new types of lasers and scientific data on injury thresholds. For a few years, diffractive optical elements (DOE) and micro- scanners have driven a large group of new products, mainly gesture controls and 3D cameras for consumer electronics, but also scanned lidars for machine vision and autonomous cars, as well as pico-projector scanners. For these new products, the combination of factors results in challenges for product safety and standardisation. Tey are not intended as specialised professional products, but are for consumer use. Terefore, they would need to be class 1, class 2 or
class 3R devices, depending on wavelength range and country, but also, for a satisfying performance
ABOUT LIA
Laser Institute of America (LIA), founded in 1968, is the professional society for laser applications and safety. Its mission is to foster lasers, laser applications and laser safety worldwide.
www.lia.org
13501 Ingenuity Drive, Ste 128, Orlando, FL 32826, +1 407.380.1553
www.lasersystemseurope.com | @lasersystemsmag
on engineering safety features are currently in development… at IEC to permit higher emission levels for divergent or scanned systems
Two concepts based
New products call for adjusted laser
safety classification concepts By Karl Schulmeister, Seibersdorf Laboratories
in terms of detection distances, emission levels need to be relatively high. Because of the diverging or scanned nature of the emission, these systems suffer particularly from the conservative combination of classification rules of a 7mm diameter pupil, an assumed exposure distance of 10cm from the DOE or the scanning mirror, together with an assumed accommodation to the apparent source at such short distances. While laser safety classification was always historically on the conservative side, it might be possible in the future to consider that the combination of those three exposure conditions is not only highly unlikely, there are also reflexes that result in pupil constriction when accommodating to a close target. Defining measurement (pupil)
diameters smaller than 7mm for very close distances might be a possible relaxation for future amendments, but would make the analysis more complex. Also, possibly, emission limits can be raised somewhat in the nanosecond and lower microsecond regime, which is a
task for the International Commission on Non-Ionizing Radiation Protection (ICNIRP) to which the IEC refers for bio-effects committee work. Particularly for a change in the emission limits, the general predicament exists that the injury thresholds depend on a very complex manner on wavelength, pulse duration and retinal spot size. When emission limits for products – or exposure limits for the eye – are to be made to reflect the thresholds more accurately to reduce needlessly large safety margins, it makes the limits more complex since simple limits by default would be, for many scenarios, over-restrictive. One exception in the 2014 IEC and ANSI revision applied to small retinal sources, where it was possible to greatly simplify the analysis of pulsed emission by setting the multiple pulse correction factor CP (or C5) to unity, at the same time permitting significantly higher emission levels compared to earlier editions.
There are new safety challenges for classifying gesture control devices and 3D cameras for consumer electronics
On the other hand, in the same revisions, the analysis of extended retinal images became more complex but permitted much higher emission levels for devices in the range of the lower ‘safe’ classes. Besides possible adjustments in the emission
limits, two concepts based on engineering safety features are being developed through the standardisation committee at IEC to permit higher emission levels for divergent or scanned systems – but still achieve classification as ‘safe’ class, such as class 1 for infrared and class 2 for visible emission. One concept is a virtual protective housing
(VPH), where the emission is automatically reduced when an object enters the VPH. One or more sensors monitor protected volume. Outside of the protected volume, the emission needs to be below limits for the class that is to be achieved, such as class 1. When the VPH is free of relevant objects, the emission level in that volume can be higher: as long as human access to this radiation is prevented by the system, it is not relevant for product classification. Te sensor system establishes a virtual protective housing instead of a real one, and defines what is referred to as the ‘closest point of human access’. Te second concept applies to lasers mounted on
vehicles and other moving platforms. When the vehicle is stationary, only normal emission levels are permitted. When it is at a certain speed, it can be
ISSUE 36 • AUTUMN 2017 LASER SYSTEMS EUROPE 35
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40
