That test involved balancing the laser pointer on a cup, shining it at a CD and photographing the resulting light patterns with two different cameras. But biochemist Jody Plank and physicist Chris Dombrowski of the University of California, Davis say there’s an easier way: Just use an infrared thermometer.

“This is an elegant example of what I hoped would come from our publishing a paper on the green laser problem: that others would find even more accessible and convenient ways to diagnose it,” said National Institute of Standards and Technology physicist Charles Clark, a coauthor of the original study, in an email to Wired.com.

Infrared thermometers measure the heat output of an object without having to touch it. Rather than directly measuring a heated object’s temperature, the thermometers measure how much the object is radiating in the infrared part of the electromagnetic spectrum, and convert that measurement to degrees.

Plank was trying to replicate the setup suggested in the earlier study, “when Chris came in and had this brainstorm” to use the lab’s infrared thermometer instead, Plank said. Infrared thermometers are useful in biology labs like Plank and Dombrowski’s, where sticking a conventional thermometer into an agar plate or a water bath would contaminate biological samples.

When the researchers’ laser pointer was switched off, the thermometer read it as near room temperature. But when they turned it on, the thermometer went nuts, jumping as high as 185 degrees Fahrenheit. Despite the high temperature reading, the laser pointer was still cool to the touch.

“That was the first clue that we were measuring the infrared output of the laser and not an actual temperature,” Planck said.

The pair caution that it’s probably not simple to convert the temperature read by the thermometer to the energy output of the laser, but it is a way to qualitatively check if a laser is leaking a lot of infrared light. The researchers suggest taking several readings to make sure. And as in any home experiment involving lasers, it’s best to wear safety glasses and keep the laser well away from your eyes.

Infrared thermometers are available on Amazon or from a well-stocked hardware store for about $50.

“The NIST method… allows people to set up a small optics physics lab right on their desk,” Plank said. “The method that we came up with might be good for people who are not as inspired by doing their own physics experiment, but still curious about the safety of the laser they’re using.”

Via Bitesize Bio

Image: Anthony Forget

See Also:

• DIY Laser Safety: How to Test Pointers and Save Your Eyes
• Laser Guidance Adds Power to Wind Turbines
• ‘Horrendously Intense’ Laser Shrinks the Proton
• Making Rain Clouds With Lasers

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Authors: Lisa Grossman

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