A bit more reading suggests the laser is the old class 3A which places it in 1M or 2M which is safe unless viewed through opical instruments.

Also how is viewing via a USB scope dangerous as you will be looking at the screen which will not be the same wave length as the actual lazer?

Lasers for scientific and alignment purposes were pretty much a fixture of my working life prior to redundancy in 2004. As were arguments concerning whether or not the thing in question was actually safe! The calculations involved to resolve a specific case are not simple and justifying the assumptions on the optical side can be even harder. By the early 2000s the expanding elf'n safety industry had produced regulations whose local interpretation tended to go well past the sanity event horizon accelerating hard towards total lunacy. Much unofficial internet data is a reaction to this and does assume a certain level of "what's actually going on" understanding so that you can use safe working practices appropriate to your situation.

Fortunately the official side seems to have come back down to earth with some practical guidelines. See **LINK** for chapter and verse. As Martin says for red diodes the basic eye-safe rule is no more than 1 mW into a dark adapted (7 mm pupil diameter) eye. In practice for a device emitting a laser beam this means class 2, or class 2M where the beam from a more powerful source is expanded so only 1 mW can enter the eye which is clearly not relevant here. Eye safe in this context refers to distraction and visual after effects not tissue damage.

Class 3a was devised as a fudge to allow a more useful range of laser powers to be employed in fairly open environments without the rigourous precautions necessary when using something powerful enough to do physical damage. In a device emitting a beam accessible to the untrained user class 3a implies that the 1 mW into a dark adapted eye is met for the intelligent user by suitable beam expansion. So for a laser centre finder with a class 3a emitter would be expected to focus down to a small dot at a fairly short working distance after which it would expand so as to meet the 1 mw criteria at a reasonably short range. I guess a couple or three feet would do to meet the letter of the regulation. In practice class 3a can be considered a low power subset of class 1M assuming that no one would market an unconditionally safe class 2 device as class 3a. I saw plenty of class 3a labels but never saw a true class 3a emitting device. The (valid) assumption was that user safety would be arranged by the experienced designer or researcher by beam expansion, beam blocks or access control as appropriate.

Bottom line is that any laser centre finder sold into the general market should be a class 2. 3a power levels are way over the top, except maybe in very special circumstances. I've used 3a emitters as alignment devices at over 5 miles!

When it comes to laser reflections its unwise to assume you won't do something daft. Optics labs are matt black pretty much everywhere for good reason.

Clive

I am surprised at the intensity of this laser. I have a couple of very small, cheap laser pointers (these usually use reject modules that are not prefect – one of them produces a clearly oval spot, although it has very little divergence). One of them was about £1 at a boot sale and came with dozens of tiny holographic projectiuon end caps, (mostly useless trivia like santa), but one of them is a neat cross hair. It is very fine and if I can ever figure out a way of fixing it to an arbor accurately it would make a neat centre finder, and not hugely bright. It has a safety advantage that it diverges with the cap on as well.

With the product in ME, I wonder if the adjustment is only accurate for one distance?

Neil

@Loft76 – I've had on of these for a while and I've not been able to get comfortable using it for anything other than aligning edges, a milling vice for example, for which it is really good. For finding a centre (ie a 2D x,y position) I can never work out the tolerance the thing works to.

I certainly hadn't thought about how safe the laser might be, but as you say with the collimator fitted, I do switch off the machine lights to see the spot. Without the collimator, "splashes" of laser light are noticeable as you move the workpiece around, but how dangerous these are, haven't a clue.

Steve