How bright is your Q-switched Nd:YAG laser?

Have you ever wondered how bright your laser is? Given that it outputs millions of watts of light (in both 1064 and 532nm) you might imagine that it is quite bright….

Well I took a couple of videos to see for myself. Our laser safety glasses are rated at OD7 – that means if 10 to the power 7 watts (that’s 10 million!) enters the front of the glasses, then only around 1 watt should get through to your eyes.

The videos, one at 1064nm and one at 532nm, were very interesting.

At the 1064nm wavelength, there is a bright flash of light every time the laser is fired on both tattooed and non-tattooed skin; but nothing extraordinary:

1064 tattoo6
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Top photo – 1064nm pulse on a tattoo  :  bottom photo – 1064nm pulse on non-tattooed skin.

However, at 532nm the brightness is enormous (see below)!! The reason why this is so is simply because 532nm is a green wavelength and our eyes are very sensitive at green. But the 1064nm wavelength is in the near infra-red and so is invisible to our eyes. Therefore, no matter how intense it is we will never see it without the use of IR technology.

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Top photo – 532nm pulse on a tattoo – the frame rate of the video camera resulted in the lower part of the arm showing without any laser light;
Bottom photo – another 532nm pulse on the tattoo. 

This photo clearly shows why safety glasses are so important when using Q-switched laser. Their output is so high that even a small percentage of that light can be very damaging to your retina.

Just think, if you laser outputs an energy of 1 joule in a 10 nanosecond pulsewidth, then the average power output is 100 million watts. The skin reflects 4% of all light that falls on it through Fresnel reflections. That equates to 4 million watts!!

If you think how bright a 200 watt bulb look like, then imagine what 4,000,000 watts would be!!!

So, the moral of this story (video!) is – ALWAYS WEAR THE CORRECT LASER SAFETY GLASSES!! 

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You only have one pair of eyes.

Protect them properly!!

If you need any help in making sure your safety eyewear is right for your laser/IPL please email me.


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