7.4 Lasers

Question 1

The word laser is an acronym, which stands for

Answer 1

Light Amplification by the Stimulated

Emission of Radiation

Question 2

A laser beam is electromagnetic radiation just like the light from a lightbulb, but
unlike the lightbulb: 4

Answer 2

 the beam of light is monochromatic, i.e. it emits light of a single wavelength (or
small number of wavelengths)
 the beam may be in the infrared, visible or ultraviolet regions of the spectrum
depending upon the active medium
 the individual waves of a laser beam are ‘in phase’ – the laser beam is coherent
 the beam is usually highly collimated (i.e. has low angular divergence and does
not ‘spread out’ significantly with distance).

Question 3

Laser products are classified to take account of

Answer 3

the amount of laser beam which can

be accessed when the product is in normal use or during routine user maintenance.

Question 4

Class 1

Answer 4

Safe under reasonably foreseeable conditions of operation.

Question 5

Class 1M

Answer 5

As Class 1 but not safe when viewed with optical aids such as eye loupe
s or binoculars.

Question 6

Class 2

Answer 6

(Visible laser beams only) The eye is protected by the aversion respons
es, including the blink reflex and head movement.

Question 7

Class 2M

Answer 7

As Class 2 but not safe when viewed with optical aids such as eye loupe
s or binoculars.

Question 8

Class 3R

Answer 8

More likely to cause harm to the eye than lower class lasers but do not n
eed as many control measures as higher class lasers.

Question 9

Class 3B

Answer 9

Eye damage likely to occur if the beam is viewed directly or from shiny
reflections.

Question 10

Class 4

Answer 10

Eye and skin damage likely from the main laser beam and reflected bea
ms. These lasers may cause fires.

Question 11

Laser health effects

Potential health hazards are dependent upon a range of variables, including: 4

Answer 11

  Laser light wavelength 
  Beam intensity 
  Distance from the laser 
  Power of the laser: 
-  average power over long intervals  
-  peak power produced in a pulse.

Question 12

The wavelength of the laser radiation is significant

because

Answer 12

only light within the retinal hazard region
(wavelength range of approximately 400 to 1400 nm)
can penetrate the eye sufficiently to damage the retina.