Maximum safe 532nm for kids

[pbolger]

I took my kids to a science museum yesterday, and was a little shocked to see an interactive exhibit demonstrating the classic laser intrusion detection system - a matrix of lasers set up across a dark room set up so a bell sounds if one of the beams is interrupted. The lasers appeared to be 10-20mw dpss 532nm.

Only thing is, instead of doing the obvious and having the lasers cut out when interrupted they stay on. At kids' eye level.

My feeling is that lasers should never be left on unattended in a public area, particularly within reach of children

Does anyone have any thoughts on whether this could be considered 'safe'?

[andy_con]

id say a watt, but buy them eye lids to use when viewing it

joking....

[Xytrell]

The lasers appeared to be 10-20mw... across a dark room

Lasers appear brighter in the dark. I'm fairly certain safety was a top consideration in the design of the exhibit.

[pbolger]

My point is more that I'm not sure if it would be safe to allow a child to look straight into any 532nm laser.

[gogu]

I've been told eyesafe = 1mw or lower but the again if you read sams laser faq laser safety http://members.misty.com/don/lasersaf.htm#safyor1
Check the comparison of a 1mw hene and looking into the sun.. interesting

[White-Light]

A static beam is always potentially dangerous although with powers of less than 5mw its usually assumed that the aversion reflex is quick enough to make someone turn away before damage can occur. Beam width is also going to have a bearing on safety.

I'm not sure children's eyes are any more sensitive to retinal burning than adults eyes although I stand to be corrected on that.

[frothychimp]

Bring a nifty coherent laser check and stick it in the beam, lol. I see you are in NZ so I'm not sure what the laws are regarding public display. Here in the U.S. you need a variance and that would be available to answer power questions.

The <5mW limit or Class 3a is really for the hobbyists as their use of lasers runs contrary to safety in that they want to see the beam. In reality, beams should be attenuated to Class II or I for real safety. Only a minimal amount should pass for visible light to identify the beam. The OD ratings on glasses only give a fundamental idea, a simple heuristic, of protection. The actual calculations made by LSO (laser safety officers) takes into account the wavelength, the operating mode, exposure times, distance and several other factors to actually calculate the required OD. It's possible those calculations were performed for this demonstration. The only way to be sure is ask.

[Steve Milani]

A static beam is always potentially dangerous although with powers of less than 5mw its usually assumed that the aversion reflex is quick enough to make someone turn away before damage can occur. Beam width is also going to have a bearing on safety.

I'm not sure children's eyes are any more sensitive to retinal burning than adults eyes although I stand to be corrected on that.

I agree. Absolutely.