On Seeing In The Infrared

Written by Tom Nugent on Tuesday, June 26th, 2007

Our laser operates in the near infrared (IR), which means it is not normally visible to humans (although that doesn’t prevent it from being dangerous to your eyes and skin). “Invisible” lasers are more dangerous precisely because people can get careless around something they can’t see. Luckily, it’s easy to get cameras (video or still) which can convert the IR image to a wavelength humans can see.

Consumer-grade cameras and camcorders, interestingly enough, can see better in the infrared than professional, TV (or photo) cameras. The CCDs or CMOS sensors in cameras are sensitive in the near IR, and higher-quality cameras tend to put filters in the system to remove any unwanted wavelengths, in order to get realistic colors. This makes sense, because the whole purpose of cameras is to reproduce an image for people to see, and if your camera is collecting wavelengths that you can’t see and converting them to something you can, then your image could look “wrong.”

This difference in camera abilities meant that, when the BBC was here in May and they wanted a visual of the laser beam, they had a bit of a problem. Their big professional video camera couldn’t see a thing. But the small camcorder they’d brought showed things just fine. When testing the laser, we always have at least one display showing the target so that we can keep track of any disturbances. It is a great help when working with near IR lasers, because it means we don’t have to spend lots of money on special scopes.

It may not be a perfect rule, but if you want to see in the near-IR, the consumer-grade camera is almost certainly a better choice than the professional-grade one!