Indirect laser reflections.

Can indirect reflections (off a clear LED)  from a cheap 5-10mW laser pointer for about 30sec-1min be harmful? If so, how would you know if damage had been done?

Bad news, you're going to die.

Good news is its not now. Anything in the cheapo range of hand-held laser diodes (i.e. under 50 mW) won't do anything except give you a headache, and and most indirect exposure from most lasers even in the several watt range won't do much.
7654321 (author)  The Ideanator3 years ago
W00t. Ok thanks, I thought I was overreacting... just making sure...
kelseymh3 years ago
From the Wikipedia laser safety article I cited previously,
Van Norren et al. (1998)[19] could not find a single example in the medical literature of a <1 mW class III laser causing eyesight damage. Mainster et al. (2003)[20] provide one case, an 11 year old child who temporarily damaged her eyesight by holding an approximately 5 mW red laser pointer close to the eye and staring into the beam for 10 seconds, she experienced scotoma (a blind spot) but fully recovered after 3 months. Luttrulla & Hallisey (1999) describe a similar case, a 34 year old male who stared into the beam of a class IIIa red laser for 30 to 60 seconds, causing temporary central scotoma and visual field loss. His eyesight fully recovered within 2 days, at the time of his eye exam. An intravenous fundus fluorescein angiogram, a technique used by ophthalmologists to visualise the retina of the eye in fine detail, identified subtle discoloration of the fovea.

(see the article itself for citations).
kelseymh3 years ago
The Ideanator has already answered your first question; indirect reflection from a class 1 laser is not harmful.

As for your second, the main problem is that your retina has no pain sensors, you you won't know whether or not any damage has been done. Don't ever work with visible lasers above 30 mW (class 4) without proper eye protection. Don't work with any infrared lasers without proper eye protection (IR filters). An IR beam can locally boil the vitreous humor (fluid inside your eye) and destroy portions of the retina.

Laser burns from ~30 mW class devices generally affect only a small part of the retina, causing "blind spots." Your brain is already set up to interpolate images to work around blind spots (the optic disk, in particular), so you're unlikely to notice anything unusually. Only an ophthamological examination can tell if you've taken this sort of damage.

Higher powered lasers can damage large areas of the retina; in severe cases, they can cause complete loss of sight in the affected eye.

The laser safety Wikipedia article is a good introduction for home users. The information is accurate and extracted from appropriate ANSI and OSHA documents (even where not fully cited).
orksecurity3 years ago
Cheap laser pointers: I agree, I wouldn't worry about them. If you look at their rating, they tell you not to _stare_ into the beam, but a glance shouldn't do damage.

If it was one of the higher powered cutting/burning lasers folks have described elsewhere on Instructables, I'd strongly suggest safety goggles and/or beam stops to prevent the issue from arising. This is something where you can cause yourself significant damage without feeling it. Not everything described on Instructables is safe if you don't already know enough to take proper precautions.