We use our eyes to view our world. While our eyes are amazing detectors of light, they only “see” a tiny slice of the whole picture of electromagnetic energy that is all around us – we call what our eyes see “light.”
There is so much more to the electromagnetic spectrum, every thing from gamma rays, x-rays, visible light and on to radio waves. Because we are so used to our own eyes it’s initially weird to think of things like x-rays or radio waves as a kind of light. However, they are really all the same thing – just differing in the amount of energy they carry.
You can think of an infrared (IR) camera (or sometimes called a thermal camera) as a detector of light that is just beyond the range our eyes can see. Anyone remember the Predator movie where the aliens could see in “heat” vision? That’s exactly what I’m talking about here. I think it’s pretty cool that one of the setting on our IR camera is actually called “predator vision” that creates the look from the movie for the false colors.
The night vision goggles the military uses are very similar to IR cameras. They typically are sensitive to wider region of the EM spectrum than an IR camera to make it easier to detect things like people or troops hiding under moon or starlight.
It turns out that everything gives off (emits) varying amounts of heat energy. That includes things you would normally think of as not being “hot” like ice cubes, a human body or even different colors of light.
Way back in 1800, an astronomer by the name of William Herschel wanted to know how much heat was passed through various colored filters he was using. He discovered that filters of different colors passed different amounts of heat. Herschel thought that the colors themselves might be of varying temperatures, so he devised a clever experiment to investigate his hypothesis.
Using a glass prism to create a color spectrum and several thermometers he measured the temperature of the various colors of light coming from the prism. He found that the the temperature of each of the colors of light increased from violet to red. Much to his surprise he found that a thermometer placed just beyond the red color showed the highest temperature of all. This was the infrared light! Read about his experiment and learn how you can do the same experiment in your home or classroom.
The camera that Leah used in this segment of Imagine It creates a false color image. That means that the colors correspond to different temperatures. White being really hot and dark blue very cold. If you wanted to get really technical you can actually bring up a scale on our camera that shows what temperature the colors correspond to as well.
There are quite a few uses for IR cameras including:
There are a couple really nice IR image galleries you should check out to see what various things heat signatures look like. Check out Caltech’s infrared zoo. There are some pretty cool images over there. Also from Caltech and NASA is fun gallery of people’s faces also at the Cool Cosmos site. FLIR, the manufacturer of our camera has some nice images on their press information page that compare visible light images with IR images.
It’s interesting side note to point out that the camera we have is from a manufacturer called FLIR. I never knew what the origin of that name meant until one of our volunteers (a former military guy) at Imagination Station casually said something about the “Forward Looking Infrared Camera”. It turns out that before IR sensor technology developed into the 2D digital-camera-like sensors we have today, IR cameras were typically a one dimensional line of detectors. They relied on a missile or satellite to move or “scan” over an area to create a 2D image. They called these type of IR cameras “push broom” sensors, since you had to rely on a the device to physically move over the object, and you could only image things at right angles to the motion – you could not “Look Forward.”
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