An Overview of the Laser Classification System

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Phil Marsh
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An Overview of the Laser Classification System

Post by Phil Marsh » Sun Jun 15, 2008 9:01 am

In 2001 the standard governing the safety of laser products in Europe (EN) and Internationally (IEC), was substantially revised and the Classification system was overhauled. This resulted in the introduction of three new laser classes (1M, 2M and 3R) and the abolition of Class 3A. Below is a brief description of each of the current laser classes.

The 60825-1 standards apply equally to lasers and LEDs. In most places we have used the word "laser", but it can be replaced by "LED". Generally speaking LEDs would be in the lower Classes (1, 1M, 2, 2M, 3R), but very exceptionally may be Class 3B. At the time of writing we are not aware of any Class 4 LEDs*.

The phrase "eye-safe" is used below. Please note that "eye-safe" is applicable to the whole optical spectrum from 180nm to 1mm wavelength, not just in the retinal hazard range of 400nm to 1400nm. Outside the retinal hazard range there is potentially a hazard to the cornea. A wavelength outside the retinal hazard range is therefore not automatically eye-safe!

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Class 1
This class is eye-safe under all operating conditions.

Class 1M
This class is safe for viewing directly with the naked eye, but may be hazardous to view with the aid of optical instruments. In general, the use of magnifying glasses increases the hazard from a widely-diverging beam (eg LEDs and bare laser diodes), and binoculars or telescopes increase the hazard from a wide, collimated beam (such as those used in open-beam telecommunications systems).

Radiation in classes 1 and 1M can be visible, invisible or both.

Class 2
These are visible lasers. This class is safe for accidental viewing under all operating conditions. However, it may not be safe for a person who deliberately stares into the laser beam for longer than 0.25 s, by overcoming their natural aversion response to the very bright light.

Class 2M
These are visible lasers. This class is safe for accidental viewing with the naked eye, as long as the natural aversion response is not overcome as with Class 2, but may be hazardous (even for accidental viewing) when viewed with the aid of optical instruments, as with class 1M.

Radiation in classes 2 and 2M is visible, but can also contain an invisible element, subject to certain conditions.

Classes 1M and 2M broadly replace the old class 3A under IEC and EN classification. Prior to the 2001 amendment there were also lasers which were Class 3B but were eye-safe when viewed without optical instruments. These lasers are Class 1M or 2M under the current Classification system.

Class 3R
Radiation in this class is considered low risk, but potentially hazardous. The class limit for 3R is 5x the applicable class limit for Class 1 (for invisible radiation) or class 2 (for visible radiation). Hence CW visible lasers emitting between 1 and 5 mW are normally Class 3R.
Visible class 3R is similar to class IIIA in the US regulations.

Class 3B
Radiation in this class is very likely to be dangerous. For a continuous wave laser the maximum output into the eye must not exceed 500mW. The radiation can be a hazard to the eye or skin. However, viewing of the diffuse reflection is safe.

Class 4
This is the highest class of laser radiation. Radiation in this class is very dangerous, and viewing of the diffuse reflection may be dangerous. Class 4 laser beams are capable of setting fire to materials onto which they are projected.

Any laser product of a given Class may contain 'embedded' lasers which are greater than the Class assigned to the product, but in these cases engineering controls (protective housings and interlocks) ensure that human access to radiation in excess of product Class is not possible. Notable examples of this are CD and DVD players which are Class 1 laser products while containing Class 3R or Class 3B lasers and laser printers which are Class 1 laser products but contain Class 4 embedded lasers.

Note:- for a product to be classified correctly, it must be tested at the maximum output accessible under reasonably foreseeable single-fault conditions (eg in the drive circuitry). A non-M class product must pass both Condition 1 and Condition 2 of Table 10 in IEC/EN 60825-1, and an M-class product (which by definition has failed either Condition 1 or 2) must pass the irradiance condition in the same table.

* Generally speaking lasers are point sources while LEDs are extended sources. Extended sources have higher power limits than point sources for a given laser Class. Therefore a visible LED emitting 10 mW may be Class 2, while a visible laser pointer of the same power would be Class 3B. NB Laser pointers above Class 2 are banned for sale to the public by trading standards.

CW = Continuous Wave - i.e. not pulsed.
Diffuse reflection = The reflection of radiation from a matt surface such as a wall.
Extended source = Having an apparent source size with angular subtense of greater than 1.5 mradian
Optical instruments = Binoculars, telescopes, microscopes, magnifying glasses (but not prescription glasses).
Point source = Having an apparent source size with angular subtense of less than 1.5 mradian.

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Re: An Overview of the Laser Classification System

Post by tlubic » Thu Dec 14, 2017 8:48 pm

A possible new client was asking if the Class 1 Eye safe laser from my Trimble TX8 would set off the fire eyes in their compressor stations. Would anyone happen to know? Thanks.

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