Last Updated Aug 24, 2010 11:51 PM EDT
Wired recently published an article that explains not just the danger from today's cheap laser pointers (to save money, it has become common practice to omit a shield that blocks potentially hazardous infrared light), but also how to test your laser pointer to see if it is affected.
In a nutshell, you'll want to shine your laser through a slit in a piece of paper at an ordinary CD, which will reflect back to the paper.
Then, all you need to do is observe the diffraction pattern on the paper with a webcam or digital camera to see if there's any infrared light shooting back. If so, you might want to toss the laser in the trash, since direct or reflected light can cause instantaneous damage if it hits your eye just right.
Yeah, this is kinda geeky -- it's a simple way to perform the kind of diffraction experiment you might have done in high school physics -- but it's not difficult to do, and it might alert you to a hidden danger in your PowerPoint tool bag. Read the original article for details on how to set up a test for yourself.