Have you ever sat in a lecture where an over-enthusiastic lecturer is waving his arms around excitedly, forgetting he is holding a laser pointer, and wondered what would happen if he accidently shone the beam into your eyes? Surely, you might think, the makers of laser pointers have anticipated such things. Well, last week I attended a training course on laser safety and I found out the answer, which, I’m afraid, isn’t necessarily re-assuring.
Class 1 lasers are considered ‘safe’, by which we mean they won’t cause lasting damage if the beam hits your eyes. The beam simply does not contain the power to do so. But please, don’t try this out at home. Class 2 lasers are also ‘safe’ against mis-use by excitable teachers, because of your blink reflex – if the light hits your eyes you will naturally take aversion measures (like blinking) and that limits the energy that gets focused onto your retina to a level such that it won’t cause permanant problems. However, not all laser pointers turn out to be Class 1 or 2. Some are Class 3B, which are considered unsafe for eyes, even with the blink reflex. And don’t think you can assume that a ‘dim’ laser pointer is safe; remember that you can only see light within a certain range of wavelengths, and there may be considerable power in the beam in invisible infra-red light.
Nasty class 3B pointers can be bought cheaply over the internet, and, in some cases, are mis-labelled so you might think they are safe. Little wonder that some laser pointers are now considered a prohibited weapon in New South Wales.
All this means that you should ask your lecturer questions about his laser pointer, and how he uses it.