When is an LED hazardous to your eyes?

[gijim]

Is there a way to calculate the danger like they do with lasers? I have 18 watts worth of LED's in a reflector. I know it is extremely bright, and looking at it directly for a split second will cause "floating images" in my vision for a few minutes.

So I know it's not good to look at, but "how not good"? Can it cause blindness? I have the specs for the LED's...

 

[Skogsgurra]

Sounds like it is "not as good" as looking into the sun. Wording gets in my way. I mean that it is as bad as looking into the sun.

Have no idea if risk can be calculated. But arc welding definitely produces eye problems if you look at the arc for a few seconds. Thought that was due to UV radiation, though.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[MadMango]

Have a read over this article, it mentions some standards that you can probably reference.

[green]"Art without engineering is dreaming; Engineering without art is calculating."[/green]

Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[itsmoked]

If you think about it we have evolved to tolerate sunlight. All day in full sunlight at the equator is a reasonable limit to how bright something can be. Picture a sunlit beach. As soon as you up the light from that - sunlit snow - you are going to have/cause problems. Hence the need for goggles or slits.

If you think of a light bulb most incandescents of 100W or more are going to have surface brightnesses that exceed sunlit snow.

So looking directly at a light bulb is painful and not advised and probably physiologically controlled via pain/learning.

Now when you get to light sources that are as bright as the Sun's surface you have a different problem. That being that a brief glimpse or a non-center-of-vision view can do harm.

In my university work I worked with lasers constantly. In one case I had to assist with the alignment of a Argon Ion laser at a commercial grating maker. Before I went I did the calculations on the spot brightness. It was about 10 times the surface brightness of the sun. This means that as your eye sweeps across any surface that the beam is striking you risk instant retinal tracking. Even worse because the laser's light was in the visible spectrum your eye will attempt perfect focus of the spot. Furthermore human nature is to look directly at bright colored spots. I took this information to the customer and pointed out that if that beam hit anything in the room even a mat finish and a person looked at it even briefly they were in trouble. No one should even enter the cell without eye protection. We subsequently accidentally drilled a hole thru one of the spacial filters by briefly misaligning the beam path.

So if your light is not meant to be 'looked at', (bright sunlit snow), and is not so bright as to cause instant or near-instant damage,(bright as the Sun's surface), you probably don't have anything to be concerned with.

Just do the math.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[samyer8741]

In my previous life I designed lasers and laser control systems. A typical LED is not a laser. However, depending on the wavelength and power an LED could be detrimental to your eyes. If this is still an issue, and these are laser diodes you are working with then most definitely consider contacting the Laser Institute of America. They can give you the specifics on classifications of lasers. There are numerous factors in determining the safety of a laser so it's not an easy question to answer. Depending on the wavelength and power of a laser there are different effects to human exposure.